Ching-Kuang C. Tzuang

Synthetic quasi-TEM meandered transmission lines for compacted microwave integrated circuits

This paper presents a two-dimensional transmission line (2-D TL) that supports quasi-TEM propagation mode and reduces problems associated with compacted meandering of microstrip (MS) on propagation constants and the characteristic impedances commonly observed in conventional one-dimensional MSs. The proposed 2-D TL comprises two layers of metallic surfaces on either side of a dielectric substrate. The top metal surface is a meandered connection of a unit cell with a central patch and connecting arms. The bottom surface is a meshed 2-D periodical ground plane, whose etched portion complements the patch portion of the top surface, forming a complementary-conducting-strip (CCS) TL, enabling a combination of an MS and MS with the tuning septa in a unit cell. Both theoretical and experimental investigations of the CCS TL agree well and demonstrate that it is much less susceptible to the effects of meanderings on the propagation constant and characteristic impedance than an MS for the same meandered pattern. Two design examples are presented to demonstrate the potential for a CCS TL for miniaturizing microwave passive circuits with minimal losses. The first example involves a 5.4-GHz CCS four-port rat-race hybrid realized in RO4003 and reduces the area of original MS design by 87%. The second example illustrates the applicability of a CCS TL to a monolithic RF integrated circuit using a first-pass design of a 5.2-GHz CMOS oscillator incorporating a CCS TL as a resonator with an area totaling 500/spl times/600 /spl mu/m/sup 2/ including pads base on Taiwan Semiconductor Manufacturing Companys 0.25-/spl mu/m 1P5M CMOS process techniques.

Transmission characteristics of finite-width conductor-backed coplanar waveguide

This paper presents theoretical and experimental results for a finite-width conductor-backed coplanar waveguide (FW-CBCPW). The guiding characteristics of FW-CBCPW are investigated first by the rigorous method of mode matching. An FW-CBCPW through line is then placed within a test fixture commonly used in laboratories, and the scattering parameters of the through line are obtained theoretically by approximating the FW-CBCPW as a simple system of coupled transmission lines. Experimental results are shown to agree very well with the theoretical ones. In particular, the anomalous behavior observed in the transmission characteristic of the through line is related to the resonant phenomenon of the terminated side planes which are short-circuited at both input and output ends due to the test fixture. Finally, a technique of mode suppression in the side-plane regions is suggested for the improvement of signal transmission over a broad band of frequency spectrum. The effects of extra higher order modes on the transmission characteristics at high frequencies are also discussed. >

Oscillator-type active-integrated antenna: the leaky-mode approach

This paper describes basic research carried out to design a microwave source module employing the concept of an active-integrated leaky-mode antenna. The novel active-antenna source module utilizes a microstrip as the radiating element while adopting uniplanar technology for the active circuit design. The microstrip is operated in the first higher order odd mode, which is a leaky mode, and excited by a proximity-coupled center-fed slotline on the same surface of the uniplanar microwave-integrated circuit. The measured performance of an X-band transmission-type injection-locked active-integrated antenna source module demonstrated that such a design approach was suitable for linear array integration for quasi-optical power combining. The harmonic-balance (HB) analysis of the proposed active-integrated antenna agrees with the measurements in both free-running frequency and power level. The measured radiation patterns of the active-integrated antenna also agree well with the theoretical predictions.

Finite-Element Analysis of Slow-Wave Schottky Contact Printed Lines

Extensive finite-element analyses on MMIC slow-wave structures with both Iocalized and layered models are presented. Good agreement is achieved between the data presented here and other theoretical results and experiments. Higher order elements that improve accuracy are discussed. The comparative studies for Schottky contact microstrip and coplanar waveguide with Iocalized and layered models are presented. Potential applications of the Iocalized models to more general and practical slow-wave circuits are also discussed.

Resonant phenomena in conductor-backed coplanar waveguides (CBCPW's)

The resonant phenomena found in CBCPW integrated through line are investigated in detail both experimentally and theoretically. Two CBCPW through-line test circuits have been built and tested. One has uniform side planes and the other contains two slits in the middle of the side planes. Three techniques are used to investigate the resonant phenomena, namely, the patch antenna cavity model, the multimode model, and the full-wave space-domain integral equation approach. The measured transmission ( mod S/sub 21/ mod ) and reflection ( mod S/sub 11/ mod ) characteristics of the through lines are reported. At a representative resonant frequency of the measured data, current distributions are displayed, demonstrating that the side planes of the CBCPW contribute to the resonance in a way similar to planar patch antenna or 2D planar circuits. >

Design of Synthetic Quasi-TEM Transmission Line for CMOS Compact Integrated Circuit

This paper presents the design guidelines of the synthetic quasi-TEM transmission line (TL) based on standard 0.18 mum one-poly six-metal complementary metal-oxide-semiconductor (CMOS) technology. The synthetic quasi-TEM TL, also called the complementary-conducting-strip transmission line (CCS TL), is composed of five structural parameters to synthesize its guiding characteristics. Twenty-four designs of CCS TL are reported, with the following unique attributes. First, a characteristic impedance range of 8.62-104.0 Omega is yielded. Second, the maximum value of the slow-wave factor is 4.79, representing an increase of 139.5% over the theoretical limit of the quasi-TEM TL. Third, the ratio of the area of the CCS TL to its corresponding quality factor ( factor) can help to estimate the cost of the loss for the circuit miniaturizations. Additionally, the important CMOS manufacturing of metal density is for the first time involved in the reported TL designs. By following the proposed design methodologies, a practical design example of a -band CMOS rat-race hybrid is reported and experimentally examined in detail to reveal the feasibility of the proposed design guidelines to synthesize the CMOS CCS TL. The chip size without contact pads is 420.0 mum 540.0 mum. The measured loss and isolation of the hybrid at 36.3 GHz are 3.84 and 58.0 dB, respectively.

