JPH0314328A - Satellite communication system - Google Patents

Abstract

PURPOSE: To improve the efficiency and processing performance of traffic command processing by sub-dividing the band width of a transponder into narrow band channels. CONSTITUTION: An on-board router 10 is serially connected to a constant band width(CB) network 12 arranged on a satellite board and arrowed to be simultaneously driven together with the network 12. The router 10 includes a means for receiving a variable frequency (VBVCF) traffic of prescribed band width and center frequency, a means for dividing the band width of the transponder 10 at least into two sub-bands, a means for channeling at least one sub-band and establishing plural monoblock channels for carrying the VBVCF traffic, an exchange means for converting or mapping a route from an up-ring up to a down-ring in the router 10 and a CB network 12. The band width and center frequency of a monoblock VBVCF channel can be controlled from the external. Consequently the efficiency and processing performance of traffic command processing can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to a novel method and apparatus for reconfiguring or onboard control of interbeam connections based on traffic demands in satellite communication systems, particularly in multibeam satellite communication systems. It is.

6 and 4GHz (c band), 14 and 11 GH
In current commercial satellite communication systems operating in the z (Ku-band) and 20-30 GHz (Ka-band), on-board connections between uplink and downlink beams occur approximately 50-100 times per year. This is done on a transponder channel basis by providing a "fixed" switching circuit that performs the switching reformation.

The exchange scheme used in this system is Frequency Division Multiple Access (FDM).
A) Suitable for carrying continuous traffic. Other satellite communication systems include “dynamic” systems, which have reconfiguration periods of several milliseconds and are suitable for carrying Satellite Switched Time Division Multiple Access (SSTDMA) burst traffic.
``There is an exchange. The exchange of communication paths between multiple uplink beams and downbeam links is typically performed by a switching matrix based on transponder channel criteria.

These onboard switching matrices are precisely configured from input (uplink) to output (downlink) traffic and can be connected to a given input port without changing the exchange structure or the bandwidth of each interconnect path. Change only the output port that is in. This connection is defined as constant bandwidth (Co) in the following description.
instant Bandwidth, "CB") connection, and the associated traffic is referred to as "CB" traffic.

The current CB-FDMA communication scheme uses l: between uplink and downlink co-frequency transponder channels.
It uses only a fixed connection network of 1 and uses mechanical coaxial exchange, which requires no DC power, to maintain its position after actuation. A typical exchange for this application is a "reorderable exchange matrix" construction that uses "beta" elements when building blocks. On the other hand, the current CB
-SSTDMA (Constant Bandwidth Satellite Switched Time Division Multiple Access) satellite communication system uses diodes or field effect transistors with rise and fall times of several nanoseconds.
A connection circuit utilizing a casopr crossbar microwave switch matrix (MSM) consisting of (FET) is used between the uplink and downlink channels. Non-onboard with variable bandwidth
Satellite fitted TIIMA systems are currently known.

If the onboard interbeam connection is represented by a matrix with an IJ- corresponding to the bandwidth of the ink beam connection path, one of the satellite-based shared frequency transponder channels (e.g. 8 beams) at a given instant The CB connectivity function for a group is represented by an 8x8 matrix with only one non-zero element in each column or row. A typical Max IJ is shown below.

Downlink No. Here, BT is the transponder bandwidth for each channel. In the SSTDMA system, the channel structure or the same matrix is represented by IJx [1],
Non-zero matrix elements periodically change their position over time. The entire representation of a satellite ink beam connection has a number of such switching units at least equal to the number of transponder channels.

C'B connections, which work in conjunction with dominating spot beams at high traffic sources, are useful for heavy route traffic with frequent connection changes.
affic ) has been improved to make it more appropriate. Also, thin route traffic
- route traffic), the CB connection is sufficient. For this traffic, the changes in on-port connectivity are minimal as the carriers are separated in space and time.

However, recently, more sophisticated satellite communication systems are being developed in response to traffic orders involving a relatively large number of small-volume users. This satellite communication system achieves high satellite design efficiency through a narrowband ink beam connection path with reconfigurable bandwidth, such as a variable bandwidth, variable frequency (VBVCF) on-board connection. here,
Satellite design efficiency is defined as the ratio of the satellite's saturated capacity to its nominal capacity and represents how efficiently the satellite regeneration sources are utilized, eg, how onboard connectivity and antenna coverage match traffic mandates.

According to the inventive concept, by subdividing the transponder bandwidth into narrower band channels of varying bandwidth and serving different narrow route services with different connectivity requirements within the range of the same transponder, Onboard TWTAS (travelingwave tu
VBVCF connections can be performed without increasing the number of be amplifiers. Recent on-board TWTA linearization techniques and modulation formers make this design concept particularly attractive.

As an example, a service that requires a continuous band of variable width may be directed to subband B of transponder bandwidth B.
The remaining bandwidth BT BX can be channelized for multiplexing of narrowband VBVCF channels suitable for multi-carrier traffic of varying numbers of different carriers.

In this operation, each channel is routed sequentially to a defined downlink beam by the switched network.

Circuits that perform demultiplexing and routing functions are referred to herein as “on-board routers.”
Continuous FDMA traffic with an onboard VBVCF connection that is accomplished in part or in whole by an onboard switching circuitry is referred to herein as a "VBVCF satellite switched FD".
"MA (SSFDMA) traffic".

According to another aspect of the invention, existing CB connections are overridden by performing both CB connections and VBVCF connections on the same space satellite that performs VBVCF connections with an onboard router that performs satellite exchange.

Conventional onboard routers mainly use continuous FD+. 1A} It was proposed around 1980 in connection with RAFIC. For example, U.S. Pat.
Sate-11i Transponder In
Terconnection UtilizingVa
riable Bandpath Filter) discloses a system that lacks on-board switching capability but uses a payload characterized by a reconfigurable beam interconnect using VBVCF filters achieved by serial filter connections. There is.

