RF front-end with wideband transmitter/receiver isolation
View Patent ↗Embodiments of a four-port isolation module are presented herein. In an embodiment, the isolation module includes a step-up autotransformer comprising a first and second winding that are electrically coupled in series at a center node. The first port of the isolation module is configured to couple an antenna to a first end node of the series coupled windings. The second port of the isolation module is configured to couple a balancing network to a second end node of the series coupled windings. The third port is configured to couple a transmit path to the center node. The fourth port is configured to couple a differential receive path across the first end node and the second end node. The isolation module effectively isolates the third port from the fourth port to prevent strong outbound signals received at the third port from saturating an LNA coupled to the fourth port.
1. An isolation module, comprising:
a step-up autotransformer comprising a first winding and a second winding that are electrically coupled in series at a center node to form series coupled windings;
a first port configured to couple an antenna to a first end node of the series coupled windings;
a second port coupled to a balancing network at a second end node of the series coupled windings;
a third port coupled to a transmit path at the center node; and
a fourth port coupled to a differential receive path across the first end node and the second end node,
wherein an impedance of the balance network is adjusted based on a change in a ratio of a number of turns in the first winding to a number of turns in the second winding away from a value of one.
2. The isolation module of claim 1 , wherein an outbound signal carried by the transmission path appears common mode across the differential receive path.
3. The isolation module of claim 2 , wherein the outbound signal has an associated power.
4. The isolation module of claim 3 , wherein a first portion of the outbound signal power is transferred to the antenna and a second portion of the outbound signal power is transferred to the balancing network.
5. The isolation nodule of claim 4 , wherein the first portion and second portion are substantially determined based on the ratio of the number of turns in the first winding to the number of turns in the second winding.
6. The isolation module of claim 5 , wherein the number of turns in the first winding equals the number of turns in the second winding, and substantially half of the outbound signal power is transferred to the antenna and half of the outbound signal power is transferred to the balancing network.
7. The isolation module of claim 5 , wherein the number of turns in the second winding is greater than the number of turns in the first winding, and more of the outbound signal power is transferred to the antenna than the balancing network.
8. The isolation module of claim 1 , wherein the impedance of the balancing network is substantially equal to an impedance of the antenna.
9. The isolation module of claim 1 , wherein the impedance of the balancing network is further adjusted based on an impedance of the antenna.
10. The isolation module of claim 1 , wherein the balancing network further comprises a tunable capacitor and a tunable resistor.
11. The isolation module of claim 1 , wherein the antenna receives an inbound signal and couples the inbound signal to the differential receive path.
12. An isolation module, comprising:
a step-up autotransformer comprising a first winding and a second winding that are electrically coupled in series at a center node to form series coupled windings;
a first port configured to couple an antenna to a first end node of the series coupled windings;
a second port coupled to a balancing network at a second end node of the series coupled windings;
a third port coupled to an output of a power amplifier (PA) at the center node; and
a fourth port coupled to an input of a low-noise amplifier (INA) across the first end node and the second end node,
wherein an impedance of the balance network is adjusted based on a change in a ratio of a number of turns in the first winding to a number of turns in the second winding away from a value of one.
13. The isolation module of claim 12 , wherein an outbound signal provided at the output of the PA at the third port appears common mode to the input of the LNA at the fourth port.
14. The isolation module of claim 12 , wherein the impedance of the balancing network is substantially equal to an impedance of the antenna.
15. The isolation module of claim 12 , wherein the impedance of the balancing network is adjusted based on an impedance of the antenna.
16. The isolation module of claim 12 , wherein the balancing network further comprises a tunable capacitor and a tunable resistor.
17. The isolation module of claim 12 , wherein a signal path coupling the antenna at the first port to the LNA at the fourth port is shorter than a wavelength of signals received by the antenna.
18. The isolation module of claim 17 , wherein a voltage on the signal path at a given time is substantially the same at all points on the signal path.
19. The isolation module of claim 17 , wherein the LNA is noise matched.
20. The isolation module of claim 17 , wherein the LNA has a substantially infinite input impedance.