Satellite communication transceiver based on UHF frequency band

Abstract

The utility model discloses a satellite communication transceiver based on a UHF (Ultra High Frequency) frequency range, relating to the field of satellite communication transceivers, aiming at solving the problem that TDM (Time Division Multiplexing) broadcast signals are easily interfered in the prior art, and adopting the technical scheme that a receiver is divided into a service processing unit and a TDM processing unit by a power divider; a frequency mixer is arranged in each processing unit, a one-time down-conversion and zero-intermediate-frequency demodulation scheme is formed after direct frequency reduction through the frequency mixers, and a large dynamic range can be obtained by combining a radio frequency filter, an intermediate frequency filter, a baseband filter and a low-noise power amplifier, the smoothness of a radio frequency front end is ensured when a large interference signal is received, the noise coefficient is small, and the signal quality is improved. Therefore, the receiver has high sensitivity and certain anti-interference capability at the same time.

Description

Technical Field

[0001] This utility model relates to the field of satellite communication transceiver technology, specifically a satellite communication transceiver based on the UHF band. Background Technology

[0002] In scenarios where basic communication facilities cannot provide communication support, such as disaster relief and field rescue, satellite communication transceivers are needed for voice and data communication transmission. Voice transmission relies on TDM broadcast receiving channels. However, existing satellite communication transceivers are highly sensitive to satellite signals, making TDM broadcast signals extremely susceptible to interference from nearby radio signals. This can cause abnormal TDM broadcast signal reception, often resulting in the inability to receive valid instructions and greatly reducing the effectiveness of communication. Utility Model Content

[0003] The technical problem to be solved by this invention is to overcome the existing defects and provide a UHF band satellite communication transceiver, which can effectively solve the problems in the background technology.

[0004] To achieve the above objectives, this utility model discloses a UHF band satellite communication transceiver. The technical solution includes a front-end unit connected to a communication antenna, a receiver, and a transmitter. The receiver and transmitter are connected to a modem. The modem is connected to a monitoring interface module and a power supply. The monitoring interface module is connected to a terminal device. The receiver includes a service receiving unit and a TDM receiving unit. The TDM receiving unit is responsible for receiving control commands from the central station and needs to operate continuously. The service receiving unit is responsible for processing and demodulating the satellite downlink radio frequency signal to obtain baseband I and Q signals, which are then sent to the modem unit for demodulation to obtain voice data signals. The service receiving channel operates according to the received TDM broadcast commands and is not continuously operated. The receiving end of the preamplifier unit is connected to a first surface acoustic wave (SAW) filter and then to a power divider. The power divider connects the service receiving unit and the TDM receiving unit. Both the service receiving unit and the TDM receiving unit have filters, mixers, I / Q demodulators (baseband demodulators), and bandpass filters. Each of the service receiving unit and the TDM receiving unit has one mixer, and the mixer's back end is connected to an optimization unit and then directly to the I / Q demodulator. The back ends of the service receiving unit and the TDM receiving unit are connected to the same modem via a channel, sending the service-I / Q output signal processed by the service receiving unit and the TDM-I / Q output signal processed by the TDM receiving unit to the modem. The modem has a first FPGA chip, which is connected to two sets of storage units. The two sets of storage units correspond one-to-one with the service-I / Q output signal and the TDM-I / Q output signal.

[0005] As a preferred embodiment of this utility model, the preamplifier unit includes a duplexer, the transmitting end of which is connected to the transmitting unit, the receiving end of which is connected to a first bandpass filter and then to a low-noise power amplifier, and the rear end of the low-noise power amplifier is connected to the receiver.

[0006] In a preferred embodiment of this invention, the service receiving unit includes a first AGC controller. The first AGC controller is connected to a first signal amplifier and then to a second surface acoustic wave (SAW) filter. The second SAW filter is connected to a first mixer. The first mixer is connected to a first crystal filter and then to the second AGC controller. The second AGC controller is connected to a second signal amplifier. The second signal amplifier is connected to a first I / Q demodulator. The first crystal filter, the second AGC controller, and the second signal amplifier together form a first optimization unit. The first I / Q demodulator is connected to a second bandpass filter. The second bandpass filter has a service-I output channel and a service-Q output channel at its end. A third AGC controller is connected between the service-I output channel and the service-Q output channel.

