A novel M-FSK modem architecture based on perfect reconstruction NMDFBs

Standard M-FSK demodulators are implemented with a series of digital parallel matched filters followed by envelope detectors and a decision stage. The number of required matched filter and envelope detectors is the same as the number of complex (In-phase/Quadrature) sub-carriers. The performance, in terms of bit error rate, of the M-FSK transmission improve as the number of frequencies employed increases. This improvement is obtained at the expense of increased size, weight and power consumption (SWaP) in the transceiver. In standard M-FSK demodulators, transmission performance and receiver complexity are inversely proportional. In this paper we propose a new fully-digital M-FSK demodulator that inverts this rule. The proposed architecture is based on perfect reconstruction (PR) non-maximally decimated filter banks (NMDFBs) also referred to as polyphase channelizers. And, compared to standard FSK receivers, the efficacy of the proposed architecture increases as the number of frequencies employed, M, increases. The architecture we propose has a very compact design and, for M larger than 16, it is more efficient than standard M-FSK receivers.