Circuit for 2-level/4-level frequency shift key modulation

Details Circuit for 2-level/4-level frequency shift key modulation Circuit for 2-level/4-level frequency shift key modulation

1996-12-26

1998-05-26

Mis, David

Modulators

Frequency shift keying modulator or minimum shift keying...

375303, H03C 300, H03K 706, H04L 2712

Patent

active

057572453

ABSTRACT:
A circuit for two-level/four-level frequency shift keying modulation, which may be used for a paging transmitter, is compatible with earlier two-level non-return to zero frequency shift keying modulation circuits and includes; a voltage leveling circuit for generating four voltage levels to selectively allow the two-level and four-level frequency shift keying modulation; a decoder for decoding the least significant bit and most significant bit data inputs to generate a decoded signal output; an analog switch for selecting the four voltage levels in accordance with the two-level or four-level frequency shift keying modulation, in response to the decoded signal; an adder for adding the selected voltage level to a reference voltage to generate a corresponding digital output voltage; an audio amplifier for amplifying an audio signal input; an input/filter selector for selecting the digital output voltage or the amplified audio signal in response to an input selection control signal and for selecting one of two filtering paths of a following stage in association with a control signal for selecting the two-level or four-level frequency shift keying modulation to generate the selected digital output voltage or the amplified audio signal via the selected filtering path; and a baseband filter for performing a first or a second filtering with a respective bandwidth for the two-level or four-level frequency shift keying modulation and for filtering the digital output voltage or the audio signal supplied through the selected one of the filtering paths.

REFERENCES:
patent: 4368439 (1983-01-01), Shibuya et al.
patent: 4408135 (1983-10-01), Yuyama et al.
patent: 4481642 (1984-11-01), Hanson
patent: 5329258 (1994-07-01), Matsuura
patent: 5377229 (1994-12-01), Wilson et al.
patent: 5450023 (1995-09-01), Yang et al.

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