X-band power amplifier system based on eight-port radio frequency pulse amplitude control microstrip network

Abstract

The application is based on an X-band power amplifier system of an eight-port radio frequency pulse amplitude control microstrip network, which is composed of a power amplifier driving and sampling comparison module, an eight-port radio frequency pulse amplitude control microstrip network module, a power amplifier module and a power amplifier control and power supply module; a linear frequency modulation pulse signal generated by a radar transmitter is input to the power amplifier driving and sampling comparison module, is amplified by the power amplifier module again through the eight-port radio frequency pulse amplitude control microstrip network module and is output; the power amplifier control and power supply module controls and supplies power to the whole system. The application embeds an eight-port radio frequency pulse amplitude control microstrip network in a radar power amplifier system, directly controls the amplitude of a radar radio frequency pulse envelope signal in a solid-state power amplifier, reduces the sidelobe amplitude of a pulse compression signal in a final receiver, improves the detection ability of a small target and the display effect of a radar echo, and reduces the cost and design complexity of a radar transmitter.

Description

Technical Field

[0001] This invention belongs to the field of X-band marine navigation solid-state pulse compression radar technology, specifically relating to a novel solid-state power amplification system with amplitude control over the radio frequency pulse envelope. Background Technology

[0002] Traditional marine navigation radars use a magnetron noncoherent system, which has a simple structure but suffers from the following drawbacks: the magnetron's peak transmission power reaches the kilowatt level, its lifespan is short, and it needs to be replaced regularly; the radar range resolution decreases as the radar detection range increases; the magnetron requires a warm-up time and cannot immediately enter the working state after the radar is started; the magnetron is a high-voltage device, which increases the maintenance risk.

[0003] As the cost of solid-state devices continues to decline, solid-state pulse compression technology will gradually become the future development direction for marine navigation radar. Solid-state pulse compression radar has advantages such as long service life, high reliability, low peak transmit power, range resolution that does not change with detection distance, and no warm-up time required.

[0004] To improve target range resolution, magnetron-based noncoherent navigation radars typically use pulse transformers to convert low-voltage narrow pulse signals into 8000V high-voltage narrow pulse signals, which are then modulated by the magnetron to generate radar radio frequency (RF) pulse signals with high peak power but very narrow pulse width. Solid-state pulse compression radars, on the other hand, amplify the wide-pulse linear frequency modulated (LFM) signal generated by the transmitter using a solid-state power amplifier before sending it as the radar RF signal to the antenna port. Upon receiving the target echo, the radar receiving system further compresses the echo signal using a matched filter, resulting in a narrow pulse signal compressed in the time domain. Research and experiments have shown that, for example, a 10µs pulse-width LFM signal generated by a solid-state pulse compression radar transmitter, after pulse compression by the radar receiver, results in a reduced pulse width. However, this compression simultaneously generates sidelobe waveforms around the main lobe. These sidelobe signals significantly impair the radar's ability to detect small targets near the sidelobes and also degrade the radar echo display quality.

[0005] Currently, the common method of windowing (weighting) matched filters effectively reduces sidelobe amplitude, but this also increases the main lobe width of the compressed pulse signal, thus reducing the radar's range resolution. Research has shown that changing the envelope shape of the radar RF pulse can effectively reduce sidelobe amplitude. Therefore, some high-end pulse compression radars typically use expensive direct digital frequency synthesizers (DDS) to control the amplitude of the RF pulse signal envelope, and then amplify the controlled signal using a solid-state power amplifier. Due to the cost sensitivity of marine navigation radar, finding a more cost-effective method to control the amplitude of the radar RF pulse envelope has become a key research focus. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing high-end pulse compression radar systems, which use expensive, complex, and difficult-to-design DDS to further suppress the sidelobes of the pulse-compressed waveform. This invention proposes a novel X-band solid-state power amplifier system with radio frequency pulse envelope amplitude control function to replace the traditional DDS approach, effectively reducing the cost and design complexity of the entire radar transmitter.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This X-band power amplifier system is based on an eight-port RF pulse amplitude control microstrip network. The system consists of a power amplifier driver and sampling comparison module, an eight-port RF pulse amplitude control microstrip network module, a power amplifier module, and a power amplifier control and power supply module. The linear frequency modulated pulse signal generated by the radar transmitter is input to the power amplifier driver and sampling comparison module, and then amplified and output by the power amplifier module after passing through the eight-port RF pulse amplitude control microstrip network module. The power amplifier control and power supply module controls and supplies power to the entire solid-state power amplifier system. The power amplifier driver and sampling comparison module mainly consists of a cascaded power amplifier, a power pulse control circuit, and a power sampling comparison circuit. The cascaded power amplifier is composed of a first-stage amplifier, a power divider, a parallel power amplifier, and a power combiner connected sequentially. The eight-port RF pulse... The amplitude control microstrip network module is controlled by the pulse envelope generation circuit from the power amplifier control and power supply module, thereby enabling amplitude control of the envelope of the input radar transmitted linear frequency modulated signal. The power amplifier module consists of a power amplifier circuit connected to a gate pulse control circuit, a drain pulse control circuit, a power monitoring circuit, a temperature monitoring circuit, and an adaptive gain adjustment control circuit. The power amplifier control and power supply module consists of a power conversion circuit, a pulse control circuit, a pulse envelope generation circuit, an eight-port RF pulse amplitude control microstrip network driver circuit, and a power monitoring sampling circuit. Its main functions are to provide the various voltages required for the operation of the other three modules, generate various synchronous pulse control signals and envelope amplitude control signals, and check the operating temperature and output power of each power amplifier in real time to ensure the normal operation of the entire system.

