CN202309690U - Frequency modulation broadcast frequency range digital broadcast signal receiving system - Google Patents
Frequency modulation broadcast frequency range digital broadcast signal receiving system Download PDFInfo
- Publication number
- CN202309690U CN202309690U CN2011202853392U CN201120285339U CN202309690U CN 202309690 U CN202309690 U CN 202309690U CN 2011202853392 U CN2011202853392 U CN 2011202853392U CN 201120285339 U CN201120285339 U CN 201120285339U CN 202309690 U CN202309690 U CN 202309690U
- Authority
- CN
- China
- Prior art keywords
- signal
- digital
- frequency
- analog
- modulation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Landscapes
- Circuits Of Receivers In General (AREA)
Abstract
The utility model relates to a frequency modulation broadcast frequency range digital broadcast signal receiving system, comprising a receiving antenna, a tuning module, an analog digital converter, a digital down converter, an analog frequency modulation signal receiver, an analog frequency modulation broadcast demodulator, a digital analog converter, a low frequency amplifier, and a digital frequency modulation signal demodulation decoder. The digital frequency signal demodulation decoder comprises a primary frequency modulation separator, an iteration frequency modulation separator, and a synchronization recovery and channel equalization and decoding module, thereby realizing the separation of analog main frequency modulation and digital signal iteration. The frequency modulation broadcast frequency range digital broadcast signal receiving system can perform iteration separation on blended digital and analog signals overlapped in a same channel, to eliminate the mutual interference between the digital and analog signals, and restores analog sound broadcast signals and digital sound broadcast signals of a transmitting end, thereby enabling a frequency modulation range digital broadcast system to be realized.
Description
(1) technical field
The utility model belongs to the digital audio broadcasting technical field, specifically is a kind of FM broadcasting frequency band digital apparatus for receiving broadcast signals.
(2) background technology
Amplitude modulation (Amplitude Modulation, AM) broadcasting starts from nineteen twenty, and (Frequency Modulation, FM) broadcasting starts from 1940 to frequency modulation.In China, from the 1950's to the sixties, intermediate waves broadcasting develops rapidly, gets into the seventies, and the FM FM broadcasting emerges rapidly, and the tonequality of broadcasting significantly improves, and FM broadcasting has obtained using widely.Though fast development along with TV, the Internet, mobile radio communication; Traditional audio broadcasting had once become time important medium mode; Development speed lags far behind other main circulation way, but audio broadcasting has its certain applications environment and demand, still is very important medium form; And along with the appearance of new technology, the development of audio broadcasting still has a extensive future.
Be accompanied by global digitized tide; Audio broadcasting has begun digital radio no exceptionly; People have proposed many digitizing technique schemes, mainly contain digital audio broadcasting (DAB, Digital Audio Broadcasting), (DRM of digital am system in Europe; Digital Radio Mondiale) and the hybrid digital of U.S. broadcasting (Hybrid Digital Radio, HD Radio) system.
DAB digital audio broadcast system employing OFDM (Orthogonal Frequency Division Multiplexing, OFDM) modulation system; Has High Data Rate (the clean data transfer rate of main business about 1.5～1.7Mb/s); The high quality audio of CD level can be provided, and characteristics such as have that stronger anti-multipath interference performance, transmitting power are little, the availability of frequency spectrum is high and professional formation is flexible are mainly used in city broadcasting to cover; But; DAB does not have the compatibility of consideration and existing frequency modulation, is to replace to existing FM frequency modulation, and existing FM radio station can only wait DAB after its all band (III wave band, L-band) develops into to a certain degree; Could original FM broadcasting Close All are used for digital audio broadcasting to corresponding frequency modulation frequency range again.Therefore, DAB system and existing frequency modulation system are difficult to realize seamlessly transitting.The digital audio broadcasting DAB canonical reference Europe DAB standard that China formulates; And begun DAB broadcasting on Beijing and other places; But used frequency range is not original modulating FM and amplitude modulation AM frequency range; Divided broadcast band for it specially, and the DAB broadcast receiver costs an arm and a leg, be difficult to obtain user's extensive approval.Therefore, its popularization is restricted, and does not accomplish the marketization and industrialization so far.
DRM digital am system develops to the Mid and Short Wave Amplitude Modulation digitlization below the 30MHz at first; Through studying for many years and realizing; DRM is organized in and has submitted the following digital am broadcasting of 30MHz recommendation (ITU-R BS.1514) to ITU April 4 calendar year 2001, and passes.In November, 2004, the DRM tissue proposed a suggestion that DRM is expanded to 30MHz～120MHz frequency range; Be DRM+; Its target is exploitation and standardization DRM expanding system; Be the digitizing technique of VHF wave band (traditional FM broadcasting frequency range), make its frequency cover wave band I, II and III, become open international standard from the LW wave band to the VHF wave band.DRM+ and FM frequency modulation are as shown in Figure 1 with the spectrogram of broadcasting, the band separation Δ f >=150kHz of DRM+ definition, difference power Δ P >=20dB.
In-band on-channel (In-Band On-Channel; IBOC) HD Radio hybrid digital broadcast system is the digital radio system that is developed to FM FM broadcasting and AM amplitude modulation medium wave broadcast digital improvement by U.S. iBiquity Digital company; The permission that on November 15th, 2000 obtained International Telecommunication Union; In October, 2002, U.S. FCC (FCC) confirms as the unique standards for digital broadcasting of the U.S. with it.The traditional FM broadcasting of the U.S. is distributed in 88～108MHz, and each channel bandwidth is 200kHz, over one hundred the station channel of can layouting approximately.IBOC-FM increases digital sidebands and is used to transmit audio frequency or out of Memory on the basis of original frequency modulation analog frequency band, and each radio station can take the bandwidth of 400kHz, and the compatible existing FM frequency modulation system of IBOC-FM need not redistributed frequency spectrum.Compare with other digital audio broadcast modes, the advantage of HD Radio hybrid digital broadcast system is to realize the smooth transition of analog to digital.But HD Radio system use be fixed on analog signal up and down the digital signal of two sidebands transmit, cause the mutual interference mutually and the signal covering problem of numeral and analog broadcasting.
