# US 11,309,860 B1 · Single ladder duplexer with impedance gradient > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,860 B1 - Document ID: US11309860B1 - Status: Granted - Kind: B1 - Application number: 17/067,017 - Filed: 2020-10-09 - Published: 2022-04-14 - Granted: 2022-04-19 - Earliest claimed: 2020-10-09 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Oliver Georg Dorn; Joonhoi Hur; Rastislav Vazny - Web page: https://patentgrep.com/patent/US11309860B1 ## CPC - H03H 7/38: Impedance-matching networks - H03F 1/565: {using inductive elements} - H03F 3/189: High-frequency amplifiers, e.g. radio frequency amplifiers - H03F 3/24: of transmitter output stages - H03F 3/245: {with semiconductor devices only} - H03H 7/463: {Duplexers} - H04B 1/44: Transmit/receive switching - H03F 2200/171: A filter circuit coupled to the output of an amplifier - H03F 2200/294: the amplifier being a low noise amplifier [LNA] - H03F 2200/451: the amplifier being a radio frequency amplifier - H03H 7/09: Filters comprising mutual inductance - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H03F: AMPLIFIERS - H04B: TRANSMISSION ## Abstract Embodiments presented herein relate to isolating a receiver circuit of an electronic device from a transmission signal and from a noise signal at a frequency range of a received signal. To do so, an isolation circuit is disposed between the receiver circuit and a transmission circuit. The isolation circuit may include multiple variable impedance devices and one or more antennas. The impedances of the variable impedance devices and the one or more antennas may be balanced such that the receiver circuit is effectively removed from the transceiver circuitry and isolated from the transmission signal. The impedance of the variable impedance devices and the one or more antennas may also be configured to isolate the receiver circuit from a noise signal generated at the transmission circuit having a frequency in the range of the receive signal. ## Claims ### Claim 1 An electronic device comprising: a transmit circuit configured to generate a transmission signal; a receive circuit configured to receive a receive signal; and an isolation circuit including: one or more antennas having a first impedance, the one or more antennas communicatively coupled to the transmit circuit via a transmit path, and the one or more antennas communicatively coupled to the receive circuit via a receive path; a first variable impedance device disposed in the transmit path and having a first variable impedance; a second variable impedance device disposed between the transmit circuit and the receive circuit and having a second variable impedance; and a third variable impedance device coupled between the receive circuit and the second variable impedance device and having a third variable impedance, wherein the first variable impedance device, the second variable impedance device, and the third variable impedance device are configured to isolate the receive circuit from the transmission signal and from a noise signal generated by the transmit circuit having a frequency of the receive signal when a ratio of the first variable impedance to the first impedance is equal to a ratio of the second variable impedance to the third variable impedance. ### Claim 2 (depends on 1) The electronic device of claim 1, wherein the isolation circuit is configured to isolate the receive circuit from the transmission signal by balancing the first impedance, the first variable impedance, the second variable impedance, and the third variable impedance, thereby causing zero voltage across the receive circuit. ### Claim 3 (depends on 1) The electronic device of claim 1, wherein the first variable impedance varies from a second impedance during transmit operations to a third impedance higher than the second impedance during receive operations, the second variable impedance varies from a fourth impedance during the receive operations to a fifth impedance less than the fourth impedance during the transmit operations, and the third variable impedance varies from a sixth impedance during the transmit operations to a seventh impedance lower than the sixth impedance during the receive operations. ### Claim 4 (depends on 3) The electronic device of claim 3, wherein a ratio of the fifth impedance to the seventh impedance is equal to a ratio of the third impedance to the first impedance during the receive operations and a ratio of the fourth impedance to the sixth impedance is equal to a ratio of the second impedance to the first impedance during the transmit operations. ### Claim 5 (depends on 1) The electronic device of claim 1, comprising a balun disposed between and coupling the receive circuit and the isolation circuit. ### Claim 6 (depends on 1) The electronic device of claim 1, wherein each of the first variable impedance device, the second variable impedance device, and the third variable impedance device comprises an impedance gradient or an impedance tuner. ### Claim 7 (depends on 1) The electronic device of claim 1, wherein the first variable impedance and the second variable impedance device each comprises a parallel arrangement of a plurality of inductors coupled in series with a plurality of capacitors. ### Claim 8 (depends on 1) The electronic device of claim 1, wherein the third variable impedance device comprises a resistor coupled in parallel with