Ananjan Basu

Gain Enhancement of a CPW-Fed Monopole Antenna Using Polarization-Insensitive AMC Structure

A polarization-insensitive dual-band artificial magnetic conductor (AMC) structure is designed and experimentally verified. It consists of a planar array of annular ring-slot loaded rectangular patches. Details of the proposed structure and origin of the two bands is discussed. Through simulations and measurements, it is shown that the structure is insensitive to polarization of the incident wave. The tuning of the higher AMC band is demonstrated by varying the capacitance of the annular slot through its width variation. The designed AMC is used as a reflector for a wideband monopole patch antenna. It is shown experimentally at the antenna frequencies in the AMC band that the gain of the antenna improves by almost 10 dB and front-to-back ratio is improved by 15 dB.

Electromagnetic interference shielding effectiveness of SS/PET hybrid yarn incorporated woven fabrics

A detailed study of electromagnetic shielding effectiveness (EMSE) of woven fabrics made of polyester and stainless steel/polyester blended conductive yarn was presented in this research work. Fabrics with different structures were analyzed and their shielding behavior was reported under different frequencies. Shielding efficiency of fabric was analyzed by vector network analyzer in the frequency range of 300 kHz to 1.5 GHz using coaxial transmission line holder. The effects of different fabric parameters such as weft density, proportion of conductive weft yarn, proportion of stainless steel content, grid openness, weave pattern and number of fabric layers on EMSE of fabrics were studied. The EMSE of fabric was found to be increased with increase in proportion of conductive yarn in the weft way. With increase in overall stainless-steel content in the fabric, the EMSE of fabric was increased. As such weave is considered, it did not have significant effect on EMSE of fabrics. But fabric with lower openness and aperture ratio showed better conducting network, hence better shielding. With increase in number of layers of fabric and ply yarns, EMSE of fabric was increased.

Polarization reconfigurable microstrip antenna

Microstrip patch antenna with circular corner truncation is proposed to achieve polarization reconfigurability. By applying forward bias, reverse bias or zero bias to the four PIN diodes, the antenna can radiate with Right Hand Circular Polarization (RHCP), Left Hand Circular Polarization (LHCP) and Linear Polarization(LP). Simulations as well as experimental results show that proposed antenna demonstrates a very good impedance match for all the three different polarizations without any additional matching network.

FSS Properties of a Uniplanar EBG and Its Application in Directivity Enhancement of a Microstrip Antenna

In this letter, frequency selective surface (FSS) properties of a uniplanar electromagnetic band-gap (EBG) unit cell are studied. The unit cell consists of meander-line inductor and interdigital capacitors on one side of a substrate. Simulation results indicate that the unit cell exhibits passband characteristics centered at 10.04 GHz. FSS property of the structure is verified by measurement using X-band waveguides. The measured results show passband characteristics at 9.45 GHz. A 13 × 13 array of these unit cells (FSS screen) is used as a superstrate at a distance ≈ 0.5λ0 over a patch antenna operating at 10.8 GHz, offset from center frequency of the FSS passband. Directivity improvement of 6.95 dB is observed along 0° in the measurements of patch antenna with FSS superstrate as compared to the patch antenna without superstrate.

Switchable and Tunable Notch in Ultra-Wideband Filter Using Electromagnetic Bandgap Structure

A simple technique to reconfigure a notch filter employing a 1-D electromagnetic bandgap (EBG) structure, which is capacitively coupled to a microstrip line, is presented in this letter. The resonant nature of the EBG creates a notch in the transmission band. The notch filter is made reconfigurable/tunable by introducing an additional capacitive structure to change the size (geometry) of the EBG unit cell. The structure is connected or disconnected to the main structure (unit cell) by means of a PIN diode or varactor diode. Its application in notched-band ultra wideband (UWB) filter is demonstrated. A 450 MHz change in notch frequency is observed using PIN diode, and 340 MHz tuning range is observed using varactor diode.

UWB Printed Slot Antenna with Improved Performance in Time and Frequency Domains

A microstrip-fed slot antenna is proposed for short-range UWB communication. First, the characteristics of a conventional circular monopole UWB antenna, as a representative of a class of UWB antennas seen in the literature, are examined in time (pulse-shape) and frequency (re∞ection and transmission coe-cients) domains. From these measurements, certain limitations of this class of antennas are brought out, which are not widely recognized. We then demonstrate that with proper optimization the traditional microstrip-fed slot antenna overcomes these defects and is an excellent candidate for UWB communication systems. This claim is justifled with measurements in time domain and frequency domain.

Efficient Spurious Rejection and Null Steering Using Slot Antennas

Reconfigurable antennas are susceptible to spurious signal reception through feed lines, interconnects and connector transitions. In this letter, a two-slot antenna backed by a metal box is demonstrated, where such spurious signals are not picked up and, consequently, spurious rejection is very high. It is shown that the direction from which signals are strongly rejected is also switchable. Finally, a four-slot array for rejecting spurious signals over some angular range, rather than at a specific angle, is presented .

Dual port ASA for frequency switchable active antenna

This report presents the design of a dual-port dual-band annular slot antenna suitable for use in the feed-back path of an oscillator resulting in an active antenna configuration. The proposed antenna is designed to radiate and transmit equal amounts of power. The return loss of the proposed antenna is higher than that desired for one-port antenna application at the desired dual-band frequencies. The antenna is fabricated on one side of a Neltec substrate (εr=3.2 and thickness = 0.762 mm) and the microstrip feeding line is fabricated on the opposite side of the board. The antenna was designed to operate at WLAN bands centered at 2.4 and 5.2 GHz. The simulated and measured results show fairly good agreement. The measured return losses were found 20.5 dB at 2.4 GHz and 13.9 dB at 5.2GHz while simulated return losses were 9.36 dB at 2.4 GHz and 31.35 dB at 5.2 GHz. The radiation pattern is approximately omnidirectional at both frequencies in H-plane.

Dielectric waveguide-based leaky-wave antenna at 212 GHz

The design and fabrication of a leaky-wave antenna at 212 GHz with a dielectric waveguide as the guiding structure is described and some measured results are presented. At this frequency, previously reported approaches for fabricating such an antenna present certain difficulties, which have been overcome using some innovations. This antenna is expected to be useful for radiometry and, consequently should have small beamwidth, high efficiency, and large beam scanning with frequency. It is shown how these can be achieved.

An Ultra-Wideband Antenna with Band Reject Capability and its Characterization in Time Domain

In this paper a square monopole antenna has been proposed which can be used for Ultra Wideband applications. Band- notch performance is introduced by an E-shaped slot on the patch. The dimensions are optimized to give not only the usual 3{10GHz bandwidth with rejection in the 5{6GHz band which is commonly used for WLAN, but also short received pulse duration when transmitted and received using a pair of these antennas. The demonstration of short received pulse-width is the primary novelty reported. The performance is verifled by time domain measurements, in addition to the usual antenna characterization.