HD Radio hybrid digital broadcast system two sidebands about conventional FM FM signal have been created the set of number sideband; It has three kinds of spectrum allocation may patterns: mixed mode, extended hybrid pattern, digital pattern; The frequency spectrum that a remarkable common ground of these patterns is analog fm signal and digital frequency-modulation signal does not have overlapping in same analog fm channel, exclusively enjoys certain section channel separately.
Under mixed mode; The digital sidebands that lower sideband increases about 70kHz respectively on original analog fm signal is used for transmission of digital signals; Analog fm signal spectrum position and shape remain unchanged; The spectrum allocation may mode is as shown in Figure 2, and lower sideband is that digital frequency-modulation signal takies on the analog fm signal both sides.Mixed mode (Hybrid Mode) provides the data transfer rate of 97kbps, comprising the auxiliary data of voice data and the 1kbps of 96kbps, the perhaps auxiliary data of the voice data of 64kbps and 33kbps.Compare mixed mode; The partial channel of former simulation FM signal has been occupied in the digital sidebands expansion of extended hybrid pattern (Extended Hybrid Mode); Last lower sideband respectively has more 28kHz, has promptly reduced the bandwidth of analog fm signal, but that both frequency spectrums still do not have is shared; The spectrum allocation may mode is as shown in Figure 3, and analog fm signal both sides arrow indication is lower sideband on the numeral of expansion.The extended hybrid pattern provides the data transfer rate of 147kbps, comprising the auxiliary data of voice data and the 51kbps of 96kbps, the perhaps auxiliary data of the voice data of 64kbps and 83kbps.This pattern is also supported to simulate stereo and radio data system (RDS), in the extended hybrid pattern, has reduced the spectrum width of analog fm signal, makes way for the digital spectrum of expansion, upper and lower each 30kHz of sideband expansion.Under digital pattern, as shown in Figure 4, original analog signal is stopped using, and is replaced by digital signal fully, and the main digital signal both sides are that numeral goes up lower sideband, in addition lower sideband on the numeral of the expansion of arrow indication.Do not had analog signal in the spectrum allocation may mode of digital pattern, the 277kbps data transfer rate can be provided, comprising the auxiliary data of voice data and the 181kbps of 96kbps, the perhaps auxiliary data of the voice data of 64kbps and 213kbps.Can find out that the power of main channel transmission that is in both sides is more a lot of greatly than the channel that mediates.
FM broadcasting spectrogram by Fig. 2,3 and 4 HD Radio hybrid digital broadcast system can be seen; It requires frequency interval is 400kHz; Because existing tuned radio frequency is spaced apart 200kHz; Therefore, broadcast the digital broadcasting that carries out the transition to HD Radio hybrid digital broadcast system by analog fm, with the bandwidth that takies a times more.This is in the intensive area of f-m broadcast station, and possibly can't be with all radio station digitlizations.To this, HD Radio hybrid digital broadcast system has adopted half-way house, when the FM radio station frequency planning, guarantees that the radio station of 200kHz does not appear in the adjacent both sides of FM radio station simultaneously.Nonetheless, system still need consider the first adjacent channel interference problem.
For example; Work in sideband digital signal among the HD Radio of mixed mode in the simulation homophony frequently between centre frequency 129.361～198.402kHz; As shown in Figure 5, based on channel spacing be 200kHz first adjacent (, dot) frequently apart from homophony centre frequency+200kHz place frequently and homophony frequency domain channel (solid line) between have the phase mutual interference; First adjacent channel possibly be original analog fm signal, or another HD Radio channel.Can find out that first adjacent channel is very serious to the interference of digital sidebands in the homophony frequency domain channel, broken line triangle has covered homophony upper sideband digital signal frequently fully among the figure.Equally, consider that then the lower sideband digital signal in the homophony frequency domain channel also will all be disturbed and cover apart from the homophony adjacent channel interference at centre frequency-200kHz place frequently.
Owing to have comparatively serious disturbance between the homophony frequency domain channel and first adjacent channel, therefore, need take signal processing technology from have the environment that disturbs, to isolate the useful signal that needs.A kind of FM signal isolation technics is referred to as COLT (COntinuous Look Through; Browse continuously); It is used for from the broadband, and FM signal extracts narrow band signal; Its effect is similar to notch filter, follows the tracks of and suppress the frequency modulation instantaneous frequency of interference signal, referring to United States Patent (USP) U.S.Pat.Nos.5263191.Because FM HD Radio signal receives various influence of fading and bandwidth characteristic in communication process, this has limited the actual effect of COLT technology.Therefore, United States Patent (USP) U.S.Pat.Nos.6259893 has described the method that the other a kind of HD of minimizing Radio FM disturbs.At first the mixed signal that receives being carried out normalization handles; Multiply each other the complex conjugate of mixed signal after the normalization and original mixed signal then, obtain a real signal, this real signal through a high-pass filtering after; Multiply each other with the normalization mixed signal; Produce last output signal, the interference signal in the output has obtained minimizing with respect to useful signal, thereby is easy to detect useful signal.
In China, frequency modulation audio broadcasting frequency scope dictates is at 87～108MHz, and its spectrum allocation may is as shown in Figure 6.Domestic frequency modulation audio broadcast mode is by GBT 4311 standards, and modulation frequency is spaced apart 200kHz.Except monophony and stereophonic broadcasting, broadcasting of multichannel sound and frequcny modulation data are broadcasted two types to have gone back standard.The existing FM broadcasting of China is main with analog signal; Utilize the base band idle frequency spectrum to modulate the mode of additional information though also defined FM broadcasting; But additional digital sidebands smaller bandwidth is mainly used in the auxiliary data message of transmission, and can not be transmitting digitized analog audio information.
