Polar modulator

Abstract

A polar modulator () comprises a modulation generator () arranged to generate phase modulation data and amplitude modulation data; and a phase modulation stage () arranged to generate a phase modulated, PM, carrier signal and a PM clock signal, wherein the PM carrier signal has a PM carrier signal frequency and the PM clock signal has a PM clock signal frequency, and the PM carrier signal frequency is higher than the PM clock signal frequency, the PM carrier signal and the PM clock signal are phase modulated by the phase modulation data, and the phase modulation stage () comprises an adjustable delay stage () arranged to adjust a relative delay between the PM carrier signal and the PM clock signal to a target value. The polar modulator () further comprises a re-timing circuit () arranged to generate an amplitude modulation, AM, clock signal by re-timing the PM clock signal with the PM carrier signal; an amplitude modulation stage () arranged to employ the AM clock signal to clock the amplitude modulation data into the amplitude modulation stage () and arranged to amplitude modulate the PM carrier signal with the amplitude modulation data; an error detection stage () arranged to generate an indication of a magnitude of a first deviation of the AM clock signal from a target condition; and a control stage () arranged to select the target value of the relative delay by determining, by controlling the adjustment of the relative delay by the adjustable delay stage (), a first value of the relative delay that maximizes the magnitude of the first deviation, and applying an offset to the first value of the relative delay.