The VBVCF filter used in this system performs two successive frequency conversions of the signal frequency spectrum over fixed passbands of two equal filters connected in series. Unfortunately, while this technique is useful for other applications (for example, the Ultrasonics Symposium published in 1977
The title "Filter Whis" described on pages 965 to 968 of "asonics Symposium"
Bandwidth Continuous Variable From 5 to 100 MHz (Filter Wit
hBandwidth Continuously V
Ariable From 5 ~100! AHz)
”), band-pass filters connected in series near the upper frequency are added to the transmission amplitude and phase linople, so in reality, the usability performance is marginal for a linear phase (constant delay time) communication channel. In contrast, in the present invention, VBVCF
The demultiplexing function is performed by an interchangeable combination of pass-hand filters connected in parallel and is not subject to spectral interference due to series connected filters.

Onboard FDMA routers proposed in the early 1980's are primarily concerned with 30 GHz and 20 GHz multi-beam satellite systems. At these frequencies, a wide range of frequency spectrum is available for commercial satellite communications (2500 MHz times more frequency reused). Accordingly, conventional rooks have been designed based on wideband channelization schemes that accommodate a large number of single channels that are frequency multiplexed over a wide bandwidth. Reconfiguration is accomplished by partitioning a large number of useful channels to match user commands. For narrowband reconfiguration connections, very large filter hunks and switching matrices are installed in the router. A router with such a structure has the disadvantage of not only complicated hardware but also larger weight and volume, and is not suitable for SSTDMA (SSTDMA).
atellite Switched time Di
Vision! There is a need for the development of other on-board routing methods, such as MultipleAccess.

Newsletter NASA Tech published in June 1983,
G described in. Stevens (G. Ste.
The paper “A Comparison of Frequency Domain Multiple Access (FDM)” by
A) Time Domain Multiple Access (TDMA) Approach Satellite Service for Low Data Rate Earth Station (A Comparison of Freq
uencyDomain Multiple Access
ss (FDMA) and Time [loma
inMultiple Access (TDMA)
Approaches to SatelliteS
service for Low Data Rate
Onboard SSFDM on Earth Station
There is a useful overview of A-Luke technology. The international magazine "Satellite Communicati" was published from April to June 1987.
On) J.
A) Payload Technologies (Non-reg
enerative Satellite Switch
hed FDMA(SSFD!.(A) Payloo
A detailed description of conventional onboard FDMA router designs can be found in ``D Technologies''.
Another prior art is G.E., published in May 1980. Document No.80SDS427 NASA Contract No. NAS-3-21745 (G,
E, Document No.80SDS427 NA
SA Contrsct No. NAS-3-217
45,! Title: Study of Advancing Communications Satellite Systems Based on SS-FDMA
anced Co+r++nunicat+ons S
atell+te Systems Based on
SS-FDMA) “J.D.Kiesling (
J. D. Kiesling); Bulletin published on April 20, 1980, AIAA 8th
Direct Access Satellite Communications Using SS-FD!.IA (DirectA
ccess Satellite Co+n+nuni
cations Llsing SS-FDJ, IA)
” and the title “Customer Prime Service Study 30/20 GHz” as stated in NASA Contract NAS-3-22889 7 Yinal Report No. 0 3 8 0 5 0-011 issued on April 22, 1982. Satellite Systems (Cumstomer PremiseSer
vice Study for 30/20 GHz
Satellite Systems)''.

In view of the problems noted in conventional satellite communication systems with current on-board technology and reconfiguration or transponder channels, it is an object of the present invention to provide a practical routing system with improved efficiency and throughput of traffic command processing. It is in.

Another object of the present invention is to effectively utilize existing on-board CB switching circuitry to improve traffic processing performance.

A particular object of the invention is to reconfigurably divide the transponder bandwidth into at least two variable width sub-bands;
An object of the present invention is to provide a system for further channelizing at least one subband to achieve multiple VBVCF subchannels.

Yet another object of the present invention is to provide a system for routing traffic through a demultiplexer having a linear phase VBVCF channel. This VBVC
The F-channel utilizes a "parallel" configuration and is based on a class of multi-level channelization formats that are preferably implemented by time and frequency multiplexing circuits.

It is a further object of the present invention to provide an onboard router in which subchannels can be programmably routed to a downlink beam and each subchannel can accommodate either burst traffic (SSTDMA) or continuous traffic (SSFDMA).

(Summary of the Invention) The concept of the present invention is that multiple . C by devices such as onboard routers that use transponder channels to couple multibeam communications satellites to the existing CB connection network on board.
This is realized by a method and apparatus for suitably performing a B connection. CB} traffic and VBVCF traffic are transmitted to the satellite in an uplink beam of a predetermined bandwidth and center frequency.

During reception, the bandwidth of each uplink beam is set to bandwidth B.
into T number of transponder channels. V8V
The transponder channel carrying the CF } traffic is further divided into a number of sub-transponder channels by an onboard router. One of these channels is variable burst rate SST.
DMA} Provides a continuous band of variable width that is particularly suitable for traffic.

This method and apparatus can be recognized on the basis of the IJx above, where VBVCF traffic is present in uplink beams 5, 6.7 and 8 and in downlink beams 4, 5.7 and 8. . CB connection mat IJ
Box [2] is shown below.

Downlink beam no. No. Here, the "*" mark represents CB} traffic, and the others represent VBVCF} traffic. Band BT
The connection path * is established by the CB connection network, and the connection path 1]. (i=5.6, 7.8 and j=4.
5, 6.7.8) and route B. + (+=5.
6. 7. 8) is established by the onboard Luke. In matrix [2], the bandwidth Li
is a portion of the transponder's bandwidth By, and the bandwidth B
Is 1 left? It is part of the bandwidth BA.

