# US 2014/0197984 A1 · Virtual antenna extension for sampled aperture arrays > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197984 A1 - Document ID: US20140197984A1 - Status: Published application - Kind: A1 - Application number: 13/742,220 - Filed: 2013-01-15 - Published: 2014-07-17 - Earliest claimed: 2013-01-15 - Assignees: Raytheon Canada Limited - Inventors: Jian Wang; Anthony M. Ponsford; Emily Wang; Rick McKerracher - Web page: https://patentgrep.com/patent/US20140197984A1 ## CPC - G01S 13/288: {phase modulated} - G01S 13/5246: {post processors for coherent MTI discriminators, e.g. residue cancellers, CFAR after Doppler filters} - G01S 2013/0227: {OTH, Over-The-Horizon radar} - G01S 2013/0254: {Active array antenna} - 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 ## Abstract A high frequency surface wave radar (HFSWR) system with improved performance. Two or more transmitters including separate transmitting antennas (120, 122, 410) are used to improve the performance of the HFSWR over the performance of a comparable system with a single transmitter. In one embodiment, two transmitters are used, and configured to transmit pulses alternately, with a time interval of at least a round-trip travel time corresponding to a maximum target range between any pair of transmitted pulses. A physical receiving antenna array (130) includes a plurality of receiving antenna elements (135), and is connected to receiver circuitry configured to distinguish returns corresponding to pulses emitted by the different transmitters. The returns are concatenated in the receiver circuitry to achieve improved resolution. ## Claims ### Claim 1 A high frequency surface wave radar system, comprising: a physical receiving antenna array comprising a plurality of receiving antenna elements; receiver circuitry coupled to the receiving antenna elements; a first transmitter, configured to transmit a first sequence of radar pulses separated from each other by at least a round-trip travel time corresponding to a maximum target range; and a second transmitter, configured to transmit a second sequence of radar pulses separated from each other by at least the round-trip travel time corresponding to the maximum target range; wherein the receiver circuitry is configured to: distinguish first radar returns, corresponding to radar pulses in the first sequence of radar pulses, from second radar returns, corresponding to radar pulses in the second sequence of radar pulses; and concatenate the first radar returns and the second radar returns to form a virtual receiving antenna array having a width greater than the width of the physical receiving antenna array. ### Claim 2 (depends on 1) The system of claim 1, wherein: the first transmitter is configured to generate a first sequence of radar pulses separated from each other by at least twice the round-trip travel time corresponding to the maximum target range; the second transmitter is configured to generate a second sequence of radar pulses separated from each other by at least twice the round-trip travel time corresponding to the maximum target range, each pulse in the second sequence of radar pulses being separated from each pulse in the first sequence of radar pulses by at least the round-trip travel time corresponding to the maximum target range. ### Claim 3 (depends on 2) The system of claim 2, wherein the receiver circuitry is configured to distinguish first radar returns, corresponding to radar pulses in the first sequence of radar pulses, from second radar returns, corresponding to radar pulses in the second sequence of radar pulses, by: identifying a radar return received after the transmission of a pulse in the first sequence of pulses and before the following pulse in the second sequence of pulses as a first radar return; and identifying a radar return received after the transmission of a pulse in the second sequence of pulses and before the following pulse in the first sequence of pulses as a second radar return. ### Claim 4 (depends on 1) The system of claim 1, wherein the first transmitter and the second transmitter are configured to transmit pulses simultaneously. ### Claim 5 (depends on 4) The system of claim 4, wherein: pulses in the first sequence of pulses have a first carrier frequency; pulses in the second sequence of radar pulses have a second carrier frequency; and the second carrier frequency differs from the first carrier frequency. ### Claim 6 (depends on 5) The system of claim 5, wherein the second carrier frequency differs from the first carrier frequency by more than 0.00001 percent of the first carrier frequency. ### Claim 7 (depends on 5) The system of claim 5, wherein the receiver circuitry comprises a matched filter to distinguish the first radar returns from the second radar returns. ### Claim 8 (depends on 4) The system of claim 4, wherein the first transmitter and the second transmitter are configured to transmit pulses comprising phase coding. ### Claim 9 (depends on 8) The system of claim 8, wherein the receiver circuitry is configured to distinguish first radar returns, corresponding to radar pulses in the first sequence of radar pulses, from second radar returns, corresponding to radar pulses in the second sequence of radar pulses, by their phase coding. ### Claim 10 (depends on 1) The system of claim 1, further comprising one or more additional transmitters, each of the additional transmitters configured to transmit a sequence of radar pulses separated from each other by at least the round-trip travel time corresponding to the maximum target range. ### Claim 11 (depends on 10) The system of claim 10, wherein the receiver circuitry is further configured to: distinguish the first radar returns, the second radar returns, and the radar returns corresponding to pulses transmitted by each of the additional transmitters from each other; and concatenate the first radar returns, the second radar returns and the radar returns corresponding to pulses transmitted by each of the additional transmitters, to form a virtual receiving antenna array having a width greater than the width of the physical receiving antenna array. ### Claim 12 (depends on 1) The system of claim 1, wherein the receiving antenna elements are uniformly spaced. ### Claim 13 (depends on 1) The system of claim 1, wherein the physical receiving antenna array comprises 8 receiving antenna elements. ### Claim 14 (depends on 1) The system of claim 1, wherein the first transmitter comprises a first transmitter drive circuit and a first transmitting antenna and the second transmitter comprises the first transmitter drive circuit and a second transmitting antenna. ### Claim 15 (depends on 1) The system of claim 1, comprising a first transmitter drive circuit, a first transmitting antenna, a second transmitting antenna, and a switch, wherein in a first position the switch connects the first transmitter drive circuit to the first transmitting antenna, and in a second position the switch connects the first transmitter drive circuit to the second transmitting antenna. ### Claim 16 A method for operating a high frequency surface wave radar system, comprising: transmitting, from a first transmitting location, a first sequence of first radar pulses, separated from each other by at least a round-trip travel time corresponding to a maximum target range; transmitting, from a second transmitting location, a second sequence of second radar pulses separated from each other by at least the round-trip travel time corresponding to the maximum target range; receiving, with a physical receiving antenna array comprising a plurality of receiving antenna elements, a sequence of returns comprising: first radar returns, corresponding to radar pulses in the first sequence of radar pulses, and second radar returns, corresponding to radar pulses in the second sequence of radar pulses; distinguishing the first radar returns from the second radar returns; and concatenating the first radar returns and the second radar returns. ### Claim 17 (depends on 16) The method of claim 16, wherein: the transmitting, from the first transmitting location, of the first sequence of radar pulses, comprises transmitting a sequence of first radar pulses separated from each other by at least twice the round-trip travel time corresponding to a maximum target range; and the transmitting, from the second transmitting location, of the second sequence of radar pulses, comprises transmitting a sequence of second radar pulses separated from each other by at least twice the round-trip travel time corresponding to a maximum target range, each pulse in the second sequence of radar pulses being separated from each pulse in the first sequence of radar pulses by at least the round-trip travel time corresponding to a maximum target range. ### Claim 18 (depends on 16) The method of claim 16, wherein the transmitting, from the second transmitting location, of the second sequence of second radar pulses comprises transmitting second radar pulses simultaneously with the transmitting of first radar pulses. ### Claim 19 (depends on 18) The method of claim 18, wherein the wherein the transmitting, from the second transmitting location, of the second sequence of second radar pulses comprises transmitting second radar pulses at a frequency different from a frequency of the first radar pulses.