CN103338048B - Reception method and unit of radio frequency front end of cognitive spectrum sensing receiver - Google Patents
Reception method and unit of radio frequency front end of cognitive spectrum sensing receiver Download PDFInfo
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Abstract
The invention discloses a reception method and a unit of a radio frequency front end of a cognitive spectrum sensing receiver. In the whole frequency band of DVB-T, every xMHz is configured to be a sub-frequency band unit. Through twice frequency mixings, a reception signal is converted to a first high intermediate frequency through up conversion, and then is converted to a second intermediate frequency terminal through down conversion, and thus the whole sub-frequency band spectrum is moved to the neighboring of the intermediate frequency of xMHz. Frequency sweep is conducted on the frequency band through an electrically tuned filer which is in a yMHz bandwidth, and slides in a certain range as the center frequency varies with the change of the voltage. As such, signals in the yMHz bandwidth and are covered in the DVB-T full frequency band range can be received. The reception method and the unit of the radio frequency front end of the cognitive spectrum sensing receiver is characterized by DVB-T full frequency band coverage, relatively small mirror image interference, simple circuit design, simple intelligent operation and easy realization.
Description
Technical field
The invention belongs to communication technical field, be specifically related to a kind of radio-frequency front-end method of reseptance based on the cognitive frequency spectrum perception receiver of ground digital television broadcast (DVB-T) frequency range and unit.
Background technology
Radio spectrum resources is a kind of extremely limited resource, needs by national correlation department to specify relevant regulations unified management and the frequency spectrum resource in certain band limits is licensed to specific purposes to use.Along with the development of wireless communication technology, people are to the variation day by day of wireless traffic kind demand, and frequency spectrum resource will be more and more poorer.In order to alleviate the problem of frequency spectrum resource shortage, the common practice that the management that can realize current frequency spectrum resource by improving the availability of frequency spectrum adopts in the world carries out to authorize and unlicensed frequencies administrative mechanism.For mandate frequency range, unauthorized person must not arbitrarily use.In these mandate frequency ranges of having distributed and unauthorized frequency range, there is the disequilibrium that this frequency spectrum resource utilizes.Namely authorize the frequency range availability of frequency spectrum very low at some, and user is a lot of in some unauthorized frequency range, traffic carrying capacity is crowded, and radio frequency band is tending towards saturated substantially.
In order to address this problem, if people start to consider the frequency spectrum resource of temporary transient vacancy to be used, namely allow the user of with no authorized license when not producing any interference to authorized user, use the licensed band of having distributed, the pressure of frequency spectrum resource will be improved greatly.The raising availability of frequency spectrum that is applied as of cognitive radio provides a kind of good solution.Its core concept is exactly that when authorized user is in non-use authority frequency range, cognitive user just can use this frequency range to communicate when not producing interference to authorized user.
Ground digital television broadcast (DVB-T) is a pith of people's amusement and recreation.Often people watch digital broadcast television and just take a part of frequency range wherein, for other frequency ranges, are be in idle condition.If the temporary unappropriated frequency range of this part can be fully utilized, the availability of frequency spectrum will be improved greatly.
In October, 2004, IEEE formally sets up IEEE802.22 working group, this is first worldwide tissue of the air-interface standardization based on cognitive radio technology, it works in the TV channel in VHF/UHF frequency range (extended frequency range 47MHz ~ 910MHz) frequency range of 54Mhz ~ 862MHz, and it automatically can detect the idle resource of frequency range and be used.
A key technology of cognitive radio is frequency spectrum perception technology.How detecting whether primary user's signal exists on this section of frequency spectrum quickly and accurately, is the key issue of frequency spectrum perception.The core concept of cognitive radio frequency spectrum perception receiver carries out detection to judge that whether its frequency range is idle to different frequency ranges, and this just needs to have multiband, reconfigurable cognitive radio Versatile RF front-end hardware platform.