Σ”Bz<BT ottJ ””'[3:]V
This is done by reconfiguring the BVCF or changing the value of the bandwidth "Xj+e.".

A preferred method of implementing CB} traffic with existing onboard CB circuitry is by connecting a device such as an onboard router to the CB network. The preferred embodiment includes dividing the transponder's bandwidth into two parts and further channelizing the l parts to establish each bandwidth and center frequency of a single VBVCF traffic channel, and the VBVCF traffic. to the downlink beam through the CB network and control the center frequency and bandwidth (eg, Li and B+j) of this VBVCF channel.

According to the device of the invention, the on-board router is connected in series to the CB network installed on the board of the satellite and operates simultaneously with this CB network. The router includes means for receiving VBVCF traffic of a predetermined bandwidth and center frequency, means for dividing the transponder bandwidth into at least two subbands, and means for further channelizing the at least one subband into VBVCF traffic.
} means for establishing a plurality of simple channels for carrying traffic; and switching means for translating or mapping the path from the uplink to the downlink in the router and CB network. The bandwidth and center frequency of a single VBVCF channel can be controlled externally.

The system of the present invention adapts the CB} traffic and the VBVCF traffic such that the CB traffic has a constant bandwidth connection through reconfiguration and the VBVCF l-rough ink has a variable bandwidth connection.

The object, concept and structure of the invention will become clear to those skilled in the art from the description of the embodiments taken in conjunction with the accompanying drawings.

(Preferred Embodiment) Referring to FIG. IA and FIG. ) is combined with the CB connection network 12 to achieve the CB connection. Rook 10 and CB network l2 are located on the board of the communication satellite and form reconfigurable interconnection paths between uplink and downlink beams based on typical frequency plans ll and 13, respectively. do. These paths can carry digital traffic from data communication systems requiring varying digitized telephone voice signals and/or data transmission rates and volumes of analog FM traffic. Furthermore, these routes can be compatible with either FDMA or TDMA according to the present invention. As mentioned above, CB is called constant bandwidth transponder trough, so VBVCF is variable band width variable center frequency subtransponder traffic (Variable Band Transponder Traffic).
wi6thVaEiable Center Freq
uency Sub-transponder tra
ffic). The width of the box within the broncs of frequency plans 11 and 13 generally indicates the bandwidth of traffic requests along a particular route. The solid and dashed lines correspond to CB traffic and VBvCF } traffic, respectively. For example, the first four blocks of uplink frequency plan l1 represent CB traffic that occupies the entire transponder bandwidth B7, and the rear four block slots of frequency plan 11 represent each of the four channels 5-8. VBVCF indicates the bandwidth of trough ink requests at .

The uplink frequency plan 11 shows possible transponder channelizations based on the connectivity matrix [2] defined in the previous description. By transponder frequency plan, this plan means dividing the transponder frequency band into l sets of sub-hands corresponding to different traffic paths.

In each block of plan 1l, the two numbers in each set are the numbers for the uplink beam and the downlink beam (destination beam) as shown at the respective inputs and outputs of the rook 10 and CB network 12 in FIG. Each represents an identification. Similarly, the downlink plan 13 indicates the characteristics of the downlink channel and the path sequence translated by the uplink and downlink beam numbers.

More than one pair of numbers in the same box means that extra bandwidth is used for multiple interconnect paths. A pair of numbers in parentheses is called SSTDMA } traffic, and a pair of numbers without parentheses is called FDMA } traffic.

According to the present invention, frequency branch l3 shows a typical satellite-converted ink beam connection and conversion for CB} traffic and VBVCF traffic. Uplink beams 1-4 handle CB traffic routed through CB connection network I2, and amplifier link beams 5-8 handle VBVCF routed through connection network I2 and router 10. l-Process traffic.

The rook lO is connected in series with a fixed connection network l2 and operates simultaneously with this connection circuit. The router 10 also splits the VBVCF traffic and routes the VBVCF traffic to the appropriate downlink beam.

In the drawing, router 10 shows a VBVCF connected in parallel to a multi-stage channel riser (MSC) as defined in connection with FIG.
It has a filter. This MSC includes the SSTDMA controller 14 and the HissFDl. lA controller 16
connected to a coupler crossbar switching network controlled by The exchange of columns in the exchange matrix is performed using SSTDM.
A controller 14 or SSFDMA controller 16
can be achieved based on either a periodic time pattern representation of SSTDMA applications (burst traffic) or a reconfiguration or time plan representation of SSFDMA applications (continuous traffic). Displayed in router 10 and SSTDM
The exchange points controlled by the A controller 14 are illustrated with open circles, and the S S F D M A controller 16
The exchange points controlled by are shown as filled circles. The structure of this exchange matrix exists for a given time instant. At another time instant, exchange controllers 14 and 16 may perform another exchange configuration.

Figure 1B shows uplink beam no. 5 shows the bandwidth versus time of a hypothetical channelization plan related to traffic originating from 5; The numerical set in FIG. IB representing the amplifier link/downlink path corresponds to the numerical set shown in FIG. IA. Subchannel division also corresponds in the same way. Time t=
In Q, the path [:5
5]. Bandwidth BM via (57], [:58)
S is used first, with traffic occurring on beam 5 and transmitted simultaneously on down beams 5, 7, and 8. time t
=t'', the operating mode changes to SSTDMA mode with frame period T1.

In each frame T1, the information of subchannel B8, is time multiplexed via each path [55), [57) and [58]. At time 1=1, Luke's reconfiguration occurs and S S T D ! ．． + A mode route (
:55], (57:] and [58] is compressed to B'XS, and at the same time, the frame period changes from T, to T2, and the multiplexed period is extended. Bandwidth Width < Bxs B'xs) to extend the bandwidth of the interconnect path [54] that performs SSFDMA} rough ink.

