CN1674448A - Digital audio frequency processing method for analog amplitude modulation medium wave broadcasting transmitter digital improvement - Google Patents

Digital audio frequency processing method for analog amplitude modulation medium wave broadcasting transmitter digital improvement Download PDF

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CN1674448A
CN1674448A CN 200510004904 CN200510004904A CN1674448A CN 1674448 A CN1674448 A CN 1674448A CN 200510004904 CN200510004904 CN 200510004904 CN 200510004904 A CN200510004904 A CN 200510004904A CN 1674448 A CN1674448 A CN 1674448A
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transmitter
digital
signal
drm
audio
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CN100364302C (en
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吕锐
杨占昕
徐伟掌
侯亚辉
卢起斌
邓纶晖
曾志斌
周剑
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BEIJING BEIGUANGKE DIGITAL BROADCAST TELEVISION TECHNIQUE Co Ltd
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BEIJING BEIGUANGKE DIGITAL BROADCAST TELEVISION TECHNIQUE Co Ltd
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Abstract

The present invention relates to a digital audio-frequency processing method for making analog amplitude-modulated medium-frequency broadcast transmitter implement digitalization reconstruction. It is a method for implementing audio-frequency branch digital signal processing when the analog medium-frequency broadcast transmitter is remade into digital broadcast (DRM) transmitter. Said method can make intelligent gain regulation of power compensation for transmitting power of transmitter and power supply voltage, and can utilize software to implement flexible software radio design, so that said invention can obtain optimum modulation and power transmitting efficiency.

