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An AM superheterodyne receiver for wide-input weak signals at 200 MHz–400 MHz

Superheterodyne receiver is a practical radio receiver with long history. It is widely used in broadcasting, radio communication, etc. However, when the incoming signal is a weak signal in a large variation range, the traditional superheterodyne receiver using discrete amplifier, non-linear mixer and envelope detector has the disadvantages of low signal-to-noise ratio(SNR), poor sensitivity, and high distortion. In this paper, we propose a novel superheterodyne receiver, consisting of two-stage integrated low noise amplifier(LNA), 7-order band-pass filter(BPF), automatic gain circuit(AGC), integrated mixer, synchronous detector and baseband amplifier. It can high-quality demodulate AM signals with the amplitude of 10uv to 1mV, message signal frequency of 300Hz–5kHz, and carrier frequency of 200MHz-400MHz. In addition, this receiver also realizes the automatic tracking of carrier by adding power detection and microcontroller Unit(MCU) modules.