A Broadband Spectrum Channelizer with PWM-LO Based Sub-Band Equalization

A spectrum channelizer that employs a frequency-folded analog-to-digital converter (FF-ADC) is described. The design allows for downconversion and channelization of a broadband spectrum into contiguous sub-bands, by using polyphase downconversion, baseband analog-to-digital conversion, and sub-band separation through digital-domain harmonic rejection. The sub-bands are aliased at baseband in the polyphase paths. At baseband, the sub-bands with large signal power can reduce the effective ADC dynamic range available for those with lower power levels. An approach that employs pulse-width-modulated local oscillator (PWM-LO) waveforms in the polyphase paths, for equalizing the sub-bands at baseband, prior to digitization, is proposed to address this issue. The approach makes it possible to vary the spectral response of the FF-ADC with low signal-path complexity.