# US 12,184,319 B2 · Indirect reflection detection for receiver circuitry protection in TDD transceivers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,319 B2 - Document ID: US12184319B2 - Status: Granted - Kind: B2 - Application number: 17/574,369 - Filed: 2022-01-12 - Published: 2022-07-14 - Granted: 2024-12-31 - Earliest claimed: 2021-01-14 - Assignees: Outdoor Wireless Networks LLC - Applicants: Outdoor Wireless Networks LLC - Inventors: Johannes Steigert; Rainer Friedrich - Web page: https://patentgrep.com/patent/US12184319B2 ## CPC - 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) - H01Q 1/246: {specially adapted for base stations} - H04B 1/44: Transmit/receive switching - H04B 1/54: using the same frequency for two directions of communication (H04B1/44 takes precedence) - H04B 17/101: {for measurement of specific parameters of the transmitter or components thereof} - H04B 17/102: {Power radiated at antenna} - H04B 17/23: Indication means, e.g. displays, alarms, audible means - H04B 17/354: Adjacent channel leakage power - H04B: TRANSMISSION - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract In an example, a receiver protection circuit includes a directional coupler configured to be coupled to a receive signal path of a communications device between an isolation device and an amplifier of the receive signal path. The receiver protection circuit further includes a power detector coupled to the directional coupler and configured to measure a power level of a transmit leakage signal in the receive signal path. The receiver protection circuit further includes a comparator configured to compare the measured power level of the transmit leakage signal in the receive signal path to a threshold value and output an alarm signal indicating that the measured power level of the transmit leakage signal exceeds the threshold value. ## Claims ### Claim 1 A communications device, comprising: a transmit signal path; a receive signal path; an isolation device coupled to the transmit signal path and the receive signal path, wherein the isolation device is configured to provide an analog transmit signal from the transmit signal path to an antenna port of the isolation device, wherein the isolation device is configured to provide an analog receive signal from the antenna port to the receive signal path; a coupler coupled to the receive signal path between the isolation device and an amplifier of the receive signal path; a power detector coupled to the coupler and configured to measure a power level of a transmit leakage signal in the receive signal path; and a comparator configured to compare the measured power level of the transmit leakage signal to a first threshold value and output a first alarm signal indicating that the measured power level of the transmit leakage signal exceeds the first threshold value; wherein the communications device is configured to reduce a transmit output power in response to the first alarm signal. ### Claim 2 (depends on 1) The communications device of claim 1, wherein the communications device is configured to reduce the transmit output power by: turning off a driver stage in the transmit signal path; reducing a supply voltage of the driver stage in the transmit signal path; reducing a supply voltage of a power amplifier in the transmit signal path; attenuating a signal traversing the transmit signal path; and/or switching off a bias signal for a power amplifier in the transmit signal path. ### Claim 3 (depends on 1) The communications device of claim 1, further comprising: a resistor and a thermistor that form a passive compensation circuit; wherein the communications device is configured to adjust the first threshold value based on an output of the passive compensation circuit. ### Claim 4 (depends on 1) The communications device of claim 1, further comprising: a temperature sensor; a humidity sensor; and a controller configured to adjust the first threshold value based on a temperature measurement from the temperature sensor and a humidity measurement from the humidity sensor. ### Claim 5 (depends on 1) The communications device of claim 1, further comprising a switch in the receive signal path, wherein the switch is positioned between the coupler and the amplifier, wherein the switch is configured to provide the analog receive signal to the amplifier in a first state, wherein the switch is coupled to a termination in a second state; wherein the communications device is configured to control the switch to be in the first state or the second state based on a time-division duplexing schedule. ### Claim 6 (depends on 5) The communications device of claim 5, wherein the communications device is configured to control the switch to be in the second state in response to the first alarm signal. ### Claim 7 (depends on 1) The communications device of claim 1, wherein the first threshold value is determined based on a known relationship between return loss at the antenna port and isolation between the transmit signal path and the receive signal path. ### Claim 8 (depends on 1) The communications device of claim 1, wherein the isolation device is a circulator. ### Claim 9 (depends on 1) The communications device of claim 1, wherein the power detector is a peak power detector. ### Claim 10 (depends on 1) The communications device of claim 1, wherein the communications device is one of: a remote unit of a distributed antenna system; a radio frequency repeater; a radio point for a small cell; an access point; or a remote radio head of a base station. ### Claim 11 (depends on 1) The communications device of claim 1, wherein the comparator is configured to compare the measured power level of the transmit leakage signal to a second threshold value that is different than the first threshold value and output a second alarm signal indicating that the measured power level of the transmit leakage signal exceeds the second threshold value; wherein the communications device is configured to reduce the transmit output power in response to the second alarm signal. ### Claim 12 A method of protecting receiver circuitry, comprising: measuring a power level of a transmit leakage signal in a receive signal path; comparing the measured power level of the transmit leakage signal to a threshold voltage; outputting an alarm signal indicating that the measured power level of the transmit leakage signal exceeds the threshold voltage; and reducing a transmit output power in response to the alarm signal. ### Claim 13 (depends on 12) The method of claim 12, wherein reducing the transmit output power includes: turning off a driver stage in a transmit signal path; reducing a supply voltage of the driver stage in the transmit signal path; reducing a supply voltage of a power amplifier in the transmit signal path; attenuating a signal traversing the transmit signal path; and/or switching off a bias signal for a power amplifier in the transmit signal path. ### Claim 14 (depends on 12) The method of claim 12, further comprising controlling a switch in the receive signal path to be in a first state or a second state based on a time-division duplexing schedule, wherein the switch is configured to provide an analog receive signal to an amplifier of the receive signal path in the first state, wherein the switch is coupled to a termination in the second state. ### Claim 15 (depends on 14) The method of claim 14, further comprising controlling the switch to be in the second state in response to the alarm signal. ### Claim 16 A receiver protection circuit, comprising: a directional coupler configured to be coupled to a receive signal path of a communications device between an isolation device and an amplifier of the receive signal path; a power detector coupled to the directional coupler and configured to measure a power level of a transmit leakage signal in the receive signal path; and a comparator configured to compare the measured power level of the transmit leakage signal in the receive signal path to a first threshold value and output a first alarm signal indicating that the measured power level of the transmit leakage signal exceeds the first threshold value. ### Claim 17 (depends on 16) The receiver protection circuit of claim 16, further comprising: a resistor and a thermistor that form a passive compensation circuit; wherein the first threshold value used by the comparator is configured to be adjusted based on an output of the passive compensation circuit. ### Claim 18 (depends on 16) The receiver protection circuit of claim 16, further comprising: a temperature sensor; a humidity sensor; and a microcontroller configured to adjust the first threshold value based on a temperature measurement from the temperature sensor and a humidity measurement from the humidity sensor. ### Claim 19 (depends on 16) The receiver protection circuit of claim 16, wherein the power detector is a peak power detector. ### Claim 20 (depends on 16) The receiver protection circuit of claim 16, wherein the comparator is configured to compare the measured power level of the transmit leakage signal to a second threshold value that is different than the first threshold value and output a second alarm signal indicating that the measured power level of the transmit leakage signal exceeds the second threshold value; wherein the communications device is configured to reduce a transmit output power in response to the second alarm signal.