Demodulation

A method comprising:

• receiving a radio signal modulated using frequency shift keying or phase shift keying, the radio signal comprising a plurality of symbol intervals;
• multiplying, by differential detector circuitry, a signal for a current symbol interval with a first reference signal and outputting a first output signal for the current symbol interval, wherein the first reference signal corresponds to a conjugate of a signal for a first symbol interval preceding the current symbol interval;
• multiplying, by the differential detector circuitry, the signal for the current symbol interval with a second reference signal and outputting a second output signal for the current symbol interval, wherein the second reference signal corresponds to a conjugate of a signal for a second symbol interval preceding the first symbol interval, in which the signal for the second symbol interval has been phase adjusted in dependence on a previous phase decision for the first symbol interval;
• combining the first output signal and the second output signal to obtain a combined signal for the current symbol interval;
• and
• outputting a phase decision for the current symbol interval in dependence upon the combined signal.

A non-transitory machine-readable storage medium bearing instructions which, when executed by a receiver device, causes the receiver device to perform a method comprising:

• receiving, the radio signal modulated using frequency shift keying or phase shift keying, the radio signal comprising a plurality of symbol intervals;
• multiplying, by differential detector circuitry, a signal for a current symbol interval with a first reference signal and outputting a first output signal for the current symbol interval, wherein the first reference signal corresponds to a conjugate of a signal for a first symbol interval preceding the current symbol interval;
• multiplying, by the differential detector circuitry, the signal for the current symbol interval with a second reference signal and outputting a second output signal for the current symbol interval, wherein the second reference signal corresponds to a conjugate of a signal for a second symbol interval preceding the first symbol interval, in which the signal for the second symbol interval has been phase adjusted in dependence on a previous phase decision for the first symbol interval;
• combining the first output signal and the second output signal to obtain a combined signal for the current symbol interval;
• and
• outputting a phase decision for the current symbol interval in dependence upon the combined signal.