Another reconfiguration occurs at time 1=12. In this case, no change in bandwidth occurs, but SSTDM with frame period T3
The A-mode paths [55] and [57] change into consecutive SSFDMA mode paths [57] with the same bandwidth.

CB traffic exchange does not occur within the router IO. CB traffic is exchanged only by the fixed connection network 12, and vBvCF traffic is exchanged independently by the router IO. Therefore, the exchange of CB traffic and VBVCF traffic may use different techniques based on the different requirements of the two traffic types.

The router IO includes a switching matrix and control means for independently routing each incoming traffic link through the network 12 to the conventional downlink beam. Router 10 also includes a filter bank that channels a portion of the transponder channel in a controllable bandwidth and center frequency, thereby forming a narrowband path for a single channel of VBVCF I-RAF. Preferably, these filter banks have bandpass characteristics with high skirt selectivity. This skirt selectivity is dB
/MHz and is defined as the ratio of 39 dB to the transition bandwidth of 1 to 40 dB, ie, the difference between the 40 dB bandwidth and the 1 dB bandwidth divided by two.

FIG. 2 shows the input stage of router 10 and illustrates a typical frequency division of one of the eight transponder channels. One of these channels will be described and substituted for the remaining transponder channels. Figure 2 shows N-
An Ideal Transponder Upritter Frequency Plan 20 for a Group of Shared Frequency Transponders in a Beam Satellite Communication System, a Typical Frequency Plan 30 Performed by the Onboard Router 10, and Band Splitting Used to Accomplish the Objectives of the Invention Scheme 60 is shown.

A typical satellite communication system includes several transponder groups that relay traffic information from a beam. In the frequency views 20 and 30, each traffic channel is ideally represented as a trapezoid whose upper and lower sides define a useful (for example 1 dB) range and a 40 dB bandwidth. The distance between the upper sides of two adjacent trapezoids is explained below? protection band B. It is called.

The center frequency of the transponder is ftc” (ri, +f
．． )/2, where fT+ and fA2 are the lower end frequency and the upper end frequency, each defining a 1 dB attenuation point. As an example, single carrier variable bit rate traffic in uplink plan 20 is fTI~F
occupies a useful bandwidth of ax 22, and multicarrier traffic occupies a bandwidth of fX~fT2 at BX.

In this example, multi-carrier traffic is allocated to two connection paths 23 and 24;
4 contains traffic destined to the same downlink beam.

The frequency plan 30 of the onboard router consists of two fixed adjacent passbands 3l and 32, and the useful bands of these bands are such that the passband 3l is between f1 and r. 2+. :
: Pass band 32 ha fas = (fu2+Bc)~f
It extends to pi. These passbands 31 and 32 do not necessarily have to be adjacent, but are preferably configured so that the entire bandwidth of the transponder channel is utilized efficiently. The shaded areas of passbands 31 and 32 are No. 2} Raffic 22. 23 and 24, respectively. Passband 3l is allocated to single carrier traffic and is provided by a fixed bandpass filter with very high skirt selectivity to achieve high spectral utilization. The transition band width 33 of 1 dB to 40 dB at the upper end frequency fR2 is the pass band 3.
Guard band B6 associated with the Mth channelization level of 2
shall be equal to Under these conditions, adjacent channel interference between single-carrier and multi-carrier traffic is suppressed to more than 39 dB. The center frequency of the passband 32 is L+c=(fQ:
++fR4)/2. This center frequency will be referred to as the "router center frequency" in the following discussion, and its selection is primarily explained by the technique used to install the router's filter.

Another requirement that satisfies the typical plan in Figure 2 is "e.

Use fi+=fi− fia=Bt. BT is f
R. −fR, represents the largest value required for 0
≦8. <; Adapt any value of Ba. In practice, the minimum loading factor for single carrier traffic is LF
If +ath =l00Bx'-+1,/By, the above inequality becomes as follows.

B. '． i. ,=(LP.,no, )/100
<ox <8. (4) and r. ．． -r
,3=B. -BXZaih (5) As an example, LFall1 =! If it is 5o%, BX'
、． ,,=8. /2 and rR2-r. ,-e. r
(6) fu- f,3=L/2 {6}' The passband 32 is reused M times by the M filter banks of the rook 10. M filter banks are connected in parallel to avoid the additional distortion typical in series connected filters. Each filter bank is multi-stage “parallel”
Configure the "stage" of the channelizer to satisfy the channelization "level" of the multi-level channelization plan.Essentially,
Each filter bank divides the bandwidth 32 into a number of simple VBVCs.
Channelize to F channel. At each stage, the single channels have different center frequencies and can have the same or different useful bandwidths, transition bandwidths, and guard bands.

As an example, the N1 passband filters of the first channelizer stage have a bandwidth Bi, a guard band BCI and a
One can have the same nominal value for the transition bandwidth Ft in dB, and the hardware complexity can be minimized. The channelization level with a minimum number of N1 single channels is referred to as the lowest level. The channelization level with the maximum number of NM single channels is called the highest level.

If two adjacent channels separated by two passband filters have the same insertion loss at their end frequency and the guard band between them is 8, then in a given channel the lower The maximum adjacent channel interference caused by adjacent channels with side center frequencies ACT. ．． A (i.e., the minimum C/I value when C is the desired signal power and I is the interference signal power) is
equals the incremental adjacent channel insertion loss associated with the increase in the guard band B, of the upper edge frequency. Adjacent channel?
If Act. has a higher center frequency, then Act. ．． ．． is equal to the incremental adjacent channel insertion loss associated with the reduction of guard band B6 at the lower edge frequency.

