Transmission-line Impedance Transformer Research Articles

A TO-CAN DFB Laser with Transmission Line Impedance Transformer for Analog Optical Link

A TO-CAN DFB Laser with Transmission Line Impedance Transformer for Analog Optical Link

The Design of a Single-Section Lossless Transmission Line Impedance Transformer [Educator’s Corner

A formula for the fractional bandwidth of a single-section lossless transmission line impedance transformer is available in some books (see e.g., <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> ). The purpose of this short note is to provide information for the design of such transformers, in the form of a graph of the fractional bandwidth versus the transformation ratio. This should prove useful to the designers.

Analytic Model and Optimization of Transmission-Line Impedance Transformers for Tens of MA-Class Pulsed Power Accelerator

The monolithic radial transmission line (MRTL) is a key component in tens of MA-class pulsed power accelerators, which connects the multiparallel modules of the prime pulsed power sources to the central vacuum insulator stack and magnetically insulated transmission line (stack-MITL system). The choice of electrical parameters of MRTL is essential for the entire accelerator design, which would bring great influences on the peak output current and the power couple efficiency. In Phys. Rev. Special Topics-Accel. Beam s, 2015, 18(10): 110401, some semianalytical formulae have been proposed to optimize the MRTL impedance that maximizes the peak current or peak power on the stack-MITL system. However, the formulae are only valid under several assumptions that are thought to be unpractical. In this article, an analytic model of the accelerator is developed to optimize the electrical parameters of MRTL. Analytical expressions of the output voltage and current at the terminal of MRTL are deduced. By simplifying the analytic model, mathematical expressions of the optimal MRTL output impedance that maximizes the peak current or peak power delivered from the prime power sources to the stack-MITL system are obtained. The factors that contribute to the optimal impedance are analyzed comprehensively with short-circuit load and Z-pinch load. Conclusions are beneficial to design the pulsed power accelerator in the future.

Multioctave Power Amplifier Design Using 9:1 Planar Impedance Transformer

In this letter, at the first step, design of a new broadband planar 9:1 transmission line impedance transformer is investigated and several parameters of this transformer, such as characteristic impedances of the lines, their length, and ground plane distance effects, are analyzed from a new point of view. Then, a multioctave power amplifier (PA) is implemented using the introduced transformer as input and output matching network of a power transistor. The fabricated PA achieves a power output more than 46.5 dBm with a flat gain of 10.5 ± 0.7 dB over an ultrawide frequency band from 0.5 to 3 GHz. The measured power added efficiency (PAE) is better than 50% over the whole frequency bandwidth.

Tri-band Impedance Matching Network Design Using Particle Swarm Optimization Algorithm

A solution strategy is presented using a five-section transmission line impedance transformer aiming for multiple band matching network circuits. In this paper, the analysis, which is ...

Compact CVT-/CCT-Unequal Power Dividers for High-Power Division Ratios and Design Methods for Arbitrary Phase Differences

Compact unequal power dividers are suggested for high-power division ratios and arbitrary phase differences. The power dividers are classified into two parts: power-dividing and impedance-transforming parts and consist of the asymmetric impedance transformers of constant voltage-standing wave ratio (VSWR)-type transmission-line impedance transformers (CVTs) and constant conductance-type transmission-line impedance transformers (CCTs). Given the special properties of asymmetric impedance transformers, the arbitrary phase differences between two outputs may be obtained by controlling the impedance-transforming part. Compactness can be achieved by using the equivalent circuits of stepped-impedance modified T-types and LS1-types. A power divider with a power division ratio of 9 (9.542 dB) and total transmission line sections that are 181.1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> long is fabricated to verify compactness and best frequency performance. Another power divider comprising two CVTs and two different CCTs is measured for 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> phase difference between two outputs. The measured results are in good agreement with the predicted findings.

A 4 : 1 Transmission-Line Impedance Transformer for Broadband Superconducting Circuits

We present a 4 : 1 superconducting transmission-line impedance transformer for cryogenic applications. The device transforms 25 Ω in the coplanar waveguide to 6.25 Ω in the microstrip and is designed to operate at 20 mK. Calibrated measurements in a dilution refrigerator demonstrate a -3 dB bandwidth from 1.6 to 13 GHz. In a modified Ruthroff design, a small capacitor is integrated at the input as a direct-current block, making it suitable for biasing and matching to low-impedance active circuits, such as superconducting quantum interference device (SQUID) amplifiers.

