Radical Shorted Transmission Lines on Silicon Based upon Periodic Metamaterial Structures

Differential transmission lines (DTL) can be synthesized by identical or different periodic structures (PS). These PS can be used not only for matching one circuit to another; also small resonators can be established serving in filters or oscillators. These new DTL - by using the proposed PS - allow characteristic impedances beyond that of classical TL and in addition at much smaller size. It is the first time that DTL structures form a real alternative for applications in MMIC design below 10 GHz.

A viable wide-band circuit model of parallel corrugated differential transmission line is established. By solving for the even- and odd-modes in this structured differential transmission line, the equivalent capacitance, inductance, resistance, and conductance per unit length are calculated, then the characteristic impedances of differential and common signals are obtained. The S-parameters obtained from the equivalent circuit model agree well with the full-wave simulation results with a deviation of only about 0.036 dB in the frequency range of 10 GHz. Experimentally, the characteristic impedances are measured for the differential and common signals using a time domain reflectometer (TDR). The deviation between the experimental and theoretical results was less than 1.05%. Based on the equivalent circuit model, it is feasible to implement this type of structured differential line directly into real circuits.

Interactions beyond nearest neighbors in a periodic structure: Force analysis

The rise of wearable computing and biomedical technologies demands development of flexible and stretchable interconnects. This paper presents the design and characterization of differential stretchable transmission line. The transmission line is embedded in the low cost Polyurethane thin film which has excellent stretchablility and flexibility, and the copper pattern is optimized as a zigzag shape to allow stretch maintaining the mechanical reliability. The electrical characteristics were measured as the line stretches by using 4-port network analyzer with house made calibration kits. Especially, the measurement was made without common ground connections between near-end and far-end VNA ports and differential characteristics are successfully extracted. Measured differential mode characteristic impedance is 94-Ω at the normal length and slightly increased as the line stretches due to the deformation of the line. The insertion loss is 0.035dB/mm at 1-GHz from the beginning and slightly reduced as the line stretches. It is shown that the line can be elongated up to 25% guaranteeing the electrical and mechanical reliability.

In the history of antenna development, periodic structures have been extensively studied and applied. Typically, through the dispersion analysis, the propagation and radiation performances of periodic structures can be predicted. There is no doubt that dispersion relation plays a vital role in periodic structures based antenna designs.
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\nIn this thesis, a systematic study on dispersion engineering of periodic structures and its applications to antenna designs is presented. The unifying goal of this study is to change the antenna properties by manipulating the dispersion relations to meet various design requirements and address the bottleneck problems. In addition, several novel antenna designs with excellent performances are proposed and presented in this thesis.
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\nFirstly, a novel one dimensional multiple periodic (MP) structure is proposed. Different from the conventional periodic structures that have single periodicity, the proposed MP structure increases the periodicity by enclosing different unit cells (UCs) into each periodic element. Through the dispersion analysis, it is found that some new features can be offered by the MP structures. With the increase of the periodicity, the separation distance between the space harmonics are reduced and several new stopbands are opened up. The former feature will lead to excitations of multiple space harmonic modes in a certain frequency range. These new features are proved to be universal for both dispersive and non-dispersive materials. Regarding to each material, the analyses are performed from media and lumped circuit perspectives. The MP structures provide room to manipulate the dispersions. By proper adjusting the geometric parameters, the dispersion relations can be engineered. Furthermore, a general dispersion relation and a general Bragg condition for MP structures are also derived.
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\nSecondly, the proposed theory of MP structures is extended to two new designs of supercell (SC) based dual-beam leaky-wave antennas. By proper engineering the dispersion relations, two space harmonic modes (m= -1 and m= -2) are excited to form two radiation beams. The two designs improve the link quality of the communication system and address the problems that are dominated by the intrinsic characteristics of the links, such as the multipath effect and the mutual interference. The first antenna is based on the microstrip lines and operates in the microwave region. It validates the feasibility of the proposed theory. On the other hand, another antenna is realized by the dielectric grating and works in the millimeter-wave (MMW) region (60-GHz). It employs a symmetrically configured SC and have better radiation performance. Both two designs can realize beam steering in the same clockwise or anti-clockwise direction against the frequency, which is rarely discussed in the previous literatures. They are of very simple structures that are easy for manufactures.
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\nThirdly, a new collimated surface-wave (SW) excited high impedance surface (HIS) leaky-wave antenna is proposed. This antenna realizes a transformation from TM0 SW mode to m= -1 leaky-wave mode. A novel substrate-integrated waveguide (SIW) based planar parabolic reflector is designed as the SW launcher (SWL). Different from the previous literatures that the SWs propagate in a cylindric wave fashion, the proposed SWL can efficiently excite collimated SWs. On the other hand, the dispersion relation is engineered by introducing an additional secondary slit on the HIS to solve the bottleneck problem, open-stopband effect. Through proper design, the open-stopband effect is suppressed successfully in the design and implementation.
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\nFinally, two antenna designs that can operate in the near-field region by using the inductive coupling principle are proposed for radio frequency identification (RFID) applications. The first antenna works in dual frequency bands (HF/UHF bands) that have nearly 70 times frequency difference. The design is challenged by the impaired UHF bandwidth due to existence of the spiral coil that operates in the HF band. A novel meander lines based diagonal symmetric structure is designed to support multiple resonance modes to expand the impedance bandwidth under the large inductive circumstance of the coil. On the other hand, the second design starts from a segmented loop antenna that behaves as a magnetic dipole and has better performance than coil. In order to meet the requirement of compactness of the RFID tag antenna, the dispersion relation is engineered by adopting multiple identical radiators. The zeroth-order resonance frequency is reduced with same dimension by this method. As a result, the physical dimension of the antenna can be further reduced at the desired frequency. Through the dispersion engineering, the antenna miniaturization is realized.
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\nIn summary, this thesis contributes to 1) the development of novel periodic structures and their relevant theory for the new features, 2) addressing practical issues by engineering the dispersion relations and 3) providing a new procedure of using the dispersion engineering for antenna designs.

