JPH0652893B2 - Spread spectrum communication system - Google Patents

Description

The present invention relates to a spread spectrum communication system, and in particular, a spread code generation circuit for generating pseudo noise for despreading is unnecessary on the receiving (demodulating) side. And spread spectrum communication system.

[Technical background]

The recent development of communication technology and diversification of system technology in Japan is remarkable. One of them is multiplex communication represented by optical communication technology. On the other hand, in communication technology using radio waves, multi-channel access (MCA) has become mainstream in order to effectively use the electric waves of the analog modulation method. However, this MCA has the advantage that a specific person cannot occupy the same frequency, but of course, while the number of channels is limited, calls over the number of channels cannot be performed simultaneously. For this reason, it is routinely necessary to wait for a call in a large city, which is frequently used. This is because frequency resources, which are finite resources, are used by simply dividing only the bandwidth, and considering the quality and immediate characteristics of information, it seems that such a technology has reached its limit.

Therefore, research on more efficient communication methods,
Development has been done by many researchers for a long time,
There is one spread spectrum communication system. This spread spectrum communication system (Spread Spectrum: SS) was developed in Europe about 50 years ago, and its basic idea was established in the 1950s. In the 1960s, a pseudo-noise code generation circuit was created with 100 transistors, but the early technology was immature, and the development of active elements and manufacturing technology that compose them was long awaited. In recent years, the development of high-density IC technology and I
Since the price of C has been reduced and it has become possible to create a small-sized and low-priced device, such a communication system has been receiving attention again.

A spread spectrum communication system is a system in which a carrier is first-order-modulated with an information signal and then spread by a broadband noise-like spread code.
This is a method of performing next modulation and spreading to a very wide band. In general, direct diffusion (D
S) system, frequency hopping (FH) system, hybrid system and the like. The system of the present invention relates to the former DS system. Such spread spectrum communication has many features as follows.

The confidentiality is very high.

Strong against external interference, noise, and intentional interference.

Can coexist with conventional systems.

There is no need for a control station or control channel such as an MCA station.

Can be managed by address code.

Since the power density is low in the DS (direct diffusion) method, it seems that there is no radio wave (transmission with weak power is possible).

The number of stations can be increased by allowing a slight decrease in call quality.

It is possible to multiplex in the same frequency band by changing the pseudo noise code signal.

Recognizing the above-mentioned features, the application is now progressing not only in the telecommunications field but also in various fields, and the application to consumer equipment is being started.

[Conventional technology]

The basic principle of spread spectrum communication will be described with reference to FIGS. 8 and 9. FIG. 8 is a basic configuration diagram of a communication device which realizes a conventional spread spectrum communication system by the DS system, and FIG. 9 is a spectrum waveform diagram in each component. As shown in FIG.
The signal (F ₁ ) as shown in FIG. 9 (a) which is primary-modulated by the secondary modulator 31 is spread by the spread code signal (F _SS ; see FIG. 2 (b)) from the spread code generation circuit 39. The signal is secondarily modulated by the modulation circuit 36, amplified, and then output from the antenna A _{1 as} a transmission signal (F _1S ). The type of primary modulation is not particularly limited, and frequency modulation (FM) or PSK Phase Shift Keyi
ng) or the like (which will be described herein as performing modulation by PSK), the secondary modulation (spread modulation) is generally spread modulation by a pseudo noise code (Pseudo Noise: PN code). This PN code needs to be as random noise as possible and has a constant period for the receiver to extract the code.

Next, the configuration and functions of the receiving side will be described. In the B station on the receiving side, the F _1S signal obtained by the predetermined filter and the high frequency amplifier from the antenna A ₂ is _fed to the despreading circuit 4
In step 7, despreading is performed by the spreading code from the spreading code generation circuit 49. The spread code generation circuit 49 is synchronized with the spread code generation circuit 39 of the A station, and the PN code is also equivalent (F _SS ). By the way, the radio waves coming into the antenna A ₂ are not limited to F _1S, but as shown in FIG. 9 (c), radio waves from other SS stations (F _2S , F _3S , ...) Radio wave (F _n ) exists. Therefore, by performing despreading by the despreading circuit 47, the desired radio wave F _1S as shown in FIG. 3D is returned to the spectrum as shown in FIG. 2A and the filter (preferably a narrow band wave filter) 41 Most of the components other than F _1S are removed at (see (e) in the same figure), and the demodulation circuit 43 demodulates and outputs the original information signal. The figure
As can be seen from (e), in the output signal of the filter 41, in addition to F _1S , F _n of the interference wave and part of the SS wave of another station remain. The ratio of this residual power to the power of the target signal is called the DN ratio (signal power to interference power ratio), and in order to obtain a large DN ratio, it is advantageous that the spreading band is as wide as possible. It is in the range of 100 to 1000 times the frequency band of the information signal.

