Design and implementation of an active antenna array for TD-LTE system based on DDS phase shifter

In this paper, a novel active antenna array is proposed for TD-LTE base station system. This array includes two parallel eight-element uniform linear sub-arrays for the dual polarization operation and provides a usable bandwidth of 100 MHz. Beamforming in the vertical dimension is achieved which improves the performance of cellular mobile communication systems. Each radiation antenna element is integrated with a complete transceiver to reduce the cable loss. Each transmitter is capable of generating up to 21 dBm of output power. Each receiver signal path achieves a gain of 37 dB and a noise figure below 3.5 dB. The eight-path sub-array improves the signal-to-noise ratio at the output by 9 dB in receiving mode compared with a conventional single receiver. Direct digital synthesizer (DDS) chips generate the local oscillator (LO) signal and work as active phase shifters in each path. This active phase shifting infrastructure provides a 360° phase shifting range and accurate tuning step which leads to a beam-steering resolution of 0.1°.