High-Frequency Stable Wireless Amplitude Modulation System Based on a Pierce Circuit

This paper designs a high-frequency stable wireless amplitude modulation (AM) system based on a Pierce circuit. The system utilizes an oscillator and comparator to generate a 20 kHz square wave with an adjustable duty cycle, combined with a 41 MHz carrier wave produced by a passive crystal oscillator Pierce circuit. A 100% modulation index amplitude modulation is achieved through the AD835 multiplier. The modulated signal is amplified by a power amplifier circuit and transmitted wirelessly via the transmitter antenna. Upon reception, the signal undergoes two-stage high-frequency amplification before passing through a Schottky diode envelope detector. The NE5532 shaping circuit then restores the square wave. Experimental results demonstrate reliable 11-meter transmission with carrier frequency deviation < 0.75% and demodulation error < 1%.