Patent ID: 7349717
Filing Date: 2008-03-25
Classification: H04B

Abstract:
1. A front-end circuit comprising: a first signal path comprising a second signal path comprising a switch having an output connected to inputs of the first and second signal paths; an input circuit to provide signals to the switch, the input circuit comprising an antenna connector; and a diode circuit to enhance isolation of the first and second signal paths, the diode circuit being arranged in the shared output path, the diode circuit for rejecting signals in at least one rejection band, the diode circuit comprising diodes connected in shunt or in series; wherein outputs of the first and second signal paths are connected in an impedance-neutral manner to form a shared output signal path; wherein (i) the first filter has a high output impedance in a pass band of the second filter or the second filter has a high output impedance in a pass band of the first filter, or (ii) the front-end circuit further comprises impedance-matching circuitry on an output side of the front-end circuit, the impedance-matching circuitry for matching output impedances of the first and second signal paths; and wherein the front-end circuit is usable with a multi-band transmission system or multi-band/multi-mode transmission system.