Description

The digital audio frequency processing method of analog AM medium wave broadcast transmitter digital improvement
Technical field
The present invention is a kind of when transforming the analog AM medium wave broadcast transmitter as digital broadcasting (DRM) transmitter, the implementation method of audio frequency branch road Digital Signal Processing particularly a kind ofly rises that sampling processing is obtained digital broadcasting (DRM) signal envelope composition and according to the transmitter power Control Parameter and the implementation method of the transmitter supply power voltage being carried out intelligent power compensation based on numeral.
Background technology
At present simulation medium wave (AM) broadcast transmitter that adopts be audio signal 1 by input after amplifier 3, in mixting circuit 5 with from the carrier signal 2 of radio frequency amplifier 4 outputs, carry out mixing, power amplification, launch 16 then, as shown in Figure 1.
Simulation medium wave (AM) transmitter realizes that the amplitude modulation double side band modulation function can be expressed as follows with mathematical formulae:
If audio input signal is: I ΩCos Ω t
The output signal that obtains after the modulation is:
i(t)＝(I T+I ΩcosΩt)cos(ωt+) {1}
I wherein TBe the carrier signal amplitude, ω is a carrier frequency.
Simulation medium wave transmitter signal processing generally is divided into Audio Signal Processing, flip-flop stack, and audio frequency+direct current signal amplifies, and radiofrequency signal is amplified, links such as mixing, power amplification.DC stacked formula { the I of 1} that is equivalent to T+ I ΩCos Ω t computing, mixing realizes by multiplication.
The baseband complex signal of digital broadcasting (DRM) channel coding modulator output can be expressed as:
Figure A20051000490400041
C wherein R, s, kThe qam symbol vector of representing required transmission, ψ R, s, kBe the one-period vector signal, according to the DRM standard, the DRM wireless signal of open circuit emission is
i ( t ) = Re { e jωt Σ r = 0 ∞ Σ s = 0 N S - 1 Σ k = K min K max c r , s , k ψ r , s , k ( t ) }
Wherein ω represents the radio frequency angular frequency, and then the mathematics formula of DRM modulation can be expressed as:
Promptly
i(t)＝I tcos(ωt)-Q tsin(ωt) {2}
i(t)＝A tcos(ωt+ t) {3}
Top formula (2) and formula (3) are equal to, and both can directly produce i (t) by digital RF excitation modulator, also can produce cos (ω t+ t) component.If adopt linear power amplifier to amplify, can produce low power i (t) signal by digital RF excitation modulator earlier, to after the linear power amplification of signal, launch then, but the efficiency of amplitude of this mode has only about 40%, for high-power transmitter, waste of electric energy is very serious, and this i (t) signal (shown in (3) formula) also is not suitable for adopting C, the D class amplification circuit that efficient is very high in the analog AM transmitter to carry out power amplification.
Though the radio frequency amplifying circuit of analog AM transmitter can not carry out undistorted amplification to i (t) signal, can be to cos (the ω t+ that does not comprise amplitude information t) component carries out undistorted amplification, this moment cos (ω t+ t) signal is a radiofrequency signal that only has phase information.
When utilizing analog AM transmitter modulation high power D RM signal, earlier i (t) signal is divided into envelope component A tWith high frequency phase modulation component cos (ω t+ t), A tComponent is delivered to transmitter audio frequency branch road and is carried out linear amplification, cos (ω t+ t) component is delivered to transmitter high frequency branch road, utilized C, the D class amplification circuit carries out high efficiency power amplification, then will be through the A that amplifies tAnd cos (ω t+ t) deliver in the mixting circuit of transmitter and carry out mixing, obtain powerful i (t) signal, realize the power amplification and the modulation of DRM signal.This mode both can make full use of the available circuit and the equipment of analog AM transmitter, had also realized power amplification efficiently and modulation simultaneously, had saved electric energy.The DRM of analog AM transmitter transforms mostly based on this thinking at present, and its block diagram as shown in Figure 2.Audio signal 1 enters DRM coded/modulated device 6, be encoded at DRM coded/modulated device 6 sound intermediate frequency signals/modulation treatment after, output digital baseband signal, and send into " asking mould-D/A switch (D/A) " 7 and digital RF excitation modulator 8 respectively.The road signal of sending into " asking mould-D/A switch (D/A) " 7 generates amplitude envelops, provides audio signal to transmitter, and the Audio Processing amplifier 2 of sending into transmitter amplifies, and finally enters mixting circuit 5; Enter the carrier wave of one tunnel treated generation phase modulated of digital RF excitation modulator 8, substitute the output of the carrier wave exciter 2 in the simulation amplitude modulated transmitter before transforming, send into radio frequency amplifier 4 and amplify, finally also enter mixting circuit 5.
Past, when transforming the analog AM medium wave transmitter as digital broadcasting (DRM) transmitter, the remodeling method that voice-grade channel is taked is the method for " full simulation transformation ", be about to Bezier (Bessel) filter by-pass on the voice-grade channel plate, to keep the DC level information of digital broadcasting (DRM) channel coding modulator, and the level and smooth oscillator of removal 72KHz, improve the bandwidth of whole audio frequency branch roads system, then the DRM signal behind the D/A switch is passed through former audio frequency bypass passage, thereby the audio frequency tributary signal of realizing the DRM signal is handled.Though this method can realize the signal processing of the audio frequency branch road of digital broadcasting (DRM) signal under the condition that does not additionally increase hardware, but the performance index of digital broadcasting (DRM) signal by this kind method emission are not ideal enough, reason is that this method is on signal processing, carry out D/A switch (D/A) earlier, and then carried out mould/number (A/D) conversion.These two links, all introduced certain quantization error, can not bring into play the advantage of existing digital modulation treatment in the existing simulation medium wave transmitter, and make the audio frequency tributary signal introduce some noise contributions, on the other hand, because the envelope of DRM signal itself contains useful high fdrequency component, if simply carry out low-pass filtering, introduce the additional high noise contribution though can reduce, the envelope itself that also can suppress the DRM signal simultaneously contains useful high fdrequency component, makes the DRM signal amplitude distortion occur.These two problems are inherent shortcomings of " full simulation transformation " method, are difficult to technically solve, and therefore make the performance index (as signal to noise ratio) of whole system be difficult to improve.
