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Cochlear signal analysis for broadband spectrum sensing in cognitive radio networks

The biological inner ear, or cochlea, is a sophisticated signal processing system that performs spectrum analysis over an ultra-broadband frequency range of ∼20 Hz to 20 kHz with exquisite sensitivity and high energy efficiency. Electronic cochlear models, which mimic the exponentially-tapered structure of the biological inner ear using transmission lines or filter cascades, have been shown to be fast and extremely efficient spectrum analyzers at both audio and radio frequencies. We have previously used this model to create single-chip RF spectrum analyzers, and have recently developed improved output encoding methods for such cochlea-like analyzers. A prototype analyzer has been designed in the UMC 65 nm RF-CMOS process. It includes a bidirectional cochlea model with 50 parallel exponentially-spaced output stages and analyzes the radio spectrum from 0.8–8.3 GHz. The outputs are encoded as delta-sigma (ΔΣ) modulated digital signals that are demodulated and analyzed in real-time by a digital back-end implemented on a field-programmable gate array (FPGA). The resulting system is expected to be useful as a broadband spectrum sensor in cognitive radio networks.