# US 8,543,071 B2 · Radiofrequency emission or reception chain with automatic impedance adaptation, and corresponding method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,543,071 B2 - Document ID: US8543071B2 - Status: Granted - Kind: B2 - Application number: 13/440,758 - Filed: 2012-04-05 - Published: 2012-10-11 - Granted: 2013-09-24 - Earliest claimed: 2011-04-07 - Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Applicants: Majid El Kaamouchi; Jean-Baptiste David; Emeric De Foucauld - Inventors: Majid El Kaamouchi; Jean-Baptiste David; Emeric De Foucauld - Web page: https://patentgrep.com/patent/US8543071B2 ## CPC - H04B 1/04: Circuits - H03H 7/40: Automatic matching of load impedance to source impedance - H04B: TRANSMISSION - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract As relates to automatic matching of antenna impedance for a radiofrequency transmit or receive circuit, an impedance matching network is inserted between an amplifier and antenna. The current i and output (resp. input) voltage V of the amplifier and their phase shift are measured, the complex impedance defined by V/i is deduced; the impedance of the antenna is calculated as a function of this complex impedance and the known existing values of the adjustable impedances of the matching network. New adjustable values of impedances of the matching network to obtain a desired overall load impedance for the amplifier are calculated on the basis of the calculated antenna impedance value, and the matching network is controlled to adjust the adjustable impedances to these new values. The measurement is made at a measurement frequency different from the working frequency to allow automatic matching without interrupting normal operation of the chain. ## Claims ### Claim 1 A radiofrequency transmit or receive chain working at a nominal frequency F0, comprising: at least one amplifier, an antenna, an impedance matching network disposed between the amplifier and the antenna and comprising adjustable impedances, a measurement impedance of known complex value inserted in series between the amplifier and the matching network, means of measurement of the potentials present at the terminals of the measurement impedance for determining at one and the same time the current in the measurement impedance and a voltage at the output of the amplifier for a transmit chain or a voltage at the input of the amplifier for a receive chain, means of calculation of the complex impedance defined by the ratio of the voltage and the current, this complex impedance representing an existing load impedance or input impedance of the amplifier, of an impedance of the antenna, and of new values of the adjustable impedances of the matching network which make it possible to obtain a desired load impedance or input impedance for the amplifier, and means of electrical control of the matching network for adjusting the adjustable impedances to these new values, wherein the chain comprises a measurement frequency generator linked to the output of the transmit amplifier or to the input of the transmit amplifier, so as to inject thereinto a measurement frequency Fm different from the working frequency F0, the calculation means being designed to make impedance calculations on the basis of voltages and currents measured at the frequency Fm, and thereafter applying a correction so as to bring the calculated impedances to the values that they would have for the frequency F0. ### Claim 2 (depends on 1) The transmit or receive chain as claimed in claim 1, further comprising a bandpass filter incorporated into the frequency generator or placed immediately downstream of the latter so as to allow only the measurement frequency Fm to pass through to the remainder of the chain and to prevent the passage of signals at the frequency F0 to the generator. ### Claim 3 (depends on 2) The transmit or receive chain as claimed in claim 2, further comprising a bandstop filter of known impedance characteristics inserted between the amplifier and the measurement impedance so as to avoid the passage to the amplifier of signals at the frequency Fm. ### Claim 4 (depends on 2) The transmit or receive chain as claimed in claim 2, wherein the means for measuring potentials comprise a frequency transposition circuit with a local oscillator with frequency FOL so as to transpose the measurement frequency Fm to an intermediate frequency FIF=Fm−FOL and a low-pass filter allowing the frequency FIF to pass, but not frequency F0−FOL. ### Claim 5 (depends on 1) The transmit or receive chain as claimed in claim 1, further comprising a bandstop filter of known impedance characteristics inserted between the amplifier and the measurement impedance so as to avoid the passage to the amplifier of signals at the frequency Fm. ### Claim 6 (depends on 5) The transmit or receive chain as claimed in claim 5, wherein the means for measuring potentials comprise a frequency transposition circuit with a local oscillator with frequency FOL so as to transpose the measurement frequency Fm to an intermediate frequency FIF=Fm−FOL and a low-pass filter allowing the frequency FIF to pass, but not frequency F0−FOL. ### Claim 7 (depends on 1) The transmit or receive chain as claimed in claim 1, wherein the means for measuring potentials comprise a frequency transposition circuit with a local oscillator with frequency FOL so as to transpose the measurement frequency Fm to an intermediate frequency FIF=Fm−FOL and a low-pass filter allowing the frequency FIF to pass, but not frequency F0−FOL. ### Claim 8 (depends on 1) The transmit or receive chain as claimed in claim 1, wherein the means for measuring potentials comprise a frequency transposition circuit with a local oscillator with frequency FOL so as to transpose the measurement frequency Fm to an intermediate frequency FIF=Fm−FOL and a low-pass filter allowing the frequency FIF to pass, but not frequency F0−FOL. ### Claim 9 A method of automatic impedance matching of a radiofrequency transmit or receive chain working at a nominal frequency F0 and comprising at least one amplifier, an antenna, an impedance matching network disposed between the amplifier and the antenna and comprising adjustable impedances, a measurement impedance of known complex value inserted in series between the amplifier and the matching network, means of measurement of the potentials present at the terminals of the measurement impedance for determining at one and the same time the current in the measurement impedance and a voltage at the output of the amplifier for a transmit chain or a voltage at the input of the amplifier for a receive chain, means of calculation of the complex impedance defined by the ratio of the voltage and the current, this complex impedance representing an existing load impedance or input impedance of the amplifier, of an impedance of the antenna and of new values of the adjustable impedances of the matching network which make it possible to obtain a desired load impedance or input impedance for the amplifier, and means of electrical control of the matching network for adjusting the adjustable impedances to these new values, wherein a measurement frequency Fm differing from the working frequency is injected into the chain, the measurements of potentials are performed at this frequency, and the impedance calculations are made on the basis of these measurements by applying a correction so as to bring the calculated impedances to the values that they would have for the frequency F0.