APPLICATIONS OF THE ARRAY IN RADAR

                

              The phased-array antenna has been of considerable interest to radar systems engineer because its properties are different from those of other microwave antennas.The array antenna takes several forms 

Mechanically scanned array.  :  The array antenna in this configuration is used to from a fixed beam that is scanned by mechanical motion of the entire antenna.No electronic beam steering is employed.This is an economical approach to air-surveillance radars at the lower radar frequencies, such as VHF. It is also employed at higher frequencies when a precise aperture illumination is required, as to obtain extermely low sidelobes. At the lower frequencies, the array might consist of slotted waveguides.

Linear array with frequency scan:. The frequency - scanned, linear array feeding a parabolic cylinder or a planer array of slotted  waveguides has seen wide application as a 3D air-surveillance radar. In this application, a pencil beam is scanned in elevation by use of frequency and scanned in azimuth by mechanical rotation of the entire antenna.

Linear array with phase scan. :      Electronic phase steering instead of frequency scanning, in the 3D air-surveillance radar is generally more expensive, but allows the use of the frequency domain for purposes other than beam steering.The linear array configuration is also used to generate multiple, contiguous fixed beam (stacked beam ) for 3D radar.Another application is to use either phase- or frequency- steering in a stationary linear array to steer the beam  in one angular coordinate, as the CGA radar.

Phase-frequency planar array :    A two-dimensional (planer) phased array can utilize frequency scanning to steer the beam in one angular coordinate and phase shifters to steer in the orthogonal coordinates, but as with any frequency-scanned array the use of the frequency domain for other purposes is limited when frequency employed for beam steering

Phase-phase planer array :             The planar array which utilizes phase shifting to steer the beam in two orthogonal coordinates is the type of array that is of major interest for radar application because of its inherent  versatility.Its application, however, has beam limited by its relatively high cost. The phase-phase array is what is generally implied when the term electronically steered phased array is used 

The phased array antenna has seen application in radar for such purpose as aircraft surveillance  from on board ship (AN/SPS-33), ballistic missile defense (PAR, MSR), air defense (AN/SPY-1 and patriot), aircraft landing systems (AN/TPN-19 and AN/TPS-32) mortar (AN/TPQ-36)and artillery (AN/TPQ-37) location tracking of ballistic missiles (Cobra Dane), and airborne bomber radar (EAR)

There have been many  developmental array radars, built in the United States, including ESAR, ZMAR, MAR, Typhon, Hapdar ADAR, MERA,  RASSR, and others. Although much effort and funds have been expended, except for limited-scan arrays there has been no large serial production of such radars comparable to serial production  of radars with mechanically rotating reflector antennas.