Design of compact directive ultra wideband antipodal antenna

Abstract

wavelength at the center frequency of the desired notched-band, where A denotes the arc length between the feedline and cutting pie. Figure 4 illustrates the characteristics of various flare angles at position ϭ 50°. The larger the flare angle , the wider the notched band. According to the above design criteria, with a ϭ 11.6 mm, ϭ 2°, and ϭ 50°, a UWB with a bandwidth range from 3.061 GHz was proposed with a notchedband range from 4.880 to 5.925 GHz. This feature meets the requirement for interference immunity at 5.2/5.8 GHz. Figure 5 plots the measured radiation patterns at 4.1 and 8.2 GHz, respectively. The measured radiation patterns of the proposed antenna are about the same as those of the reference antenna (without cutting pie, ϭ 0°). Figure 6 depicts the measured antenna gains of the proposed and the reference antennas with respect to frequency, indicating a sharp notched-band, suppressed by the cutting pie between 4.880 and 5.925 GHz. The antenna gain is about the same for both the proposed and the reference antennas for the frequencies outside the notched frequency band. CONCLUSIONSA circular slot antenna fed with an indented circular stub presented to achieve the band-notched characteristic has been proposed. The cutting pie helps determine the notched band. The proposed printed antenna has ultra-wideband frequency, but avoids interference with the 5.2/5.8 GHz bands, which are occupied by existing wireless systems. INTRODUCTIONRecently, there has been great interest in the development of the radio frequency identification (RFID) tags. As the use of RFID systems increases, manufacturers are pushing toward higher operating frequencies (UHF band) for long reading range, reading speed, and anticollision [1]. The technology used to realize the antenna is perhaps the most important technology in RFID development. Designing a passive tag antenna matched with the complex microchip impedance is the most challengeable factor, since a microchip has very high Q because of its small resistance and large capacitive reactance. To overcome this problem, the inductively coupled feed is used to achieve a wideband impedance match between the antenna and the chip [2]. Also, the impedance of an RFID tag antenna varies when it is mounted on different objects. Especially, metallic objects strongly affect the antenna performance by lowering the tag's efficiency. Therefore, tag antennas have to be designed to enable tags to be read near and on metallic objects without severe performance degradation. Several microstrip patch antennas mountable on metal platforms have been proposed [3,4]. In this article, a microstrip patch-type tag antenna mountable on various metallic platforms is proposed. The antenna is inductively coupled by a novel feeding structure placed on the side of the radiator. This allows control of both the real and imaginary parts of the antenna impedance to achieve conjugate match with the various values of the microchip impedances. STRUCTURE AND DESIGNThe structure and dimension of the proposed antenna are sh...

An Overview of Uwb Antennas for Microwave Imaging Systems for Cancer Detection Purposes

“…The tapers are separated by placing one on the front face of the dielectric and the other on the back side, achieving a higher bandwidth than a conventional one [62]. Examples of this type of antennas can be observed in [71][72][73][74]. In [71,72], both antennas operate in UWB band frequency with total dimensions of 50 × 50 mm 2 on a RT6010LM substrate (ε r = 10.2) and maximum gains of 9 dB at high frequencies.…”

“…Examples of this type of antennas can be observed in [71][72][73][74]. In [71,72], both antennas operate in UWB band frequency with total dimensions of 50 × 50 mm 2 on a RT6010LM substrate (ε r = 10.2) and maximum gains of 9 dB at high frequencies. However, to improve directivity of the antenna, in [73] resistive layers were incorporated with the radiating elements of the antenna on an RT4003 substrate (ε r = 3.38).…”

Breast Cancer Diagnosis Using Microwave and Hybrid Imaging Methods

“…The system consists of a circular cylindrical scanning platform with a resolution of 1° to support a breast phantom, and a mechanical scanning platform with resolution of 0.1 mm in the vertical axis. The scanning platform supports an array of wideband antennas [22]. The antenna is connected to a microwave Vector Network Analyzer that measures the scattered signals.…”

Design and implementation of microwave imaging systems for medical applications

“…In addition, a realistic shape of the phantom is recommended. Tapered slot antennas (TSAs) are popular candidates for achieving these requirements [44][45][46]49] and are widely used in different applications, such as satellite communications, remote sensing, radio telescopes and microwave imaging systems. These kinds of antennas have high directivity, wide bandwidth, simple feed structure, and low cost.…”

“…The width of the microstrip transition feeder to give the characteristic impedance 0 = 50 can be calculated using the following equation [49]:…”