| With the rapid development of information technology and aerospace technology,countries around the world have realized the strategic importance and great commercial value of establishing an autonomous and controllable global satellite communication network.The microwave radar transmission link in the satellite communication system is the core component to realize the data transmission between the satellite and the earth.Its stability and high reliability are very important for the normal operation of the whole satellite communication system.In the dissertation,the key technologies of spaceborne microwave radar transmitting link are studied in combination with practical engineering applications.The stability and reliability of the key components of the transmitting link-coaxial dielectric frequency source,power amplifier and power detection circuit are designed and implemented.Through in-depth research,the main achievements of the dissertation are as follows:1.Aiming at the problems of weak spurious signal suppression ability,large spurious signal interference,miniaturization and environmental adaptability of frequency source,a method of integrated design of microstrip line filter is proposed to realize spurious suppression.A C-band miniaturized coaxial dielectric frequency source is designed and verified by experiments.Compared with the frequency source without spurious suppression,the spurious suppression depth of the frequency source with spurious suppression is optimized by 5 d B by filter integration.The test results show that the frequency source output power≥10 d Bm,clutter suppression≥70 d Bc,harmonic suppression≥30 d Bc,vibration phase noise deterioration(@0.06g~2/Hz)≤5 d B and other key indicators meet the engineering application development goals.2.Aiming at the problems of high complexity of broadband matching and large gain fluctuation,the simplified real frequency technology is used to synthesize the broadband matching network,and the improved particle swarm optimization algorithm is introduced to optimize the impedance function,which improves the efficiency of power transmission of power amplifier and the stability of power output.Three initial values are introduced by chaotic mapping,and the dynamic adaptive parameter adjustment algorithm is used to optimize.When the error of the three optimization results is less than the preset amount(2%),the function optimization is completed.The algorithm reduces the probability that the traditional particle algorithm is easy to converge to the local minimum.The feasibility and effectiveness of the proposed design method are verified by an engineering application example of a 4-6 GHz broadband power amplifier.The test results show that in the operating frequency band,the output power is about 39.5 d Bm,the power added efficiency is between 61.1%and 72.4%,and the gain is between 13-17 d B.3.The automatic gain control circuit is designed to realize the gain control and temperature control of the power amplifier,so as to ensure that the power amplifier can achieve stable output performance under the condition of temperature disturbance,which solves the problem of low stability of output performance of traditional power amplifier in spaceborne environment.The test results show that in the whole working frequency band,the output power fluctuation caused by the input power fluctuation of the front stage or the temperature drift of the power amplifier can automatically control the output power of the power amplifier by controlling the attenuation of the adjustable attenuator to ensure the stable output of the power amplifier.Under high and low temperature working conditions,the output power changes between 33.68d Bm～34.46d Bm,and the flatness of the system output power is better.The variation range is△=0.78d B,which meets the design requirements of high power and stable output at the transmitter.4.Optimized design and completed the production of a miniaturized broadband power detection circuit.the equivalent circuit model of planar Schottky diode is designed,and the wideband equalization matching network is constructed to design and simulate the detection circuit of Schottky diode.Aiming at the problem that the Schottky diode matching circuit is greatly affected by the process,a gain equalization optimization technology based on Ta N thin film resistor is developed.Through the optimization of sputtering process and etching process,the problem of poor detection flatness caused by low resistance accuracy and large temperature characteristics in full temperature environment in the integration of Ta N thin film resistor and Schottky diode is solved,and the fluctuation of output voltage of Schottky diode detection circuit is reduced.The test results show that the flatness index of the miniaturized broadband power detection circuit is optimized.The flatness of the detection is optimized to 2.4d B in the 0.1GHz～8GHz band,2.1d B in the 8GHz～18GHz band,2.3d B in the 18GHz～26.5GHz band,and 4.8d B in the 26.5GHz～40GHz band.It basically covers the frequency band application of microwave system power detection.5.Aiming at the environmental adaptability of microwave devices onboard,the anti-radiation test of microwave power detection circuit devices was carried out,and the electrical parameters and anti-radiation test verification of microwave devices were completed.The experimental results show that the functional parameters of the device meet the design input requirements,the total dose irradiation resistance index reaches 100krad(Si),the single event locking threshold is greater than 75 Me V·cm~2/mg,and the single event transient threshold is greater than 75 Me V·cm~2/mg.It lays a foundation for the subsequent application of the device in the actual space environment.The research results obtained in this dissertation have been installed and verified on the model products to meet the actual engineering application requirements. |
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