High-isolation transmit/receive switch on CMOS for millimeter-wave applications
View Patent ↗A CMOS monolithic transmit/receive switch comprises a single pole double throw switch (SPDT) module operable to selectively connect an antenna port to either a transmit port or to a receive port. A transmit matching network comprising a first transmission line matches the impedance of the transmit port of the SPDT module to a transmit impedance, and a first shunt transistor is operable to selectively ground a transmitter end of the first transmission line. A receive matching network comprising a second transmission line matches the impedance of the receive port of the SPDT module to a receive impedance, and a second shunt transistor is operable to selectively ground a receiver end of the second transmission line.
1. A CMOS monolithic transmit/receive (T/R) switch comprising:
a single pole double throw switch (SPDT) module operable to selectively connect an antenna port to either a transmit port or to a receive port;
a transmit matching network comprising a first transmission line matching the impedance of the transmit port of the SPDT module to a transmit impedance, and a first shunt transistor operable to selectively ground a transmitter end of the first transmission line; and
a receive matching network comprising a second transmission line matching the impedance of the receive port of the SPDT module to a receive impedance, and a second shunt transistor operable to selectively ground a receiver end of the second transmission line.
2. The T/R switch of claim 1 , further comprising an antenna matching network comprising a third transmission line and a shunt capacitor, to match the impedance of the antenna port of the SPDT module to an antenna impedance.
3. The T/R switch of claim 1 , wherein the shunt transistor of the transmitter matching network is controlled by a RxON input of the SPDT core so as to ground the transmitter end of the first transmission line during a receive stage.
4. The T/R switch of claim 1 , wherein the shunt transistor of the receiver matching network is controlled by a TxON input of the SPDT core so as to ground the receiver end of the second transmission line during a transmit stage.
5. The T/R switch of claim 1 , wherein an operational frequency of the switch comprises 57-66 GHz.
6. The T/R switch of claim 1 wherein the switch is fabricated on a 130 nm process and wherein control voltages controlling the SPDT module and the first and second shunt transistors are 1.2 V and 0 V so as to provide for direct T/R switch control.
7. The T/R switch of claim 1 wherein transistors of the switch are fabricated with a minimum allowable channel length to minimize Ron.
8. The T/R switch of claim 1 further comprising biasing circuitry to bias the source/drain of all transistors to 0 V to minimize Ron.
9. The T/R switch of claim 1 wherein the first and second transmission lines are fabricated with a signal line formed in a top CMOS metal layer and with a ground layer formed in a lowest CMOS metal layer (M1).
10. A method of transmit/receive switching, the method comprising:
using a single pole double throw switch (SPDT) module to selectively connect an antenna port to either a transmit port or to a receive port;
impedance matching a transmitter to the transmit port by connecting a first transmission line between the transmitter and the transmit port;
selectively grounding a transmitter end of the first transmission line, to isolate the transmitter during receive periods;
impedance matching a receiver to the receive port by connecting a second transmission line between the receiver and the receive port; and
selectively grounding a receiver end of the second transmission line, to isolate the receiver during transmit periods.
11. A fully integrated CMOS millimeter wave transceiver comprising a transmit/receive switch in accordance with claim 1 .