a parallel arrangement of a plurality of inductors coupled in series with a plurality of capacitors. ### Claim 9 (depends on 1) The electronic device of claim 1, wherein the first variable impedance device, the second variable impedance device, and the third variable impedance device are configured to direct the noise signal from the transmit circuit to the second variable impedance device and the third variable impedance device. ### Claim 10 An electronic device comprising: one or more antennas having a first impedance; transmitter circuitry configured to transmit a transmission signal via the one or more antennas; receiver circuitry configured to receive a receive signal via the one or more antennas; a first variable impedance device having a first variable impedance; a second variable impedance device having a second variable impedance, the transmitter circuitry, the first variable impedance device, and the second variable impedance device communicatively coupled together via a first node; a third variable impedance device having a third variable impedance, the first variable impedance device, the receiver circuitry, and the third variable impedance device communicatively coupled together via a second node, and the second variable impedance device, the receiver circuitry, and the one or more antennas coupled together via a third node. ### Claim 11 (depends on 10) The electronic device of claim 10, wherein the first impedance, the first variable impedance, the second variable impedance, and the third variable impedance are configured to isolate the receiver circuitry when a ratio of the first variable impedance to the third variable impedance is equal to a ratio of the second variable impedance to the first impedance. ### Claim 12 (depends on 10) The electronic device of claim 10, wherein the first variable impedance, the second variable impedance, and the third variable impedance are frequency dependent. ### Claim 13 (depends on 10) The electronic device of claim 10, wherein the first variable impedance is greater than the second variable impedance at a first frequency, the first variable impedance device is less than the third variable impedance at the first frequency, the first variable impedance is less than the second variable impedance at a second frequency, and the first variable impedance is greater than impedance of the third variable impedance device at the second frequency. ### Claim 14 (depends on 10) The electronic device of claim 10, wherein the third variable impedance is less than each of the first variable impedance, the second variable impedance, and the first impedance at a frequency of the receive signal. ### Claim 15 (depends on 14) The electronic device of claim 14, wherein the receiver circuitry is configured to be isolated from the transmission signal when a ratio of the first variable impedance to the third variable impedance is substantially equivalent to a ratio of the second variable impedance to the first impedance. ### Claim 16 (depends on 10) The electronic device of claim 10, wherein the first variable impedance varies from a second impedance during transmit operations to a third impedance higher than the second impedance during receive operations, the second variable impedance varies from a fourth impedance during the receive operations to a fifth impedance less than the fourth impedance during the transmit operations, and the third variable impedance varies from a sixth impedance during the transmit operations to a seventh impedance lower than the sixth impedance during the receive operations. ### Claim 17 (depends on 16) The electronic device of claim 16, wherein a ratio of the seventh impedance to the fifth impedance is equal to a ratio of the third impedance to the first impedance during the receive operations and a ratio of the sixth impedance to the fifth impedance is equal to a ratio of the second impedance to the first impedance during the transmit operations. ### Claim 18 An electronic device, comprising: a transmitter configured to transmit a transmission signal; a receiver configured to receive a receive signal; and an isolation circuit configured to isolate the receiver from the transmission signal and a noise signal generated by the transmitter, the noise signal having a frequency of the receive signal, the isolation circuit comprising a plurality of variable impedance devices configured to direct the transmission signal and the noise signal away from the receiver when the plurality of variable impedance devices are in a balanced state. ### Claim 19 (depends on 18) The electronic device of claim 18, wherein the plurality of variable impedance devices includes a first variable impedance device communicatively coupled to the antenna and the transmitter and having a first variable impedance, a second variable impedance device communicatively coupled to the receiver and having a second variable impedance, and a third variable impedance device communicatively coupled to the transmitter and the receiver and having a third variable impedance. ### Claim 20 (depends on 19) The electronic device of claim 19, comprising an antenna having a first impedance, wherein the plurality of variable impedance devices are in the balanced state when a ratio of the first variable impedance to the first impedance is equal to a ratio of the third variable impedance to the second variable impedance.