Dual-band Impedance Transformer Research Articles

A 2.45/5.8 GHz high-efficiency dual-band rectifier for low radio frequency input power

This article proposes a concurrent rectifier for radio frequency (RF) energy harvesting from the popular ambient RF sources wireless fidelity (WiFi) 2.45 and 5.8 GHz bands. A voltage doubler-based converter circuit with the Schottky SMS7630 diode is used, this chosen diode has shown good results for low power levels. To ameliorate the resulting circuit, we used an interdigital capacitor (IDC) instead of a lumped component; and then we added a filter to reject the 3rd harmonics of each operating frequency. A dual-band impedance transformer with a direct current (DC) block function is used and optimized at low input power points for more harvested DC power. The final circuit was, therefore, more efficient and more reliable. The maximum conversion efficiencies obtained from the resulting circuit are about 60.321% for 2.45 GHz and 47.175% for 5.8 GHz at 2 dBm of input power. Compared to other previous rectifiers presented in the literature, our proposed circuit presents high efficiencies at low power levels and at these operating frequencies.

Dual-Band Impedance Transformer Based on General Coupled-Resonator Filter Theory

A kind of dual-band impedance transformer based on general coupled-resonator filter theory is proposed. By additionally taking impedance property of dual-mode resonator into consideration, the constructed dual-band filter could match to arbitrary required impedances. Besides different filtering specifications in two bands, different impedances in two bands can also be matched. Detailed design procedure for dual-band impedance transformer with any required different port impedances, center frequencies, bandwidths and return losses in two bands is displayed.

Mixed Dual-Band Impedance Transformer With Embedded Transmission Zero

Dual- and multi-band impedance transformers are important components in radio frequency (RF) and microwave circuits for contemporary communication systems. This brief presents a mixed transmission zero embedded dual-band impedance transformer that consists of transmission lines and lumped elements, operates at two uncorrelated frequencies. The proposed impedance transformer is appropriate for a load with frequency-dependent complex impedance. The presented transformer has the advantages of compact size and the absence of extremely high or low impedance transmission lines and stubs. In addition, the values of the transformer parameters are determined using the presented closed-form design formula. The proposed structure is validated through simulations and measurements.

A novel dual‐band highly efficient power amplifier for 5G applications

This paper presents a novel dual-band highly efficient power amplifier (PA) design for 5G applications. The presented dual-band matching network consists of an impedance tuning network and a dual-band impedance transformer. This structure can not only achieve the precise fundamental and second harmonic control at two 5G bands, but also the excellent dual-band filtering response. Compared with other dual-band PAs, it shows better frequency selectivity and wider bandwidth. For demonstration, a dual-band PA is designed, fabricated, and measured. The measured results display the power added efficiencies of 60% and 47% at 2.5 GHz and 3.5 GHz (bandwidth >150 MHz) under the saturated output power of above 40 dBm, and excellent frequency selectivity with return loss (> 14.7 dB) and stopband rejection (> 25.2 dB).

Generalized design of a versatile tri‐frequency Wilkinson power divider

This article presents the design, conceptualization, and validation of a generalized architecture for a Wilkinson Power Divider (WPD). The proposed design strategy highlights the versatility of incorporating a broad variety of dual-band impedance transformers as a part of the WPD, thereby extending its range of applications. As an example, a DC blocking variant of the proposed WPD has also been designed for demonstration. Simple closed-form design equations have been developed and validated with classical examples and case studies. Finally, two prototypes- one ordinary and another DC blocking variant have been fabricated on RO4350 (ɛr = 3.6) substrate and measured. The measurement results are well in accordance with the simulations, thereby validating the proposed design theory.

