Abstract: The method of calibration of a second order intermodulation intercept point (IIP2) of a radio transceiver comprises the steps of: generating a second order intermodulation (IM2) reference signal (STXIM2-REF) from a transmission baseband signal (STXBB-REF); estimating a second order intermodulation power from the second order intermodulation reference signal (STXIM2-REF) and a radio transceiver output signal (Output); tuning a second order intermodulation intercept point tuner to find a lowest second order intermodulation power; extracting an optimum second order intermodulation intercept point corresponding to the lowest second order intermodulation power.

Abstract: Method of processing a digital complex modulated signal, comprising performing pre-processing said digital complex modulated signal (DCMS) for obtaining a pre-processed digital complex modulated signal (PPRS) and performing a Cartesian to polar conversion of said pre-processed signal, said pre-processing including analysing the trajectory of said digital complex modulated signal and if said trajectory crosses a region (RAO) around the origin (O) of the complex plane, modifying said digital complex modulated signal such that said pre-processed signal has a modified trajectory avoiding said region.

Abstract: The method of calibration of a second order intermodulation intercept point (IIP2) of a radio transceiver comprises the steps of: generating a second order intermodulation (IM2) reference signal (STXIM2-REF) from a transmission baseband signal (STXBB-REF); estimating a second order intermodulation power from the second order intermodulation reference signal (STXIM2-REF) and a radio transceiver output signal (Output); tuning a second order intermodulation intercept point tuner to find a lowest second order intermodulation power; extracting an optimum second order intermodulation intercept point corresponding to the lowest second order intermodulation power.

Abstract: An antenna system for a mobile telephone operates by radio channel between the mobile telephone (1) and at least one at a time of a group of satellites (2) revolving in polar orbit or quasi polar orbit around the earth. The antenna system includes a cone-shaped antenna (3) for transmission and reception with at least four equi-angularly spaced apart spiral strands. Radio frequency signal is fed to or from the strands at the apex or small diameter end of the cone with relative phases to selectively produce for circularly polarized radiation, in a first mode of operation (m1), an antenna pattern of substantially hemispherical form, and in a second mode of operation (m2), an antenna pattern of substantially toriodal form. A switch mode function (SWF) block (11) is controlled by a control block (16) to automatically effect selection of the mode of operation in accordance with a priori or a posteriori selection criteria.