# US 2014/0152489 A1 · High-frequency ocean surface radar using frequency multiplexing and orthogonal waveforms > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152489 A1 - Document ID: US20140152489A1 - Status: Published application - Kind: A1 - Application number: 13/870,811 - Filed: 2013-04-25 - Published: 2014-06-05 - Earliest claimed: 2012-12-04 - Assignees: Hannam University Institute for Industry-Academia Cooperation; Electronics and Telecommunications Research Institute - Inventors: Joo Hwan LEE; Dong-Uk SIM; Young Jun CHONG; Jong Ho KIM; YOUNG KEUN YOON; Myoung-Won JUNG; In-Sik CHOI - Web page: https://patentgrep.com/patent/US20140152489A1 ## CPC - G01S 7/023: {Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques (auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36)} - G01S 13/282: {using a frequency modulated carrier wave (G01S13/286 takes precedence)} - G01S 13/87: Combinations of radar systems, e.g. primary radar and secondary radar - 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 method of reusing a frequency by allocating two orthogonal signal waveforms to the same frequency band is as follows. Two high-frequency ocean surface radars can be operated in the same frequency band without mutual interference by allocating a signal having an up-chirped LFM waveform and a signal having a down-chirped LFM waveform, having the same frequency band, to the two radars by employing an orthogonal characteristic between the two signals. Furthermore, a plurality of radars located within a distance within which interference is possible can be operated without mutual interference by combining and allocating two orthogonal signals and a plurality of frequency bands. ## Claims ### Claim 1 A frequency reuse apparatus, comprising: a reset unit for resetting a number of repetitions for a frequency reuse method for two or more radars; a parameter input unit for receiving parameters for the two or more radars; a minimum separation distance determination unit for determining a minimum separation distance between the two or more radars from a maximum detection distance between the two or more radars; an interference distance condition determination unit for determining whether interference is present between the two or more radars; and a frequency and waveform determination unit for determining a frequency and a waveform to be used by each of the two or more radars without interference. ### Claim 2 (depends on 1) The frequency reuse apparatus of claim 1, wherein the frequency and waveform determination unit allocates a signal having an up-chirped Linear Frequency Modulation (LFM) waveform and a signal having a down-chirped LFM waveform to the respective two or more radars, the signal having the up-chirped LFM waveform and the signal having a down-chirped LFM waveform having an identical frequency band. ### Claim 3 (depends on 2) The frequency reuse apparatus of claim 2, wherein a distance between the two or more radars exceeds twice the minimum separation distance. ### Claim 4 (depends on 1) The frequency reuse apparatus of claim 1, wherein the frequency and waveform determination unit combines a plurality of frequency bands with the signal having the up-chirped LFM waveform and the signal having the down-chirped LFM waveform and simultaneously allocates the combined frequencies and signal waveforms to the two or more radars. ### Claim 5 (depends on 4) The frequency reuse apparatus of claim 4, wherein a distance between the two or more radars is less than twice the minimum separation distance. ### Claim 6 (depends on 1) The frequency reuse apparatus of claim 1, further comprising an end determination unit for determining whether the frequency reuse method has ended or not. ### Claim 7 A frequency reuse method of a frequency reuse apparatus, comprising: resetting a number of repetitions for a frequency reuse method for two or more radars; receiving parameters for the two or more radars; determining a minimum separation distance between the two or more radars from a maximum detection distance between the two or more radars; determining whether interference is present between the two or more radars; and determining a frequency and a waveform to be used by each of the two or more radars without interference. ### Claim 8 (depends on 7) The frequency reuse method of claim 7, wherein the determining a frequency and a waveform to be used by each of the two or more radars without interference comprises allocating a signal having an up-chirped Linear Frequency Modulation (LFM) waveform and a signal having a down-chirped LFM waveform to the respective two or more radars, the signal having the up-chirped LFM waveform and the signal having the down-chirped LFM waveform having an identical frequency band. ### Claim 9 (depends on 8) The frequency reuse method of claim 8, wherein a distance between the two or more radars exceeds twice the minimum separation distance. ### Claim 10 (depends on 8) The frequency reuse method of claim 8, further comprising: transmitting the signal having the up-chirped LFM waveform and the signal having the down-chirped LFM waveform, having the same frequency band, from the two or more radars to an ocean surface; and performing matched filtering between signal waveforms reflected by and received from the ocean surface. ### Claim 11 (depends on 7) The frequency reuse method of claim 7, wherein the determining a frequency and a waveform to be used by each of the two or more radars without interference comprises combining a plurality of frequency bands with the signal having the up-chirped LFM waveform and the signal having the down-chirped LFM waveform and simultaneously allocating the combined frequencies and signal waveforms to the two or more radars. ### Claim 12 (depends on 11) The frequency reuse method of claim 11, wherein a distance between the two or more radars is less than twice the minimum separation distance. ### Claim 13 (depends on 7) The frequency reuse method of claim 7, further comprising determining whether the frequency reuse method has ended or not.