A method is disclosed for operating a multi-mode mobile station, wherein
each mode shares at least one common band of frequencies. The method
includes transmitting a signal from a first antenna circuit of the mobile
station in the common band of frequencies and, while transmitting,
electronically detuning a second antenna circuit of the mobile station
such that the second antenna circuit is not resonant in the common band
of frequencies. As an example, the common band of frequencies includes
1900 MHz. The step of detuning includes varying an impedance of at least
one component that forms a part of the second antenna circuit, where the
at least one component can be a stripline or a PIN diode of a FET diode
uses as switch for making an impedance change. The at least one component
can also be a normally active component that is put into a passive state.
A multi-mode mobile station in accordance with these teachings has, for
each mode, a transmitter chain that includes an antenna circuit that
operates in the common band of frequencies and a controller, that is
responsive to a first one of the transmitter circuits transmitting, for
electronically detuning a second antenna circuit of the mobile station
such that said second antenna circuit is resonant at a frequency that
lies outside of, or that is shifted away from, the common band of
frequencies.