The basic principle of spread spectrum communication has been described above.
Next, a specific operation in each modulation / demodulation will be theoretically explained. In the spread spectrum communication, the spread spectrum signal (t) {F _1S } in FIG. 8 represents the information data as d (t) [+ 1 or
-1], the spreading code _{F SS P (t) [+} 1 or -1, the carrier cos .omega _c t
Then, it is expressed by the following equation.

S (t) = d (t ) P (t) cosω c t ...... (1) ( where, omega _{c =} 2.pi.fc) The spread spectrum signal S (t) in the receiving (or demodulation), spectra incoming A spread code clock signal is generated from the spread signal, and spread code P (t) that is synchronized with the spread code in the spread spectrum signal at the time of transmission (actually with some delay) Is obtained, and multiplication (also called correlation or despreading) is performed on the incoming spread spectrum signal S (t), and d (t) cosω
It is converted into _c t becomes two-phase PSK signal. Furthermore, the carrier cos .omega _c t reproduced Performs synchronous detection by multiplying the, to obtain _{d (t) (cosω c t} ) 2 = d (t) (1 + cos2ω c t) / 2, remove the double component 2 [omega _c t of the carrier frequency in the filter By doing so, the information data d (t) is demodulated.

Here, the bandwidth of the two-phase PSK signal d (t) cosωct (main spectrum lobe) is _BD , and the spreading code P
If the bandwidth of the spread spectrum signal spread by (t) (main lobe of spectrum) is B _p , the process gain G _p in spread spectrum communication is G _p = B _p / B _D ...... (2 ). The process gain G _p is a value of several hundreds to several thousands in a normal design value, and the interference signal, noise, etc. are suppressed according to this value, so that the information data d (t)
On the other hand, the wider the frequency band of the spread spectrum signal, the higher the effect of improvement in interference resistance and noise resistance. That is,
The improvement effect is almost uniquely determined by the process gain G _p .

[Invention or problem to be solved]

In such a spread spectrum communication system, "despreading" is the most important, and it is not easy to generate a spreading code necessary for doing so. At present, the despreading method using an AFC control loop, a delay lock loop, and a multiplier is used. , The despreading method with a synchronous loop using a matched filter and a multiplier is generally used. The despreading by these configurations has a complicated circuit configuration, and there are problems in terms of adjustment and cost, and it is necessary to solve these problems when deploying to consumer equipment. In addition, since a very wide frequency band is required, there is a problem in effective use of the frequency band (or radio wave), and the usable frequency band is actually limited, making it difficult to design as desired. There are drawbacks such as.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the spread spectrum communication system of the present invention is equipped with the following means for communication. That is to say, on the modulation side (10), the addition means for adding the two-phase PSK signal obtained by the multiplication of the first carrier wave and the information signal and the second carrier wave to obtain the addition signal are obtained. The spread signal is spread by the spread code signal to obtain a spread spectrum signal.

In addition, the demodulation side (20) has the first spread signal which is spread modulation of the two-phase PSK signal and the second spread which is spread modulation of the second carrier from the received spread spectrum signal. A separation means for separating and outputting the signal, a means for despreading by multiplying the spread signals separated and output, and two two-phase PSK signals, and only one of the two two-phase PSK signals. And selecting means for selectively outputting.

Note that the frequency interval between the first carrier wave and the second carrier wave is (2
N−1) / {2 (2 ⁿ −1) T ₀ }, so that the spectrum of the second spread signal is present between the sidebands of the first spread signal and communication is performed. There is.

