# US 7,609,206 B1 · Enabling digital beamforming techniques for RF systems having short repetitive synchronization sequences > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,206 B1 - Document ID: US7609206B1 - Status: Granted - Kind: B1 - Application number: 12/012,433 - Filed: 2008-02-01 - Granted: 2009-10-27 - Earliest claimed: 2008-02-01 - Assignees: Rockwell Collins, Inc. - Inventors: Dana J. Jensen; Scott J. Zogg - Web page: https://patentgrep.com/patent/US7609206B1 ## CPC - H01Q 3/26: varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture ({H01Q3/12,} H01Q3/22, H01Q3/24 take precedence) - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract A system and method of enabling digital beamforming (DBF) for use with RF receiver systems with a multi-element array antenna having short repetitive synchronizaton sequences in a noise and/or jamming environment. The method includes the following steps: a) receiving repetitive synchronization RF signals utilizing a multi-element array antenna, each of the repetitive synchronization RF signals includes an ideal known synchronization sequence, the ideal known synchronization sequence is denoted as yd and a length of the ideal known synchronization sequence is denoted as Nd; b) calculating a sequence of magnitudes and phases for each element of the multi-element array antenna corresponding to each of the ideal known synchronization sequences in the received synchronization RF signals, the sequence of the magnitudes and the phases comprises an array of N elements and is denoted as x, wherein the phases are also referred to as absolute phases; c) calculating a relative phase for each element in the sequence of the magnitudes and the absolute phases by referencing the absolute phases of all elements in the array x of N elements to a phase of a single element in the array x of N elements; d) converting the array x of N elements with the magnitudes and the absolute phases into an array of N elements with the magnitudes and the relative phases by replacing each of the absolute phases in the array x of N elements with the calculated relative phase for each element, the array of N elements with the magnitudes and the relative phases is denoted as xr; e) calculating a relative cross correlation vector for each element of the multi-element array antenna utilizing xr and yd, the relative cross correlation vector is denoted as rxd, where rxd=E{xryd*} and * is a complex conjugate; and, f) generating a relative cross correlation vector estimate by filtering rxd, for use with DBF techniques. ## Claims ### Claim 1 A method for enabling digital beamforming (DBF) techniques within a system having a multi-element array antenna receiving RF signals in a noise environment, said RF signals having short repetitive synchronization sequences, said method of enabling DBF techniques, comprising the steps of: a) receiving repetitive synchronization RF signals utilizing a multi-element array antenna, each of said repetitive synchronization RF signals comprising an ideal known synchronization sequence, said ideal known synchronization sequence being denoted as yd and a length of said ideal known synchronization sequence being denoted as Nd; b) calculating a sequence of magnitudes and phases for each element of said multi-element array antenna corresponding to each of said ideal known synchronization sequences in said received synchronization RF signals, said sequence of said magnitudes and said phases comprising an array of N elements and being denoted as x, wherein said phases are also referred to as absolute phases; c) calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases by referencing said absolute phases of all elements in said array x of N elements to a phase of a single element in said array x of N elements; d) converting said array x of N elements with said magnitudes and said absolute phases into an array of N elements with said magnitudes and said relative phases by replacing each of said absolute phases in said array x of N elements with said calculated relative phase for each element, said array of N elements with said magnitudes and said relative phases being denoted as xr; e) calculating a relative cross correlation vector for each element of said multi-element array antenna utilizing said xr and said yd, said relative cross correlation vector being denoted as rxd, where rxd=E{xryd*} and * is a complex conjugate; and, f) generating a relative cross correlation vector estimate by filtering said rxd, for use with DBF techniques. ### Claim 2 (depends on 1) The method of claim 1, further comprising the step of utilizing said relative cross correlation vector estimate for maximal ratio combining. ### Claim 3 (depends on 1) The method of claim 1, further comprising the step of utilizing said xr to calculate a covariance matrix containing results of signals arriving on any element of said multi-element array antenna with signals arriving on all other elements of said multi-element array antenna, said covariance matrix being denoted as Rx, where Rx=E{xrxrH} and H is Hermitian transpose. ### Claim 4 (depends on 1) The method of claim 1, further comprising the step of utilizing said relative cross correlation vector estimate in a weight vector algorithm, said weight vector algorithm combining said magnitude and said phase for each element with certain weight to form a combined single signal such that said combined signal being less noise and interference. ### Claim 5 (depends on 1) The method of claim 1, wherein said step of calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases, comprises the step of subtracting a phase of a single element in said array x of N elements from said absolute phases of all