A phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions. Phased arrays are extensively used in satellite communications, multipoint communications, radar systems, early warning and missile defense systems, etc., so they are employed in large quantities. In a conventional phased array system, the signal to be sent is divided into many branches using a power splitter and each branch is then fed into a phase shifter and followed by an antenna. The cost of a conventional phased array mainly depends on the cost of the phase shifters used. It has been estimated that almost half of the cost of a phased array is due to the cost of phase shifters. Because of the high cost of phase shifters, a significant amount of research has been performed to minimize the cost and improve the performance of phase shifters. In addition, conventional phased arrays result in very complex structures and suffer from high loss and mass.
Researchers at the University of Michigan have developed an extended resonance based phased array system for reducing and/or eliminating the need of a separate power splitter and phase shifter in a conventional phased array system. The extended resonance is a power dividing combining technique, which results in a very compact circuit structure with high dividing/combining efficiency (>90%). These phased arrays simply use varactors (capacitors whose capacitance can be varied with an applied DC voltage) for splitting the power and achieving the required phase shift. This approach eliminates the need for separate power splitter and phase shifters in a conventional phased array system, resulting in significant amount of reduction in the circuit complexity and cost.
Applications and Advantages
- Extended resonance based phased array system
- Satellite communications, multipoint communications, radar systems, early warning and missile defense systems
- Very compact and simple circuit structure
- Much lower cost