# US 10,768,213 B2 · Software-defined radiometer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,213 B2 - Document ID: US10768213B2 - Status: Granted - Kind: B2 - Application number: 15/690,852 - Filed: 2017-08-30 - Published: 2019-02-28 - Granted: 2020-09-08 - Earliest claimed: 2017-08-30 - Assignees: United States of America as represented by the Administrator of NASA - Applicants: United States of America as represented by the Administrator of NASA - Inventors: Lynn R. Miles; Damon C. Bradley; Englin Wong; Alicia T. Joseph - Web page: https://patentgrep.com/patent/US10768213B2 ## CPC - G01R 23/165: using filters - G01R 23/06: by converting frequency into an amplitude of current or voltage - G01R 23/16: Spectrum analysis; Fourier analysis - G01R 29/08: Measuring electromagnetic field characteristics - G01R 29/0878: {Sensors; antennas; probes; detectors (wave guide measuring sections G01R1/24)} - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A software-defined radiometer includes dual RF front end channels. One RF front end channel processes the horizontal polarization signals and the other RF front end channel processes the vertical polarization signals. Each RF front end channel includes a power splitter for splitting the polarization signals into a plurality of identical polarization signals, a filter bank of N-bandpass filters that have the same bandwidth but different center frequencies and a multi-input switch. The bandpass filters filter the horizontal and vertical polarization signals and provide a plurality of filtered horizontal and vertical polarization signals. A control circuit issues a control signal to the multi-input switch so as to route a desired one of the plurality of filtered horizontal and vertical polarization signals to a programmable frequency converter. The programmable frequency converter includes a programmable local oscillator that is configured to generate signals having any one of N frequencies and is used to produce intermediate frequency representations of the horizontal and vertical polarization signals. The intermediate frequency representations are converted into digital signals and processed to extract desired information and data. ## Claims ### Claim 1 A radiometer for receiving and processing RF signals of the same frequency but with different polarizations, comprising: a plurality of RF signal paths, each RF signal path configured to receive and process RF signals from an external source, each of the RF signals having a particular polarization; an input bandpass filter in each RF signal path for filtering the received RF signal having the particular polarization and outputting a filtered received RF signal, wherein the input bandpass filter has a predetermined bandwidth and center frequency; a signal splitting device in each RF signal path for splitting the filtered received RF signal into a plurality of identical RF signals; a filter bank of bandpass filters in each RF signal path 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; an electronically controlled switch in each RF signal path which includes a plurality of RF signal inputs, a RF signal output and a control signal input for receiving a control signal that determines which of the RF signal inputs is coupled to the RF signal output, each RF signal input receiving a corresponding uniquely filtered RF signal provided by the filter bank, wherein the electronically controlled switch couples one of the uniquely filtered RF signals to the RF signal output upon receiving the control signal; programmable frequency conversion circuitry for converting the uniquely filtered RF signal outputted by the electronically controlled switch in each RF signal path into intermediate frequency representations having predetermined intermediate frequencies; signal conversion circuitry for converting the intermediate frequency representations into digital signals; and a signal processor to process the digital signals to extract desired information from the digital signals. ### Claim 2 (depends on 1) The radiometer according to claim 1 further comprising an amplifier in each RF signal path for amplifying the filtered received RF signal provided by the input bandpass filter. ### Claim 3 (depends on 1) The radiometer according to claim 1 further comprising a programmable control circuit for providing control signals for input into the electronically controlled switch in each RF signal path, each control signal defining which one of the uniquely filtered RF signals is to be outputted by the electronically controlled switch. ### Claim 4 (depends on 3) The radiometer according to claim 3 wherein the programmable frequency conversion circuitry comprises: a local oscillator for generating a local oscillator RF signal having a predetermined frequency; a mixer for mixing the local oscillator RF signal with the uniquely filtered RF signal outputted from the electronically controlled switch of one RF signal path to produce signals that include an intermediate frequency representation having one polarization; and another mixer for mixing the local oscillator RF signal with the uniquely filtered RF signal outputted by the electronically controlled switch of another one of the RF signal paths to produce signals that include an intermediate frequency representation