Digital modulator with compensation and method therefor

Details Digital modulator with compensation and method therefor Digital modulator with compensation and method therefor

1996-08-08

1999-07-27

Vo, Don N.

Pulse or digital communications

Systems using alternating or pulsating current

Amplitude modulation

375281, 375308, 332103, H04L 2720

Patent

active

059302992

ABSTRACT:
In a digital modulator with compensation, a digital bit stream from a microphone (705), a speech coder (706), and a channel encoder (707) is sent to an encoder (720) which translates the bits into I/Q digital pulses with phase shift keying. A symbol correlater (730) notes when predetermined target phase symbol sequences, which contribute to a high peak-to-average power ratio, enter the encoder. If a target symbol sequence is encountered, the correlater directs compensation amplifiers or compensation filters (734, 737) of the I/Q signals. Next, I/Q pulse shaping filters (764, 765) filter the I/Q pulses according to communication system specifications. The filtered I/Q signals are then sent to a quadrature modulator (790) for RF modulation. Compensation of target symbol sequences reduces the negative impact they have on peak-to-average power ratio and increases the efficiency of the power amplifier (795) which extends the battery life of a communication device (700).

REFERENCES:
patent: 5157693 (1992-10-01), Lemersal, Jr. et al.
patent: 5590155 (1996-12-01), Yasuda
patent: 5640417 (1997-06-01), Barabash et al.
"An Integrated .pi./4-Shift QPSK Baseband Modulator," by Yasushi Kobayashi, Takaoki Hida, Kazushige Sawada, Kiyoaki Hodohara, Yukihiro Ueda, Kaoru Takasuka, Allen Barlow*, Asahi Kasei Microsystems, Tokyo, Japan, *San Diego, CA, IEEE 1994 Custom Integrated Circuits Conference, IEEE, 1994.

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