elements in said array x of N elements. ### Claim 6 A method for enabling digital beamforming (DBF) techniques within a system having a multi-element array antenna receiving RF signals from a plurality of sources transmitting on the same frequency at the same time in a noise environment, said RF signals having short repetitive synchronization sequences, said method of enabling DBF techniques, comprising the steps of: a) receiving repetitive synchronization RF signals from said plurality of sources utilizing a multi-element array antenna, each of said repetitive synchronization RF signals comprising an ideal known synchronization sequence, said ideal known synchronization sequence being denoted as ydi and a length of said ideal known synchronization sequence being denoted as Ndi, where i=0, 1, . . . m−1, and m is the total number of said plurality of sources; b) calculating a sequence of magnitudes and phases for each element of said multi-element array antenna corresponding to each of said ideal known synchronization sequences in said received synchronization RF signals, said sequence of said magnitudes and said phases comprising an array of N elements and being denoted as xi, wherein said phases are also referred to as absolute phases; c) calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases by referencing said absolute phases of all elements in said array xi of N elements to a phase of a single element in said array xi of N elements; d) converting said array xi of N elements with said magnitudes and said absolute phases into an array of N elements with said magnitudes and said relative phases by replacing each of said absolute phases in said array xi of N elements with said calculated relative phase for each element, said array of N elements with said magnitudes and said relative phases being denoted as xri; e) calculating a relative cross correlation vector for each element of said multi-element array antenna utilizing said xri and said ydi, said relative cross correlation vector being denoted as rxdi, where rxdi=E{xriydi*} and * is a complex conjugate; and, f) generating a relative cross correlation vector estimate by filtering said rxdi, for use with DBF techniques. ### Claim 7 (depends on 6) The method of claim 6, further comprising the step of utilizing said relative cross correlation vector estimate for maximal ratio combining. ### Claim 8 (depends on 6) The method of claim 6, further comprising the step of utilizing said xri to calculate a covariance matrix corresponding to each of said sources containing results of signals arriving on any element of said multi-element array antenna with signals arriving on all other elements of said multi-element array antenna, said covariance matrix being denoted as Rxi, where Rxi=E{xrixriH} and H is Hermitian transpose. ### Claim 9 (depends on 6) The method of claim 6, further comprising the step of utilizing said relative cross correlation vector estimate in a weight vector algorithm, said weight vector algorithm combining said magnitude and said phase for each element with certain weight to form a combined single signal such that said combined signal minimizes noise and interference. ### Claim 10 (depends on 6) The method of claim 6, wherein said step of calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases, comprises the step of subtracting a phase of a single element in said array xi of N elements from said absolute phases of all elements in said array xi of N elements. ### Claim 11 A method for enabling digital beamforming (DBF) techniques within a system having a multi-element array antenna receiving RF signals in a noise environment, said system being a frequency hopped system with a relatively large hop range compared to a carrier frequency, said RF signals having short repetitive synchronization sequences, said method of enabling DBF techniques, comprising the steps of: a) receiving repetitive synchronization RF signals utilizing a multi-element array antenna, each of said repetitive synchronization RF signals comprising an ideal known synchronization sequence for each hopped frequency, said ideal known synchronization sequence for each of said hopped frequencies being denoted as ydj and a length of said ideal known synchronization sequence being denoted as Ndj, said hopped frequency being denoted as fj, where j=0, 1, . . . k−1 and k is the total number of hopped frequencies; b) calculating a sequence of magnitudes and phases for each element of said multi-element array antenna corresponding to each of said ideal known synchronization sequences for each of said hopped frequencies in said received synchronization RF signals, said sequence of said magnitudes and said phases comprising an array of N elements and being denoted as xj, wherein said phases are also referred to as absolute phases; c) compensating said phase of said array xj utilizing information regarding multi-element array geometry for each of said hopped frequencies; d) calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases by referencing said absolute phases of all elements in said array xj of N elements to a phase of a single element in said array xj of N elements; e) converting said array xj of N elements with said magnitudes and said absolute phases into an array of N elements with said magnitudes and said relative phases by replacing each of said absolute phases in said array xj of N elements with said calculated relative phase for each element, said array of N elements with said magnitudes and said relative phases being denoted as xrj; f) calculating a relative cross correlation vector for each element of said multi-element array antenna utilizing said xrj and said ydj, said relative cross correlation vector