RF antenna switch and method of operating the same

• US 5,630,213 A
• Filed: 06/14/1995
• Issued: 05/13/1997
• Est. Priority Date: 12/22/1992
• Status: Expired due to Term

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Vannatta, Louis J.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): LE, THANH C
• Application Number:
  US08/490,523
• Time in Patent Office: 699 Days
• Field of Search: 455/78, 455/82, 455/83, 455/84, 455/89, 455/132, 455/133, 455/134, 455/137, 455/140, 455/188.1, 455/188.2, 455/189.1, 455/191.3, 455/192.1, 455/272, 455/273 , 455/277.1, 455/280, 455/323, 455/325, 455/326
• US Class Current: 455/133
• CPC Class Codes: H04B 7/0817 with multiple receivers and antenna path selection
• CPC Class Codes: H04B 7/082 selecting best antenna path

Abstract

A radio frequency (RF) antenna switch (136) and associated method of operating the same is provided for switching between a first antenna (109) and a second antenna (111). A first mixer (125) has an input terminal 124 coupled to the first antenna (109) and has an output terminal 126. A second mixer (129) has an input terminal 128 coupled to the second antenna (111) and has an output terminal 130 coupled to the output terminal of the first mixer (125). The first mixer (125) and the second mixer (129) are alternatively enabled responsive to the state of an antenna select signal (141). Additionally, the common output terminals 126 and 130 of both the first mixer (125) and the second mixer (129) are matched to a first intermediate frequency stage (131). The RF antenna switch (136) advantageously provides low loss and low current drain.

Claims

1. An antenna switch operative to switch between at least a first antenna and a second antenna comprising:

a first active mixer having an input terminal coupled to the first antenna and having an output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled;

a second active mixer having an input terminal coupled to the second antenna and having an output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled;

a matching network directly connected to the output terminal of the first active mixer and the output terminal of the second active mixer, the matching network having an input impedance; and

a controller operative to alternatively enable the first and the second active mixers, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network.

2. An antenna switch according to claim 1 wherein the first antenna receives a first signal in a first predetermined frequency band and the second antenna receives a second signal in a second predetermined frequency band.

3. An antenna switch according to claim 2 wherein the first and second signals are in substantially the same predetermined frequency band.

4. An antenna switch according to claim 2 wherein the first and second signals are in substantially different predetermined frequency bands.

5. An antenna switch according to claim 1 wherein the matching network further comprises:

a first transmission line having an input terminal directly connected to the output terminal of the first active mixer, and having an output terminal; and

a second transmission line having an input terminal directly connected to the output terminal of the second active mixer, and having an output terminal;

wherein the output terminal of the first transmission line is connected to the output terminal of the second transmission line.

6. A receiver comprising:

at least a first antenna and a second antenna;

an antenna switch operative to switch between the first antenna and the second antenna, including;

a first active mixer having an input terminal coupled to the first antenna and having an output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled;

a second active mixer an input terminal coupled to the second antenna and having an output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled;

a matching network directly connected to the output terminal of the first active mixer and the output terminal of the second active mixer, the matching network having an .input impedance; and

a controller operative to alternatively enable the first and the second active mixers, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network; and

a demodulator coupled to the matching network.

7. A receiver according to claim 6 wherein the matching network further comprises:

a first transmission line having an input terminal directly connected to the output terminal of the first active mixer, and having an output terminal; and

a second transmission line having an input terminal directly connected to the output terminal of the second active mixer, and having an output terminal;

wherein the output terminal of the first transmission line is connected to the output terminal of the second transmission line.

8. A transceiver comprising:

at least a first antenna and a second antenna;

a transmitter coupled to the second antenna; and

a receiver coupled to the first antenna and the second antenna, including;

an antenna switch operative to switch between the first antenna and the second antenna, the antenna switch including;

a first active mixer having an input terminal coupled to the first antenna and having an output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled;

a second active mixer having an input terminal coupled to the second antenna and having an output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled;

a matching network directly connected to output terminal of the first active mixer and the output terminal of the second active mixer, the matching network having an input impedance; and

a controller operative to alternatively enable the first and the second active mixers, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network; and

a demodulator coupled to the matching network.

9. A transceiver according to claim 8 wherein the matching network further comprises:

a first transmission line having an input terminal directly connected to the output terminal of the first active mixer, and having an output terminal; and

a second transmission line having an input terminal directly connected to the output terminal of the second active mixer, and having an output terminal;

wherein the output terminal of the first transmission line is connected to the output terminal of the second transmission line.

10. A receiver comprising:

a first path for receiving a first radio frequency (RF) signal including in series;

a first antenna, a first bandpass filter, a first matching network and a first active mixer, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled;

a second path for receiving a second RF signal including in series;

a second antenna, a second bandpass filter, a second matching network and a second active mixer, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled;

a third matching network directly connected to the first path and the second path at an output terminal of the first active mixer and an output terminal of the second active mixer, respectively, the third matching network having an input impedance; and

a controller operative to alternatively enable the first active mixer and the second active mixer to alternatively couple the first RF signal and the second RF signal, respectively, to the third matching network, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network.

11. A receiver according to claim 11 wherein the matching network further comprises:

a first transmission line having an input terminal directly connected to the output terminal of the first active mixer, and having an output terminal; and

a second transmission line having an input terminal directly connected to the output terminal of the second active mixer, and having an output terminal;

wherein the output terminal of the first transmission line is connected to the output terminal of the second transmission line.

12. A method for switching between at least a first antenna and a second antenna comprising the step of:

alternatively enabling first and second active mixers, the first active mixer has an input terminal coupled to the first antenna and has an output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled the second active mixer has an input terminal coupled to the second antenna and has an output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled, the output terminal of the first active mixer and the output terminal of the second active mixer are directly connected to a matching network, the matching network having an input impedance, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network.

13. A method for receiving a radio frequency (RF) signal received by at least one of a first antenna and a second antenna, comprising the steps of:

alternatively enabling first and second active mixers, the first active mixer has an input terminal coupled to the first antenna and has an output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled the second active mixer has an input terminal coupled to the second antenna and has an output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled, the output terminal of the first active mixer and the output terminal of the second active mixer are directly connected to a matching network, the matching network having an input impedance, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network; and

demodulating the RF signal present at the output terminal of at least one of the first active mixer and the second active mixer.

14. A method of operating a receiver comprising the steps of:

receiving a first radio frequency (RF) signal via a first path including in series;

a first antenna, a first bandpass filter, a first matching network, a first active mixer and a first output terminal, the first active mixer having a first output impedance when the first active mixer is enabled and a second output impedance when the first active mixer is disabled;

receiving a second RF signal via a second path including in series;

a second antenna, a second bandpass filter, a second matching network, a second active mixer, and a second output terminal, the second active mixer having a first output impedance when the second active mixer is enabled and a second output impedance when the second active mixer is disabled, wherein an output terminal of the first active mixer and an output terminal of the second active mixer are directly connected to a third matching network, the third matching network having an input impedance; and

alternatively enabling the first active mixer and the second active mixer for alternatively coupling the first RF signal and the second RF signal, respectively, to the matching network, the first output impedance of the first active mixer in combination with the second output impedance of the second active mixer matching the input impedance of the matching network, and the second output impedance of the first active mixer in combination with the first output impedance of the second active mixer matching the input impedance of the matching network.