CN116886120A - Simple VHF frequency channel transceiver - Google Patents

Abstract

The invention relates to a simple VHF frequency channel transceiver, which belongs to the technical field of very high frequency transceivers. The device comprises a device box and a circuit board, wherein the device box comprises a shell, a cover plate and a shielding cavity, and a transceiver channel module arranged on the circuit board comprises a receiving circuit, a transmitting circuit and a power circuit; the receiving circuit consists of a low-noise amplification frequency selection circuit, a frequency mixing circuit, an intermediate frequency amplification circuit, an intermediate frequency crystal filtering circuit, an automatic gain control circuit, a receiving demodulation circuit and a receiving frequency synthesis circuit; the transmitting circuit consists of a transmitting frequency synthesis, a transmitting front-stage driving amplification, a transmitting rear-stage driving amplification and a power detection circuit; a plurality of shielding cavities are milled in the shell and the cover plate, each single module circuit of the receiving circuit and the transmitting circuit is respectively arranged in the shielding cavities, and the shell and the cover plate seal and shield the circuit board. The integrated design of a transceiver and the modulation of the radio frequency carrier 4FSK digital signal are realized. The receiving medium frequency, image frequency, intermodulation and spurious response indexes are excellent, the multi-channel operation has no crosstalk, the simulation sensitivity is high, the volume is small, the noise is small, the harmonic spurious suppression degree is high, and the receiving dynamic range is large.

Description

Simple VHF frequency channel transceiver

Technical Field

The invention relates to a simple VHF frequency channel transceiver, which belongs to the technical field of very high frequency transceivers.

Background

With the continuous upgrading, changing and rapid development of wireless communication equipment, the very high frequency radio stations which are still used in a large number at present have the defects of production stopping of key frequency synthesis devices, large occupied space of a receiver and a transmitter, low receiving sensitivity of analog signals, high background noise of emission and serious crosstalk when a plurality of radio stations work at different frequency points, so that the simple VHF frequency channel transceiver device for effectively reducing the space occupation rate is provided for fully modifying and utilizing the existing very high frequency radio stations, avoiding resource waste, reducing the modification cost, improving the national yield level and promoting the development of the field, has the advantages of low development cost, combining a receiving and transmitting channel into a modularization, small volume, strong working performance, convenient replacement, adapting the transformation and utilization of the very high frequency radio stations and meeting the requirements of the dual-purpose market of the military and the civilian.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the simple VHF frequency channel transceiver which realizes the modularization of the transceiver channel, has strong electromagnetic shielding property, small insertion loss of an intermediate frequency filter, high stop band inhibition degree, effectively improves the receiving performance index, has small occupied space, strong working performance and high reliability, realizes new service expansion by adding a 4FSK modulation carrier wave transmitting hardware platform, adapts to the transformation, upgrading and updating operation of a very high frequency radio station, has small occupied space and low transmitting noise, greatly reduces the transformation cost, is convenient to replace, furthest avoids crosstalk when a plurality of radio stations work at close distance at the same time, and has high communication quality.

The invention realizes the aim through the following technical scheme:

a simple VHF frequency channel transceiver is composed of a device box and a circuit board, wherein the circuit board is arranged in the device box; the device box is characterized by comprising a shell, a cover plate and a plurality of shielding cavities, wherein a transceiver module is arranged on the circuit board and mainly comprises a receiving circuit, a transmitting circuit and a power circuit; the receiving circuit consists of a low-noise amplification frequency-selecting circuit, a mixing circuit, an intermediate frequency amplification circuit, an intermediate frequency crystal filtering and automatic gain control circuit, a receiving demodulation circuit and a receiving frequency synthesis circuit; the transmitting circuit consists of a transmitting frequency synthesizing circuit, a transmitting front-stage driving amplifying circuit, a transmitting rear-stage driving amplifying circuit and a power detecting circuit; a plurality of shielding cavities are formed in the shell, a plurality of shielding cavities are also formed in the cover plate, the single module circuits of the receiving circuit and the transmitting circuit are respectively arranged in the shielding cavities, and the shell and the cover plate seal and shield the circuit board; the transmitting frequency synthesis circuit of the transmitting circuit selects a phase-locked loop phase discriminator with the model of LMX2571, so that 4FSK digital baseband signals are directly modulated on a radio frequency carrier wave to be modulated, and a brand new hardware platform is provided for expanding 4FSK modulated carrier waves; meanwhile, the FM analog modulation signal is input through a transmitting voltage-controlled oscillator VCO to generate a FM modulation carrier wave.

The circuit board is characterized in that a 25-core socket is arranged on one side of the circuit board, XS 1-XS 4 radio frequency sockets are arranged on the other side of the circuit board, the XS1 radio frequency sockets are connected with an external receiving radio frequency interface, the XS2 radio frequency sockets and the XS3 radio frequency sockets are connected with an external cavity filter, and bottom noise of a transmitting signal and harmonic wave and clutter signals are restrained through the external cavity filter.

The low-noise amplification frequency-selecting circuit of the receiving circuit selects a low-noise amplifier with the model of ATF54143, the radio frequency band-selecting filter selects a surface acoustic wave filter with the model of SF1137, the intermediate frequency filter selects a crystal filter with the model of LST58.05OMA3, and the phase-locked loop phase detector of the receiving circuit selects a double-ring phase detector with the model of ADF 4212.