NONSYNCHRONOUS NONCOMMENSURATE IMPEDANCE TRANSFORMERS

Nonsynchronous noncommensurate impedance transform- ers consist of a combination of two types of transmission lines: trans- mission lines with a characteristic impedance equal to the impedance of the source, and transmission lines with a characteristic impedance equal to the load. The practical advantage of such transformers is that they can be constructed using sections of transmission lines with a limited variety of characteristic impedances. These transformers also provide comparatively compact size in applications where a wide trans- formation ratio is required. This paper presents the data which allows to estimate the achievable total electrical length and in-band re∞ec- tion coe-cient for transformers consisting of up to twelve transmission line sections in the range of transformation ratios r = 1:5 to 10 and bandwidth ratios ´ = 2 to 20. This data is obtained using wave trans- mission matrix approach and experimentally verifled by synthesizing a 12-section nonsynchronous noncommensurate impedance transformer. The measured characteristics of the transformer are compared to the characteristics of a conventional tapered line transformer. Fast-growing performance requirements demanded in industrial and scientiflc applications continuously challenge the standard approaches to the design of impedance transformers. Implementation of traditional designs based on distributed components leads to a large circuit size, which is highly undesirable in practice. The transformers based on lumped elements are compact, but sufier from low quality-factor at high frequencies. Nonsynchronous noncommensurate (NN) altering transmission line impedance transformers are one of the promising

Modified Asymmetric Impedance Transformers (MCCTs and MCVTs) and Their Application to Impedance-Transforming Three-Port 3-dB Power Dividers

For size reduction and design flexibility of impedance transformers, two modified asymmetric impedance transformers are suggested. They each consist of one open stub and two different transmission-line sections and are named a modified constant conductance-type transmission-line impedance transformer (MCCT) and a modified constant voltage-standing-wave-ratio (VSWR)-type transmission-line impedance transformer (MCVT), depending on where the open stub is located. As their applications, impedance-transforming MCCT- and MCVT-three-port 3-dB power dividers (MCCT- and MCVT-PDs) are presented, and it is found that the isolation circuits should be composed of not only resistance but also capacitance. For high-power applications, MCCT and MCVT Gysel-type PDs are also suggested, and four isolation circuits are developed systematically based on the isolation impedances of the MCCT- and MCVT-PDs. The isolation circuits of the Gysel-type PDs are comprised of three transmission-line sections, shunt resistances connected to ground, and series capacitances/shunt inductances. One MCCT-PD and one MCVT Gysel-type PD are verified by measurements. The measured results show good agreement with the prediction, giving power divisions of -3.08 dB, return losses better than 23.8 dB, and isolation of 24.07 dB at 1 GHz for the MCCT-PD and power divisions of about -3.42 and -3.5 dB, return losses better than 21 dB, and isolation of 28 dB at 2 GHz for the MCVT Gysel-type PD.

Simulation Analysis of Transmission-Line Impedance Transformers With the Gaussian, Exponential, and Linear Impedance Profiles for Pulsed-Power Accelerators

Based on the transmission-line code, a 1-D circuit model for the transmission-line impedance transformer with an arbitrary impedance profile is developed, and the simulation results are compared with those of the existing literatures. By using this model, the power efficiencies and pulse compression ratios of the transformers (with Gaussian, exponential, and linear impedance profiles) were quantified as functions of Ψ (the ratio of the output impedance to the input impedance of the transformers) and Γ (the ratio of the pulsewidth to the one-way transit time of the transformers). The simulation results indicate that the exponential transformers have the maximum power efficiencies and pulse compression ratios. However, in the limit h <; 0.05 (where h is the Gaussian parameter), the Gaussian transformers almost have the same power efficiencies and pulse compression ratios as the exponential ones. Finally, the performances of a radial transformer line in smoothing the arrival time variations in the forward-going power pulses were studied. The simulation results show that, for the cases considered, the rise time (0-1.0) of the output pulse is prolonged by about half of the maximum difference in the time at which the pulses are launched, and the reduction of the peak output power is less than 2% when the maximum difference is 30 ns.