There is the organization plan of many radio-frequency transmitters about multiband at present.Such as notification number is that the Chinese invention patent of CN101867381 " utilizes narrow-band local oscillation and switch filtering to realize the method for down conversion of radio frequency spectrometer " and notification number is " tracking filter for TV tuner " of CN101938613, they adopt radio-frequency input signals is divided into several wave band carries out down-conversion, utilize switch filtering to realize the frequency-selecting of different-waveband signal.This utilize multiple band pass filter to realize frequency-selecting and frequency tuning structure and be not suitable as the radio-frequency (RF) front-end circuit of the cognitive frequency spectrum detection receiver of DVB-T, reason is that the band bandwidth of DVB-T is wider, if the frequency sub-band selected has lacked, the probability of the idle frequency spectrum that can detect can be affected.And select more frequency sub-band, then divide several frequency sub-band just to need several filter, cause circuit very complicated.Notification number is that the Chinese invention patent " a kind of multi-frequency band radio-frequency receiver " of CN101908896 adopts radiofrequency signal to be down-converted to required intermediate frequency through twice mixing to export in addition, frequency synthesizer is except giving the first frequency mixer and providing local oscillation signal, also by a frequency divider, provide local oscillation signal to the second mixing.But because be controlled by a frequency divider, and frequency divider can not be very accurate, so more difficult realization is for the covering of DVB-T full frequency band, if secondly frequency sub-band divide more time, it will be very complicated for controlling frequency divider.Application number be 201210047420.6 Chinese invention patent " short-wave spectrum sensing method and system " in have employed tuned filter, refinement shortwave frequency range.And step-by-step system frequency sweep achieves a butt joint the perception of to collect mail number in refinement shortwave frequency range, and shortwave frequency range covers comprehensively.But because tuned filter is for frequency-adjustable scope and limited bandwidth, so be difficult to realize realizing full frequency band frequency sweep in DVB-T frequency range.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of radio-frequency front-end method of reseptance and unit of cognitive frequency spectrum perception receiver, and it has the covering of DVB-T full frequency band, Image interference impact is less, circuit design is simple, intelligent operation is simple and the feature easily realized.
Provided by the invention based on DVB-T cognitive radio frequency spectrum detection receiver radio frequency front end, its basic ideas exactly the whole frequency range of DVB-T are set to a frequency sub-band unit with every xMHz, if it is CH1, CH2, CH3 ... CHn.Each frequency sub-band correspond to an one-level local frequency.By secondary mixing, acknowledge(ment) signal is first upconverted to the first high intermediate frequency, then is down-converted to the second intermediate frequency end, thus whole frequency sub-band frequency spectrum shift to bandwidth be xMHz intermediate frequency near.Again by a yMHz bandwidth, the electrically tunable filter that centre frequency is slided within the specific limits along with the change of voltage, and frequency sweep is carried out to this frequency range.So just can realize receiving with the yMHz of DVB-T full frequency band scope covering the signal being bandwidth.In the entire system, PC control first vibration frequency and electrically tunable filter centre frequency, and the second local frequency is fixing.Be easy to just can draw the range of signal that receiver radio frequency front end is current received.
For solving the problem, the present invention is achieved by the following scheme:
A radio-frequency front-end method of reseptance for cognitive frequency spectrum perception receiver comprises the steps:
(1) low pass filter receives the signal of DVB-T frequency range, the signal beyond filtering frequency range;
(2) signal of reception carries out amplifying and restraint speckle power by low noise amplifier;
(3) DVB-T band limits is divided into n frequency sub-band, i.e. CH1, CH2, CH3 ... CHn, wherein each frequency sub-band is xMHz;
(4) under the control of host computer, first vibration generator is that each frequency sub-band correspondence produces an one-level local frequency;
(5) first frequency mixers, under one-level local frequency, carry out up-conversion the sub-band signals that will receive, frequency sub-band frequency spectrum shift on the high intermediate-frequency band of a fixing xMHz bandwidth;
(6) signal after up-conversion is suppressed Image interference through the high intermediate-frequency filter that a bandwidth is xMHz, and through high intermediate frequency amplifier, power amplification is carried out to it;
(7) second local oscillator generators produce a fixing secondary local frequency;
(8) second frequency mixers are under this secondary local frequency, and the signal after being amplified high intermediate frequency amplifier carries out mixing, by the second mixing, whole frequency sub-band frequency spectrum shift to bandwidth be xMHz intermediate-frequency band on;
(9) signal after mixing is sent into automatic gain controller and carry out automatic growth control;
(10) signal after automatic growth control is sent into tuned filter network; This tuned filter network comprises and rises impedance matching line transformer group, electrically tunable filter, tuning filtering amplifier, falls impedance matching line transformer group; Wherein
(10.1) rise after the signal after automatic growth control is carried out rising impedance matching by impedance matching line transformer group and send into electrically tunable filter;
(10.2) Digital DC Voltage-stabilized Power Source is under the control of host computer, realizes tuning filtering function by the voltage changing electrically tunable filter;
(10.3) electrically tunable filter carries out the frequency sweep that centre frequency is yMHz bandwidth in certain scope, and electrically tunable filter carries out filtering to rising the signal after impedance matching;
(10.4) tuning filtering amplifier amplifies filtered signal;
(10.5) fall impedance matching line transformer group and impedance matching is fallen to the signal after amplification;
(11) host computer carries out data processing to the one-level local frequency data of the frequency that first vibration generator produces and the centre frequency data of electrically tunable filter, the frequency range that the radio-frequency front-end that acquisition bandwidth is yMHz receives, and show on host computer, wherein
The frequency that radio-frequency front-end receives=one-level local frequency-secondary local frequency+electrically tunable filter centre frequency;
(12) baseband processing unit that the frequency band signals received by radio-frequency front-end sends into receiver carries out the whether idle detection of frequency spectrum.