The emission front-stage driving amplifying circuit selects a radio frequency power amplifying tube with the model number of 2SC3357-A, the emission rear-stage driving amplifying circuit selects a high-power driving amplifier with the model number of RD01MUS2B, and the power detection circuit comprises a microstrip line coupler, a resistor pi-shaped attenuator and a logarithmic detector.

The transmitting voltage-controlled oscillator VCO and the loop filter are constructed by discrete components and are arranged in a shielding cavity for full isolation and shielding.

The transmitting circuit generates a radio frequency carrier wave through the PLL transmitting frequency synthesizing circuit, modulates an input audio signal onto the radio frequency carrier wave generated by the transmitting voltage-controlled oscillator VCO in an FM frequency modulation mode, and directly modulates a 4FSK digital signal onto the radio frequency carrier wave through a phase-locked loop phase discriminator of the transmitting frequency synthesizing circuit, so that automatic closed-loop adjustment and amplification of transmitting power are realized, and harmonic clutter and background noise are effectively restrained.

The power supply circuit consists of a low-voltage-difference voltage-stabilizing circuit, an external interface circuit and a voltage conversion circuit, wherein the low-voltage-difference voltage-stabilizing circuit is arranged on a circuit board, the low-voltage-difference voltage-stabilizing circuit adopts direct-current voltage-stabilizing circuits with the types of XC6210A502MR, XC6204A332MR and 78L08, and the external interface circuit adopts a socket with the specification of 220-251-20-10 to be connected with an external interface; the voltage conversion circuit is used for realizing control signal level inversion by adopting model numbers DTC124EKA and 74AHC1G 00.

The external control circuit consists of a control processor, an asynchronous serial port circuit and a key circuit, wherein the control circuit adopts a ST89LE516RD chip, and the PLL phase-locked loop frequency synthesis control of the receiving circuit and the transmitting circuit is realized; the asynchronous serial circuit adopts MAX3245EEAT to realize the conversion of RS232 level and LVCMOS3.3V level; the key circuit realizes frequency change through an 8-bit dial switch; the external control circuit is connected with the 25-core socket to download programs, so that frequency word transmission, frequency point setting and channel selection of the frequency synthesis circuit formed by the receiving-transmitting phase-locked loop are realized.

Compared with the prior art, the invention has the beneficial effects that:

according to the simple VHF frequency channel transceiving device, the transceiving channels are combined into a modularization, space occupation is greatly reduced, a phase discrimination chip of a phase-locked loop of a transmitting frequency synthesizer adopts LMX2571 to directly modulate 4FSK to a radio frequency carrier, a receiving frequency synthesizer adopts ADF4212 to perfectly replace original LMX2335, a radio frequency selection filter adopts a surface acoustic wave filter SF1137, the volume of an original cavity spiral filter is greatly reduced, an intermediate frequency filter adopts a LST58.050MA3 crystal filter with higher rectangular coefficient and smaller passband insertion loss, receiving intermediate frequency, image frequency, intermodulation and spurious response indexes are obviously improved, meanwhile, a plurality of shielding cavities milled in a shell are optimally selected, so that the radio channels have no crosstalk, the analog sensitivity is higher, the transmitting background noise is small, the harmonic spurious suppression degree is high, the dynamic range of a receiver is large, and the problems that key frequency synthesis devices in the 155-163 MHz working frequency band transceiving channel exist are stopped, the occupied space of the receiver and the transmitter is large, the receiving sensitivity of analog signals is low, the transmitting background noise is high, and a plurality of radio stations work at different serious frequency points are fully used.

The simple VHF frequency channel transceiver device is shown by the actual measurement result of 156.800MHz test: the frequency error is 0.3ppm, the audio distortion is 1.0%, the modulation distortion transmitting carrier power is 29.5dBm, the modulation distortion is 1.1%, the 2 nd harmonic suppression is 80.0dB, the third harmonic suppression is 79.8dB, the analog sensitivity is-122 dBm, the spurious response immunity is more than or equal to 71dB, the intermodulation (200 KHz interval) is 70.8KHz intermediate frequency and image frequency suppression is 90dB, and the double signal selectivity is 72.8dB. The dynamic range of the receiving channel exceeds more than 100dB, and the performance index is excellent. The VHF frequency band transceiver channel device realizes reliable transmission, clear transceiver voice and strong practicability, and is very suitable for the transformation, upgrading and upgrading of very high frequency radio stations.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a simple VHF channel transceiver;

FIG. 2 is a schematic structural view of a cover plate;

FIG. 3 is a schematic structural view of the housing;

FIG. 4 is a schematic view of A-A of FIG. 3;

FIG. 5 is a schematic view of B-B of FIG. 3;

FIG. 6 is a schematic view of C-C of FIG. 3;

FIG. 7 is a schematic view of D-D of FIG. 3;

FIG. 8 is a schematic block diagram of the operating principle of a simple VHF channel transceiver;

FIG. 9 is a low noise amplification frequency selection circuit diagram;

fig. 10 is a mixer circuit diagram;

FIG. 11 is an intermediate frequency amplifying circuit diagram;

FIG. 12 is a diagram of an intermediate frequency crystal filtering and automatic gain control circuit;

fig. 13 is a reception demodulation circuit diagram;

fig. 14-1 is a receiving frequency synthesizing circuit diagram;

fig. 14-2 is a receive frequency synthesis circuit diagram;

fig. 15 is a transmission frequency synthesizing circuit diagram;

fig. 16 is a front-stage drive amplification circuit diagram;

fig. 17 is a rear stage drive amplifying circuit diagram;

FIG. 18 is a power detection circuit diagram;

FIG. 19 is a power circuit diagram;

FIG. 20-1 is a diagram of an external control circuit;

FIG. 20-2 is a diagram of an external control circuit;

FIG. 21 is a schematic diagram of a meter and device connection for receiving analog debug;

FIG. 22 is a schematic diagram of a meter and device connection for carrier power debug;

FIG. 23 is a schematic diagram of a meter and device wiring for spurious emission component testing;

fig. 24 is a schematic rear view of the housing.

