CN102394739B - Generation method and transmitting equipment for in band on channel (IBOC) digital/analog audio broadcast signals - Google Patents
Generation method and transmitting equipment for in band on channel (IBOC) digital/analog audio broadcast signals Download PDFInfo
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Abstract
The invention relates to a generation method and transmitting equipment for in band on channel (IBOC) digital/analog audio broadcast signals. The method comprises the following steps of: generating analog sound broadcast signals of time discrete; generating digital signals, and copying the digital signals in an adjacent signal frame; adding and subtracting the analog sound broadcast signals *2m, *2m + 1 and the corresponding digital broadcast signals in the adjacent signal frame, and acquiring *2m-dm and *2m + 1 + dm; and emitting acquired digital/analog mixed signals in the same broadcast channel. The transmitting equipment comprises an analog sound modulation module, a digital signal modulation module, a mixing module, a digital/analog converter, an upconversion module, a power amplifier and an antenna feeder system, wherein the mixing module comprises an adder and a subtractor so as to acquire the digital/analog mixed signals. According to the method and the equipment, analog/digital mixed signals with completely overlapped frequency spectrums are acquired, frequency bands are saved, and that a receiving end completely separates the digital/analog signals is facilitated.
Description
(1) technical field
The invention belongs to DAB Technology field, specifically, relate to production method and the transmitting apparatus of mixed in-band on-channel (Time Domain Overlapping-In Band On Channel, TDO-IBOC) the digital-analog audio frequency broadcast signal repeatedly of time domain.
(2) background technology
Amplitude modulation (Amplitude Modulation, AM) broadcast starts from nineteen twenty, and frequency modulation (Frequency Modulation, FM) broadcast starts from 1940 years.In China, from the 1950's to the sixties, intermediate waves broadcast develops rapidly, enters the seventies, and FM FM broadcasting emerges rapidly, and the tonequality of broadcast significantly improves, and FM broadcast is widely used.Although the fast development along with TV, the Internet, mobile radio communication, traditional audio broadcasting had once become time important media method, development speed lags far behind other main mode of transmission, but audio broadcasting has its specific applied environment and demand, it is still 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 the tide of global figure, audio broadcasting has started digital radio no exceptionly, people have proposed many digitizing technique schemes, mainly contain European digital audio broadcasting (DAB, Digital Audio Broadcasting), digital am system (DRM, Digital Radio Mondiale) and the high-fidelity of U.S. broadcast (High Definition Radio, HD Radio) system.
DAB digital audio broadcast system adopts OFDM (Orthogonal Frequency Division Multiplexing, OFDM, ) modulation system, there is High Data Rate (the about 1.5～1.7Mb/s of the clean data transfer rate of main business), the high quality audio of CD level can be provided, there is stronger anti-multipath interference performance, transmitting power is little, availability of frequency spectrum height and business form the features such as flexible, being mainly used in city broadcast covers, but, DAB does not have the compatibility of consideration and existing frequency modulation, to existing FM frequency modulation, be to replace, existing FM radio station can only wait DAB at its all band (III wave band, L-band) after developing into a certain degree, could be by original FM broadcasting Close All, again corresponding frequency modulation frequency range is used for to digital audio broadcasting.Therefore, DAB system and existing frequency modulation system are difficult to realize and seamlessly transit.The digital audio broadcasting DAB canonical reference Europe DAB standard that China formulates, and on Beijing and other places, started DAB broadcast, but frequency range used is not original modulating FM and amplitude modulation AM frequency range, for it, divided broadcast band specially, and DAB broadcast receiver is expensive, be difficult to obtain user's extensive approval.Therefore, its popularization is restricted, and does not accomplish so far the marketization and industrialization.
DRM digital am system is developed for the Mid and Short Wave Amplitude Modulation digitlization below 30MHz at first, through studying for many years and realizing, DRM is organized in and to ITU, has submitted the following digital am broadcast of 30MHz recommendation (ITU-R BS.1514) to April 4 calendar year 2001, and passes.In November, 2004, 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, it is the digitizing technique of VHF wave band (traditional FM broadcasting frequency range), make its frequency coverage wave band I, II and III, become the open international standard from LW wave band to VHF wave band.DRM+ and FM frequency modulation with the spectrogram broadcast as shown in Figure 1, 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 high-fidelity broadcast system Shi You U.S. iBiquity Digital company transforms and the digital radio system of exploitation for FM FM broadcasting and the digitization of broadcasting of AM amplitude modulation medium-wave, obtained the license of International Telecommunications Union (ITU) on November 15th, 2000, in October, 2002, U.S. FCC (FCC (Federal Communications Commission)) is defined as the unique standards for digital broadcasting of the U.S..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 approximately can layouting.IBOC-FM, on the basis of original frequency modulation analog frequency band, increases digital sidebands and is used for transmitting audio frequency or out of Memory, and each radio station can take the bandwidth of 400kHz, and the compatible existing FM frequency modulation system of IBOC-FM, does not need to redistribute frequency spectrum.Compare with other digital Audio Broadcasting modes, the advantage of HD Radio high-fidelity broadcast system is to realize the smooth transition of analog to digital.But HD Radio system is used the digital signal that is fixed on upper and lower two sidebands of analog signal to transmit, and causes phase mutual interference and the signal covering problem of Digital and analog broadcast.
