An analogue to digital converter uses charge sampling in combination with a successive approximation conversion technique in order to combine anti-alias filtering and quadrature downconversion functions into the data converter. The conversion method is an energy-efficient realization for wide-band radio systems with moderate resolution specifications such as 4G or ultra-wideband radio (UWB). The converter uses two capacitor matrices, one to perform charge sampling, and one to be used simultaneously in the successive approximation technique, so that full use of an input signal is made and efficiency is maximised.