〔Example〕

As described above, the spread spectrum communication system of the present invention modulates the PN code signal used for despreading at the time of modulation, interpolates the frequency between the spectrums of the spread spectrum signal, and sends it, and at the time of demodulation (reception), spread spectrum signal. Signal and modulation P
N code signals are separately detected and despread by multiplication,
The two two-phase PSK signals obtained are separated and detected by a filter and output. As a result, the clock recovery circuit, the spread code generation circuit, the synchronization pull-in circuit and the synchronization holding circuit which are composed of loops, which have been indispensable in the past in despreading, are no longer necessary. An example of a device that can realize the method will be described with reference to the drawings.

FIG. 1 is a block configuration diagram of a first embodiment of a spread spectrum communication apparatus capable of realizing a spread spectrum communication system of the present invention, in which FIG. 1 (A) is a modulator (transmitting side) 10 and FIG. 1 (B). Is a demodulation unit (reception side) 20. In this figure, a part of the configuration of the antenna and the like is omitted.

The modulator 10 includes an arithmetic circuit (adder) 2, a multiplier 4, a spread code generation circuit (PNG) 6 and a BPF (band pass filter) 7 as a first circuit.
Figure (A) Connected as shown. The demodulation unit 2
0 is constituted by connecting two BPFs 12 and 17, a delay circuit (DL) 13, an adder 14, a subtractor 15 and a multiplier 16 as shown in FIG. 1 (B). The delay circuit 13,
The adder 14 and the subtractor 15 form two types of comb-teeth filters 11, and their transmission characteristics are shown in FIGS. 2 (A) and (B).
Are shown as addition characteristics and subtraction characteristics, respectively. Hereinafter, specific functions and operations will be described with reference to the frequency spectrum diagrams of FIGS. 3 and 4.

First, in the case of transmission, in the modulation section 10, the primary modulation signal d (t) cosω _c1 t (here, the two-phase PSK modulation signal is used) from the input terminal In _{1 as} shown in the spectrum (a) of FIG. 3 (A). Is supplied to the arithmetic circuit 2 and is added to the carrier signal cosω _c2 t from the input terminal In ₂ ((B) in FIG. 7A) to obtain d (t) cosω _c1 t + cosω _c2 t, It is supplied to the multiplier 4. On the other hand, the clock signal S _c (t) is input from the input terminal In _3.
Is supplied to the spread code generating circuit 6, and the spread code signal P (t) is generated based on this. As the spreading code, a pseudo noise code is often used, and an M-sequence code is often used among them, so that it may be called a “pseudo noise code”. The spread code P (t) generated by the spread code generation circuit 6 is supplied to the multiplier 4, where the two-phase
The PSK carrier signal is multiplied (spread spectrum) by the added signal d (t) cosω _c1 t + cosω _c2 t, and the spread spectrum signal P (t) {d (t) cosω _c1 t + cosω _c2 t} (hereinafter "S
(Also referred to as “ _M (t)”) (see FIG. 3 (B)), BPF7
At, only the main lobe of the spread spectrum signal is passed and transmitted, and output from the output terminal Out ₁ .

Here, the frequency spectrum of the spread spectrum signal will be described. In the interval between the angular frequencies ω _c1 and ω _c2 in FIG. 7A, the 1-bit time length of the clock signal is T ₀ , the M code is used in the spreading code generating circuit 6, and the M series code generating circuit (see FIG. If a shift register is used (not shown), where n is the number of stages, it is selected to have an interval given by {2 (2 ⁿ −1) T ₀ } ⁻¹ . In the frequency spectrum of the spread spectrum signal shown in FIG. 7B, the frequency spacing between the sidebands + Sa ₁ and + Sa ₂ and the frequency spacing between + Sb ₁ and + Sb ₂ are {(2 ⁿ −1) T ₀ } ^-1 And the sidebands + Sa ₁ to + Sa _n , -Sa ₁ to -Sa _n ,
Sideband + Sb ₁ ~ + Sb _n, the -Sb ₁ ~-Sb _n, are arranged at equal intervals to each alternately. Note that 2 ⁿ -1 is the spread code length.

FIG. 4 shows the frequency band of the spread spectrum signal together with the angular frequencies ω _c1 and ω _{c2 of} both carriers,
The solid line (c) shows the main lobe between (a) and (b) in the figure.

