Input Voltage Standing Wave Ratio Research Articles

Analysis and fabrication of a small-scale radio-frequency balun for magnetic resonance imaging amplifier.

In this study, the authors report the design and fabrication of a small mixed-integrated balun for magnetic resonance imaging (MRI). The device was designed by using the positive anti-symmetric coupling method, which applies the lump surface-mount technology capacitors as well as mirror-symmetric coupling strips that were etched on the top and bottom layers of a printed circuit board. The capacitors reduced the length of the coupling strips and compensated for imbalances in the phase and gain due to errors in the fabrication process. The structure and equivalent even-odd circuit model of the device was modeled and examined using commercial software to optimize the design parameters. Following this, the device was fabricated and its performance was assessed through measurements using a network analyzer. The results showed that imbalances in the gain and phase were lower than 0.1 dB and 1°, respectively, and the insertion loss and the input voltage standing-wave ratio (VSWR) were lower than 0.4 dB and -25 dB, respectively. More importantly, the device was small, with dimensions of 50 × 60 × 1.5mm. This makes it suitable for MRI applications involving highly integrated miniaturized systems. The proposed device was integrated into a 3.0T radio-frequency power amplifier (RFPA) and reduced the dimensions of its power modules by 20% compared with the traditional balun. Finally, the RFPA module was used in an 3.0T MRI system for imaging experiments, and the results showed that the balun can help obtain high-quality scanning images.

Analysis and Design of a Wideband Low-Noise Amplifier with Bias and Parasitic Parameters Derived Wide Bandpass Matching Networks

This paper proposes a 110% relative bandwidth (RBW) low-noise amplifier (LNA) for broadband receivers with flat gain, low noise and high linearity. Bias and parasitic parameters derived wide bandpass (BPDWB) matching networks and a cascode with dual feedbacks are introduced for broadband performance. Matching network design procedures are demonstrated, and results show that the frequency response of the network fits the target impedance well from 1 GHz to 3.5 GHz. The proposed BPDWB network improves the design efficiency and enhances the prediction accuracy of impedance matching. The proposed LNA in 0.25 μm GaAs pseudomorphic high electron mobility transistor (GaAs pHEMT) technology realizes a minimum NF of 0.45 dB at 1.6 GHz where the NF is less than 0.55 dB within the operating frequency band. A flat gain of 22.5–25.2 dB is achieved with the input voltage standing wave ratio (VSWR) below 1.22 and output VSWR less than 2.5. In addition, the proposed LNA has good linearity where the output third-order intercept point (OIP3) is better than +31.5 dBm, and the output 1 dB compression point (OP1dB) is better than +19 dBm over the wide frequency range.

DESIGN OF DUAL-BAND SERIES-FED DIPOLE PAIR ANTENNA USING PROXIMITY-COUPLED STRIP AND SPLIT-RING RESONATOR DIRECTORS

In this paper, a design of a dual-band series-fed dipole pair (SDP) antenna using proximity- coupled strip and split-ring resonator (SRR) directors is presented. Two different types of directors are placed close to the top element of the SDP antenna. First, a thick strip director is used to enhance the bandwidth and gain characteristics of the SDP antenna. Next, a pair of SRR directors is appended to both sides of the strip director to create a new resonance for dual-band operation. The performance of three different SDP antenna structures (with a strip director, with a pair of SRRs, and with both directors) are compared with the conventional SDP antenna without directors. When the strip and SRR directors are used together, the mutual coupling might affect the impedance matching of the original frequency band of the SDP antenna and the distance between the two directors is an importance parameter to decide the performance of the antenna. The effects of the distance between the strip and the SRR directors on the input voltage standing wave ratio (VSWR) and realized gain characteristics are studied. A prototype of the proposed dual-band SDP antenna operating in the global positioning system L1 (1.563-1.587 GHz) and 1.7-2.8 GHz bands is designed and fabricated on an FR4 substrate. The experiment results show that the antenna has dual-band characteristics in the 1.56-1.63 GHz and 1.68-2.87 GHz frequency bands for a VSWR < 2. Measured gain is 5.9-7.5 dBi in the former frequency band, whereas it ranges from 6.2 dBi to 7.3 dBi in the latter.

