Modulators – Amplitude modulator
Patent
1995-12-26
1996-11-26
Mis, David
Modulators
Amplitude modulator
330 10, 455108, H03C 100, H03F 324
Patent
active
055789714
ABSTRACT:
An amplitude modulation circuit and method. A predetermined number of (e.g., 6) drivers and differentially switched power amplifiers are provided in pairs. A program sound signal which has been quantized into a predetermined number of bits (e.g., 12 bits) is divided through a ROM into a plurality of bit groups each consisting of a predetermined number of bits (e.g., 2 bits), which are in turn distributed to the respective driver and differentially switched power amplifier pairs. In response to the value of the distributed bit group, each driver selects two different phase-shift carriers from seven different phase-shift carriers, and provides as its outputs .phi..sub.A and .phi..sub.B. With the output phase-shift carriers (.phi..sub.A and .phi..sub.B), each driver differentially switches the differentially switched power amplifier corresponding thereto. The output of each differentially switched power amplifier is weighted. The outputs of all the differentially switched power amplifiers are combined by a power combiner and then filtered through a BPF, thereby obtaining a broadcast output which has been amplitude modulated by the program sound. Thus, a digital amplitude modulation can be realized using a lower number of power amplifiers than before.
REFERENCES:
patent: 3480881 (1969-11-01), Boykin
patent: 4403197 (1983-09-01), Swanson
patent: 5111158 (1992-05-01), Malec et al.
patent: 5132637 (1992-07-01), Swanson
patent: 5450444 (1995-09-01), Miki et al.
"Digitally Implemented Medium Frequency Transmitter And Its Application", Shinya Hirano, Hoso Gijutsu, pp. 119-125 (Apr. 1991 Issue).
Hayeiwa Kazuhisa
Kojima Yutaka
Minami Michitoshi
Naka Hisashi
Japan Radio Co. Ltd.
Mis David
Nippon Hoso Kyokai
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