A. K. Verma

Control of bandstop response of Hi-Lo microstrip low-pass filter using slot in ground plane

This paper examines the effect of the geometrical shapes of a defected ground-plane structure (DGS) slot on performance of the Hi-Lo microstrip low-pass filter (LPF). A three-pole LPF based on an arrowhead DGS slot has 67% less length as compared to a conventional three-pole LPF. It has insertion loss of 0.5 dB and 15-dB rejection in the stopband up to three times the cutoff frequency.

Wideband Circularly Polarized Stacked Microstrip Antennas

A simple technique is developed to improve the axial ratio (AR)-bandwidth and quality of circularly polarized stacked microstrip antennas (CPSMAs) using a new C-type single feed. The proposed antenna has been optimized and fabricated, and the computed results agree very well with measurements. The antenna has a 3 dB AR bandwidth of 13.5%, gain is more than 7.5 dBi over the 3 dB AR bandwidth and the 10 dB return-loss bandwidth is 21%. The proposed feed optimization technique is useful for rapid design of circular polarized stacked microstrip antennas.

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.

Compact stub type microstrip bandpass filter using defected ground plane

Usually a defected ground plane structure (DGS) provides only a band-reject response. However, in this work we introduce a simple band-accept circuit element in the DGS and developed a microstrip stub type compact 3-pole bandpass filter (BPF) at 4.2 GHz. The BPF has bandwidth and insertion loss 38% and 0.6 dB respectively. It has better than 25 dB rejection in the stopband up to 12 GHz.

Resonant frequency of uncovered and covered rectangular microstrip patch using modified Wolff model

A new model, called the modified Wolff model (MWM), is proposed to calculate the resonant frequency of a rectangular open microstrip patch, a patch with a dielectric superstrate and a patch inside a shielded enclosure. The model has also been applied to calculate resonant frequencies of higher-order modes. The dependence of resonant frequency on the various parameters and its accuracy are discussed using the MWM. Results obtained from MWM follow very closely the results from various forms of full-wave analysis, and in almost all cases they are within 0.5% of published experimental results for the fundamental mode and within 1.7% for higher-order modes. The method is computationally fast and efficient even on a desktop computer. The method could be used for other patches like circular, hexagonal and equilateral triangle. >

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.

Improved circuit model for DGS based lowpass filter

We report a new and improved circuit model for the defective ground plane (DGS) slot based lowpass filter (LPF) which accounts for losses and mutual coupling between the slots. We also present a Hi-Lo LPF with DGS slots and investigate the impact of their position on improving the performance of the filter.

Wideband High-Gain Circularly Polarized Stacked Microstrip Antennas With an Optimized C-Type Feed and a Short Horn

A new technique is developed to increase the axial ratio (AR) bandwidth of circularly polarized stacked microstrip antennas (CPSMAs) to about 15.0% by optimizing the location of the C-type single feed and a few other parameters. The stacked microstrip antenna with a quasi-planar surface-mounted short horn (SMSH) has achieved 13 dBi gain, 15.5% 3 dB AR bandwidth, 0.37 dB minimum AR and 25.0% impedance bandwidth. The measured gain is more than 11.5 dBic over the impedance bandwidth. The proposed technique simplifies the design of wideband circularly polarized antenna for medium to high gain applications.

Static capacitance of some multilayered microstrip capacitors

A new unified model, the modified Wolff model (MWM) is presented to determine the lumped capacitance of rectangular, circular, hexagonal and triangular patches on the single layer substrate and under the multilayer condition. Effect of the top shield on the lumped capacitance has also been determined. The MWM is the combination of Wolff-Knoppick model, TTL technique and single layer reduction (SLR) technique, The results of MWM have been compared against the results of SDA, FEM, dual integral method and other forms of the variational methods with accuracy between 0.5-5% for most shapes under various conditions. The present model has accuracy of SDA and other rigorous formulations. No single method has been used in the literature to determine the lumped capacitance of patches of several shapes under the multilayer and shielded condition. The MWM is fast even on the desktop computer. Thus, the model is suitable for a unified CAD for the MMIC applications. >

Improving the axial-ratio bandwidth of circularly polarized stacked microstrip antennas and enhancing their gain with short horns

A systematic technique is developed to improve the AR bandwidth of circularly polarized stacked microstrip antennas (CPSMAs) to about 14% by optimizing the location of the feed and a few other parameters. A new C-type single feed is explored for this purposes. Then a CPSMA is integrated with a quasi-planar short horn to enhance its gain. Our results indicate that it is possible to increase the gain by 4.5 dB without compromising the 3 dB axial ratio (AR) bandwidth or the 10 dB return loss bandwidth of the CPSMA. The final design has a gain of 11.5 dBi, 3 dB AR bandwidth of 15.2%, minimum AR of 0.27 dB and a 10 dB return loss bandwidth of 21.5%. The proposed techniques simplify the design of wideband circularly polarized antennas for medium to high gain applications