HD Radio high-fidelity broadcast system has created set of number sideband at upper and lower two sidebands of conventional FM FM signal, 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 separately certain section of channel.
Under mixed mode, the digital sidebands that lower sideband increases respectively about 70kHz in original analog fm signal is for transmission of digital signals, analog fm signal spectrum position and shape remain unchanged, as shown in Figure 2, on analog fm signal both sides, lower sideband is that digital frequency-modulation signal takies to spectrum allocation may mode.Mixed mode (Hybrid Mode) provides the data transfer rate of 97kbps, comprising the auxiliary data of voice data and the 1kbps of 96kbps, or the voice data of 64kbps and the auxiliary data of 33kbps.Compare mixed mode, the partial channel of former analog fm signal has been occupied in the digital sidebands expansion of extended hybrid pattern (Extended Hybrid Mode), upper lower sideband respectively has more 28kHz, reduced the bandwidth of analog fm signal, but both frequency spectrums still do not share, as shown in Figure 3, analog fm signal both sides arrow indication is lower sideband in the numeral of expansion to spectrum allocation may mode.Extended hybrid pattern provides the data transfer rate of 147kbps, comprising the auxiliary data of voice data and the 51kbps of 96kbps, or the voice data of 64kbps and the auxiliary data of 83kbps.This pattern is also supported to simulate stereo and radio data system (RDS), in 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 by digital signal, is replaced completely, and main digital signal both sides are the upper lower sideband of numeral, in addition lower sideband in the numeral of the expansion of arrow indication.In the spectrum allocation may mode of digital pattern, there is no analog signal, 277kbps data transfer rate can be provided, comprising the auxiliary data of voice data and the 181kbps of 96kbps, or the voice data of 64kbps and the auxiliary data of 213kbps.Can find out, the power of the main channel transmission in both sides is more much larger than the channel mediating.
FM broadcasting spectrogram by Fig. 2,3 and 4 HD Radio high-fidelity broadcast system can be seen, it requires frequency interval is 400kHz, because existing tuned radio frequency is spaced apart 200kHz, therefore, by analog fm broadcast, be transitioned into the digital broadcasting of HD Radio high-fidelity broadcast system, by the bandwidth that takies a times more.This is in the intensive area of f-m broadcast station, and possibly cannot be by the digitlization of all radio station.To this, HD Radio high-fidelity broadcast system has adopted half-way house, and when FM radio station frequency planning, the radio station of 200kHz appears in the adjacent both sides of assurance FM radio station when different.Nonetheless, system still needs to consider the first adjacent channel interference problem.
HD Radio system analog fm signal in main channel is completely nonoverlapping with the frequency spectrum of the digital frequency-modulation signal of upper lower sideband, but has phase mutual interference with the first adjacent channel, as shown in Figure 5.Therefore be difficult to be applicable to existing frequency modulation frequency range, for example the frequency modulation channel of China.
In China, frequency modulation audio broadcasting frequency scope dictates is at 87～108MHz, and its spectrum allocation may 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, multi-Channel Acoustic broadcast and frequcny modulation data are broadcasted two classes to have gone back standard.The existing FM broadcasting of China be take analog signal as main, although also defined FM broadcasting, utilize base band idle frequency spectrum to modulate the mode of additional information, but additional digital sidebands smaller bandwidth, is mainly used in transmitting auxiliary data message, and can not be transmitting digitized analog audio information.And between current domestic actual FM frequency, be separated with 100kHz, 200kHz, 300kHz, 500kHz and 600kHz etc., frequency service condition is complicated, still has dummy frequencies resource to be underutilized.Existing DAB Technology is inapplicable in China.But be greatly supplementing of frequency-modulation broadcasting by making full use of of FM Digital Realization tuned radio frequency.Therefore, need mixed repeatedly in-band on-channel (the Time Domain Overlapping-In Band On Channel of a kind of new time domain, TDO-IBOC) production method of modulus sound broadcasting signal and corresponding transmitting apparatus, to promote audio broadcasting flourish of China.
(3) summary of the invention
The object of the invention is to propose production method and the transmitting apparatus that a kind of time domain is mixed the digital-analog audio frequency broadcast signal of in-band on-channel repeatedly, simulated sound broadcast singal and digital Audio Broadcasting signal are mixed into a road signal by certain way in time domain, and really share a fm broadcast channel in frequency domain.Do not need to repartition frequency spectrum, frequency spectrum is fully used, saved frequency spectrum resource, and at receiving terminal thoroughly separation simulation sound broadcasting signal and digital broadcast signal.
