Double-balance passive mixer with configurable gain

The gain-configurable double-balance passive mixer disclosed by the invention is high in conversion gain and flexible in gain configuration. According to the technical scheme, a high-pass filtering circuit calls out needed frequency characteristics, prevents signals with the frequency lower than a determined frequency threshold value and allows signals with the frequency higher than the determined frequency threshold value to pass through, and a radio frequency input signal is subjected to direct current blocking and alternating current passing for high-pass filtering; a local oscillator signal from a voltage-controlled oscillator is received by N sub-mixing circuits which have the same circuit structure and are connected in parallel through a switching mixing circuit, and a radio-frequency signal is directly processed and converted into an intermediate-frequency current signal; the transimpedance amplification circuit receives input weak current and converts an intermediate-frequency current signal output by