Rakhesh Singh Kshetrimayum

A Printed 2.4 GHz/5.8 GHz Dual-Band Monopole Antenna with a Protruding Stub in the Ground Plane for WLAN and RFID Applications

The design of a simple microstrip fed folded strip monopole antenna (FSMA) with a protruding stub in the ground plane for the application in WLAN and RFID is presented. The antenna has two resonant paths, one in the radiating element (folded strip) and the other in the protruding stub of the ground plane. It supports two resonances at 2.4 GHz and 5.81 GHz, which are the center frequencies of WLAN and RFID. Effectively consistent radiation pattern and large percentage bandwidth have been observed. The measured percentage fractional bandwidth at 2.4 GHz (2.05 GHz to 2.86 GHz) is 32.99, and the percentage fractional bandwidth at 5.81 GHz (5.55 GHz to 6.14GHz) is 10.11. The proposed antenna is simple and compact in size, providing broadband impedance matching, consistent radiation pattern and appropriate gain characteristics in the WLAN and RFID frequency regions.

An introduction to UWB communication systems

Ultra-wideband (UWB) wireless communication is a revolutionary technology for transmitting large amounts of digital data over a wide frequency spectrum using short-pulse, low powered radio signals. UWB commonly refers to a signal or system that either has a large relative bandwidth (BW) that exceeds 20% or a large absolute bandwidth of more than 500 MHz. A 14 February 2002 report and order by the federal communications commission (FCC) authorizes the unlicensed use of UWB in 3.1--10.6 GHz. This is intended to provide an efficient use of scarce radio bandwidth while enabling both high data rate personal area network (PAN) wireless connectivity and longer-range, low data rate applications as well as radar and imaging systems.

SAR Reduction in Human Head from Mobile Phone Radiation using Single Negative Metamaterials

In this paper, we use single negative metamaterials to reduce the electromagnetic interaction between the mobile phone and human head. The specific absorption rate (SAR) in the head can be reduced by placing the metamaterials between the antenna and the head. We design the single negative metamaterials from periodic arrangement of split ring resonators (SRRs), spiral resonators (SRs) and open split ring resonators (OSRRs). By properly designing structural parameters of SRRs, the effective medium parameter can be trade negative around 900 MHz and 1800 MHz bands. The design procedure and principle operation of resonators are explained. The performance and size comparison of resonators will be described. Numerical results of the SAR values in the human head with the presence of resonators exhibit SAR reduction. These results can provide useful information in designing safety mobile communication equipments compliant.

Guided-wave characteristics of waveguide based periodic structures loaded with various FSS strip layers

In this paper, frequency-dependent guided-wave characteristics of waveguide based periodic structures loaded with transversal strip layers of frequency selective surfaces (FSS) are extensively studied in terms of per-unit-length transmission parameters, i.e., complex propagation constant and complex wave impedance. Such a periodic structure with various FSS strip layers are in theory characterized using the hybrid method of moments (MoM)-immittance approach so as to derive these two per-unit-length parameters over a wide frequency range. At first, the extracted phase constant of a simple periodic waveguide, loaded with rectangular patch layer, is compared with the available analytical results, thus validating the approach utilized here. Next, the three novel periodic waveguides, loaded with plus, square loop and Jerusalem cross FSS strip layers, are investigated. It is observed that there is slow-wave behavior in the lower passband for the first two whereas the third one exhibits both fast-wave and slow-wave propagation behaviors in the lower passband. Besides, the third one shows the attractive backward wave propagation within the partial passband, thus introducing a novel waveguide-based artificial negative refractive index metamaterial (NRIM).