The production method of the digital-analog audio frequency broadcast signal of the in-band on-channel that the present invention proposes, comprises the following steps:
I, obtain simulated sound broadcast singal;
II, the simulated sound broadcast singal digitlization that step I is obtained, obtain the simulated sound broadcast singal after corresponding digitlization;
III, in adjacent signal frame reproduction digital signal;
This method, in same broadcasting channel, in the digital broadcast signal obtaining, is gone back transmission of one line digital signal at transmission above-mentioned steps II.This digital signal is audio broadcast signal and/or the conventional data-signal of an other railway digital.This digital signal is through Channel Coding and Modulation, to resist better Noise and Interference.The modulation of this digital signal can be traditional OFDM (Orthogonal Frequency Division Multiplexing, OFDM) multi-carrier modulation, or single-carrier modulated, or band spectrum modulation.In adjacent signal frame, copy time-domain digital signal,, in 2m+1 signal frame, copy the time-domain digital signal d of 2m signal frame of an order
m, obtain the time-domain digital signal that a consecutive frame repeats completely, every two adjacent signals frames form the time-domain digital signal of one group of Data duplication.
IV, analog signal and digital signal time domain are mixed, and obtain digital-to-analogue mixed signal;
The time-domain digital signal that simulated sound broadcast singal after the digitlization that the Step II of adjacent signals frame is obtained and corresponding Step II I obtain mixes, in 2m frame, and the simulated sound broadcast singal x after digitlization
2mdeduct corresponding time-domain digital signal d
m, obtain x
2m-d
m; In 2m+1 frame, the simulated sound broadcast singal x after digitlization
2m+1add corresponding time-domain digital signal d
m, obtain x
2m+1+ d
m, obtain the digital-to-analogue mixed signal S=(x transmitting in same broadcasting channel
0-d
0, x
1+ d
0... ..x
2m-d
m, x
2m+1+ d
m... ..), or S=(x
0+ d
0, x
1-d
0... ..x
2m+ d
m, x
2m+1-d
m... ..);
The digital-to-analogue mixed signal that V, step IV obtain is after digital-to-analogue conversion, up conversion and amplification, by antenna transmission.
Simulated sound broadcast singal described in step I is analog fm sound broadcasting signal.
Broadcasting channel described in Step II I is fm broadcast channel.
The digitlization of the simulated sound broadcast singal described in Step II is time discretization.
The Channel Coding and Modulation of the digital signal described in Step II I is OFDM modulation, i.e. OFDM modulation.The Fourier transform length of described OFDM is any in 256,512,1024 and 2028.
Digital signal described in Step II I is also passed through channel error correction coding, and error correction coding has adopted serially concatenated error correcting code, and ISN adopts convolution code, and its female code is that code check is 1/2 convolution code, and generator polynomial is (171
otc, 131
otc), by forced (puncturing), process reliability enhanced deleting, obtain the convolution code of other code check, for example 2/3,3/4,5/6 and 7/8; Outer code adopts loe-density parity-check code (Low Density Parity Check, LDPC), also can adopt other cascaded code form, for example RS code+convolution, or BCH+LDPC code etc.
According to the production method of the digital-analog audio frequency broadcast signal of above-mentioned in-band on-channel, the transmitting apparatus of the digital-analog audio frequency broadcast signal of the in-band on-channel of the present invention's design, comprise simulated sound modulation module, digital signal modulated module, mixing module, digital to analog converter, up-conversion module, power amplifier and antenna-feedback system
The simulated sound modulation module that produces simulated sound broadcast singal by required frequency range, its input is connected to external audio source; The input that produces the digital signal modulated module of digital signal by the identical frequency range of simulated sound broadcast singal is connected to external audio source and/or data source; The input of mixing module is connected to the output of simulated sound modulation module and the output of digital modulation module, and the output of mixing module is connected to digital to analog converter; The output of digital to analog converter is connected to up-conversion module; The output of up-conversion module is connected to power amplifier; The output of power amplifier is sent into antenna-feedback system by antenna transmission.
Described digital signal modulated module comprises precoding unit, multiplexed unit and digital modulator; Multi-channel analog or digital audio and video signals and data flow access precoding unit, precoding unit comprises A/D converter, preaccentuator, condensing encoder, the output access multiplexer unit of precoding unit, multiplexed unit connects digital modulator again, and digital modulator comprises scrambler, channel encoder, constellation mapping unit, becomes frame unit, OFDM modulation processing unit, time domain copied cells; The code stream access scrambler of input, sends into constellation mapping unit after channel encoder, meanwhile, synchronize data of system and control data, also channel encoder is sent into constellation mapping unit respectively; The output of each constellation mapping unit through becoming frame unit, OFDM modulation processing unit, connects time domain copied cells with pilot signal, and time domain copied cells copies time-domain digital signal d in the adjacent signals frame of two group
m, the output of time domain copied cells is the output of digital signal modulated module, access mixing module.
