CN1200518C

CN1200518C - Double moduration type radio transmitter

Info

Publication number: CN1200518C
Application number: CN 01133322
Authority: CN
Inventors: 郭建军
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-19
Filing date: 2001-10-19
Publication date: 2005-05-04
Anticipated expiration: 2021-10-19
Also published as: CN1412950A

Abstract

The present invention discloses a double modulation type radio transmitter which mainly solves the problems of poor interference rejection and low fidelity existing in MW-SW (Medium Wave Short Wave) radio communication broadcasting receiving equipment. The transmitter comprises a high-frequency signal oscillator, a high-frequency amplifier circuit, an audio amplifier circuit, an amplitude keying modulator and an audio duty cycle modulator, wherein the amplitude keying modulator is arranged between the high-frequency signal oscillator and the high-frequency amplifier circuit; the audio duty cycle modulator is arranged between the audio amplifier circuit and the amplitude keying modulator. High-frequency oscillation signals and pulse square signals are output into high-frequency interrupted waves through the amplitude keying modulator; after high-frequency amplification, the signals are transmitted by an antenna and can be received for processing by a receiver or a radio.

Description

A kind of double moduration type radio transmitter

One, technical field

The present invention relates to radio communication broadcasting, be specially adapted to the receiver or the wireless double moduration type radio transmitter of the communication of short-and-medium wave band.

Two, background technology

Medium wave (MW) is the broadcast band that extensively adopt in present countries in the world and area.Be mainly used in domestic, inside the province, the broadcasting of middle distance such as provincialism.

Shortwave (SW) utilizes the outer surface ionosphere multihop propagation signal of the earth, and the broadcasting coverage distance is far away.Adopted as the international broadcasting wave band by countries in the world, be widely used in military affairs, civilian and ham radio broadcast communication simultaneously again.

Utilize the in-plant high-fidelity broadcast system of ultrashort wave frequency modulation (FM) in addition in addition, propagate with linear fashion, coverage is about tens kilometers usually.Be that quantity is maximum, the broadcast system that tonequality is best.Disadvantage is exactly that propagation distance is too near.Though and the intermediate waves propagation distance is far.But the amplitude modulation standard that adopts is subject to disturb at present.Especially the radio reception effect lower tone of short-wave band, noise is big, sounds unpleasant.This is strong and weak the variation along with the audio frequency signal amplitude power changes and respective change of amplitude of the high frequency radio wave of amplitude modulation standard, and the strong and weak objective condition that is subjected to natural environment easily that changes of high frequency radio wave amplitude is disturbed.In the radio receiver of amplitude modulation standard, can not find effective jamproof technological means again and overcome this electromagnetic interference.The radio communication receiver of this amplitude modulation standard or broadcast receiver just have unsurmountable noise big, the deficiency of lower tone.

The amplitude of above-mentioned said radio wave is subjected to the interference of objective environment easily.And the frequency change of radio wave just wavelength change be not easy to be interfered.So the radio broadcasting and the communication apparatus of frequency modulation standard have just been arranged.But the radio broadcasting of frequency modulation standard can only be applicable on the high-frequency modulation system of ultra-short wave band.Low frequency for short-and-medium wave band is just inapplicable.Because the frequency resource of intermediate waves is limited, the radio wave frequency band of emission requires narrow.The radio wave frequency of launching between radio station and the radio station is adjacent very near.And the very big frequency band of frequency-modulated wave frequency deviation is very wide, will make mutual interference mutually between adjacent radio station and the radio station if be used for the intermediate waves wave band.This is unallowed.So the broadcasting of the radio communication of short-and-medium wave band does not up to the present also have a kind of modulation system of high-fidelity.

Three, summary of the invention

The objective of the invention is to have the problem of anti-interference difference and lower tone, and a kind of new modulation system is provided, be i.e. double moduration type radio transmitter at above medium wave band, short-wave band radio communication apparatus for receiving broadcasting.