[0007] In a preferred embodiment of this invention, the TDM receiving unit includes a fourth AGC controller. The fourth AGC controller is connected to a third signal amplifier and then to a third surface acoustic wave (SAW) filter. The third SAW filter is connected to a second mixer. The second mixer is connected to a second crystal filter and then to a fifth AGC controller. The fifth AGC controller is connected to a fourth signal amplifier. The fourth signal amplifier is connected to a second I / Q demodulator. The second crystal filter, the fifth AGC controller, and the fourth signal amplifier together form a second optimization unit. The second I / Q demodulator is connected to a third bandpass filter. The third bandpass filter has a TDM-I output channel and a TDM-Q output channel. A sixth AGC controller is connected between the TDM-I output channel and the TDM-Q output channel.

[0008] In a preferred embodiment of this invention, the transmitting unit includes a transmitting control unit and a power amplifier. The power amplifier is connected to the preamplifier unit. The transmitting control unit includes a transmitting signal input terminal, an I / Q signal input terminal, and forward and reverse voltage input terminals of the power amplifier directional coupler. The transmitting signal input terminal is connected to an I / Q modulator and then to an electrically adjustable attenuator. The electrically adjustable attenuator is connected to a first amplification and filtering module and then to the power amplifier. The I / Q signal input terminal is connected to a second amplification and filtering module and then to the I / Q modulator and an arithmetic unit. The arithmetic unit is connected to an analog multiplier and then to a differential linear amplifier and a loop filter. The loop filter is connected to the electrically adjustable attenuator at its rear end. The analog multiplier is also connected to the monitoring interface module and the monitoring and protection module. The forward and reverse voltage input terminals of the power amplifier directional coupler are connected to the monitoring and protection module and the differential linear amplifier.

[0009] As a preferred embodiment of this utility model, the arithmetic unit includes a squarer, an adder, and a square root extractor.

[0010] As a preferred technical solution of this utility model, the first FPGA chip of the modem is connected to a first analog-to-digital conversion module, a second analog-to-digital conversion module and a digital-to-analog conversion module. The first analog-to-digital conversion module and the second analog-to-digital conversion module are each connected to a set of signal conditioning modules and then connected to the service receiving unit and the TDM receiving unit, respectively. The digital-to-analog conversion module is connected to a filtering and amplification module and then connected to the transmitting unit.

[0011] In a preferred embodiment of this invention, the monitoring interface module includes a control chip and a second FPGA chip. The control chip is connected to a vocoder and then to the second FPGA chip. Both the control chip and the second FPGA chip are connected to the modem. The control chip is also connected to the transmitting unit, the receiver, and the terminal device. A transceiver frequency synthesizer is connected between the transmitting unit and the receiver, and the transceiver frequency synthesizer is connected to the control chip.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model uses a power divider to split into two receiving channels to receive TDM broadcast signals and service signals respectively. Each receiving channel is equipped with a mixer, and the frequency is directly down-converted to the baseband after mixing, forming a single down-conversion + zero intermediate frequency demodulation scheme. Combined with RF, intermediate frequency, baseband filters and low noise power amplifiers, a large dynamic range can be obtained. When receiving large interference signals, the RF front-end is kept unobstructed, the noise figure is small, and the receiver has high sensitivity and a certain anti-interference capability. Attached Figure Description

[0013] Figure 1 This is a block diagram of the components of this utility model;

[0014] Figure 2 This is a block diagram of the front unit of this utility model;

[0015] Figure 3 This is a block diagram of the receiver link of this utility model;

[0016] Figure 4 This is a schematic diagram of the working principle of the launch control unit of this utility model;

[0017] Figure 5 This is a schematic diagram of the modem of this utility model;

[0018] Figure 6 This is a schematic diagram of the monitoring interface module of this utility model. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example 1

[0020] like Figures 1 to 6 As shown, this utility model discloses a UHF band satellite communication transceiver. The technical solution adopted includes a front-end unit, which includes a duplexer with a transmit port and a receive port and is connected to a communication antenna. The transmit port is connected to the power amplifier of the transmit unit, and the power amplifier is connected to the transmit control unit. The receive port is connected to a first bandpass filter, and the first bandpass filter is connected to an LNA (low noise power amplifier). The LNA is connected to a receiver.