Design of Four-Arm Equiangular Spiral Antenna in Mine Communication

According to the propagation characteristics of radio wave in mine tunnels, in order to realize the communication and detection in underground tunnels, a four-arm equiangular spiral antenna is presented in the paper, which based on the principle and structure of traditional two-arm spiral antenna, and reduces the antenna size. CST software is used to construct and simulate the antenna model. The antenna is tested by the PNA3621 vector network meter. Simulation and measurement results show that the antenna has good performance in 652MHz-3.012GHz frequency range, antenna input voltage standing-wave ratio VSWR and return loss RL are ideal, and antenna pattern is better, which agrees well with the simulated results.

Design and Simulation of S-Band Low Noise Amplifier Based on ATF-54143

This design used a low noise enhanced high electron mobility transistor ATF54143 and Agilent's ADS simulation software to achieve the good performance of operating frequency at 2.45GHz, noise figure (NF) is less than 0.8dB, band gain (S21) is greater than 15dB, input voltage standing-wave ratio (VSWR1) is less than 1.4dB, output voltage standing-wave ratio (VSWR2) is less than 1.6dB.

Wideband 5-bit MMIC Digital Attenuator With High Precision

This paper mainly introduces the Wideband 5-bit MMIC digital attenuator with high precision. Firstly, the theories of basic GaAs digital attenuator MMICâ??s configurations are searched. Secondly, every possible configuration is contrasted, subsequently, appropriate topology is selected for each stage. This attenuator has been realized by 0.5µm GaAs pHEMT process. Simulation results of the digital attenuator has 0.25dB resolution and 7.75dB dynamic attenuation range, Input Voltage Standing Wave Ratio(VSWRIN) was less than 1.55 and Output Voltage Standing Wave Ratio(VSWROUT) was less than 1.6 for all attenuation states, high attenuation accuracy is less than ±0.26dB; insertion loss is less than 1.3dB; The layout of the digital attenuator with a chip size is 0.93 mmA?1.45 mm

Low‐profile circularly polarised loop antenna assisted with an effective PMC bandwidth

Proposed is an ultra-low-profile loop antenna backed by an electromagnetic bandgap (EBG) surface reflector, where the EBG surface can effectively exhibit the property of a perfect magnetic conductor (PMC) inside a deliberately designed bandwidth. It is shown that, assisted by the effective PMC bandwidth, while the proposed antenna is with a 0.07-λ spacing between the loops and the EBG reflector, its axial ratio (AR) and voltage standing wave ratio (VSWR) performances are significantly improved. Experimental measurements show that the prototype antenna has a 3 dB AR bandwidth of 17% with an input VSWR less than 1.6. The proposed approach can find a wide range of low-profile circularly polarised (CP) antenna applications.

Design and Fabrication of an End-Launched Rectangular Waveguide Adapter Fed by a Coaxial Loop

An end-launched adapter combining a coaxial loop within a rectangular waveguide has been analyzed and designed. The accurate electromagnetic modeling of input impedance for the adapter design has been developed using a modal analysis method. Also, design parameters to improve the end-launched adapter have been investigated. Numerical and experimental results of the proposed model have been compared with the results of previous works, and verified by an electromagnetic simulator of High Frequency Structure Simulator (HFSS). The input voltage standing wave ratios (VSWRs) are smaller than 2 over the wide frequency band from 7.5 GHz to 10.5 GHz.

Design and implementation of a high-performance 60-GHz CMOS slot antenna

This article describes the design and implementation of a monolithic 60-GHz millimeter-wave planar CMOS slot antenna. A finite element method-based three-dimensional full-wave electromagnetic solver, high-frequency structure simulator, is used to simulate and optimize the performance of the antenna. The feeding network adopts the coplanar waveguide (CPW) structure, so the on-chip antenna can be flip-chip bonded to a CPW RO4003 conversion board for complete radiation-pattern measurement. Nearly, omnidirectional operation is achieved by providing four major current paths in the shape of a cross for radiation. The measured input voltage standing wave ratio of the on-chip slot antenna is smaller than 2 for frequencies 54.6–68.3 GHz. The measured maximum power gain is −0.74 dB at 60 GHz, one of the highest power gains ever reported for a CMOS antenna at 60 GHz. The chip area is only 1 × 0.8 mm2, i.e., 0.8 mm2. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2061–2065, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27012

