Yogesh Ranga

Multioctave Frequency Selective Surface Reflector for Ultrawideband Antennas

In this letter, we demonstrate the gain enhancement of an ultrawideband (UWB) antenna, achieved using an appropriately designed multioctave dual-layer frequency selective surface (FSS) reflector. The proposed novel FSS reflects effectively in phase over a bandwidth of about 120%. Hence, significant enhancement in antenna gain has been achieved with a low-profile configuration without compromising the impedance bandwidth of the UWB antenna. The proposed FSS reflector has a low transmission coefficient and linearly decreasing phase over an ultra-wide frequency band, which is the key requirement for providing an effectively in-phase reflection at the antenna plane. The composite structure is compact, with a total height of λ/4, where λ is the free-space wavelength at the lowest operating frequency of 3 GHz. Experimental results show an impedance bandwidth of 122%. The antenna gain is maintained around 7.5 dBi from 3 to 7 GHz. Between 7-14 GHz, the antenna is more directive with a gain of about 9 dBi with ±0.5 dB variation. Experimental measurements con firm the predicted wideband antenna performance and gain enhancement due to the FSS reflector.

An Ultra-Wideband Quasi-Planar Antenna with Enhanced Gain

A new ultra-wideband antenna with enhanced and nearly constant gain is presented. This quasi-planar antenna is composed of a CPW-fed printed monopole and a short horn, both made out of a single substrate. The measurements demonstrate an almost ∞at peak gain of 5:5dBi § 0:7dB from 2.5GHz to 15GHz with the average gain difierence in XZ plane is roughly 2dB up to 8GHz, which further rise to 6dB at 10GHz. The antenna also has a nearly linear phase response in this band. Well tested performance both in frequency and time domains, along with broad azimuth pattern, results in minimal ringing of a radiated pulse. The new antenna is suitable for establishing good line of sight link for UWB transmission and other broadband applications.

A Single-Layer Frequency-Selective Surface for Ultrawideband Electromagnetic Shielding

An efficient approach to achieve the shielding effectiveness (SE) by using a frequency-selective surface (FSS) is presented. This FSS, which consists of cross dipoles and rings printed on the opposite sides of a single-layer FR-4 substrate, exhibits a wide, 7.5-GHz stopband to provide simultaneous shielding in both X- and Ka-bands. Experimental results confirm SE of the prototype over an ultra-wide band with more than 20-dB measured attenuation. The design is compact and suitable to provide shielding against the radiation interference caused by license-free and other radio systems.

A Simple Ultra Wideband Printed Monopole Antenna With High Band Rejection and Wide Radiation Patterns

A compact ultra wideband antenna with strong notch-band rejections up to VSWR = 26, that is tunable over a wide frequency range from 3.55 GHz to 6.8 GHz, is presented. It has wide radiation patterns and yields a measured 10 dB return-loss bandwidth from 3 GHz to 10.5 GHz.

A Constant Gain Ultra-Wideband Antenna with a Multi-Layer Frequency Selective Surface

An ultra-wideband (UWB) antenna with a novel multi-layer frequency selective surface (FSS) reflector is presented. A significant enhancement in the gain has been achieved in a low profile design while maintaining the excellent impedance bandwidth of the UWB antenna. The average peak gain of the antenna has been increased from 4 dBi to 9.3 dBi as a consequence of the use of the FSS reflector. More importantly the gain variation within the frequency range from 3 GHz to 15 GHz is only +/-0.5 dB. This is a significant improvement from §2 dB gain variation of the UWB slot antenna without the reflector. This optimized FSS re°ector provides the flexibility of mounting a planar antenna close to conducting bodies, including screens and cases

Development of a low-noise active balun for a dual-polarized planar connected array antenna for ASKAP

We describe the development of a low-noise active balun for a dual-polarized planar connected array antenna operating in the 0.7-1.8GHz frequency range. The device consists of two single-ended low-noise amplifiers (LNAs) operating at ambient temperature with a passive output-side balun. Issues of device characterization, matching and stability are discussed and techniques for measuring the signal and noise parameters are described. The viability of the approach is confirmed by preliminary measurements of noise temperatures less than 60K on a 5 × 4 array.

A printed antenna with a ground plane and electromagnetically coupled feed for 2.45GHz body area networks

This paper presents a printed antenna with a full ground plane and electromagnetically coupled feed for body area network devices operating in industrial, scientific, and medical (ISM) band at 2.45 GHz. Performance characteristics along with parametric analysis are presented. Specific absorption rate (SAR) analysis is carried out to investigate its performance for body centric wireless communication. The electromagnetically-coupled feed used is tuned to fill a null in the radiation pattern and to achieve impedance matching. The proposed antenna exhibits wide radiation pattern along the body surface to provide maximum coverage and its narrow width (14mm) makes it suitable for on-body applications.

An armband-wearable printed antenna with a full ground plane for body area networks

This paper presents a printed antenna with a full ground plane, suitable for wearable armbands and other such body area network devices operating in the industrial, scientific, and medical (ISM) band (2.45 GHz). Performance and characteristics are presented along with parametric analyses. Antenna performance is investigated under conformal bending over human arm to assess its suitability for armband-type body centric wireless communication devices. The full ground plane makes the antenna performance highly insensitive to the gap between the antenna and the arm. It also reduces electromagnetic radiation absorption in the arm. The proposed antenna exhibits a wide radiation pattern along the body surface to provide better coverage and its narrow width (14mm) makes it suitable for wearable on-body applications.

Increasing the gain of a semicircular slot UWB antenna using an FSS reflector

In this paper we demonstrate the gain enhancement of a semicircular slot antenna using a multilayer frequency-selective surface (FSS). A theoretical analysis of the FSS with a UWB semicircular slot antenna is presented. The multilayer FSS provides an appropriate reflection phase to act as a reflector and is able to enhance the gain of the slot antenna. Simulations show a linear phase response from 3.5 GHz to 12 GHz that is sufficient for ultra wideband operation. A significant improvement of 3 to 4 dB gain over the whole frequency range is demonstrated. The composite antenna has a theoretical gain of 8 dBi and a very small maximum gain variation of ±1.5 dB over the 3.5 to 10 GHz frequency range. Its compact configuration provides flexibility for mounting the reflector close to the slot antenna and makes it more suitable for modern UWB devices.

Stub-loaded printed antenna with a ground plane and electromagnetically coupled feed for 2.45GHz body area networks

This paper presents a stub-loaded printed antenna with a full ground plane and electromagnetically coupled feed for body area network devices operating in industrial, scientific, and medical (ISM) band at 2.45 GHz. Performance and characteristics are presented along with parametric analyses. Antenna performance is investigated under bending to check its suitability for conformal body centric wireless communication devices. The electromagnetically-coupled feed is tuned to fill a null in the radiation pattern and to achieve impedance matching, which is further fine tuned by stub loading. The proposed antenna exhibits a wide radiation pattern along the body surface to provide maximum coverage and its narrow physical width (14mm) makes it suitable for on-body applications.