SYSTEMS AND METHODS RELATED TO IMPROVED ISOLATION BETWEEN TRANSMIT AND RECEIVE RADIO-FREQUENCY SIGNALS

• US 20130273859A1
• Filed: 04/12/2013
• Published: 10/17/2013
• Est. Priority Date: 04/12/2012
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Pehlke, David Richard, King, Joel Richard
• Granted Patent: US 9,496,913 B2
• Time in Patent Office: Days
• US Class Current: 455/78
• CPC Class Codes: H04B 1/0057 using diplexing or multiplexing filters for selecting the desired band
• CPC Class Codes: H04B 1/44 Transmit/receive switching
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04L 43/028 by filtering
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex

Abstract

Disclosed are systems and methods for improving isolation between transmit and receive radio-frequency (RF) signals. In some embodiments, a system can be implemented for isolating RF signals during Tx and Rx operations. The system can include a Tx path and an Rx path, with the Tx path having a filter. In some embodiments, the Tx path can include a power amplifier having a plurality of interstages and an output stage, and the filter can be implemented at one of the interstages and before the output stage. The system can further include first and second antennas connected respectively to the Tx and Rx paths. The Tx path, the Rx path, and/or the first and second antennas can be configured to yield a desired level of isolation between the RF signal in the Tx and Tx paths.

Claims

1. A system for isolating radio-frequency (RF) signals during Tx and Rx operations, the system comprising:

a transmit path configured for passage of a first RF signal;

a first filter disposed along the transmit path and configured to filter the first RF signal;

a first antenna connected to the transmit path and configured to transmit the first RF signal; and

a second antenna connected to a receive path and configured to receive a second RF signal, the first and second antennas separated from each other to yield a desired level of isolation between the transmit and receive paths.

2. The system of claim 1 further comprising a second filter disposed along the receive path and configured to filter the second RF signal for processing by a receiver circuit.

3. The system of claim 2 wherein the receive path includes a diversity receive path.

4. The system of claim 2 wherein each of the first and second filters includes a relaxed filtering requirement due at least in part to the separate first and second antennas, the relaxed filtering requirement allowing reduction in insertion losses for both of the transmit and receive paths.

5. The system of claim 4 wherein the relaxed filtering requirement includes a relaxed out-of-band attenuation requirement.

6. The system of claim 2 wherein each of the first and second filter includes a band-pass filter (BPF).

7. The system of claim 1 wherein the transmit path includes a power amplifier having a plurality of interstages.

8. The system of claim 7 wherein the first filter is disposed at one of the interstages and before an output stage of the power amplifier.

9. The system of claim 8 wherein the interstages include a variable-gain stage configured to compensate for variation of insertion loss at the first filter.

10. The system of claim 9 wherein the variation of insertion loss includes insertion loss variation due to change in frequency or temperature.

11. The system of claim 1 further comprising a duplexer path configured to facilitate a duplexer mode where both transmit and receive operations are performed with the first antenna.

12. The system of claim 11 further including a duplexer bypass and one or more switches to allow switching between the duplexer mode and a duplexer bypass mode where both of the first and second antennas are being used.

13. The system of claim 12 wherein the duplexer bypass mode is engaged for bypassing the duplexer over selected regions of dynamic range to optimize performance.

14. The system of claim 13 wherein each of the transmit path, receive path, and duplexer path includes a plurality of channels for facilitating multi-band operations.

15. The system of claim 14 wherein the multi-band operation includes a quad-band for a 3GPP communication standard.

16. The system of claim 12 further comprising a detection system configured to detect a condition for switching between the duplexer mode and the duplexer bypass mode.

17. The system of claim 16 wherein the condition is representative of an antenna isolation environment.

18. The system of claim 17 wherein the antenna isolation environment condition is detected by an Rx diversity measurement analysis, a forward and reflected coupled power measurement, a direct measurement of the first RF signal transmitted, or a comparison to one or more calibrated reference values.

19. A radio-frequency (RF) device comprising:

a transceiver configured to process RF signals;

first and second antennas in communication with the transceiver to facilitate transmission and reception of the RF signals; and

a circuit configured to provide isolation of the RF signals during Tx and Rx operations, the circuit including a transmit path configured for passage of a first RF signal, a first filter disposed along the transmit path and configured to filter the first RF signal, and a transmit node for connecting to the first antenna for transmitting the first RF signal, the circuit further including a receive path configured to receive a second RF signal from the second antenna, the transmit path and the receive path configured to yield a desired level of isolation therebetween.

20. A method for isolating radio-frequency (RF) signals during Tx and Rx operations, the method comprising:

passing a first RF signal through a transmit path;

filtering the first RF signal along the transmit path;

passing the first RF signal to a first antenna to transmit the first RF signal;

receiving a second RF signal through a second antenna;

passing the second RF signal through a receive path, the first and second antennas separated from each other to yield a desired level of isolation between the transmit and receive paths.