关键词: 超再生接收机, 频率选择性, 晶体振荡器, 紧凑接收机, 无线传感网 

Abstract:  To overcome the poor frequency accuracy and selectivity of the conventional superregenerative receiver (SＲＲ)，a SＲＲ based on crystal has been proposed for low-data rate and low distance wireless sensor network (WSN)． This SＲＲ adopts a crystal oscillator (XO) as a superregenerative oscillator (SＲO) instead of the conventional LC or ＲC oscillator． With the help of the ultra-high quality factor of the crystal this SＲＲ has achieved the same accuracy and stability of working frequency as a crystal，and is immune to variations of process，voltage and temperature． A prototype chip， implemented in 0. 18-μm CMOS technology，utilizes a bi-direction driver to overcome the challenges of slow start-up and fully quenching，makes a reference XO work in a super-pre-generative manner，and then achieves sensitivity of －78dBm (1kb/s data rate)． The measured data show 50 times improvement on the frequency selectivity，and 7 ×10 －6 frequency error from the target frequency，which matches the reference-class accuracy． This receiver supplies a very compact solution with only a crystal being needed outside except several decoupling capacitors，which is suitable for WSN applications，e. g． wireless capsule endoscopy． 

Key words: superregenerative receivers, frequency selectivity, crystal oscillators, compact receivers, wireless sensor networks