The frequency spectrum of HD Radio system digital frequency-modulation signal of analog fm signal and last lower sideband in main channel is nonoverlapping fully, but has mutual interference mutually with first adjacent channel, therefore is difficult to be applicable to existing frequency modulation frequency range, for example the frequency modulation channel of China.Real same frequency has appearred for this reason with band (Truly in-band-on-channel; TIBOC) digital-to-analogue audio droadcasting system; Frequency spectrum is as shown in Figure 7; The frequency spectrum of simulation homophony frequency signal and digital frequency-modulation signal is overlapping fully, and promptly identical frequency modulation channel is used for transportation simulator homophony signal and digital frequency-modulation signal frequently simultaneously.Digital frequency-modulation signal wherein is through chnnel coding and modulation, so that resist noise and interference better.Digital modulation signals can be traditional OFDM (Orthogonal Frequency Division Multiplexing, OFDM) multi-carrier scheme, single-carrier scheme, perhaps spread spectrum scheme.More employing OFDM scheme.
The mixed signal of simulation homophony frequency signal and digital frequency-modulation signal is expressed as
x(t)＝x
FM(t)+d(t)
Wherein d (t) representes the digital frequency-modulation signal of transmission; X
FM(t) expression simulation homophony frequency signal.With being with together frequently in the broadcast system, the influence of signal frequently is subject to digital modulation signals to the simulation homophony at traditional I BOC:
The a.OFDM signal power is lower than simulation homophony signal power 25dB frequently;
B. in fundamental mode, the ofdm signal frequency spectrum does not have overlapping with simulation homophony frequency signal spectrum; In mode of extension, both overlapping scopes are conditional.
Adopt the methods such as COLT of above-mentioned hybrid digital broadcasting to recover to separate FM signal, when eliminating analog fm signal then and then obtaining digital frequency-modulation signal, residual analog fm signal just becomes the background noise of digital signal.
Therefore; In the TIBOC digital-to-analogue audio droadcasting system of real same frequency with band, simulation homophony frequency signal and digital modulation signals frequency spectrum are overlapping fully, adopt traditional frequency modulation isolation technics; The analog fm signal of demodulation will become the part of ofdm signal; And the residual noise power that is derived from analog fm signal will be much larger than the power of ofdm signal, makes the requirement that the digital modulation signals that recovered does not reach certain signal to noise ratio, influences the quality of reception of digital modulation signals.Simultaneously, the interference of signal frequently makes simulation homophony frequency signal accurately to recover to digital modulation signals to the simulation homophony.This critical technical problems makes the complete overlapping digital-to-analogue audio droadcasting system of digital-to-analogue frequency spectrum be difficult to realize.
(3) utility model content
The purpose of the utility model is a kind of FM broadcasting frequency band digital apparatus for receiving broadcast signals of design; To simulating the problem that homophony frequency signal and digital frequency-modulation signal are difficult to good separation in broadcasting together in the overlapping fully band of frequency spectrum; The separator that simulation homophony frequency and digital signal iteration are offset has been proposed; Make the simulation homophony frequently can separate preferably with digital signal; Recover clean simulation homophony broadcast singal frequently, the signal to noise ratio of digital frequency-modulation signal reaches requirement simultaneously, obtains high-quality digital audio broadcasting.
What the FM broadcasting frequency band digital broadcast signal received method of the utility model design was directed against is the digital broadcast signal of the FM broadcasting frequency range radio frequency digital-to-analogue mixing of digital-to-analogue audio broadcasting emission; The shared frequency modulation channel of simulated sound broadcast singal and digital audio broadcast singal in this digital broadcast signal, their frequency spectrum is overlapping fully.Digital audio broadcast singal is wherein handled through OFDM modulation (OFDM) and is obtained; Between each OFDM symbol of digital signal, insert protection (Guard Interval at interval; GI), Cyclic Prefix OFDM (Cyclic Prefix OFDM, CP-OFDM) mode have been adopted; Put into a Cyclic Prefix in the GI at interval in protection, become the cycle expansion of an OFDM symbol.In the subcarrier of OFDM modulation, inserted pilot tone (pilot) signal; The power of pilot signal can be higher than the power of digital audio broadcast singal; So that receiving terminal is easy to detect pilot signal; Said pilot signal is the continuous pilot signal that inserts continuously at some subcarrier, and perhaps for pressing the discrete guide-frequency signal that predetermined way disperses insertion, so far this broadcasting equipment transmitting terminal signal has been accomplished chnnel coding and modulation.Promptly send into speed adjustment filter unit then, transmission code rate is regulated in through-rate adjustment filtering, obtains the digital audio broadcast singal.
The inserted mode of discrete guide-frequency signal is every at a distance from 1 pilot signal of several subcarriers insertions; Insert pilot signal by staggered position in the perhaps adjacent OFDM symbol; The position that pilot signal is inserted behind m OFDM symbol is cycle repeats again, and the pilot signal of when m=4, inserting forms argyle design.
Can contain ISN in the digital frequency-modulation signal, the corresponding ISN code word of each OFDM symbol or several OFDM symbol.ISN can adopt any in convolution code, RS sign indicating number, BCH code, LDPC sign indicating number (Low Density Parity-check Code, loe-density parity-check code) and the Turbo code.ISN constitutes cascaded code with outer sign indicating number, for example convolution code+LDCP sign indicating number or RS sign indicating number+convolution code, or the BCH+LDPC sign indicating number etc.
