Phased-array system stems from an idea to build antennas that can operate with signals in various directions without turning the antenna mechanically. Thus the cost, the weight and the dimension of these types of system can be reduced significantly. In this system, the phase of the antennas in an antenna array will be steered electronically to the required direction, hence the so-called phased-array antenna. By using this control manner, electrical signal is sent to each antenna in an array with an appropriate phase in such a way that, when combined spatially, it increases the intensity of the signal in the desired direction, while minimizing the signals in other direction of the transmission. The main component to adjust the phase of the signal of each antenna element is called phase shifter. The operation of the phase shifter is normally controlled by microcontrollers or microprocessors. A basic diagram of the phased-array antenna system is shown in Figure 1.
At Silicon Radar, phased-array radar have been developed at millimeter-wave frequency, i.e., 120 GHz. For radar applications, the system consists of an array of receive, an array of transmitter a signal generator and an intermediate-frequency (IF) section. The block diagram and the layout of a Silicon Radar 120-GHz phased-array chip are shown in Figure 2 and Figure 3, respectively. It can be noted that, phase shifters are required on both transmitter and receiver arrays in order to selectively transmit and receive the signal in the required direction.