Fermi Antenna Research Articles

High gain Fermi antenna array for radar-aided radiotherapy system

This article presents the design of Fermi antenna array with improved gain for radar respiration measurement. A six-element Fermi antenna array working at 5.8 GHz is optimally designed and integrated with the respiration radar system. Specifically, to easily feed the antenna array as well as reduce the total size of the array system, a feeding network based on 0-degree phase shifters is used along with suitable impedance transformers. The whole system is proposed to function as a radar sensor for respiration rate measurement, which is known as a promising noncontact and noninvasive approach for lung cancer radiotherapy. The measurement results verify the improved performance of the proposed system for radar respiration measurement in motion-adaptive lung cancer radiotherapy. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1649–1654, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26871

High Gain Antipodal Fermi Antenna with Low Cross Polarization

Antipodal Fermi antenna (APFA) that uses an antipodal feeding section is proposed and its fundamental characteristics are presented. It is shown that the cross polarization level is decreased by 5-10dB by the presence of the corrugation. It is also found that high gain, low VSWR and low side lobes and low back lobes are obtained. The mechanism of operation principles is discussed by using FDTD analysis. It is found that the corrugation transforms the current of parallel line mode to the current of traveling wave radiation mode and the effective aperture is enlarged which yields high gain characteristics.

Modified antipodal Fermi antenna with piecewise-linear approximation and shaped-comb corrugation for ranging applications

The authors propose the dual-tapered structure consisting of piecewise-linear inner taper and outer shaped-comb corrugation and the antipodal feeding section to present a modified antipodal Fermi antenna. This antenna exhibits the performance with wider band (3.6–15 GHz) in return loss responses, moderately high gain (5.1–14.5 dBi), high front-to-back ratio (24.8–38.9 dB) and available end-fire (29.8° beamwidth and −18.7 dB side lobe level) in radiation patterns. The current distributions demonstrate the characteristics of leakage, transverse waves among dual-taper and transition on balun. The proposed antenna presents the longitudinal conformation for mounting application and evaluate the pulse responses with linearity test for ultra-wideband (UWB) ranging and imaging applications.

Ultra-Wideband Fermi Antenna Using Microstrip-to-CPS Balun

A new design and experimental results of a microstrip-fed ultra-wideband Fermi antenna at millimeter-wave frequencies are presented. By utilizing a new microstrip-to-CPS balun (or transition), which provides wider bandwidth than conventional planar balun, the design of microstrip-fed Fermi antenna is greatly simplified. The proposed Fermi antenna demonstrates ultra-wideband performance for the frequency range of 23 to over 58GHz with the antenna gain of 12 to 14dBi and low sidelobe levels. This design yields highly effective solutions to various millimeter-wave phased-arrays and imaging systems.

Multi-Channel Microwave Reflectometer with Fermi Antenna Receivers

We have evaluated a Fermi antenna newly designed in X band for use in a multichannel reflectometer. The advantages of the Fermi antenna are that it can be adopted as an array antenna owing to its planer shape and fabricated with a low cost due to its compactness and a light-weighted structure. The radiation-beam widths in the E- and H-plane are almost equal to each other and the side-lobe levels are low. Plasma behaviors in the HITOP device are measured by reflectometry using two Fermi antenna receivers. Time evolution of the cutoff layer and plasma rotation velocity measured by the reflectometer are in good agreement with an electrostatic probe measurement.

Evaluation of tapered slot antennas for use in multichannel reflectometers

We have evaluated a Fermi antenna newly designed in X band for use in a multichannel reflectometer. The Fermi antenna is a tapered slot antenna provided with both a Fermi–Dirac-function-type tapered slot structure and a corrugated structure along the antenna edge in order to improve radiation patterns of the linearly tapered slot antenna. We attained a 3 dB beam width of 32° in the E plane and 37° in the H plane at 12 GHz. By optimizing the stripline dimensions according to an equivalent circuit model, a bandwidth of 8–18 GHz with a voltage standing-wave ratio less than 2 is obtained. In the mockup experiments using a rotating metal cylinder, the experimental results are in good agreement with the predicted ones.