Abstract: Systems and methods for a distortion monitoring system that detects an abnormal amount of signal distortion occurring in a transmission system. The distortion monitoring system includes a system amplifier section for amplifying and coupling an input signal to provide first and second outputs and a distortion monitoring section for processing the second output. The amount of distortion present is represented by an output from the distortion monitoring section of the system. In one embodiment, the distortion monitoring section can include an envelope detector for receiving the second output signal, a lowpass filter coupled to the envelope detector for cutting off frequencies below the Nyquist rate, and a voltage amplifier coupled to the lowpass filter for amplifying the signal.

Abstract: A communication system (300) includes amplifiers (325) having an improved thermal response. The amplifiers (325) include a Bode circuit (208) for attenuating the signals and a thermal compensation circuit (320) for adjusting the gain in response to changes in temperature. The thermal compensation unit (320) provides a non-linear impedance to offset for the non-linear performance of the amplifiers gain versus control current. The thermal compensation unit (320) has circuit paths that are selectively turned on to provide the non-linear relationship of impedance versus input control voltage.

Abstract: An amplifier (125) having automatic gain control (AGC) includes a gain stage (220), having a variable amplifier (215), for amplifying a signal received by the amplifier (125). The amplifier (125) also includes an AGC circuit (228) that adjusts amplification of the gain stage (220) and that includes a manual switch (246) having first and second switch settings. Sequential operation from the first switch setting to the second switch setting causes the AGC circuit (228) to automatically and correctly set the gain of the amplifier (125) without further human intervention.

Abstract: A distribution amplifier (210) for a cable television system (100) includes an output gain stage section (215) for receiving an input signal from a cable head end section (105). The output gain stage section (215) includes multiple active amplifier circuits (225, 230) for amplifying the input signal to generate main and auxiliary outputs that are processed by a radio frequency (RF) detector (255) having at least a first detector circuit (300) for processing the main output to generate a first voltage and a second detector circuit (305) for processing the auxiliary output to generate a second voltage. Further included in the distribution amplifier (210) is a status monitor (260) coupled to the RF detector (255) for converting the first and second outputs to first and second digital values and transmitting the first and second digital values. In this manner, an indication of a system or amplifier malfunction can be provided.

Abstract: 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.

Abstract: A cable television system employs two-way communication between a headend and at least one subscriber terminal. The two-way communication is provided by having separate frequency bands for each communication path. The frequency bands do not overlap and the higher frequency band is used for subscriber terminal to headend transmissions. A line amplifier is provided that employs two diplex filters each connected to both a forward and reverse amplifier. The high pass portions of the diplex filters are formed from both lumped and distributed components.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. A gain control circuit controls the gain of the amplifier pair.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.

Abstract: A transimpedance receiver for broad band optical signals, such as carry multichannel CATV signals or broad band data over an optical fiber which may vary in length (e.g. from 2 km to 20 km) such that the optical power at a photodetector of the receiver may vary widely depending upon where the receiver, and is installed in the fiber optic distribution system utilizes a broad band device, preferably a GASFET, the internal capacitance and gain of which enables amplification over the broad band frequency range without oscillation.

Abstract: Scrambling and descrambling systems utilizing jamming signals provide improved pictures with minimal distortion due to ghosts and artifacts. The television signal is combined with a jamming signal or signals located preferably in the vestigial sideband (VSB) of the modulated picture carrier and at about a null in the spectrum of the modulation of the picture carrier by the horizontal sync. The jamming signal or signals also preferably are placed between the harmonic components of the horizontal sync which define the horizontal sync spectrum and at frequencies which comply with governmental regulations respecting frequency locations of strong signals of CATV purposes. The jamming signals are generated by phase locking to the horizontal sync signals of the television signals or to a submultiple of the horizontal sync frequency.