TDD receiver protection
Techniques are provided herein for a receiver protection circuit in a time-division duplex (TDD) system. The receive protection circuit has a first diode with an anode that is coupled to an input of a low-noise-amplifier (LNA) and a cathode that is coupled to a ground. A controller is coupled to the anode of the diode and is configured to generate a control signal for turning on the diode when the TDD system is in a transmission mode. A load is coupled to the diode such that a reflected transmit signal is shorted to the ground by the diode and the radio frequency energy carried in the reflected transmit signal is consumed by the load.
1. An apparatus comprising:
a time-division duplex (TDD) transceiver comprising a transmitter and a receiver, wherein the receiver further comprises a first low-noise-amplifier (LNA);
a first hybrid coupler comprising an input port configured to receive radio frequency (RF) signals, a first output port coupled to an input of the first LNA, a second output port, and an isolation port;
a first diode with an anode coupled to the input of the first LNA and a cathode coupled to a ground (GND);
a first controller coupled to the anode of the first diode and configured to generate a first control signal for turning on the first diode when the TDD transceiver is in a transmission mode; and
a load coupled to the isolation port configured to consume any energy from RF signals reflected to the first and second output ports.
2. The apparatus of claim 1 , wherein the first diode is a p-type, intrinsic, n-type (PIN) diode.
3. The apparatus of claim 1 , wherein the load is a resistive load.
4. The apparatus of claim 1 , further comprising a RF choke coupled on a conduction path that carries the first control signal.
5. The apparatus of claim 1 , wherein the first hybrid coupler has a 3 dB attenuation and 90 degree phase shift.
6. The apparatus of claim 1 , wherein the receiver further comprises a second LNA coupled to the second output port of the first hybrid coupler, and further comprising a second diode coupled to an input of the second LNA, wherein the second diode is turned on during the transmission mode by a second control signal.
7. The apparatus of claim 6 , wherein the second control signal is generated either by a second controller or the first controller.
8. The apparatus of claim 6 , further comprising a second hybrid coupler configured to be coupled to outputs of the first and second LNAs.
9. A system comprising:
a time-division duplex (TDD) transmitter;
a TDD receiver with a first low-noise-amplifier (LNA);
a circulator coupled between the TDD transmitter and TDD receiver;
a receiver protection circuit comprising:
a first diode with an anode coupled to an input of a first low-noise-amplifier (LNA) and a cathode coupled to a ground (GND);
a first controller coupled to the anode of the first diode configured to generate a first control signal for turning on the first diode when the system is in a transmission mode;
a first hybrid coupler coupled between the circulator and the first LNA; and
a load coupled to the first diode through the first hybrid coupler.
10. The system of claim 9 , wherein the first diode is a p-type, intrinsic, n-type (PIN) diode.
11. The system of claim 9 , wherein the load is a resistive load.
12. The system of claim 9 , wherein the first hybrid coupler has a 3 dB attenuation and 90 degree phase shift.
13. The system of claim 9 , wherein the receiver protection circuit further comprises a radio frequency choke coupled on a conduction path that carries the first control signal.
14. The system of claim 9 , wherein the receiver further comprises a second LNA coupled to the first hybrid coupler that is in balance with the first LNA, and the receiver protection circuit further comprises a second diode coupled to an input of the second LNA, wherein the second diode is also turned on during the transmission mode by a second control signal.
15. The system of claim 14 , wherein the second control signal is generated either by a second controller or the first controller.
16. The system of claim 14 , further comprising a second hybrid coupler configured to be coupled to outputs of the first and second LNAs.
17. An apparatus comprising:
a first hybrid coupler comprising an input port configured to receive radio frequency (RF) signals;
a first low-noise-amplifier (LNA) and a second LNA balanced to each other, and both are coupled to the first hybrid coupler;
a first diode with an anode coupled to an input of the first LNA and a cathode coupled to a ground (GND);
a second diode with an anode coupled to an input of the second LNA and a cathode coupled to the GND;
at least one controller coupled to the anodes of both the first and second diodes and configured to generate a control signal for turning on both the first and second diodes; and
a load coupled to the first hybrid coupler configured to consume any energy reflected from RF signals received through the first hybrid coupler.
18. The apparatus of claim 17 , wherein both the first and second diodes are p-type, intrinsic, n-type (PIN) diodes.
19. The apparatus of claim 17 , wherein the load is a resistive load.
20. The apparatus of claim 17 , further comprising a RF choke coupled on a conduction path that carries the first control signal.
21. The apparatus of claim 17 , wherein the first hybrid coupler has a 3 dB attenuation and 90 degree phase shift.
22. The apparatus of claim 17 , further comprising a second hybrid coupler configured to be coupled to outputs of the first and second LNAs.