Recent work by Intel [1,2] has shown that it is possible to reduce the loss of transmission lines through innovative routing. The “vertical trench” proposed in Intel's work [1,2] showed a 20% reduction in the differential insertion loss. In this work a detailed discussion on the reasons why this novel routing approach can reduce the loss of the differential lines as well as analysis on the design variables of and their effects on the performance of a differential transmission line employing the vertical trench is undertaken. It is also shown through simulation that similar improvements in the differential insertion loss can be obtained through simply increasing the thickness of the of metal for the differential pair.

In recent years, with improvement in the speed of digital equipment, differential transmission lines are used abundantly in the circuit substrate. However, by using the differential lines, the number of signal wires doubles as compared with the conventional single-ended. In this paper, the authors investigated the cross-sectional shape of the trace of printed circuit board, which can reduce the cross-talk interference or improve the wiring density. The three patterns of the cross-sectional shape of the trace are examined in this paper. The one is conventional rectangular shape, which the width of the trace is longer than the thickness (low aspect ratio), and the second pattern is a shape of high aspect ratio (the thickness of the trace is longer than the width), and the last trace pattern is a shape of square. The characteristic impedances of the all three trace patterns are designed to be 100 ohm in differential mode. Also, the cross sectional area is arranged to be same among the three trace patterns in order to make the transmission loss conditions are same. As a result, we discovered that the amount of cross talks become minimum, when the cross sectional form of the trace is square. In verification of this idea, the authors simulated for three patterns of cross-sectional shapes of signal traces by the HSPICE of circuit analysis software and the HFSS of three-dimensional electromagnetic-field analysis software.

In a differential transmission line, a large common-mode radiation is excited due to its asymmetry. In this paper, the imbalance difference model, which was proposed by the authors for estimation of common-mode radiation, is extended to apply to the differential signaling systems. The authors focus on a differential transmission line with asymmetric property, which consists of an adjacent return plane and two signal lines which are placed close to an edge of the return plane. Three orthogonal transmission modes, a normal mode, a primary common mode and a secondary common mode, are defined. Among these transmission modes, the secondary common mode is dominant in radiation, and a mechanism of the secondary common-mode generation is explained. The radiated emission which was calculated using the imbalance difference model was in good agreement with that obtained by full wave calculation.

In this paper, the problem of using guard traces for reducing crosstalk between differential transmission line pairs is investigated, both experimentally and by full-wave electromagnetic (EM) simulations. Different cases of differential lines crosstalk are treated with and without guard trace separation between the differential line pairs. Coated microstrip printed circuit board test structures including thru-reflect-line calibration standards are designed and fabricated on a high frequency laminate material, allowing direct measurement of crosstalk between adjacent differential line pairs in the absence and in the presence of guard traces stitched with vias of regular spacing. The test structures are characterized with mixed-mode scattering parameters using a physical layer test system. Different configurations (of differential line pairs) without guard trace, with floating guard traces (which are terminated and nonterminated) and with a solid guard trace separation are investigated using a High Frequency Structure Simulator (a commercial full-wave 3-D EM simulation tool). The experimental data are compared with the simulation results, and some conclusions and guidelines on the effect of guard traces for alleviating crosstalk between differential transmission lines are presented

This paper presents an area-efficient differential distributed amplifier using differential coupled inductors. The artificial transmission lines of the proposed distributed amplifier are modeled as differential transmission lines, and thus, it can be easily designed compared with other area reduction techniques. The dimensions of the coupled inductors have been optimized using a gradient descent algorithm with a scalable model of the coupled inductors. The proposed amplifier was designed using 1P5M 180 nm standard CMOS technology. Post-layout simulation results demonstrated a gain of 6.9 dB and a bandwidth of 20.2 GHz with 4.9 ps Nyquist group delay variation. A core area of the proposed amplifier was 0.28 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which was the smallest value compared with previous works using similar processes.

