CN114710385A - Digital-analog simulcast broadcast transmitting system - Google Patents
Digital-analog simulcast broadcast transmitting system Download PDFInfo
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- CN114710385A CN114710385A CN202210226372.0A CN202210226372A CN114710385A CN 114710385 A CN114710385 A CN 114710385A CN 202210226372 A CN202210226372 A CN 202210226372A CN 114710385 A CN114710385 A CN 114710385A
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- 230000003321 amplification Effects 0.000 claims abstract description 17
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 17
- 238000012545 processing Methods 0.000 claims abstract description 16
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 6
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 6
- 230000005669 field effect Effects 0.000 claims description 9
- 230000005540 biological transmission Effects 0.000 claims description 8
- 239000013078 crystal Substances 0.000 claims description 3
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- 238000010586 diagram Methods 0.000 description 7
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 3
- 230000005236 sound signal Effects 0.000 description 3
- 230000002051 biphasic effect Effects 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/20—Modulator circuits; Transmitter circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
- H04L25/40—Transmitting circuits; Receiving circuits
- H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
- H04L25/4902—Pulse width modulation; Pulse position modulation
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Abstract
The invention discloses a digital-analog simulcast broadcast transmitting system which comprises a digital signal processing module, an analog signal processing module and a power synthesis output module, wherein the digital signal processing module is used for generating a carrier signal, converting the input digital signal into a two-phase coding waveform, and then carrying out phase modulation on the carrier signal and the two-phase coding waveform to obtain a modulation signal. The analog signal processing module is used for generating a triangular wave signal, and then comparing the triangular wave signal with an input analog signal to obtain a width modulation pulse signal containing analog information. And the power synthesis output module is used for carrying out power amplification on the modulation signal and the width modulation pulse signal and transmitting the signal after power amplification. The invention can realize the mixing emission of the analog broadcast signals and the digital signals, effectively utilizes frequency spectrum resources, and realizes the transition from the analog broadcast transmitter to the digital transmitter under the conditions of low cost and stable operation so as to obtain better user experience.
Description
Technical Field
The invention relates to the technical field of broadcasting, in particular to a digital-analog simulcast broadcasting transmitting system.
Background
Since the development of broadcasting technology, the modulation modes of domestic all-solid-state medium wave transmitters are mainly divided into two categories, namely analog modulation and digital modulation. The ground analog sound broadcasting mode is to transmit audio signal to the broadcasting transmitter, and the audio signal is carried on the carrier signal by analog modulation mode, and then is transmitted to the antenna through the feeder after being amplified to transmit radio wave.
Digital modulation can overcome the above disadvantages of analog modulation, but if digital modulation is used instead, the consumption of spectrum resources will be greatly increased, and the modification cost is also high.
Disclosure of Invention
The embodiment of the invention provides a digital-analog simulcast broadcast transmitting system, which is used for solving the problems of analog modulation and digital modulation in the prior art.
In one aspect, an embodiment of the present invention provides a digital-analog simulcast broadcast transmitting system, including:
a digital signal processing module comprising: an exciter, a phase modulator and a preamplifier; the exciter is used for generating a carrier signal; the phase modulator is used for converting an input digital signal into a two-phase coding waveform, and then carrying out phase modulation on the carrier signal and the two-phase coding waveform to obtain a modulation signal; the preamplifier is used for amplifying the modulation signal;
the analog signal processing module comprises a pulse width modulator and a modulation driver; the pulse width modulator is used for generating a square wave signal, performing integration processing on the square wave signal to obtain a triangular wave signal, and then comparing the triangular wave signal with an input analog signal to obtain a width modulation pulse signal containing analog information; the modulation driver is used for amplifying the width modulation pulse signal;
the power synthesis output module comprises a power amplifier and an output network, wherein the power amplifier is used for performing power amplification on the amplified modulation signal and the amplified width modulation pulse signal; the output network is used for transmitting and transmitting the signals after power amplification.
The digital-analog simulcast broadcast transmitting system has the following advantages:
1. the method realizes the simulcasting with the digital signal while transmitting the analog bandwidth-modulated broadcast signal, and efficiently utilizes the existing frequency spectrum resources.
2. The phase modulator circuit structure is simple and stable, and unnecessary amplitude modulation can be effectively eliminated.