Simulation Analysis of Transmission-Line Impedance Transformers for Petawatt-Class Pulsed Power Accelerators

Based on the transmission line code TLCODE, a 1D circuit model for a transmission-line impedance transformer was developed and the simulation results were compared with those in the literature. The model was used to quantify the efficiencies of voltage-transport, energy-transport and power-transport for a transmission-line impedance transformer as functions of ψ (the ratio of the output impedance to the input impedance of the transformer) and Γ (the ratio of the pulse width to the one-way transit time of the transformer) under a large scale of m (the coefficient of the generalized exponential impedance profile). Simulation results suggest that with the increase in Γ, from 0 to ∞, the power transport efficiency first increases and then decreases. The maximum power transport efficiency can reach 90% or even higher for an exponential impedance profile (m = 1). With a consideration of dissipative loss in the dielectric and electrodes of the transformer, two representative designs of the water-insulated transformer are investigated for the next generation of petawatt-class z-pinch drivers. It is found that the dissipative losses in the electrodes are negligibly small, below 0.1%, but the dissipative loss in the water dielectric is about 1% to 4%.

New Isolation Circuits of Compact Impedance-Transforming 3-dB Baluns for Theoretically Perfect Isolation and Matching

New isolation circuits and design equations of compact impedance-transforming 3-dB baluns are suggested for theoretically perfect isolation and perfect matching at all ports. Any balun consists of two impedance transformers, being 180° out of phase, and an isolation circuit. For compactness, the impedance transformers need to be reduced and the isolation circuits should depend on phase delay of the compact impedance transformers. The compact balun with -90° phase delay of the compact impedance transformer is called the compact II-type balun and the one with non -90° phase delay is called the constant voltage-standing-wave-ratio type transmission-line impedance transformer (CVT) balun. Three isolation circuits are derived for the compact II-type baluns and five for the CVT baluns. Using the isolation circuits derived, the two types of compact baluns are fabricated and measured at a design center frequency of 1.5 GHz. The measured results have good agreement with prediction, showing power divisions of -2.9 and -3.3 dB (- 2.8 and -3.25 dB ), phase difference between two output signals of 181.8°(178.5°) , matching performance of -21.8, -31.8, and -33.8 dB ( -24, -22, and - 28 dB), and isolation of better than 40 dB (27 dB) for the compact II-type (CVT) balun.

A Novel Modified Multiband Planar Inverted-F Antenna

A novel multiband modified planar inverted-F antenna (PIFA) with a compact single feed is proposed, which covers GSM900 (880-960 MHz), DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), Bluetooth/WLAN (2400-2480 MHz), WiMAX (2500-2690 MHz), HiperLAN/2 (5470-5725 MHz), and an additional band (4600-4800 MHz). In conventional PIFA, most of time the shorted pin acts as a capacitor load only for impedance matching purpose, which may yield a large ground plane, narrow bandwidth, and large antenna volume due to a long shorted pin to provide enough capacitance. In our design, the shorted pin just acts a short-circuited load, which is an effective way to control the current resonant paths and is a novel way in design a multiband PIFA. Furthermore, with this design and parasitic folded structures, the proposed multiband antenna can be modeled by parallel short-circuited transmission line impedance transformers (TLIT), which can easily create six mentioned frequency bands (from PCS band to HiperLAN/2 band) by adjusting the lengths of folded branches. Measurement result conforms that our multiband design not only provides size reduction of both the antenna and the ground plane but also enhances the bandwidth of the six bands.

Optimized transmission-line impedance transformers for petawatt-class pulsed-power accelerators

We have developed 1D analytic and 2D fully electromagnetic models of radial transmission-line impedance transformers. The models have been used to quantify the power-transport efficiency and pulse sharpening of such transformers as a function of voltage pulse width and impedance profile. For the cases considered, we find that in the limit as $\ensuremath{\Gamma}\ensuremath{\rightarrow}0$ (where $\ensuremath{\Gamma}$ is the ratio of the pulse width to the one-way transit time of the transformer), the transport efficiency is maximized when the impedance profile is exponential. As $\ensuremath{\Gamma}$ increases from zero, the optimum profile gradually deviates from an exponential. A numerical procedure is presented that determines the optimum profile for a given pulse shape and width. The procedure can be applied to optimize the design of impedance transformers used in petawatt-class pulsed-power accelerators.