For realizing the object of the invention, take following measure technically:

A kind of double moduration type radio transmitter, it comprises high-frequency signal oscillator, high-frequency amplifier circuit, audio amplifier circuit, it is characterized in that: between high-frequency signal oscillator and high-frequency amplifier circuit, be provided with the amplitude keying modulator, between audio amplifier circuit output and the input of amplitude keying modulator, be provided with the audio frequency duty cycle modulator that produces square-wave signal; The operating frequency of its duty cycle modulator is 30～100KHZ, the input of the audio signal ending connecting audio duty cycle modulator of said audio amplifier circuit output, through the square-wave signal of duty cycle modulator output for the pulse square wave of audio signal voltage size variation to change, the output termination amplitude keying modulator input of this signal, another input of the high-frequency oscillation signal termination amplitude keying modulator of high-frequency signal oscillator output is exported the high frequency discontinuous wave signal termination high-frequency amplifier circuit that be loaded with audio frequency with audio frequency duty cycle pulse signal by the amplitude keying modulator when high-frequency signal and is launched through antenna.

The present invention compared with prior art beneficial effect is as follows:

Transmitter of the present invention and existing amplitude modulation, frequency modulated transmitter are different is that the signal launched is the high frequency discontinuous wave that is loaded with audio frequency through twice modulation.Through primary modulation be the duty ratio audio signal for the pulse square wave of audio signal voltage size respective change, the intrinsic frequency of oscillation of the pulse square wave of this change in duty cycle self is constant, voltage amplitude is constant, have only the waveform duty cycle of square wave to change, by the amplitude keying modulator, the constant amplitude high-frequency signal is modulated into the high frequency discontinuous wave that is loaded with audio frequency again.This high frequency waves signal can make the meeting of receiver or wireless tonequality better, and antijamming capability is stronger.Than highly sensitive a lot of times of intermediate waves amplitude-modulation receiver.Also can make original intermediate waves amplitude-modulation receiver still can receive use.

Four, description of drawings

Fig. 1 is an integrated circuit block diagram of the present invention;

Fig. 2 is Fig. 1 audio frequency duty cycle modulator and amplitude keying modulator circuitry phase schematic diagram;

Fig. 3 plants the circuit theory diagrams of audio frequency duty cycle modulator for other of Fig. 2.

Five, embodiment

Referring to accompanying drawing 1～3, double moduration type radio transmitter, it comprises high-frequency signal oscillator, high-frequency amplifier circuit, audio amplifier circuit, also is provided with amplitude keying modulator, audio frequency duty cycle modulator; The operating frequency of said audio frequency duty cycle modulator is 30～100KHZ, and preferred operating frequency is 32KHZ～80KHZ; Frequency optimum traffic is 35～36KHZ, the audio signal of said audio amplifier circuit output connects audio frequency duty cycle modulator input 1,2 ends respectively through its amplifying circuit triode VT5 emitter and collector electrode, pulse square wave through the output of audio frequency duty cycle modulator connects amplitude keying modulator input P2 end, the high-frequency oscillation signal of high-frequency signal oscillator output connects the P3 end of amplitude keying modulator input, high-frequency signal and duty cycle pulse signal are by the amplitude keying modulator, and its output P4 high-frequency signal is launched through high-frequency amplifier circuit, antenna T.

See Fig. 2 audio frequency duty cycle modulator, it is by triode VT6, VT7, and resistance R 1～R4, capacitor C 3～C4 form multivibrator, capacitor C 1, C2, resistance R 5～R6 formation.Its audio signal output is multivibrator input 1,2 ends respectively, connect the corresponding end of capacitor C 1, C2 again respectively, the end in addition of capacitor C 1, C2 connects oscillator resistor R2, R3 (A, B) point respectively, and A point and B point be connecting resistance R5～R6 one end again, and its resistance R 5～R6 is the termination power positive pole in addition.

See Fig. 3, other plants the audio frequency duty cycle modulator, can constitute by producing square-wave signal circuit and divider resistance R7 '～R8, and its signal circuit is made of saw-toothed wave generator, voltage comparator A1, its saw-toothed wave generator is by voltage comparator B 1, resistance R 9～R13, and capacitor C 6, diode D form; Said divider resistance R7 '～R8 serial connection, divider resistance R7 ' connects positive source, resistance R 8 is the termination power negative pole in addition, meet comparator A1 between divider resistance R7 '～R8 and import 7 pin, the sawtooth voltage of saw-toothed wave generator output meets voltage comparator A1 and imports 6 pin, audio signal is imported 7 pin through capacitor C 1 connecting resistance voltage comparator A1, and its 1 pin output connects positive source through pull-up resistor R14, and the audio frequency duty cycle pulse signal of comparator A1 output connects the P2 end of amplitude keying modulator.

