Matched Transmission Line Research Articles

Development of a microwave photoconductance measurement technique for the study of carrier dynamics in highly-excited 4H-SiC

The microwave conductance decay (MCD) technique combining an initially matched transmission line setup and picosecond optical excitation was developed and applied for the monitoring of transmitted and reflected microwave power transients in a 4H-SiC epilayer in a wide excitation range, from 2 × 1014 to 1018 cm−3. The excitation-dependent decrease in measurement sensitivity in the power-law relations of the transients was observed at excess carrier densities above 1016 cm−3 due to the line mismatches and decrease in the internal microwave field in the illuminated sample. The calibration procedure of MCD data on excess carrier density was applied for the correction of the MCD transients and resulted in nearly identical MCD kinetics in the reflection and transmission. In a 35 μm-thick n-type 4H-SiC epilayer, the tendencies of the gradual decrease of the initial decay time with an excitation increase and the excitation-enhanced carrier recombination rate in MCD tails were analyzed numerically. These tendencies were attributed to the excitation dependent surface recombination rate and the enhanced trap-related bulk recombination, correspondingly.

Design of low distortion high voltage coaxial-type transmission line for quasi-square wave nano-pulse with several hundred kilovolts in vacuum

A high voltage quasi-square wave pulse with an amplitude of above 500 kV is successfully transmitted using a coaxial-type matched transmission line in vacuum. To enhance the surface flashover voltage and reduce the distortion of pulse shape, the matched symmetric coaxial solid dielectric configuration with the positive angle of 45° and the socket-type field shaper are proposed and applied to the coaxial transmission line. This type of transmission line provides not only the high capability of hold off voltage but also good pulse shape corresponding to the input pulse. The transmission of quasi-square wave short pulse with an amplitude of above 500 kV, a pulse duration of above 20 ns, and a rise time of 20-30 ns without the surface flashover and the pulse distortion phenomena is experimentally and numerically presented.

Beyond the Smith Chart: A Universal Graphical Tool for Impedance Matching Using Transformers

The topic of impedance transformation and matching is one of the well-established and essential aspects of microwave engineering. A few decades ago, when discrete radio-frequency (RF) design was dominant, impedance matching was mainly performed using transmission-lines techniques that were practical due to the relatively large design size. As microwave design became possible using integrated on-chip components, area constraints made L-C section matching (using lumped passive elements) more practical than transmission line matching. Both techniques are conveniently visualized and accomplished using the well-known graphical tool, the Smith chart.

Design of on-chip 15~18 GHz ultra low noise amplifier

With rapid development communication system, high signal to noise ratio (SNR) system is required. In high frequency bandwidth, high loss, low Q inductors and high noise figure is a significant challenge with on-chip monolithic microwave integrated circuits (MMICs). To overcome this problem, high Q, low loss transmission line characteristics was analyzed. Compared with the same inductor value of the lumped component and the transmission line, it has a higher Q value and lower loss performance in high frequency, and a 2-stage common-source low noise amplifier (LNA) was presented, which employs source inductor feedback technology and high Q low loss transmission line matching network technique with over 17.6 dB small signal gain and 1.1 dB noise figure in 15 GHz–18 GHz. The LNA was fabricated by WIN semiconductors company 0.15 μm gallium arsenide (GaAs) P high electron mobility transistor (P-HEMT) process. The total current is 15 mA, while the DC power consumption is only 45 mW.

非匹配传输线产生宽谱脉冲实验研究

非匹配传输线产生宽谱脉冲实验研究

65 nm CMOS 공정을 이용한 77 GHz LNA 설계

This work presents a 77 GHz low noise amplifier(LNA) for automotive radar systems using 65 nm RF CMOS process. The LNA is composed of three stage common source amplifiers and includes transmission line matching networks. To reduce the time for three dimensional EM simulation, we optimize the transmission line impedance matching network using a pre-built EM library. The proposed compact simulation technique is confirmed by measurement results. The peak gain of the LNA is 10 dB at 77 GHz and input/output return losses are below -10 dB around the design frequency.

