D. R. Poddar

A Compact UWB Bandpass Filter With Embedded SIR as Band Notch Structure

In this letter, an ultrawideband (UWB) bandpass filter with a band notch is proposed. The UWB BPF (3.1-10.6 GHz) is realized by cascading a distributed high-pass filter and an elliptic low-pass filter with an embedded stepped impedance resonator (SIR) to achieve a band notch characteristic. The notch band is obtained at 5.22 GHz. It is shown that the notch frequency can be tuned by changing the impedance ratio of the embedded SIR. A fabricated prototype of the proposed UWB bandpass filter is developed. The inband and out-of-band performance obtained by measurement, EM simulation, and that with an equivalent circuit model are in good agreement.

A Wideband Minkowski Fractal Dielectric Resonator Antenna

A CPW slot loop fed Minkowski shaped fractal dielectric resonator antenna is proposed. Self similar property of fractal geometry is utilized to bring higher order modes close together to realize a wide impedance bandwidth. A comparative study of the resonant frequency behavior between the well established fractal electrical boundary antennas and fractal magnetic boundary antennas is presented to provide insight into the functionality of the proposed antenna. The comparison highlights the fact that electrical boundary lowers resonance frequency, whereas fractal magnetic boundary increases the resonant frequency. Minkowski fractal is also compared with Koch fractal and Sierpinski curve geometries. It is observed that the Minkowski fractal DRA yields the widest impedance bandwidth along with stable gain amongst the three proposed geometries. The proposed antenna exhibits a fractional bandwidth of 64% (5.52 -10.72 GHz) and a maximum gain of 4.9 dBi.

Compact UWB Bandpass Filter With Dual Notch Bands Using Open Circuited Stubs

In this letter, an ultra-wideband (UWB) bandpasss filter with multiple notch bands is presented. The UWB bandpass characteristic is achieved using a modified distributed highpass filter (HPF) and suppressing higher order harmonics of the HPF by realizing defected stepped impedance resonator. The dual band notches at 5.75 and 8.05 GHz are obtained by embedding two open stubs on the main microstrip line. The in band and out of band performance obtained from fullwave electromagnetic simulation, equivalent circuit model and measurement are in good agreement.

A CIRCULAR SHAPED SIERPINSKI CARPET FRACTAL UWB MONOPOLE ANTENNA WITH BAND REJECTION CAPABILITY

A novel planar ultra wideband (UWB) antenna using a second iteration Sierpinski carpet fractal shape with circular boundary is presented in this paper. The antenna covers the frequency band from 3GHz to 12GHz (VSWR • 2). The proposed antenna has a meander shaped slot that renders the capability to reject 5.15{5.825GHz band assigned for IEEE802.11a and HIPERLAN/2. The gain is suppressed very well in the desired WLAN bands. The measured antenna peak gain varies from 1.85dBi to 6dBi within the band. The time domain characteristics show that the antenna is not dispersive. A fabricated prototype is developed with close agreement between simulated and measured resonance as well as radiation characteristics.

A Dielectric Resonator-Loaded Minkowski Fractal-Shaped Slot Loop Heptaband Antenna

A multiband fractal co-planar waveguide (CPW)-fed slot antenna loaded with a dielectric resonator conforming to multiple wireless standards is presented in this paper. The Minkowski fractal geometry is utilized to generate multiple frequency bands as well as to provide a miniaturized design compared to its Euclidean counterpart. The idea behind placing the dielectric load is to serve a dual purpose of enhancing the impedance bandwidth of the antenna at the upper frequency band as well as improving the overall gain of the antenna. The slot loop acts as a hybrid antenna performing the task of both an antenna as well as a feed mechanism for the dielectric slab to radiate. Design guidelines involving closed form formulae and equivalent model consisting of lumped resonators, distributed resonators and impedance transformers of the dielectric-loaded fractal slot antenna are provided to present an insight into the functioning of the antenna. The reflection coefficient parameters of the antenna yield a close match between the circuit model and those obtained from full wave simulator. The proposed antenna exhibits a heptaband performance with a maximum gain of 3.1 dBi.

Perturbed Sierpinski Carpet Antenna With CPW Feed for IEEE 802.11 a/b WLAN Application

A printed antenna useful for IEEE 802.11 a/b WLAN application is proposed in this letter. The antenna adopts a modified Sierpinski carpet geometry in planar monopole configuration. Design steps to achieve the desired resonance characteristics are discussed. Return loss characteristics suggest that the antenna is also suitable for HiperLAN2 system. The peak realized antenna gain is around 3.2 dBi at the lower band and 4.5 dBi at the higher band.

Dielectric Resonator Antennas: Designs and Advances

This article presents a comprehensive review of the research carried out on Dielectric Resonator Antennas (DRAs) over the last three decades. Dielectric resonator antennas (DRAs) have received increased attention in various applications due to their attractive features in terms of high radiation e-ciency, light weight, small size and low proflle. Over last decades, various bandwidth enhancement techniques have been developed for DRAs. In this article, the attention is focused on a type of DRAs that can ofier multi-resonance frequencies and these frequencies can be merged into a broad band. In order to efiectively review design techniques, DRAs in this article are categorized into three types, broadband, ultra-wideband (UWB) and multiband. The latest developments in DRAs are discussed in the limited scope of this article.

A CIRCULAR FRACTAL UWB ANTENNA BASED ON DESCARTES CIRCLE THEOREM WITH BAND REJECTION CAPABILITY

A novel planar circular Apollonian fractal shaped UWB monopole antenna with band rejection capability is presented in this paper. The antenna performs satisfactorily in the frequency range 1.8{10.6GHz which gives a wide impedance bandwidth of 142% for VSWR within 2. The proposed antenna has the capability to reject the frequency band 5.125{5.825GHz assigned for IEEE802.11a and HIPERLAN/2. This is achieved by a pair of narrow band resonant L-shaped slots in the CPW ground plane. The antenna exhibits satisfactory omnidirectional radiation characteristics throughout its operating band. The measured peak gain varies from 2dBi to 6dBi in the entire UWB band except the notch band. The performances of time domain characteristic is satisfactory with a group delay variation of 1ns that shows the antenna is non dispersive. To ensure the usefulness of the proposed antenna in pulse communications systems, the correlation between the time-domain transmitting antenna input signal and the receiving antenna output signal is calculated. This antenna can be efiectively used for medical imaging and military radar system along with other common UWB applications.

An UWB antenna using modified Hilbert curve slot for dual band notch characteristics

A printed dual band notched ultra wideband monopole antenna with a single perturbed Hilbert curve slot is presented which exhibits 121% impedance bandwidth. A single modified Hilbert curve slot provides dual band notch characteristics in the range of 3.3–3.7 GHz (WiMAX), 3.7–4.2 GHz (C-Band), and 5.15–5.825 GHz (WLAN) which makes the notch design process simpler than other dual band notched antennas. The gain of the proposed antenna varies from 3 to 4 dBi over its operating frequency range, except at the rejection bands. Suitable radiation characteristics are obtained throughout its operating band. Simulation and measured results of the proposed antenna are in good agreement.

On some broad-band microstrip resonators

The variation of voltage standing-wave ratio (VSWR) with frequency for microstrip antennas on stepped and wedge-shaped dielectric-substrates is measured for a band of frequencies, and is compared with those of an equivalent rectangular microstrip resonator. The results indicate a considerable improvement in bandwidth.