This FM broadcasting frequency band digital broadcast signal received method carries out initial gross separation, the analog fm signal x that is tentatively recovered after receiving the digital broadcast signal x (t) of FM broadcasting frequency range radio frequency digital-to-analogue mixing with the analog fm signal receive mode
0 FMAnd obtain from x (t), having eliminated the preliminary recovery digital frequency-modulation signal d of analog fm signal (t),
0(t).The preliminary x that recovers
0 FM(t) and d
0(t) carry out the iteration frequency modulation separating treatment of the first order based on pilot tone; Obtain utilizing digital frequency-modulation signal and the analog fm signal of recovering after the first order alternate analysis of pilot tone, the digital frequency-modulation signal that alternate analysis obtains carries out obtaining digital audio and video signals and data-signal behind the channel-decoding; The analog fm signal that alternate analysis obtains is carried out simulated audio signal and is separated the mediation digital-to-analogue conversion, obtains simulated audio signal.
The receiving system of the FM broadcasting frequency band digital broadcast singal of the utility model design comprises reception antenna, tuner module, A-D converter, digital down converter, analog fm signal receiver, analog fm broadcast demodulator, digital-to-analog converter and low frequency amplifier, also has digital frequency-modulation signal demodulating and decoding device.
The radio frequency rf signal that reception antenna receives inserts digital down converter then through tuner module, convert digital signal into through digital-to-analog converter again, simultaneously with the reception signal feedback after the digital-to-analog converter digitlization to tuner module, be used for automatic gain control.Digital down converter becomes signal into medium-frequency IF signal or zero intermediate frequency signals, sends into the code check of resampling module through interior slotting change data, is convenient to the processing of back.One tunnel output signal of resampling module is received the demodulation that the analog fm receiver carries out analog fm signal, and another road signal is received digital frequency-modulation signal demodulating and decoding device, recovers the digital audio and video signals and the data-signal of making a start and sending.
The analog fm receiver is a prior art, comprises the amplitude limit band pass filter, differentiator and the frequency discriminator that connect successively.Frequency discriminator can be phase-locked loop frequency demodulator or envelope detection frequency discriminator.The analog-digital blended signal x (t) of input is through signal limiter and bandpass filtering; The changes in amplitude that FM signal produces in broadcasting process is partly removed; Become the frequency-modulated wave of fixed amplitude; Band pass filter passes through by FM signal smoothly, and filtering out-of-band noise and higher harmonic components reduce noise jamming.Differentiator becomes the frequency-modulated wave of constant amplitude into amplitude-modulation & frequency-modulationwave, from changes in amplitude, detects modulation signal x with frequency discriminator again
0 FM(t).
Digital frequency-modulation signal demodulating and decoding device comprises preliminary frequency modulation separator, iteration frequency modulation separator, recovery synchronously and channel equalization module, channel decoding module.The preliminary analog fm signal x that recovers after analog-digital blended signal x (t) that receives and the demodulation of analog fm receiver
0 FM(t) insert preliminary frequency modulation separator, from x (t), deduct x
0 FM(t) the digital frequency-modulation signal d that is tentatively recovered
0(t).The preliminary analog fm signal x that recovers of analog fm receiver
0 FM(t), the preliminary figure FM signal d that obtains of preliminary frequency modulation separator
0(t) and synchronously recover channel response information C (k) access iteration frequency modulation separator with the channel equalization module.Through progressively eliminate based on the first order iteration of pilot tone and two kinds of FM signals of digital-to-analogue between the phase mutual interference, obtain the analog fm signal of relative clean
And digital frequency-modulation signal
Iteration frequency modulation separator is with the balanced d of channel response C (k)
0(t) the frequency-region signal D that obtains through FFT
0(k), i.e. D
0(k) * C (k).For the phase mutual interference between elimination and two kinds of FM signals of digital-to-analogue better, the second level iteration based on pilot tone and ISN also can be arranged, realize separating of simulation homophony frequency and the counteracting of digital signal iteration.
The digital frequency-modulation signal
of iteration frequency modulation separator output inserts and recovers synchronously and the channel equalization module; Carrier error and timing offset are promptly calculated in recovery synchronously; To the laggard link synchronization tracing of error filtering; Obtain system synchronization; Channel equalization then is to estimate the characteristic of channel; Various declines to the broadcast radiated process produces are proofreaied and correct, and feed back to digital down converter, resampling module and the iteration frequency modulation separator of front end to information such as carrier wave, timing and channel responses respectively.The output access channel decoder module of recovery and channel equalization module carries out forward error correction (FEC, Forward Error Correction) channel-decoding synchronously.Channel decoding module contains a deinterleaver, is used to improve the resistance that the data paired pulses disturbs.The output of channel decoding module inserts the source coding module, finally obtains the digital audio and video signals and the data-signal of making a start and sending.
The analog fm signal
of iteration frequency modulation separator output is sent into the analog fm demodulator; Obtain an audio signal that satisfies quality requirement; Convert an analoging sound signal into through D/A converter again, through low frequency amplifier rear drive loud speaker.
The first order of said iteration frequency modulation separator is following based on the iteration frequency modulation method for separating and processing of pilot tone: d
k(t) digital frequency-modulation signal of expression k step iteration recovery, x
k FM(t) analog fm signal of expression k step iteration recovery; Δ x
k FM(t) error of the FM signal that obtains of expression k step iteration, when supposing that iteration is initial, Δ x
k FM(t) be 0; The preliminary x that recovers
0 FM(t) and d
0(t) be iteration initial input signal.Wherein the process of k step iteration is following, at first to d
k(t) with Δ x
k FM(t) summation is then to both summed result d
K+1(t) carry out the fast fourier transform computing, i.e. FFT computing obtains the orthogonal frequency-division multiplex singal of demodulation, i.e. ofdm signal.Based on the pilot signal that is inserted in each OFDM symbol (OFDM symbol); Use these known pilot signals to replace being used for fast fourier transform (FFT) frequency of pilot signal, carry out fast fourier inverse transformation computing again, i.e. after the IFFT computing; Rebuild time domain OFDM signal, be expressed as d
Recon(t).After promptly doing the pilot tone replacement exactly, remake the IFFT computing based on pilot signal reconstruction OFDM symbol.d
Recon(t) and d
k(t) difference signal between is expressed as Δ d
k(t).The error delta d of the digital frequency-modulation signal that the utility model setting iteration obtains
k(t) be a part that is derived from analog fm signal, the analog fm update signal is so:
x
FM updated(t)＝x
k FM(t)+Δd
k(t)
FM signal is a constant envelope signal, and its planisphere is a circle.Work as x
FM Updated(t) in the time of not on the permanent envelope planisphere circumference of FM signal, utilize the permanent envelope character of FM signal, rebuild x with this circumference
K+1 FM(t), can be from x
FM Updated(t) rebuild analog fm signal x
K+1 FM(t), deposit register in, be used for k+1 step iteration; Utilize x simultaneously
FM Updated(t) and x
K+1 FM(t) obtain
Then
The x that calculates
K+1 FM(t), d
K+1(t) together as the input of the k+1 time iteration of next round.