Described mixing module comprises a subtracter and adder, respectively the digital signal d repeating on adjacent signals frame
mwith corresponding digitized simulated sound broadcast singal x
2m, x
2m-1add and subtract mutually the mixed signal S=(x that shares a broadcasting channel of output
0-d
0, x
1+ d
0, ... and ..x
2m-d
m, x
2m+1+ d
m... ..), or S=(x
0+ d
0, x
1-d
0... ..x
2m+ d
m, x
2m+1-d
m... ..).
Described simulated sound modulation module is analog fm sound radio modulation module, and described digital signal modulated module is digital audio and/or data broadcast modulation module.
Described simulated sound modulation module contains Direct Digital Frequency Synthesizers.
Described digital signal modulated module comprises precoding unit, multiplexed unit and digital modulator; Multi-channel analog and/or digital audio and video signals and data flow access precoding unit, precoding unit comprises A/D converter, preaccentuator, condensing encoder, the output access multiplexer unit of precoding unit, multiplexed unit connects digital modulator again, and digital modulator comprises scrambler, channel encoder, constellation mapping unit, becomes frame unit, OFDM modulation processing unit, time domain copied cells; The code stream access scrambler of input, sends into constellation mapping unit after channel encoder, meanwhile, synchronize data of system and control data, also channel encoder is sent into constellation mapping unit respectively; The output of each constellation mapping unit through becoming frame unit, OFDM modulation processing unit, connects time domain copied cells with pilot signal, and the output of time domain copied cells is the output of digital signal modulated module.
The Fourier transform length of described OFDM modulation processing unit is any in 256,512,1024 and 2028.
Described channel encoder is LDPC code error correction coding unit.
Described simulated sound modulation module and digital signal modulated module output signal share channel are fm broadcast channel.
The production method of digital-analog audio frequency broadcast signal and the advantage of transmitting apparatus of in-band on-channel of the present invention are: 1, in a broadcasting channel, method and the corresponding equipment of simulated sound broadcast singal and the complete overlapping analog-digital blended signal of digital signal frequency spectrum have been proposed to produce, at transmitting terminal, keep compatible with existing analog broadcast channel, do not need to repartition frequency spectrum, frequency spectrum is fully used, has saved frequency spectrum resource; 2, it is separated that the analog-digital blended signal that this method sends with equipment is convenient to receiving terminal, can eliminate the phase mutual interference of simulated sound broadcast singal and digital signal, realizes the good reduction of simulated sound broadcast singal and digital signal.
(4) accompanying drawing explanation
Fig. 1 is European DRM+ spectrum allocation may pattern.
Fig. 2 is the mixed mode frequency spectrum of IBOC-FM.
Fig. 3 is the enhancing mixed mode frequency spectrum of IBOC-FM.
Fig. 4 is the digital mode spectrum of IBOC-FM.
Fig. 5 is main channel and the first adjacent FM channel channel phase mutual interference schematic diagram of IBOC-FM.
Fig. 6 is Chinese frequency modulation spectrum allocation may schematic diagram.
Fig. 7 is that the production method embodiment of the digital-analog audio frequency broadcast signal of this in-band on-channel adopts modulus frequency modulation channel spectrum diagram.
Fig. 8 is the time domain adjacent signals frame reproduction digital signal schematic diagram of production method embodiment of the digital-analog audio frequency broadcast signal of this in-band on-channel.
Fig. 9 is the transmitting apparatus example structure block diagram of the digital-analog audio frequency broadcast signal of this in-band on-channel.
(5) embodiment
Below in conjunction with accompanying drawing, specific embodiments of the invention are described in detail.
The mixed repeatedly production method embodiment of the audio broadcast signal of in-band on-channel
The production method embodiment of the mixed repeatedly in-band on-channel audio broadcast signal of this digital-to-analogue time domain in time domain simulated sound broadcast frequency modulation signals and digital signal repeatedly mixed by certain way, in frequency domain, both share fm broadcast channels.Concrete generation step is as follows:
I, obtain analog fm signal
The analog fm voice signal that audio-source obtains is expressed as m (t), f
cit is frequency modulated carrier.Modulating signal of frequency modulation x
fMbe expressed as
x
FM＝cos[α(t)] ①
Wherein α (t) is the phase function that following formula provides
2. f in formula
drepresent maximum frequency deviation, the order of this example
II, the analog fm voice signal time discretization that step I is obtained, obtain the analog fm modulation signal after corresponding digitlization.
