High-efficiency Dual-frequency Homologous Frequency-modulated Radio Broadcasting Modulation and Transmission System

Abstract

High-efficiency dual-frequency homologous frequency-modulated radio broadcast modulation and transmission system, which relates to the field of radio and television technology and solves the problem of low power efficiency of existing multi-program homologous transmitters. The system includes a frequency modulator and a power amplifier circuit. The power amplifier circuit includes an amplitude modulator and a carrier amplifier. The frequency modulator includes a processor, a V oscillator, a U oscillator, a pulse generator, a pulse modulator, an inverter, a phase detector, and a data selector. The power amplification circuit of the present invention not only has the function of signal amplification, but also participates in the frequency synthesis of frequency-modulated programs in the form of high-power amplitude modulation, which is a new technical route. Therefore, the power amplifier circuit can use class C or higher class D amplifiers with higher power efficiency, and the output high-power program signal can be directly transmitted.

Description

Technical Field

[0001] The present invention relates to the technical field of radio and television, and particularly to a high-power frequency modulation radio dual-frequency and single-source transmitter with relatively high power utilization efficiency. Background Art

[0002] China's national standard for frequency modulation radio stipulates that frequency modulation radio programs use frequency modulation, with a frequency range from 87 MHz to 108 MHz and a maximum frequency deviation of 75 KHz; for traditional frequency modulation radio transmitters, each broadcast program needs to occupy a radio frequency carrier channel; because the currently widely used frequency modulation radio transmitters are single-channel transmitters, if multiple programs need to be transmitted simultaneously, multiple single-frequency transmitters must be used, and each program is modulated into a radio frequency signal of a different channel and then transmitted; in order to reduce the number of devices, Patent 201520223933.7 introduces a multi-channel signal modulator that can broadcast multiple digital TV programs simultaneously with one set of circuits; there is also Patent 201710355630.4 that introduces a frequency modulation radio multi-channel digital modulation system, and the authorized Patent 202110434764.1 that introduces a multi-channel stereo frequency modulation radio modulator, all of which can modulate and broadcast multiple frequency modulation radio programs simultaneously with one set of circuit devices; this type of transmitter that can transmit multiple channel program signals simultaneously with one transmitter is called a single-source transmitter and is currently in the trial stage; the power amplifier circuits of traditional single-frequency frequency modulation radio transmitters generally use class C amplifiers, and the power efficiency can reach up to 70%; while for the transmitters designed using the above several existing technologies, class A or class AB power amplifier circuits must be used, and the efficiency is difficult to exceed 50%; that is to say, although the existing single-source transmitters optimize the equipment utilization, they also significantly reduce the power consumption efficiency and are not suitable for high-power program coverage scenarios.

[0003] Currently, the core amplification element of a power amplifier is a power amplifier tube. According to the different states of the operating point of the power amplifier tube being in class A, class B, class C, and class D, the corresponding designed amplifiers are also called class A amplifiers, class B amplifiers, class C amplifiers, and class D amplifiers; sorted by signal distortion, class A has the least distortion, class B has a little more distortion, class C has even more distortion, and class D has the most distortion; sorted by power efficiency, class A has the lowest efficiency, class B has a higher efficiency, class C has a relatively high efficiency, and class D has the highest efficiency; in high-power scenarios, power efficiency is relatively important, and class C or class D amplifiers with relatively high efficiency should be used as much as possible;

[0004] Because the amplitude of the traditional single - frequency FM radio program signal is constant, the requirement for the distortion degree of the transmitter power amplifier circuit is not high, and class - C or even class - D amplifiers with larger distortion can be used. However, in the technical solutions described in several patents in the background art, it is a technical solution of superposition of multi - program signals. After superposition, the amplitude of the signal changes rapidly and is not constant. At this time, the power amplifier circuit must have good distortion index and can only use class - A or class - AB amplifiers. Therefore, the power supply efficiency of existing single - source transmitters is very low and is not suitable for high - power program coverage occasions. Summary of the Invention

[0005] The present invention provides an efficient dual - frequency single - source FM radio modulation and transmission system to solve the problem of low power supply efficiency of existing multi - program single - source transmitters.