Design and implementation of A 24-/60-GHz dual-band monopole meander-line planar CMOS antenna

This article describes the design and implementation of a monolithic 24/60-GHz dual-band millimeter- wave planar CMOS antenna.A finite element method-based 3D full-wave electromagnetic solver, high-frequency structure simulator, is used to simulate and optimize the performance of the antenna. The feeding network adopts the coplanar waveguide (CPW) structure, so the on-chip antenna can be flip-chip-bonded to a CPW RO4003 conversion board for complete radiation-pattern measurement. The main structure uses meander-line to save chip area. Dual-band operation is achieved by providing two major current paths for radiation. The measured input voltage standing wave ratio of the on-chip dual-band antenna is smaller than 2 for frequencies 10–25.7 and 58.4–66.6 GHz. The measured maximum power gain is −7 dB at 60 GHz, one of the highest power gains ever reported for a CMOS antenna at 60 GHz. The chip area is only 1 × 0.75 mm2, i.e., 0.75 mm2, excluding the periphery conductor and the dummy metals for metal density requirement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1731–1737, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26916

고주파 시스템 온 칩 응용을 위한 온 칩 검사 대응 설계 회로

본 논문은 고주파 시스템 온 칩 응용을 위한 온 칩 검사 대응 설계 (Design-for-Testability, DFT) 회로를 제안한다. 이러한 회로는 고주파 회로의 주요 성능 변수들 즉, 입력 임피던스, 전압이득, 잡음지수, 입력 전압 정재비 (VSWRin) 및 출력 신호대 잡음비 (SNRout)를 고가의 장비없이 측정 가능하다. 이러한 고주파 검사 회로는 DFT 칩으로부터 측정된 출력 DC 전압에 실제 고주파 소자의 성능을 제공하는 자체 개발한 이론적인 수학적 표현식을 이용한다. 제안한 DFT 회로는 외부 장비를 이용한 측정 결과와 비교해 볼 때 고주파 회로의 주요 성능 변수들에 대해 5.25GHz의 동작주파수에서 2%이하의 오차를 각각 보였다. DFT 회로는 고주파 소자 생산뿐만 아니라 시스템 검사 과정에서 칩들의 성능을 신속히 측정할 수 있으므로 불필요한 소자 복사를 위해 소요되는 엄청난 경비를 줄일 수 있으리라 기대한다. This paper presents on-chip Design-for-Testability (DFT) circuit for radio frequency System-on-Chip (SoC) applications. The proposed circuit measures functional specifications of RF integrated circuits such as input impedance, gain, noise figure, input voltage standing wave ratio (VSWRin) and output signal-to-noise ratio (SNRout) without any expensive external equipment. The RF DFT scheme is based on developed theoretical expressions that produce the actual RF device specifications by output DC voltages from the DFT chip. The proposed DFT showed deviation of less than 2% as compared to expensive external equipment measurement. It is expected that this circuit can save marginally failing chips in the production testing as well as in the RF system; hence, saving tremendous amount of revenue for unnecessary device replacements.

A novel simultaneous noise and input VSWR matching technique for broadband LNA

The Simultaneous Noise and Input Voltage Standing Wave Ratio (VSWR) Matching (SNIM) condition for Low Noise Amplifier (LNA), in principle, can only be satisfied at a single frequency. In this paper, by analyzing the fundamental limitations of the narrowband SNIM technique for the broadband application, the authors present a broadband SNIM LNA systematic design technique. The designed LNA guided by the proposed methodology achieves 10 dB power gain with a low Noise Figure (NF) of 0.53 dB. Meanwhile, it provides wonderful input matching of 27 dB across the frequency range of 3∼5 GHz. Therefore, broadband SNIM is realized.