In the present invention, a preferred channelization plan satisfies the following properties: Frequency multiplexing of single channels selected from different channelization levels generates a νBVCF channel sequence, resulting in a
I) ■ or will be smaller than a certain value, or (C/l)-i- between any two channels will be larger than a certain value. The formulas for these characteristics are expressed as follows.

(1) Useful (i.e., 1 dB) to be channelized
) bandwidth is an integer number N. of single channels of bandwidth Bx. and the integer (N.-1) of the safety band Bcx. That is, BT −Nm U3s + (Nl1 1)B
cm - (7) (2> Based on the router frequency plan 30 in Fig. 2, F."BG. binding, ni (
integer) = NM /IC, and the first level channel is the Mth level η. The following requirements are required to satisfy the condition that it can be replaced with 1 channel.

Bl +2Ft −jl, M)1 +(n+
1) Bax+2Bc14. ．． -(8)(8>
The formula can be rewritten more generally as:

8, =nt Bx +α(n+-1)Bci+
(9) F+ = Bc, x [1+α+n
+(1-α) ) / 2 (10) using parameters and system requirements selected in the range 0≦α≦1 based on available means (e.g., frequency spectrum and filter techniques). Spectral diagram 6 in Figure 2
0 is n. 12 shows some of the channelization formats. When α=l, the transition bandwidth is minimized, resulting in a more useful bandwidth for retaining information.

(3> The (C/l)l value between any two adjacent channels at the first level is the minimum value (C/l).i
.

In order to satisfy the condition that the value becomes larger, the following formula is required.

Bc+=2Ft-Bcg-BcH(α+n+(1-α)
) (14)(7)2~Channelization formats in which the factor α satisfies equations (11) and have different values are as follows:
Channel shape factor (SF, = 1 + 2F+/Bt
), spectrum utilization efficiency (η+ =100 N+
8+/at ) and adjacent channel interference (C/T) i . For example, since the channelization format 30 (“brickwall” format) in FIG. 2 gives the maximum value η1 and satisfies the condition α=1, the following equation can be derived from equations (10) and (11). It will be destroyed.

B. =F, 1F, =8. ．． (12) N. -12, the brickwall channelization format has five possible levels as shown in Table (13) below.

Table 13 There is a risk of For this, other channelization formats are conceivable, for example formats with smaller values of the factor α. In general, when 0 and α≦1, B/8.4=0.25, that is, SF, I=1.
It was set as 5.

In FIG. 2, the channelization levels shown correspond to the levels i=2.4 and 5 above. From Table (13), it is clear that as the single channel bandwidth B1 increases (e.g. as the lower channelization level increases), SF+ decreases and η1 increases under the condition of α-1. A reduction in SF+ very close to 1 (an ideal rectangular box filter) poses significant technical problems in the practical realization of such a filter at the lower channel level; (l3) shows SFI = 1.291 (for comparison, SF, = 1.069 for α = l). Unfortunately, the higher the form factor, the lower the spectrum utilization efficiency. The best solution is SF, , η1 and AC
+, is derived from the exchange of requirements.

The input stage 40 of the router will be explained based on FIG. Router input stage 40 includes an input downconverter 41 , a parallelization circuit 46 , and a channelizer 55 that develops subchannels for passband 32 . The parallelization circuit 46 has one input port and two output ports, and these output ports are coupled in parallel to a bandpass filter 50 having a transmission characteristic of the passband 31. The down converter 41 is a normal circuit that converts a predetermined frequency band from a predetermined center frequency to a lower center frequency, and is a normal circuit known in the art, such as a frequency mixer connected to a filter. It can be constructed.

The parallelization circuit parallelizes two bandpass filter circuits such as the bandpass filter 50 and the channelizer 55 having the minimum insertion loss between the input port and the output port, and this parallelization circuit It can be constructed in various ways depending on how the Luke filter is constructed by conventional means. For example, the parallel circuit may consist of two series connected support circuits with one port terminating in a matched load when the filter operates at microwave frequencies.

Alternatively, if the filter operates at surface acoustic wave (SAW) frequencies, it may be constructed with a constant-K ladder network. For example, ■ “IE” published in November 1976.
IEEE Transactions
actions) Volume SU-23, No. 6. 3rd
It is described on pages 86 to 393. 'Properties of Constant K Ladder SAW Contiguous Filter Bank
s of a Constant-K Ladder
SAW Contiguous Filter Ba
Please refer to nk).

Channelizer 55 includes a 1:M power divider 51;
This power divider divides the incoming power in the passband 32 into M
filter banks 52. It is divided into M parallel paths including 53 and 54. If necessary, any power splitting loss 10 1 oM (dB) can be partially or totally compensated for by a linear amplifier. The router input terminal 40 also includes a sum frequency source 45, which is the local oscillator frequency f,. +ex is generated. 1
．． -1. - Te, fto=ftcf++c, Teari, B
x varies between zero and 81 in discrete steps of width B'M -(ON +B, ). Preferably, a crystal oscillator with an n-divided counter is used to achieve frequency stabilization. It should be noted that other types of stabilization sources can of course be used.

Minimum loading factor LP. ．． , if we consider B. is period B
Xr*l. <[lX Varies in the range of IT. The input traffic signal is supplied to the port 43 of the down converter 41 and at the same time the frequency f L O + B゜×
A local oscillator signal (where B'x = Dx + Bc) is provided to the downconverter via port 42. The down converter 41 has fX+ (fto+B'x
) Convert the frequency Ll to fR2 according to the relational expression = fi2. The result is that all of the single carrier traffic is kept within passband 31 and all of the multiplex traffic is kept within passband 32. Pass band 32
The traffic within emerges from port 47 of parallelization circuit 46. The output 47 of the parallelization circuit 46 is connected to the input 48 of a 1:M power divider 5l, from which the M filter bank 52. 53. 54 with the incoming signal. Filter bank 52 satisfies the lowest channelization level and produces N outputs 56 with a bandwidth of 8l. Filter bank 53 satisfies the next higher channelization level and produces N2 simple channels 57 of bandwidth B2. The last filter bank 54 satisfies the highest channelization level M and bandwidth B. N, one single channel 58 is generated. Output 56. 57 and 58 are applied to the input ports of the switching network of router 10, which will be described below in connection with FIG. Note that although three stages have been described to satisfy M channelization levels, the present invention is not limited to three stages.