In the figure: 1. the device comprises a shell, 2, a cover plate, 3, a shielding cavity, 4 and a circuit board.

Detailed Description

The design idea of the invention is as follows: although the wireless communication equipment is continuously updated and rapidly developed, the construction cost and the original technical system of the wireless communication equipment, and the market demand, the actual condition of an industrial chain and the dynamic change of application scenes are considered, so that the equipment development and manufacturing needs are advanced, the localization rate level is improved, and the existing wireless communication equipment is fully modified and utilized to meet the demands of dual-purpose clients for the army and the civil.

The current phase-locked loop frequency synthesis chip of the receiver and the transmitter of the very high frequency radio station adopts LMX2335 of National Semiconductor company, which is a double phase-locked loop, integer frequency division PLL frequency synthesis phase discriminator, which has been stopped for many years, and the frequency synthesizer circuit of the transceiver channel needs to be redesigned; meanwhile, the original intermediate frequency crystal filter has large insertion loss, low stop band suppression degree and insufficiently steep rectangular coefficient, so that the radio station receiving performance index is low, and the original intermediate frequency 21.4MHz is improperly selected, so that a plurality of radio stations are easy to cross talk when working at close distance; the radio frequency band-pass frequency-selecting filter at the front end of the original low-noise amplifier adopts a spiral cavity structure, so that the occupied space is large, and the original radio receiver and the transmitter are of independent unit design structures, so that the miniaturization is inconvenient; and the original shielding box can only shield part of the circuit, has small coverage and insufficient electromagnetic shielding.

With the upgrading and changing of radio stations, the in-situ replacement of domestic devices is required, the occupied space is small, the original working performance is kept, more functions are continuously and perfectly configured, and the requirement on reliability is higher. Therefore, a 4FSK modulation carrier wave transmitting hardware platform is developed to expand new services, key transceiver circuits are developed and replaced by units, the transceiver circuits are combined into a modularization through cavity shielding, the transceiver circuits are adapted to the improvement and utilization of the existing very high frequency radio station, the practicability and electromagnetic shielding performance are high, the work is stable and reliable, the size is small, the localization rate level is improved, and a VHF frequency channel transceiver with low cost is very necessary.

Embodiments of the simple VHF band channel transceiving apparatus are described in further detail below (see fig. 1 to 24) with reference to the accompanying drawings:

the simple VHF frequency channel receiving and transmitting device consists of a device box and a circuit board 4, wherein the circuit board 4 is arranged in the device box; the device box consists of a shell 1, a cover plate 2 and a plurality of shielding cavities 3, wherein the shielding cavities 3 are manufactured in the shell 1 and the cover plate 2 through milling by a milling machine; the circuit board 4 is vertically fixed in the shell 1 through the screw, the cover plate 2 is matched with the shell 1 to seal and shield the circuit board 4, the plates of the shell 1 and the cover plate 2 are made of aluminum alloy, and electromagnetic leakage is prevented. One side of the circuit board 4 is provided with an XS1 radio frequency socket-XS 4 radio frequency socket, and the other side of the circuit board 4 is provided with a 25-core socket; the XS1 radio frequency socket-XS 4 radio frequency socket and the 25-core socket are used as external interfaces to be respectively connected with an external control circuit and an audio frequency and PTT state signal interface.

The XS1 radio frequency socket of the circuit board 4 is connected with an external transmitting radio frequency interface, the XS4 radio frequency socket is connected with an external receiving radio frequency interface, the XS2 radio frequency socket and the XS3 radio frequency socket are connected with an external cavity filter, so that bottom noise of a transmitting signal is restrained, and meanwhile, harmonic waves and clutter are restrained; the external cavity filter is a narrow-band cavity band-pass filter, adopts a resonant rod coupling design, comprises four resonant cavities, and tuning screws of the four resonant cavities are used for fine tuning the bandwidth and the frequency of the external cavity filter; the external cavity filter has the characteristics of firm structure, stable and reliable performance, small volume, moderate Q value, far high-end parasitic passband and good heat dissipation performance, and is applicable to high power and high frequency. Through frequency selection and stop band suppression of an external cavity filter, out-of-band interference signals are effectively suppressed, and in-band signals are received with low insertion loss and enter a receiving circuit channel; meanwhile, the out-of-band spurious and noise of the transmitting signal output by the power amplifier are effectively restrained, and particularly, the out-of-band electromagnetic pollution is restrained, and the background noise and interference resistance of the receiving background is improved.

The circuit board 4 is provided with a transceiver/transmitter module which mainly comprises a receiving circuit, a transmitting circuit and a power circuit; the receiving circuit consists of a low-noise amplification frequency-selecting circuit, a mixing circuit, an intermediate frequency amplification circuit, an intermediate frequency crystal filtering and automatic gain control circuit, a receiving demodulation circuit and a receiving frequency synthesis circuit; (see FIGS. 9-14).