[0009] In the preferred embodiment, the first stage of the cascaded power amplifier in the power amplification drive and sampling comparison module uses two series-connected transistor amplifiers. The amplified signal is then evenly distributed by an RF power divider before being input to a parallel power amplifier. Finally, the parallel amplified signal is output from the power combiner to the eight-port RF pulse amplitude control microstrip network module via an RF power combiner. The power sampling comparison circuit uses a 15dB microstrip coupling circuit to couple out part of the output power. The coupled signal is converted into a DC level signal after passing through an RF detector and an RF diode. This DC signal is compared with a reference voltage by an integrated operational amplifier before being output. If the amplitude of the detected DC signal is less than that of the reference signal, it indicates that the output power has not met the design specifications. The power pulse control circuit is mainly used to control the power supply of the cascaded power amplifier. The power pulse control circuit only enables the cascaded power amplifier to work when the linear frequency modulated pulse signal generated by the radar transmitter arrives; otherwise, the power supply is cut off.

[0010] In the preferred embodiment, the eight-port RF pulse amplitude control microstrip network module employs a ring connection of four 90-degree RF microstrip hybrid couplers. The left and right 90-degree hybrid couplers serve as the input and output terminals for the RF transmission signal, respectively, while the upper and lower 90-degree hybrid couplers act as matching or reflection terminals for the RF transmission signal. By adding varactor diodes, inductors, and resistors to the through and coupling terminals of the upper and lower 90-degree hybrid couplers, and controlling the control voltage of the varactor diodes, the upper and lower 90-degree hybrid couplers exhibit different power reflection characteristics. When the control voltage is high, the capacitance of the varactor diode decreases, the impedance to the RF signal increases, and the reflection is strengthened. This allows the input RF signal to be reflected back from the upper and lower 90-degree hybrid couplers, and then synthesized and output through the rightmost 90-degree hybrid coupler. When the voltage signal controlling the varactor diode decreases, the capacitance of the varactor diode increases, and the effective impedance decreases. Since a matching resistor is used after the varactor diode, the input RF signal is mainly transmitted to the load impedance through the upper and lower 90-degree hybrid couplers, while the signal synthesized through the rightmost 90-degree hybrid coupler will experience significant attenuation. By controlling the magnitude of the voltage signal on the varactor diode, the amplitude of the output signal envelope can be effectively adjusted, thereby achieving control over the amplitude of the RF transmit pulse envelope.

[0011] The preferred embodiment of the power amplifier module mainly consists of a power amplifier circuit, a gate pulse control circuit, a drain pulse control circuit, a power monitoring circuit, a temperature monitoring circuit, and an adaptive gain adjustment control circuit. The power amplifier circuit uses a domestically produced power amplifier chip with a gain of 28dB and an output compression point of 25W per 1dB. The gate pulse control circuit and the drain pulse control circuit control the conduction time of the power amplifier. The power-on process of the power amplifier involves the gate control level first changing from low to high, followed by the drain control level changing from low to high. The power-off sequence involves the gate control level first changing from high to low, followed by the drain control level changing from high to low. The temperature monitoring circuit uses a temperature sensor chip to test the power output in real time. The operating temperature of the power amplifier is transmitted to the power amplifier control and power supply module. When the operating temperature exceeds the rated operating temperature, the amplifier control and power supply module will directly remove the gate and drain voltages of the power amplifier to protect it from burnout. When the temperature changes slightly, the adaptive gain adjustment control circuit will control the gain of the power amplifier to ensure normal operation. The power monitoring circuit uses an RF microstrip coupling circuit. Since the output power of the power amplifier is relatively large, the isolation terminal of the coupling circuit is used as the output terminal. Then, after detection and rectification by the RF detector diode, a DC level representing the power level is obtained. This DC level is digitally sampled by the power monitoring sampling circuit in the power amplifier control and power supply module.