[0021] like Figure 3As shown, the receiver includes a first surface acoustic wave (SAW) filter. A power divider is connected to the rear end of the first SAW filter. The power divider splits the signal into a service signal processing link and a TDM signal processing link, which are respectively a service receiving unit and a TDM receiving unit. The service receiving unit includes a first AGC controller, which is connected to a first signal amplifier and then to a second SAW filter. The second SAW filter is connected to a first mixer, which mixes in +7 ohms generated by LO1 (the first local oscillator). The first mixer has a local oscillator frequency of -5dBm. The first mixer is connected to a first crystal filter and then to a second AGC controller. The second AGC controller is connected to a second signal amplifier, which is connected to a first I / Q demodulator. Only one mixer is used. After downconversion by the mixer, the signal is subjected to interference suppression, level stabilization, and loss compensation by a first optimization unit composed of the first crystal filter, the second AGC controller, and the second signal amplifier. The signal is then directly fed into the first I / Q demodulator, forming a single downconversion + zero intermediate frequency demodulation scheme. In the first I / Q demodulator, the 140MHz, -5dBm local oscillator frequency generated by LO3 (the third local oscillator) is amplified and divided equally. The signals are then mixed in the in-phase branch and the quadrature branch mixers, respectively. The first I / Q demodulator is connected to a second bandpass filter. The second bandpass filter has a service-I output channel and a service-Q output channel. A third AGC controller is connected between the service-I output channel and the service-Q output channel. The VAGC1 voltage signal generated by the third AGC controller is applied to the first AGC controller and the second AGC controller.

[0022] Similarly, the TDM receiving unit includes a fourth AGC controller, which is connected to the third signal amplifier and then to the third surface acoustic wave (SAW) filter. The third SAW filter is connected to the second mixer, and the second mixer is connected to the second crystal filter and then to the fifth AGC controller. The fifth AGC controller is connected to the fourth signal amplifier, which is connected to the second I / Q demodulator. The second crystal filter, the fifth AGC controller, and the fourth signal amplifier together form the second optimization unit. The second I / Q demodulator is connected to the third bandpass filter, and the third bandpass filter has a TDM-I output channel and a TDM-Q output channel. A sixth AGC controller is connected between the TDM-I output channel and the TDM-Q output channel.

[0023] like Figure 4As shown, the transmit control unit includes a transmit signal input terminal, an I / Q signal input terminal, and forward and reverse voltage input terminals of the power amplifier directional coupler. The transmit signal input terminal is connected to the I / Q modulator and then to an electrically adjustable attenuator. The electrically adjustable attenuator is connected to the first amplification and filtering module and then to the power amplifier. The I / Q signal input terminal is connected to the second amplification and filtering module, and then to the I / Q modulator and the arithmetic logic unit (ALU). The ALU includes a squarer, an adder, and a square root extractor. The ALU is connected to an analog multiplier, then to a differential linear amplifier and a loop filter. The loop filter generates an ALC control voltage applied to the electrically adjustable attenuator. The analog multiplier is also connected to a monitoring interface module and a VSWR (voltage standing wave ratio) monitoring and protection module. The VSWR monitoring and protection module protects the circuit. The forward and reverse voltage input terminals of the power amplifier directional coupler are connected to the monitoring and protection module and the differential linear amplifier. A transmit / receive frequency synthesizer is connected between the transmit control unit and the receiver.