When iterations reaches predetermined numerical value M, the perhaps Δ x of adjacent iteration order
k FM(t) or Δ d
k(t) difference in change is equal to or less than parameter δ, iteration stopping.The value of parameter δ is 0≤δ≤0.002.d
M(t) compose to variable
As based on the digital frequency-modulation signal that recovers after the pilot tone; x
M FM(t) compose to variable
As based on the analog fm signal of recovering after the pilot tone.
and?
as the first iteration of the output signal level.
Factors such as quality and iteration implementation complexity, the iterative processing time delay of desired restoring signal are depended in the selection of M value, through the selected M value of taking into account the compromise of each essential condition of Computer Simulation, generally select M=8～12.
Digital frequency-modulation signal that obtains after the first order alternate analysis and analog fm signal are still not too satisfactory, can increase the alternate analysis of the second level by means of pilot tone and ISN again, and alternate analysis process in the second level is similar with first order alternate analysis.
In the alternate analysis of the second level, d
n(t) digital frequency-modulation signal of expression n step iteration recovery, x
n FM(t) analog fm signal of expression n step iteration recovery; Δ x
n FM(t) error of the FM signal that obtains of expression n step iteration, when supposing that iteration is initial, Δ x
n FM(t) be 0; First order iteration is utilized the digital frequency-modulation signal that recovers after the pilot tone
With utilize the analog fm signal of recovering after the pilot tone
Input signal for second level iteration.Wherein the process of n step iteration is following, at first to d
n(t) with Δ x
n FM(t) summation is then to both summed result d
N+1(t) carry out the FFT computing, obtain the OFDM symbol.Pilot signal with known exact position replaces receiving the pilot sub-carrier that frequency modulation pollutes in the OFDM symbol, and for the data carrier of non-pilot tone, the error-correcting decoding information that provides through ISN retrains.The error-correcting decoding information that so-called ISN provides promptly refers to the possible value for non-pilot data carrier wave that obtains behind the error-correcting decoding.After replacing data on the non-pilot data carrier wave and carry out the IFFT computing again with these possible values, rebuild time domain OFDM signal, be expressed as d
Recon(t).d
Recon(t) and d
n(t) difference signal between is expressed as Δ d
n(t).The analog fm update signal is:
x
FMupdated(t)＝x
n FM(t)+Δd
n(t)
Utilize the permanent envelope character of FM signal, rebuild x with circumference
N+1 FM(t), from x
FM Updated(t) rebuild the analog fm signal x that n+1 step iteration is recovered
N+1 FM(t), deposit register in, be used for n+1 step iteration; Utilize x simultaneously
n FM(t) and x
N+1 FM(t) obtain Δ x
n FM(t)=x
N+1 FM(t)-x
n FM(t), then with Δ x
n FM(t), x
K+1 FM(t) and d
K+1(t) begin the n+1 time new iteration as input parameter.
When iterations reaches predetermined numerical value of N, the Δ x of adjacent iteration order
n FM(t) or Δ d
n(t) difference in change is equal to or less than parameter δ, iteration stopping.The value of parameter δ is 0≤δ≤0.002.At this moment, d
N(t) compose to variable
Utilize the digital frequency-modulation signal that recovers behind pilot tone and the ISN as the second level, give the channel error correction decoding of back; X
N FM(t) compose to variable
Utilize the analog fm signal of recovering behind pilot tone and the ISN as the second level, give the analog fm demodulator, can obtain higher-quality analog fm broadcasting.
The selection of N value is the same with the selection principle of front M value, generally selects N=8～12.
The advantage of the receiving system of the utility model FM broadcasting frequency band digital broadcast singal is:
1, receive simulation homophony signal and the complete overlapping mixing digital-to-analogue radiofrequency signal of digital broadcast signal frequency spectrum frequently, separation simulation homophony frequency signal and digital broadcast signal are eliminated the phase mutual interference of the two preferably well; 2, simple in structure, dependable performance is easy to realize.
(4) description of drawings
Fig. 1 is European DRM+ spectrum allocation may pattern diagram;
Fig. 2 is the mixed mode spectrum diagram of IBOC-FM;
Fig. 3 is the enhancing mixed mode spectrum diagram of IBOC-FM;
Fig. 4 is the digital mode spectrum sketch map of IBOC-FM;
Fig. 5 is main channel and the first adjacent channel frequently mutual interference sketch map mutually of IBOC-FM.
Fig. 6 is Chinese FM spectrum allocation may sketch map;
Fig. 7 is the digital-to-analogue spectrum of FM signal sketch map of spectrum overlapping;
Fig. 8 is this FM broadcasting frequency band digital broadcast signal received method embodiment alternate analysis flow chart;
Fig. 9 is based on the first order FM signal alternate analysis flow chart of pilot tone among Fig. 8;
Figure 10 is based on the second level FM signal alternate analysis flow chart of pilot tone and ISN among Fig. 8;
Figure 11 is the receiving system example structure sketch map of this FM broadcasting frequency band digital broadcast singal;
Figure 12 is the receiving system embodiment Computer Simulation SNR～BER performance curve of this FM broadcasting frequency band digital broadcast singal.