Summary of the invention
The present invention is a kind of medium wave broadcast transmitter of will simulating when transforming digital broadcasting (DRM) transmitter as, the implementation method of audio frequency branch road Digital Signal Processing.This method adopts based on rising sampling processing and obtains digital signal envelope composition, and carries out intelligent compensation according to transmitter power Control Parameter and supply power voltage, to obtain best modulation and power emission efficient.
The method that the present invention takes is:
A) the digital serial audio frequency symbols streams of DRM modulating coder output is carried out serial/parallel conversion;
B) rise sampling;
C) separate the envelope composition;
D) carry out power control;
E) transmitter voltage compensation;
F) output sampling rate conversion;
H) export the Audio Processing amplifier to.
Above step also is a running software flow process of the present invention.Hardware signal processing procedure of the present invention is:
Original analogue audio frequency branch input signal is replaced with numeral (DRM) signal, and adopt digital signal processing method to substitute the original analog signal processing method.At first the sampled value of supply power voltage is carried out mould/number conversion, and be combined as binary signal with power control signal (binary-coded decimal) and be input in the floating type digital signal processing chip (DSP) as parameter, numeral (DRM) signal that will receive by AES (audio engineer association interface) interface simultaneously, in-phase signal I after promptly modulating, orthogonal signalling Q, converting serial digital signal to sends in this digital signal processor (DSP), the FIR (finite impulse response) that carries out 32 rank rises sampling processing and asks modular arithmetic, and according to the fluctuation variation of transmitter supply power voltage signal amplitude is done the adjustment relevant with power control and handle, output to programmable logic device (FPGA) then, programmable logic device (FPGA) obtains the sampled signal of radio frequency by comparator, to carry out the code check conversion from numeral (DRM) envelope signal of digital signal processor (DSP) input, output to the audio frequency amplifier of transmitter at last by buffer, provide data to keep simultaneously, reset signal provides relevant control shows signal for the control display panel.
The beneficial effect that the present invention produces is: low cost, can realize directly obtaining the purpose of envelope information of the high-speeld code-flow of input with the less hardware expense; Adopt the design concept of software radio, can not change hardware designs, just can realize that the envelope information of the symbol data streams of different rates input is extracted, be easy to upgrading and expanded application.Because the DRM Signal Processing is all finished at numeric field, so, can access very high performance index, meet the technical standard requirement of DRM fully.
Description of drawings
Below in conjunction with drawings and Examples the present invention is done a detailed explanation.
Fig. 1 is the theory diagram of simulation medium wave broadcast transmitter;
Fig. 2 will be for will simulate the theory diagram that medium wave broadcast transmitter is adapted as numeral (DRM) broadcast transmitter;
Fig. 3 is theory diagram of the present invention and running software flow chart;
Fig. 4 is a hardware block diagram of the present invention.
Among the figure: audio signal 1, carrier generator 2, Audio Processing amplifier 3, radio frequency amplifier 4, mixting circuit 5, DRM modulating coder 6, obtain envelope 7, digital RF excitation modulator 8, serial/parallel conversion 9, rise sampling 10, separate envelope composition 11, transmitter voltage compensation 12, transmitter power control 13, output signal sample rate conversion 14, AES interface (audio engineer association interface) 15, digital signal processor (DSP) 16, D/A (A/D) conversion 17, programmable logic device (FPGA) 18, buffer 19, comparator 20, power control signal (BDC sign indicating number), voltage sample and power control signal 22, voltage sampling signal 23, radiofrequency signal 24, radio frequency sampling signal 25, control shows 26, and data keep, reset signal 27, envelope signal 28.
Embodiment:
Figure 3 shows that theory diagram of the present invention.Digital serial audio frequency symbols streams to 6 outputs of DRM encoder is carried out serial/parallel conversion 9 earlier, then carry out numeral and rise sampling processing 10, obtain the envelope composition 11 of DRM signal, afterwards the transmitter supply power voltage is carried out power back-off 12, carry out output power of transmitter control 13 then, output signal is carried out sample rate conversion 14 and is exported audio frequency amplifier 3 to.
The digital audio processing plate hardware and the software that is embedded into wherein that comprise a core assembly sheet by use, but these steps of specific implementation.Employed chip is: the high performance digital signal processor of floating type (DSP) chip, and field programmable logic device (FPGA) is the chipset on basis.
Hardware of the present invention moves as shown in Figure 4: the sampled signal 23 of supply power voltage is carried out mould/number (A/D) conversion, and be combined as binary signal with power control signal (binary-coded decimal) 21 and be input in the floating type Digital Signal Processing (DSP) as parameter, simultaneously will be by AES interface (audio engineer association interface) the 15 DRM signals that receive, it is modulated I, Q quadrature two paths of signals converts serial digital signal to and is input in the digital signal processor (DSP) 16, the FIR (finite impulse response) that carries out 32 rank rises sampling processing and asks modular arithmetic, and according to the fluctuation variation of transmitter supply power voltage signal amplitude is done the adjustment relevant with power control and handle, output to programmable logic device (FPGA) 18 then, programmable logic device (FPGA) 18 obtains the sampled signal 25 of radio frequency by comparator, to carry out the code check conversion from numeral (DRM) envelope signal of digital signal processor (DSP) 16 inputs, output to audio frequency amplifier 3 by buffer 19 at last, giving simultaneously provides data to keep, reset signal 27 shows that 26 provide relevant control shows signal for control.

