Fernando Beltran

Terrain compensation for OTHR receive array

The performance of an OTHR array situated on irregular terrain is presented, and the compensation of the effects of terrain irregularities is illustrated. The model used evaluates the effects of long correlation intervals on the received pattern by taking into account both the vertical terrain deformation and the effects of local ground tilt on the element pattern. A typical no-error pattern exhibits a -40 dB Taylor weighted sidelobe structure. Without beamformer compensation for terrain irregularities, the sidelobe performance is degraded to the -25 dB level. Using a beamformer compensation optimized for 10/spl deg/ elevation at azimuth boresight, the sidelobe performance is nearly fully recovered. The results obtained are very promising, and suggest that future OTH receive antenna ground preparation costs can be significantly reduced.<<ETX>>

Dual band cellular antenna

Several cellular provider companies have indicated significant interest in a single antenna assembly which could cover both cellular (UHF) and PCS1900 (L-band) frequency bands. A simple, low cost microstrip antenna solution has been developed, demonstrated and the results are presented.

Angle accuracy improvement using DMC randomization for phased array

It is shown that, as an alternative to using cable randomization, decorrelation can be obtained by randomizing the element phase settings at one half of the LSB value. As demonstrated in computer simulations for both methods, this randomization is not only more accurate than cable randomization; it can also be obtained cost-free in most modern phased arrays. To decorrelate the quantization error using DMC (distributed modular controller) randomization, a random number stored in a DMC register is added to DMCs phase shift calculation. The maximum value of this random number is one-half of the phase shifter LSB. The lower bound for the LSB of this random number is equal to the LSB of the DMC. Therefore, the number of bits in this random number is equal to or less than the difference between the DMC word length and the number of bits in the phase shifter. The choice of randomization bit length is affected by tradeoffs involving DMC cost and throughput and array pointing accuracy. Some of these tradeoffs are summarized for a 16-b DMC.<<ETX>>

Combination of numerical methods and simulator measurements for the optimization of array element designs

This paper addresses the design of a large class of phased array radiating elements for which only partial analytical models exist. A method is suggested that makes maximum use of the analytical model, integrating it with simulator measurements in such a way as to greatly simplify the optimization of the design.