In the method of the present invention, the selection of frequency is an important point,
The spectrum of the second spread signal S ₂ (t) is selected to exist between the sidebands in the frequency spectrum of the first spread signal S ₁ (t) described later. That is, in FIG. 3, the carrier angular frequency ω _{c1 of the} primary modulation (two-phase PSK modulation) signal d (t) cosω _c1 t and the carrier angular frequency ω of the carrier signal cosω _c1 t
The frequency interval with _c2 is represented by 1 / {2 (2 ⁿ −1) T ₀ }. However the invention is not limited thereto, in theory may be a gap determined by (2N-1) / {2 (2 n -1) T 0}. Note that N is a positive integer, and FIG. 3 shows the case where N = 1. By defining the frequency interval in this way, the spectra of the first and second spread signals S ₁ (t) and S ₂ (t), which will be described later, are arranged alternately without overlapping.

Next, the function and operation of the demodulation unit 20 will be described with reference to FIG. The spread spectrum signal S _M (t) (see FIG. 3 (B)) that has entered the input terminal In ₄ has frequency components other than the spread spectrum signal removed by the BPF 12,
It is supplied to the positive input terminals of the delay circuit 13, the adder 14, and the subtractor 15. Moreover, the output of the delay circuit 13 is added to the adder 1
4, and the negative input terminal of the subtractor 15 is used, so that the delay circuit 13, the adder 14 and the subtractor 15
And addition characteristics and subtraction characteristics (Refer to Fig. 2 (A) and (B) respectively)
The comb-teeth filter 11 having the is formed. Now
Assuming that the delay time in the delay circuit 13 is T (= 1 / F), in the case of addition, as shown in FIG. 2 (A), 1 / T, 2
The gain doubles at the frequencies of / T, 3 / T, ..., N / T (N is a natural number), and the output becomes 0 at each intermediate frequency, and a steep dip can be made. In the case of subtraction, conversely, as shown in Fig. 7B, 1 / T, 2 / T, 3 / T,
The gain becomes zero at the frequency of N / T, and the gain becomes double at each intermediate frequency. Therefore, the delay time is set to T = (2 ⁿ −1) T _0, and f _c1 = M / (2 ⁿ −
1) By setting T ₀ = M · 2Δf (M: natural number), if the frequency of the crests or troughs of the comb-shaped filter 11 is matched with the sideband frequency of the spread spectrum signal, P in the spread spectrum signal S _M (t) (t) d (t) cos ω _c1 t and P (t) cos
This makes it possible to detect the separation from ω _c2 t. Therefore,
The output signal of the adder 14 is P (t) d (t) cosω _c1 t (hereinafter sometimes referred to as the first spread signal “S ₁ (t)” for convenience;
(See FIG. 3 (C)), and the output signal of the subtractor 15 is P
(t) cosω _c2 t (hereinafter also referred to as a second spread signal “S ₂ (t)” for convenience; see FIG. 3D). Although a specific separating operation of the comb-teeth filter 11 will be described later, the expression of the delay of the spread spectrum signal S _M (t) by the delay circuit 13 is omitted here for convenience of description.

The first and second spread signals S ₁ (t) and S ₂ (t), which have been separated and detected according to the above-described principle, are supplied to the multiplier 16, where despreading is performed by multiplication and the spread code signal P ( t) becomes DC by multiplication, and demodulation 2-phase PSK signal d (t) equivalent to that at the time of modulation
cos (ω _c1 −ω _c2 ) t and d (t) cos (ω _c1 + ω _c2 ) t ((d) and (e) of FIG. 3 (E), respectively) are obtained. After removing unnecessary frequency components from these output signals by the BPF 17, the two-phase PSK signal d (t) cos (ω _c1 + is output from the output terminal Out _2.
ω _c2 ) t is output. The two-phase PSK signal here has an angular frequency higher by ω _c2 than the two-phase PSK signal on the modulation side, but this is not an essential change. Also, for convenience of explanation,
The minute crosstalk component is omitted.