An Impedance-Matched 2-Element Superdirective Array

With proper adjustment of the amplitude and phase of the element excitations, the directivity of an N-element end-fire array of isotropic radiators can approach N2 as the spacing between the elements approaches zero. To achieve this end-fire superdirectivity for a 2-element array, the excitation phase difference between the elements must closely approach 180deg. When closely spaced elements are driven nearly 180deg out-of-phase, the element radiation resistances approach zero, resulting in a high input Voltage Standing Wave Ratio (VSWR) and reduced radiation efficiency. At the same time, there is also a significant decrease in the operating bandwidth. In this letter we present the design of a 2-element, superdirective multiple arm folded monopole array that achieves a near 50 Omega input radiation resistance at each element, resulting in a matched input VSWR, higher radiation efficiency and therefore, a substantial increase in realized or overall efficiency.

위성 DAB 수신을 위한 저잡음 증폭기의 설계 및 구현에 관한 연구

본 논문에서는 1,452∼l,492 MHz L-Band 대역의 위성 DAB 수신기를 위한 저잡음증폭기를 입ㆍ출력 반사계수와 전압정재파비를 개선하기 위하여 평형증폭기 형태로 설계 및 제작하였다. 저 잡음증폭기는 GaAs FET소자인 ATF-10136을 사용한 저 잡음증폭단과 MMIC 소자인 VNA-25을 사용한 이득증폭단을 하이브리드 방식으로 구성하였으며, 최적의 바이어스를 인가하기 위하여 능동 바이어스 회로를 사용하였다. 적용된 능동 바이어스 회로는 소자의 펀치오프전압(<TEX>$V_P$</TEX>)과 포화드래인 전류(<TEX>$I_{DSS}$</TEX>)의 변화에 따라 주어진 바이어스 조건을 만족시키기 위해 소스 저항과 드래인 저항의 조절이 필요없다. 즉, 능동 바이어스 회로는 요구된 드래인 전류와 전압을 공급하기 위해 게이트-소스 전압(<TEX>$V_{gs}$</TEX>)을 자동적으로 조절한다. 저잡음증폭기는 바이어스 회로와 RF 회로를 FR-4기판 위에 제작하였고, 알류미늄 기구물에 장착하였다. 제작된 저잡음증폭기는 이득 32 dB, 이득평탄도 0.2 dB, 0,95 dB 이하의 잡음지수, 입ㆍ출력 전압정재파비는 각각 1.28, 1.43이고, <TEX>$P_{1dB}$</TEX> 는 13 dBm으로 측정되었다. In this paper, a LNA(Low Noise Amplifier) has been developed, which is operating at L-band i.e., 1452∼1492 MHz for satellite DAB(Digital Audio Brcadcasting) receiver. The LNA is designed to improve input and output reflection coefficient and VSWR(Voltage Standing Wave Ratio) by balanced amplifier. The LNA consists of low noise amplification stage and gain amplification stage, which make a using of GaAs FET ATF-10136 and VNA-25 respectively, and is fabricated by hybrid method. To supply most suitable voltage and current, active bias circuit is designed Active biasing offers the advantage that variations in <TEX>$V_P$</TEX> and <TEX>$I_{DSS}$</TEX> will not necessitate a change in either the source or drain resistor value for a given bias condition. The active bias network automatically sets <TEX>$V_{gs}$</TEX> for the desired drain voltage and drain current. The LNA is fabricated on FR-4 substrate with RF circuit and bias circuit, and integrated in aluminum housing. As a reults, the characteristics of the LNA implemented more than 32 dB in gain. 0.2 dB in gain flatness. lower than 0.95 dB in noise figure, 1.28 and 1.43 each input and output VSWR, and -13 dBm in <TEX>$P_{1dB}$</TEX>.

Size Optimization of a Microstrip GPS Antenna for Automobile Glass with a Genetic Algorithm

Using a genetic algorithm, we designed a microstrip antenna for the Global Position System (GPS), to be placed on the rear window glass of an automobile as a dielectric material. The antenna has right-hand circular polarization, near hemispherical coverage, and operates at the frequency of 1.57542 GHz. This antenna was simulated using the multiport network model (MNM)/method of moments (MoM: Rao, Wilton, Glisson (RWG) basis functions) and then fabricated and test. It is a square with sides of 3.6 cm and a truncated corner size 0.55 cm. The input voltage standing wave ratio and far field patterns were computed and measured. Satisfactory experimental results were obtained in field tests.

