Design of a high resolution HF phased array for ionospheric applications at the equator

The design of a high resolution HF phased array for mapping TIDs and spread-F irregularities of the equatorial ionosphere is described in detail. The high resolution radar is a phase coherent system comprising a broadband pulse transmitter, a thinly filled phased array, a bank of hf phase coherent receivers, an interface and a digital recording system. The receiving array consists of 16 identical short dipoles equally spaced around the circumference of a circle of 400 m diameter. A pencil beam of about 4 deg resolution can be synthesized at a frequency of 10 MHz and it can be scanned both in azimuth and elevation within an angular window of about 20 deg off zenith. The radar can be used to map the angular spectrum of the spread-F returns which will help develop useful models for the equatorial spread-F irregularities. In probing the TIDs, the radar by way of measuring the Doppler line, the range, and the angle of arrival of the signals reflected from the ionosphere, provides all the information necessary to determine the complete spectrum of the gravity waves and their propagation characteristics.