A three beam phased array antenna capable of two frequency harmonic operation

• Main Authors: Janardhanan, K.V, Mukundan, K.K, Shenoy, K.S.V
• Format: Conference Proceeding
• Language: English
• Subjects: Antenna accessories; Antenna arrays; Atmospheric, ionospheric and magnetospheric techniques and equipment; Instrumentation and techniques for aeronomy, space physics, and cosmic rays; Ionosphere; Radar equipment, systems and applications
• DOI: 10.1049/cp:19940497

Large phased array antennas are often employed in HF/VHF radars used for atmospheric studies to generate narrow switchable beams. For the realisation of narrow beamwidth (less than 10 degrees) the size of the array has to be many times the operating wavelength. Thus narrow beam antenna arrays operating at these frequency ranges occupy large areas. If the bandwidth requirement is small, resonant element antennas can be employed for the array to simplify the array design substantially. For wideband operation of the array resonant antennas cannot be used and very short antennas, log-periodic antennas etc. have to be employed which result in increased complexity. There are situations where one wants to operate the radar only at two or three selected spot frequencies and does not require operation at all the frequencies in the band. In such situations one need not design the array for wideband operation. The paper describes the use of a single array antenna for operation at two harmonically related frequencies. The array forms a part of an HF radar system used to study equatorial ionospheric irregularities. The backscattered echoes are mainly from irregularities of scale sizes corresponding to half the radar wavelength (Bragg scattering). Thus by employing two operating wavelengths for the radar, the characteristics of irregularities of two different scale sizes can be studied. The paper describes the design of a 12×6 dipole array antenna covering a physical aperture of 13300 m2 which is capable of operation at two frequencies.