An Exposition on the Choice of the Proper S Parameters in Characterizing Devices Including Transmission Lines with Complex Reference Impedances and a General Methodology for Computing Them

The purpose of this paper is to demonstrate that the recently published paper [1] dealing with little known facts and some new results on transmission lines is due to an incomplete interpretation of the nonphysical artifacts resulting from a particular mathematical model for the S parameters. These artifacts are not real and do not exist when a different form of the S parameters is used.The first objective of this paper is thus to introduce the two different types of S parameters generally used to characterize microwave circuits with lossy characteristic impedance. The first type is called the pseudo wave, an extension of the conventional traveling-wave concepts, and is useful when it is necessary to discuss the properties of a microwave network junction, irrespective of the impedances connected to the terminals. However, one has to be extremely careful in providing a physical interpretation of the mathematical expressions, as in this case the reflection coefficient can be greater than one, even for a passive load impedance with a conjugately matched transmission line. The power balance also cannot be simply obtained from the powers associated with the incident and reflected waves. Hence, this cannot be applied for broadband characterization of antennas. The second type of S parameter is called the power-wave scattering parameter. This is useful when one is interested in the power relationship between microwave circuits connected through a junction. In this case, the magnitude of the reflection coefficient cannot exceed unity, and the power delivered to the load is directly given by the difference between the powers associated with the incident and the reflected waves. Since this methodology deals with the reciprocal relationships between powers from various devices, this may be quite suitable for dealing with a pair of transmitting and receiving antennas where power reciprocity holds. This methodology is also applicable in network theory, where the scattering matrix of a two-port (or a multi-port) can be defined using complex reference impedances at each of the ports without any transmission line being present, so that the concept of characteristic impedances becomes irrelevant. Such a situation is typical in small-signal microwave transistor amplifiers, where the analysis necessitates the use of complex reference impedances in order to study simultaneous matching and stability. However, for both definitions for the S parameters, when the characteristic impedance or the reference impedance is complex, the scattering matrix does not need to be symmetric, even if the network in question is reciprocal.The second objective is to illustrate that when the characteristic impedance of the line or the reference impedances in question is real and positive, then both of the pseudo-wave and the power-wave scattering parameters provide the same results. Finally, a general methodology is presented with examples to illustrate how the S parameters can be computed for an arbitrary network without any a priori knowledge of its characteristic impedance.

A penta-band folded antenna for mobile phone application

A penta-band folded antenna for mobile phone applications is presented.The antenna is comprised of two modified inverted-L monopole radiators with a short grounded transmission line for impedance matching and includes a ground plane printed on FR-4 substrate. The radiators are bonded onto a plastic carrier whose dimensions are 50 × 15 × 4 mm3. The antenna is designed and optimized to generate two separate bands, ranging from (i) 870 to 1010 MHz and (ii) 1710 to 2490 MHz with return loss for both better than 7.5 dB. Thus, the antenna covers five bands useful for mobile phone applications, namely, Global System for Mobile Communications/Digital Communication System/Personal Communication Services/Universal Mobile Telecommunications System/Bluetooth. The design strategy was such that the two separate widebands of interest can be controlled relatively independently. Design considerations for the constructed prototype are discussed. The effects of the ground plane, the mobile phone housing and the human hand on the return loss, and the efficiency of the proposed antenna are also investigated. It is found that the hand grip on the mobile phone has a significant effect on the performance of the antenna, especially its efficiency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:34–40, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27274

Miniature UWB Filter Using Three-Quarters Wavelength Resonator with Direct-Connected Feed Method

A miniature ultra-wideband (UWB) bandpass filter using three-quarters wavelength resonators is presented in this paper. Direct-connected feed method is employed between the input/output ports and the resonators in order to overcome the shortcomings due to the gap-coupled feed method and produce two transmission zeros in the lower and upper stopbands. On the other hand, two quarter-wavelength matching transmission lines are introduced to the input/output ports to improve the reflection loss characteristic in the passband of the filter. In addition, the resonators are folded to be open ring structures, which are more miniaturized than the conventional linear structure. As a consequence, the filter is compact in size and exhibits good performance. The filter is successfully realized in theory and verified by full wave EM simulation, and simulated frequency response results show that the fabricated filter has an insertion loss of better than 1dB in the passband and two rejections of greater than 25dB in most of the stopbands.