In said method, the shunt-resonant circuit of what described electrically tunable filter adopted is wire-wound inductor and capister, Digital DC Voltage-stabilized Power Source realizes tuning filtering function by the voltage changing capister under the control of host computer.
In said method, the scope of described DVB-T frequency range is between 50 ~ 878MHz.
In said method, the bandwidth of described each frequency sub-band and the span of x are between 8MHz ~ 16MHz.
In said method, described electrically tunable filter in centre frequency between 10MHz ~ 30MHz.
In said method, the bandwidth of described electrically tunable filter and the span of y are between 1MHz ~ 4MHz.
A radio frequency front-end unit for cognitive frequency spectrum perception receiver, forms primarily of low pass filter, low noise amplifier, first vibration generator, the first frequency mixer, high intermediate-frequency filter, high intermediate frequency amplifier, the second local oscillator generator, the second frequency mixer, automatic gain controller, tuned filter network, the first single-chip microcomputer, second singlechip and host computer.Wherein tuned filter network comprises and rises impedance matching line transformer group, electrically tunable filter, tuning filtering amplifier, falls impedance matching line transformer group and Digital DC Voltage-stabilized Power Source.The input of low pass filter is connected with reception antenna.The output of low pass filter sends into one of them input of the first frequency mixer after low noise amplifier, host computer connects the data input pin of first vibration generator through the first single-chip microcomputer, and the output of first vibration generator is connected with another input of the first frequency mixer.The output of the first frequency mixer accesses one of them input of the second frequency mixer successively after high intermediate-frequency filter and high intermediate frequency amplifier, and the output of the second local oscillator generator connects another input of the second frequency mixer.The output of the second frequency mixer sends into the input rising impedance matching line transformer group of tuned filter network through automatic gain controller.The output rising impedance matching line transformer group connects the input of electrically tunable filter, the output of electrically tunable filter connects the input falling impedance matching line transformer group through tuning filtering amplifier, the output falling impedance matching line transformer group connects baseband processing unit.Host computer connects the data input pin of Digital DC Voltage-stabilized Power Source through second singlechip, and the output of the voltage of Digital DC Voltage-stabilized Power Source is connected with the voltage of electrically tunable filter.
In said units, the shunt-resonant circuit of what described electrically tunable filter adopted is wire-wound inductor and capister.
Compared with prior art, tool of the present invention has the following advantages:
1, this radio-frequency (RF) front-end circuit is specially adapted for the structure of DVB-T frequency spectrum perception receiver, refinement DVB-T frequency range, and in refinement frequency range, carry out the step-by-step system frequency sweep function of yMHZ bandwidth, thus achieve a butt joint collect mail number perception, and can realize DVB-T full frequency band cover.
2, have employed the double conversion scheme of the first up-conversion, and use a fixed-frequency filter and a tuned filter, and the frequency band of two filters is all custom-made design, whole system can be made to have good selectivity and pass-band performance, reach better mirror image inhibition, distortion effect is less.
3, provide the local oscillation signal of the first upper side frequency by PC control, the local frequency that output is accurately wanted can be facilitated.
What the numerical-control direct-current source of stable pressure 4, controlling electrically tunable filter adopted is single-chip microcomputer is core, and it carrys out alternative traditional digital regulation resistance by PC control and controls, thus the filtering frequency range of more simple and convenient, accurate control tuned filter.
