RF transmitter with extended efficient power control range

• US 6,681,101 B1
• Filed: 01/11/2000
• Issued: 01/20/2004
• Est. Priority Date: 01/11/2000
• Status: Expired due to Term

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Lindstrom, Mats, Eidson, Brian, Grange, Robert Edmund
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Pan, Yuwen
• Application Number:
  US09/481,094
• Time in Patent Office: 1,470 Days
• Field of Search: 455/118, 455/127.1, 455/245.1, 455/126, 455/127, 455/127.2, 455/127.3, 330/10, 330/103, 330/124.R, 330/284, 330/129, 330/51, 332/103
• US Class Current: 455/127.1
• CPC Class Codes: H03C 3/0925 applying frequency modulation at the divider in the feedback loop
• CPC Class Codes: H03C 3/0933 using fractional frequency division in the feedback loop of the phase locked loop
• CPC Class Codes: H03C 5/00 Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal H03C7/00 takes precedence
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03G 3/004 Control by varying the supply voltage
• CPC Class Codes: H04B 1/04 Circuits

Abstract

A highly efficient radio frequency (RF) transmitter provides both wide bandwidth and an extended power control range. The RF transmitter includes stage switching, bias adjustment, and drain supply modulation. These components are used to provide fine and coarse power control and EER envelope fluctuations. The RF transmitter is useful in wireless communications to increase both handset talk time and battery life.

Claims

1. A radio frequency (RF) transmitter for use in transmitting nonconstant-envelope signals, comprising:

a signal processing block responsive to an input signal;

a supply modulator responsive to an envelope output of the signal processing block;

an FM modulator responsive to a phase output of the signal processing block;

a power amplifier circuit having a plurality of amplifier stages each coupled to the supply modulator, and a plurality of switches configured to bypass selected amplifier stages, and

an envelope modulator coupled between the envelope output and the supply modulator, wherein the supply modulator comprises;

a multiplexer configured to receive a signal from the envelope modulator;

plurality of delay lines connected to the multiplexer and to associated ones of the switches of the amplifiers; and

a plurality of filters connected to corresponding ones of the switches and the drain input terminals, wherein a modulated signal is delivered to selected ones of the amplifiers.

2. The RF transmitter of claim 1, further comprising an attenuator coupled between the FM modulator and the power amplifier circuit.

3. The RF transmitter of claim 2, wherein the supply modulator is configured to drain-bias each amplifier stage through a drain input terminal of the amplifier stage.

4. The RF transmitter of claim 2, wherein the attenuator modulates an output of the RF transmitter under control of the supply modulator during low power operations.

5. The RF transmitter of claim 2, wherein the supply modulator is configured to provide a supply voltage of each of the amplifier stages and an attenuation control voltage to the attenuator.

6. The RF transmitter of claim 5, wherein the attenuator and the amplifier stages are serially cascaded, the switches are configured to each selectably bypass a single amplifier stage, and the supply modulator is configured to modulate, responsive to the envelope signal, only the voltage that it provides to the last unbypassed one of the amplifier stages and the attenuator.

7. The RF transmitter of claim 6, wherein the attenuator is configured to provide a static voltage to all other than the last of the unbypassed ones of the amplifier stages and the attenuator.

8. The RF transmitter of claim 7, wherein the supply modulator is further configured to provide incremental output power control by adjusting one or more DC drain bias levels.

9. The RF transmitter of claim 1, wherein each switch is configured for bypassing an associated amplifier stage.

10. The RF transmitter of claim 1, wherein the supply modulator is configured to control and output range of each of the amplifier stages that is not bypassed.

11. The RF transmitter of claim 1, wherein the plurality of amplifiers is cascaded, and the supply modulator is configured to modulate, responsive to the envelope output of the signal processing block, the output range of no more than one of the amplifier stages of the power amplifier circuit.

12. The RF transmitter of claim 1, wherein the FM modulator comprises:

a delta-sigma D/A converter;

a synthesizer having a N,N+1 divider; and

a voltage controlled oscillator for generating a phase modulated carrier centered at a selected carrier frequency.

13. The RF transmitter of claim 1, wherein the signal processing block converts the input signal having rectangular coordinates into an output signal having polar coordinates.

14. The RF transmitter of claim 1, wherein the FM modulator is configured to frequency modulate the phase signal onto an RF carrier frequency.

15. The RF transmitter of claim 1, wherein the RF transmitter forms a portion of a handset for wireless communications.