An improved method to measure the antenna resistance and radiated power of ICRF-antennas using current probes

The coupling properties of ICRF antennas depend on the plasma boundary characteristics, which are modified for example by H-Mode or ELMs. The impedance and the power into the antenna feeding line are measured with a pair of directional couplers near the double stub tuner matching system. Those measurements include the losses of the transmission line and the antenna. An approach to separate the radiated power from the losses is to measure the current in the antenna loops. To measure the current in the short of the antenna loop two current probes have been installed near the short of the antenna loops in one of the ICRF antennas during the 2009/2010 shutdown of ASDEX Upgrade. These signals allow a new approach in calculating the antenna resistance and the launched power and can be used to separate the launched power from the losses in the matching system and transmission lines up to the antenna. Although the calibration of the signal amplitude from the current probes needs further investigation, the amplitude is proportional to the current in the antenna loop. With those probes and a new real-time DSP-based system, the radiated (as opposed to the total power i.e. including loss power) power can be feedback controlled.

Concurrent Hex-Band GaN Power Amplifier for Wireless Communication Systems

In this letter, we propose a novel multi-section transmission line matching technique applied to the design of a concurrent hex-band HEMT GaN power amplifier (PA). The PA has been designed for a concurrent operation at 0.9, 1.8, 2.5, 3.5, 5.2, and 5.8 GHz. Experimental results have shown minimum and maximum saturated output power levels of 33 dBm and 36.7 dBm respectively over the different frequency bands, with the power added efficiency (PAE) ranging from a minimum of 20% to a maximum of 49%. A detailed comparison between simulation and experimental results data has also been reported.

A design methodology for the 60 GHz CMOS power amplifier using on-chip transformers

This letter presents a design methodology for the millimeter wave amplifier using 90-nm Taiwan Semiconductor Manufacture Company (TSMC) CMOS technology. The proposed design scheme with mathematically modeled transmission lines and interstage matching transformers illustrates how to design a millimeter amplifier considered in the maximum power transfer. The single-ended transformer-coupled CMOS PA is implemented to verify the design methodology. The design consists of neutralized common source (CS) amplifiers, matching transmission lines, and 3D modeled transformers. The designed circuit shows 16.2-dB gain and 9-dBm saturation power over 60-GHz channel. The measured results are well matched with the proposed modeling results. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:506–509, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25782

Design of transmission line driven slot waveguide Mach-Zehnder interferometers and application to analog optical links

Slot waveguides allow joint confinement of the driving electrical radio frequency field and of the optical waveguide mode in a narrow slot, allowing for highly efficient polymer based interferometers. We show that the optical confinement can be simply explained by a perturbation theoretical approach taking into account the continuity of the electric displacement field. We design phase matched transmission lines and show that their impedance and RF losses can be modeled by an equivalent circuit and linked to slot waveguide properties by a simple set of equations, thus allowing optimization of the device without iterative simulations. We optimize the interferometers for analog optical links and predict record performance metrics (V(pi) = 200 mV @ 10 GHz in push-pull configuration) assuming a modest second order nonlinear coefficient (r(33) = 50 pm/V) and slot width (100 nm). Using high performance optical polymers (r(33) = 150 pm/V), noise figures of state of the art analog optical links can be matched while reducing optical power levels by approximately 30 times. With required optical laser power levels predicted at 50 mW, this could be a game changing improvement by bringing high performance optical analog link power requirements in the reach of laser diodes. A modified transmitter architecture allows shot noise limited performance, while reducing power levels in the slot waveguides and enhancing reliability.

