Abstract: A removable plug-in board for dividing incoming radio frequency (RF) to an external port and providing alternating current (AC) signals to a CATV system amplifier contains a radio frequency choke or inductor for passing the AC power signal, a high pass filter for passing the radio frequency signal and either a directional coupler or a splitter. This plug-in board is inserted into a motherboard on which is mounted amplification circuitry and power supply and divider circuitry. The plug-in board routes RF signals arriving on an input port of the amplifier motherboard through the directional coupler to the amplification circuitry, while additionally tapping off and feeding the incoming RF signals to a second output port of the amplifier motherboard.

Abstract: An amplifier (100) for amplifying signals includes a diplex filter (120) having a highpass filter (110) and a lowpass filter (115), and an amplifier circuit (205) for amplifying higher frequency signals provided by the highpass filter (110) of the diplex filter (120). Because the highpass filter (110) introduces attenuation of the higher frequency signals within a particular frequency range, the amplifier (100) also includes a gain control circuit (155) coupled to the amplifier circuit (205) for adjusting the gain of the particular frequency range. Both the diplex filter (120) and the gain control circuit (155) can reside in a plug-in module that can be inserted into and removed from the amplifier (100).

Abstract: A node (100) for a communications system includes a forward distribution amplifier within a housing (600). Plug-in modules (200,400) can be removably attached to the forward distribution amplifier within the same housing (600) to change the functionality of the node (100). For example, the plug-in module can be a reverse amplifier module (200) for adding reverse signal processing function or an optical module (400) for adding optical capabilities.

Abstract: The present invention solves the gain, noise figure, and distortion problems of prior art thermal compensation circuits by incorporating a temperature-compensating circuit in the feedback loop of a transistor amplifier arrangement. Using this method, the insertion loss is reduced as the gain of the amplifier varies proportionately to the temperature. This method has a negligible effect on the noise figure and distortion, and the incremental cost is much lower than the conventional circuits. Furthermore, the present invention can be used in both single-ended or push-pull dual amplifier configurations.

Abstract: The automatic gain control circuit of the present invention improves upon conventional techniques using a pilot carrier for control by monitoring for the presence of the pilot carrier. If the pilot carrier level is at an undetectable level, it will switch control of the level control section of the automatic gain control circuit to the equivalent thermal setting by means of a switch. The switch connects the output of a temperature-sensing network to a Bode driving circuit that approximates attenuation of a given transmission medium over temperature. The gain setting will therefore be based on an approximation of what the cable losses should be at the detected temperature of the amplifier housing. The present invention provides dynamic gain adjustment, even in the event of pilot carrier signal loss.