FIG. 3 is a schematic block diagram showing the structure of switching network 90. The switching network 90 includes a bandpass filter 50 (
2) and a channel riser 55 (FIG. 2) with M outputs 56, 57. 58 (Figure 2). In operation, circuitry 90 (1) determines which single channel to select from which channelization level; (11) converts the selected channel to FDM technology (
(iii) multiplexing by frequency division multiplexing);
Routing the channels formed in (ii) towards the desired downlink is performed. Channelization format 30 (FIG. 2) and a general channelization format that satisfies equations (7) through (1l) allow switching network 90 to perform the two functions shown in FIG. 4: (a) sequentially; (b) connecting one input signal among multiple input signals with overlapping bands to a single output port at a time instant of . Connect to the output ports at the same time. Switch network 90 performs each of these functions. Preferably, this is implemented using two multi-port switched networks. In the following description, these switching networks will be referred to as switching networks 60 and 80.

Switching network 60 (FIG. 3) connects channelizer output 51 . 52. 53 and 5
Single polar multi-throw (SPmT
Here, m=2.3, 4, , M) switches 62 to 7
It is implemented by a linear array consisting of 0. switch 6
2 to 70 control the control unit 10 in the usual manner by a microprocessor or mechanical means on board the satellite.
3 or can be activated and controlled automatically in response to command signals from the ground or by other means known in the art.

The switching network 80 has (N, t-+-t) rows 81,
82. 83, 84, 85, 86. 87 and Nx columns 871, 872, 873. Here, NX
is the number of downlink beams. exchange matrix 8
0 individual exchange matrix intersections can provide both broadcast (with l inputs to many outputs) and report (with many inputs to one output) modes of operation. can. these are,
It may be of the type shown in the insert of FIG. 3 with a SPIT switch 93, a crossbar 94 and two directional couplers 95 and 96. This configuration is the traditional technology used in many on-board microwave switching units. For example, June 1982
The magazine “IEEI I11MTT Symposium” (1 Kano Miichi MTT Symposium) was published in April.
p. p.). tlo (
``Coupler Crossbar Microwave Switch Matrix (C
ouplcr Crossbar Microwave
Each crossbar switch matrix row has two control units.
(CU) SSTDMA controller 101 or SSFDMA
Any one of the controllers 102 may control the control unit 102, the control unit being a fast periodic reconfiguration (SS
Signals can be provided for TDM^) or aperiodic reconfiguration (SSFDMA). exchange matrix 80
Nx 1 output 91 of SP. T switch array 6
0 to nodes 71, 72, and 73, or from channelizer 55 (FIG. 2) to node 74 and from passband filter 50 of FIG. 2 to interconnect 75.

FIG. 4 shows as an example the principle of connection of channelizers.

According to FIG. 4, the switching network of FIG. It is understood that multiple input signals with non-overlapping bands can be connected simultaneously to a single output port. Fourth
The figure shows N,=3:N2=4, N3=6 and N.
．． 4-12 shows the channelization format of N4-12. The bands illustrated in the same diagram have the same SP. Switched by T-switches, this fourth band is for traffic connected directly to crossbar switching matrix 80 of FIG. 3 at input port 74. Same SP.
The division of the band into groups switched by T-switches is done on the basis of the minimum number of switches.

However, it is understood that other criteria may also be applied, for example by minimizing the number of throws of each switch.

From the example in FIG. 4, according to the above criteria, a switching network having 3 SP4T switches, 1 SP3T switch, and 2 SP2T switches is obtained, and 6 filters are obtained from the 12 filters serving as the fourth channelizer. is clearly connected directly to the exchange matrix. More generally, applying the criterion of minimizing the number of switches results in the following configuration, evident in FIG. The input to switching network 90 from the Mth filter bank is divided into two groups of single channels 54 and 55. N.M.
- A group of one channel is SP. T switch array 60 and the remaining N. ~N. -, channels extend directly to several input ports 74 of the crossbar switching matrix 80. SP shown in FIG. The structure of the T-switch array 60 is as follows.

Table 15 From Table 15, NX-1 is SP. Determine the overall number of T switches, M and N, control the complexity and number of the largest SPMT switches. The size of the crossbar exchange matrix is determined by Ni1 and N1.

FIG. 5A shows a mechanism for identifying and labeling all possible VBVCF channel sequences generated by a given channelizer. For illustration purposes, N+
= 2, N2= 4. A channelization format with L=N3216 was chosen.

FIG. 5B shows a channelization sequence selected to be performed by way of example.

FIG. 5C is a circuit diagram of a switching network of the type shown in FIG. 3 with switching settings suitable for generating the channelization scheme shown in FIG. 5B.

In FIG. 5A, labeling of sequences is performed using a framework diagram superimposed on the channelization plan of the channelizer. A binary representation suitable for implementation by digital control signals is employed. The control signal is sent to unit 101. in FIG. 102 and 103 are generated by the control unit. In Figure 5A, each possible V
BVCF channel sequences are identified by paths in the framework diagram, represented by dashed lines (branches) and dotted nodes. Each block. The launch is related to the bottom channel, with each bullet indicating an option to choose between channels at different levels. The VBVCF channel sequence starts at node 161 and includes either a first level wideband channel (branch 00), a second level intermediate band channel (branch 01), or an Mth (third) level (branch 11) narrowband channel. Therefore, V
BVCF channel sequence 165. 166 and 16
There are three groups of 7. Moving along the right side of the branch in the framework diagram, we reach node 162. 163 and 1
64 appears. At these node points, a selection is made of which single channels are to be included in the desired VBVCF channel sequence. Each framework path intersects the channelization frequency plan from left to right and is characterized by a 6-bit word. Each word also represents a VBvCF channel sequence associated with a unique framework path.