(5) embodiment
The receiving system of the digital-to-analogue FM signal of the spectrum overlapping of present embodiment is used to receive the radio frequency digital-to-analogue mixed signal of digital-to-analogue audio broadcasting emission; The shared frequency modulation channel of simulated sound broadcast singal and digital audio broadcast singal in this radio frequency digital-to-analogue mixed signal, frequency spectrum are overlapping fully; This receiving system received RF digital-to-analogue mixed signal and with its two separation obtains high-quality analog-and digital-two kinds of sound broadcasting signals.
The signal frame that information such as the audio frequency of formation digital audio broadcast singal and data flow, synchrodata, control data, pilot tone are formed is sent into OFDM modulation treatment (OFDM) unit; The different business data centralization is got up through inverse Fourier transform; And place on the corresponding OFDM time frequency grid; Be on the subcarrier of different time different frequency, obtain the frequency spectrum of digital signal.Between each OFDM symbol of digital signal, insert protection (Guard Interval at interval then; GI); In the present embodiment, Cyclic Prefix OFDM (Cyclic Prefix OFDM, CP-OFDM) mode have been adopted; In GI, put into a Cyclic Prefix, become the cycle expansion of an OFDM symbol.
The corresponding ISN code word of each OFDM symbol of the digital-to-analogue FM signal of present embodiment or several OFDM symbol; ISN constitutes the serially concatenated error correcting code with outer sign indicating number, and in this example, ISN has adopted convolution code; Outer sign indicating number adopted loe-density parity-check code (Low Density Parity Check, LDPC).
Said ISN also can adopt the error correcting code of other form, for example RS sign indicating number (Reed Solomon code), perhaps BCH (Bose, Ray-Chaudhuri, Hocquenghem Code), LDPC sign indicating number etc.
The opposite order of transmitter according to the digital-to-analogue FM signal of spectrum overlapping is carried out demodulating and decoding, can obtain the data of source end.
The receiving system block diagram of this routine FM broadcasting frequency band digital broadcast singal is shown in figure 11; Comprise reception antenna, tuner module, A-D converter (A/D converter), digital down converter, analog fm signal receiver, analog fm broadcast demodulator, digital-to-analog converter and low frequency amplifier, also have digital frequency-modulation signal demodulating and decoding device.
The radio frequency rf signal of the FM broadcasting frequency band digital broadcasting that reception antenna receives is through tuner module, convert digital signal into through digital-to-analog converter again; Insert digital down converter then; Reception signal after the digital-to-analog converter digitlization feeds back to tuner module through the automatic gain control module simultaneously, is used for automatic gain control.Digital down converter becomes signal into medium-frequency IF signal or zero intermediate frequency signals, sends into the code check of resampling module through interior slotting change data, is convenient to the processing of back.One tunnel output signal of resampling module is received analog fm receiver (simulation FM receiver) and is carried out the demodulation of analog fm signal; Another road signal is received digital frequency-modulation signal demodulating and decoding device (digital FM demodulating and decoding device), recovers the digital audio and video signals and the data-signal of making a start and sending.
The analog fm receiver is a prior art, comprises the amplitude limit band pass filter, differentiator and the frequency discriminator that connect successively.This example adopts the envelope detection frequency discriminator.The analog-digital blended signal x (t) of input is through signal limiter and bandpass filtering; The changes in amplitude that FM signal produces in broadcasting process is partly removed; Become the frequency-modulated wave of fixed amplitude; Band pass filter passes through by FM signal smoothly, and filtering out-of-band noise and higher harmonic components reduce noise jamming.Differentiator becomes the frequency-modulated wave of constant amplitude into amplitude-modulation & frequency-modulationwave, from changes in amplitude, detects modulation signal x with frequency discriminator again
0 FM(t).
Digital frequency-modulation signal demodulating and decoding device comprises preliminary frequency modulation separator, iteration frequency modulation separator, recovery synchronously and channel equalization module, channel decoding module.The preliminary analog fm signal x that recovers after analog-digital blended signal x (t) that receives and the demodulation of analog fm receiver
0 FM(t) insert preliminary frequency modulation separator (preliminary FM separator), from x (t), deduct x
0 FM(t) the digital frequency-modulation signal d that is tentatively recovered
0(t).The preliminary analog fm signal x that recovers of analog fm receiver
0 FM(t), the preliminary figure FM signal d that obtains of preliminary frequency modulation separator
0(t) and synchronously recover channel response information C (k) access iteration frequency modulation separator with the channel equalization module; Through based on the first order iteration of pilot tone, based on the second level iteration of pilot tone and ISN progressively eliminate and two kinds of FM signals of digital-to-analogue between the phase mutual interference, obtain the analog fm signal of relative clean
And digital frequency-modulation signal
Iteration frequency modulation separator is with the balanced d of channel response C (k)
0(t) the frequency-region signal D that obtains through FFT
0(k), i.e. D
0(k) * C (k).The digital frequency-modulation signal
of iteration frequency modulation separator output inserts and recovers synchronously and the channel equalization module; Carrier error and timing offset are promptly calculated in recovery synchronously; To the laggard link synchronization tracing of error filtering; Obtain system synchronization; Channel equalization then is to estimate the characteristic of channel; Various declines to the broadcast radiated process produces are proofreaied and correct, and feed back to digital down converter, resampling module and the iteration frequency modulation separator of front end to information such as carrier wave, timing and channel responses respectively.The output access channel decoder module of recovery and channel equalization module carries out forward error correction (FEC, Forward Error Correction) channel-decoding synchronously.Channel decoding module contains a deinterleaver, is used to improve the resistance that the data paired pulses disturbs.In the present embodiment, FEC has adopted cascaded code, and at first ISN is removed the local channel error code, through the outer sign indicating number of cascade, further reduces remaining error code then, improves progressive performance.The ISN of present embodiment has adopted convolution code, and the outer sign indicating number of FEC has adopted the LDPC sign indicating number.The LDPC decoder of channel decoding module is the soft-decision iterative decoder, and when iterative process has reached the maximum iteration time (intact iteration) of regulation, or when in wrong detection and error correcting processing, not had error code (part iteration), iterative process just finishes.Also error correction data is gone randomization in channel decoding module.Channel decoding module goes the code stream after the randomization to insert the source coding module, digital audio and video signals and data-signal that final recovery is made a start and sent.