The whole receiving circuit adopts a superheterodyne secondary receiving circuit architecture, wherein the first intermediate frequency is 58.05MHz, and the second intermediate frequency is 455KHz; the low-noise amplifier in the low-noise amplifying frequency-selecting circuit (see fig. 9) and the low-noise amplifier in the intermediate-frequency amplifying circuit (see fig. 11) select ATF54143, the noise coefficient is 0.5dB, the P1dB compression point output power is 20.4dBm, and the gain is 16.6 dB.

Radio frequency band pass frequency-selecting filter (see figure 9) adopting Beijing Zhongxin tetragonal sound surface filter SF1137 and packaging size of 5.00x1.50mm ³ The original cavity spiral filter is replaced, the volume is smaller, the center insertion loss is 1.7dB, the BW1dB bandwidth is 9.7MHz, and the BW40dB bandwidth is 29MHz.

The intermediate frequency crystal filter and the automatic gain control circuit (see figure 12) adopt LST58.05OMA3 of Liaoning Hongyu, the stop band attenuation reaches more than 80dB, the rectangular coefficient is 2.5, the insertion loss is 2.8dB, the nominal frequency is 58.050MHz, and the intermediate frequency, the image frequency, the intermodulation and spurious response indexes are improved.

The mixer circuit (see fig. 10) has a mixer device that uses ADL5350, radio frequency input and radio frequency local oscillation signal lo_v5 generated by the receiving frequency synthesizer in the receiving frequency synthesizer circuit (see fig. 14-1 and 14-2), the generated intermediate frequency signal is amplified by the intermediate frequency amplifying circuit (see fig. 11), and after being filtered by the intermediate frequency crystal and being automatically gain controlled circuit (see fig. 12), the intermediate frequency signal is sent to the frequency discriminator n jm2591 in the receiving demodulation circuit (see fig. 13) to perform two intermediate frequency mixing, 455KHz frequency discrimination processing, and the analog audio signal is demodulated and is sent to the audio operational amplifier SM358 to be amplified, then analog voice is restored, meanwhile, the two intermediate frequency internal is also subjected to AGC closed loop control, and three-stage AGC automatic adjustment makes the dynamic range of the receiving circuit reach more than 105 dB.

The phase-locked loop phase detector in the receiving frequency synthesizing circuit (see fig. 14-1 and 14-2) adopts a double-loop ADF4212 phase detector, and adopts an integer frequency division phase locking mode to realize perfect substitution of LMX2335; the receive voltage controlled oscillator VCO and the loop filter are built with discrete devices, the technology is autonomously controllable (see fig. 14 and 15), and the shielding is isolated by means of the respective shielding cavities 3.

The radio frequency AGC adjusting device in the mixing circuit (see fig. 10) adopts an analog attenuator RFSA2013, an analog field intensity signal RSSI is automatically detected through a frequency discriminator NJM2591 in the receiving demodulation circuit (see fig. 13), the radio frequency analog attenuator RFSA2013 is controlled, when the received radio frequency signal is strong enough, the analog voltage of the RSSI is increased, the attenuation amount of the analog attenuator is increased, the radio frequency input signal is reduced, the analog voltage of the RSSI is reduced, and the automatic gain control of the radio frequency AGC is realized. Intermediate frequency automatic gain adjustment (see fig. 12) is also an intermediate frequency automatic gain AGC adjustment by the RSSI signal closed loop control 3SK 294.

Each module circuit of the receiving circuit is correspondingly arranged in a shielding cavity 3 of the shell 1 and the cover plate 2, and is fully and effectively isolated and shielded by the shielding cavity 3; the receiving circuit realizes the functions of radio frequency useful signal selection, low noise amplification, radio frequency AGC adjustment, receiving PLL frequency synthesis, frequency mixing and conversion, intermediate frequency amplification, intermediate frequency crystal filtering, intermediate frequency AGC adjustment, intermediate frequency discrimination demodulation and audio amplification. The XS4 radio frequency sockets on circuit board 4 are connected to an external receive radio frequency interface through the XS4 sockets of housing 1, and the external interfaces of the remaining module circuits are connected to 25-core sockets.

The transmitting circuit consists of a transmitting frequency synthesizing circuit, a transmitting front-stage driving amplifying circuit, a transmitting rear-stage driving amplifying circuit and a power detecting circuit; (see FIGS. 15-18).

The circuit board 4 is also provided with an external control circuit, an external cavity filter and a loop filter, and the loop filter of the transmitting circuit and the transmitting voltage-controlled oscillator VCO are formed by discrete components (see figure 14) and are correspondingly arranged in the shielding cavity 3.

The phase-locked loop phase discriminator of the transmitting frequency synthesizing circuit (see fig. 15) adopts LMX2571, 4FSK digital baseband signals sent by three control lines CLOCK, DATA, LETX are directly modulated on radio frequency carrier waves generated by a transmitting voltage-controlled oscillator VCO, and a brand new hardware platform is provided for expanding the 4FSK modulated carrier waves; meanwhile, FM analog modulation is input through a modulation input port MODOVCO of a transmitting voltage-controlled oscillator VCO to generate a frequency modulation carrier wave; the method is perfect to replace LMX2335, realizes direct 4FSK digital signal modulation, and is beneficial to upgrading, updating and reconstruction of the existing very high frequency radio station.