having another polarization. ### Claim 5 (depends on 4) The radiometer according to claim 4 wherein the local oscillator comprises a voltage controlled oscillator which has input for receiving a voltage signal, wherein the magnitude of the voltage signal determines the frequency of the local oscillator RF signal. ### Claim 6 (depends on 5) The radiometer according to claim 5 wherein the programmable frequency conversion circuitry further comprises a programmable hardware element that has an input for receiving a digital signal that represents a desired voltage magnitude and an output for providing a voltage signal that has the desired voltage magnitude and wherein said voltage signal outputted by the programmable hardware element is coupled to the input of the voltage controlled oscillator. ### Claim 7 (depends on 6) The radiometer according to claim 6 further comprising a computer, wherein the computer comprises said signal processor, wherein the computer is in electronic signal communication with the programmable hardware element and programmed to generate the digital signal that is inputted into the programmable hardware element. ### Claim 8 (depends on 1) The radiometer according to claim 1 further comprising: a programmable control circuit in electronic signal communication with the electronically controlled switch in each RF signal path; and a computer in electronic signal communication with the programmable control circuit, wherein the computer is programmed to issue signals to the programmable control circuit to cause the programmable control circuit to issue control signals for input into the control signal inputs of the electronically controlled switches. ### Claim 9 (depends on 4) The radiometer according to claim 4 further comprising an amplifier for amplifying the local oscillator RF signal. ### Claim 10 (depends on 4) The radiometer according to claim 4 further comprising amplifiers for amplifying the signals outputted by each of the mixers. ### Claim 11 (depends on 4) The radiometer according to claim 4 further comprising additional bandpass filters, wherein each of the additional bandpass filters the signals outputted by the mixers so that only the intermediate frequency representations having the different polarizations are passed through the additional bandpass filters. ### Claim 12 (depends on 1) The radiometer according to claim 1 further including a memory medium for storing the desired information extracted from the digital signals. ### Claim 13 (depends on 1) The radiometer according claim 1 further including a dipole antenna coupled to each of the RF signal paths. ### Claim 14 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. ### Claim 15 (depends on 14) The radiometer according to claim 14 wherein the computer is programmed to process the digital signals to extract particular information from said digital signals. ### Claim 16 (depends on 15) The radiometer according to claim 15 wherein the computer is programmed to process the digital signals with one or more signal processing algorithms. ### Claim 17 (depends on 14) The radiometer according to claim 14 further comprising a dipole antenna coupled to the input bandpass filter of each RF front end channel for receiving the horizontal polarization signals and vertical polarization signals. ### Claim 18 (depends on 14) The radiometer according to claim 14 wherein the at least one amplifier of each RF front end channel comprises a plurality of amplifiers arranged in cascade. ### Claim 19 (depends on 14) The radiometer according to claim 14 wherein one of the bandpass filters in the filter bank has a center frequency that is the same as the center frequency of the input bandpass filter. ### Claim 20 (depends on 14) The radiometer according to claim 14 wherein one of the bandpass filters in the filter bank has a center frequency that is less than the center frequency of the input bandpass filter. ### Claim 21 (depends on 14) The radiometer according to claim 14 wherein one of the bandpass filters in the filter bank has a center frequency that is greater than the center frequency of the input bandpass filter. ### Claim 22 (depends on 14) The radiometer according to claim 14 wherein the programmable frequency converter comprises a programmable local oscillator having an input for receiving the second control signal and outputting a local oscillator signal having a frequency determined by the second control signal. ### Claim 23 (depends on 22) The radiometer according to claim 22 wherein the programmable frequency converter further includes a pair of mixers, each mixer having an input for receiving the local oscillator signal and another input for receiving a filtered polarization signal outputted by an analog switch of a corresponding RF front end section, each mixer outputting a first signal having a frequency that is the sum of local oscillator signal and the frequency of the filtered polarization signal outputted by the corresponding analog switch and a second signal having an intermediate frequency that is the difference between the frequency of the local oscillator signal and the frequency of the filtered polarization signal outputted by the corresponding analog switch. ### Claim 24 (depends on 22) The radiometer according to claim 22 wherein the programmable frequency