[0006] The efficient dual - frequency single - source FM radio modulation and transmission system includes a frequency modulator and a power amplifier circuit. The power amplifier circuit includes an amplitude modulator and a carrier amplifier.

[0007] The frequency modulator includes a processor, a V oscillator, a U oscillator, a pulse generator, a pulse modulator, an inverter, a phase detector, and a data selector.

[0008] The output end of the input terminal of Program A is electrically connected to the first input terminal of the processor.

[0009] The output end of the input terminal of Program B is electrically connected to the second input terminal of the processor.

[0010] The first output end of the processor is electrically connected to the input end of the V oscillator.

[0011] The second output end of the processor is electrically connected to the input end of the U oscillator.

[0012] The output end of the V oscillator is respectively electrically connected to the second input terminal of the pulse modulator and the input terminal of the phase detector.

[0013] The output end of the U oscillator is respectively electrically connected to the input end of the inverter and the second input terminal of the data selector.

[0014] The output end of the pulse generator is electrically connected to the first input terminal of the pulse modulator.

[0015] The output end of the pulse modulator is electrically connected to the input end of the amplitude modulator.

[0016] The output end of the inverter is electrically connected to the first input terminal of the data selector.

[0017] The output end of the phase detector is electrically connected to the SEL input terminal of the data selector.

[0018] The output end of the data selector is electrically connected to the IN input end of the carrier amplifier;

[0019] The OUT output end of the carrier amplifier is electrically connected to the signal output end;

[0020] Program A and Program B respectively enter the frequency modulator through the output ends of the input ends of Program A and the input ends of Program B; the center frequencies of the channels where the transmission carriers of Program A and Program B are located are f1 and f2 respectively, and the center frequencies f1 and f2 are stored in the processor; after being modulated by the processor, the carrier is transmitted to form a superimposed signal which is output from the output end and finally connected to the transmitting antenna to realize program broadcasting.

[0021] The beneficial effects of the present invention:

[0022] In order to prevent users from hearing mixed radio programs, the radio and television industry standard "GY / T196-2003 Technical Regulations for FM Radio Coverage Networks" stipulates that the frequency interval of the same-station FM radio is generally not less than 1 MHz (when the number of the same-station frequencies is 6 or more, the frequency interval is not less than 800 kHz); however, in actual situations, because the FM radio channel resources in many large cities in China are tense, so while reducing the transmission power, the frequency interval is extremely compressed to accommodate more radio station programs; however, the compression limit cannot be less than 500 kHz, otherwise there will be mixed-channel interference phenomena; and by using the homologous transmitter designed by the present invention, it is possible to achieve equal-intensity transmission of homologous signals. Even if the frequency interval between the two programs is compressed to 300 kHz, it is still possible to ensure normal broadcasting without mixed channels.

[0023] The transmission system described in the present invention is different from the power amplification circuit in the existing homologous transmitter which only has the single function of signal amplification. The power amplification circuit of the present invention not only has the function of signal amplification, but also participates in the frequency synthesis of the FM program in the form of high-power amplitude modulation, which is a new technical route; therefore, the power amplifier circuit can use class C or higher class D amplifiers with higher power efficiency, and the output high-power program signal can be directly transmitted.

[0024] In the transmission system described in the present invention, the amplitude modulator uses a class C or class D amplification circuit to solve the above power efficiency problem. Brief Description of the Drawings

[0025] Figure 1 It is the structural block diagram of the high-efficiency dual-frequency homologous FM radio modulation and transmission system described in the present invention;

[0026] Figure 2 It is the waveform diagram of the V signal and the Y signal. Detailed Embodiments

[0027] Combined Figure 1 andFigure 2 This embodiment describes a high-efficiency dual-frequency and single-source frequency-modulated broadcast modulation and transmission system, which includes a frequency modulator and a power amplifier circuit. The power amplifier circuit includes an amplitude modulator and a carrier amplifier 12; the amplitude modulator includes an amplitude modulation amplifier 9, a low-pass filter 13, and a high-power power supply 14;

[0028] The frequency modulator includes a processor 3, a V oscillator 4, a U oscillator 5, a pulse generator 6, a pulse modulator 7, an inverter 8, a phase detector 10, and a data selector 11;

[0029] The output end of the program A input terminal 1 is electrically connected to the 1 input end of the processor 3;

