| Active frequency selective surfaces(AFSS) is one of the important research topics in the filed of microwave engineering. And attention is mainly paid to AFSS loaded with PIN diodes. Hence,by way of different drive current(or voltage) for AFSS loaded with PIN diodes has obtained high performance microwave absorbing characteristics. Therefore,analyze and design of the digital controlled constant voltage/current power supply which can applied to the AFSS microwave reflectivity coefficient measurement were carried out from potential application point of view.At first, drive power supply for AFSS loaded PIN diodes were analyzed. The comprehensive requirements of drive power supply were paid forward on the basis of the arrangement, drive mode and special application environment of PIN diodes. Further more, after the work principle and circuits simulation of direct current linear constant voltage/current regulator and direct current switching regulator are important for the specific design of drive power supply were constructed the drive power supply for AFSS loaded with PIN diodes.Secondly,based on the practical application requirement, the drive power supply should be portable, low-power dissipation and multiple output channel.For these purpose,using 7 strings high-capacity lithium-ion batteries for system’s power supply,and using multiple daughter board connection for multiple output channel.On the basis of the basic series feedback regulator circuit, high-side current detection and high-side load high voltage output with low control voltage. Direct current linear constant voltage/current regulator have good performance in both ripple rejection and control accuracy, but its power efficiency is very low when the big difference voltage between input and output.Nevertheless, direct current switching regulator has high ripple high and power efficiency which has little effect by the load. Combines the advantages of both regulator circuit,using switching regulator as preceding regulator circuit,linear voltage/current regulator as secondary regulator circuit to design numerical control direct current constant voltage/current power supply which has good performance at ripple rejection and controlaccuracy.Finally, Cortex-M3 core STM32,16 bit DAC,24 bit ADC are used in daughter board has two direct current constant voltage/current power outputs, which with step 1 mV up to20 V output voltage, step 0.1 mA up yo 3A output current. The control board which bases on STM32 and 4-inch TFT and the bottom board which can connect most 4 daughter board are designed.After hardware debugging and voltage calibration,the drive power supply used in AFSS loaded with PIN diodes microwave reflectivity coefficient measurement and have a good performance. The results show that our system will make the needs for the smart adjustable microwave absorbing structure application. |