Realization of a genetic‐algorithm‐optimized wire antenna with 5:1 bandwidth

Techniques for developing and realizing a broadband, loaded wire antenna with a transmission line transformer matching network are presented. The component values and position of a parallel inductor‐resistor load circuit are optimized via a genetic algorithm to improve the bandwidth of a straight‐wire monopole antenna. Candidate antennas are analyzed by solving the electric field integral equation with a lumped‐load model included. This model has been enhanced with fast algorithms from the literature in order to improve computational efficiency during optimization. Subsequent to optimization, the curved‐wire integral equation solution is used to more closely model a real‐world monopole loaded with a helical coil and parallel resistor. The measured input voltage standing wave ratio of the loaded antenna with matching network is below 3.5 over a 5:1 bandwidth (200–1000 MHz). The computed system gain is above −4.0 dBi over the band 220–1000 MHz.

Design of a vehicular antenna for GPS/Iridium using a genetic algorithm

In this paper, we describe a vehicular wire antenna, designed using a genetic algorithm that may be used for both the GPS and Iridium systems. It has right-hand circular polarization, near hemispherical coverage, and operates over the frequency band from 1225 to 1625 MHz. This antenna was simulated using the numerical electromagnetics code (NEC) and then fabricated and tested. The antenna consists of five copper tubing segments connected in series, has an unusually odd shape, and is very inexpensive. It fits in a volume approximately 10 cm/spl times/10 cm/spl times/15 cm, The input voltage standing wave ratio (VSWR) and circular polarization radiation patterns were computed and measured. The VSWR was under 2.2 at the design frequencies of 1225, 1575, and 1625 MHz. The gain varied by less than 12 dB for a 170/spl deg/ sector; it generally fell off near the horizon so the variation was less for 150/spl deg/ and 160/spl deg/ sectors. This new design process, which uses a genetic algorithm in conjunction with an electromagnetics code, produces configurations that are unique and seem to outperform more conventional designs.

Crossed dipoles fed with a turnstile network

A "turnstile network" is introduced which may be conveniently used for circular polarization synthesis. The network, outfitted with proper phasing stubs, forms a balanced quadrature hybrid; for an antenna with less than a perfect reflection coefficient, the reflected power will appear at an isolated port, which may be terminated, resulting in good polarization properties coupled with good input voltage standing-wave ratio. A crossed-dipole array is used as a test-bed to demonstrate the turnstile network.

An integrated CMOS distributed amplifier utilizing packaging inductance

An integrated CMOS distributed amplifier is presented. The required inductance needed for the distributed waveguide structure is realized by the parasitic packaging inductance of a plastic surface-mount package. A fully packaged three-stage distributed amplifier fabricated in a 0.8-/spl mu/m CMOS process is presented. The distributed amplifier has a unity gain cutoff frequency of 4.7 GHz, a gain of 5 dB, with a gain flatness of /spl plusmn/1.2 dB over the 300-kHz to 3-GHz band. At a frequency of 2 GHz the amplifier has an input referred third-order intercept point of +15 dBm and an input referred 1-dB compression point of +7 dBm. The amplifier consumes 18 mA from a 3.0-V supply. The distributed amplifier is matched to 50 /spl Omega/ at the input and output and has a maximum input voltage standing-wave ratio (VSWR) of 1.7:1, and a maximum output VSWR of 1.3:1 over the 300 kHz to 3 GHz band. The amplifier has a noise figure of 5.1 dB at 2 GHz.

A 29.3-GHz cavity-enclosed aperture-coupled circular-patch antenna for microwave circuit integration

A circular patch antenna fed by an aperture-coupled microstrip line has been demonstrated at 29.3 GHz. The patch was enclosed by a cavity to reduce surface-wave interactions in an array environment and to improve heat dissipation when using active devices. The antenna exhibited a 2:1 input VSWR (voltage standing wave ratio) over a bandwidth of 12% from 27.52 to 30.95 GHz. The antenna should have applications in conformal phased arrays at millimeter-wave frequencies. >