[0030] The output end of the program B input terminal 2 is electrically connected to the 2 input end of the processor 3;

[0031] The 3 output end of the processor 3 is electrically connected to the 1 input end of the V oscillator 4;

[0032] The 4 output end of the processor 3 is electrically connected to the 1 input end of the U oscillator 5;

[0033] The 2 output end of the V oscillator 4 is respectively electrically connected to the 3 input end of the pulse modulator 7 and the 1 input end of the phase detector 10;

[0034] The 2 output end of the U oscillator 5 is respectively electrically connected to the 1 input end of the inverter 8 and the 2 input end of the data selector 11;

[0035] The output end of the pulse generator 6 is electrically connected to the 1 input end of the pulse modulator 7;

[0036] The 2 output end of the pulse modulator 7 is electrically connected to the IN input end of the amplitude modulation amplifier 9;

[0037] The 2 output end of the inverter 8 is electrically connected to the 1 input end of the data selector 11;

[0038] The 2 output end of the phase detector 10 is electrically connected to the SEL input end of the data selector 11;

[0039] The 3 output end of the data selector 11 is electrically connected to the IN input end of the carrier amplifier 12;

[0040] The OUT output end of the amplitude modulation amplifier 9 is electrically connected to the 1 input end of the low-pass filter 13;

[0041] The output end of the high-power power supply 14 is electrically connected to the POW power input end of the amplitude modulation amplifier 9;

[0042] The 2 output end of the low-pass filter is electrically connected to the POW power input end of the carrier amplifier 12;

[0043] The OUT output terminal of the carrier amplifier 12 is electrically connected to the signal output terminal 15;

[0044] Both sets of broadcast programs are digital program data, entering the system from the program A input terminal 1 and the program B input terminal 2 respectively; the center frequencies of the channels where the carriers of these two sets of programs are transmitted are f1 and f2 respectively, which have been stored in the processor 3; after modulation, the carriers of the two sets of broadcast programs will be transmitted to the signal output terminal 15 and have been superimposed together, and then can be connected to the transmitting antenna to realize program broadcasting; because the two carrier signals output at the signal output terminal 15 are homologous signals and can always maintain the same output intensity, so even if the frequency interval between f1 and f2 is compressed to 300 kHz, it can still ensure normal reception without mixing stations with an ordinary radio.

[0045] The homologous transmitter introduced in the prior art modulates several programs to several intermediate frequency signal frequencies first, and then secondarily modulates the intermediate frequency signals to another high frequency signal frequency. The frequency of the program signal actually transmitted is equal to the high frequency signal frequency plus or minus the intermediate frequency signal frequency; while a new dual-frequency modulation scheme is adopted in the transmission system described in this embodiment;

[0046] The data of the two sets of broadcast programs of program A and program B are input into the system. If the instantaneous frequencies of the FM signals corresponding to these two sets of programs are fa and fb respectively, then the frequency modulator must generate a U signal with a frequency of fu and an X signal with a frequency of fx. Both signals are square wave signals, and fu is equal to the average value of fa and fb;

[0047]

[0048] Inside the modulator, an X signal is generated by modulating another signal with a frequency of fx with a sine wave V signal pulse with a frequency of fv; fv is equal to the absolute value of the difference between fa and fb divided by 2;

[0049]

[0050] fu, fv, and fx are all generated by the frequency modulator according to the instantaneous voltage values of the program sound signals input by the transmitter, and change with the signal data, which is realized by the frequency modulator module;

[0051] In this embodiment, the input signal of the frequency modulator is the N-bit binary sound voltage values of two programs, and the sound program data is continuously input and constantly changing. If the input is an analog sound signal, it needs to be converted into a digital quantity by analog-to-digital conversion and then sent to the frequency modulator. The two FM radio programs are broadcast at the carrier center frequencies of f1 and f2 respectively. The instantaneous values of the sound voltage signals of the two programs at a certain moment are represented by variable A and variable B respectively. Whenever the input A or B changes, the frequency modulator has to calculate the carrier instantaneous frequencies fa and fb of the two programs according to the values of the input voltages A and B using the following formula, with the unit of megahertz;