Here, the separation detection operation of the spread spectrum signal S _M (t) (the operating principle of the comb-shaped filter 11) will be described. First
The spread spectrum signal S _M (tT) output from the delay circuit 13 in the diagram (B) is S _M (tT) = P (tT) {d (tT) cosω _c1 (t−T) + cosω _c1 (tT) } ... (3). Here, as a precondition, the period of P (t) and the delay time T are made equal, and cosω _c1 t is in phase with the period of P (t),
If a continuous wave that repeats at the same level, cos ω _c2 t has a reverse phase at a period of P (t), and a continuous wave that repeats at the same level, S _M (tT) is S _M (tT) = P (t) {d ( tT) cosω _c1 t − cosω _c2 t} (4) Therefore, the addition output S _M (t) + S _M (tT) {= S
₁ (t)} becomes S _M (t) + S _M (tT) = {d (t) + d (tT)} P (t) cosω _c1 t ... (5). On the other hand, the subtraction S _M (t) + S _M (tT)} = S ₂ (t)} is S ₂ (t) = S _M (t) −S _M (tT) = 2P (t) cosω _c2 t + {D (t) -d (tT)} P (t) cosω _c1 t (6) Note that {d (t) -d (tT)} P (t) co in the equation (6)
Although sω _c1 t is a crosstalk component that cannot be separated by the comb-shaped filter 11, it does not pose a problem because it changes to direct current by the despreading operation described later.

Next, the despreading operation will be specifically described according to the configuration of FIG. A demodulated two-phase PSK signal Sp (t) is obtained at the output of the multiplier 16. That is, from the fifth and sixth equations, Sp (t) = S ₁ (t) × S ₂ (t) = P ² (t) {d (t) + d (tT)} {cos (ω _c1 + ω _{c2) t + cos (ω c1} -ω c2) t + P (t) {d 2 (t) -d 2 (tT)} (1 + cos2ω c1) / 2 to become. By the way, since P (t), d (t), and d (tT) are all +1 or -1, the square of these is 1.
Therefore, Sp (t) = {d (t) + d (tT)} cos (ω _c1 −ω _c2 ) t + (d (t) + d (tT)} cos (ω _c1 + ω _c2 ) t ( 7) Note that if the delay time T is sufficiently shorter than the 1-bit time length in the information data d (t), d (tT) is d
It can be approximated as (t). Therefore, demodulation 2-phase PSK signal Sp
(t) is Sp (t) = 2d (t) {cos (ω _c1 −ω _c2 ) t + cos (ω _c1 + ω _c2 ) t} (8), which is reasonable from the actual circuit operation study. The sex was confirmed.

Next, a second embodiment of the device that can realize the communication system of the present invention will be described with reference to the circuit block diagram of FIG. 5 and the frequency spectrum diagram of FIG. FIG. 5 (A) is a block diagram of the modulator, and FIG. 5 (B) is a block diagram of the demodulator. In these figures, the same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

The modulator 30 is the same as the modulator 10 of the first embodiment except that a multiplier is added, but there is no change in the components, but the way of connection is slightly different, and the primary modulated wave and the carrier wave are different. Are separately modulated (spread) by spread code signals and then added and mixed. Further, the demodulation unit 40 includes a carrier recovery circuit 18,
A multiplier 9 and an LPF 19 are further provided, and these are subtracted by the subtractor 1
5 is inserted between the multiplier 5 and the multiplier 16, and
Same as the embodiment. The combination of the modulator and the demodulator is not limited to this, and the modulator 10 and the demodulator 40 may be combined, and conversely, the modulator 30 and the demodulator 20.
You may combine and. Hereinafter, the operations of the modulator 30 and the demodulator 40 having such a configuration will be described with reference to the frequency spectrum diagram of FIG.

