Scientific-atlanta, Inc.

Other

Walid Kamali

Herman A Kruse

John Skrobko

Saleh R Al-Araji

Brian Green

Disclosed herein are circuits and methods for reducing a thermally dependent gain swing. Exemplary embodiments include a resonant notch filter in parallel with a thermistor.

Circuits and methods of thermal gain compensation

The present invention is directed towards an optical receiver including an open loop automatic gain control (AGC) circuit. Optical signals received by the optical receiver are converted to electrical signals via a photodiode. The electrical signals are subsequently amplified through an input and an output amplifier stage. The amplified signal is then converted to RF signals and provided to an output port for further transmission. Concurrently, the AGC circuit senses the input optical power level at the input photodiode. The input optical power level is compared with a reference voltage, thereby providing a difference voltage. The difference voltage is applied to input and output amplifier stages for correcting the electrical signals to ensure a constant output power level.

Optical receiver having an open loop automatic gain control circuit

An amplifier circuit (400) includes an input port (402) for receiving a signal and a first balun (404) for splitting the signal into first and second signals. First and second amplifiers (406, 408) are coupled to outputs of the first balun (404) for respectively amplifying the outputs of the first balun (404) to generate first and second amplified signals. Second and third baluns (410, 412) are coupled, respectively, to outputs of the first and second amplifiers (406, 408) for splitting, respectively, each of the first and second amplified signals into in-phase and out-of-phase components. The amplifier circuit (400) also includes third and fourth amplifiers (414, 416) coupled to outputs of the second balun (410) for respectively amplifying the outputs of the second balun (410) to generate third and fourth amplified signals and fifth and sixth amplifiers (418, 420) coupled to outputs of the third balun (412) for respectively amplifying the outputs of the third balun (412) to generate fifth and sixth amplified signals. A fourth balun (422) combines the third and fourth amplified signals into a first combined signal, and a fifth balun (424) combines the fifth and sixth amplified signals into a second combined signal. The amplifier circuit (400) further includes a combiner, such as an additional balun (326) or a summer (430), for combining the first and second combined signals to generate an amplifier output signal.

Amplifier circuit

A protection circuit prevents a surge applied to one end of a signal line from being applied to a circuit connected to another end of the signal line. The protection circuit includes a first diode having an anode coupled to the signal line and a first capacitor having a first electrode coupled to a cathode of the first diode and a second electrode coupled to a first potential. A second capacitor has a first electrode coupled to the signal line and a second diode has a cathode coupled to a second electrode of said second capacitor and an anode coupled to the first potential. A first inductor is coupled between the cathode of the first diode and the cathode of the second diode. A power supply terminal is applied with a power supply potential and is coupled to one end of the first inductor.

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Duluth, GA, United States of America

Walid Kamali