Although 5, this radio-frequency (RF) front-end circuit also needs to carry out double conversion, because the high intermediate frequency after first time mixing is fixing, so second time mixing is also fixing, do not need in circuit to change; Thus whole radio-frequency (RF) front-end circuit system needs the local oscillation signal being just to provide the first mixing and the electrically tunable filter of control, these two pieces can be carried out in real time controlling and demonstrating the frequency range received by host computer intuitively, make whole circuit very simple; Controlled by these two parts, can know that the frequency range of which part carries out the detection of frequency spectrum very intuitively, the cognitive radios work after convenient.
Accompanying drawing explanation
Fig. 1 is Circuits System schematic diagram of the present invention.
Fig. 2 is passage block diagram of the present invention.
Fig. 3 is system flow chart of the present invention.
Fig. 4 is electrically tunable filter block diagram of the present invention.
Embodiment
A kind of radio frequency front-end unit of cognitive frequency spectrum perception receiver, as shown in Figure 1, form primarily of low pass filter, low noise amplifier, first vibration generator, the first frequency mixer, high intermediate-frequency filter, high intermediate frequency amplifier, the second local oscillator generator, the second frequency mixer, automatic gain controller, tuned filter network, the first single-chip microcomputer, second singlechip and host computer.Wherein tuned filter network comprises and rises impedance matching line transformer group, electrically tunable filter, tuning filtering amplifier, falls impedance matching line transformer group and Digital DC Voltage-stabilized Power Source.The input of low pass filter is connected with reception antenna.The output of low pass filter sends into one of them input of the first frequency mixer after low noise amplifier, host computer is connected by the input of serial ports with the first single-chip microcomputer, the output of the first single-chip microcomputer connects the data input pin of first vibration generator, and the output of first vibration generator is connected with another input of the first frequency mixer.The output of the first frequency mixer accesses one of them input of the second frequency mixer successively after high intermediate-frequency filter and high intermediate frequency amplifier, and the output of the second local oscillator generator connects another input of the second frequency mixer.The output of the second frequency mixer sends into the input rising impedance matching line transformer group of tuned filter network through automatic gain controller.The output rising impedance matching line transformer group connects the input of electrically tunable filter, the output of electrically tunable filter connects the input falling impedance matching line transformer group through tuning filtering amplifier, the output falling impedance matching line transformer group connects baseband processing unit.Host computer is connected with the input of second singlechip by serial ports, and the output of second singlechip connects the data input pin of Digital DC Voltage-stabilized Power Source, and the output of the voltage of Digital DC Voltage-stabilized Power Source is connected with the voltage of electrically tunable filter.
Host computer adopts VB language compilation, and the inside comprises three parts, is respectively one-level local oscillator control section, electrically tunable filter control section, receiver reception frequency range display section.
For first vibration generator, what its first phase-locked loop adopted is ADF4350 chip, and being characterized in inner integrated first voltage-controlled oscillator (VCO), can reference frequency output be 137.5MHZ to 4400MHZ.Be suitable as very much this radio-frequency front-end local oscillator part.Its inside includes 8 registers, just can produce corresponding local frequency by the value arranging these 8 registers.What these 8 registers adopted is serial date transfer, can control with single-chip microcomputer.Just data can be inputted to phase-locked loop by control single chip computer by host computer.According to each frequency sub-band CHn, host computer correspond to a local frequency respectively.When needing, only need input the frequency sub-band value wanted, press corresponding button, just its frequency sub-band that correspond to can be moved in low-frequency range.
