Method and apparatus for high efficiency wideband power amplification

• US 6,130,910 A
• Filed: 11/03/1997
• Issued: 10/10/2000
• Est. Priority Date: 11/03/1997
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Anderson, Dale, Midya, Pallab, Myers, Ronald Gene
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): DEPPE, BETSY LEE
• Application Number:
  US08/963,491
• Time in Patent Office: 1,072 Days
• Field of Search: 375/238, 375/295, 375/297, 375/377, 332/109, 455/91, 455/102, 455/127, 330/10, 330/110, 330/297, 330/127, 330/199
• US Class Current: 375/238
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

A method and apparatus for efficient power amplification of a wideband signal with a correspondingly wide modulation bandwidth includes an envelope detector (220), an interleaved class S modulator (270), and a power amplifier (260). The interleaved class S modulator (270) amplifies includes multiple channels (272) which each include a portion of a class S modulator. Each class S modulator has a duty cycle and time offset associated therewith. The duty cycles of the channels (272) can be the same with the time offsets different, or the duty cycles can also be different. For an interleaved class S modulator with N channels (272), the slew rate increases by as much as N, and the output ripple decreases by as much as N².

Claims

1. A method of amplifying an input signal, said method comprising:

splitting said input signal into an envelope component and a phase component;

generating an envelope signal representing amplitude information of said envelope component;

creating a plurality of pulsewidth modulated signals in response to said envelope signal;

combining said plurality of pulsewidth modulated signals to produce an amplified envelope signal; and

receiving said phase component as an input to an amplifier stage and said amplified envelope signal as a power supply to said amplifier stage such that said phase component is remodulated and amplitude of said input signal is restored to reproduce a substantial replica of said input signal.

2. The method of claim 1 wherein creating a plurality of pulsewidth modulated signals comprises:

creating a first pulsewidth modulated signal having a first duty cycle; and

creating a second pulsewidth modulated signal having a second duty cycle.

3. The method of claim 2 wherein said first duty cycle is proportional to a more significant portion of said input signal and said second duty cycle is proportional to a less significant portion of said input signal.

4. The method of claim 1 wherein creating a plurality of pulsewidth modulated signals comprises:

creating a first pulsewidth modulated signal having a first time offset; and

creating a second pulsewidth modulated signal having a second time offset.

5. The method of claim 4 wherein said first time offset and said second time offset are not equal.

6. An amplifier comprising:

a divider configured to split an input signal into an amplitude path signal and a phase path signal;

an detector configured to detect an envelope of said amplitude path signal and generate an envelope signal representing amplitude information;

a modulator configured to receive said envelope signal and produce an amplified envelope signal, said modulator comprising;

a plurality of pulsewidth modulators configured to receive said envelope signal, each of said plurality of pulsewidth modulators configured to produce a pulsewidth modulated signal having a duty cycle substantially related to an amplitude of said envelope signal;

a combining network configured to combine each pulsewidth modulated signal of said plurality of pulsewidth modulators to produce a composite signal; and

a filter configured to filter said composite signal and produce said amplified envelope signal;

a delay element configured to delay said phase path signal in order to compensate for a delay of said amplitude path signal to produce a time delayed signal; and

a power amplifier configured to receive said amplified envelope signal as a power supply such that said time delayed signal is remodulated and said envelope of said amplitude path signal is restored to reproduce a substantial replica of said input signal.

7. The amplifier of claim 6 wherein said plurality of pulsewidth modulators is comprised of:

a first pulsewidth modulator having a first duty cycle and a first time offset; and

a second pulsewidth modulator having a second duty cycle and a second time offset.

8. The amplifier of claim 7 wherein said first duty cycle is proportional to a more significant portion of an input signal, and said second duty cycle is proportional to a less significant portion of said input signal.

9. The amplifier of claim 7, wherein said first time offset and said second time offset are not equal.