The front two-stage driving radio frequency power amplifying tube in the front-stage driving power amplifying circuit (see fig. 16) of the transmitting circuit adopts 2SC3357-A, the modulating carrier power is pushed to 20 dBm+/-0.5 dBm through two-stage cascade amplification, the modulating carrier power is sent to the matched filtering input port in the rear-stage driving amplifying circuit (see fig. 17), the high-power amplification is carried out through the power push amplifier RD01MUS2B, 31.5 dBm+/-0.5 dBm output power is generated, the high-power amplification is filtered through the low-pass filter, the high-power output power is sent to the external cavity filter through the radio frequency socket XS3 for harmonic wave, spurious and transmitting background noise suppression, the high-power is output through the external cavity filter, the high-power output is sent to the microstrip line coupler in the power detecting circuit (see fig. 18) through the XS2 radio frequency socket, and the microstrip line coupler is sent to the XS1 radio frequency socket for outputting the transmitting radio frequency power through extremely low insertion loss; the transmitting power coupled by the microstrip line coupler is attenuated by a resistance pi-type network and then sent to a logarithmic detector AD8361ARM, the radio frequency power signal is detected into analog voltage, the analog voltage is directly subjected to closed loop control on the gate input end of a rear-stage driving amplifying circuit (see figure 17) through the negative feedback amplification of an operational amplifier OPA2227U, and the gate input end of the rear-stage driving amplifying circuit is directly subjected to closed loop control on the analog voltage, so that the closed loop adjustment control on the transmitting power is realized.

The loop filter of the transmitting circuit is connected with the phase detector chip of the LMX2571 phase-locked loop of the transmitting frequency synthesizer circuit (see fig. 15), the transmitting voltage-controlled oscillator VCO and the loop filter are built by discrete devices, and are correspondingly placed in the shielding cavity 3 to be fully isolated and shielded. The external cavity filter of the rear stage of the power push amplifier adopts a custom-made module, has high Q value and stop band rejection rate and small insertion loss, and effectively suppresses the transmitted background noise and spurious.

The transmitting circuit generates a radio frequency carrier wave through PLL frequency synthesis, modulates an input audio signal onto the radio frequency carrier wave generated by the VCO in an FM mode, directly modulates a 4FSK digital signal onto the radio frequency carrier wave through a phase-locked loop phase discriminator, and realizes automatic closed-loop adjustment and amplification of transmitting power, thereby effectively inhibiting harmonic clutter and background noise. The XS1, XS2 and XS3 radio frequency sockets on the circuit board 4 are connected with the XS1, XS2 and XS3 sockets of the shell 1 in a one-to-one correspondence manner, wherein the XS2 and XS3 sockets of the shell 1 are connected with an external cavity filter, the XS1 socket of the shell 1 is connected with an external emission radio frequency port, and external interfaces of the rest module circuits are connected with 25 core sockets.

The external cavity filter is a narrow-band cavity band-pass filter.

The power supply circuit mainly comprises a low-dropout voltage stabilizing circuit, an external interface circuit and a voltage conversion circuit (see figure 19); the low dropout voltage regulator circuit is composed of a plurality of LDO low dropout voltage regulators, mainly uses XC6210A502MR, XC6204A332MR and 78L08 devices, and an external interface circuit connects input and output signals and a power supply with an external interface through 220-251-20-10 sockets. The voltage conversion circuit mainly relies on DTCs 124EKA and 74AHC1G00 to realize control signal level inversion. The power supply circuit realizes control signal switching, external interface switching and provides stable direct current voltage for each module circuit. The power circuit is connected with an external debugging interface through a 25-core socket.

The external control circuit mainly comprises a control processor, a key circuit and an asynchronous serial circuit. The control circuit adopts an ST89LE516RD+ chip to realize the PLL frequency synthesis control of the receiving circuit and the transmitting circuit; the asynchronous serial circuit adopts a MAX3245EEAT chip to realize the conversion of RS232 level and LVCMOS3.3V level; the key circuitry effects the frequency change by an 8-bit dip switch (see fig. 20-1 and 20-2).

The external control circuit is mainly used for being matched with the simple VHF frequency band receiving and transmitting channel device for debugging, belongs to an independent external circuit and realizes the interface debugging control of the simple VHF frequency band receiving and transmitting channel device; the external control circuit is connected with the 25-core socket and the receiving/transmitting channel module for downloading programs, so that the frequency synthesis circuit formed by the receiving/transmitting phase-locked loop is subjected to frequency word transmission, frequency point setting, channel selection, PTT receiving/transmitting control and mode selection.

The following table shows the material composition of the simple VHF frequency channel transceiver

The checking and debugging process of the simple VHF frequency channel transceiver device is as follows:

the device box of the simple VHF frequency channel transceiver consists of a shell 1, a cover plate 2 and a shielding cavity 3 (see fig. 1-7), wherein the connection structure of an external cavity filter and an external transceiver XS 2-XS 3 radio frequency socket (see fig. 1, 8 and 24) is formed. The simple VHF frequency channel transceiver is a schematic block diagram (see fig. 8), and each single module circuit of the receiving circuit and the transmitting circuit, a power supply circuit and an external control circuit (see fig. 9-20) are used for checking and debugging processes (see fig. 21-23).

The simple VHF frequency channel transceiver device is used for checking and debugging as follows:

2955B comprehensive tester 1 table

UT61E Universal meter 1

JWY-30D direct-current stabilized voltage supply 1 station

ROHDE & SCHWARZ FSP spectrometer 1 table

E4432B Agilent 250 KHz-3.0 GHz signal source 1 station

40dB attenuator 1

The checking and debugging steps are as follows:

checking whether the front and back sides of the circuit board 4 have elements and welding points which are short-circuited with the ground or are in cold joint, and whether the polarity of the electrolytic capacitor has error or not; the circuit board 4 is installed in the shell 1, the cover plate 2 is installed on the circuit board 4, and the circuit board 4 is isolated, shielded and fixedly installed through the shell 1 and the shielding cavity 3 of the cover plate 2.

