Aiming at higher performances and lower cost of an ultrasonic imaging system, a novel digital imaging approach was proposed, which combines the dual beamforming technique to double frame rate with the synthetical aperture technique to halve receive channels. Besides theoretical analyses and simulations, its hardware implementation was discussed in detail, embodied and finally tested on a real ultrasonic imaging system. The experimental results show that with this approach, system cost can be remarkably reduced without lowering the frame rate and image quality.