First, in the modulation section 30, from the input terminal In ₁ to FIG.
One modulation signal d (t) cosω _c1 t such as the spectrum (A) of (A)
From the input terminal In ₂ to the carrier signal cosω _c2 t (Fig.
(B) is supplied to the multipliers 4 and 5, respectively. On the other hand, the clock signal S _c (t) is supplied to the spread code generation circuit 6 from the input terminal In ₃ , and based on this, the spread code signal P (t) is generated and supplied to the multipliers 4 and 5. We are supplying. As a result, the spread spectrum is performed by multiplication in the multipliers 4 and 5, and the spread spectrum signals P (t) d (t) cosω _c1 t and P (t) cosω are obtained as shown in (C) and (D) of FIG. _c2 t
Respectively, and the two are added by the arithmetic circuit 2 in the next stage to obtain the spread spectrum signal P (t) {d (t) cosω _c1 t + cosω _c1 t}.
(S _M (t)) (see FIG. 6 (E)), only the main lobe of the spread spectrum signal is passed and transmitted by the PBF 7, and output from the output terminal Out ₁ .

Next, the function and operation of the demodulation unit 40 will be described. The spread spectrum signal S _M (t) such as that shown in FIG. 6 (E) that has entered the input terminal In ₄ has the frequency components other than the spread spectrum signal removed by the BPF 12, and the delay circuit 13 and the adder 1
4 and the positive input terminal of the subtracter 15 and the output of the delay circuit 13 to the negative input terminals of the adder 14 and the subtractor 15 (that is, FIGS. 2A and 2B are shown). To the comb-teeth filter 11 having the characteristics of (1) (the frequency of the crests or troughs of the comb-teeth filter 11 is, of course, matched with the sideband frequency of the spread spectrum signal), so that the spread spectrum signal S _M (t ) P (t) d (t) cosω _c1 t and P
(t) cos ω _c2 t is separately detected, and the adder 14 outputs the signal shown in FIG.
(C) Spread spectrum signal P (t) d (t) cosω _c1 t
{= S ₁ (t)} is output, and the subtracter 15 outputs P (t) cosω _c2 t {= S ₂ (t)} as shown in FIG. The spectrum signal S ₂ (t) is supplied to the carrier recovery circuit 18 and the multiplier 9. The carrier wave recovery circuit 18 is, for example, the multipliers 21 and 2.
3; BPF 22, LPF 24, VCO (voltage controlled oscillator) 25 and 1/2 divider 26 are connected as shown in FIG. That is, this is a doubled carrier recovery circuit, in which the subtraction output S ₂ (t) is first squared in the multiplier 21. Since the subtraction output S ₂ (t) is approximately P (t) cosω _c2 t, the binary signal P (t) is converted into a direct current by the square operation,
The carrier wave cos ω _c2 t becomes cos2 ω _c2 t. Next BPF2
After removing unnecessary frequency components at 2, the multiplier (or phase comparator) 23, the LPF (or loop filter) 24,
And a phase-locked loop (PLL
L) 27, and a carrier of double frequency with a constant amplitude is obtained by removing unnecessary noise components in the input signal. This carrier wave is subjected to signal processing in the 1 / 2-minute clock 26, and the reproduced carrier wave cos ω _c2 t is output.

The carrier wave cos ω _c2 t regenerated by the carrier wave regenerating circuit 18 and the spread spectrum signal S ₂ (t) directly supplied from the subtractor 15 are supplied to the multiplier 9 for multiplication and modulation by the above principle. Spreading code P (t) and signal P (t) cos2 equivalent to time
ω _c2 t is obtained. This signal P (t) cos2ω _c2 t
Is removed by the LPF 19, and only the spread code P (t) is LP.
The signal is passed through F19 and supplied to the multiplier 16, where despreading by multiplication with the spread spectrum signal S ₁ (t) from the adder 14 is performed, and the demodulated two-phase PSK signal d (t) cosω _c1 t
(Actually, there is a delay due to transmission, but it is omitted for convenience of explanation.), Unnecessary frequency components are removed by the BPF 17, and then output from the output terminal Out ₂ . Note that the minute crosstalk component is omitted for convenience of explanation.

〔effect〕

Since the spread spectrum communication system of the present invention communicates as described above, it has the following excellent features.

Since the clock recovery circuit, spreading code generation circuit, synchronization pull-in circuit and synchronization holding circuit that are loops, which were indispensable in the conventional method, are no longer required, the circuit configuration can be considerably simplified and the cost can be significantly reduced. Since it can be easily reduced, it has become extremely easy to deploy to consumer equipment.

