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.

Flexible and Compact AMC Based Antenna for Telemedicine Applications

Abstract: We present a flexible, compact antenna system intended for telemedicine applications. The design is based on an M-shaped printed monopole antenna operating in the Industrial, Scientific, and Medical (ISM) 2.45 GHz band integrated with a miniaturized slotted Jerusalem Cross (JC) Artificial Magnetic Conductor (AMC) ground plane. The AMC ground plane is utilized to isolate the user's body from undesired electromagnetic radiation in addition to minimizing the antenna's impedance mismatch caused by the proximity to human tissues. Specific Absorption Rate (SAR) is analyzed using a numerical human body model (HUGO) to assess the feasibility of the proposed design. The antenna expresses 18% impedance bandwidth; moreover, the inclusion of the AMC ground plane increases the front to back ratio by 8 dB, provides 3.7 dB increase in gain, in addition to 64% reduction in SAR. Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas. Furthermore, it offers a compact and flexible solution which makes it a good candidate for the wearable telemedicine application.

Bandwidth-Enhanced Low-Profile Cavity-Backed Slot Antenna by Using Hybrid SIW Cavity Modes

Abstract: A bandwidth enhanced method of a low-profile substrate integrated waveguide (SIW) cavity-backed slot antenna is presented in this paper. Bandwidth enhancement is achieved by simultaneously exciting two hybrid modes in the SIW-backed cavity and merging them within the required frequency range. These two hybrid modes, whose dominant fields are located in different half parts of the SIW cavity, are two different combinations of the and resonances. This design method has been validated by experiments. Compared with those of a previously presented SIW cavity-backed slot antenna, fractional impedance bandwidth of the proposed antenna is enhanced from 1.4% to 6.3%, its gain and radiation efficiency are also slightly improved to 6.0 dBi and 90%, and its SIW cavity size is reduced about 30%. The proposed antenna exhibits low cross polarization level and high front to back ratio. It still retains advantages of low-profile, low fabrication cost, and easy integration with planar circuits.

Multiple-element driven array antenna and phasing method

Abstract: An antenna array for direction-agile applications, such as r.f. packet mesh networks, employs a plurality of quarter-wave radiators disposed normally to a ground plane on a dielectric backing and switching elements for selecting a desired receiving direction and transmission direction and minimizing interference from signals in opposing directions. A control system selects and switches direction rapidly enough to receive and transmit digipeating signals in selected different directions using the phasing and switching elements. A specific embodiment employs eight radiators of 0.2625 electrical wavelengths (quarter wave plus 5%) disposed equidistant along a circle within a circular ground plane in a pattern which is 1/4 wavelength from the outer boundary of the ground plane, each radiator being disposed at least 0.15 wavelengths to about 0.25 wavelengths from adjacent radiators in a circular pattern. The antenna is characterized by eight electronically switchable radiating directions (at 45° intervals) with at least 20 dB front to back ratio and a 3 dB beamwidth of 64°. Pairs of radiators form parasitic elements, driven elements and reflectors with spacing selected as a modest compromise from the ideal spacing to allow electronically selectable directionality using identically-spaced elements acting as driven elements, parasitic elements and reflector elements. The driven elements are slightly reactively fed.

Dielectric Resonator Antenna for X band Microwave Application

Abstract: A simple Dielectric Resonator Antenna (DRA) for X band frequency operation is proposed in this paper. X band is a microwave band lies between frequency range 8 to 12 GHz. In proposed DRA reflector plane is used beneath the microstrip feed line with a small air gap, introduced between feed substrate and reflector plane to reduce the back lobe. Slot coupling is used to excite this DRA. Proposed DRA design gives dual band operation in X band and resonates at frequency 8.6 GHz and 10.3 GHz. Antenna design offers minimum return loss of -20.3 db and -24.5 db at 8.6 GHz and 10.3 GHz respectively. It also offers high front to back ratio (FBR) of 12.35db and 9.83 db at 8.65 GHz and 10.3 GHz respectively. Return loss impedance bandwidth of 390 MHz (4.5%) for Band I and 730MHz (7.3%) for band II is obtained. Simple DRA design with high FBR is proposed here for X band application that shows a total bandwidth of 11.8%. DRA is analysed using Ansoft HFSS based on finite element method. Radiation characteristics of this DRA are observed at resonating frequencies. This DRA is useful at microwave X band application such as satellite communication.

Coplanar waveguide fed quasi-Yagi antenna

Abstract: A novel coplanar waveguide fed quasi-Yagi antenna is presented. A wide bandwidth is achieved by using a broadband coplanar waveguide to a slotline balun. An X-band prototype has been realised which demonstrates a broad bandwidth (30%), –19 dB front-to-back ratio, and cross-polarisation better than -17 dB at 10 GHz.