Direct down-conversion of passband signals using MEMS filters and sub-sampling

The term sub-sampling implies sampling a passband system at a sampling rate of less than twice the highest frequency in the system. In this paper we address design limitations in passband subsampled radios. We develop a set of three restrictions on the sub-sampling frequency, the signal and filter bandwidth, and the desired post-sub-sampled center frequency. These restrictions will prevent intersymbol interference. Additionally, we address wideband and sampler noise replication, we show that the additional noise contribution of these sources converges under an additional restriction. We finish by showing the tradeoff between filter shape, front-end amplifier gain, and received signal to noise ratio loss. Our results are presented in the context of a micro electro-mechanical (MEMS) filtered receiver.