Claims (3)

1. implementation method that the analog AM medium wave broadcast transmitter is transformed into the audio frequency branch road Digital Signal Processing of digital broadcasting (DRM) transmitter, be particularly related to and a kind ofly rise sampling processing based on numeral and obtain digital broadcasting (DRM) signal envelope composition and, it is characterized in that described method comprises according to transmitter power Control Parameter and implementation method that the transmitter supply power voltage is carried out the intelligent power compensation:
A) the digital serial audio frequency symbols streams of DRM modulating coder output is carried out serial/parallel conversion (9)
B) rise sampling (10);
C) separate envelope composition (11);
D) carry out power control (13);
E) transmitter voltage compensation (12);
F) output sampling rate conversion (14);
H) export Audio Processing amplifier (3) to.
2. digital audio processing plate of realizing the described method of claim 1, it is characterized in that, described digital audio processing plate comprises: AES interface (audio engineer association interface) (15), digital signal processor (DSP) (16), D/A (A/D) transducer (17), programmable logic device (FPGA) (18), buffer (19), comparator (20).
3. digital audio processing plate according to claim 2, the software that is embedded into chipset is wherein arranged, it is characterized in that, described software comprises: serial/parallel conversion (9), rise sampling (10), separate envelope composition (11), transmitter voltage compensation (12), transmitter power control (13), output signal sample rate conversion (14).
CNB2005100049042A 2005-01-28 2005-01-28 Digital audio frequency processing method for analog amplitude modulation medium wave broadcasting transmitter digital improvement Expired - Fee Related CN100364302C (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103166651A (en) * 2011-11-10 2013-06-19 北京北广科技股份有限公司 Power control device of transmitter digital modulator
CN103634254A (en) * 2012-08-23 2014-03-12 华东师范大学 Indirect modulation and demodulation data transmission device and transmission method thereof
CN105743825A (en) * 2014-12-11 2016-07-06 北京同方吉兆科技有限公司 Digital predistortion system for digital-analog mixed broadcasting type digital audio broadcasting transmitter
CN105743517A (en) * 2014-12-11 2016-07-06 北京同方吉兆科技有限公司 Digital-analog mixed broadcasting structure for digital-analog mixed broadcasting type digital audio broadcasting transmitter
CN111066264A (en) * 2017-08-24 2020-04-24 谷歌有限责任公司 Dynamic calibration for audio data transfer

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6128350A (en) * 1999-08-24 2000-10-03 Usa Digital Radio, Inc. Method and apparatus for reducing peak to average power ratio in digital broadcasting systems
KR100859868B1 (en) * 2002-05-30 2008-09-24 삼성전자주식회사 Carrier Recovery Apparatus of digital broadcasting receiver using the 2 pilot signal
CN1152493C (en) * 2002-06-20 2004-06-02 上海交通大学 Method for inhibiting peak-to-average ratio in orthogonal frequency division complex communication system
US20040223553A1 (en) * 2003-02-07 2004-11-11 Kumar Derek D. Method and system for wireless audio transmission using low bit-weight words

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103166651A (en) * 2011-11-10 2013-06-19 北京北广科技股份有限公司 Power control device of transmitter digital modulator
CN103166651B (en) * 2011-11-10 2015-02-25 北京北广科技股份有限公司 Power control device of transmitter digital modulator
CN103634254A (en) * 2012-08-23 2014-03-12 华东师范大学 Indirect modulation and demodulation data transmission device and transmission method thereof
CN105743825A (en) * 2014-12-11 2016-07-06 北京同方吉兆科技有限公司 Digital predistortion system for digital-analog mixed broadcasting type digital audio broadcasting transmitter
CN105743517A (en) * 2014-12-11 2016-07-06 北京同方吉兆科技有限公司 Digital-analog mixed broadcasting structure for digital-analog mixed broadcasting type digital audio broadcasting transmitter
CN111066264A (en) * 2017-08-24 2020-04-24 谷歌有限责任公司 Dynamic calibration for audio data transfer
CN111066264B (en) * 2017-08-24 2022-01-25 谷歌有限责任公司 Dynamic calibration for audio data transfer

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Assignee: Harbin Broadcast Equipment Co., Ltd.

Assignor: Beijing Beiguangke Digital Broadcast Television Technique Co., Ltd.

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Denomination of invention: Digital audio frequency processing method for analog amplitude modulation medium wave broadcasting transmitter digital improvement

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