Microstrip leaky-mode antenna array

The first-pass design of a linear eight-element microstrip leaky-mode antenna array is proposed, built, and tested, showing a gain of 18.5 dB, directivity of 23.5 dB, and pencil beam with 3-dB beamwidth (Az/El) of 10.2/spl deg//14.3/spl deg/. Excellent agreement between the theoretical prediction and measured results for the array antenna performance is obtained.

Analysis and design of large leaky-mode array employing the coupled-mode approach

This paper presents the coupled-mode approach to the analysis and design of a large leaky-mode array, in which an N-element microstrip array above a common ground plane supports N coupled leaky modes (leaky EH/sub 1/ modes) at the first higher order. Following a brief description of a conventional full-wave nonstandard eigenvalue problem for solving the complex propagation constants, we present the detailed formulation of the coupled-mode approach, clearly showing the transformation of the nonstandard eigenvalue problem into a standard one. Thus, all the eigenvalues (complex propagation constants) and eigenvectors (modal current distributions) are solved simultaneously, regardless of the size of the array (N). Two key issues pertinent to the successful implementation of the proposed coupled-mode approach are addressed: the determination of the coupling coefficients and the uniqueness of the isolated uncoupled leaky mode, which represents the leaky modal solution of a single microstrip, but is derived from a system of coupled leaky-mode solutions provided the coupled microstrips have equal width and spacing. Closed-form expressions for obtaining the coupling coefficients of orders two, three, and four are presented. Theoretical studies of closely coupled microstrip arrays of two, three, and four elements show that the magnitude of the coupling coefficient /sub i,i+j/ between elements i and i+ decreases at the order of 10/sup -j/. These theoretical case studies also lead to the same isolated uncoupled leaky-mode solution as predicted. Furthermore, the dispersion characteristics of the microstrip array at the first higher order obtained by the coupled-mode approach and the full-wave approach agree excellently for all the case studies. Error analyses indicated that at least two coupling coefficients (C/sub i,i+1/ andC/sub i,i+2/) are required for obtaining accurate complex propagation constants with rms errors less than 1% for most of the leaky region of the particular array under investigation. An example of applying the proposed coupled-mode- approach for analyzing a corporate-fed leaky-mode array of eight elements is reported, revealing that only four out of the eight leaky modes are excited. The coupled-mode theory predicts the far-field radiation pattern in the main beam region in excellent agreement with the measured results.

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In this paper, an X-band CMOS single chip integrating 16 building blocks is developed for frequency modulation continuous wave radar application. The quadrature and monopulse transceiver consists of a voltage-controlled oscillator, amplifiers, Wilkinson power dividers, 90deg hybrid low-noise amplifiers, rat-race hybrid, a single-pole double-throw switch, an active bandpass filter (BPF), and mixers. The transceiver is fabricated in a standard mixed-signal/RF bulk 0.18-mum CMOS technology with a chip area of 2.6 mm 3.3 mm, including contact pads. The transceiver is implemented by meandered complementary-conducting-strip transmission lines demonstrating their capability of miniaturizing circuits such as 90deg hybrid and rat-race hybrid with 95% and 98% size reduction compared to the prototype designs, respectively. The active BPF consumes 4.5 mW achieving 0-dB insertion loss at the passband. The total power consumption of the transceiver is 0.35 W. Output power of the transmitter is 1 dBm with a 35-dB second harmonic suppression. Moreover, the on-chip isolations between T/R in this compacted transceiver are more than 60 dB. The measured receiver gain and NF are -4.5 and 11.5 dB, respectively. Finally, the obtained in-phase and quadrature signals demonstrate 0.6-dB amplitude and 7deg phase imbalance.

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A new quasi-planar leaky-wave antenna is presented. It consists of microstrip line on one side of the substrate and uniplanar circuit on the other side placed in a partially opened waveguide. The leakage is produced by the excitation of the first higher order (odd) microstrip mode coupled electromagnetically through a slotline on the opposite side of the substrate. Theoretic results based on rigorous Greens impedance integral equation method show that the new microstrip-slotline-coupled leaky-wave antenna has a broadband tuning range via structure parameters and is insensitive to the microstrip line width variation. Measured relative power absorbed (RPA) results indicate that the useful frequency bandwidth agrees with that predicted by rigorous field theory. The measured antenna radiation patterns also agree very well with the approximate theoretic computations. The theory and experiments show that the proposed leaky-wave antenna can interface to feeding structure easily and directly. The new antenna may become a good candidate for microwave and millimeter-wave integrated antenna design.