# US 11,451,248 B2 · Front-end systems with a shared back switch > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,248 B2 - Document ID: US11451248B2 - Status: Granted - Kind: B2 - Application number: 16/947,587 - Filed: 2020-08-07 - Published: 2021-03-11 - Granted: 2022-09-20 - Earliest claimed: 2016-12-13 - Assignees: Skyworks Solutions, Inc. - Applicants: Skyworks Solutions, Inc. - Inventors: Mackenzie Brian Cook; John Jackson Nisbet - Web page: https://patentgrep.com/patent/US11451248B2 ## CPC - H04B 1/006: {using switches for selecting the desired band (H04B1/0057 takes precedence)} - H03F 3/19: with semiconductor devices only - H03F 3/245: {with semiconductor devices only} - H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal - H04B 1/0057: {using diplexing or multiplexing filters for selecting the desired band} - H04B 1/18: Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H) - H04B 1/38: Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving - H04B 1/406: {with more than one transmission mode, e.g. analog and digital modes} - H03F 2200/294: the amplifier being a low noise amplifier [LNA] - H03F 2200/451: the amplifier being a radio frequency amplifier - H03F 2203/7239: the gated amplifier being switched on or off by putting into parallel or not, by choosing between amplifiers and shunting lines by one or more switch(es) - H04B: TRANSMISSION - H03F: AMPLIFIERS ## Abstract Apparatus and methods for front-end systems with directional couplers and a shared back switch are provided. In certain configurations, a method includes transmitting a first transmit signal from a first transmit port to an antenna port, generating a first coupled signal in response to the first transmit signal using a first directional coupler, providing the first coupled signal to a receive port by way of a first loopback selection switch and a shared back switch, transmitting a second transmit signal from a second transmit port to the antenna port, generating a second coupled signal in response to the second transmit signal using a second directional coupler, and providing the second coupled signal to the receive port by way of a second loopback selection switch and the shared back switch. ## Claims ### Claim 1 A front-end system comprising: a plurality of ports including a first transmit port, a second transmit port, a receive port, and an antenna port; a plurality of radio frequency switches including a first loopback selection switch, a second loopback selection switch, and a shared back switch; and a plurality of loopback impedances including a first loopback impedance connected between the first transmit port and the receive port by way of the first loopback selection switch and the shared back switch, and a second loopback impedance connected between the second transmit port and the receive port by way of the second loopback selection switch and the shared back switch. ### Claim 2 (depends on 1) The front-end system of claim 1 further comprising a shared termination circuit connected between a first end of the shared back switch and ground, and a receive port DC blocking capacitor connected between a second end of the shared back switch and the receive port. ### Claim 3 (depends on 2) The front-end system of claim 2 wherein the shared termination circuit includes a termination resistor and a termination capacitor electrically connected in series. ### Claim 4 (depends on 2) The front-end system of claim 2 further comprising a first loopback DC blocking capacitor connected between the first end of the shared back switch and the first loopback impedance, and a second loopback DC blocking capacitor connected between the first end of the shared back switch and the second loopback impedance. ### Claim 5 (depends on 1) The front-end system of claim 1 further comprising a first transmit port DC blocking capacitor electrically connected between the first loopback impedance and the first transmit port, and a second transmit port DC blocking capacitor electrically connected between the second loopback impedance and the second transmit port. ### Claim 6 (depends on 1) The front-end system of claim 1 further comprising a low noise amplifier electrically connected between the antenna port and the receive port in a receive path. ### Claim 7 (depends on 6) The front-end system of claim 6 further comprising an input switch electrically connected between an input of the low noise amplifier and the antenna port, and an output switch electrically connected between an output of the low noise amplifier and the receive port. ### Claim 8 (depends on 1) The front-end system of claim 1 wherein the plurality of radio frequency switches further include a first antenna switch electrically connected between the first transmit port and the antenna port, and a second antenna switch electrically connected between the second transmit port and the antenna port. ### Claim 9 (depends on 8) The front-end system of claim 8 further comprising a first antenna port DC blocking capacitor electrically connected in series with the first antenna switch between the first loopback impedance and the antenna port, and a second antenna port DC blocking capacitor electrically connected in series with the second antenna switch between the second loopback impedance and the antenna port. ### Claim 10 A method of loopback in a front-end system, the method comprising: transmitting a first transmit signal from a first transmit port to an antenna port; generating a first loopback signal in response to the first transmit signal using a first loopback impedance connected between the first transmit port and the receive port by way of a first loopback selection switch and a shared back switch; transmitting a second transmit signal from a second transmit port to the antenna port; and generating a second loopback signal in response to the second transmit signal using a second loopback impedance connected between the second transmit port and the receive port by way of a second loopback selection switch and the shared back switch. ### Claim 11 (depends on 10) The method of claim 10 further comprising providing termination using a shared termination circuit that is electrically connected between a first end of the shared back switch and ground. ### Claim 12 (depends on 10) The method of claim 10 further comprising transmitting the first transmit signal through a first antenna switch that is between the first transmit port and the antenna port, and transmitting the second transmit signal through a second antenna switch that is between the second transmit port and the antenna port. ### Claim 13 (depends on 10) The method of claim 10 further comprising amplifying a receive signal from the antenna port to generate an amplified receive signal using a low noise amplifier, and providing the amplified receive signal to the receive port. ### Claim 14 (depends on 10) The method of claim 10 further comprising transmitting a third transmit signal from a third transmit port to the antenna port, and generating a third loopback signal in response to the third transmit signal using a third loopback impedance connected between the third transmit port and the receive port by way of a third loopback selection switch and the shared back switch. ### Claim 15 A packaged module comprising: a package substrate; and a semiconductor die attached to the package substrate, the semiconductor die including a first transmit port, a second transmit port, a receive port, an antenna port, a first loopback selection switch, a second loopback selection switch, a shared back switch, a first loopback impedance, and a second loopback impedance, the first loopback impedance connected between the first transmit port and the receive port by way of the first loopback selection switch and the shared back switch, and the second loopback impedance connected between the second transmit port and the receive port by way of the second loopback selection switch and the shared back switch. ### Claim 16 (depends on 15) The packaged module of claim 15 wherein the semiconductor die further includes a shared termination circuit connected between a first end of the shared back switch and ground, and a receive port DC blocking capacitor connected between a second end of the shared back switch and the receive port. ### Claim 17 (depends on 16) The packaged module of claim 16 wherein the shared termination circuit includes a termination resistor and a termination capacitor electrically connected in series. ### Claim 18 (depends on 16) The packaged module of claim 16 wherein the semiconductor die further includes a first loopback DC blocking capacitor connected between the first end of the shared back switch and the first loopback impedance, and a second loopback DC blocking capacitor connected between the first end of the shared back switch and the second loopback impedance. ### Claim 19 (depends on 15) The packaged module of claim 15 wherein the semiconductor die further includes a third transmit port, a third loopback selection switch, and a third loopback impedance, the third loopback impedance connected between the third transmit port and the receive port by way of the third loopback selection switch and the shared back switch. ### Claim 20 (depends on 15) The packaged module of claim 15 wherein the semiconductor die further includes a low noise amplifier electrically connected between the antenna port and the receive port in a receive path.