RF transformer based TX/RX integrated RF switch

Patent metadata

Field	Value
Publication number	US-9484977-B2
Application number	US-201414277427-A
Country	US
Kind code	B2
Filing date	May 14, 2014
Priority date	May 14, 2014
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

The present invention is a novel and useful RF transformer based transmit/receive (TX/RX) integrated RF switch. In one embodiment of the invention, the TX/RX RF switch circuit is based on the use of an RF transformer which functions as (1) the PA output transformer during TX mode and (2) as a series inductance in an LNA matching network during receive mode. Thus, the RF transformer plays a dual function or role. Antenna diversity is achieved by having multiple antennas each having an associated antenna switch connected to the output transformer. The TX/RX switch of the invention reduces the number of switches required for antenna diversity to a minimum and minimizes RF losses in the system. The TX/RX switch is suitable for use with modern wireless communication standards such as DECT, 802.11 WLAN, Bluetooth, ZigBee, etc. The configuration of the TX/RX circuit permits the use of common, relatively low cost semiconductor fabrication techniques such as standard CMOS processes.

First claim

What is claimed is:

1. An integrated transmit/receive (TX/RX) radio frequency (RF) switch, comprising:
an output transformer having a primary coil coupled to a transmit (TX) circuit, and a secondary coil having a first end coupled to an antenna;
a switch operative to electrically couple a second end of said secondary coil of said output transformer to ground in accordance with a switch control signal;
wherein in a TX mode of operation, said switch is on and power is transferred from said TX circuit to said antenna; and
wherein in a receive (RX) mode of operation, said switch is off and an RF signal from said antenna is transferred to a RX circuit coupled thereto.

2. The integrated TX/RX RF switch according to claim 1 , wherein said secondary coil functions as a power amplifier output transformer as well as a series inductance as part of an low noise amplifier (LNA) input matching network.

3. The integrated TX/RX RF switch according to claim 1 , wherein during said RX mode of operation, TX power amplifier biasing circuits are turned off.

4. The integrated TX/RX RF switch according to claim 1 , wherein during said RX mode of operation, a floating switching controlled ground of said secondary coil of said output transformer is electrically connected to an input of an LNA circuit.

5. The integrated TX/RX RF switch according to claim 1 , wherein during said TX mode of operation, said secondary coil of said output transformer is electrically coupled to ground.

6. The integrated TX/RX RF switch according to claim 1 , wherein said output transformer comprises an integrated semiconductor transformer.

7. The integrated TX/RX RF switch according to claim 1 , wherein the on voltage drop of said switch is minimized such that the impedance of an low noise amplifier (LNA) Balun in parallel with said switch is substantially negligible.

8. The integrated TX/RX RF switch according to claim 1 , wherein a low noise amplifier (LNA) circuit coupled to said switch is turned off during said TX mode of operation to reduce power consumption.

9. The integrated TX/RX RF switch according to claim 1 , wherein a low noise amplifier (LNA) circuit coupled to said switch remains on during said TX mode of operation without suffering substantial damage.

10. The integrated TX/RX RF switch according to claim 1 , further comprising an electrostatic discharge (ESD) protection capacitor coupled between said switch and said second end of said secondary coil of said output transformer.

11. An integrated transmit/receive (TX/RX) radio frequency (RF) switch, comprising:
an output transformer having a primary coil coupled to a transmit (TX) circuit and a secondary coil having a first end and a second end;
a plurality of antennas;
a plurality of antenna switches, each switch in series with a respective antenna and coupled to the first end of said secondary coil of said output transformer;
a TX/RX switch operative to electrically couple the second end of said secondary coil of said output transformer to ground in accordance with a switch control signal;
wherein in a TX mode of operation, said switch is on and power is transferred from said TX circuit to one or more of said antennas; and
wherein in a receive (RX) mode of operation, said switch is off and an RF signal from one or more of said antennas is transferred to an RX circuit coupled thereto.

12. The integrated TX/RX RF switch according to claim 11 , wherein antenna diversity is achieved requiring N+1 active transistor switches, where N is the number of antennas.

13. The integrated TX/RX RF switch according to claim 11 , wherein said secondary coil functions as a power amplifier output transformer as well as a series inductance as part of an LNA input matching network.

14. The integrated TX/RX RF switch according to claim 11 , wherein during said RX mode of operation, TX power amplifier biasing circuits are turned off.

15. The integrated TX/RX RF switch according to claim 11 , wherein during said RX mode of operation, a floating switching controlled ground of said secondary coil of said output transformer is electrically connected to an input of an LNA circuit.

16. The integrated TX/RX RF switch according to claim 11 , wherein during said TX mode of operation, said secondary coil of said output transformer is electrically coupled to ground.

17. The integrated TX/RX RF switch according to claim 11 , wherein said output transformer comprises an integrated semiconductor transformer.

18. The integrated TX/RX RF switch according to claim 11 , wherein the on voltage drop of said switch is minimized such that the impedance of an LNA Balun in parallel with said switch is substantially negligible.

19. The integrated TX/RX RF switch according to claim 11 , wherein an LNA circuit coupled to said switch is turned off during said TX mode of operation to reduce power consumption.

20. The integrated TX/RX RF switch according to claim 11 , wherein a low noise amplifier (LNA) circuit coupled to said switch remains on during said TX mode of operation without suffering damage.

21. The integrated TX/RX RF switch according to claim 11 , further comprising an electrostatic discharge (ESD) protection capacitor coupled between said switch and said second end of said secondary coil of said output transformer.

22. A radio frequency (RF) front end module (FEM), comprising:
an RF switch coupled to one or more antennas and operative to receive and transmit RF signals in one or more frequency bands, said RF switch comprising:
an output transformer having a primary coil coupled to a transmit (TX) circuit, and a secondary coil having a first end coupled to an antenna;
a switch operative to electrically couple a second end of said secondary coil of said output transformer to ground in accordance with a switch control signal;
wherein in a TX mode of operation, said switch is on and power is transferred from said TX circuit to said antenna;
wherein in a receive (RX) mode of operation, said switch is off and an RF signal from said antenna is transferred to a RX circuit coupled thereto;

a power amplifier circuit adapted to receive a TX RF input signal and generate an RF output signal input to said RF switch; and
a low noise amplifier (LNA) adapted to receive an RF input signal from said RF switch and generate an RX RF input signal.

23. The RF FEM according to claim 22 , wherein said secondary coil functions as a power amplifier output transformer as well as a series inductance as part of a low noise amplifier (LNA) input matching network.

24. The RF FEM according to claim 22 , wherein during said RX mode of operation, TX power amplifier biasing circuits are turned off.

25. The RF FEM according to claim 22 , wherein during said RX mode of operation, a floating switching controlled ground of said secondary coil of said output transformer is electrically connected to an input of a low noise amplifier (LNA) circuit.

26. A method of implementing a radio frequency (RF) switch, comprising:
providing an output transformer having a primary and secondary winding;
coupling said primary winding to a transmit (TX) circuit and one end of said secondary winding to an antenna;
switching said second end of said secondary winding to ground in accordance with a control signal;
turning said switch on in a TX mode of operation whereby power is transferred from said TX circuit to said antenna; and
turning said switch off in a

Assignees

• Dsp Group Ltd

Inventors

• Anderson Sergey
• Betzalel Sharon

Classifications

• H04B1/48

  in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter {(H04B1/46 takes precedence)} · CPC title

• H04B1/44 Primary

  Transmit/receive switching · CPC title