Passive Intermodulation in Finite Lengths of Printed Microstrip Lines

This paper addresses the theoretical aspects of passive intermodulation (PIM) generation in printed transmission lines. In order to elucidate the mechanisms of PIM generation, a new model of the transmission line length with distributed nonlinearity is proposed. The developed model has been validated by the near-field measurements of PIM product distributions along the microstrip lines. The contributions of nonlinear mixing, power dissipation, and load matching to PIM products have been analyzed in detail. The obtained results reveal the fundamental properties of PIM generation in finite lengths of printed lines with distributed nonlinearity and identify possible means for PIM mitigation. It was shown for the first time that the reverse PIM products in a matched transmission line with distributed nonlinearity are generated due to nonlinear scattering.

Gerbil middle-ear sound transmission from 100Hzto60kHz

Middle-ear sound transmission was evaluated as the middle-ear transfer admittance H(MY) (the ratio of stapes velocity to ear-canal sound pressure near the umbo) in gerbils during closed-field sound stimulation at frequencies from 0.1 to 60 kHz, a range that spans the gerbil's audiometric range. Similar measurements were performed in two laboratories. The H(MY) magnitude (a) increased with frequency below 1 kHz, (b) remained approximately constant with frequency from 5 to 35 kHz, and (c) decreased substantially from 35 to 50 kHz. The H(MY) phase increased linearly with frequency from 5 to 35 kHz, consistent with a 20-29 micros delay, and flattened at higher frequencies. Measurements from different directions showed that stapes motion is predominantly pistonlike except in a narrow frequency band around 10 kHz. Cochlear input impedance was estimated from H(MY) and previously-measured cochlear sound pressure. Results do not support the idea that the middle ear is a lossless matched transmission line. Results support the ideas that (1) middle-ear transmission is consistent with a mechanical transmission line or multiresonant network between 5 and 35 kHz and decreases at higher frequencies, (2) stapes motion is pistonlike over most of the gerbil auditory range, and (3) middle-ear transmission properties are a determinant of the audiogram.

32‐GHz dual‐termination coupled CPW bandpass filter on HR‐SI

AbstractBandpass filter is an important device in portable communication and other RF systems. A dual‐termination coupled coplanar waveguide (CPW) bandpass filter (BPF) has been designed by HFSS. This dual‐termination coupled structure improves the coupling capacitances between the central metal and the matching transmission lines so that the insertion loss can be reduced. The filter has been fabricated on a high resistivity silicon substrate (ρ ≥ 1000 Ω cm) with 1 μm SiO2. It has −2.16‐dB low insertion loss at peak transmission of about 32 GHz. This filter shows good s‐parameter characteristics and it is attractive for RF ICs. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1705–1706, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23464

Mapping of Power Transmission Lines on Malaysian Highways Using UPM-APSB’s AISA Airborne Hyperspectral Imaging System

Power transmission lines routes mapping is an important technique for locating power transmission line routes and towers on mountain/hilltops to assist viewing of their impacts on the environment, operations and allocation of public utilities. A study was therefore conducted to map the power transmission lines within Bukit Lanjan PLUS highway. The main objective of this study is to assess the capability of airborne hyperspectral sensing for mapping of power transmission. By using ENVI software, the airborne hyperspectral imaging data was enhanced using convolution filtering technique using band 3 which produced a gray scale image which appeared clearer and sharper. The spectral reflectance curves were acquired for each power line which showed the same spectrum characteristics in curve or the reflectance energy. This is because of the same power lines composition material for all power lines. Ground verification was done by comparing the UPM-APSB’s AISA Global Positioning System (GPS) coordinates readings with ground GPS coordinates readings of the power transmission lines footings. The ground verification result from the two matching power transmission line footings showed that the accuracy of power lines identification was acceptable. This study implies that airborne hyperspectral imagers are powerful tools for mapping and spotting of suitable large transmission towers and lines.