The amplitude keying modulator is formed by the Automatic Electronic Switch that is subjected to pulse square wave signal control with by the high-frequency amplifier circuit that triode VT2, capacitor C 6～C8, transformer T1, resistance R 15～16 are formed, its electronic switch is made up of triode VT3, VT8, resistance R 7, capacitor C 5, is the electronic switch of the conducting over the ground of triode VT2 in the high-frequency amplifier circuit; The pulse square wave signal of its duty cycle modulator output connects triode VT8 base stage, the emitter of its triode VT8 connects the base stage of triode VT3 through resistance R 7, its triode VT3 collector electrode connects the grounded emitter of amplifying circuit triode VT2, and triode VT8 collector electrode connects positive source.

The course of work of this transmitter

When audio amplifier circuit does not have the audio voltage input, the audio frequency duty cycle modulator does not have the audio signal input yet, at this moment audio frequency duty cycle modulator output frequency constant (frequency of oscillation by F=1/1.4RC formula calculate), voltage amplitude is constant, the pulse square wave that duty ratio is also constant.At this moment high-frequency oscillation signal and be not loaded with the duty cycle pulse square-wave signal of audio frequency, the high frequency discontinuous wave of exporting after the amplitude keying modulators modulate is not loaded with audio signal yet; When audio amplifier circuit output had audio voltage signal, the pulse square wave of audio frequency duty cycle modulator output was a change in duty cycle, and promptly waveform width changes and the square wave of respective change along with audio voltage amplitude size variation.When high-frequency signal and duty ratio audio signal inputed to the amplitude keying modulator simultaneously, the high frequency discontinuous wave after this modulators modulate was loaded with audio signal, after high-frequency amplifier circuit amplifies, launched radio wave through antenna again.

Claims

1, a kind of double moduration type radio transmitter, it comprises high-frequency signal oscillator, high-frequency amplifier circuit, audio amplifier circuit, it is characterized in that: between high-frequency signal oscillator and high-frequency amplifier circuit, be provided with the amplitude keying modulator, between audio amplifier circuit output and the input of amplitude keying modulator, be provided with the audio frequency duty cycle modulator that produces square-wave signal; The operating frequency of its duty cycle modulator is 30～100KHZ, the input of the audio signal ending connecting audio duty cycle modulator of said audio amplifier circuit output, through the square-wave signal of duty cycle modulator output for the pulse square wave of audio signal voltage size variation to change, the output termination amplitude keying modulator input (P2) of this signal, another input (P3) of the high-frequency oscillation signal termination amplitude keying modulator of high-frequency signal oscillator output is exported the high frequency discontinuous wave signal termination high-frequency amplifier circuit that be loaded with audio frequency with audio frequency duty cycle pulse signal by the amplitude keying modulator when high-frequency signal and is launched through antenna (T).

2, double moduration type radio transmitter according to claim 1, it is characterized in that: said audio frequency duty cycle modulator is by multivibrator and two resistance (R5, R6), two electric capacity (C1, C2) constitute, its audio signal output connects transistor collector end in the oscillator, emitter terminal, collector electrode connects the corresponding end of first electric capacity (C1), emitter connects another electric capacity (C2) corresponding end, the end in addition of two electric capacity meets two groups of resistance (R2 of oscillator respectively, R5), (R3, R6) two of line point (A between, B) on, two resistance (R5 wherein, R6) termination power positive pole in addition.

3, double moduration type radio transmitter according to claim 1, it is characterized in that: said audio frequency duty cycle modulator, can constitute by producing circuit and square-wave and two divider resistances (R7 ', R8), its circuit and square-wave is made of saw-toothed wave generator, voltage comparator (A1); Two divider resistances (R7 ', R8) of serial connection, one of them divider resistance (R7 ') is the termination power positive pole in addition, another divider resistance (R8) is the termination power negative pole in addition, connect the input pin (7) of comparator (A1) between two divider resistances (R7 ', R8), audio signal input end connects the input pin (7) of comparator (A1), the input (P2) of the output termination amplitude keying modulator of its comparator (A1) through electric capacity (C1).

4, according to claim 1,2 or 3 described double moduration type radio transmitters, it is characterized in that: said audio frequency duty cycle modulator operating frequency is 32KHZ～80KHZ.

5, double moduration type radio transmitter according to claim 4 is characterized in that: the operating frequency of said audio frequency duty cycle modulator is 35KHZ～36KHZ.