Narrowband communication with free-running 2.4GHz ring oscillators

Ring oscillators have area and power advantages over LC tanks, but conventional wisdom is that rings must be locked to a high-Q external reference to be useful in RF communications. In this paper we explore performance of a 2.4GHz receiver incorporating only a free-running ring as a local oscillator. Using a simple technique to compensate for frequency error, we find that a minimum-size ring fabricated in 65nm CMOS and consuming only 105μW is able to demodulate 75% of received 802.15.4 packets and, if the FSK tone deviation is doubled from 802.15.4 spec, packet receive rate exceeds 99.8%.