In this article, a balanced symmetrical low cross polarization (X‐pol) substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is presented. The unit cell of the LWA consists of transverse and longitudinal slots, which provide series and shunt resonant elements, essentially required to radiate at broadside direction efficiently. The radiating slots are arranged in a way such that the unit cell is symmetrical around the centerline so as to achieve the low X‐pol levels. Moreover, the shape of the longitudinal slots are changed and optimized to match the unit cell impedance to the characteristic impedance of the SIW. Parametric constraints of the radiating slots are studied for achieving the continuous beam scanning and the best low X‐pol in the presented LWA. The final presented LWA is capable of continuous beam scanning from −28° to +30° within a frequency range of 9.5‐15.2 GHz including broadside at 12.2 GHz. Moreover, the X‐pol levels are better than −40 dB all over the scanning frequency range. Finally, the antenna prototype is fabricated and tested. Simulated and measured results are in good agreement. The maximum gain of the antenna measured is 13.8 dB.
A planar asymmetric substrate integrated waveguide leaky wave antenna is proposed with open stop band suppression and radiation efficiency equalization through broadside for the Ku-band. The stop-band behavior exhibited at broadside in the 1-D periodic structure is significantly reduced using reflection cancellation technique by placing the two slots at a quarter distance within the unit cell. Furthermore, asymmetric technique is applied. The asymmetry is introduced with respect to both axial and transversal axis of the structure so as to match the atbroadside Bloch impedance and off-broadside Bloch impedance. This provides total open stop band suppression and radiation efficiency improvement as well as equalization through broadside. The problem is analyzed with the help of Bloch impedance behavior. For illustration of the above techniques; single slot, double slot and asymmetric designs are developed for the proposed leaky wave antenna. The final asymmetric design after optimization is fabricated. Measured results are almost consistent with the simulation results with complete suppression of open stop band, efficiency improvement and equalization through broadside providing continuous beam scanning from -32° to +27° with constant gain of ~12.5 dBi.
Abstract-A planar substrate integrated waveguide leaky wave antenna (LWA) with cross slots is proposed in the frequency range of 10 GHz-15.5 GHz. Moreover, the symmetrical version of the structure is designed and analyzed in terms of the simulated S-parameters and E-field distribution which shows the existence of the open stopband in the frequency range from 12.91 GHz-14 GHz, consequently degrading the radiation beam at broadside. Therefore, asymmetry is introduced in the unit cell design w.r.t the position of the cross slots to achieve the continuous beam scanning in the desired frequency range. The unit cell is analyzed with the help of dispersion relation and Bloch impedance for predicting the beam scanning and matching of the proposed LWA respectively. This planar LWA is fabricated by the standard printed-circuit board process. Measured results are almost consistent with the simulation ones with a continuous beam scanning from of −40 • to +16 • with gain varying from 8.5 dBi to 11 dBi.
A half mode substrate integrated waveguide (HMSIW) based leaky wave antenna (LWA) featuring low cross-polarization is proposed in this paper. The umbrella-shaped slot (the combination of longitudinal and transverse slots) is etched on the top layer of HMSIW LWA to get the efficient broadside radiation. The scanning range is obtained from −47° to +30° in a frequency range of 8.3 to 15.1 GHz. The cross-polarization level for the LWA is around −10 dB at broadside. In order to improve the cross-polarization levels in HMSIW LWA, two antennas are placed face to face obtaining the balanced symmetry across the longitudinal axis. Both the simulated and measured results show that the antenna is able to scan continuously from backward to forward direction with a very good low cross-polarization level. The developed prototype is capable of continuous beam scan from −29° to +32° in an operating frequency band of 9.2 to 15 GHz with a maximum gain of 13.5 dBi. The measured cross-polarization level is −30 dB which is quite low for the main beam at the broadside direction.
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