converter further includes a filter section including a pair of filters, each filter having a predetermined bandwidth and center frequency and filtering the signals outputted by a corresponding mixer, each filter passing only the signal having the intermediate frequency. ### Claim 25 (depends on 24) The radiometer according to claim 24 further including a pair of amplifiers, each amplifier being connected between one of the filters in the filter section and a corresponding mixer, the amplifier amplifying the signals outputted by the corresponding mixer. ### Claim 26 (depends on 22) The radiometer according to claim 22 wherein the programmable local oscillator comprises: a programmable voltage source having an input for receiving the second control signal and outputting a tuning voltage having a magnitude that is determined by the second control signal; and a voltage controlled oscillator having an tuning voltage input for receiving the tuning voltage and an output for providing a signal having a frequency determined by the tuning voltage. ### Claim 27 (depends on 22) The radiometer according to claim 22 wherein the programmable frequency converter further includes an amplifier to amplify the local oscillator signal. ### Claim 28 (depends on 23) The radiometer according to claim 23 wherein the programmable frequency converter further includes a power splitter for splitting the local oscillator signal into a plurality of identical local oscillator signals, wherein one of the identical local oscillator signals is inputted into one of the mixers and another one of the identical local oscillator signals is inputted into the other mixer. ### Claim 29 (depends on 14) The radiometer according to claim 14 wherein the processing element comprises an analog-to-digital signal converter for converting the signals outputted by the pair of filters of the filter section into digital signals. ### Claim 30 (depends on 14) The radiometer according to claim 14 wherein the programmable control circuit is programmed to generate duplicate selection signals for input into the processing element to enable the processing element to confirm which of the analog switches are active. ### Claim 31 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. ### Claim 32 (depends on 31) The method according to claim 31 further comprising, in each RF signal path, amplifying the filtered received RF signal. ### Claim 33 (depends on 31) The method according to claim 31 further comprising providing electrical signals that define which of the uniquely filtered RF signals of each RF signal path are to be selected. ### Claim 34 (depends on 31) The method according to claim 31 wherein the step of converting the selected uniquely filtered RF signal from each RF signal path to an intermediate frequency representation comprises: generating a local oscillator RF signal having a predetermined frequency; mixing the local oscillator RF signal with the selected uniquely filtered RF signal from one of the RF signal paths to produce signals including an intermediate frequency representation having one polarization; and mixing the local oscillator RF signal with the selected uniquely filtered RF signal from another one of the RF signal paths to produce signals including an intermediate frequency representation having another polarization. ### Claim 35 (depends on 34) The method according to claim 34 further comprising providing an electrical signal that defines the predetermined frequency of the local oscillator RF signal. ### Claim 36 (depends on 34) The method according to claim 34 further comprising amplifying the local oscillator RF signal. ### Claim 37 (depends on 34) The method according to claim 34 further comprising: amplifying the signals produced by mixing the local oscillator RF signal with the selected uniquely filtered RF signal from said one of the RF signal paths; and amplifying the signals produced by mixing the local oscillator RF signal with the selected uniquely filtered RF signal from said another one of the RF signal paths. ### Claim 38 (depends on 34) The method according to claim 34 further comprising: filtering the signals produced by mixing the local oscillator RF signal with the selected uniquely filtered RF signal from said one of the RF signal paths with a bandpass filter so as to pass only the intermediate frequency representation having said one polarization; and filtering the signals produced by mixing the local oscillator RF signal with the selected uniquely filtered RF signal from said another one of the RF signal paths with a bandpass filter so as to pass only the intermediate frequency representation having said another polarization. ### Claim 39 (depends on 34) The method according to claim 34 wherein the step of converting the intermediate frequency representations into the digital signals comprises using an analog-to-digital converter to convert the intermediate frequency representations into the digital signals. ### Claim 40 (depends on 34) The method according to claim 34 wherein the step of processing the digital signals comprises processing the digital signals with one or more digital signal processing algorithms. ### Claim 41 (depends on 31) The method according to claim 31 further comprising storing the extracted desired information in a memory medium.