[0012] In the preferred embodiment, the power amplifier control and power supply module is the control center and power supply core of the entire solid-state power amplifier system. It mainly consists of a power conversion circuit, a pulse control circuit, a pulse envelope generation circuit, an eight-port RF pulse amplitude control microstrip network driver circuit, and a power monitoring and sampling circuit. The power conversion circuit uses multiple voltage conversion chips to generate the various supply voltages required for the normal operation of the other three modules. The pulse control circuit uses a field-programmable logic array (FPGA) chip to generate pulse control signals that meet various timing requirements. These signals are used to control the power supply of the cascaded power amplifiers in the power amplifier driver and sampling comparison modules, and to generate the timing control logic required for the gate and drain pulse control circuits in the power amplifier module. It is also used to generate the amplitude information parameters required by the pulse envelope generation circuit. The pulse envelope generation circuit mainly generates the amplitude signal for controlling the eight-port RF pulse amplitude control microstrip network. This amplitude signal is generated through a digital-to-analog converter chip. The generated pulse amplitude signal is amplified and amplitude-adjusted by the eight-port RF pulse amplitude control microstrip network driver circuit before controlling the eight-port RF pulse amplitude control microstrip network module. The power monitoring and sampling circuit mainly consists of an analog-to-digital converter sampling chip, used to sample the DC level coupled from the solid-state amplifier.

[0013] The beneficial effects of this invention are:

[0014] 1. This invention is a novel X-band solid-state power amplifier system with radio frequency pulse envelope amplitude control function. An eight-port radio frequency pulse amplitude control microstrip network is embedded in the radar power amplifier system, thereby directly controlling the amplitude of the radar radio frequency pulse envelope signal in the solid-state power amplifier. This further reduces the sidelobe amplitude of the pulse compression signal in the final receiver, thereby improving the radar's ability to detect small targets, improving the display effect of radar echo, and effectively reducing the cost and design complexity of the entire radar transmitter.

[0015] 2. The power amplifier control and power supply module are used to control the power supply of the cascaded power amplifier. When there is no radio frequency pulse input signal, the power supply of the cascaded power amplifier is turned off, thereby reducing the power consumption of the cascaded power amplifier.

[0016] 3. Pulse control was applied to both the gate and drain of the power amplifier circuit, thereby reducing the power consumption of the power amplifier module;

[0017] 4. The operating temperature of the power amplifier can be monitored in real time by a temperature sensor to ensure that the power amplifier operates within the rated operating temperature range.

[0018] 5. When the operating temperature of the power amplifier changes, the gate bias voltage of the power amplifier is automatically changed through the adaptive gain adjustment circuit to ensure the stable operation of the entire amplifier. Attached Figure Description

[0019] Figure 1 This is a block diagram of an X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network.

[0020] Figure 2 A schematic diagram of an X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network;

[0021] Figure 3 A schematic diagram of a 10µs pulse width linear frequency modulated signal generated by a solid-state pulse compression radar transmitter after pulse envelope control.

[0022] Figure 4 This is a schematic diagram of the pulse compression waveform after envelope modulation.

[0023] Figure 5 A schematic diagram of a 10µs pulse width linear frequency modulated signal generated by a solid-state pulse compression radar transmitter;

[0024] Figure 6 This is a schematic diagram of the waveform after pulse compression.