[0024] like Figure 5 As shown, the core unit of the modem is a first FPGA chip, which includes a baseband signal input terminal and a baseband signal output terminal. There are two baseband signal input terminals, corresponding to the service receiving unit and the TDM receiving unit, respectively. The output channels of each unit are connected to a signal conditioning module, and then connected to the baseband signal input terminal of the first FPGA chip via a first analog-to-digital converter (ADC) module and a second ADC module, respectively. The baseband signal output terminal is connected to an ADC module, and then to a filtering and amplification module. The filtering and amplification module is connected to the second amplification and filtering module of the transmit control unit via a channel. The first FPGA chip also has two sets of non-volatile memory cells. Each set of non-volatile memory cells includes a DSP (Digital Signal Processing) chip and a FLASH (Flash Memory) chip, corresponding to the service receiving unit and the TDM receiving unit, respectively. The modem mainly performs functions such as rate conversion of information stream, Turbo encoding and decoding, RS encoding and decoding, FEC convolutional encoding / VITERBI decoding, interleaving and deinterleaving, inserting CR, BTR, header and tail UW codes, π / 4-DQPSK baseband shaping, differential demodulation, DOPPLER frequency shift correction, frame header capture, bit synchronization capture, bit timing tracking, header and tail UW code detection, and generating transmit and receive clocks.

[0025] like Figure 6 As shown, the monitoring interface unit includes a control chip (CPU) and a second FPGA chip. The CPU and the second FPGA chip are connected via a vocoder. Both the CPU and the second FPGA chip are connected to the first FPGA chip of the modem. The CPU is also connected to a transmit control unit, a receiver, a transmit / receive frequency synthesizer, and two storage modules: RAM and FLASH.

[0026] The monitoring interface unit connects to terminal devices including handheld multifunction terminals and telephones. The CPU connects to the level conversion module and then to the handheld multifunction terminal. The CPU connects to the dialing detection chip and the user interface chip and then to the telephone.

[0027] The working principle of this utility model:

[0028] Voice or data signals undergo interface processing, data encoding, modulation, and digital-to-analog conversion (D / A) to form baseband signals. The transmit control unit modulates the baseband signal using DBPSK / DQPSK, amplifies the RF signal to an appropriate level, and sends it to the power amplifier unit. After amplification, it enters the preamplifier unit and is transmitted to the antenna through the antenna port of the band-stop duplexer. The antenna receives the signal relayed by the satellite and provides it to the receiver through the band-stop duplexer and bandpass filter in the preamplifier unit. After filtering by a low-noise amplifier (LNA) and a surface acoustic wave bandpass filter, the power divider splits the service signal and TDM signal into two separate paths for processing. LNA specifications: noise figure less than 2dB, gain greater than 30dB, maximum output power greater than 10dBm. Due to the large gain of the LNA, the equivalent noise figure of subsequent cascaded stages has a minimal impact on the overall noise figure of the device. This ensures high sensitivity and strong resistance to large signals.

[0029] The radio frequency signal is amplified, filtered, and controlled by AGC before being sent to the mixer, where it is mixed with the local oscillator signal generated by the local oscillator frequency to produce a 70MHz intermediate frequency signal. Then, the 70MHz intermediate frequency signal is filtered by a crystal filter to remove noise and controlled by AGC before entering the I / Q demodulation circuit. The I and Q signals demodulated by the I / Q demodulation circuit are amplified, and the I and Q signals received by the service are output to the modulator / demodulator after passing through a phase-flat low-pass filter with a cutoff frequency of 4.8kHz.

[0030] The I and Q signals received by the TDM are output to the modulator / demodulator after passing through a phase-flat low-pass filter with a cutoff frequency of 7.2kHz. The I and Q signals are then processed by the modulation / demodulation unit and the monitoring channel unit through sampling (A / D), demodulation, decoding, and other digital signal processing measures to restore the original voice or data, thus realizing voice, data, and short message communication.

