Karumudi Rambabu

Coupling-Matrix Design of Dual and Triple Passband Filters

The concept of the conventional coupling matrix is extended to include designs of dual- and triple-band filters. The multiband response is created by either placing transmission zeros within the bandwidth of a wideband filter or using higher order resonances. Realizable topologies both in planar and waveguide technologies can be imposed and associated coupling coefficients enforced during optimization. The design process is verified by measurements and comparison with results of commercially available field solvers

Design of multiple-stopband filters for interference suppression in UWB applications

A design of multiple-stopband filters is presented for the suppression of interfering signals in UWB applications. Since possible interferers can be located at fixed frequencies or within a defined frequency band, the design of both fixed and tunable narrow stopband filter sections is addressed. For multiple fixed stopband filters, bent resonators, coupled to the main line, are introduced in order to more effectively suppress harmonics. A new tunable tapped stopband section is proposed, which allows the simultaneous control of stopband frequency and bandwidth. The final multiple-stopband design combines fixed and tunable sections and simultaneously suppresses interferences from global system for mobile communication, wireless local area network, worldwide interoperability for microwave access, and industrial-scientific-medical applications. Measurements verify the design process

Buried Object Characterization Using Ultra-Wideband Ground Penetrating Radar

In this paper, a method to characterize buried nonmagnetic objects in ground using ultra-wideband (UWB) ground penetrating radar (GPR) is proposed. In this method, UWB pulses are radiated by the radar, while scattered signals from the ground with the buried object are received. The received signals are then post-processed to estimate the depth, thickness, and electrical properties of the buried object. A constant depth and thickness is enforced at all frequencies while the signals are processed to extract the buried object characteristics, resulting in more accurate estimations and reduced processing time. In addition, path loss due to the close proximity of the radar to the ground is compensated analytically. The applicability of the proposed method is validated with several planar objects and a boulder that we typically encounter in the construction industry. The proposed method can achieve sufficient reliability in estimating the permittivity of buried objects for the purpose of material identification. Incorporating the proposed method into the GPRs enhances their existing imaging ability by adding material identification capability.

Estimation of Antenna Effect on Ultra-Wideband Pulse Shape in Transmission and Reception

This paper presents an analysis of the antenna effect on ultra-wideband (UWB) pulse shape in transmission and reception. This analysis consists of a derivation of the impulse response for frequently used UWB antennas like the ridged horn, transverse electromagnetic horn, and bicone in the transmitting and receiving modes. An analytical/semianalytical expression for the received pulse has been derived. Frequency-limited gain of the transmitting and receiving antennas has been accounted for in the estimation of the received pulse. To demonstrate the antenna effect on a UWB pulse, various antenna combinations have been considered to transmit and receive different Gaussian pulses. A combination of transmitting and receiving antennas has been proposed for faithful reception of the transmitted pulse. This paper also studies the pulse shape and amplitude due to oblique incidence of the pulse on a receiving antenna. Measurements have been presented to support the proposed analysis, and they show good agreement with the estimated received pulses.

Design of Compact F-Shaped Slot Triple-Band Antenna for WLAN/WiMAX Applications

This communication presents a small, low-profile planar triple-band microstrip antenna for WLAN/WiMAX applications. The goal of this communication is to combine WLAN and WiMAX communication standards simultaneously into a single device by designing a single antenna that can excite triple-band operation. The designed antenna has a compact size of

Design of reactive parasitic elements in electronic beam steering arrays

19 \times 25\;\text{mm}^{2}

Design of Koch Fractal Circularly Polarized Antenna for Handheld UHF RFID Reader Applications

(

Characteristics of Ultra-Wideband Pulse Scattered From Metal Planar Objects

0.152 \lambda_{0}\;\times 0.2 \lambda_{0}

Time Domain Characterization of Circularly Polarized Ultrawideband Array

). The proposed antenna consists of F-shaped slot radiators and a defected ground plane. Since only two F-shaped slots are etched on either sides of the radiator for triple-band operation, the radiator is very compact in size and simple in structure. The antenna shows three distinct bands I from 2.0 to 2.76, II from 3.04 to 4.0, and III from 5.2 to 6.0 GHz, which covers entire WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.5/3.5/5.5) bands. To validate the proposed design, an experimental prototype has been fabricated and tested. Thus, the simulation results along with the measurements show that the antenna can simultaneously operate over WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.5/3.5/5.5 GHz) frequency bands.

Circularly Polarized Ultra-Wideband Radar System for Vital Signs Monitoring

A new approach for the design of electronic beam steering arrays with reactive parasitic elements is introduced. The method is demonstrated at the example of a circular array formed by capacitively tuned monopoles. The related capacitances are determined straightforwardly and without any need for optimization techniques. The resulting beams are rotatable and maintain their gain and beamwidth within tight margins. Comparisons with NEC2 verify the pattern calculation.