A functional block of a front-end circuit for a communication device,
which is employed for multi-band and/or multi-mode operation, is
proposed. By positioning, according to this invention, a pin diode switch
in one of the parallel signal paths instead of positioning it on the
input side before separating the signal paths, it is possible to do
without an impedance transformation network on the input side and to thus
reduce the signal loss and the space requirement of the circuit. In a
further configuration, the signal paths preferably associated with the
adjacent frequency bands are combined on the output side, whereby the
further processing of the signals corresponding to the different
frequency bands takes place in one path. This for example allows a chip
set designed for (n-1) frequency bands to be used in a transmission
system designed for n bands. Another embodiment of this invention enables
monitoring of the received signal of a system even during operation of
the other mode in a multi-mode system. Stable electrical properties of
the circuit can be achieved according to this invention through
integration of all components of the front-end circuit in one module.