Phased Array Antenna Basics

The architecture of the phased array antennas has undergone a steady evolution over the years [1–3]. In the first generation of phased array antennas, as shown in Fig. 2.1, the antenna aperture was divided into a large number of antenna elements to realize beam agility, each with an electronically controlled phase shifter. However, the centralized high-power transmit and receive amplifiers were still used. In the 1980s, thanks to advancements in highly reliable solid state devices and MMIC technologies, solid-state transmit amplifiers were distributed and moved much closer to the antenna elements. As shown in Fig. 2.2, all the transmit amplifiers, low-noise receive amplifiers, phase shifters, and attenuators are integrated together and known as transmit/receive (T/R) module. Analog microwave components are used to realize analog beamforming. It has the adavantages of wide bandwidth and low power consumption. However, connections and interfaces for this type of beamforming are very complicated, strict microwave parameters and specifications are required. To form M simultaneous beams, the phase shifters and analog beamformers must be implemented in M times. Thus phased array antennas with analog beamforming were inherently constrained by the front-end beamforming electronics. As the number of beams increases, so does the analog components and the cost of a phased array antenna. As a result, it’s very difficult to generate multiple independent beams by analog beamforming in actual application.