Amplifiers – Modulator-demodulator-type amplifier
Patent
1997-07-25
1999-03-23
Pascal, Robert
Amplifiers
Modulator-demodulator-type amplifier
330136, 330149, H03F 338
Patent
active
058865721
ABSTRACT:
A method and apparatus for efficient power amplification with low distortion includes an envelope detector (220), a difference amplifier (130), an envelope amplifier (270), and a power amplifier (260). A feedback path is provided from the output through a second envelope detector (120) to the difference amplifier (130). The feedback circuit operates on the bandwidth of the envelope of the RF signal rather than at the RF bandwidth. An envelope amplifier (270) includes a difference amplifier (272), a pulsewidth modulator (275), a driver (280), switching transistors (285), a low pass filter (290), and a voltage scaler (292). A feedback path within the envelope amplifier reduces the time delay introduced by low pass filter (290). The combined feedback loops work together to reduce distortion and lower intermodulation products.
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Publication entitled, "A High Efficiency 835 MHZ Linear Power Amplifier For Digital Cellular Telephony", M.J. Koch et al. Published by Gateway to New Concepts in Vehicular Technology, San Francisco May 1-3, 1989.
An article entitled "Single-Sideband Transmission By Envelope Elimination And Restoration" by Leonard R. Kahn from Proceeding of the I.R.E., 1952.
Jackson Robert Michael
Myers Ronald Gene
Sigmon Bernard Eugene
LeMoine Dana
Motorola Inc.
Nguyen Khanh Van
Pascal Robert
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