[0025] In the diagram: 1. Power amplifier drive and sampling comparison module; 2. Eight-port RF pulse amplitude control microstrip network module; 3. Power amplifier module; 4. Power amplifier control and power supply module; 5. Cascaded power amplifier; 6. Power pulse control circuit; 7. Power sampling comparison circuit; 8. First-stage amplifier; 9. Power divider; 10. Parallel power amplifier; 11. Power combiner; 12. Power conversion circuit; 13. Pulse control circuit; 14. Pulse envelope generation circuit; 15. Eight-port RF pulse amplitude control microstrip network drive circuit; 16. Power monitoring sampling circuit; 17. Gate pulse control circuit; 18. Drain pulse control circuit; 19. Power amplifier circuit; 20. Power monitoring circuit; 21. Temperature monitoring circuit; 22. Adaptive gain adjustment control circuit. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0027] Example: An X-band power amplification system using a radio frequency pulse amplitude control (RF pulse amplitude control) microstrip network. This system comprises a power amplification driver and sampling comparison module 1, an eight-port RF pulse amplitude control microstrip network module 2, a power amplification module 3, and a power amplification control and power supply module 4. The linear frequency modulated pulse signal generated by the radar transmitter is input to the power amplification driver and sampling comparison module 1, and then amplified and output by the power amplification module 3 via the eight-port RF pulse amplitude control microstrip network module 2. (See [link to example]). Figure 1 .

[0028] The power amplifier drive and sampling comparison module 1 is mainly composed of a cascaded power amplifier 5, a power pulse control circuit 6, and a power sampling comparison circuit 7. The cascaded power amplifier 5 is composed of a first-stage amplifier 8, a power divider 9, a parallel power amplifier 10, and a power combiner 11 connected in sequence. Its main function is to amplify the linear frequency modulated pulse signal generated by the radar transmitter and monitor whether the amplitude of the input signal meets the design requirements. At the same time, the power supply of the cascaded power amplifier 5 is also controlled by the power amplifier control and the power module 4. When there is no radio frequency pulse input signal, the power supply of the cascaded power amplifier 5 is turned off, thereby reducing the power loss of the power amplifier.

[0029] To achieve a total gain of 25dB and an output compression point of 200mW, the first stage amplifier 8 of the cascaded power amplifier 5 in the power amplifier drive and sampling comparison module 1 uses two series-connected transistor amplifiers. The amplified signal is then evenly distributed by the RF power divider 9 before being input to the parallel power amplifier 10. Finally, the parallel amplified signal is output by the RF power combiner 11 to the eight-port RF pulse amplitude control microstrip network module 2. The power sampling comparison circuit 7 uses a 15dB microstrip coupling circuit to couple out part of the output power. The coupled signal is converted into a DC level signal after passing through an RF detector and RF diode. This DC signal is compared with a reference voltage by an integrated operational amplifier and then output. If the amplitude of the detected DC signal is less than that of the reference signal, it indicates that the output power has not met the design specifications. The amplifier design is based on the S-parameter models of each amplifier, combined with precise software simulation, and uses microstrip line matching to achieve conjugate impedance matching between each stage of the amplifier, thereby maximizing the power transfer gain of the cascaded power amplifier.

[0030] The power amplifier control and power supply module 4 consists of a power conversion circuit 12, a pulse control circuit 13, a pulse envelope generation circuit 14, an eight-port RF pulse amplitude control microstrip network driver circuit 15, and a power monitoring and sampling circuit 16. Its main functions are to provide the other three modules with the necessary voltages, generate various synchronous pulse control signals and envelope amplitude control signals, and monitor the operating temperature and output power of each power amplifier in real time to ensure the normal operation of the entire system. The power amplifier control and power supply module 4 is the control center and power supply core of the entire solid-state power amplifier system.

[0031] In the power amplifier control and power supply module 4, the power pulse control circuit 13 is mainly used to control the power supply of the cascaded power amplifier 5. The power pulse control circuit 13 only enables the cascaded power amplifier 5 to work when the linear frequency modulation pulse signal generated by the radar transmitter arrives. At other times, the power supply is cut off, thereby reducing the power consumption of the entire module and improving the efficiency of the cascaded power amplifier 5.

[0032] The power conversion circuit 12 uses multiple voltage conversion chips to generate various power supply voltages required for the normal operation of the other three modules. The pulse control circuit 13 uses a field-programmable logic array chip to generate pulse control signals that meet various timing requirements. These signals are used to control the power supply of the cascaded power amplifier 5 in the power amplifier drive and sampling comparison module 1, and to generate the timing control logic required by the gate pulse control circuit 17 and the drain pulse control circuit 18 in the power amplifier module 3. It is also used to generate the amplitude information parameters required by the pulse envelope generation circuit 14. The pulse envelope generation circuit 14 is mainly used to generate the amplitude signal controlling the eight-port RF pulse amplitude control microstrip network. This amplitude signal is generated by a digital-to-analog converter chip. The generated pulse amplitude signal is amplified and amplitude-adjusted by the eight-port RF pulse amplitude control microstrip network drive circuit 15 before controlling the eight-port RF pulse amplitude control microstrip network module 2. The power monitoring sampling circuit 16 mainly consists of an analog-to-digital conversion sampling chip, used to sample the DC level coupled from the solid-state amplifier.