being denoted as rxdj, where rxdj=E{xrjydj*} and * is a complex conjugate; g) translating said rxdj to a relative cross correlation vector corresponding to other hopped frequencies fi with said information regarding said multi-element array geometry, where i=0, 1, . . . k−1 and i≠j; and, h) generating a relative cross correlation vector estimate by filtering said rxdj, for use with DBF techniques. ### Claim 12 (depends on 11) The method of claim 11, further comprising the step of utilizing said relative cross correlation vector estimate for maximal ratio combining. ### Claim 13 (depends on 11) The method of claim 11, further comprising the step of utilizing said relative cross correlation vector estimate in a weight vector algorithm, said weight vector algorithm combining said magnitude and said phase for each element with certain weight to form a combined single signal such that said combined signal minimizes noise and interference. ### Claim 14 (depends on 11) The method of claim 11 further comprising the step of utilizing said xrj to calculate a covariance matrix corresponding to each of said hopped frequencies containing results of signals arriving on any element of said multi-element array antenna with signals arriving on all other elements of said multi-element array antenna, said covariance matrix being denoted as Rxj, where Rxj=E{xrjxrjH} and H is Hermitian transpose. ### Claim 15 (depends on 11) The method of claim 11, wherein said step of compensating said phase of said array xj utilizing said information regarding said multi-element array geometry for each of said hopped frequencies is omitted, under a circumstance of a wavelength of the lowest and highest hopped frequency changing by a relatively small amount, the element separation of said multi-element array, being expressed in wavelengths of said hopped frequency, being deemed static. ### Claim 16 (depends on 11) The method of claim 11, wherein said step of calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases, comprises the step of subtracting a phase of a single element in said array xj of N elements from said absolute phases of all elements in said array xj of N elements. ### Claim 17 An RF receiver for enabling digital beam forming (DBF) techniques receiving RF signals in a noise environment, said RF signals having short repetitive synchronization sequences, said RF receiver, comprising: at least one digital signal processor (DSP) for performing the following: a) calculating a sequence of magnitudes and phases for each element of said multi-element array antenna corresponding to each of said ideal known synchronization sequences in said received synchronization RF signals, said sequence of said magnitudes and said phases comprising an array of N elements and being denoted as x, wherein said phases are also referred to as absolute phases; b) calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases by referencing said absolute phases of all elements in said array x of N elements to a phase of a single element in said array x of N elements; c) converting said array x of N elements with said magnitudes and said absolute phases into an array of N elements with said magnitudes and said relative phases by replacing each of said absolute phases in said array x of N elements with said calculated relative phase for each element, said array of N elements with said magnitudes and said relative phases being denoted as xr; d) calculating a relative cross correlation vector for each element of said multi-element array antenna utilizing said xr and said yd, said cross correlation vector being denoted as rxd, where rxd=E{xryd*} and * is a complex conjugate; and, e) generating a relative cross correlation vector estimate by filtering said rxd, for use with DBF techniques. ### Claim 18 An RF system for receiving RF signals in a noise environment, said RF signals having short repetitive synchronization sequences, said RF system, comprising: a) a multi-element array antenna for receiving repetitive synchronization RF signals, each of said repetitive synchronization RF signals comprising an ideal known synchronization sequence, said ideal known synchronization sequence being denoted as yd and a length of said ideal known synchronization sequence being denoted as Nd; and, b) an RF receiver, comprising at least one DSP for performing the following: i. calculating a sequence of magnitudes and phases for each element of said multi-element array antenna corresponding to each of said ideal known synchronization sequences in said received synchronization RF signals, said sequence of said magnitudes and said phases comprising an array of N elements and being denoted as x, wherein said phases are also referred to as absolute phases; ii. calculating a relative phase for each element in said sequence of said magnitudes and said absolute phases by referencing said absolute phases of all elements in said array x of N elements to a phase of a single element in said array x of N elements; iii. converting said array x of N elements with said magnitudes and said absolute phases into an array of N elements with said magnitudes and said relative phases by replacing each of said absolute phases in said array x of N elements with said calculated relative phase for each element, said array of N elements with said magnitudes and said relative phases being denoted as xr; iv. calculating a relative cross correlation vector for each element of said multi-element array antenna utilizing said xr and said yd, said cross correlation vector being denoted as rxd, where rxd=E{xryd*} and * is a complex conjugate; and, v. generating a relative cross correlation vector estimate by filtering said rxd, for use with DBF techniques.