Digital beamforming apparatus with a sigma-delta A/D converter

Embodiments of the present invention may provide a digital beamforming apparatus in an ultrasound system having an array transducer, the apparatus comprising: a variable sampling clock generating unit to variably generate sampling clock signals based on reception delay times in ultrasound echo signals arriving at each element of the transducer elements of the array transducer, the variable sampling clock generating unit further being configured to output control signals corresponding to cycles of the sampling clock signals; sigma-delta analog-to-digital (A/D) converters connected to the respective transducer elements of the array transducer and being configured to convert analog signals outputted from the elements of the array transducer into digital signals in response to the sampling clock signals and the control signals; delay units to delay output signals of the sigma-delta A/D converters based on the reception delay time; and an adder for adding the delayed signals.