The analysis and design of passive broadband negative group delay (NGD) transmission line phase shifters is presented. By extending the metamaterial transmission line concept to include loss, a NGD unit cell is proposed. Phase shifters are supplemented with NGD unit cells to produce a flattened phase response significantly increasing phase bandwidths. The design methodology of a NGD phase shifter is presented with consideration of nominal phase, frequency, impedance, maximum insertion loss and bandwidth. The relation between gain, bandwidth and group delay signifies a fundamental design limitation and tradeoff. A significant application of NGD phase shifters for removing beam squint in series fed antenna arrays is discussed. Several NGD phase shifters are fabricated and experimentally verified in the UHF band upwards of 1 GHz using planar microstrip transmission lines loaded with passive surface mount RF components with both positive and negative phase shifts.

The analysis and design of passive broadband negative group delay (NGD) transmission line phase shifters is presented. By extending the metamaterial transmission line concept to include loss, a NGD unit cell is proposed. Phase shifters are supplemented with NGD unit cells to produce a flattened phase response significantly increasing phase bandwidths. The design methodology of a NGD phase shifter is presented with consideration of nominal phase, frequency, impedance, maximum insertion loss and bandwidth. The relation between gain, bandwidth and group delay signifies a fundamental design limitation and tradeoff. A significant application of NGD phase shifters for removing beam squint in series fed antenna arrays is discussed. Several NGD phase shifters are fabricated and experimentally verified in the UHF band upwards of 1 GHz using planar microstrip transmission lines loaded with passive surface mount RF components with both positive and negative phase shifts.

Owing to the need of high-directivity radiation in fix-point communication, this thesis designs the metamaterial with 4-fold rotational symmetric unitcells. Using their nearing-zero refractive index along two polarizations, we can get gain-enhanced antenna radomes and place them above dual- and circular-polarized antenna to verify our idea. It is known that the group delay variation in a communication system causes the degradation of symbol error rate, and positive group delay (GD) causes delay in signal propagation. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the GD of metamaterial equivalent circuit caused by poles and zeros, we design a novel NGD bandpass circuit. Furthermore, this thesis develops graphic method for group delay investigatiion and study the relationship between NGD, loss and gain in order to simplify the design of GD compensation circuit.

In a communication system, the group delay variation (GDV) causes the distortion of signal and the degradation of symbol error rate. Usually, the compensation of group delay (GD) utilizing positive group delay (PGD) results in further propagation delay. Therefore, this research studies the negative group delay (NGD) behavior of metamaterial. Through analyzing the effects on GD caused by poles and zeros of circuit, the group delay circuit capable of switching between NGD and PGD is presented. Further, adjustable negative group delay circuits (NGDCs) are designed based on the concept of poles and zero. The NGD generated by NGDC is used to achieve the equalization of GD and recover the distorted signal in time domain. Additionally, owing to the limited frequency band of communication, a filter with high selectivity is required to utilize the available bandwidth. The character of left-handed metamaterial is applied to the design of filter for reducing the size and cost of traditional microstrip line filters with high selectivity. Under the balanced condition, composite right/left-handed (CRLH) transmission line behaves right- and left- handed characteristics in different frequency bands. Thus, a coplanar waveguide (CPW) filter with high selectivity, size reduction and low cost is presented utilizing such a CRLH structure.

Although it has been well established that abnormal group delay is a real physical phenomenon and is not in violation of Einstein causality, there has been little investigation into whether or not such abnormal behaviour can be used to reduce signal latency in practical communication systems in the presence of noise. In this thesis, we use time-varying probability of error to determine if abnormal group delay “channels” can offer reduced signal latency. Since the detection system plays a critical role in the analysis, three important detection systems are considered: the correlation, matched filter and envelope detection systems. Our analysis shows that for both spatially negligible microelectronic systems and spatially extended microwave systems, negative group delay “channels” offer reduced signal latency as compared to conventional “channels”. The results presented in the thesis can be used to design a new generation of electronic and microwave interconnects with reduced or eliminated signal latency.

Although it has been well established that abnormal group delay is a real physical phenomenon and is not in violation of Einstein causality, there has been little investigation into whether or not such abnormal behaviour can be used to reduce signal latency in practical communication systems in the presence of noise. In this thesis, we use time-varying probability of error to determine if abnormal group delay “channels” can offer reduced signal latency. Since the detection system plays a critical role in the analysis, three important detection systems are considered: the correlation, matched filter and envelope detection systems. Our analysis shows that for both spatially negligible microelectronic systems and spatially extended microwave systems, negative group delay “channels” offer reduced signal latency as compared to conventional “channels”. The results presented in the thesis can be used to design a new generation of electronic and microwave interconnects with reduced or eliminated signal latency.