[0033] The eight-port RF pulse amplitude control microstrip network module 2 is controlled by the pulse envelope generation circuit 14 from the power amplifier control and power supply module 4, thereby enabling amplitude control of the envelope of the input radar transmitted linear frequency modulated signal. The eight-port RF pulse amplitude control microstrip network module 2 employs a ring connection of four 90-degree RF microstrip hybrid couplers. The left and right 90-degree hybrid couplers serve as the input and output terminals of the RF transmitted signal, respectively, while the upper and lower 90-degree hybrid couplers serve as the matching or reflection terminals of the RF transmitted signal. By adding varactor diodes, inductors, and resistors to the through and coupling terminals of the upper and lower 90-degree hybrid couplers, and controlling the control voltage of the varactor diodes, the upper and lower 90-degree hybrid couplers exhibit different power reflection states. When the control voltage is... When the voltage across the varactor diode is high, the capacitance decreases, increasing the impedance to the RF signal and strengthening reflection. This causes the input RF signal to be reflected back from the upper and lower 90-degree hybrid couplers, and then synthesized by the rightmost 90-degree hybrid coupler before being output. When the voltage signal controlling the varactor diode decreases, the capacitance increases, reducing the effective impedance. Since a matching resistor is used after the varactor diode, the input RF signal is mainly transmitted to the load impedance through the upper and lower 90-degree hybrid couplers, while the signal synthesized by the rightmost 90-degree hybrid coupler experiences significant attenuation. By controlling the voltage signal across the varactor diode, the amplitude of the output signal envelope can be effectively adjusted, thus controlling the amplitude of the RF transmit pulse envelope.

[0034] The power amplifier module 3 is composed of a power amplifier circuit 19, a gate pulse control circuit 17, a drain pulse control circuit 18, a power monitoring circuit 20, a temperature monitoring circuit 21, and an adaptive gain adjustment control circuit 22. The power amplifier circuit 19 in the power amplifier module 3 uses a domestically produced power amplifier chip with a gain of 28dB and an output 1dB compression point of 25W. To ensure the stability of the power amplifier during operation, after designing the DC bias RF microstrip circuit of the power amplifier circuit 19, the S-parameters of the power amplifier chip are measured using a Keysight 5222 network analyzer. Then, port extension matching is used to obtain the optimal input and output matching parameters of the power amplifier chip. Based on these parameters, the input and output microstrip matching circuits of the power amplifier are designed to achieve the best power amplification effect. The power-on process of the power amplifier circuit 19 is as follows: the gate control level first changes from low to high, and then the drain control level changes from low to high. The cutoff sequence of the power amplifier circuit 19 is as follows: the gate control level first changes from high to low, and then the drain control level changes from high to low again.

[0035] The temperature monitoring circuit 21 in the power amplifier module 3 uses a temperature sensing chip to test the operating temperature of the power amplifier circuit 19 in real time and transmit it to the power amplifier control and power supply module 4. When the operating temperature exceeds the rated operating temperature, the power amplifier control and power supply module 4 will directly remove the gate and drain voltages of the power amplifier to protect the power amplifier from being burned out. When the temperature changes slightly, the adaptive gain adjustment control circuit 22 will control the gain of the power amplifier to ensure that the power amplifier circuit 19 works normally.

[0036] The power monitoring circuit 20 in the power amplifier module 3 also uses an RF microstrip coupling circuit. Since the output power of the power amplifier circuit 19 is relatively large, the isolation terminal of the coupling circuit is used as the output terminal. Then, after detection and rectification by the RF detector diode, a DC level representing the power level is obtained. This DC level is digitally sampled by the power monitoring sampling circuit 16 in the power amplifier control and power supply module 4.