Make the discrete-time signal of analog fm modulation signal be expressed as
X
FM＝(x
0，x
1，......x
m，)
X wherein
m=(x
0, m, x
1, m..., x
n-1, m) be the vector that in m signal frame, length is N.Here N is fast Fourier transform (FFT) length of OFDM in digital signal (OFDM) modulation, being about to analog fm modulated signal sequences after digitlization, to take the length of fast Fourier transform be unit segmentation, and this is the length of signal frame or OFDM frame.In the present embodiment, N value is any in 256,512,1024 and 2028.
Reproduction digital signal d in III, adjacent signals frame
m
In this method embodiment, in same frequency modulation channel, in analog fm modulation signal after the digitlization obtaining at transmission above-mentioned steps II, go back transmission of one line digital signal d (t), d (t) is audio broadcast signal and the data-signal after an other railway digital.Digital signal d (t) is through Channel Coding and Modulation, to resist better Noise and Interference.In the present embodiment, adopted modulating in OFDM.
Make D
m=(D
0, m, D
1, m..., D
n-1, m) represent the frequency domain digital signal after error correction and constellation mapping in m signal frame, through N point Fourier inversion (IFFT) the OFDM multi-carrier modulation of finishing dealing with, obtain D
mtime-domain digital signal, be expressed as d
m=(d
0, m, d
1, m..., d
n-1, m), d here
0, m, d
1, m..., d
n-1, msingle scalar, as x
mthe same, d
mrepresent the vector that in m signal frame, length is N.
Then, in adjacent signal frame, copy time-domain digital signal, in the 2m+1 signal frame of time domain, the time-domain digital signal d of 2m signal frame
mcopy once, in the 2m+3 signal frame of time domain, the time-domain digital signal d of 2m+2 signal frame
m+1copy once, as shown in Figure 8, obtain the time-domain digital signal that an adjacent signals frame repeats completely, every two adjacent signals frames form the time-domain digital signal of one group of Data duplication.
IV, analog and digital signal time domain are mixed, and obtain digital-to-analogue mixed signal.
The digital signal that analog fm modulation signal after the digitlization that the Step II of two adjacent signals frames is obtained and corresponding Step II I obtain is mixed in time domain, in 2m frame, and the analog fm modulation signal x after digitlization
2mdeduct corresponding digital signal d
m, obtain x
2m-d
m; In 2m+1 frame, the analog fm modulation signal x after digitlization
2m+1add corresponding d
m, obtain x
2m+1+ d
mthereby, obtaining the digitized simulation modulating signal of frequency modulation of transmission in same frequency modulation channel and the mixing of time-domain digital signal, this digital-to-analogue mixed signal is expressed as
S＝(s
0，s
1，s
2，s
3，......s
m)
=(x
0-d
0, x
1+ d
0, x
2-d
1, x
3+ d
1... ..x
2m-d
m, x
2m+1+ d
m... ..) 4. from formula, 4. can find out, at the upper time-domain digital signal d that repeats of adjacent signal frame (vector)
m, and with corresponding digitized analog fm modulation signal x
2m, x
2m-1add and subtract mutually, i.e. x
2m-d
mand x
2m+1+ d
m, the corresponding element in corresponding vector subtracts each other or is added.
The another kind of processing method that two signal time domains are mixed is, also can be by the order transposing that adds reducing of digitized analog fm modulation signal in above-mentioned adjacent signals frame and corresponding digital signal, and 2m frame two signals carry out sum operation, obtain x
2m+ d
m; And 2m+1 frame two signals carry out additive operation, obtain x
2m+1-d
m, digital-to-analogue mixed signal is expressed as in such cases
S＝(s
0，s
1，s
2，s
3，......s
m)
＝(x
0+d
0，x
1-d
0，x
2+d
1，x
3-d
1，.....x
2m+d
m，x
2m+1-d
m.....)④
In other words, the time domain hybrid mode of digitized analog fm signal and digital signal is as long as the digital signal symbol in adjacent two frames on the contrary in the digital-to-analogue mixed signal that guarantees to obtain, and reason is shown in separation description below.
V, digital-to-analogue mixed signal S, after digital-to-analogue conversion (DA) and up conversion, power amplification, are gone out by antenna transmission.
Above-mentioned analog fm modulation signal and digital signal are transmitted completely in same channel, frequency spectrum as shown in Figure 7, the frequency spectrum of analog fm modulation signal and digital signal is completely overlapping, and an identical frequency modulation channel is simultaneously for transportation simulator FM signal and digital signal.
Above-mentioned is the production method of in-band on-channel IBOC digital-analog audio frequency broadcast signal, and in IBOC digital audio broadcast system, the problem of core is exactly how receiving terminal separates analog-and digital-broadcast singal as far as possible neatly, reduces their phase mutual interference.