Harmonic Suppression of Parallel Coupled Microstrip Line Bandpass Filter Using CSRR

Bandstop filter (BSF) is first constructed using open stubs and spurline. The stop bandwidth of this conventional structure is further increased by placing a complementary split ring resonator (CSRR) exactly below the 50Ω microstrip line. By embedding this BSF with a wide rejection band in the input port of the PCML bandpass filter, unwanted passbands of bandpass filter is eliminated. To demonstrate this, we have designed, fabricated and tested a first order Chebyshev bandpass filter centered at 0.9GHz with 10% fractional bandwidth (FBW). This bandpass filter is cascaded with the newly proposed BSF. Simulation and measured results shows a harmonic rejection upto 5f0 with more than 20 dB rejection level.

A wide-band monopole antenna in combination with a UWB microwave band-pass filter for application in UWB communication system

A filter-antenna configuration for the application for UWB communication system is presented. Firstly, a microstrip transmission line fed monopole antenna for the wide-band (2.65 GHz-8.52 GHz) communication system is designed and Its performance is verified. Secondly, in the place of microstrip transmission line feeding, a planar UWB microwave filter is used and the performance (3.65 GHz-10.16 GHz) of the new filter-antenna configuration is noted. The new filter-antenna configuration considerably improves the antenna performance and wide-band antenna becomes the UWB antenna after the insertion of the UWB microwave filter in place of microstrip-line feeding technique. Hence, the UWB antenna can be used as the wide-band impedance matching circuit to enhance the performance of the antenna in the passband. Apart from this there is improvement in the out-of-band performance. The proposed UWB filter-WB antenna configuration is simple and compact in size providing broadband impedance matching, and consistent radiation pattern within the UWB frequency range.

Robust Time and Frequency Synchronization in OFDM based 802.11a WLAN systems

In this paper, robust and efficient time and frequency synchronization technique suitable for IEEE 802.11a wireless LAN system is proposed. The proposed method performs OFDM symbol boundary detection and frequency offset estimation using correlation techniques. The conjugate property of long preamble is used to reduce the computational complexity. In this proposed method, coarse time and fine frequency offset are estimated jointly and the frequency offset is estimated accurately before fine time estimation

A printed 2.4 GHz/5.8 GHz dual-band monopole antenna for WLAN and RFID applications with a protruding stub in the ground plane

Design of a simple microstrip fed folded strip monopole antenna with a protruding stub in the ground plane for the application in the WLAN and RFID is presented. The antenna has two resonant paths, one in the radiating element (folded strip) and other in the protruding stub of the ground plane, supports two resonances at 2.4 GHz and 5.81 GHz, which are the center frequencies of the WLAN and RFID. Effectively consistent radiation pattern and large percentage bandwidth has been observed. The percentage bandwidth at 2.4 GHz (2.06 GHz to 2.82 GHz) is 31.14 and the percentage bandwidth at 5.81 GHz (5.57 GHz to 6.08 GHz) is 8.75.The proposed antenna is simple and compact in size providing broadband impedance matching, consistent radiation pattern and appropriate gain characteristics in the RFID frequency range.

Novel UWB printed monopole antenna with triangular tapered feed lines

A novel ultra-broadband printed monopole antenna with 10dB return loss bandwidth from 2.1-21.5GHz is proposed. This printed monopole antenna is constructed using cross-slotted modified circular patch with etched ground plane. This UWB printed monopole antenna is microstrip-fed with a triangular tapered input line for broadband matching.

A printed F-shaped dual-band monopole antenna for RFID and WLAN applications

Design of a simple microstrip fed monopole patch antenna for the radio frequency identification (RFID) and wireless local area network (WLAN) is presented. The antenna has two different resonant paths (forming an F-shaped structure), supports two resonances at around 2.44 GHz and 5.18 GHz, which are reserved for RFID and WLAN applications. Effectively consistent radiation pattern and large impedance bandwidth has been observed. Impedance bandwidth for −10 dB return loss in the 2.44 GHz and 5.18 GHz center frequency reaches 0.65 GHz (2.12 GHz to 2.77 GHz) and 0.59 GHz (4.91 GHz to 5.50 GHz) respectively. The proposed antenna is simple and compact in size providing broadband impedance matching, consistent radiation pattern and appropriate gain characteristics in the RFID and WLAN frequency range.