By eliminating the need for a sync pull-in circuit and a sync hold circuit, it is possible to contribute to stabilizing the operation of the spread spectrum communication system by eliminating the disadvantages such as the time required for pulling in the sync in the conventional system and the problems such as loss of synchronization. .

Demodulation 2-phase PSK if carrier wave recovery circuit is additionally provided
Since the signal has the same angular frequency as the two-phase PSK signal on the modulation side, more accurate communication can be performed.

[Brief description of drawings]

FIGS. 1 (A) and 1 (B) are block configuration diagrams of a modulator and a demodulator, respectively, of a first embodiment of a spread spectrum communication apparatus capable of realizing a spread spectrum communication system of the present invention, and FIGS. (B) is a transmission characteristic diagram of the comb-shaped filter, and FIGS. 3 (A) to (E) and 6 are shown.
FIGS. 4A to 4E are frequency spectrum diagrams for explaining the operation of the respective constituent parts of the first and second embodiments, and FIG. 4 shows the frequency band of the spread spectrum signal as the angular frequency ω _c1 of each carrier. And frequency spectrum diagram with ω _{c2, Fig.5} (A), (B)
Is a block diagram of the modulator and demodulator of the apparatus of the second embodiment capable of realizing the method of the present invention, FIG. 7 is a block diagram showing an example of the configuration of the carrier recovery circuit, and FIG. 8 is a spectrum used conventionally. FIG. 9 is a schematic block diagram showing the basic configuration of the spread communication device, and FIG. 9 is a spectrum waveform diagram in each component of the block diagram shown in FIG. 2 ... Arithmetic circuit, 4, 5, 9, 16, 21, 23 ... Multiplier, 6 ... Spread code generating circuit, 7, 12, 17, 22
...... BPF (band pass filter) 10,30 …… Modulator, 1
1 ... Comb-shaped filter, 13 ... Delay circuit, 14 ... Adder, 15 ... Subtractor, 18 ... Carrier recovery circuit, 2
0,40 ... Demodulator, 24 ... LPF (low pass filter),
25 ... VCO (voltage controlled oscillator), 26 ... 1/2 frequency divider, 27 ... Phase-locked loop, In _{1 to} In _4, input terminal, Out _{1 to} Out _2, output terminal.

Claims (2)

[Claims] 1. An addition means on the modulation side for adding a two-phase PSK signal obtained by multiplication of a first carrier wave and an information signal and a second carrier wave to obtain an addition signal, and the addition means. And a spreading means for spreading the added signal by a spread code signal to obtain a spread spectrum signal.
Separation means for separating and outputting the first spread signal, which is the spread modulation of the phase PSK signal, and the second spread signal, which is the spread modulation of the second carrier, and both spread signals that have been separated and output. Despread by multiplying two two
A means for generating a phase PSK signal and a selection means for selectively outputting only one of the two two-phase PSK signals are provided, and the frequency interval between the first carrier wave and the second carrier wave is (2N-
1) / {2 (2 ⁿ −1) T ₀ } (where N is a positive integer, n is the number of shift register stages in the spread code generating means, and T ₀ is the 1-bit time length of the clock signal) First above
A spread spectrum communication system characterized in that the spectrum of the second spread signal is allowed to exist between the sidebands of the spread signal of 1. 2. The modulation side comprises first spreading means for spreading-modulating a primary modulation signal obtained by modulating an information signal with a first carrier wave with a spreading code signal to obtain a first spreading signal. , Second
The second carrier is spread-modulated using the spread code signal.
Second spreading means for obtaining the spread signal and the adding means for obtaining the added spectrum spread signal by adding the first and second spread signals. 1
Separation means for separating and outputting the spread signal and the second spread signal, and means for synchronously detecting the separated and output second spread signal to obtain a spread code signal equivalent to the spread code signal on the modulation side,
Despreading means for despreading the first spread signal by the obtained spread code signal to obtain the primary modulated signal, and a frequency interval between the first carrier and the second carrier is (2N -
1) / {2 (2 ⁿ −1) T ₀ } (where N is a positive integer, n is the number of shift register stages in the spread code generating means, and T ₀ is a 1-bit time length of the clock signal) A spread spectrum communication system, characterized in that the spectrum of the second spread signal is allowed to exist between the sidebands of the first spread signal to perform communication.