For the mixed in-band on-channel TDO-IBOC digital-analog audio frequency broadcast mixed signal repeatedly of this routine time domain, from above-mentioned formula 4., can see that two adjacent signal frames are
S
2m=x
2m-d
mand s
2m+1=x
2m+1+ d
m
Therefore, two adjacent signal frames are added, obtain
s
2m+s
2m+1＝x
2m+x
2m+1 ⑤
Therefrom eliminated digital signal d
m, further from s
2m+ s
2m+1=x
2m+ x
2m+1middle the analog fm signal x of two consecutive frames
2mand x
2m+1separate, obtain analog fm signal x
2mand x
2m+1, recover after treatment the analog fm signal of making a start and sending; Known x
2mand x
2m+1after, just can be from receiving digital-to-analogue mixed signal s
2mor s
2m+1middle recovery digital signal d
m.Thereby realize the thorough separation of digital and analogue signals.
The mixed repeatedly transmitting apparatus embodiment of the audio broadcast signal of in-band on-channel
The transmitting apparatus embodiment of this in-band on-channel digital-analog audio frequency broadcast as shown in Figure 9, comprises analog fm modulation module, digital signal modulated module, mixing module, digital-to-analogue (D/A) transducer, up-conversion module, power amplifier, antenna-feedback system and antenna.
Analog fm modulation module produces digitized analog fm modulation signal X
fM=(x
0, x
1... x
m), its output is by length N segmentation, and its input is connected to external audio source, and output is connected to mixing module; Digital audio modulation module produces and digital signal d
m, its input is connected to external audio source and data source, and output is connected to mixing module; Mixing module comprises a subtracter and adder, respectively the digital signal d repeating on adjacent signals frame
mwith corresponding digitized analog fm signal x
2m, x
2m-1add and subtract mutually, thus digitized analog fm modulation signal x
mwith digital signal d
mdigital-to-analogue mixed signal S=(the x mixing
0-d
0, x
1+ d
0... ..x
2m-d
m, x
2m+1+ d
m... ..), in the digital-to-analogue mixed signal of its output, digitized analog fm modulation signal and digital signal share a fm broadcast channel, and their frequency spectrum is completely overlapping.The output linking number weighted-voltage D/A converter of mixing module, becomes digital signal into analog signal s (t), is then connected to up-conversion module; Up-conversion module is moved radio frequency mixed signal from base band, and the output of up-conversion module is connected to high frequency power amplifier; Power amplifier outputs to antenna-feedback system after mixed signal is amplified, and through antenna transmission, goes out.
Described analog fm modulation module is analog fm sound modulation module, according to analog fm broadcast technology standard, the voice signal of input is modulated to FM signal, the technic relization scheme of analog fm modulation is a lot, analog fm sound modulation module contains direct digital synthesiser (Direct Digital Synthesis in the present embodiment, DDS), realize the modulation of analoging sound signal frequency modulation, modulation signal is converted to digital signal, frequency control word with this Digital Signals DDS, form the time-discrete sine wave that output frequency is controlled by analog signal, thereby obtain the modulating signal of frequency modulation X of time discrete (digitlization)
fM=(x
0, x
1...).
Described digital signal modulated module comprises precoding unit, multiplexed unit and digital modulator.Multi-channel analog or digital audio and video signals and data flow access precoding unit, precoding unit comprises A/D converter, preaccentuator, condensing encoder etc., after being become to digital transmission form with Data Stream Processing, various input audio frequency send into multiplexed unit, multiplexed unit is combined into a code stream by all data flow and the audio frequency that receive, then gives digital modulator.
Digital modulator comprises scrambler, channel encoder, constellation mapping unit, becomes frame unit, OFDM modulation processing unit (OFDM unit), time domain copied cells.The code stream access scrambler of input carries out randomization, realizes energy dissipation, and channel encoder carries out sending into constellation mapping unit after channel error correction coding.Meanwhile, synchronize data of system and control data, also send into constellation mapping unit through similar channel encoder respectively; The output of each constellation mapping unit is with pilot signal through becoming frame unit, OFDM modulation processing unit, and so far digital signal has completed Channel Coding and Modulation, has obtained time-domain digital signal d
m.Then access time domain copied cells, in the adjacent signals frame of two group, copy time-domain digital signal d
m, then give mixing module.
The Fourier transform length of the OFDM modulation processing unit that this example is described is any in 256,512,1024 and 2028.
In the present embodiment, the channel error correction coding of channel encoder has adopted serially concatenated error correcting code, and ISN adopts convolution code, and its female code is that code check is 1/2 convolution code, and generator polynomial is (171
otc, 131
otc), by forced (puncturing), process reliability enhanced deleting, obtain the convolution code of other code check, for example 2/3,3/4,5/6 and 7/8; Outer code adopts loe-density parity-check code (Low Density Parity Check, LDPC); Channel encoder is followed an interleaver, burst continuous error code discrete be random error, within dropping on error correcting capability scope.
