Abstract: An amplifier for a radio communications system in a shielded tunnel is disclosed. In one example, the amplifier comprises a processor configured to execute a plurality of modules comprising a gain control module and an attenuation control module. Methods and systems are further provided for controlling and monitoring amplifier characteristics.

Abstract: An amplifier for a radio communications system in a shielded tunnel is disclosed. In one example, the amplifier comprises a processor configured to execute a plurality of modules comprising a gain control module and an attenuation control module. Methods and systems are further provided for controlling and monitoring amplifier characteristics.

Abstract: An amplifier for a radio communications system in a shielded tunnel is disclosed. In one example, the amplifier comprises a processor configured to execute a plurality of modules comprising a gain control module and an attenuation control module. Methods and systems are further provided for controlling and monitoring amplifier characteristics.

Abstract: An amplifier for a radio communications system in a shielded tunnel is disclosed. In one example, the amplifier comprises a processor configured to execute a plurality of modules comprising a gain control module and an attenuation control module. Methods and systems are further provided for controlling and monitoring amplifier characteristics.

Abstract: The dual band bi-directional amplifier has only one amplifier chain having an uplink amplifier and a downlink amplifier, but can nonetheless amplify signals from two frequency bands in both an uplink and a downlink direction between two antennas. This is possible by using duplexers and circulators to separate signals to and from each antenna into the two bands. In particular, for each frequency band handled by the circuit, the dual band bi-directional amplifier has a duplexer set for separating the signals from one of the bands into the uplink and downlink direction. In the case of a dual band amplifier, there are two sets of duplexers, one for each band. By using duplexers and circulators to differentiate signals in different bands travelling in different directions, there is no need for additional amplifier chains, which increase the manufacturing costs.

Abstract: The dual band bi-directional amplifier has only one amplifier chain having an uplink amplifier and a downlink amplifier, but can nonetheless amplify signals from two frequency bands in both an uplink and a downlink direction between two antennas. This is possible by using duplexers and circulators to separate signals to and from each antenna into the two bands. In particular, for each frequency band handled by the circuit, the dual band bi-directional amplifier has a duplexer set for separating the signals from one of the bands into the uplink and downlink direction. In the case of a dual band amplifier, there are two sets of duplexers, one for each band. By using duplexers and circulators to differentiate signals in different bands travelling in different directions, there is no need for additional amplifier chains, which increase the manufacturing costs.

Abstract: In a feed forward amplifier (100), a main amplifier (125) is coupled between an input (102) at which an input signal is received and an output (173) at which an output signal is provided. The output signal is an amplification of the input signal. A sample of the output signal is compared (144) with a sample of the input signal to produce a difference signal indicative of distortions introduced by the main amplifier (125). An error amplifier (165) provides a distortion signal which is an amplification of the difference signal, and the distortion signal is combined (169) with the output signal to compensate for main amplifier distortions. A random frequency, constant amplitude sine wave pilot signal is combined (117) with the input signal, and a correlation power detector (194,195,202,212,213) is provided to determine the magnitude of the pilot signal in the output signal. The gain and phase of the difference signal is then adjusted (155) to minimize the magnitude of the pilot signal in the output signal.