[0052] fa = A * 0.15 / N + f1 - 0.075

[0053] fb = B * 0.15 / N + f2 - 0.075

[0054] After that, calculate the frequencies of the U signal and the V signal;

[0055] The frequency of the U signal output by the frequency modulator fu = (fa + fb) / 2

[0056] The frequency of the V signal inside the frequency modulator fv = (|fa - fb|) / 2

[0057] The X signal output by the frequency modulator is a signal generated by pulse modulation of the V signal. The specific modulation method can be PWM, or PFM or PSM, etc. As long as the statistical average value of the duty cycle of the X signal is proportional to the voltage value of the V signal, any modulation method can be used. The frequency of the X signal must be more than four times higher than the frequency of the V signal. Because increasing the frequency of the X signal is beneficial to improving the harmonic output index of the system, but it is mainly limited by the high-frequency performance parameters of the power amplifier tube components in the amplitude modulation amplifier 9, and the frequency cannot be too high. Therefore, the frequency of the X signal can only be increased as much as possible under the condition that the performance of the amplitude modulation amplifier 9 permits. The pulse generator 6 generates square wave pulses and sends them to the signal input end of the pulse modulator 7. The V signal is sent to the modulation input end of the pulse modulator 7 to modulate the square wave generated by the pulse generator 6 into the X signal;

[0058] The frequency modulator operates under the control of processor 3. Processor 3 receives data from program A input terminal 1 and program B input terminal 2, calculates the frequency fu of the U signal and the frequency fv of the V signal, controls the V oscillator 4 to generate the V signal, and also controls the U oscillator 5 to generate a signal with a frequency equal to fu. The data selector 11 selects one of the in-phase or anti-phase signals to become the U signal. Whenever the data content of the input program A or B changes, processor 3 needs to calculate a new frequency value of the U signal to set the U oscillator to work, and calculate a new frequency value of the V signal to set the V oscillator to work. When the U oscillator receives the setting from processor 3, it can directly change the output to a new frequency. When the V oscillator receives the setting from processor 3, it starts to output a new frequency from the voltage value and phase of the sine waveform at that time, so as to ensure that while immediately changing the output to a new frequency, the continuity of the output sine signal waveform can be maintained.

[0059] The phase of the U signal output by the frequency modulator needs to change synchronously with the polarity change of the V signal. Whenever the V signal enters the negative half cycle from the positive half cycle, the U signal needs to be inverted by 180 degrees. If the V signal returns from the negative half cycle to the positive half cycle, the U signal also returns from the inverted phase to the normal phase. That is to say, the U signal is a signal generated by binary phase shift keying modulation of the V signal. The specific method is that the phase detector 10 detects the phase of the V signal. When the V signal is in the positive half cycle, the data selector 11 selects the signal output by the U oscillator 5 as the U signal and outputs it to the carrier amplifier 12. When the V signal is in the negative half cycle, the data selector 11 selects the inverted signal output by the U oscillator 5 as the U signal and outputs it to the carrier amplifier 12.

[0060] The signals output by the homomorphic transmitter in the prior art are multiple frequency signals superimposed together. Only one power amplifier circuit can be used to amplify all frequency signals simultaneously, and it is required that the output signal of the power amplifier has the same frequency as the input signal. Since the amplitude of the superimposed signal is always changing, class A or class AB power amplifier circuits must be used. Otherwise, distortion of the amplitude of the superimposed signal will cause a large number of harmonics to be generated, which cannot meet the needs of normal broadcasting.

[0061] The power amplifier circuit of this system mainly consists of two major modules. One module is the carrier amplifier, and the other module is the amplitude modulator. The U signal input to the power amplifier is amplitude-modulated and then output as the superposition of two program transmission signals. The difference in working performance from the traditional power amplifier is that the frequency of the input signal U of the power amplifier circuit of this system is not equal to the frequency of the output signal.

[0062] The U signal is generated by a frequency modulator and delivered to the input end of a radio frequency amplifier; the frequency fu of the U signal is equal to the average value of the two program carrier frequencies, not equal to any of them, and is related to the audio data input for both sets of programs; in order to obtain a higher power efficiency in this system, it is required that the operating point of the power amplifier tube in the radio frequency amplifier be in class C or class D.