Flexible Design Scheme for a Simple Dual-Band Ultra-High Impedance Transformer and Its Application in a Balun

A dual-band impedance transformer for achieving very high impedance transformation (k) and frequency ratio (r) is presented in this paper. The design is accompanied by a thorough analysis and systematic design procedure for facilitating the rapid development of the prototypes. A number of case studies show the excellent design flexibility of the proposed design in regards to achieving ultra-high k and r. Two prototypes, with very high design specifications, working at concurrent r = 5, k = 8.04 and r = 15, k = 20 are fabricated to validate the proposed architecture and the design procedure. Subsequently, the application of the proposed impedance transformer is demonstrated in the design of a dual-band balun architecture with inherent impedance transformation capability. To evaluate the performance and the presented concept, an impedance transforming balun prototype is fabricated and the excellent agreement between the simulation and experimental results is a testament to the effectiveness of the proposed design.

A Novel Dual-Band Branch Line Coupler for Dual-Band Butler Matrix

In this brief, a novel dual-band branch line coupler (BLC) for designing a dual-band Butler matrix (BM) has been proposed. To realize the proposed BLC, a unique dual-band impedance transformer (DBIT) with a derivation of closed-form design equations, capable of performing a dual-band operation for a traditional transmission line (TL) of any electrical length, has been proposed as well. The proposed BLC is different from the existing dual-band BLCs in terms of its phase difference between the output ports, which enables it to play a role equivalent to the combination of a dual-band equal power ±90° BLC and a dual-band ±45° / ±135° phase shifter. The circuit parameters analysis of the proposed BLC versus the frequency ratio has also been studied here. To verify the design method, a dual-band BLC has been designed using Keysight Technologies’ advanced design system (ADS), implemented on a Rogers 5870 for 1 GHz and 1.76 GHz operating frequencies, and then tested.

Reply to Comments on “A Three-Section Dual-Band Transformer for Frequency-Dependent Complex Load Impedance”

The author thanks Dr. R. Sinha very much for providing detailed design equations for the proposed dual-band impedance transformer in <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> . Note that the analytical solutions for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> are very necessary, which are developed in <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> , in closed form. In fact, the generalized and closed-form solutions for this kind of impedance transformers have been published in <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> . It is very interesting that all results in <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> can be degenerated to the simple solutions in both <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> and the presented results in the comments by Dr. R. Sinha, when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In</sub> = 0 is considered in <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> .

Comments on “A Three-Section Dual-Band Transformer for Frequency-Dependent Complex Load Impedance”

In the above paper, Liu et al . proposed the dual-band impedance transformer based on three sections of the transmission line. However, there is some incorrectness in the design equations and inconsistencies in the derivations. Here, we have provided the corrected design equations.

Theory and Design of Dual-Band Microstrip Networks Using Embedded Metamaterial-Based Electromagnetic Bandgap Structures

This article examines implementations of the recently introduced metamaterial-based electromagnetic bandgap (MTM-EBG) structure, which may be embedded directly into the transmission-line (TL) segments of microstrip (MS) networks and whose dispersion properties may be accurately determined using multiconductor TL (MTL) theory. Two methods of imparting dual-band behavior to MS-based networks are introduced: utilizing stopband and passband regions of the EBG for frequency-selective signal routing, and using the phasing properties of the EBG to provide equal phase shifts at two separate frequencies. Two topological variants of the MTM-EBG are introduced and shown to provide different bandgap sizes, suiting each proposed application. A dual-band Wilkinson power divider, a dual-band quadrature hybrid coupler, and a dual-band impedance transformer are designed with embedded MTM-EBGs, which due to their ability to be realized in an entirely uniplanar form without vias and using a single dielectric layer, allow these devices to be entirely printable as well. The performance characteristics of all three devices are simulated and demonstrate excellent agreement with measurements. The design methodology is general and based on a rigorous MTL circuit model, making this approach amenable to a variety of MS networks, beyond what is presented.