[0037] Figure 2 A schematic diagram of the physical layout of this embodiment is shown. The first stage of the cascaded power amplifier 5 in the power amplification drive and sampling comparison module 1 uses a Qorvo NLB400 broadband gallium arsenide amplifier. The output of the NLB400 amplifier is evenly distributed to two parallel paths via a 90-degree microstrip hybrid coupler. On each parallel path, two series-connected Infineon BFP650F amplifiers further amplify the power. Finally, the power from the two parallel paths is combined and output via a 90-degree hybrid coupler. To monitor whether the output power meets the design specifications, a portion of the output power is coupled out using a 15dB attenuation microstrip coupler. The DC component is removed by a capacitor, and the DC amplitude information of the coupled signal is extracted by a Skyworks SC-79 RF detector diode. The obtained DC amplitude and reference amplitude are then compared and output. If the coupled DC amplitude is greater than the reference voltage, it indicates that the output signal power meets the design specifications. To reduce the power consumption of the power amplifier drive and sampling / comparison modules, each stage of the amplifier uses a mirrored current source for power supply. Furthermore, the reference voltage of the mirrored power supply requires a PNP transistor BC857 to actually provide power. The collector of the BC857 is controlled by the pulse control circuit 13 from the power amplifier control and power supply module 4. When the radio frequency linear frequency modulated pulse signal generated by the radar transmitter arrives, the pulse control circuit 13 generates a synchronization pulse control signal, giving the collector of the BC857 a high level, causing the BC857 to conduct and thus starting the cascaded power amplifier 5. When the radio frequency linear frequency modulated signal ends, the pulse control signal also goes low, causing the entire cascaded power amplifier to stop working. This reduces the power consumption of the entire module and improves the efficiency of the cascaded power amplifier.

[0038] After being amplified by the cascaded power amplifier 5, the RF linear frequency modulated signal enters the eight-port RF pulse amplitude control microstrip network module 2, which consists of four 90-degree microstrip hybrid couplers connected in a ring. The RF signal is input from the left coupler, whose isolation terminal is connected to two parallel 100-ohm resistors in a T-connection. This reduces the mutual coupling of the inductors in the resistors at the RF level, making the two 100-ohm parallel resistors approach a 50-ohm matching value. The input RF signal passes through the through-terminal and coupling terminal, respectively, and enters the upper and lower 90-degree microstrip couplers. Both the through-terminal and coupling terminals of the upper and lower couplers are connected in series with varactor diodes, inductors, and 50-ohm resistors. The varactor diode is controlled by an amplitude modulation signal from the eight-port pulse amplitude control network drive circuit. When the modulation voltage increases, the capacitance of the varactor diode decreases, and its impedance increases. This causes the RF signals transmitted to the coupling and through terminals to be reflected back. The reflected signals are then combined at the original isolation terminals for output. The signals at the isolation terminals of the upper and lower 90-degree microstrip hybrid couplers are then combined again through the right-side 90-degree hybrid coupler before being output. Since the equivalent impedance of the varactor diode can be controlled by different amplitude control voltages, the final eight-port output power can be changed. The dynamic range of the eight-port RF pulse amplitude control microstrip network module 2 can reach 25dB. This allows for effective amplitude control of the envelope of the transmitted frequency-modulated continuous wave signal.

[0039] The transmitted RF-modulated continuous wave signal enters the power amplifier module 3 after passing through an eight-port RF pulse amplitude control microstrip network. It is then amplified by a domestically produced power amplifier chip with a 1dB compression point of 25 watts and a gain of 28dB before being output. To monitor the output power, a portion of the output power is coupled out through the isolation terminal of a 20dB microstrip coupler. After the DC component is removed by an RF capacitor, it is converted to DC level by an Sc-97 RF detector diode circuit. The output DC level is amplified by an integrated operational amplifier and sampled by the power monitoring circuit in the power amplifier control and power supply module 4. To ensure the normal operation of the power amplifier, a Texas Instruments LM74CIM-5 temperature sensor is incorporated. The temperature sensor is positioned below the power amplifier. When the power amplifier exceeds its rated operating temperature, the power amplifier control and power supply module 4 generates a control signal to directly cut off the power supply voltage to the power amplifier. To overcome the characteristic that the power amplifier's threshold decreases with increasing temperature, an adaptive gain adjustment control circuit 22 appropriately reduces the bias voltage of the power amplifier's gate when the temperature rises. The adaptive gain adjustment control circuit 22 is mainly based on a forward amplifier circuit composed of an integrated operational amplifier and a negative temperature coefficient thermistor. When the temperature rises, the resistance of the thermistor decreases, the gain of the forward amplifier decreases, and thus the gate voltage decreases accordingly. To reduce the power consumption of the entire power amplifier module, a push-pull circuit is used to implement the gate and drain pulse control circuit. The control of the push-pull circuit comes from the pulse control circuit of the power amplifier and power supply module.

