Front-to-back ratio

About: Front-to-back ratio is a research topic. Over the lifetime, 292 publications have been published within this topic receiving 3314 citations.

A 6-Port Two-Dimensional $3\times 3$ Series-Fed Planar Array Antenna for Dual-Polarized X-Band Airborne Synthetic Aperture Radar Applications

Abstract: A six-port $3\times 3$ series-fed planar antenna array design for dual polarized X-band airborne synthetic aperture radar (SAR) applications is presented in this paper. The antenna array patches interconnected with series feeding one to another as the structure to realize directional radiation and vertical/horizontal polarization. The patch elements are excited through $50~\Omega $ microstrip line feeding in series with quarter wave transformer for good impedance characteristics. A six-port feeding allows selecting the direction of the traveling waves, and consequently the sense of linear (vertical and horizontal) polarization. A prototype of the antenna is fabricated and validated the proposed method. The dimensions of the fabricated prototype $3\times 3$ array antenna are $3.256\lambda \text {g} \times 3.256\lambda _{\mathrm {g}}\times 0.0645\lambda _{\mathrm {g}}$ ( $\lambda _{\mathrm {g}}$ is guided wavelength at center frequency 9.65 GHz). The measured S11 < −10 dB reflection bandwidths are 1.4% at each port. Furthermore, an interport and intraport isolation S21<−25 dB was also achieved across the operation band. The measured peak gains are higher than 11.5 dBi with 90% efficiency for all individual ports/polarizations V1, V2, V3 H1, H2, and H3). In order to satisfy the different performance requirement of series-fed array antenna, such as realized gain, radiation efficiency, side lobe level, half power beam width and front to back ratio are also examined. Measured results of an antenna prototype successfully validate the concept. The proposed antenna is found suitable for dual polarized airborne SAR applications.

Open slot antenna in a small ground plane

Abstract: The impact of a finite ground plane on an open-slot antenna performance is reviewed and the far-field pattern behaviour is clarified. The pattern of this slot configuration is fundamentally different to its complementary dipole. Here, a parametric study of a slot antenna is presented including the impact and use of a small groundplane with different sizes and bending angles along the slot axis. As a result, the authors demonstrate a simple, effective antenna comprising a slot in a small groundplane, which has direct matching to 50 Ω, high efficiency and medium gain over a wide bandwidth. The slot length at the second resonance dictates the centre frequency, and the slot width influences the bandwidth. Only a small groundplane is required to maintain the performance. The impedance is also insensitive to the groundplane bending angle from 180° (flat) down to 30°. This bent groundplane configuration allows some control over the front-to-back ratio, and thence the directivity.

Mushroom meta-material based substrate integrated waveguide cavity backed slot antenna with broadband and reduced back radiation

Abstract: A novel substrate integrated waveguide (SIW) cavity backed slot antenna with low back radiation is proposed in this study. This newly proposed meta-mushroom antenna uses a SIW cavity to decrease the back radiation. It is fed by the SIW cavity backed slot and radiates by meta-mushroom structure. This antenna exhibits broadband characteristics due to the meta-mushroom structure and a bow-tie slot on the SIW. The back radiation of the proposed antenna is considerably diminished by the SIW cavity located at the back side maintaining high gain performance. After all, its front-to-back ratio is increased and maintained over 19.2 dB in the operating frequency band, 4.5–5.6 GHz. Full-wave simulation and experiments results of the proposed antenna are demonstrated.

Compact, wideband-printed quasi-Yagi antenna using spiral metamaterial resonators

Abstract: A novel structure for size reduction and bandwidth enhancement of quasi-Yagi antenna using spiral resonator (SR) metamaterials is presented. The basic resonance is produced through excitation of simple quasi-Yagi antenna elements through a microstrip feedline while parasitic SR metamaterials augment bandwidth. The antenna is designed on an glass-reinforced epoxy laminate sheets (FR4) substrate with a dielectric constant of 4.4 and a thickness of 1.6 mm. Compared to original printed quasi-Yagi antennas, the size of the proposed quasi-Yagi antenna is reduced by ∼53%. Simulation results show that the proposed antenna has the impedance characteristics with a frequency bandwidth of 1.43–3.97 GHz (94%) for return loss more than 10 dB and a gain of 3.4–5.2 dBi in the corresponding frequency range. The designed antenna presents an end-fire radiation with a front-to-back ratio >10 dB. The antenna is fabricated, and measurement results demonstrate compactness and wide bandwidth of the antenna.