Radiation Characteristics of Phased Array Antennas with Reduced True Time Delay Devices - Numerical Analysis with Linear Array Antenna Models -

摘要

Phased array antennas (PAAs) have combinations of 360-degree phase shifters and true time delay (TTD) devices for the purpose of beam forming. The number of TTD devices is desirable to be reduced because PAA systems require miniaturization, lightness, and ease of control. The most obvious way to reduce the number of TTD devices is to group elements of the array into subarrays and to insert a TTD device into each subarray. However, if the number of TTD devices is reduced sharply when the PAA transmits or receives a wideband signal, the direction of the mainbeam at the off-center frequency shifts away from the target direction, because the wavefront of each subarray differs from a perfect wavefront at the center frequency. Gain variation, which depends on frequency in the target direction, occurs as a result of the beam shift. In this report, the results of the numerical analysis about the changes of electrical characteristics while reducing the number of TTD devices are shown. Since there is no noticeable degradation of characteristics, we conclude that the number of TTD devices can be reduced to about four.