Multisection branch line couplers as dual-band crossovers using coupled lines for wideband applications

This article presents multisection branch line couplers as dual-band crossovers using coupled lines (CLs) for wide bandwidth (BW) applications. The efficiency of the CL as a dual-band impedance transformer and its closed form design equations has also been explored. Specifically, dual-band crossovers having three and four sections have been designed using the advanced design system software and then implemented on a Rogers 5870 substrate with a dielectric constant of 2.33 and thickness of 0.787 mm. The designs have been developed for 1 and 2.6 GHz operating frequency bands. A much wider BW and interband suppression, of 225/218 MHz and 86.45% for the three-section prototype and 269/260 MHz and 85% for the four-section prototype respectively, have been achieved. It is concluded that the proposed crossovers exhibited a much wider BW as compared to the existing dual-band crossovers.

An analytical design method for a novel dual‐band filtering DC‐block impedance transformer

AbstractIn this paper, a dual‐band impedance transformer with filtering integration and DC‐block function is proposed for the first time. Excellent frequency selectivity is achieved by the dual‐narrowband filtering integration with two pairs of transmission zeros (TZs) at both sides of the dual passband. Using transmission‐line theory and even‐/odd‐mode analysis method, the design theory and equations are demonstrated analytically. Furthermore, the relationship between terminal impedance ratios and operating frequency ratios is analyzed, and arbitrary impedance ratios and frequency ratios can be obtained in the given constrained region. Based on a simple design flow, two examples with the same frequency ratio 1.9 but different terminal impedance ratios 1.2 and 1.6 are fabricated and measured for experimental validation. Good agreement between the simulated results and measured ones verifies the presented design method.

Design of dual/tri-frequency impedance transformer with ultra-high transforming ratio

In this article, the design of a new dual-band impedance transformer with ultra-high transforming ratio (UHTR) is presented. The closed-form expressions are derived analytically using a lossless transmission-line theory. To practically validate the proposed design concept, two examples of dual-band transformer working at smaller and larger frequency ratios are designed for different load impedance of 500, 1000, and 1500 Ω. Finally, three prototypes of dual-band transformer with UHTR are designed, fabricated, and tested. For all these prototypes, different frequency ratios (two operating frequencies can be chosen arbitrarily) are considered. The measured return loss of the prototypes is better than 15 dB at all the operating frequencies. The measured results are matched very closely with the simulated results. This design is then extended to match a complex load at two different frequencies. The multi-band characteristic is obtained by decomposing a shorted stub into a stepped impedance section of the proposed structure. With the necessary derivation and analysis, a tri-frequency matching network is designed for a transforming ratio of 10.

Transmission Zero Embedded Dual-Band Impedance Transformer With Three Shunt Stubs

This letter presents a dual-band impedance transformer with three shunt stubs. The considered load has frequency-dependent complex impedance at two uncorrelated frequencies. The functions of the three shunt stubs are compensating for susceptances at two frequencies simultaneously, generating an additional transmission zero at the desired frequency, and eliminating the need to use transmission lines with extremely high or low impedance. The required circuit parameters are all obtained using the derived analytical design formula. Simulations agree closely with measurements and validate the developed structure as well as the design process.

General Dual-Band Impedance Transformer With a Selectable Transmission Zero

This paper presents general design formulas for a dual-band impedance transformer with an inherent and selectable transmission zero. The inherent transmission zero can block unwanted signal or interference and improve the overall circuit performance by suppressing spurious response and enhancing selectivity. The considered load has unequal complex impedances at two uncorrelated frequencies. The proposed transformer consists of three sections of transmission lines and two shunt stubs. The parameters of each transmission line and stub are obtained using the derived analytical formulas without any time-consuming try-and-error procedure or numerical solution. The proposed design formulas reduce the need to use a transmission line with extremely high or low impedance. Two impedance transformers are designed and fabricated. Good agreement between numerical and measured results validates the proposed design formulas.

