Radio-signal direction finding

A method of radio-signal direction finding comprising:

• switching at least two antennas from one antenna coupled to a radio-signal input, to another antenna coupled to the radio-signal input, the antennas being at different locations;
• processing a radio signal which is present at the radio-signal input so as to obtain a phase-detection input signal;
• detecting periods of time in which the phase-detection input signal is substantially free of phase-modulation;
• enabling a switchable antenna coupler to switch said at least two antennas during said periods of time;
• and
• detecting a phase-change in the phase-detection input signal during said periods of time due to the switching from the one antenna to the other antenna;
• and
• calculating the direction in which the source of the radio signal is located on the basis of the phase change.

A radio-signal direction finder for establishing in which direction a radio-signal source is located, the radio-signal direction finder comprising:

• a plurality of antennas at different locations;
• a switchable antenna-coupler for switching from one antenna coupled to a radio-signal input, to another antenna coupled to the radio-signal input;
• a radio-signal processor for processing a radio signal which is present at the radio-signal input so as to obtain a phase-detection input signal;
• a controller which detects periods of time in which the phase-detection input signal is substantially free of phase-modulation, and enables the switchable antenna coupler to switch said plurality of antennas during said periods of time;
• a phase-change detector for detecting a phase-change in the phase-detection input signal during said periods of time due to the switching from the one antenna to the other antenna;
• and
• a calculator for calculating the direction in which the source of the radio-signal is located on the basis of the phase change.

A method of radio-communication comprising the steps of:

• switching from one antenna coupled to a radio-signal input, to another antenna coupled to the radio-signal input, the antennas being at different locations;
• processing a radio signal at the radio-signal input so as to obtain a phase-detection input signal;
• detecting periods of time in which the phase-detection input signal s substantially free of phase-modulation;
• enabling a switchable antenna coupler to switch the antennas during said periods of time;
• detecting a phase-change in the phase-detection input signal during said periods of time due to the switching from the one antenna to the other antenna;
• calculating the direction in which the source of the radio signal is located on the basis of the phase change;
• and
• controlling, on the basis of the calculated direction, an antenna array such that the antenna array provides an antenna pattern which is substantially directed to the source.