1) External control circuit debugging (see fig. 20-1 and 20-2): the comprehensive tester and the frequency spectrograph are electrified and preheated for a few minutes, the comprehensive tester works in an initial state, one of the switches of the channels CH 1-CH 6 is turned to the ON side, the ON represents a low level, the other 5 channels are turned to one side of the connected pull-up resistor, the pull-up resistor side represents a high level, and the low level represents that a certain channel of the gating frequency is effective; the low level of the side of the S8 terminal PTT is turned ON to indicate effective receiving, and the PTT is turned ON to indicate effective transmitting of the high level ON the side of the pull-up resistor; the MODE ON side indicates that FM analog phone is effective, and the MODE ON side high level indicates that digital phone 4FSK is effective; the turning ON of V5/V6 indicates that VHF band selection is active, where S1-S6 indicate channel 1 to channel 6 frequency selective switches.

PTT on the external control circuit (see FIG. 20-1 and FIG. 20-2) is set to be effective in low level reception, a plurality of groups of direct current stabilized power supplies are prepared to output direct current voltages required by multipath debugging, the external control circuit is communicated with the power supply circuit (see FIG. 19) by using a 25-core switching wire, and the direct current voltages of +12V input by 5 pins, +3.6V input by 7 pins, +5.5V input by 9 pins and +24V input by 11 pins of XS6 (see FIG. 20); the 5-pin output of test N4 (see FIG. 20) should be 3.3+ -0.1V, N4 in the power circuit (see FIG. 19) 8 V+ -0.2V, N10, N28 5 V+ -0.15V, N6, N9 3.3 V+ -0.1V. If the output voltage of the low dropout regulator circuit is abnormal, it is checked whether the circuit is cold-soldered, the integrated circuit is damaged, and the input voltage is out of the normal range.

2) Debugging of the receiving circuit (see fig. 21): connecting an RF port of a comprehensive tester to an XS4 radio frequency socket on a circuit board 4 of the simple VHF channel transceiver, setting the comprehensive tester as RX TEST, setting the modulation frequency as 1kHz and the modulation frequency as 3kHz, outputting the radio frequency signal amplitude of the comprehensive tester as-47 dBm, and setting the frequency output as 156.800MHz; the S2 dial switches S2 and PTT, MODE, V/V6 in an external control circuit (see fig. 20-1 and 20-2) are all turned ON, the low level is selected to be effective, the output end of the 17 pin of the XS6 socket is connected to an AF input audio input port of the comprehensive tester, the AF audio output amplitude is 110+/-10 mV, the audio distortion is less than 2.5%, and the audio output SINAD is more than 40dB. If the distortion index does not meet the requirement, the resistances of R227, R233, R271, R272 of the intermediate frequency amplifying circuit and the intermediate frequency crystal filter circuit (see fig. 11-12) are properly fine-tuned, and the output voltage of the pin 12 of the N18 of the receiving demodulation circuit (see fig. 13) should be 1.8v±0.2V, and when the output amplitude of the radio frequency signal is changed to-120 dBm, the voltage of rssi_v5 is output to 0.35v±0.2V. The radio frequency amplitude output of the comprehensive tester is regulated to change from-20 dBm to-121.5 dBm, and the audio frequency output SINAD is more than 12dB, which shows that the receiving dynamic range is better than more than 100 dB.

If the receiving dynamic range does not meet the requirement, fine tuning changes the resistance-capacitance parameter values of L45, R120 and C166 of the receiving demodulation circuit (see FIG. 13); if the audio amplitude does not meet the requirement, the resistor R118 of the receiving demodulation circuit (see fig. 13) is appropriately increased, and if the audio amplitude is too large, the resistor R118 is decreased. And slowly adjusting the output amplitude of the radio frequency signal of the comprehensive tester, and when the output amplitude of the radio frequency signal is adjusted to 12dB, the amplitude of the radio frequency signal at the moment is the analog sensitivity of 156.800MHz, and the standard reaching requirement is less than or equal to-119 dBm.

During normal test, when the radio frequency output of the comprehensive tester is-121.5 dBm+/-0.5, the audio frequency output SINAD is 12 dB+/-0.5, and the value is the analog sensitivity value. If the analog sensitivity index does not meet the requirement, checking and positioning one by one from the intermediate frequency post-stage module circuit to the pre-stage radio frequency module, and checking the signal output amplitude of each functional module in the receiving circuit step by step, wherein the voltage of the working point of the related device meets the design requirement; in the mixer circuit (see fig. 10), the input amplitude of the local oscillator lo_v5 end of the mixer N15 should be 0dbm±2dB; the input amplitude of the 1 st pin of the intermediate frequency demodulator N18 of the receiving demodulation circuit (see FIG. 13) should be-10 dBm+ -3 dB, and the frequency should be 57.6MHz; the locking voltage range of vco_v5 end in the receiving frequency synthesizing circuit (see fig. 14-1 and 14-2) is not more than 1V-3V, the N3 phase discriminator of the receiving frequency synthesizing circuit (see fig. 14-1 and 14-2) sends different frequency words through the external control circuit, and the loop filter generates different direct current locking voltages. The circuit inspection is normal, and then the amplification gain and the output waveform of each single module circuit are inspected step by step to determine whether the amplification gain and the output waveform meet the design requirements.