In constellation mapping unit, the data that complete after error correction coding are carried out quaternary PSK modulation (QPSK) or/and the sign map of multiple qam digital modulation (mQAM).
In order to be convenient to realize carrier wave at receiving terminal, recover, various synchronous, regularly recover, phase noise is followed the tracks of, transmission mode identification, planisphere type identification, channel estimating and equilibrium etc., in the subcarrier of OFDM cells modulate, suitably insert pilot tone (pilot) signal, it is high that the power of the power ratio digital signal of pilot signal is wanted, so that receiving end is easy to detect pilot signal, pilot tone is divided in the continuous pilot of some subcarrier insert continually with by the scattered pilot of certain pattern dispersion insertion, that pilot tone adopts in the present embodiment is binary pseudo-random sequence (the Pseudo-Random Binary Sequence of certain length, PRBS).
The output of each constellation mapping unit is sent into into frame unit with pilot signal, in different business data centralizations such as this audio frequency and data flow, synchrodata, control data, pilot tones, get up to form signal frame, signal frame is sent into OFDM modulation and is processed (OFDM) unit, through inverse Fourier transform, and be placed on corresponding OFDM time frequency grid, be on the subcarrier of different time different frequency, obtain the frequency spectrum of digital signal.Then between each OFDM symbol of digital signal, insert protection interval (Guard Interval; GI); in the present embodiment; adopted Cyclic Prefix OFDM (Cyclic Prefix OFDM; CP-OFDM) mode; in GI, put into a Cyclic Prefix, become the period expansion of an OFDM symbol.
On the basis of Computer Simulation, each module of this transmitting apparatus with scene, can edit gate array (FPGA) and digital signal processor (DSP) is accomplished, and actual effect is good.
Above-described embodiment, is only the specific case that object of the present invention, technical scheme and beneficial effect are further described, and the present invention is not defined in this.All any modifications of making, be equal to replacement, improvement etc., within being all included in protection scope of the present invention within scope of disclosure of the present invention.
Claims (10)
1. the production method of in-band on-channel digital-analog audio frequency broadcast signal, is characterized in that comprising the following steps:
I, obtain simulated sound broadcast singal;
II, the simulated sound broadcast singal digitlization that step I is obtained, obtain the simulated sound broadcast singal after corresponding digitlization;
III, in adjacent signal frame reproduction digital signal;
This method, in same broadcasting channel, in the digital broadcast signal obtaining, is gone back transmission of one line digital signal in transmission above-mentioned steps II; This digital signal is audio broadcast signal and/or the conventional data-signal of an other railway digital; This digital signal, through Channel Coding and Modulation, copies time-domain digital signal in adjacent signal frame,, in 2m+1 signal frame, copies the time-domain digital signal d of 2m signal frame of an order
m, obtain the time-domain digital signal that a consecutive frame repeats completely, every two adjacent signals frames form the time-domain digital signal of one group of Data duplication;
Simulated sound broadcast singal after IV, digitlization and digital signal time domain are mixed, and obtain digital-to-analogue mixed signal;
The time-domain digital signal that simulated sound broadcast singal after the digitlization that the step II of adjacent signals frame is obtained and corresponding step III obtain mixes, in 2m frame, and the simulated sound broadcast singal x after digitlization
2mdeduct or add corresponding time-domain digital signal d
m, obtain x
2m– d
mor x
2m+ d
m; In 2m+1 frame, the simulated sound broadcast singal x after digitlization
2m+1add or deduct corresponding time-domain digital signal d
m, obtain x
2m+1+ d
mor x
2m+1-d
m, obtain the digital-to-analogue mixed signal S=(x transmitting in same broadcasting channel
0-d
0, x
1+ d
0... ..x
2m– d
m, x
2m+1+ d
m... ..), or S=(x
0+ d
0, x
1-d
0... ..x
2m+ d
m, x
2m+1-d
m... ..);
The digital-to-analogue mixed signal that V, step IV obtain is after digital-to-analogue conversion, up conversion and amplification, by antenna transmission.
2. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 1, is characterized in that:
Simulated sound broadcast singal described in step I is analog fm broadcast singal sound;
Broadcasting channel described in step III is fm broadcast channel.
3. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 1, is characterized in that,
The digitlization of the simulated sound broadcast singal described in step II is time-discrete.
4. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 1, is characterized in that,
The OFDM multi-carrier that is modulated to of the digital signal described in step III is modulated, or single-carrier modulated, or band spectrum modulation.
5. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 1, is characterized in that:
Digital signal described in step III be modulated to OFDM modulation.
6. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 5, is characterized in that:
The Fourier transform length of described OFDM modulation is any in 256,512,1024 and 2028.