The electromagnetic coupling of a microstrip transmission line (MS-TL) to a metamaterial backward wave Negative-Refractive-Index transmission line (NRI-TL) is the primary investigation of this dissertation. The coupling of forward waves in the MS-TL to the backward waves in the NRI-TL results in the formation of complex modes, characterized by simultaneous phase progression and attenuation along the lossless lines. Through network-theoretic considerations, we investigate the properties of these modes in the complex-frequency plane of the Laplace domain to help unravel the confusion that has existed in the literature regarding the independent excitation of a pair of conjugate complex modes. We show that it is possible to arbitrarily suppress one of the modes over a finite bandwidth and completely eliminate it at a discrete set of frequencies using proper source and load impedances. Hence we use conjugate modes with independent amplitudes in our eigenmode expansion when we analyse various coupling configurations between the two types of lines (MS/NRI-TL coupler). We derive approximate closed-form expression for the scattering parameters of the MS/NRI-TL coupler and these are complemented by design charts that allow the synthesis of a wide range of specifications. Moreover, these expressions reveal that such couplers allow for arbitrary backward coupling levels along with very high-isolation when they are made half a guided wavelength long. The MS/NRI-TL coupler offers some interesting applications which we highlight through the design and testing of a 3-dB power splitter, a high-directivity signal monitor and a compact corporate power divider. We have included design, simulation and experimental data for the fabricated prototypes exhibiting good agreement and thereby justifying the theory that has been developed in this work to explain the coupling between a right-handed MS-TL and a left-handed NRI-TL.

The electromagnetic coupling of a microstrip transmission line (MS-TL) to a metamaterial backward wave Negative-Refractive-Index transmission line (NRI-TL) is the primary investigation of this dissertation. The coupling of forward waves in the MS-TL to the backward waves in the NRI-TL results in the formation of complex modes, characterized by simultaneous phase progression and attenuation along the lossless lines. Through network-theoretic considerations, we investigate the properties of these modes in the complex-frequency plane of the Laplace domain to help unravel the confusion that has existed in the literature regarding the independent excitation of a pair of conjugate complex modes. We show that it is possible to arbitrarily suppress one of the modes over a finite bandwidth and completely eliminate it at a discrete set of frequencies using proper source and load impedances. Hence we use conjugate modes with independent amplitudes in our eigenmode expansion when we analyse various coupling configurations between the two types of lines (MS/NRI-TL coupler). We derive approximate closed-form expression for the scattering parameters of the MS/NRI-TL coupler and these are complemented by design charts that allow the synthesis of a wide range of specifications. Moreover, these expressions reveal that such couplers allow for arbitrary backward coupling levels along with very high-isolation when they are made half a guided wavelength long. The MS/NRI-TL coupler offers some interesting applications which we highlight through the design and testing of a 3-dB power splitter, a high-directivity signal monitor and a compact corporate power divider. We have included design, simulation and experimental data for the fabricated prototypes exhibiting good agreement and thereby justifying the theory that has been developed in this work to explain the coupling between a right-handed MS-TL and a left-handed NRI-TL.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.

Abnormal electromagnetic wave propagation characterized by negative group velocity and consequently negative group delay (NGD) has been observed in certain materials as well as in artificially built structures. Within finite frequency intervals where an NGD phenomenon is observed, higher frequency components of the applied waveform are propagated with phase advancement, not delay, relative to the lower frequency components. These media have found use in many applications that require positive delay compensation and an engineered phase characteristic, such as eliminating phase variation with frequency in phase shifters, beam-squint minimization in phased array antenna systems, size reduction of feed-forward amplifiers and others. The three principal questions this thesis addresses are: can a generic formulation for artificial NGD structures based on electric circuit resonators be developed; is it possible to derive a quantitative functional relationship (asymptotic limit) between the maximum achievable NGD and the identified trade-off quantity (out-of-band gain); and, can a microwave circuit exhibiting a fully loss-compensated NGD propagation in both directions be designed and implemented? A generic frequency-domain formulation of artificial NGD structures based on electric circuit resonators is developed and characterized by three parameters, namely center frequency, bandwidth and the out-of-band gain. The developed formulation is validated through several topologies reported in the literature. The trade-off relationship between the achievable NGD on one hand, and the out-of-band gain on the other, is identified. The out-of-band gain is shown to be proportional to transient amplitudes when waveforms with defined “turn on/off” times are propagated through an NGD medium. An asymptotic limit for achievable NGD as a function of the out-of-band gain is derived for multi-stage resonator-based NGD circuits as well as for an optimally engineered linear causal NGD medium. Passive NGD media exhibit loss which can be compensated for via active elements. However, active elements are unilateral in nature and therefore do not allow propagation in both directions. A bilateral gain-compensated circuit is designed and implemented, which overcomes this problem by employing a dual-amplifier configuration while preserving the overall circuit stability.