Digitally controlled wide ranch automatic gain control

Details Digitally controlled wide ranch automatic gain control Digitally controlled wide ranch automatic gain control

1980-09-12

1982-11-23

Mullins, James B.

Amplifiers

With semiconductor amplifying device

Including gain control means

330279, 330129, 330144, H03G 320

Patent

active

043607870

ABSTRACT:
In high speed high quality modems it is important to be able to preserve the gain value for the automatic gain control system during breaks in transmission to permit rapid resumption of normal operation. The a.g.c. circuit comprises a basic a.g.c. transistor amplifier whose emitter-collector conductance is varied by a control voltage derived from the envelope of the amplifier output voltage which is well known. The invention involves the use of a digital-to-analog converter which is controlled by a digital-updown counter. The counter is controlled by a window comparator which compares the rectified output voltage of the amplifier with a reference voltage level and upper and lower limits. If the output voltage exceeds either limit, the counter is enabled and the appropriate up or down indication is given. The counter is then clocked to change the drive to the d-to-a converter which thereby changes the conductance of the a.g.c. transistor. The state of the up down counter will be used to maintain the a.g.c. at the last level in the event of a transmission break by inhibiting the clock for the counter.

REFERENCES:
patent: 3636462 (1972-01-01), Baldauf, Jr.
patent: 4066977 (1978-01-01), Chambers et al.
patent: 4112384 (1978-09-01), Buchberger
patent: 4134079 (1979-01-01), Kohtani

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