Temperature independent, low level, AM modem receiver

Details Temperature independent, low level, AM modem receiver Temperature independent, low level, AM modem receiver

1986-11-17

1988-04-26

Safourek, Benedick V.

Pulse or digital communications

Repeaters

Testing

375 98, 455246, 455247, 455253, H04B 116

Patent

active

047409967

ABSTRACT:
The receiver of a radio frequency modem (10) achieves temperature and component independence in two steps. The receiver accomplishes detection in unbalanced parallel paths (Q45, Q47; Q44, Q46) such that the diode drops of transistor base-to-emitter junctions in each path offsets those in the other path whereby temperature dependence of components does not adversely affect the operation of the receiver. Any residual base-to-emitter junction offset causes floating of the quiescent bias of the circuits. The floating is further removed by using the same ladder network (R119, R120, R121, R122, R136) to derive all references (60, 61, 62, 63), automatic gain control (63) as well as slicing levels (60, 61, 62). This minimizes the number of circuit components as compared, for example, to using balanced amplifiers. Detectors (Q45, R105, C89, Q47, R108; Q44, R106, C86, Q46, R107, C87) employed in the two unbalanced paths utilize two stages of detection rather than a single stage of detection so as to minimize distortion. Distortion is further minimized when the transistors of corresponding amplifiers in the two unbalanced paths are on the same substrate.

REFERENCES:
patent: 3409834 (1968-11-01), Cullis et al.
patent: 3733553 (1973-05-01), Magnante et al.
patent: 4037163 (1977-07-01), Nicholas
patent: 4165493 (1979-08-01), Harrington

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