[0031] This receiver employs six filters across three categories: an RF bandpass filter, an IF bandpass filter, and a baseband low-pass filter. The RF bandpass filter is a cavity filter with good linear phase, used to suppress transmit frequency, image signals, IF signals, and signals outside the receive band. Two surface acoustic wave (SAW) filters are cascaded, resulting in minimal group delay ripple. A bandpass filter serving the receive band further suppresses transmit frequency, image signals, IF signals, and signals outside the receive band. The received signal, after down-conversion, enters a narrowband crystal bandpass filter. This filter suppresses local oscillator leakage and other interference signals outside the IF band. After zero-IF demodulation by the LT5546, the 140MHz local oscillator signal is filtered by its built-in low-pass baseband filter, outputting clean I and Q baseband signals. These are then further filtered by the programmable filter MAX274 to obtain constant-amplitude I and Q baseband signals for data demodulation by the modem. The overall phase characteristic of the receiving channel is equivalent to the phase characteristics of the six cascaded filters.

[0032] Both the service reception unit and the TDM reception unit of the receiver employ a scheme of demodulation at the intermediate frequency (IF) after a single mixing operation. The satellite downlink signal received by the antenna passes through a duplexer and a bandpass filter, then enters a low-noise LNA for amplification and filtering. A power divider then splits the RF signal into two paths: one for the service reception channel and the other for the TDM reception channel. The circuitry for both channels is identical. The program for each channel is as follows: the RF signal, after amplification and filtering, is fed into a mixer and mixed with the local oscillator signal to generate the IF signal. Then, the intermediate frequency (IF) signal is filtered, controlled by AGC, and amplified to generate a -65dBm signal, which enters the zero-IF demodulation circuit. The zero-IF demodulation circuit uses a local oscillator signal divide-by-two configuration to reduce the DC bias of the I and Q signals due to local oscillator leakage. The I and Q signals demodulated by the IF demodulation circuit are amplified. The I and Q signals of the service receiving channel are output to the modulator / demodulator after passing through a phase-flat low-pass filter with a cutoff frequency of 4.8kHz; the I and Q signals of the TDM receiving channel are output to the modulator / demodulator after passing through a phase-flat low-pass filter with a cutoff frequency of 7.2kHz. Using a multiplier, the square root of the sum of the squares of the I and Q signal amplitudes is used as the received signal strength indicator, forming an AGC voltage forming circuit. This generates an AGC voltage, which is sent to the front-end AGC control circuit and the IF AGC control circuit to control the channel gain variation. The control range is over 60dB, thus ensuring that the amplitudes of the demodulated I and Q signals remain constant under different input signal amplitudes.

[0033] Gain Allocation: Based on the system's receiver specifications, the receiver's minimum input signal is -125dBm, and the interface level with the zero-IF demodulation circuit is -65dBm (the input level range of the zero-IF demodulation circuit is -76dBm to -19dBm). Considering a 10dB design margin, the gain from the input port to the zero-IF demodulation circuit input port is: G = -65 - (-125) + 10 = 70dB

[0034] Automatic Gain Control (AGC): According to the receiver's specifications, the receiver's automatic gain control (AGC) range is designed to be 60dB. The receiver's minimum input signal level Smin and maximum input signal level Smax are Smin = -125dBm and Smax = -65dBm, respectively. Therefore, the AGC control range of the entire system is: ΔAGC = Smax - Smin = -65 - (-125) = 60dB.

[0035] The AGC is controlled via RF, using an integrated circuit with a built-in PIN attenuation diode for two-stage control, with each stage having a control range of at least 30dB.

[0036] The circuits and mechanical connections involved in this utility model are common practices used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments. They are common knowledge.

[0037] Components not described in detail in this article are existing technologies.

[0038] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A UHF band satellite communication transceiver based on a front-end unit, said front-end unit is connected with a communication antenna, a receiver and a transmitting unit, said receiver and said transmitting unit are connected with a modem, said modem is connected with a monitoring interface module and a power supply, said monitoring interface module is connected with a terminal device, characterized in that: The receiver includes a service receiving unit and a TDM receiving unit, the receiving end of the pre-unit is connected to the first acoustic surface filter of the receiver, then connected to the power divider, the power divider is connected to the service receiving unit and the TDM receiving unit, both the service receiving unit and the TDM receiving unit have filters, mixers, I / Q demodulators and band pass filters, each of the mixers in the service receiving unit and the TDM receiving unit has one, and the end of the mixer is connected to the I / Q demodulator through the optimization unit; The service receiving unit and the TDM receiving unit are connected in the same modem through channels at the end, and the service-I / Q output signal processed by the service receiving unit and the TDM-I / Q output signal processed by the TDM receiving unit are sent into the modem; The modem has a first FPGA chip, and the first FPGA chip is connected with two groups of storage units, and the two groups of storage units correspond to the service-I / Q output signal and the TDM-I / Q output signal one by one.

