# US 9,002,278 B2 · Simple automatic antenna tuning system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,002,278 B2 - Document ID: US9002278B2 - Status: Granted - Kind: B2 - Application number: 13/408,719 - Filed: 2012-02-29 - Published: 2013-08-29 - Granted: 2015-04-07 - Earliest claimed: 2012-02-29 - Assignees: HTC Corporation - Applicants: William David Anderson - Inventors: William David Anderson - Web page: https://patentgrep.com/patent/US9002278B2 ## CPC - H04B 1/163: {Special arrangements for the reduction of the damping of resonant circuits of receivers (amplifiers H03F; negative impedance networks for line transmission systems H04B3/16)} - H03H 7/40: Automatic matching of load impedance to source impedance - H04B 1/0458: {Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H)} - H04B 17/12: of transmit antennas, e.g. of the amplitude or phase - H04B 17/30: of propagation channels - H04B: TRANSMISSION - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract Embodiments of a method for tuning the resonant frequency of an antenna in a wireless communication device are disclosed, along with embodiments of a wireless communication device using such a method. Embodiments sense the out-of-band impedance of the antenna, which comprises an antenna element and selectively adjustable impedance disposed between the antenna element and a ground plane of the wireless device, and adjust the selectively adjustable impedance to achieve a desired resonant frequency of the antenna. Embodiments separate an antenna signal into an in-band signal and out-of-band impedance, generate an error signal related to the out-of-band impedance, apply the error signal to a controller circuit configurable to generate an impedance error signal representing the change in antenna impedance, and apply the impedance error signal to the selectively adjustable impedance. Embodiments of a method and electronic circuit for determining the change in impedance of an antenna are also disclosed. ## Claims ### Claim 1 A method for tuning the resonant frequency of an antenna in a wireless communication device, comprising the steps of: sensing the out-of-band impedance of the antenna, the antenna comprising an antenna element and a selectively adjustable impedance disposed between the antenna element and a ground plane of the wireless device; and adjusting the selectively adjustable impedance to achieve a desired resonant frequency of the antenna, wherein the sensing step further comprises: separating an antenna signal into an in-band antenna signal and the out-of-band antenna impedance; generating an error signal related to the out-of-band impedance; and applying the error signal to a controller circuit configurable to generate an impedance error signal. ### Claim 2 (depends on 1) The method of claim 1 wherein the antenna signal comprises a signal originating from a source outside of the wireless device that is received by the antenna. ### Claim 3 (depends on 1) The method of claim 1 wherein the antenna signal comprises a portion of a signal applied to the antenna by a transmitter of the wireless device. ### Claim 4 (depends on 1) The method of claim 1 wherein: the generating step further comprises applying the out-of-band antenna impedance to an oscillator; and the error signal is a frequency error signal. ### Claim 5 (depends on 1) The method of claim 1 wherein the applying step further comprises applying the impedance error signal to the selectively adjustable impedance. ### Claim 6 (depends on 1) The method of claim 1 wherein the out-of-band impedance comprises the combination of the actual load impedance of the antenna and the selectively adjustable impedance. ### Claim 7 (depends on 1) The method of claim 1 wherein the selectively adjustable impedance is a variable reactance. ### Claim 8 (depends on 1) The method of claim 1 wherein the selectively adjustable impedance is disposed substantially away from the feed point of the antenna. ### Claim 9 (depends on 1) The method of claim 1 wherein the desired resonant frequency is a frequency on which Global Positioning System (GPS) signals are transmitted. ### Claim 10 (depends on 1) The method of claim 1 wherein the desired resonant frequency is a frequency used during two-way wireless communications. ### Claim 11 A method for determining the change in impedance of an antenna in a wireless communication device, comprising the steps of: separating an antenna signal into an in-band antenna signal and an out-of-band antenna impedance; generating an error signal related to the out-of-band antenna impedance; and applying the error signal to a controller circuit configurable to generate a signal representing the change in impedance of the antenna. ### Claim 12 (depends on 11) The method of claim 11 wherein the antenna signal comprises a signal originating from a source outside of the wireless communication device that is received by the antenna. ### Claim 13 (depends on 11) The method of claim 11 wherein the antenna signal comprises a portion of a signal applied to the antenna by a transmitter of the wireless communication device. ### Claim 14 (depends on 11) The method of claim 11 wherein: the generating step further comprises applying the out-of-band antenna impedance to an oscillator; and the error signal is a frequency error signal. ### Claim 15 An electronic circuit for determining the change in impedance of an antenna in a wireless communication device, comprising: a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance; an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance; and a controller operably connected to the oscillator, said controller configurable to generate a signal related to the change in impedance of the antenna in proportion to the frequency error signal. ### Claim 16 (depends on 15) The electronic circuit of claim 15 wherein the out-of-band antenna impedance comprises the combination of the actual antenna load impedance and a selectively adjustable impedance. ### Claim 17 (depends on 15) The electronic circuit of claim 15 wherein the oscillator comprises a radio frequency (RF) crystal oscillator. ### Claim 18 (depends on 15) The electronic circuit of claim 15 wherein the oscillator comprises a radio frequency (RF) tank oscillator. ### Claim 19 A wireless communication device comprising: an antenna; and an antenna tuning circuit, comprising: a selectively adjustable impedance disposed between an element of the antenna and a ground plane of the wireless communication device; a filter operably connected to the antenna, wherein the filter comprises a diplexer that separates an antenna signal into an in-band antenna signal and an out-of-band antenna impedance; an oscillator operably connected to the filter, said oscillator capable of generating a frequency error signal related to the out-of-band antenna impedance; and a controller operably connected to the oscillator, said controller configurable to generate an impedance error signal in proportion to the frequency error signal and to adjust the resonant frequency of the antenna to a desired resonant frequency by applying the impedance error signal to the selectively adjustable impedance. ### Claim 20 (depends on 19) The wireless communication device of claim 19 wherein the antenna signal comprises a signal originating from a source outside of the wireless device that is received by the antenna. ### Claim 21 (depends on 19) The wireless communication device of claim 19 further comprising a wireless communication transmitter, wherein the antenna signal comprises a portion of a signal applied to the antenna by the wireless communication transmitter. ### Claim 22 (depends on 19) The wireless communication device of claim 19 wherein the selectively adjustable impedance is a variable reactance. ### Claim 23 (depends on 19) The wireless communication device of claim 19 wherein the selectively adjustable impedance is disposed substantially away from the feed point of the antenna. ### Claim 24 (depends on 19) The wireless communication device of claim 19, further comprising a Global Positioning System (GPS) receiver, and wherein the desired resonant frequency is a frequency on which Global Positioning System (GPS) signals are transmitted. ### Claim 25 (depends on 19) The wireless communication device of claim 19, further comprising a wireless transceiver, and wherein the desired resonant frequency is a frequency used during two-way wireless communications. ### Claim 26 (depends on 19) The wireless communication device of claim 19, wherein the out-of-band antenna impedance comprises the combination of the actual antenna load impedance and a selectively adjustable impedance.