초광대역 마이크로스트립 안테나의 설계와 제작에 관한 연구

본 논문에서는 UWB(ultra wideband) 무선통신 응용을 위해 3GHz의 광대역 무지향성 마이크로스트립 패치 배열 안테나를 구현하였다. <TEX>$7.2{\sim}10.2GHz$</TEX>의 광대역의 밴드를 만족시키기 위해 다중공진 안테나가 설계되었고, 각 공진주파수는 600MHz의 간격을 가지고 7.5, 8.1, 8.7, 9.3, 그리고 9.9GHz의 5개 중심주파수로 분리하였고 광대역 특성을 위해, 각 중심주파수에서 U-slot 안테나가 각각 설계되었다. 설계된 5개의 U-slot 안테나는 3GHz의 대역폭의 다중공진을 위해 병렬로 연결되었고, 임피던스 정합 과정은 7.5GHz 패치안테나와 8.1GHz 패치안테나의 중심주파수인 7.8GHz를 적용하여 전송 선로를 구한 후 같은 방법으로 전송 선로 임피던스 정합을 하여 광대역 매칭 회로가 되도록 설계하였다. 안테나 제작에 이용된 PCB 기판의 비유전율, 기판높이, 손실은 각각 <TEX>${\epsilon}_r= 4.8,\;h=0.6$</TEX> 그리고 손살탄젠트는 0.0009였다. 제작된 안테나의 방사패턴과 이득은 5개의 중심주파수에서 <TEX>$1.46{\sim}4.08dBi$</TEX>의 이득을 나타내었다. In this paper, the ultra-widebend, microstrip patch antenna with the bandwidth of 3 GHz was implemented for ultra-wideband(UWB) wireless communication applications. In order to cover the very wide bandwidth of 3 GHz, a multi-resonance antenna was designed, each resonance frequency was separated into five frequency bend, 7.5, 8.1, 8.7, 9.3, and 9.9GHz with the interval of 600MHz BW. And for wideband characteristics of each antenna, U-slot antennas were designed at each center frequency. Designed five U-slot antennas were connected in series for multi-resonance of 3GHz BW and wideband matching was also designed for impedance matching transmission line calculated. The relative dielectric constant, the height, the loss tangent of the PCB substrate were <TEX>${\epsilon}_r=4.8,\;h=0.6$</TEX> and loss tangent=0.0009 respectively. The implemented antenna's radiation patterns and gain were directivity characteristics and <TEX>$1.46{\sim}4.08dBi$</TEX> at the five separated center frequency.

WIDEBAND OR MULTIBAND COMPLEX IMPEDANCE MATCHING USING MICROSTRIP NONUNIFORM TRANSMISSION LINES

A novel method is introduced to synthesize microstrip Nonuniform Transmission Lines (NTLs) for matching between two arbitrary complex frequency dependent impedances in a wideband or multi-band frequency range. First, stripwidth or the characteristic impedance function of the microstrip NTL is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed method is verified using some examples.

Design and Development of Optoelectronic Mixed Signal System-on-Package (SOP)

This paper describes the design and development of a 2.5-Gb/s optical transceiver module as a mixed signal SOP for access networks. The module development consists of concurrent design of an optoelectronic package optimizing optical, electrical, thermal, mechanical functions and optical subassembly and RFICs housed in a chip-on-board package. The optical subassembly (OSA) consists of laser and photodiode assembled on a silicon substrate. The transmit and the receiver sections are combined into a single fiber through a polymer coupler on silicon. The splitter between the transmit and receive section is realized using a polymer waveguide. The electronic ICs are assembled on a multilayer organic substrate. The package design includes optical coupling design, impedance matched transmission line design for RF signals, electrical layout design for mixed signals and thermal design for the package. The module is housed in a plastic molded nonhermetic package to achieve low cost packaging. The assembly is completed using passive alignment of optical devices and attachment of electronic devices using adhesives. In this paper, we present the details of the component design and the development of packaging process methods to achieve the design specifications, test results and process guidelines for assembly and integration.