Proposed Impedance Transformer Research Articles

A compact tri‐band impedance transformer for frequency‐dependent complex loads

AbstractA compact tri‐band impedance transformer that can match the frequency‐dependent complex loads is presented in this letter. The proposed transformer is cascade of a dual‐band conductance transforming network, a dual‐band susceptance stub network and a dual‐to‐tri‐band transformer. There are four topologies of the transformer are available according to the different loads at the first frequency and the realizability of the transformer. All the parameters are acquired by solving the closed form design equations and a detailed design process is provided. The proposed design method is demonstrated through two examples, and a prototype is fabricated. Good agreement between the simulated and measured results is obtained. Compared with the existing works, the transformer not only can match the frequency‐dependent complex loads, but also obtains wide bandwidths and has a very short electrical length. In summary, the proposed impedance transformer is very suitable for the design of tri‐band active circuits and systems.

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.

Flexible ultra‐high transformation ratio‐based dual‐band impedance transformer and its applications in a T‐junction power divider

A design scheme is presented for an all-pass coupled-line (APCL)-based dual-band impedance-matching network. Salient features include a highly flexible frequency ratio (r) (high of 15 and low of 1.2) and impedance transformation ratio (k) (high of 9 and low of 0.2) simultaneously at two arbitrary, uncorrelated frequencies of interest. The design strategy consists of two APCL sections and a stub that prove to be simple and easy to prototype. Detailed mathematical modelling and graphical interpretations have been presented. Closed-form design equations have been developed and backed up with design examples. Two dual-band T-junction power dividers (TPDs) have been designed to demonstrate the application of the proposed impedance transformer at two widely separated frequencies. RO4350 B- and RO5880-based prototypes have been fabricated for both the matching network and the TPD to validate the proposed theory. The measurement results demonstrate an achievable frequency ratio of 15 and an impedance transformation ratio of 9 in simultaneous operation mode.

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.

Realization of Extremely High and Low Impedance Transforming Ratios Using Cross-Shaped Impedance Transformer

In this brief, the design methodology of microstrip impedance transformers with extreme (i.e., extremely high and extremely low) impedance transforming ratios is proposed by deploying the cross-shaped structure (CSS) configuration. The proposed impedance transformer can significantly eliminate the line width limitation of traditional quarter-wave impedance transformer and hence an extremely wide range of impedance transformation can be easily realized. At the same time, the impedance transformer provides a good frequency selectivity, especially in the narrowband regime. To demonstrate the outstanding performance of proposed CSS impedance transformer, two examples, with the load-to-source impedances of 2000-to-50 $\Omega $ and 5-to- $50~\Omega $ , respectively, are presented and prototyped. The measurement results are in good agreement with the simulated counterparts and hence, the outstanding performance of extreme impedance transforming ratios is validated.

Synthesis design of a wideband impedance transformer consisting of two‐section coupled lines

An impedance transformer employing two-section coupled lines is presented in this study, which can achieve a wide operating band or passband with three reflection zeros. A direct synthesis approach is proposed and applied to the design of this transformer with the prescribed Chebyshev-function frequency response. If the impedance–transformation ratio, passband return loss (RL), and operating bandwidth are properly specified, all the required design parameters of this transformer can be explicitly gained. Furthermore, a special region for realisable impedance–transformation ratio and operating bandwidth with respect to the passband equal-ripple RL is extensively investigated. As such, various sets of design curves are numerically derived and graphically demonstrated for synthesis design of authors’ proposed impedance transformer. As an example, a 50–25 Ω impedance transformer with the 50% fractional bandwidth and 20 dB passband RL is designed, fabricated, and measured to confirm the theoretical predictions in the experiment.

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.

A COUPLED-LINE BASED L-SECTION DC-ISOLATED DUAL-BAND REAL TO REAL IMPEDANCE TRANSFORMER AND ITS APPLICATION TO A DUAL-BAND T-JUNCTION POWER DIVIDER

This paper presents a dual-band impedance transformer for real source and load impedances that is capable of providing matching at two arbitrary frequencies. There are two possible configurations of the proposed technique, and both the configurations are simple and possess flexibility to cater to wide range of impedance environments. A very useful feature of the design is its inherent ability to provide DC isolation. A prototype, which works at 1 GHz and 2 GHz, fabricated using Roger's RO4350B laminate validates the proposed design with a good match between theoretical and experimental results. In addition, a dual-band T-junction power divider is reported to demonstrate the usefulness of the proposed impedance transformer.

Designs of bandwidth-controllable impedance transformers using dual transmission lines

The technique of dual transmission lines is applied to replace quarter-wave transformers for impedance transformation. By varying the electrical lengths of the two lines, the bandwidths of the proposed impedance transformers are reduced and become adjustable. Two designs are presented to illustrate these characteristics. The rectangular configuration minimises the coupling between its input/output ports; whereas the ring configuration allows the two ports to be arranged in any desired directions. Simulation results indicate the larger the difference between the electric lengths of the dual transmission lines, the narrower the bandwidth of the proposed impedance transformer. The validity of the computed data is verified by measuring examples prepared for both designs. The measurement data are in close agreement with the simulation results.

A Generalized 90° Impedance Transformer with Improved Spurious Suppression for Arbitrary Real Terminated Impedances

A generalized impedance transformer for arbitrary real terminated impedances is proposed in this article. This transformer mainly features 90° phase shifting at the operating frequency, matching for arbitrary real terminated impedances, and improved spurious suppression. It consists of two-section transmission lines and three parallel transmission-line stubs. By equating the ABCD matrixes of the proposed impedance transformer and conventional quarter-wavelength impedance transformer, closed-form design equations are obtained as a final analytical design approach. Several numerical and measured microstrip transformers with improved spurious suppression are presented. Finally, experimental performances verify this generalized structure and the proposed rigorous design equations.