Modern trends in electronics development require the design of compact and high-performance devices operating under high levels of electromagnetic interference (EMI). A promising solution for ensuring the electromagnetic compatibility (EMC) of differential transmission lines (DTLs) is the use of electromagnetic absorbers (EAs). However, the influence of the absorber thickness on the time-domain and frequency-domain characteristics of integrated DTLs remains insufficiently studied. This study employs modeling methods implemented in the software tools TUSUR.EMC and COMSOL Multiphysics. A DTL on a GaAs substrate is considered, with the EA thickness varied from 0 to 20 µm. The investigation includes an analysis of transmission and reflection coefficients, signal integrity, and propagation delays. The research aims to determine the optimal EA thickness that provides maximum interference suppression while minimizing its impact on the useful signal. The results show that an EA with a thickness of 8 µm reduces interference amplitude by a factor of 1.4, increases signal arrival time by a factor of 1.15, and decreases the level of reflected signals in the stopband to minus 13.16 dB. However, the passband width decreases from 2.41 GHz (at H = 0) to 1.03 GHz (at H = 20 µm). Thus, the use of an EA with an optimal thickness significantly improves the EMC of integrated DTLs. The obtained results can be utilized in the design of high-frequency devices with enhanced immunity to interference.

Measurements of the distribution of electric field intensity along a periodic radiating structure consisting of a dipole array coupled to a balanced transmission line reveal a standing‐wave pattern that is formed at the driven end of the structure. We propose that this standing wave is formed by the interference of two normal modes of the coupled structure. These modes are found to possess conjugate wave functions exp [−αx±jβx], and to carry energy in opposite directions on the transmission line. They are identified with transmitting and receiving modes of the infinite, periodic structure; both are excited on a finite model to satisfy boundary conditions on both the transmission line and the dipole array at its driven end.These conjugate normal modes arise from coupling of the TEM mode of the unloaded transmission line with the complex, radiating mode of an undriven, periodic array of dipoles. The determinantal equation of the coupled array can be cast in a form that displays the mode coupling.

Peierls transition that modifies electronic band structure has attracted intensive attention in solid state physics. In the present work, we report that a photonic analog of Peierls transition has been observed in a 1-D triangular metal diaphragm array, where the photonic bandgap structures have been designed at will by adjusting periodically metal diaphragm positions. It is shown by the numerical analysis that the transmission and radiation effect of the present periodic metal structure designed through the Peierls transition rule exhibits the behavior significantly different from an original periodic structure with each unit cell containing a metal diaphragm. The near- and far-field measurement results are in good agreement with our theoretical simulation. The present effect of photonic Peierls transition can serve as a working mechanism for designing new types of guided wave devices. It can be seen that the photonic Peierls transition would be one of the simplest ways for modifying the transport characteristics of electromagnetic waves in periodic structures.

A methodology for the harmonic-balance analysis and design of rotary-traveling wave oscillator is presented. Two different implementations are compared. The first one is the standard configuration based on a distributed transmission lines. The second one is a new configuration based on a differential nonlinear transmission line (NLTL), which enables the generation of square waveforms with reduced number of stages, while still maintaining the capability to produce multiphase signals. The possible coexistence of oscillation modes is investigated with a detailed bifurcation analysis versus practical parameters such as the device bias voltage. The phase-noise spectrum is predicted from the variance of the common phase deviation. The parameters that determine this variance are identified with the conversion-matrix approach. The two prototypes, based on a distributed transmission line and a differential NLTL, have been manufactured and characterized experimentally, obtaining very good agreement between simulations and measurements.

In this work, absorption properties of spatially disordered metamaterials are analysed using numerical simulations. For this purpose, position randomness is introduced in a supercell, which transforms a periodic metamaterial structure into a random metamaterial structure, where the constituent resonators are interacting with each other. It is demonstrated that the disorder can be used to enhance the absorption bandwidth. This enhancement is obtained due to the coupling among the nearby resonators, which results in broadening of collective resonance. The proposed disordered metamaterial absorbers also exhibit polarisation-insensitivity and have wide-band absorption for both normal and oblique incidences, which makes them a promising candidate for a variety of applications.