An Improvement to Directional Equiangular Spiral Antenna With Wide Cp Band, High Gain and Low Profile

Abstract

Abstract-An improved directional equiangular spiral antenna with wide CP band and high gain is proposed, in which the impedance bandwidth is 2 ∼ 12 GHz, CP bandwidth, 4.5 ∼ 7 GHz, and gain 6 ∼ 9.5 dBi. The antenna includes 4 layers. The top layer is equiangular spiral antenna, and the bottom layer is the ground. The middle two layers are parasitic metal films with irregular rectangular holes, which are introduced to improve the performance of equiangular spiral antenna and reduce the profile. The measured results are in good agreement with the simulated ones.

Improved spiral antenna with a new semi‐fractal reflector for short‐range sensing

“…The performance of a fractal reflector polarisation conversion is described in (16) and (19)- (21). These are the return loss (RL), defined as the ratio of the incident power and the reflected power in cross-polarisations S 11 RL and S 11…”

“…; insertion loss (IL), the ratio of the incident power and the transmitted power in co-polarisation S 11 RR and S 11 LL , and the axial ratio (AR) of the reflected signals; a measure of the polarisation purity of a CP wave [22].…”

“…Despite their benefits, equiangular spiral antennas are high profile and have low gain across the intended polarisation mode. Many attempts have been made to enhance spiral antenna characteristics such as antenna gain [3][4][5][6][7][8][9][10][11][12][13], circular polarisation (CP) [3,8,[10][11][12][13][14][15][16][17] and reduction of physical size [12,18,19]. Bidirectional radiation pattern can be changed to unidirectional by employing a reflector.…”

“…Photonic band gap (PBG) [4] and electromagnetic band gap (EBG) [5,8] structures can reduce the profile of spiral antenna, but decrease the bandwidth ratio. Using parasitic layers [6,11,13] could enhance the gain including improving the bandwidth ratio.…”