TRANSMITTER FRONT END WITH PROGRAMMABLE NOTCH FILTER AND METHODS FOR USE THEREWITH

• US 20130109334A1
• Filed: 12/18/2011
• Published: 05/02/2013
• Est. Priority Date: 10/28/2011
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Afsahi, Ali, Behzad, Arya Reza, Kwon, Dae
• Granted Patent: US 9,065,504 B2
• Time in Patent Office: Days
• US Class Current: 455/114.3
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0433 with linearisation using feedback

Abstract

A radio transmitter front end for use in a radio frequency (RF) transceiver includes at least one amplifier stage operable to generate a transmit signal in response to an upconverted signal. A feedback generator is operable to generate a transmit feedback signal in response to the transmit signal. A control signal generator is operable to generate at least one filter control signal in response to the transmit feedback signal. A notch filter is operable to filter out of band noise while passing in-band frequencies to the at least one amplifier stage, under control of the at least one filter control signal.

Claims

1. A radio transmitter front end for use in a radio frequency (RF) transceiver, the radio transmitter front end comprising:

at least one amplifier stage operable to generate a transmit signal in response to an upconverted signal;

a feedback generator, coupled to the at least one amplifier stage, operable to generate a transmit feedback signal in response to the transmit signal;

a control signal generator, coupled to the feedback signal generator, operable to generate at least one filter control signal in response to the transmit feedback signal; and

a notch filter, coupled to the control signal generator and the at least one amplifier stage, operable to filter out of band noise while passing in-band frequencies to the at least one amplifier stage, under control of the at least one filter control signal.

2. The radio transmitter front end of claim 1 wherein the feedback generator includes a transmit signal strength indicator.

3. The radio transmitter front end of claim 1 wherein the feedback generator includes at least a portion of a receive path of a receiver included in the RF transceiver.

4. The radio transmitter front end of claim 1 wherein the at least one amplifier stage includes a power amplifier driver and a power amplifier and wherein the notch filter is coupled between the power amplifier driver and the power amplifier.

5. The radio transmitter front end of claim 1 wherein the at least one amplifier stage includes a power amplifier driver and a power amplifier and wherein the notch filter is coupled filter input signals to the power amplifier driver.

6. The radio transmitter front end of claim 1 wherein the at least one amplifier stage includes a power amplifier driver and a power amplifier and the radio transmitter front end includes a switch matrix, coupled to the power amplifier driver and the power amplifier operable in response to a configuration control signal generated by the control signal generator to selectively couple the notch filter between the power amplifier driver and the power amplifier to filter input signals to the power amplifier in a first mode of operation and to couple the notch filter to filter input signals to the power amplifier driver in a second mode of operation.

7. The radio transmitter front end of claim 1 wherein the at least one amplifier stage includes a cascode amplifier having a plurality of cascode transistors and a plurality of transconductance transistors and wherein the notch filter is coupled between the plurality of cascode transistors and the plurality of transconductance transistors.

8. The radio transmitter front end of claim 1 wherein the notch filter includes a inductor and a first capacitor that forms a series tank with the inductor, and a second capacitor in parallel with the series tank, wherein a capacitance of at least one of:

the first capacitor and the second capacitor is controlled via the at least one filter control signal.

9. The radio transmitter front end of claim 8 wherein the notch filter includes an active quality (Q) boost circuit having at least one transistor, the quality boost circuit coupled to boost a quality of the series tank.

10. The radio transmitter front end of claim 1 wherein the RF transceiver operates in accordance with an 802.11ac standard.

11. A method for use in a radio frequency (RF) transceiver, the method comprising:

generating a transmit signal in response to an upconverted signal via at least one amplifier stage;

generating a transmit feedback signal in response to the transmit signal;

generating at least one filter control signal in response to the transmit feedback signal; and

controlling a programmable notch filter based on the at least one filter control signal to filter out of band noise while passing in-band frequencies to the at least one amplifier stage.

12. The method of claim 11 wherein the transmit feedback signal indicates a transmit signal strength of the in-band frequencies.

13. The method of claim 11 wherein generating the transmit feedback signal uses at least a portion of a receive path of a receiver included in the RF transceiver.

14. The method of claim 11 wherein the at least one amplifier stage includes a power amplifier driver and a power amplifier and the method further comprises:

coupling the notch filter between the power amplifier driver and the power amplifier.

15. The method of claim 11 wherein the at least one amplifier stage includes a power amplifier driver and a power amplifier and the method further comprises:

coupling the notch filter to filter input signals to the power amplifier driver.

16. The method of claim 11 wherein the at least one amplifier stage includes a power amplifier driver, a power amplifier and a switch matrix, and the method further comprises:

controlling the switch matrix to selectively couple the notch filter between the power amplifier driver and the power amplifier to filter input signals to the power amplifier in a first mode of operation; and

to selectively couple the notch filter to filter input signals to the power amplifier driver in a second mode of operation.

17. The method of claim 11 wherein the at least one amplifier stage includes a cascode amplifier having a plurality of cascode transistors and a plurality of transconductance transistors and the method further comprises:

coupling the notch filter between the plurality of cascode transistors and the plurality of transconductance transistors.

18. The method of claim 11 wherein the notch filter includes a inductor and a first capacitor that forms a series tank with the inductor, and a second capacitor in parallel with the series tank, and controlling the programmable notch filter can operate by controlling, via the at least one filter control signal, a capacitance of at least one of:

the first capacitor and the second capacitor.

19. The method of claim 18 further comprising:

boosting a quality of the series tank via an active quality (Q) boost circuit having at least one transistor.

20. The method of claim 11 wherein the RF transceiver operates in accordance with an 802.11ac standard.