[0063] In this embodiment, the amplitude modulator amplifies and filters the X signal from the frequency modulator to generate a Y signal; the waveform of the Y signal is a half-cycle sine wave, only the positive polarity part among the sine waveforms, and the negative polarity part among the sine waveforms is made into the positive polarity by reversing the polarity; the frequency of the Y signal is twice the frequency of the V signal. Figure 2 The waveform of the Y signal is shown corresponding to the V signal.

[0064] The X signal of the frequency modulator is a small signal, and its load capacity is not sufficient to be used as the power supply for the carrier amplifier; the amplitude modulation amplifier 9 is a class C or class D amplifier, which can obtain energy from the high-power power supply 14, amplify the intensity of the X signal to the extent that it can be used as a power supply to supply power to the carrier amplifier 12, and has a high power efficiency.

[0065] From Figure 2 Looking at the voltage waveform of the intermediate signal, in the positive half-cycle of the V signal, the voltage phase of the Y signal is the same as that of the V signal; in the negative half-cycle of the V signal, the voltage phase of the Y signal is opposite to that of the V signal; the signal Y will be delayed with respect to the signal V, and the main reason for the delay is the existence of the low-pass filter 13. The delay time value t is determined by the design parameters of the low-pass filter 13. Therefore, when the program input data changes, the frequency fv of the signal V changes immediately, while the frequency fu of the signal U needs to be deliberately delayed before changing. The specific delay time must be consistent with the delay of the low-pass filter; the processor 3 can be used to control the frequency modulator to first change fv, and then change fu after the delay, indirectly realizing this deliberately delayed function.

[0066] The U signal generated by the frequency modulator is input to the input end of the carrier amplifier 12. The carrier amplifier 12 is also a class C or class D amplifier, uses the Y signal as the input power supply, the output signal frequency is equal to fu, and the output amplitude is proportional to the voltage value of the Y signal. While achieving amplitude modulation of the radio frequency signal, it has a high power efficiency.

[0067] The amplitude of the Y signal output by the amplitude modulation amplifier 9 does not affect the frequency of the transmitted program, but only affects the power of the transmitted program; since the amplitude modulation amplifier 9 is a class C or class D amplifier and the amplitude of the input signal is proportional to the output voltage of the high-power power supply 14, the transmitted power can be controlled by controlling the output voltage of the high-power power supply 14, affecting the coverage area of the program; however, in any case, the two programs transmitted and broadcast are of the same source and equal intensity, and the center frequency interval between the two program channels can be compressed to 300 kHz for normal broadcast without mixing channels.

Claims

1. An efficient dual-frequency and same-source frequency-modulated radio broadcast modulation and transmission system, characterized in that: The system includes a frequency modulator and a power amplifier circuit, and the power amplifier circuit includes an amplitude modulator and a carrier amplifier; The frequency modulator includes a processor, a V oscillator, a U oscillator, a pulse generator, a pulse modulator, an inverter, a phase detector, and a data selector; The output end of the program A input terminal is electrically connected to the first input end of the processor; The output end of the program B input terminal is electrically connected to the second input end of the processor; The first output end of the processor is electrically connected to the input end of the V oscillator; The second output end of the processor is electrically connected to the input end of the U oscillator; The output end of the V oscillator is respectively electrically connected to the second input end of the pulse modulator and the input end of the phase detector; The output end of the U oscillator is respectively electrically connected to the input end of the inverter and the second input end of the data selector; The output end of the pulse generator is electrically connected to the first input end of the pulse modulator; The output end of the pulse modulator is electrically connected to the input end of the amplitude modulator; The output end of the inverter is electrically connected to the first input end of the data selector; The output end of the phase detector is electrically connected to the SEL input end of the data selector; The output end of the data selector is electrically connected to the IN input end of the carrier amplifier; The OUT output end of the carrier amplifier is electrically connected to the signal output end; The program A and program B respectively enter the frequency modulator through the output ends of the program A input terminal and the program B input terminal; the center frequencies of the channels where the carriers of the program A and program B are transmitted are f1 and f2 respectively, and the center frequencies f1 and f2 are stored in the processor; After being modulated by the processor, the carrier is transmitted to form a superimposed signal and output from the output end, and finally connected to the transmitting antenna to realize program broadcasting; The amplitude modulator includes an amplitude modulation amplifier, a low-pass filter, and a high-power power supply; Both the amplitude modulation amplifier and the carrier amplifier are class C or class D amplifiers.