[0040] The power conversion circuit 12 in the power amplifier control and power supply module 4 uses multiple power conversion chips to generate the power supply voltage required by other modules. The pulse control circuit 13 uses a Xilinx Field Programmable Array (FPGA) to synchronously generate the timing control pulses required by each module based on the radar transmitter's trigger signal, used to control the operating state of each module's amplifier. Furthermore, the FPGA controls an Analog-to-digital converter (ADI) AD9705 to generate a pulse envelope amplitude control signal. This signal is amplified and voltage-adjusted by an integrated operational amplifier before being sent to the eight-port RF pulse amplitude control microstrip network module 2 to control the amplitude of the RF pulse. Simultaneously, the power monitoring and sampling circuit 16 uses an ADI high-speed analog-to-digital converter (ADI) AD9609 to sample the DC signal coupled from the power amplifier in real time.

[0041] Depend on Figure 3 and Figure 4 It can be seen that by using the amplitude control of the eight-port RF pulse amplitude control microstrip network, the sidelobe amplitude of the pulse-compressed waveform is reduced from 0.12 to 0.09, a decrease of 37%. This effectively suppresses the sidelobe amplitude.

[0042] In contrast. Figure 5 and Figure 6 This demonstrates the signal characteristics received by existing radar technologies. Figure 5 This is a 10µs pulse width linear frequency modulated signal generated by a solid-state pulse compression radar transmitter. Figure 6 This is the waveform after the radar receiver compresses the echo signal pulses. Figure 6 It is known that the pulse width of the signal received by the radar in the existing technology is reduced after pulse compression, but at the same time, side lobe waveforms are generated around the main lobe waveform. This side lobe signal will greatly affect the radar's ability to detect small targets near the side lobe, and will also make the radar echo display effect worse.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network, characterized in that, The system consists of a power amplifier drive and sampling comparison module, an eight-port RF pulse amplitude control microstrip network module, a power amplifier module, and a power amplifier control and power supply module. The linear frequency modulated pulse signal generated by the radar transmitter is input to the power amplifier drive and sampling comparison module, and then amplified and output by the power amplifier module after passing through the eight-port RF pulse amplitude control microstrip network module. The power amplifier control and power supply module controls and supplies power to the entire solid-state power amplifier system. The power amplifier drive and sampling comparison module mainly consists of a cascaded power amplifier, a power pulse control circuit, and a power sampling comparison circuit. The cascaded power amplifier is composed of a first-stage amplifier, a power divider, a parallel power amplifier, and a power combiner connected sequentially. The eight-port RF pulse amplitude control microstrip network module receives the signal from the power amplifier drive and sampling comparison module. The power amplifier control and power supply module's pulse envelope generation circuit controls the amplitude of the input radar transmitted linear frequency modulated signal's envelope. The power amplifier module consists of a power amplifier circuit connected to a gate pulse control circuit, a drain pulse control circuit, a power monitoring circuit, a temperature monitoring circuit, and an adaptive gain adjustment control circuit. The power amplifier control and power supply module consists of a power conversion circuit, a pulse control circuit, a pulse envelope generation circuit, an eight-port RF pulse amplitude control microstrip network driver circuit, and a power monitoring sampling circuit. Its main functions are to provide the other three modules with the various voltages required for operation, generate various synchronous pulse control signals and envelope amplitude control signals, and check the operating temperature and output power of each power amplifier in real time to ensure the normal operation of the entire system.

2. The X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network according to claim 1, characterized in that, The cascaded power amplifier in the power amplification drive and sampling comparison module uses two series-connected transistor amplifiers in the first stage. The amplified signal is then evenly distributed by an RF power divider before being input to a parallel power amplifier. Finally, the parallel amplified signal is output from the power combiner to the eight-port RF pulse amplitude control microstrip network module via an RF power combiner. The power sampling comparison circuit uses a 15dB microstrip coupling circuit to couple out part of the output power. The coupled signal is converted into a DC level signal by an RF detector and an RF diode. This DC signal is compared with a reference voltage by an integrated operational amplifier and then output. If the amplitude of the detected DC signal is less than that of the reference signal, it indicates that the output power has not met the design specifications. The power pulse control circuit is mainly used to control the power supply of the cascaded power amplifier. The power pulse control circuit only enables the cascaded power amplifier to work when the linear frequency modulated pulse signal generated by the radar transmitter arrives; otherwise, the power supply is cut off.