2. A UHF band satellite communication transceiver as claimed in claim 1, characterized in that: The pre-unit includes a duplexer, the transmitting end of the duplexer is connected to the transmitting unit, the receiving end is connected to the first band pass filter, then connected to the low noise power amplifier, and the end of the low noise power amplifier is connected to the receiver.

3. The UHF band satellite communication transceiver of claim 1, wherein: The service receiving unit includes a first AGC controller, the first AGC controller is connected to the first signal amplifier, then connected to the second acoustic surface filter, the second acoustic surface filter is connected to the first mixer, the end of the first mixer is connected to the first crystal filter, then connected to the second AGC controller, the end of the second AGC controller is connected to the second signal amplifier, the second signal amplifier is connected to the first I / Q demodulator, the first I / Q demodulator is connected to the second band pass filter, the end of the second band pass filter has a service-I output channel and a service-Q output channel, and the third AGC controller is connected between the service-I output channel and the service-Q output channel.

4. The UHF band satellite communication transceiver of claim 1, wherein: The TDM receiving unit includes a fourth AGC controller, the fourth AGC controller is connected to the third signal amplifier, then connected to the third acoustic surface filter, the third acoustic surface filter is connected to the second mixer, the end of the second mixer is connected to the second crystal filter, then connected to the fifth AGC controller, the end of the fifth AGC controller is connected to the fourth signal amplifier, the fourth signal amplifier is connected to the second I / Q demodulator, the second I / Q demodulator is connected to the third band pass filter, the end of the third band pass filter has a TDM-I output channel and a TDM-Q output channel, and the sixth AGC controller is connected between the TDM-I output channel and the TDM-Q output channel.

5. The UHF band satellite communication transceiver of claim 1, wherein: The transmitting unit comprises a transmitting control unit and a power amplifier connected with the pre-stage unit, the transmitting control unit comprises a transmitting signal input end, an I / Q signal input end and a power amplifier directional coupler forward and reverse voltage input end, the transmitting signal input end is connected with an I / Q modulator, the I / Q modulator is connected with an electrically adjustable attenuator, the electrically adjustable attenuator is connected with a first amplification filter module, the first amplification filter module is connected with the power amplifier, the I / Q signal input end is connected with a second amplification filter module, the second amplification filter module is connected with the I / Q modulator and an operator respectively, the operator is connected with an analog multiplier, the analog multiplier is connected with a differential linear amplifier and a loop filter, the loop filter is connected with the electrically adjustable attenuator at the rear end, the analog multiplier is also connected with the monitoring interface module and a monitoring protection module, the power amplifier directional coupler forward and reverse voltage input end is connected with the monitoring protection module and the differential linear amplifier.

6. A UHF band satellite communication transceiver according to claim 5, characterised in that: The operator comprises a squarer, an adder and a square root extractor.

7. The UHF band satellite communication transceiver of claim 1, wherein: The first FPGA chip of the modem is connected with a first analog-digital conversion module, a second analog-digital conversion module and a digital-analog conversion module, the first analog-digital conversion module and the second analog-digital conversion module are each connected with a group of signal conditioning modules, and then connected with the service receiving unit and the TDM receiving unit respectively, and the digital-analog conversion module is connected with a filter amplification module, and then connected with the transmitting unit.

8. The UHF band satellite communication transceiver of claim 1, wherein: The monitoring interface module comprises a control chip and a second FPGA chip, the control chip is connected with a vocoder, and then connected with the second FPGA chip, and the control chip and the second FPGA chip are both connected with the modem; the control chip is also connected with the transmitting unit, the receiver and the terminal device, and a transceiving frequency synthesizer is connected between the transmitting unit and the receiver, and the transceiving frequency synthesizer is connected with the control chip.

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