The analog fm signal
of iteration frequency modulation separator output is sent into the analog fm demodulator; Obtain an audio signal that satisfies quality requirement; Be converted to high-quality analoging sound signal through D/A converter again, this analoging sound signal can directly drive loud speaker behind low frequency amplifier.
For above-mentioned FM broadcasting frequency band digital broadcast signal received method embodiment is estimated; Employing is based on 2400 length L DPC sign indicating numbers; The OFDM digital signal has been carried out Computer Simulation than the digital-to-analogue FM signal of the low 25dB of frequency modulation analog signal power, and (BER～SNR) curve is shown in figure 12 to obtain the error rate～signal to noise ratio; Wherein dotted line is the result of this routine FM broadcasting frequency band digital broadcast signal received method, and solid line is the result who does not carry out the alternate analysis of the utility model.Can find out that therefrom the performance of this routine FM broadcasting frequency band digital broadcast signal received method is greatly improved.
On base of digital simulation; Can edit this FM broadcasting frequency band digital apparatus for receiving broadcast signals of gate array (FPGA) and digital signal processor (DSP) realization with the scene; Receive the digital-to-analogue hybrid digital broadcast singal of FM broadcasting frequency range spectrum overlapping; Respond well, the broadcasting of the simulated sound of output and digital audio are broadcasted and have all clearly been reduced the original sound signal of transmitting terminal.
The foregoing description is merely concrete example of purpose, technical scheme and beneficial effect further explain to the utility model, and the utility model is not to be defined in this.All any modifications of within the scope of disclosure of the utility model, being made, be equal to replacement, improvement etc., all be included within the protection range of the utility model.
Claims (4)
1. FM broadcasting frequency band digital apparatus for receiving broadcast signals; Comprise reception antenna, tuner module, A-D converter, digital down converter, analog fm signal receiver, analog fm broadcast demodulator, digital-to-analog converter and low frequency amplifier, digital frequency-modulation signal demodulating and decoding device;
The radiofrequency signal that said reception antenna receives is through tuner module, convert digital signal into through digital-to-analog converter again; Insert digital down converter then; Simultaneously the reception signal feedback after the digital-to-analog converter digitlization is arrived tuner module; Digital down converter becomes signal into intermediate-freuqncy signal or zero intermediate frequency signals, sends into the code check of resampling module through interior slotting change data, and one tunnel output signal of resampling module is received the demodulation that the analog fm receiver carries out analog fm signal; Another road signal is received digital frequency-modulation signal demodulating and decoding device, recovers the digital audio and video signals and the data-signal of making a start and sending;
The analog fm receiver comprises amplitude limit band pass filter, differentiator and the frequency discriminator that connects successively; The analog-digital blended signal x (t) of input becomes the frequency-modulated wave of fixed amplitude through signal limiter and bandpass filtering; Differentiator becomes the frequency-modulated wave of constant amplitude into amplitude-modulation & frequency-modulationwave, from changes in amplitude, detects modulation signal x with frequency discriminator again
0 FM(t); It is characterized in that:
Said digital frequency-modulation signal demodulating and decoding device comprises preliminary frequency modulation separator, iteration frequency modulation separator, recovery synchronously and channel equalization module, channel decoding module, the preliminary analog fm signal x that recovers after analog-digital blended signal x (t) that receives and the demodulation of analog fm receiver
0 FM(t) insert preliminary frequency modulation separator, from x (t), deduct x
0 FM(t) the digital frequency-modulation signal d that is tentatively recovered
0(t); The preliminary analog fm signal x that recovers of analog fm receiver
0 FM(t), the preliminary figure FM signal d that obtains of preliminary frequency modulation separator
0(t) and synchronously recover to insert iteration frequency modulation separator, through progressively eliminating the phase mutual interference between two kinds of FM signals of digital-to-analogue based on the first order iteration of pilot tone, the analog fm signal of acquisition relative clean with the channel response information C (k) of channel equalization module
And digital frequency-modulation signal
Iteration frequency modulation separator is with the balanced d of channel response C (k)
0(t) the frequency-region signal D that obtains through fast Fourier transform
0(k);
The digital frequency-modulation signal
of iteration frequency modulation separator output inserts and recovers synchronously and the channel equalization module; Obtain system synchronization and the various declines of proofreading and correct the broadcast radiated process, and feed back to digital down converter, resampling module and the iteration frequency modulation separator of front end to carrier wave, timing and channel response information respectively; The output access channel decoder module of recovery and channel equalization module carries out the forward error correction channel-decoding synchronously; The output of channel decoding module inserts the source coding module, finally obtains the digital audio and video signals and the data-signal of making a start and sending;
The analog fm signal
of iteration frequency modulation separator output is sent into the analog fm demodulator; Obtain an audio signal that satisfies quality requirement, convert an analoging sound signal into through D/A converter again.
2. FM broadcasting frequency band digital apparatus for receiving broadcast signals according to claim 1 is characterized in that:
Said iteration frequency modulation separator also has the second level iteration based on pilot tone and ISN.
