Nokia Mobile Phones Limited

Technophone Limited

Peter Sroka

Peter D Harrison

John A Samuels

In a mobile radio telephone, an adaptive impedance matching circuit (25) is positioned between a transmitting power amplifier (24) and a duplexer (18). The adaptive matching circuit (25) matches an antenna (17) to associated electronic circuitry, thereby optimising power transfer in an effort to maintain communication with a base station and to minimise power dissipation within the device itself. An adaptation algorithm is selected and implemented during idle periods when a reflection coefficient is identified as being large. The reactance of a passive pi network is incrementally modified and settings which achieve an optimum match are stored for subsequent use.

Adaptive antenna matching

Apparatus and a method for inhibiting spurious responses in the receiver stage of a radio telephone are disclosed. A detector detects the transmission of an RF signal from the transceiver and sends a control signal indicative of such transmission to a linearity controller. The linearity controller is coupled to non-linear devices in the receiver stage of a transceiver and varies the linearity of the non-linear devices in accordance with the control signal. Preferably, the linearity is varied by increasing the bias current or voltage for the non-linear devices when the control signal indicates transmission of an RF signal.

Method and apparatus for suppressing spurious third-order responses in

An antenna assembly comprises an elongate radiating element (11) movable between a retracted position and an extended position, and a substantially planar radiating element (12) extending transversely to the elongate element. The elongate element extends through an aperture (25) in the planar element. A pair of concentric conductors (9,10) provide coaxial feed to the radiating elements and the elongate element is slidably mounted within the inner conductor (9). In the retracted position the elongate element forms part of the coaxial feed to the planar element and is itself rendered inoperative as a radiator. The invention provides a compact and convenient dual antenna arrangement ideally suited for use in a portable cellular radio telephone.

Retractable antenna assembly with retraction inactivation

A tunable bandstop/bandpass filter particularly suitable for use in duplex applications where the transmit and receive bands are closely located, comprises two or more reactively coupled quarter wavelength resonators e.g. dielectric resonators. One end of each resonator is coupled to ground potential. The opposite (open-circuit) end of the resonators is coupled to adjacent resonators via coupling capacitors. Voltage controlled tuning means, e.g. a varactor and series connected capacitor, are coupled in parallel to the open circuit end of each of the resonators respectively. The stopband/passband of the filter can thus be adjusted by varying the voltage applied to the tuning means. Additionally, in the case of a bandpass filter a tunable zero (or 'notch') may be introduced into the transmission response by including varactors coupled in series to the open-circuit end of the resonators.

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Sandhurst, United Kingdom

Peter Sroka