Synthesis of a miniaturized dual‐band 3‐DB hybrid coupler through a general three‐step optimization process

ABSTRACTSynthesis method for a novel dual‐band hybrid coupler (DBHC) is presented in this letter. The proposed DBHC is built up using a novel dual‐band impedance transformer (DBIT). The DBIT is made up of a single kernel circuit unit cell with uniform transmission lines attached to its two ends. A system of nonlinear equations dominating the DBIT performance is first established and then successfully solved with numerical method. Design charts are provided for determining the feasible DBIT parameters. With the DBIT theoretical solutions, a microstrip DBHC centered at 2.4/5.8 GHz is practically implemented, of which layout parameters are effectively resolved through a sequential three‐step optimization design process, and its compact size as well as good dual‐band operational performance has been demonstrated by fabrication and measurement, validating the proposed synthesis method. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2057–2062, 2016

A novel three-dimensional dual-band balun with frequency-independent phase difference and complete ground

A novel three-dimensional (3D) dual-band balun employing the double-sided parallel-strip line (DSPSL) with inherent impedance-transforming capability and complete ground is presented in this paper. The proposed balun is mainly composed of two mutually perpendicular printed circuit boards (PCBs), one of which is a horizontal feeding plane with a slender slot and the other of which is a mounted board vertical to the former.An unbalanced input port and two balanced output ports are totally located at the feeding plane. Utilising the configuration of DSPSL, two different dual-band impedance transformers of two sections are placed in the top and bottom layers of the vertical mounted board respectively. Thus, the transformers are applicable to transform impedances at two frequencies simultaneously. Furthermore, the 180° phase difference is frequency-independent, which facilitates the broadband operation. For verification, two numerical examples with different frequency ratios are designed and simulated, one of ...

Synthesis of a miniaturised wireless local area network dual‐band microstrip Wilkinson power divider through a general three‐step optimisation process

Synthesis method for a novel dual-band Wilkinson power divider (DBWPD) is presented in this study. The proposed DBWPD is constructed using a novel dual-band impedance transformer (DBIT). The DBIT is made up of a kernel circuit unit cell with uniform transmission lines attached to its two ends. A non-linear system of equations ruling the DBIT performance is first built up and then successfully solved with numerical method. Design charts are provided for determining the feasible DBIT theoretical parameters. With the DBIT theoretical solutions, a microstrip DBWPD operative at 2.4/5.2 GHz is practically implemented, of which layout parameters are effectively resolved in a sequential three-step optimisation design process, and its compact size as well as good dual-band operation performance has been demonstrated by fabrication and experimental tests, confirming the proposed synthesis method.

&lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$\Pi$&lt;/tex&gt;&lt;/formula&gt;-Model Dual-Band Impedance Transformer for Unequal Complex Impedance Loads

This letter presents a $\pi$ -model dual-band impedance transformer which can match two unequal arbitrary complex loads at two frequencies. The required nonlinear simultaneous equations are derived to obtain the physical parameters of transmission lines and stubs. Return loss for the proposed matching circuit is measured to validate the results of the presented structure simulations. Excellent agreement between analytical and measured results confirms the proposed structure.

Analytical design of dual‐band impedance transformer with additional transmission zero

This study presents a three-stage dual-band impedance transformer, capable of providing good match between two circuit modules and generating an additional and selectable transmission zero. The input impedances of the output circuit module are unequally complex at two uncorrelated frequencies. Among the three stages of the proposed transformer, the first stage transforms the complex impedance of the load to become equal resistance at the two frequencies. The second stage cancels out the susceptance produced by the first stage at the two frequencies concurrently and generates the desired transmission zero. The final stage transforms the equal and real impedance to the input circuit module. This study provides analytical formulation of each stage to obtain the required circuit parameters instead of numerical solution or optimisation. The proposed impedance transformer has up to four configurations, subsequently decreasing the possibility of using an extremely narrow or wide transmission line. Simulations and measurement demonstrate the reliability of the proposed structure and design formula. The simulation results agree measured results well, and comply with the specifications.