7. the production method of in-band on-channel digital-analog audio frequency broadcast signal according to claim 1, is characterized in that:
Digital signal described in step III is also passed through channel error correction coding, and error correction coding has adopted serially concatenated error correcting code, and ISN adopts convolution code, and outer code adopts loe-density parity-check code; Or adopt cascaded code RS code+convolution code, or adopt cascaded code BCH+ loe-density parity-check code.
8. according to the transmitting apparatus of the in-band on-channel digital-analog audio frequency broadcast signal of the production method of the in-band on-channel digital-analog audio frequency broadcast signal described in any one in claim 1 to 7, it is characterized in that:
Comprise simulated sound modulation module, digital signal modulated module, mixing module, digital to analog converter, up-conversion module, power amplifier and antenna-feedback system,
The simulated sound modulation module that produces simulated sound broadcast singal by required frequency range, its input is connected to external audio source; The input that produces the digital signal modulated module of digital broadcast signal by the identical frequency range of simulated sound broadcast singal is connected to external audio source and/or data source; The input of mixing module is connected to the output of simulated sound modulation module and the output of digital signal modulated module, and the output of mixing module is connected to digital to analog converter; The output of digital to analog converter is connected to up-conversion module; The output of up-conversion module is connected to power amplifier; The output of power amplifier is sent into antenna-feedback system by antenna transmission;
Described digital signal modulated module comprises precoding unit, multiplexed unit and digital modulator; Multi-channel analog or digital audio and video signals and data flow access precoding unit, precoding unit comprises A/D converter, preaccentuator, condensing encoder, the output access multiplexer unit of precoding unit, multiplexed unit connects digital modulator again, and digital modulator comprises scrambler, channel encoder, constellation mapping unit, becomes frame unit, OFDM modulation processing unit, time domain copied cells; The code stream access scrambler of input, sends into constellation mapping unit after channel encoder, meanwhile, synchronize data of system and control data, also channel encoder is sent into constellation mapping unit respectively; The output of each constellation mapping unit through becoming frame unit, OFDM modulation processing unit, connects time domain copied cells with pilot signal, and time domain copied cells copies time-domain digital signal d in the adjacent signals frame of two group
m, the output of time domain copied cells is the output of digital signal modulated module, access mixing module;
Described mixing module comprises a subtracter and adder, respectively the digital signal d repeating on adjacent signals frame
mwith corresponding digitized simulated sound broadcast singal x
2m, x
2m-1add and subtract mutually the mixed signal S=(x of output
0-d
0, x
1+ d
0... ..x
2m– d
m, x
2m+1+ d
m... ..), or S=(x
0+ d
0, x
1-d
0... ..x
2m+ d
m, x
2m+1-d
m... ..), share a fm broadcast channel.
9. the transmitting apparatus of in-band on-channel digital-analog audio frequency broadcast signal according to claim 8, is characterized in that:
Described simulated sound modulation module contains Direct Digital Frequency Synthesizers.
10. the transmitting apparatus of in-band on-channel digital-analog audio frequency broadcast signal according to claim 8, is characterized in that:
The Fourier transform length of described OFDM modulation processing unit is any in 256,512,1024 and 2028.
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| CN103023849B (en) * | 2012-11-28 | 2015-05-13 | 中国传媒大学 | Psychoacoustic-model-based data transmission method of IBOC (in-band on-channel) system |
| CN102970269B (en) * | 2012-11-28 | 2015-05-13 | 中国传媒大学 | Dynamic data sending method for in-band on-channel (IBOC) system based on ear perception |
| CN102970087B (en) * | 2012-11-28 | 2014-10-29 | 苏州威士达信息科技有限公司 | Digital spectrum detection method for in-band on-channel (IBOC) system based on ear perception |
| CN103220251B (en) * | 2013-03-18 | 2015-10-14 | 深圳思凯微电子有限公司 | The in-band on-channel digital-analog audio frequency broadcast signal generating method improved |
| CN107666472B (en) | 2016-07-29 | 2020-08-11 | 微软技术许可有限责任公司 | Method and apparatus for hybrid digital-analog coding |
| CN107493107B (en) * | 2017-09-20 | 2019-06-28 | 深圳思凯微电子有限公司 | In-band on-channel self-interference removing method, device and computer readable storage medium |
| CN107947884A (en) * | 2017-11-17 | 2018-04-20 | 深圳思凯微电子有限公司 | A kind of digital-to-analogue broadcast singal combining device and method |
| CN108809318A (en) * | 2018-06-04 | 2018-11-13 | 成都中微达信科技有限公司 | A kind of digital-analogue converting device based on addition extension |
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| CN1193441A (en) * | 1995-09-22 | 1998-09-16 | 罗伯特·博施有限公司 | Method for the common transmission of digital and analogue modulated radio broad casting and/or television broadcasting signals |
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