3) Squelch and receive performance index debugging: (see fig. 13), the terminal SQ connected to the terminal R153 and the terminal RP6 of the receiving and demodulating circuit is connected to the pin 16 of the socket XS6 of the external control circuit, the terminal SQ is connected to 1.62K to ground, the output amplitude of the radio frequency signal of the comprehensive tester is adjusted to be an analog sensitivity value, the normal value is-121.5 dbm±0.5, the potentiometer RP6 in the receiving and demodulating circuit (see fig. 13) is adjusted at this time, the collector BUSY of V27 is turned from 0V to 3.3V, the light emitting diode VD7 is on, and the adjusting squelch is set at this time just near the threshold of analog sensitivity. When the noise signal or the radio frequency useful signal received by the receiving circuit is lower than the analog sensitivity threshold, the 3 pin of the N18 of the receiving demodulation circuit (see fig. 13) outputs a high level of 5.0V, the VD7 indicator light is turned off, the collector BUSY of the V27 outputs a low level, and the receiving AF channel is controlled to be closed by BUSY= "0"; when the received radio frequency signal is higher than the analog sensitivity, BUSY outputs high level 3.3V, and the receiving AF channel is controlled to be opened by BUSY= "1", so that the squelch control function is realized.

If the intermediate frequency and image frequency inhibition index does not meet the requirement, checking V10 and N2 of a low-noise amplification frequency selection circuit (see fig. 9) of a receiving circuit, checking the total gain of V10 and N2 cascading 22 dB+/-2, checking whether the passband waveform of N2 meets the design requirement by using a network analyzer, and mainly checking whether the welding of an N2 grounding pin is fully grounded, and if the grounding is good, replacing N2.

If the tuning and dual signal selection do not meet the design requirements, checking whether the receiving local oscillation amplitude of the 3-pin input end of the N15 of the mixing circuit (see fig. 10) is 0 dBm+/-2 dB, if not, checking whether the gain of the V15 amplifier of the receiving frequency synthesizing circuit (see fig. 14-1 and 14-2) meets the 16dB amplifying gain, checking whether the input and output end resistance matching resistance pi network parameters of the Z2 intermediate frequency crystal filter (see fig. 12) are reasonable, checking the waveform of the 58.05MHz intermediate frequency crystal filter by using a network analyzer, checking the waveform change of the crystal filter while modifying the resistance values of R227, R233, R271 and R272, and repeatedly debugging until the indexes meet the requirements.

4) Transmit carrier power, transmit carrier frequency error, transmit frequency synthesis circuit debug (see fig. 22): the comprehensive tester is set to be in a P-mode state, PTT in an external control circuit (see fig. 20-1 and 20-2) is set to be in a high-level active working state, S2 channels are set to be in a low level, and S1, S3, S4, S5 and S6 channels are set to be in a high level. At this time, whether the power of the transmitting carrier wave meets 30 dBm+/-1 dB is directly read out by a comprehensive tester, and if the power does not meet the requirement, the resistor R28 of the potentiometer RP4 of the power detection circuit (see fig. 18) and the resistor R28 of the front-stage driving amplifying circuit (see fig. 16) are regulated so that the output power meets the requirement.

And reading out the transmitting frequency value, checking whether the carrier frequency error is less than or equal to 0.5ppm, and if the carrier frequency error does not meet the requirement, checking whether the input frequency precision of an external 12.8MHz clock meets the requirement. The amplitude of the C152 output RFoutTx of the transmitting frequency synthesizing circuit (see fig. 15) is normally 0dbm±2dB, the amplitude of the collector output signal of the driving amplifier V6 of the front driving amplifying circuit (see fig. 16) should be 15dbm±2dB, and the locking voltage range of the L6 terminal VTco of the transmitting voltage controlled oscillator VCO of the transmitting frequency synthesizing circuit (see fig. 15) does not exceed 0.8V to 3.8V.

5) Harmonic spurious emission component tuning (see fig. 23): and (3) connecting a radio frequency test cable connected to the simple VHF channel transceiver with a 40dB attenuator, and connecting the other end of the 40dB attenuator with an FSP spectrometer to test stray and harmonic emission components. Before testing, the resolution bandwidth RBW of the spectrometer is 3kHz, the video bandwidth VBW is 1kHz, the SPAN bandwidth is 20MHz, the center frequency is 156.800MHz, and the ATT attenuation is 20dB, so that the correct configuration of the spectrometer is ensured. In the external control circuit (see fig. 20-1 and 20-2), PTT is set to a high level active state, the S2 channel is set to a low level, and the S1, S3, S4, S5, S6 channels are set to a high level. The difference between the carrier and the harmonic, between the carrier and the spur is read directly by a spectrometer. The spurious emission component is less than or equal to-75 dBc, the harmonic emission component is less than or equal to-80 dBc, and the external body filter cavity filter is replaced when the spurious emission component does not meet the requirement.

The simple VHF frequency channel transceiver device enables an upgrading and reforming technical scheme of a VHF radio station with the frequency range of 155-163 MHz in the VHF frequency range to fall to the ground, realizes the integrated design of a transceiver channel, greatly reduces the volume of the whole machine, has the functions of 4FSK modulation and FM modulation carrier waves, optimizes and improves the electromagnetic shielding performance, improves the crosstalk problem of simultaneous work of a plurality of radio stations, and realizes the reliable transmission of the VHF frequency transceiver channel. The practical measurement shows that the simple VHF frequency band channel transceiver has the frequency error of 0.3ppm, the audio distortion of 1.0%, the modulation distortion transmitting carrier power of 29.5dBm, the modulation distortion of 1.1%, the 2 nd harmonic suppression of 80.0dB, the third harmonic suppression of 79.8dB, the analog sensitivity of-122 dBm, the spurious response immunity of more than or equal to 71dB, the intermodulation 200KHz interval of 70.8KHz intermediate frequency and image frequency suppression of 90dB and the double signal selectivity of 72.8dB. The dynamic range of the receiving channel exceeds 100 dB. The method has the advantages of large receiving dynamic range, high analog sensitivity, high intermediate frequency and image frequency suppression degree, strong intermodulation immunity, small transmitting background noise, small harmonic spurious, clear receiving and transmitting voice, superior comprehensive performance index and outstanding substantive effects.

