Bio-Inspired Hybrid Filter Bank for Software-Defined Radio Receivers

For an efficient exploitation of the RF spectrum, very sophisticated analog-to-digital front-ends for modern cognitive-/software-defined radios featuring high sampling rate and dynamic range are required to properly handle broadband frequency-sparse signals. For this purpose, a receiver solution based on a mixed-analog/digital-domain channelizer can be advantageous, with added benefits regarding system reconfigurability and parallelization of multiband signal processing. Here, a novel receiver architecture using this approach for the commented application is described, with a special focus on the IF hybrid filter bank as its core element. The analog part of the hybrid filter bank is a 50–100-MHz eight-channel analog multiplexer inspired in the human hearing system. The associated digital block can be co-synthesized as a discrete-time filter bank to invert the action of the IF analog channelizer. As a benefit, hardware imperfections inherent to the analog circuitry can be easily counteracted at the digital level. Furthermore, such a channelization enables low-cost analog-to-digital converters to be utilized for the sampling of the signal sub-bands to be later digitally processed for the overall signal reconstruction. For validation, measured and simulated results of a proof-of-concept prototype for the analog channelizer are shown. Besides, the inversion of the measured transfer functions of this multiplexing device by means of the application of the co-designed digital filter bank is demonstrated. An experiment is also carried out showing the reconstruction of a band-limited noise signal with the developed hybrid filter bank.