Calibration apparatus and method

A method of calibrating a multi-beam satellite system having a beam forming network providing a plurality of signal paths, the method comprising

• extracting calibration tones from a test path of the plurality of paths;
• and
• determining the phase and amplitude shifts of the test path for the calibration tones by correlating the extracted calibration tones with reference calibration signals, wherein the calibration tones comprise at least two calibration tones of different frequencies to allow a phase and amplitude offset of the test path for a signal of any frequency within an operational frequency range of the multi-beam satellite system to be calculated from the determined phase and amplitude shifts.

A computer program for calibrating a multi-beam satellite system having a beam forming network providing a plurality of signal paths, the computer program comprising instructions that when executed by a processor cause the processor to

• extract calibration tones from a test path of the plurality of paths;
• and
• determine the phase and amplitude shifts of the test path for the calibration tones by correlating the extracted calibration tones with reference calibration signals, wherein the calibration tones comprise at least two calibration tones of different frequencies to allow a phase and amplitude offset of the test path for a signal of any frequency within an operational frequency range of the multi-beam satellite system to be calculated from the determined phase and amplitude shifts.

Apparatus for calibrating a multi-beam satellite system comprising a beam forming network providing a plurality of signal paths, the apparatus comprising

• a digital signal processor for translating a signal in a test path of said plurality of paths from a first frequency to a second frequency, the signal comprising a calibration tone;
• a calibration processor for determining the phase and amplitude shift of the test path by correlating a calibration tone extracted from the test path with a reference calibration signal, the calibration processor being configured to determine the phase and amplitude shift of the test path for at least two calibration tones of different frequencies and the digitals signal processor being configured to apply a correction, based on the determined phase and amplitude shifts for the at least two calibration tones, to the test path.