The above description is merely a preferred embodiment of the present invention, and the above illustration is not to be construed as limiting the spirit of the present invention in any way, and any simple modification or variation of the above embodiments according to the technical spirit of the present invention, and equivalent embodiments that may be changed or modified to equivalent variations using the above disclosed technical spirit of the present invention, will still fall within the scope of the technical solutions of the present invention, without departing from the spirit and scope of the present invention.

Claims (7)

1. A simple VHF frequency channel transceiver is composed of a device box and a circuit board (4), wherein the circuit board (4) is arranged in the device box; the method is characterized in that: the device box consists of a shell (1), a cover plate (2) and a plurality of shielding cavities (3), wherein a transceiver/transmitter channel module is arranged on the circuit board (4), and the transceiver/transmitter channel module mainly consists of a receiving circuit, a transmitting circuit and a power circuit; the receiving circuit consists of a low-noise amplification frequency-selecting circuit, a mixing circuit, an intermediate frequency amplification circuit, an intermediate frequency crystal filtering and automatic gain control circuit, a receiving demodulation circuit and a receiving frequency synthesis circuit; the transmitting circuit consists of a transmitting frequency synthesizing circuit, a transmitting front-stage driving amplifying circuit, a transmitting rear-stage driving amplifying circuit and a power detecting circuit; a plurality of shielding cavities (3) are formed in the shell (1), a plurality of shielding cavities (3) are also formed in the cover plate (2), the single module circuits of the receiving circuit and the transmitting circuit are respectively arranged in the shielding cavities (3), and the shell (1) and the cover plate (2) seal and shield the circuit board (4); the transmitting frequency synthesis circuit of the transmitting circuit selects a phase-locked loop phase discriminator with the model of LMX2571, realizes that a 4FSK digital baseband signal is directly modulated on a radio frequency carrier wave, and provides a brand new hardware platform for expanding the 4FSK modulated carrier wave; meanwhile, the FM analog modulation signal is input by the VCO to generate the FM modulation carrier wave, so that the automatic closed-loop adjustment and amplification of the transmitting power are realized, and the harmonic clutter and the background noise are effectively inhibited.

2. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the circuit board (4) one side install 25 core sockets, the XS1 ~ XS4 radio frequency socket is installed to the another side of circuit board (4), XS1 radio frequency socket is connected with outside transmission radio frequency interface, XS2 radio frequency socket and XS3 radio frequency socket are connected with outside external cavity filter, restrain the bottom noise of transmission signal and restrain harmonic wave and clutter signal through external cavity filter, XS4 radio frequency socket is connected with outside receiving radio frequency interface.

3. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the low-noise amplification frequency-selecting circuit of the receiving circuit selects a low-noise amplifier with the model of ATF54143, the radio frequency band-selecting filter selects a surface acoustic wave filter with the model of SF1137, the intermediate frequency filter selects a crystal filter with the model of LST58.05OMA3, and the phase-locked loop phase detector of the receiving circuit selects a double-ring phase detector with the model of ADF 4212.

4. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the emission front-stage driving amplifying circuit selects a radio frequency power amplifying tube with the model number of 2SC3357-A, the emission rear-stage driving amplifying circuit selects a high-power driving amplifier with the model number of RD01MUS2B, and the power detection circuit comprises a microstrip line coupler, a resistor pi-shaped attenuator and a logarithmic detector.

5. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the VCO and the loop filter of the receiving circuit and the transmitting circuit are built by discrete components and are placed in a shielding cavity (3) for full isolation and shielding.

6. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the power supply circuit consists of a low-voltage-difference voltage-stabilizing circuit, an external interface circuit and a voltage conversion circuit, wherein the low-voltage-difference voltage-stabilizing circuit is arranged on a circuit board (4), the low-voltage-difference voltage-stabilizing circuit adopts direct-current voltage-stabilizing circuits with the types of XC6210A502MR, XC6204A332MR and 78L08, and the external interface circuit adopts a socket with the specification of 220-251-20-10 to be connected with an external interface; the voltage conversion circuit is used for realizing control signal level inversion by adopting model numbers DTC124EKA and 74AHC1G 00.

7. The apparatus for transmitting and receiving VHF band channel according to claim 1, wherein: the external control circuit consists of a control processor, an asynchronous serial port circuit and a key circuit, wherein the control processor selects a ST89LE516RD chip with the model number to realize the PLL phase-locked loop frequency synthesis control of the receiving circuit and the transmitting circuit; the asynchronous serial circuit adopts MAX3245EEAT to realize the conversion of RS232 level and LVCMOS3.3V level; the key circuit realizes frequency change through an 8-bit dial switch; the external control circuit downloads the program by connecting with the 25-core socket and the receiving/transmitting channel module, and realizes the frequency word transmission, frequency point setting, channel selection, PTT receiving/transmitting control and mode selection of the frequency synthesis circuit formed by the receiving/transmitting phase-locked loop.