PERFORMANCE ENHANCEMENT OF MICROWAVE DEVICES USING METAMATERIAL BASED SUB-WAVELENGTH RESONATORS
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Metamaterials are new artificial materials with unusual electromagnetic properties, not commonly found in nature. All natural materials have positive magnetic permeability and electric permittivity. In contrast, in metamaterials they are negative. Using these exotic properties, several high performance microwave devices/components have been developed by many researchers across the globe. In our study, many size miniaturized and per- formance enhanced planar microwave devices/circuits employing metamaterial based sub- wavelength resonators viz. complementary split ring resonator (CSRR), open slot split ring resonator (OSSRR) and open complementary split ring resonator (OCSRR) were designed, fabricated, tested and are listed below. * Various wide bandstop filters using complementary split ring resonator (CSRR), open stub and spurline are designed and used for harmonic suppression of lowpass and bandpass filters.* A complementary single split ring resonator (CSSRR) is used to develop a band notched ultra wideband (UWB) bandpass filter, designed using ground plane aperture technique. To filter out the undesired wireless local area network (WLAN) signals, a CSSRR is placed under the coupled lines of bandpass filter. Thus, any unwanted signals (i.e., IEEE 802.11a frequency band) that may interfere with the desired UWB frequency range are effectively removed. * An OSSRR is introduced for the first time to realize a composite right/left handed (CRLH) transmission line (TL) structure in microstrip technology. The CRLH line is synthesized by etching OSSRR in the ground plane and interdigital capacitor in the microstrip line. The proposed method of realization of CRLH TL results in size reduction compared with the conventional CSRR based TL. *A compact lowpass filter is constructed using periodic array of OSSRR and open stubs. Open stubs are attached on both sides of the OSSRR. The proposed filter has sharp rejection characteristics and compact size compared with the conventional stepped impedance lowpass filter. * A compact, wide fractional bandwidth bandpass filter, using a new resonator OSSRR and compact microstrip resonating cell (CMRC) is presented. The designed BPF has a wide fractional bandwidth of 74%, sharp passband to stopband transition, and low passband insertion loss of less than 1 dB * Design of a compact lowpass filter using an OCSRR and an open stub is presented. The proposed lowpass filter consists of two OCSRR connected in series with the open stubs attached on either side. At the 3 dB cut-off frequency of 1 GHz, the proposed filter offers a sharp and wide rejection bandwidth of more than 20 dB, up to six times the cut-off frequency. * The size of the lowpass filter designed using OCSRR and open stub is further reduced by replacing the open stubs with the defected ground structures. A size miniaturized lowpass filter is designed using two cell OCSRRs connected in series and dumbbell shaped DGS placed below the OCSRRs. The proposed filter size is very small and its rejection band is up to ten times the cut-off frequency. * By utilizing the slow-wave effect of OCSRR, size miniaturized and third harmonic suppressed T-junction power divider is designed. The proposed power divider is 47% smaller than the conventional design. * A compact and harmonic suppressed 1800 ring hybrid is proposed using OCSRR. It of- fers third harmonic............
Supervisor: Rakesh Singh
ELECTRONICS AND ELECTRICAL ENGINEERING