Abstract: A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit (2) controlled by a gain control signal and a reverse path unit (6) comprising a filter unit (8) with variable time constant. A control unit (13) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances (12) and capacitances (10) in such a way that the time constant of the filter unit (8) varies essentially proportionally with the gain of the variable amplifier unit (2). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain.

Abstract: A GPS-cellular hand-set includes a receive antenna; a separate transmit antenna; a power amplifier; a duplex filter unit having an input connected to the receive antenna, a cellular output, and a GPS output; a cellular unit having a receive input and a transmit output, wherein the receive input is connected to the cellular output of the duplex filter unit and the transmit output is connected to the transmit antenna via the power amplifer; and a GPS unit having an input connected to the GPS output of the duplex filter unit.

Abstract: The present invention is a circuit, method and system for automatic gain control in a communication device which may receive one or more communication signals. The source or sources of the one or more communication signals may be selected from a set of one or more related or unrelated transmitters of networks of transmitters. Each transmitter or network of transmitters may produce one or more signal types. As part of the present invention, a circuit or system may control a gain correction factor of variable gain amplifiers used to amplify a received signal according to a set of parameters associated with one or more selected signal types.

Abstract: An active duplex filter unit (7) for a combined GPS-cellular hand-set comprises a GPS low noise amplifier unit (13) connecting a receive antenna to the input of a GPS unit. It comprises a capacitance (15) and an inductance (16) preceding, in parallel, an amplifier (14) whose output is connected to ground via, in series, an inductance (17) and a capacitance (18) with a tap (19) for the application of a bias voltage (+V) between them. A similar cellular low noise amplifier unit (12) connects the receive antenna with the recive input of a cellular unit a transmit output of which is connected to a transmit antenna via a power amplifier. The GPS low noise amplifier unit (13) provides high gain and low noise figure at the GPS frequency and strong suppression in particular of frequencies used by cellular systems. The transmitter leakage signal in the GPS and cellular receivers is attenuated by the separation of the receive and transmit antennas.

Abstract: A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit (2) controlled by a gain control signal and a reverse path unit (6) comprising a filter unit (8) with variable time constant. A control unit (13) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances (12) and capacitances (10) in such a way that the time constant of the filter unit (8) varies essentially proportionally with the gain of the variable amplifier unit (2). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain.