Analysis and Prejudgment of Entire-Link Rejection Ratio of a Spaceborne Microwave Receiver Against Switched Mode Power Supply Harmonics

With the wide application of high-sensitivity broadband microwave receivers, the requirement of power-supply modulation ratio in receivers is greatly increased. Especially, the switched mode power-supply harmonics of the secondary converted power-supply in the satellite will inevitably produce spurious emissions in the receiver band. Therefore, it is necessary to analyze and prejudge the spurious response rejection ratio of the entire link from power-supply when designing a spaceborne high-sensitivity broadband receiver. The systematic theoretical formula of the spurious rejection ratio of each link is obtained by researching the influence of circuit design parameters, including the ratio of modules' area to spacing, transistor bias voltage, frequency multiplying times, and sensitivity of the voltage-controlled oscillator. Taking a spaceborne Ka-band broadband receiver as an example, and the actual receiver is manufactured and measured for verification. By reducing the circuit area to 35 cm 2 , separating the module spacing to 0.1 mm, selecting a transistor gate bias voltage of −0.25 V, increasing the oscillator frequency to 3.25 GHz, and reducing the oscillator's voltage control sensitivity to 58 MHz/V, the optimal power supply switched spurious rejection ratio of nearly 60 dBc was ultimately achieved.