For tuned filter network, it mainly comprises two line transformer net mates, electrically tunable filter, a tuning filtering amplifier divide and a Digital DC Voltage-stabilized Power Source.The shunt-resonant circuit of what above-mentioned electrically tunable filter adopted is wire-wound inductor and capister, see Fig. 4.Tuned filter network is the emphasis of receiver rf front-end, and its performance quality, directly determines detection probability and the sensitivity of frequency spectrum perception system.The narrow bandwidth electrically tunable filter directly realizing yMHZ bandwidth due to low frequency that will to realize in bandwidth be xMHz requires very high to the Q value of resonant circuit.If when input and output impedance and load are all 50 ohm, the decay of filter can be very slow, and pass band is very wide, and the Q value of resonant tank is not high, thus does not reach the requirement of narrow-band filtering.Input and output impedance and load is increased so can adopt.Wherein, rising impedance matching line transformer group with what fall that impedance matching line transformer group adopts is line transformer chip TC4-1W and ADT16-1T of Mini-Circuits company, realizes 50 ohm to the impedance transformation of 3.2K ohm reach the object of raising electrically tunable filter resonant tank quality factor q value by two-stage cascade.After impedance matching network, it is carry out the slip of yMHZ bandwidth in the low frequency of xMHz that electrically tunable filter just can be implemented in bandwidth by the voltage controlling variable capacitance diode two ends.And just can realize controlling electrically tunable filter by a Digital DC Voltage-stabilized Power Source.Digital DC Voltage-stabilized Power Source also controls single-chip microcomputer with host computer here, and the voltage exported by controlling Digital DC Voltage-stabilized Power Source just can control electrically tunable filter centre frequency.
The radio-frequency front-end method of reseptance of the cognitive frequency spectrum perception receiver that above-mentioned radio frequency front-end unit realizes, as shown in Figure 2, is characterized in that comprising the steps:
(1) signal of DVB-T frequency range is received by the low pass filter of radio frequency front-end unit, the signal beyond filtering frequency range.
(2) signal of reception carries out amplifying and restraint speckle power by the low noise amplifier of radio frequency front-end unit.
(3) every for DVB-T band limits 50 ~ 878MHz x MHz is set to a frequency sub-band, is divided into as n frequency sub-band, i.e. CH1, CH2, CH3 ... CHn, each frequency sub-band corresponds to a local frequency, and the first local oscillator part is controlled by host computer.By the first frequency mixer of radio frequency front-end unit, want the frequency sub-band frequency spectrum received to carry out up-conversion, frequency sub-band frequency spectrum shift on the high intermediate-frequency band of a fixing xMHz bandwidth.
(4) signal after up-conversion is suppressed Image interference through the high intermediate-frequency filter that a bandwidth is xMHz, and through high intermediate frequency amplifier, power amplification is carried out to it.In the present embodiment, the bandwidth of described each frequency sub-band and the span of x are between 8MHz ~ 16MHz.
(5) frequency produced through radio frequency front-end unit second frequency mixer and secondary local oscillator again carries out lower mixing.This secondary local frequency is fixed.
(6) the automatic growth control module signal after mixing being sent into radio frequency front-end unit carries out automatic growth control.
(7) signal after automatic growth control is sent into tuned filter network.This tuned filter network comprises one for what rise impedance matching and rises impedance matching line transformer group, an electrically tunable filter, a tuning filtering amplifier, and one formed for the impedance matching line transformer group of falling of falling impedance matching.The bandwidth of electrically tunable filter is yMHz, and it can change voltage thus realize centre frequency slides between certain limit.Be that the Digital DC Voltage-stabilized Power Source of the host computer of core controls electrically tunable filter by single-chip microcomputer, can allow and make to carry out the frequency sweep that centre frequency is yMHz bandwidth in the scope that bandwidth is the intermediate frequency of xMHz.In the present embodiment, the shunt-resonant circuit of what described electrically tunable filter adopted is wire-wound inductor and capister, Digital DC Voltage-stabilized Power Source realizes tuning filtering function by the voltage changing capister under the control of host computer.Electrically tunable filter in centre frequency between 10MHz ~ 30MHz.The bandwidth of described electrically tunable filter and the span of y are between 1MHz ~ 4MHz.
(8) the host computer data controlling first vibration frequency, the host computer transfer of data controlling electrically tunable filter centre frequency carry out data processing, according to formula to PC end: radio-frequency front-end receive frequency=first vibration frequency-secondary local frequency+electrically tunable filter centre frequency.Just can draw the frequency range that the radio-frequency front-end that bandwidth is yMHz receives.
(9) host computer correspondingly can control first vibration frequency and electrically tunable filter centre frequency, and demonstrates its corresponding frequency range received.
(10) signal received is sent into baseband processing module and carry out the whether idle detection of frequency spectrum.
By step (7) (8), just can show that in the frequency range received by receiver, whether frequency spectrum is idle.Operation before repeating again afterwards, just can carry out frequency sweep to whole DVB-T frequency range.