Transmission-line transformers in multilayered high-dielectric-constant thin-film structures

In this paper, we propose a planar transmission-line impedance transformer (TLT) with a multilayered configuration obtained by deposition of high-dielectric-constant thin films over the conductors printed on conventional bulk substrates. The resulting effective dielectric constant is very high, the dispersion is very low, and the cutoff frequency of the higher-order modes is significantly increased. The theoretical behavior of this device is investigated using the Ansoft's HFSS simulator and the results are compared to those obtained for a CPW TLT printed on ϵr = 80 conventional bulk substrate. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 290–293, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21149

General design equations, small-sized impedance transformers, and their application to small-sized three-port 3-dB power dividers

In this paper, design equations for three-port power dividers have been derived. These design equations are available for both arbitrary power divisions and arbitrary termination impedances, and many sets of design equations are possible. Therefore, the design equations may be called general design equations and an arbitrary design impedance A is introduced to describe them. On the basis of the derived general design equations, a coplanar three-port power divider with a power split ratio (3 dB) terminated by 50, 60, and 70 /spl Omega/ is designed with A=33.33 /spl Omega/, so that a commercially available resistor 100 /spl Omega/ can be used for the isolation resistance. Additionally, to reduce the size of transmission-line impedance transformers, two types of small-sized impedance transformers are designed, named a constant VSWR-type transmission-line impedance transformer (CVT) and a constant conductance-type transmission-line impedance transformer (CCT) and compared with conventional reduced-sized impedance transformers. These impedance transformers are designed in the low-Q region on the Smith chart. Therefore, they show wide-band properties. To make sure that the derived design equations of CVTs and CCTs are reasonable, four 1;6:1 impedance transformers, CVT 20/spl deg/, CVT 30/spl deg/, CCT 15/spl deg/, and CCT 20/spl deg/ have been fabricated in microstrip technology and measured. The measured results show the expected tendency. Based on the CVTs and CCTs, small-sized three-port 3-dB power dividers are constructed and named a constant VSWR-type three-port 3-dB power divider (CVT3PD) and a constant conductance-type three-port 3-dB power divider (CCT3PD). For the CVT3PD and CCT3PD, perfect isolation conditions are derived, and it is shown that the perfect isolation circuit (I.C) must be composed of resistance combined with capacitance or inductance in the case that the length of transmission lines is not /spl lambda//4. These I.Cs are quite different from conventional ones composed of only resistance. Finally, on the basis of the derived perfect isolation impedance, CVT3PD and CCT3PD are designed and simulated, giving the possibility that a CCT3PD can be realized with the electrical length 15.30/spl deg/ of the transmission lines.

A new, small-sized transmission line impedance transformer, with applications in high-speed optoelectronics

A small-sized transmission line transformer (TLT) which matches 50- Omega circuits to low-input resistance components, such as semiconductor lasers and PIN photodiodes, is described. This TLT is formed by different coplanar waveguide configurations and printed on a very high-dielectric constant substrate ( in /sub r/=80). This TLT considerably improves the temporal response of high-speed photodiodes as compared with the conventional coupling scheme. >

Short-Step Chebyshev Impedance Transformers

Impedance transforming networks are described which consist of short lengths of relatively high impedance transmission line alternating with short lengths of relatively low impedance line. The sections of transmission line are all exactly the same length (except for corrections for fringing capacitances), and the lengths of the line sections are typically short compared to a quarter wavelength throughout the operating band of the transformer. Tables of designs are presented which give exactly Chebyshev transmission characteristics between resistive terminations having ratios ranging from 1.5 to 10, and for fractional bandwidths ranging from 0.10 to 1.20. These impedance-transforming networks should have application where very compact transmission-line or dielectric-layer impedance transformers are desired.