# US 12,009,787 B2 · Signal down-conversion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,787 B2 - Document ID: US12009787B2 - Status: Granted - Kind: B2 - Application number: 17/761,883 - Filed: 2020-09-16 - Published: 2022-10-20 - Granted: 2024-06-11 - Earliest claimed: 2019-09-20 - Assignees: Sonitor Technologies AS - Applicants: Sonitor Technologies AS - Inventors: Wilfred Edwin Booij; Elad Shabtai - Web page: https://patentgrep.com/patent/US12009787B2 ## CPC - H03D 7/165: {at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature (combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002)} - G01S 5/26: Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/28 takes precedence) - G01S 7/526: Receivers - H03M 1/0626: {by filtering} - H03M 1/124: {Sampling or signal conditioning arrangements specially adapted for A/D converters} - H03M 3/462: {Details relating to the decimation process (decimation filters in general H03H17/0416, H03H17/0621)} - H03D 2200/0062: Computation of input samples, e.g. successive samples - H04L 27/14: Demodulator circuits; Receiver circuits - H04L 27/22: Demodulator circuits; Receiver circuits - H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract An apparatus (7) for down-converting a sampled signal comprises a processing system (206) configured to apply a mixing-and-combining operation repeatedly to successive sub-sequences of N input samples, X, representative of a signal and having an initial sampling rate, M, to generate a sequence of output samples, Y, having an output rate, T, lower than the initial sampling rate M. The sub-sequences of the N input samples, X, are spaced at intervals that correspond to the output rate M. The mixing-and-combining operation generates a respective output sample Y from each sub-sequence, where Y depends on a set of products of the input samples X of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency. ## Claims ### Claim 1 A method of down-converting a sampled signal, the method comprising: receiving input samples, representative of a signal, having an initial sampling rate; and applying a mixing-and-combining operation to each of a succession of sub-sequences of the input samples to generate a sequence of output samples having an output rate lower than the initial sampling rate, wherein the sub-sequences of the input samples are spaced at intervals that correspond to the output rate, and wherein the mixing-and-combining operation generates a respective output sample from each sub-sequence wherein the output sample depends on a set of products of the input samples of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency. ### Claim 2 (depends on 1) The method of claim 1, wherein the signal comprises phase-encoded data and wherein the input samples and output samples are quadrature samples. ### Claim 3 (depends on 1) The method of claim 1, wherein the mixing frequency is not an integer multiple of the output rate, and wherein the method further comprises rotating each output sample through a constant angle relative to the immediately preceding output sample, wherein the constant angle depends on the mixing frequency and on the output rate. ### Claim 4 (depends on 1) The method of claim 1, wherein the signal is an ultrasound signal. ### Claim 5 An apparatus for down-converting a sampled signal, the apparatus comprising a processing system configured to apply a mixing-and-combining operation to each of a succession of sub-sequences of input samples, the input samples being representative of a signal and having an initial sampling rate, to generate a sequence of output samples having an output rate lower than the initial sampling rate, wherein the sub-sequences of the input samples are spaced at intervals that correspond to the output rate, and wherein the mixing-and-combining operation generates a respective output sample from each sub-sequence wherein the output sample depends on a set of products of the input samples of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the processing system is configured to rotate each output sample through a constant angle relative to the immediately preceding output sample, wherein the constant angle depends on the mixing frequency and on the output rate. ### Claim 7 (depends on 5) The apparatus of claim 5, comprising an input for receiving data representative of a target centre frequency, and wherein the processing system is configured to determine the mixing frequency from the data representative of a target centre frequency, received at the input. ### Claim 8 (depends on 5) The apparatus of claim 5, wherein applying the mixing-and-combining operation comprises performing sample-wise multiplication of the sub-sequence of input samples with the values derived from the periodic mixing signal, to generate a set of sample-wise products, and calculating an average of the set of sample-wise products. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the apparatus comprises a memory for storing the values derived from the periodic mixing signal, and wherein the processing system is configured to fetch the values derived from the periodic mixing signal from the memory and to use the same values derived from the periodic mixing signal in each mixing-and-combining operation. ### Claim 10 (depends on 5) The apparatus of claim 5, wherein applying the mixing-and-combining operation comprises calculating a discrete Fourier transform of the sub-sequence of the input samples and generating the output sample from a magnitude of a Fourier-transform frequency bin centred on the mixing frequency. ### Claim 11 (depends on 5) The apparatus of claim 5, wherein applying the mixing-and-combining operation comprises applying a Goertzel-algorithm operation, at the mixing frequency, to the sub-sequence of the input samples, and generating the output sample from output of the Goertzel-algorithm operation. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the processing system is configured to calculate a common sub-sequence length for the sub-sequences that minimises a cost function that includes a cost term that scales with distance between a target centre frequency and a closest frequency-bin index to the target centre frequency. ### Claim 13 (depends on 5) The apparatus of claim 5, wherein the processing system is configured to apply a windowing function to the input samples or to samples of the periodic mixing signal. ### Claim 14 A non-transitory computer-readable storage medium storing computer software which, when executed on one or more processors, causes the one or more processors to apply a mixing-and-combining operation to each of a succession of sub-sequences of input samples, the input samples being representative of a signal and having an initial sampling rate, to generate a sequence of output samples having an output rate lower than the initial sampling rate, wherein the sub-sequences of the input samples are spaced at intervals that correspond to the output rate, and wherein the mixing-and-combining operation generates a respective output sample from each sub-sequence wherein the output sample depends on a set of products of the input samples of the sub-sequence with respective values derived from a periodic mixing signal having a mixing frequency. ### Claim 15 (depends on 14) The non-transitory computer-readable storage medium of claim 14, wherein the computer software is a driver software and comprises an interface for receiving data representative of the output rate and of a target centre frequency from an application software.