3. The whole system is reconstructed based on the traditional analog pulse width modulation broadcast transmitter, and has low cost and strong implementability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram illustrating a digital-analog simulcast broadcast transmitting system according to an embodiment of the present invention;
fig. 2 is a signal spectrum occupation diagram of a digital-analog simulcast broadcast transmission system according to an embodiment of the present invention;
fig. 3 is a process of generating a modulation signal of a phase modulator according to an embodiment of the present invention;
fig. 4 is a schematic circuit diagram of a portion of a phase modulator according to an embodiment of the present invention;
FIG. 5 is a schematic circuit diagram of a portion of a pulse width modulator according to an embodiment of the present invention;
fig. 6 is a schematic circuit diagram of a power amplifier according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1-6 are schematic diagrams illustrating components of a digital-analog simulcast broadcast transmitting system according to an embodiment of the present invention. The embodiment of the invention provides a digital-analog simulcast broadcast transmitting system, which comprises:
a digital signal processing module comprising: an exciter, a phase modulator and a preamplifier; the exciter is used for generating a carrier signal; the phase modulator is used for converting an input digital signal into a two-phase coding waveform, and then carrying out phase modulation on the carrier signal and the two-phase coding waveform to obtain a modulation signal; the preamplifier is used for amplifying the modulation signal;
the analog signal processing module comprises a pulse width modulator and a modulation driver; the pulse width modulator is used for generating a square wave signal, performing integration processing on the square wave signal to obtain a triangular wave signal, and then comparing the triangular wave signal with an input analog signal to obtain a width modulation pulse signal containing analog information; the modulation driver is used for amplifying the width modulation pulse signal;
the power synthesis output module comprises a power amplifier and an output network, wherein the power amplifier is used for performing power amplification on the amplified modulation signal and the amplified width modulation pulse signal; and the output network is used for transmitting and transmitting the signals after power amplification.
Illustratively, the transmission system in the present invention selects the additional spectrum in the 9KHz or 10KHz channel, as shown in fig. 2, the digital signal may be located in the adjacent channel to the analog signal. The bandwidth of the audio path (i.e., the path of the analog signal) in the transmission system is greater than the bandwidth required for conventional analog transmitter operation and is also 3.5 times the bandwidth required for the digital signal.
The data in the digital signal processing block is transmitted by a bi-phase encoded waveform (shaped waveform in fig. 3) which is phase modulated on a carrier signal by a phase modulator. As shown in fig. 3, for a bit "1" in the binary digital signal, the phase modulator will first generate a positive going pulse and then a negative going pulse. For a bit "0" in a binary digital signal, the phase modulator first generates a negative going pulse and then a positive going pulse. For each data bit to be transmitted, the phase modulator generates a pair of biphasic pulse signals, each pulse signal in the pair of biphasic pulse signals being spaced in time by tdAnd 2, then shaping the pulse signal by a square root raised cosine filter to obtain a biphase coding waveform. Square root raised cosine filter HT(f) The frequency response for the shaping process is:
with the above processing, the phase θ (t) of the bi-phase encoded waveform needs to be scaled to ensure a peak of ± 20 °, positive values indicating a phase lead and negative values indicating a phase lag. The phase modulator then selects the appropriate frequency w generated by the excitercAnd amplitude A0The phase modulator carries out phase modulation processing on the biphase coding waveform and the carrier signal to obtain a modulation signal. The modulation signal s (t) is given by:
When the phase modulator performs phase modulation, it can be performed independently of the carrier frequency. The modulation process of the phase modulator is implemented by an "I" balance adjuster (in-phase balance adjuster) and a "Q" balance adjuster (quadrature balance adjuster), based on the conventional approach. The modulation signal is multiplied by a linear analog multiplier to obtain a square term voltage, and the square term voltage is multiplied by the modulation signal again to obtain a cubic term voltage. The use of a "linear" analog multiplier ensures that no harmonic components are introduced while any amplitude modulation or carrier level variation at the input is preserved. But since the amplitude of the phase signal is not constant, a circuit as shown in fig. 4 is introduced in order to minimize the effect of unwanted amplitude modulation that may be caused in phase modulation. Driving the "I" balance regulator with a square term voltage can substantially eliminate unwanted amplitude modulation. In addition, the use of a cubic-term voltage-driven "Q" balanced modulator linearizes the phase modulation process and further eliminates spurious amplitude modulation. The waveform obtained after modulation is symmetrical about the nominal rest position of the carrier, the peak phase deviation is +/-20 degrees based on the nominal rest position, and the waveform processed by the phase modulator is sent to the power synthesis output module after being amplified by the preamplifier, as shown in fig. 5.
In an embodiment of the invention, the two balancing regulators are driven by two digital-to-analog converters, respectively, controlled by a microprocessor. The nature of the balance adjuster is an analog multiplier, since it is "linear", no harmonic components are introduced, while any amplitude modulation or carrier level variation at the input is preserved.
As shown in fig. 5, the circuit of the pwm is configured such that a MC14536 chip generates a square wave signal, which is output to the inverting terminal of an integrator circuit including a TL082 amplifier and its peripheral circuits via a pin 13, and a dc voltage is applied to the positive terminal of the integrator to output a triangular wave signal superimposed on the dc voltage. Then, the signal is compared with an audio signal (i.e. an analog signal) in an LM319 comparator, and a width modulated pulse signal containing audio information is output. The signal is input to the modulation driver for amplification and filtering, and then is input to the 2 and 3 input ports of the power amplifier, as shown in fig. 6.