3. The X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network according to claim 1 or 2, characterized in that, The eight-port RF pulse amplitude control microstrip network module employs a ring connection of four 90-degree RF microstrip hybrid couplers. The left and right 90-degree hybrid couplers serve as the input and output terminals for the RF transmission signal, respectively, while the upper and lower 90-degree hybrid couplers act as matching or reflection terminals for the RF transmission signal. By adding varactor diodes, inductors, and resistors to the through and coupling terminals of the upper and lower 90-degree hybrid couplers, and controlling the control voltage of the varactor diodes, the upper and lower 90-degree hybrid couplers exhibit different power reflection characteristics. When the control voltage is high, the capacitance of the varactor diode decreases, the impedance to the RF signal increases, and the reflection is strengthened. The input RF signal is reflected back from the upper and lower 90-degree hybrid couplers, and then synthesized by the rightmost 90-degree hybrid coupler before being output. When the voltage signal controlling the varactor diode decreases, the capacitance of the varactor diode increases, and the effective impedance decreases. Since a matching resistor is used after the varactor diode, the input RF signal is mainly transmitted to the load impedance through the upper and lower 90-degree hybrid couplers, while the signal synthesized by the rightmost 90-degree hybrid coupler will experience significant attenuation. By controlling the magnitude of the voltage signal on the varactor diode, the amplitude of the output signal envelope can be effectively adjusted, thereby achieving control of the RF transmit pulse envelope amplitude.

4. The X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network according to claim 3, characterized in that, The power amplifier module mainly consists of a power amplifier circuit, a gate pulse control circuit, a drain pulse control circuit, a power monitoring circuit, a temperature monitoring circuit, and an adaptive gain adjustment control circuit. The power amplifier circuit uses a domestically produced power amplifier chip with a gain of 28dB and an output compression point of 25W at 1dB. The gate pulse control circuit and the drain pulse control circuit control the power amplifier's on-time. During power-on, the gate control level first changes from low to high, followed by the drain control level. The power amplifier's off-time sequence is as follows: the gate control level first changes from high to low, followed by the drain control level. The temperature monitoring circuit uses a temperature sensor chip to monitor the power amplifier in real time. The amplifier's operating temperature is transmitted to the power amplifier control and power supply module. When the operating temperature exceeds the rated operating temperature, the amplifier control and power supply module will directly remove the gate and drain voltages of the power amplifier to protect it from burnout. When the temperature changes slightly, the adaptive gain adjustment control circuit will control the gain of the power amplifier to ensure normal operation. The power monitoring circuit uses an RF microstrip coupling circuit. Since the power amplifier has a large output power, the isolation terminal of the coupling circuit is used as the output terminal. Then, after detection and rectification by an RF detector diode, a DC level representing the power level is obtained. This DC level is digitally sampled by the power monitoring sampling circuit in the power amplifier control and power supply module.

5. The X-band power amplifier system based on an eight-port RF pulse amplitude control microstrip network according to claim 4, characterized in that, The power amplifier control and power supply module is the control center and power supply core of the entire solid-state power amplifier system. It mainly consists of a power conversion circuit, a pulse control circuit, a pulse envelope generation circuit, an eight-port RF pulse amplitude control microstrip network driver circuit, and a power monitoring and sampling circuit. The power conversion circuit uses multiple voltage conversion chips to generate various supply voltages required for the normal operation of the other three modules. The pulse control circuit uses a field-programmable logic array chip to generate pulse control signals that meet various timing requirements. It is used to control the power supply of the cascaded power amplifier in the power amplifier drive and sampling comparison module, and to generate the timing control logic required for the gate and drain pulse control circuits in the power amplifier module. In addition, it is also used to generate the amplitude information parameters required by the pulse envelope generation circuit. The pulse envelope generation circuit is mainly used to generate the amplitude signal for controlling the eight-port RF pulse amplitude control microstrip network. This amplitude signal is generated by a digital-to-analog converter chip. The generated pulse amplitude signal is amplified and amplitude-adjusted by the eight-port RF pulse amplitude control microstrip network driver circuit before controlling the eight-port RF pulse amplitude control microstrip network module. The power monitoring sampling circuit is mainly composed of an analog-to-digital conversion sampling chip, which is used to sample the DC level coupled out of the solid-state amplifier.

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