2. The high-efficiency dual-frequency and same-source frequency-modulated radio broadcast modulation and transmission system according to claim 1, wherein: The output end of the pulse modulator is electrically connected to the IN input end of the amplitude modulation amplifier; The OUT output end of the amplitude modulation amplifier is electrically connected to the input end of the low-pass filter; The output end of the high-power power supply is electrically connected to the POW power input end of the amplitude modulation amplifier; The output end of the low-pass filter is electrically connected to the POW power input end of the carrier amplifier.

3. The high-efficiency dual-frequency and same-source frequency modulation broadcast modulation and transmission system according to claim 1, characterized in that: The input signals of the frequency modulator for program A and program B are both N-bit binary voice voltage values, and the two programs are respectively broadcast at the carrier center frequencies of f1 and f2; variables A and B are respectively used to represent the instantaneous values of the voice voltage signals of the two programs at a certain moment; whenever the input voltage A or B changes, the frequency modulator calculates the carrier instantaneous frequencies fa and fb of the two programs according to the values of the input voltages A and B by using the following formula; fa = A * 0.15 / N + f1 - 0.075 fb = B * 0.15 / N + f2 - 0.075 Calculate the frequency fu of the U signal and the frequency fv of the V signal generated by the frequency modulator; fu = (fa + fb) / 2 fv = (|fa – fb|) / 2 where fa and fb are the instantaneous frequencies of the transmitted frequency-modulated signals corresponding to Program A and Program B, respectively; The frequency modulator outputs an X signal with a frequency of fx. The process of obtaining the X signal is as follows: The pulse generator generates square-wave pulses and transmits them to the signal input terminal of the pulse modulator; the V signal is transmitted to the modulation input terminal of the pulse modulator, and the square wave generated by the pulse generator is modulated into an X signal; the X signal is modulated by the amplitude modulator and then outputs a Y signal, and the U signal and the Y signal are superimposed by the carrier amplifier and then output through the output terminal.

4. The high-efficiency dual-frequency and same-source frequency-modulated radio broadcast modulation and transmission system according to claim 3, wherein: The processor receives the data of Program A and Program B, calculates the frequency fu of the U signal and the frequency fv of the V signal, controls the V oscillator to generate a V signal with a frequency of fv, and controls the U oscillator to generate a U signal with a frequency of fu; The data selector selects one of the in-phase or anti-phase signals as the U signal; when the input voltage signal A or B changes, the processor calculates a new frequency value of the U signal once and uses the new frequency value to control the operation of the U oscillator, and at the same time calculates a new frequency value of the V signal once and uses the new frequency value to control the operation of the V oscillator; The U oscillator directly changes the output new frequency upon receiving the processor control signal; the V oscillator starts to output a new frequency when receiving the processor's control signal according to the voltage value and phase of the current sine waveform.

5. The high-efficiency dual-frequency and same-source frequency-modulated radio broadcast modulation and transmission system according to claim 4, wherein: The phase of the U signal output by the frequency modulator needs to be synchronously changed according to the polarity change of the V signal. When the V signal enters the negative half-cycle from the positive half-cycle, the U signal needs to be inverted by 180 degrees; if the V signal returns from the negative half-cycle to the positive half-cycle again, the U signal returns from the anti-phase to the normal phase; Specifically: The phase detector detects the phase of the V signal. When the V signal is in the positive half-cycle, the data selector selects the signal output by the U oscillator as the U signal and outputs it to the carrier amplifier; when the V signal is in the negative half-cycle, the data selector selects the inverted signal output by the U oscillator as the U signal and outputs it to the carrier amplifier.

6. The high-efficiency dual-frequency and same-source frequency-modulated radio broadcast modulation and transmission system according to claim 5, wherein: The X signal output by the frequency modulator is amplified and filtered by an amplitude modulation amplifier and a low-pass filter to generate a Y signal; the waveform of the Y signal is a half-cycle sine wave, only the positive-polarity part in the sine waveform, and the negative-polarity part in the sine waveform is inverted to be the positive-polarity; the frequency of the Y signal is twice the frequency of the V signal.

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