For example, the channel sequence 70 of FIG.
Characterized by the word l74="011110" for the framework path represented by the thicker dashed line in the figure.

FIG. 5C shows how the above words are used to control an SP to T switch array in a switching network of the type shown in FIG. Signals from the first, second and third channelization levels 180, 182 and 184 are routed to SP. The T-switch array 80 is supplied with the T-switch array 80 . SP. The T-switch array is connected to nodes 161. 162
．． 4 switches 188 corresponding to 163 and 164
, 190, 192 and 194. SP3
The T switch corresponds to the three selection nodes in the framework diagram, and the S
A P2T switch corresponds to two selection nodes.

SP. The structure of the T-switch array consists of a 6-bit control signal (CBI, 2, 3,
4, 5.6). Switch 188, 1
The states 90, 192 and 194 are defined by the first two bits, the third bit, the fourth bit, the fifth bit and the sixth bit, respectively. A control signal is supplied from a controller 140. The setting of the switch in FIG. 5C is identified by two black dots on the switch rotary arm and is based on the word "011110." The four outputs of the switch array are symbols ▲, 口, ●, △
gives the four channels of sequence 70 illustrated by .

Sequences 70 all belonging to the third channelization level
The other channels are coupled directly to the crossbar exchange matrix. These channels are designated by letter D (
Channels marked with crossbars in FIG.

Once a configured VBVCF sequence of single channels is obtained, it is necessary to route another block channel to another downbeam. for example,
In FIG. 5B, at a certain time instant the channel sequence 70 consists of three predetermined blocks 71 . 72 and 73.

The task of simultaneously connecting non-overlapping frequency multiplexed channels to output ports is accomplished by the coupler crossbar matrix of FIG. 5C.

The replacement point shall be of the type shown in Figure 3. The black dots with circles indicate exchange points, and the requirement 71 for determining the route in Figure 5B.
．． Provide the correct connections to match 72 and 73. The switching controls for switching matrix 90 are of the conventional type and consist of 5-bit words supplied to the columns of this matrix. Regarding the addresses of 16 exchange points 4
bits, and use 1 bit for a fixed bit.

In FIG. 5C, three words are applied by control unit 140 to convert this relanowart into CCB7. 8.
9, 10. 11), [CB12, 13,
14, 15. 16:] and [(:B 17, 1
8, 19. 20, 21]. Note that in this example, switching control is not specified for either SSTDM^ or SSFDMA. In the most general case, this preferred embodiment uses three separate controllers S S T D ! J^Controller, SSFDMA
: ] 7 } o-5 and sp. 'r Control unit 1 executed by switch array controller
40 is used.

FIG. 6 is a detailed block diagram of a preferred onboard router based on the concepts of the present invention. 1~N,I(N.<N
> input beam constitutes the VBVC'F traffic. A single beam, for example beam no. 1, the incoming traffic occupies a bandwidth By of the center frequency fTC shown in FIG. When switch 116 (which can also be externally controlled like other switches in the CB network) couples the input to downconverter 111, the traffic signal is transferred to downconverter 111.
1, the frequency is converted using the local oscillator frequency flo+B' generated by the combined signal source 114 described above.

Bypass switch 115 connects signal source 114 to downconverter 111 or operates with BX''O.

Bypass switch 116 bypasses incoming traffic to router processing and provides incoming traffic directly to CB connection network 12 (FIG. 1A).

The output signal from the downconverter 111 is provided via a connecting transmission line 118 to the parallelization circuit 112 described above in connection with the parallelization circuit 46 of FIG. The parallelization circuit 112 divides the traffic into two signal streams 121 and 12.
These signal streams are passed through a hand-pass filter 113.
and proceeds to the channelizer 123. These bandpass filters and channelizers include a channel riser 55 (fifth
3A) and 3A are connected to the switching circuit 125 as described above. Unit l20 is a channelizer (CHAN), a parallelization circuit (PAR),
Bandpass filter (BPF) and switched network (SN)
Contains.

Switch network 125 includes two large units. Unipolar multiple throw (S) provides “variable bandwidth” functionality.
PMT) array 126 and a crossbar switching matrix (CBSM) that performs the “variable center frequency” function and routes traffic to the downlink beams.
) 127. N from each of the units 120
Multiplexer 130 outputs 128 outputs from X
multiplexed into NX traffic channels at .

Traffic failures at the outputs 134, 135 and 136 of the multiplexer are connected to the output ports 14 of the router.
It is up-converted in an amplifier converter 141 before being sent to the amplifier converter 141. Other units} 120 and other components of this unit operate similarly.

Specific embodiments of the invention have been illustrated and described in detail. Various modifications and improvements are possible to those skilled in the art. For example, the used bandwidths and frequencies are used for convenience of explanation and are not limited to the values and ranges described above. Bandwidths and operating frequencies may vary in form and specification without departing from the scope taught herein. Other frequency plans may be used and the frequency plans shown and described are not limited to those shown. Control of all sinches may be achieved by various means including processing units, relays, or by condition responsive means. Filter linking can be done by various means besides filter banks. For example, digital filtering may be utilized by substituting appropriate components compatible with the technology, such as digital filters based on the teachings of the present invention.

Up-conversion and down-conversion can be performed by various means as well as frequency mixing using a combined signal source.

