Bandpass sampling architecture for wide-frequency band signal analysis

摘要

A bandpass sampling system (10) of this invention employs a conventional mixer (14) driven by a frequency-tunable LO (16) to upconvert a signal frequency band to an IF frequency band that is above the signal frequency band. The IF frequency band is passed through an IF bandpass filter (18) to provide to subsequent digitization stages (20, 24) an IF bandpass range of signal frequency components. In this architecture, the IF bandpass filter acts as an anti-alias filter for the digitization stages. The LO frequency is selected to place the upconverted signal frequency band within the pass band of the IF bandpass filter. The resultant IF bandpass signal is sampled and digitized at a rate that is commensurate with the IF bandwidth, but typically much lower than the IF bandpass center frequency. Signal sampling is carried out by a sample-and-hold or a track-and-hold circuit (20), the output of which is applied to an ADC (24) that is clocked (22) at the same rate as the sampling circuit. <IMAGE>