As shown in Figure 3, in a preferred embodiment of the invention, we are set to a frequency sub-band unit DVB-T with every 8Mhz.Analyze for CH1 frequency range, will carry out frequency spectrum detection to CH1 frequency sub-band (50 ~ 58MHz), the frequency spectrum analyzing its which part is in the free time.Radiofrequency signal is first through low pass filter and low noise amplifier, and the first local oscillation signal produced with phase-locked loop in the first frequency mixer carries out first time up-conversion.Wherein, the local frequency that frequency sub-band CH1 is corresponding is 968MHz.Here in host computer, only need input the frequency sub-band value wanted, press corresponding button, local oscillator will produce the local frequency corresponding to frequency sub-band.By up-conversion, whole CH1 frequency range frequency spectrum shift to 910 ~ 918MHz.Be 915MHz by the signal after frequency conversion through a centre frequency, bandwidth is that the intermediate-frequency filter of 8MHz suppresses Image interference, and carries out power amplification through an intermediate frequency amplifier to it.The 938MHz frequency produced through radio frequency front-end unit second frequency mixer and secondary local oscillator again carries out mixing, downconverts to 20 ~ 28MHz place.The automatic growth control module that signal after secondary mixing sends into radio frequency front-end unit is carried out automatic growth control.Finally by tuned filter network, wherein electrically tunable filter module is bandwidth is 1MHz, and centre frequency is slided between 20 ~ 28MHz along with change in voltage.Pressing its corresponding button by host computer namely can control centre's frequency.First press corresponding to the button of centre frequency at 21MHz here, such electrically tunable filter index is bandwidth 1MHz, centre frequency 21Mhz.Pass through formulae discovery, the frequency range that current radio frequency front end receiver receives can be known: radio-frequency front-end receive frequency=first vibration frequency-secondary local frequency (938)+electrically tunable filter centre frequency, wherein first vibration frequency is 968MHz, and electrically tunable filter centre frequency is 21MHz; Bring in formula and be then: radio-frequency front-end receive frequency=968-938+21=51MHz; So the frequency that current radio frequency front end receives is bandwidth 1MHz, centre frequency is the signal of 51MHz scope.This formula also can be run automatically in host computer inside, and result is presented on host computer.The baseband processing module of the signal feeding rear class received is carried out the detection of frequency spectrum free time.If idle condition, just this section of frequency spectrum can be utilized.If be in busy state, then, repeat step above, press electrically tunable filter module host computer and correspond to the button of 22MHz, just can obtain the frequency that radio-frequency front-end accepts is bandwidth 1MHz, and centre frequency is the signal of 52MHz scope.Send into again and follow-uply carry out Base-Band Processing.The detection of frequency spectrum free time so just can be carried out to CH1 frequency sub-band (50 ~ 58MHz).Same, if want the detection other frequency sub-band being carried out to the frequency spectrum free time, as long as press the button relative to this frequency sub-band at the first local oscillator host computer, then the operation before repeating.
Claims (8)
1. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver, is characterized in that comprising the steps:
(1) low pass filter receives the signal of DVB-T frequency range, the signal beyond filtering frequency range;
(2) signal of reception carries out amplifying and restraint speckle power by low noise amplifier;
(3) DVB-T band limits is divided into n frequency sub-band, i.e. CH1, CH2, CH3 ... CHn, wherein each frequency sub-band is xMHz;
(4) under the control of host computer, first vibration generator is that each frequency sub-band correspondence produces an one-level local frequency;
(5) first frequency mixers, under one-level local frequency, carry out up-conversion the sub-band signals that will receive, frequency sub-band frequency spectrum shift on the high intermediate-frequency band of a fixing xMHz bandwidth;
(6) signal after up-conversion is suppressed Image interference through the high intermediate-frequency filter that a bandwidth is xMHz, and through high intermediate frequency amplifier, power amplification is carried out to it;
(7) second local oscillator generators produce a fixing secondary local frequency;
(8) second frequency mixers are under this secondary local frequency, and the signal after being amplified high intermediate frequency amplifier carries out mixing, by the second mixing, whole frequency sub-band frequency spectrum shift to bandwidth be xMHz intermediate-frequency band on;
(9) signal after the second frequency mixer mixing is sent into automatic gain controller and carry out automatic growth control;
(10) signal after automatic growth control is sent into tuned filter network; This tuned filter network comprises and rises impedance matching line transformer group, electrically tunable filter, tuning filtering amplifier, falls impedance matching line transformer group; Wherein
(10.1) rise after the signal after automatic growth control is carried out rising impedance matching by impedance matching line transformer group and send into electrically tunable filter;
(10.2) Digital DC Voltage-stabilized Power Source is under the control of host computer, realizes tuning filtering function by the voltage changing electrically tunable filter;
(10.3) electrically tunable filter carries out the frequency sweep that centre frequency is yMHz bandwidth in its tuning range, and electrically tunable filter carries out filtering to rising the signal after impedance matching;
(10.4) tuning filtering amplifier amplifies filtered signal;
(10.5) fall impedance matching line transformer group and impedance matching is fallen to the signal after amplification;
(11) host computer carries out data processing to the one-level local frequency data of the frequency that first vibration generator produces and the centre frequency data of electrically tunable filter, the frequency range that the radio-frequency front-end that acquisition bandwidth is yMHz receives, and show on host computer, wherein
The frequency that radio-frequency front-end receives=one-level local frequency-secondary local frequency+electrically tunable filter centre frequency;
(12) baseband processing unit that the frequency band signals received by radio-frequency front-end sends into receiver carries out the whether idle detection of frequency spectrum.
2. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver according to claim 1, is characterized in that:
The shunt-resonant circuit of what described electrically tunable filter adopted is wire-wound inductor and capister, Digital DC Voltage-stabilized Power Source realizes tuning filtering function by the voltage changing capister under the control of host computer.
3. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver according to claim 1, is characterized in that:
The scope of described DVB-T frequency range is between 50 ~ 878MHz.
4. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver according to claim 1, is characterized in that:
The bandwidth of described each frequency sub-band and the span of x are between 8MHz ~ 16MHz.
5. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver according to claim 1, is characterized in that:
Described electrically tunable filter in centre frequency between 10MHz ~ 30MHz.
6. the radio-frequency front-end method of reseptance of cognitive frequency spectrum perception receiver according to claim 1, is characterized in that:
The bandwidth of described electrically tunable filter and the span of y are between 1MHz ~ 4MHz.
7. the radio frequency front-end unit of cognitive frequency spectrum perception receiver, it is characterized in that, form primarily of low pass filter, low noise amplifier, first vibration generator, the first frequency mixer, high intermediate-frequency filter, high intermediate frequency amplifier, the second local oscillator generator, the second frequency mixer, automatic gain controller, tuned filter network, the first single-chip microcomputer, second singlechip and host computer; Wherein tuned filter network comprises and rises impedance matching line transformer group, electrically tunable filter, tuning filtering amplifier, falls impedance matching line transformer group and Digital DC Voltage-stabilized Power Source; The input of low pass filter is connected with reception antenna; The output of low pass filter sends into one of them input of the first frequency mixer after low noise amplifier, host computer connects the data input pin of first vibration generator through the first single-chip microcomputer, and the output of first vibration generator is connected with another input of the first frequency mixer; The output of the first frequency mixer accesses one of them input of the second frequency mixer successively after high intermediate-frequency filter and high intermediate frequency amplifier, and the output of the second local oscillator generator connects another input of the second frequency mixer; The output of the second frequency mixer sends into the input rising impedance matching line transformer group of tuned filter network through automatic gain controller; The output rising impedance matching line transformer group connects the input of electrically tunable filter, the output of electrically tunable filter connects the input falling impedance matching line transformer group through tuning filtering amplifier, the output falling impedance matching line transformer group connects baseband processing unit; Host computer connects the data input pin of Digital DC Voltage-stabilized Power Source through second singlechip, and the output of the voltage of Digital DC Voltage-stabilized Power Source is connected with the voltage of electrically tunable filter.
8. the radio frequency front-end unit of cognitive frequency spectrum perception receiver according to claim 7, is characterized in that,
The shunt-resonant circuit of what described electrically tunable filter adopted is wire-wound inductor and capister.
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| CN103532643B (en) * | 2013-10-09 | 2015-06-03 | 桂林电子科技大学 | Cognition spectrum sensing device and method on basis of DVB-T (Digital Video Broadcasting-Terrestrial) frequency band |
| CN104092967B (en) * | 2014-07-14 | 2017-02-15 | 桂林电子科技大学 | Receiver system and receiving method with cognitive function |
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