[Brief explanation of the drawing]

FIG. IA is a block diagram illustrating the configuration and uplink and downlink frequency plans of a preferred onboard router of the present invention to which a typical satellite CB connection network is coupled; FIG. IB is a block diagram illustrating the uplink and downlink frequency plans; 2 is a conceptual diagram showing the time characteristics of the bandwidth structure of the channel routing achieved by the onboard rook in FIG. 1A. FIG.
- an uplink frequency plan relating to a group of shared frequency transponders in beam satellite communications 20, CB
FIG. 3 is a diagram illustrating, respectively, a channelization plan 30 accomplished by an on-port router that routes through the connecting network, and a preferred band division scheme 60 necessary to implement the principles of the present invention. FIG. 4 is a block diagram showing the preferred switching circuitry and cross-spar switching circuitry incorporated in the on-board router of FIG. IA; FIG. 4 is a diagram showing the basic design concept of the switching circuitry contemplated by the present invention; 5C are diagrams showing actual examples of channel allocation and switching control in FIG. IA, and FIG. 6 is a block diagram showing the structure of a preferred onboard rook according to the present invention. 1-8...Uplink beam and downlink beam 10...Router 11, 13. 20. 30...Frequency plan 1
2... Connection circuit network 14... SSTDMA controller 16... SSFDMA controller 40... Input stage 46... Parallelization circuit 50
. . . Bandpass filter 5l . . . Power divider 52. 53. 54... Filter bank 55...
Channelizer 60...Band division scheme 80.
90... Switching circuit network 140... Control Uninote★
Sheet 7-D FIG. Old 'm FIG. 5A FIG. 4 ← Tsukasa'・tchu K. al; counter number FIG. 5B

Claims (1)

[Scope of Claims] 1. A variable band variable center frequency multi-beam satellite communication system including multiple transponder channels interconnecting a plurality of incoming and outgoing communication paths, comprising: A. at least one fixed band. C. receiving means for receiving an incoming transponder channel of a width of 100 nm; , multi-stage channelization means connected to the band division means for receiving a second portion of the at least one transponder channel and dividing the second channel portion into multiple levels of subchannels of variable bandwidth; , one of many input signals with overlapping bands
switching means for connecting a plurality of input signals to an output port of the transponder in sequential time periods and simultaneously connecting a plurality of input signals with non-overlapping bands to the output port of the transponder. Satellite communication method. 2. The satellite communication system according to claim 1, further comprising means for changing relative bandwidths of the first and second portions. 3. The band dividing means includes distribution means for distributing a minimum power loss to the signal between the first part and the second part;
3. The satellite communication system according to claim 2, further comprising bandpass filter means for passing the second portion, and power division means for dividing the signal power of the second portion. 4. The satellite communication system according to claim 3, wherein the distribution means includes amplifier means for amplifying the power of the first and second portion signals. 5. The satellite communication system of claim 2, wherein the channelizing means comprises a plurality of selectable filter banks with high skirt selectivity. 6. The filter vanter comprises a plurality of groups of constant bandwidth filters to form multi-level channelization in parallel configuration and reduce additional losses and distortions in series configuration. Satellite communication method described in. 7. The satellite communication system according to claim 6, wherein the filter banks of the adjacent subchannels have asymmetric transmission amplitude characteristics at their ends. 8. The satellite communication system according to claim 1, wherein the receiving means includes frequency conversion means for converting the frequency of the at least one transponder channel. 9. The satellite communication system according to claim 8, wherein the center frequency of the frequency conversion means matches the center frequency of the at least one transponder channel. 10. Satellite communications according to claim 9, wherein the frequency conversion means comprises a local oscillator including means for generating a plurality of frequencies to tune the at least one transponder channel to a plurality of center frequencies. method. 11. E. further comprising SSTDMA control means connected to the switching means for time division multiplexing the information carried by the first and second portions of the variable band. satellite communication method. 12, E, connected to said exchange means, said at least one
frequency division multiplexing of the information carried by the first and second parts of the transponder channels.
The satellite communication system according to claim 1, further comprising SFDMA control means. 13, E, a first
SSTDMA means for time-division multiplexing information carried by a second part of the at least one transponder channel and a second part of variable bandwidth; SSFDM that accesses information by frequency division multiplexing
Claim 1 further comprising A control means.
Satellite communication method described in. 14. In a satellite communication method including multiple transponder channels interconnecting a plurality of incoming and outgoing communication paths, when performing multi-beam communication with variable bandwidth and variable center frequency, the bandwidth of the at least one transponder channel is dividing the width into a first portion having a first center frequency and a second portion having a second center frequency, and dividing the second portion of the transponder channel into successive levels of selectable bandwidth subchannels. one input path of the plurality of input paths with overlapping bands is connected to an output port of the transponder in sequential time periods based on a traffic command; A satellite communication method characterized in that a plurality of input paths that are not connected to each other are simultaneously connected to an output port of a transponder. 15. The satellite communication method according to claim 14, wherein the connecting step is controlled by frequency division multiplexed access to each input path and output path of the at least one transponder channel. 16. The method of claim 14, wherein the connecting step is controlled by time division multiplexed access to each input path and output path of the at least one transponder channel. 17. Controlling the step of connecting each input path and output path of the at least one transponder channel by frequency division or time division multiplexed access based on a traffic command.
4. The satellite communication method described in 4. 18. The satellite communication method according to claim 14, wherein the controlling step includes the step of time division multiplexing access and frequency division multiplexing access of each input path and output path. 19. The step of dividing comprises the step of frequency converting the bandwidth of the at least one transponder into first and second frequency bands defining the first and second portions. Satellite communication method according to item 14. 20. The dividing step includes a frequency conversion step of converting the bandwidth of the at least one transponder into first and second frequency bands defining the first and second portions. The satellite communication method according to claim 15. 21, where M is an integer, the channeling step is
15. A satellite communication method as claimed in claim 14, including power dividing the second portion into M stages each having n equal narrowband levels.