3. FM broadcasting frequency band digital apparatus for receiving broadcast signals according to claim 1 is characterized in that:
The frequency discriminator of said analog fm receiver is phase-locked loop frequency demodulator or envelope detection frequency discriminator.
4. FM broadcasting frequency band digital apparatus for receiving broadcast signals according to claim 1 is characterized in that:
Said channel decoding module contains a deinterleaver.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011202853392U CN202309690U (en) | 2011-08-06 | 2011-08-06 | Frequency modulation broadcast frequency range digital broadcast signal receiving system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011202853392U CN202309690U (en) | 2011-08-06 | 2011-08-06 | Frequency modulation broadcast frequency range digital broadcast signal receiving system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN202309690U true CN202309690U (en) | 2012-07-04 |
Family
ID=46378499
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011202853392U Expired - Lifetime CN202309690U (en) | 2011-08-06 | 2011-08-06 | Frequency modulation broadcast frequency range digital broadcast signal receiving system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN202309690U (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106462557A (en) * | 2014-06-27 | 2017-02-22 | 奥兰治 | Resampling of an audio signal by interpolation for low-delay encoding/decoding |
| CN107493107A (en) * | 2017-09-20 | 2017-12-19 | 深圳思凯微电子有限公司 | In-band on-channel self-interference removing method, device and computer-readable recording medium |
| CN114189410A (en) * | 2021-12-13 | 2022-03-15 | 深圳市日声数码科技有限公司 | Vehicle-mounted digital broadcast audio receiving system |
-
2011
- 2011-08-06 CN CN2011202853392U patent/CN202309690U/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106462557A (en) * | 2014-06-27 | 2017-02-22 | 奥兰治 | Resampling of an audio signal by interpolation for low-delay encoding/decoding |
| CN106462557B (en) * | 2014-06-27 | 2019-03-01 | 奥兰治 | Method, equipment, coder/decoder and the storage medium of resampling audio signal |
| CN107493107A (en) * | 2017-09-20 | 2017-12-19 | 深圳思凯微电子有限公司 | In-band on-channel self-interference removing method, device and computer-readable recording medium |
| CN114189410A (en) * | 2021-12-13 | 2022-03-15 | 深圳市日声数码科技有限公司 | Vehicle-mounted digital broadcast audio receiving system |
| CN114189410B (en) * | 2021-12-13 | 2024-05-17 | 深圳市日声数码科技有限公司 | Vehicle-mounted digital broadcast audio receiving system |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN102394714B (en) | Method and system for receiving digital broadcasting signals in frequency modulation (FM) broadcast bands | |
| CN102307168B (en) | Separation method and receiving device of digital broadcasting analog-to-digital (A/D) signal at frequency modulation (FM) broadcast band | |
| CN102142852B (en) | Method and equipment for transmitting digital-analog audio broadcasting | |
| CN1221115C (en) | Method and apparatus for determining transmission mode and synchronization for digital audio broadcasting signal | |
| JP4269014B2 (en) | Method and apparatus for performing digital broadcast compatible with amplitude modulation | |
| US6005894A (en) | AM-compatible digital broadcasting method and system | |
| CN101855777B (en) | Antenna design for FM radio receivers | |
| US6452977B1 (en) | Method and apparatus for AM compatible digital broadcasting | |
| CN102394739B (en) | Generation method and transmitting equipment for in band on channel (IBOC) digital/analog audio broadcast signals | |
| CN105359446A (en) | Implicit signalling in OFDM preamble with embedded signature sequence, and cyclic prefix and postfix aided signature detection | |
| CN105144616A (en) | Method and apparatus for transmission and reception of in-band on-channel radio signals including complementary low density parity check coding | |
| JPH11512242A (en) | Method of transmitting digital data via a radio broadcast channel having a fault and a receiver for digital data transmitted via a radio channel having a fault | |
| CN202309690U (en) | Frequency modulation broadcast frequency range digital broadcast signal receiving system | |
| CN202406103U (en) | Transmitting apparatus for in-band on-channel digital-analog audio frequency broadcast signal | |
| De Bot et al. | An overview of the modulation and channel coding schemes developed for digital terrestrial television broadcasting within the dTTb project | |
| JP3607589B2 (en) | Method and apparatus for performing differential modulation on frequency in an orthogonal frequency division multiplexing (OFDM) communication system | |
| CN101808067B (en) | Method and device thereof for receiving and transmitting OFDM signals by using differential data as pilot frequencies | |
| de Bot et al. | An example of a multi-resolution digital terrestrial TV modem | |
| CN202085153U (en) | Transmitting device for digital-analog audio frequency broadcast | |
| JP3782246B2 (en) | BST-OFDM signal generator / distributor | |
| Ernest | DAB implementation in SDR | |
| CN103220251A (en) | Improved method for generating in-band on-channel digital-analog audio broadcasting signals | |
| Benedetto et al. | Performance of the COFDM systems with waveform shaping | |
| WO2013023595A1 (en) | Method and apparatus for frequency synchronization and receiving of digital audio broadcast signal | |
| Agarwal | Digital Audio Broadcast: Modulation, Transmission & Performance Analysis |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| ASS | Succession or assignment of patent right |
Owner name: SHENZHEN SIKAI MICROELECTRONIC CO., LTD. Free format text: FORMER OWNER: SIQI COMMUNICATION EQUIPMENT CO., LTD., GUILIN CITY Effective date: 20150909 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20150909 Address after: 518057 Guangdong province Shenzhen Nanshan District Tea Light Road 1089 integrated circuit design application Industrial Park Room 508 Patentee after: Shenzhen Si Kai Microtronics A/S Address before: 541004, D-08, Chaoyang Information Industrial Park, Qixing District, the Guangxi Zhuang Autonomous Region, Guilin Patentee before: Siqi Communication Equipment Co., Ltd., Guilin City |
|
| CX01 | Expiry of patent term |
Granted publication date: 20120704 |
|
| CX01 | Expiry of patent term |