Software-defined radiometer

A radiometer, comprising:

• a pair of RF front end channels for processing RF signals from an external source, each of the RF signals with different polarizations, wherein one RF front end channel processes horizontal polarization signals and the other RF front end channel processes vertical polarization signals, wherein each RF front end channel includes:
• an input bandpass filter having an input for receiving the polarization signals, an output, a bandwidth and a center frequency, the input bandpass filter outputting a filtered polarization signal,
• at least one amplifier for amplifying the filtered polarization signal to produce an amplified polarization signal,
• a power splitter for splitting the amplified polarization signal into a plurality of identical polarization signals,
• a filter bank comprising a plurality of bandpass filters, each bandpass filter of the filter bank having the same bandwidth and a different center frequency, each bandpass filter in the filter bank filtering a corresponding one of the plurality of identical polarization signals outputted by the power splitter and outputting a plurality of filtered polarization signals, and
• an analog switch having a plurality of inputs, each input of the analog switch receiving a corresponding one of the plurality of filtered polarization signals, the analog switch including an output and a selection signal input for receiving a selection signal that configures the analog switch to route a particular one of the plurality of filtered polarization signals to the output of the analog switch;
• a programmable control circuit for providing the selection signals;
• a programmable frequency converter including one or more programmable hardware elements that cooperate to convert the filtered polarization signals outputted by the analog switches of the RF front end channels to intermediate frequency representations of the filtered polarization signals outputted by the analog switches, wherein the intermediate frequency representations have predetermined frequencies;
• a computer for generating a first control signal for input into the programmable control circuit to effect generation of selection signals for input into the analog switches to enable each analog switch to output filtered polarization signals with desired center frequencies and for generating a second control signal for input into the programmable frequency converter to generate the intermediate frequency representations of the filtered polarization signals outputted by the analog switches, wherein the second control signal determines the frequencies of the intermediate frequency representations;
• and
• a processing element for converting the intermediate frequency representations into digital signals.

A method of processing RF signals from an external source, each of the RF signals of the same frequency but with different polarizations, comprising:

• providing a plurality of RF signal paths, each RF signal path configured to receive and process RF signals having a particular polarization;
• in each RF signal path, filtering the received RF signal having the particular polarization with an input bandpass filter having a predetermined bandwidth and center frequency so as to provide a filtered received RF signal;
• in each RF signal path, splitting the filtered received RF signal into a plurality of identical RF signals;
• in each RF signal path, inputting the plurality of identical RF signals into a filter bank of bandpass filters wherein each bandpass filter of the filter bank has the same bandwidth but different center frequencies and wherein each of the identical RF signals is filtered by a corresponding bandpass filter of the filter bank so as to provide a plurality of uniquely filtered RF signals having the particular polarization;
• in each RF signal path, selecting one of the plurality of uniquely filtered RF signals;
• converting the selected uniquely filtered RF signal from each RF signal path to an intermediate frequency representation having a predetermined intermediate frequency;
• converting the intermediate frequency representations into digital signals;
• and
• processing the digital signals to extract desired information from the digital signals.