In one possible embodiment, the exciter comprises a crystal oscillator, a frequency divider, and an amplification driver electrically connected in sequence.
Illustratively, the driver may use an external oscillator or signal source, or may use the crystal oscillator described above, using a jumper plug and a buffer driver amplifier.
In an embodiment of the invention, the exciter further generates a frequency sense output signal which is used to drive a frequency monitor and counter.
In a possible embodiment, the power amplifier uses a class d bridge circuit composed of a plurality of field effect transistors, wherein a part of the field effect transistors form one path to perform power amplification on the amplified modulation signal, and the remaining field effect transistors form the other path to perform power amplification on the amplified width-modulated pulse signal.
Illustratively, the power amplifier adopts a class D bridge circuit consisting of 8 IRF360 field effect transistors, and the circuit diagram is shown in FIG. 6. Each amplifier circuit uses 4 field effect transistors, the field effect transistors work in a switching state to carry out high-efficiency amplification, and the series resistor and the P6KE20CA voltage regulator tube are used for protecting the circuit. The output signal of the preamplifier is sent to the input port 1 of the power amplifier, the output signal of the modulation driver is sent to the input ports 2 and 3 of the power amplifier, the output signals of the two modules are subjected to final power amplification in the power combiner, and the output signals are sent to an output network for transmission through the output ports 4 and 5 of the transformer, so that digital-analog simulcasting is realized.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. A digital-to-analog simulcast broadcast transmission system, comprising:
a digital signal processing module comprising: an exciter, a phase modulator and a preamplifier; the exciter is used for generating a carrier signal; the phase modulator is used for converting an input digital signal into a two-phase coding waveform, and then carrying out phase modulation on the carrier signal and the two-phase coding waveform to obtain a modulation signal; the preamplifier is used for amplifying the modulation signal;
the analog signal processing module comprises a pulse width modulator and a modulation driver; the pulse width modulator is used for generating a square wave signal, performing integration processing on the square wave signal to obtain a triangular wave signal, and then comparing the triangular wave signal with an input analog signal to obtain a width modulation pulse signal containing analog information; the modulation driver is used for amplifying the width modulation pulse signal;
the power synthesis output module comprises a power amplifier and an output network, wherein the power amplifier is used for performing power amplification on the amplified modulation signal and the amplified width modulation pulse signal; and the output network is used for transmitting and transmitting the signals after power amplification.
2. The digital-to-analog simulcast broadcast transmission system of claim 1, wherein said exciter comprises a crystal oscillator, a frequency divider and an amplification driver electrically connected in sequence.
3. The digital-to-analog simulcast broadcast transmission system of claim 1, wherein said exciter is further adapted to generate a frequency detection output signal, said frequency detection output signal being adapted to drive a frequency monitor and a counter.
4. The digital-to-analog simulcast broadcast transmission system of claim 1, wherein the phase modulator first converts the digital signal into a bi-phase pulse signal and then converts the bi-phase pulse signal into the bi-phase encoded waveform using a square root raised cosine filter.
5. The digital-analog simulcast broadcast transmitting system of claim 1, wherein the phase modulator comprises an "I" balance adjuster and a "Q" balance adjuster, the "I" balance adjuster is driven by a square term voltage multiplied by the modulating signal, and the "Q" balance adjuster is driven by a cubic term voltage multiplied by the modulating signal.
6. The digital-analog simulcast broadcast transmitting system of claim 1, wherein the power amplifier employs a class-d bridge circuit composed of a plurality of field effect transistors, wherein a part of the field effect transistors constitutes one path to perform power amplification on the amplified modulation signal, and the remaining field effect transistors constitute the other path to perform power amplification on the amplified width modulated pulse signal.
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| CN202210226372.0A CN114710385A (en) | 2022-03-09 | 2022-03-09 | Digital-analog simulcast broadcast transmitting system |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB201314018D0 (en) * | 2013-08-06 | 2013-09-18 | Thales Holdings Uk Plc | Modulation unit and modulation method |
| CN105684301A (en) * | 2013-10-25 | 2016-06-15 | 三菱电机株式会社 | Power encoder and method for modulating data |
| CN216751799U (en) * | 2022-03-09 | 2022-06-14 | 陕西科技大学 | Digital-analog simulcast broadcast transmitting system |
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- 2022-03-09 CN CN202210226372.0A patent/CN114710385A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB201314018D0 (en) * | 2013-08-06 | 2013-09-18 | Thales Holdings Uk Plc | Modulation unit and modulation method |
| CN105684301A (en) * | 2013-10-25 | 2016-06-15 | 三菱电机株式会社 | Power encoder and method for modulating data |
| CN216751799U (en) * | 2022-03-09 | 2022-06-14 | 陕西科技大学 | Digital-analog simulcast broadcast transmitting system |
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