Two-section Impedance Transformer Research Articles

Compact dual‐band five‐way Wilkinson power divider

A compact dual-band five-way Wilkinson power divider with good RF performance is presented. Two-section impedance transformers are utilised to obtain the dual-band function. To facilitate assembling the isolation resistors among outputs, a second layer is introduced. The proposed power divider works at 0.915 and 2.45 GHz with small phase and magnitude imbalances.

Wideband Two-Section Impedance Transformer With Flat Real-to-Real Impedance Matching

This letter presents the design of an impedance transformer with wideband, maximally flat real-to-real impedance matching. The design formulas for two-section quarter-wave transformer are presented and exact solutions for transmission lines' parameters are derived in explicit form for any impedance transformation ratio. The results of this study are useful for a number of practical design problems, especially power amplification circuits. To validate the design formulas, three impedance transformers terminated in a fixed impedance of 50 $\Omega$ and three target impedances of 100, 150, and 200 $\Omega$ are fabricated and measured. Measurements show a good agreement with theory and simulations.

Bandwidth improvement of rat-race couplers having left-handed transmission-line sections

A novel broadband rat-race coupler has been investigated. The coupler utilizes an artificial left-handed transmission line section for broadband phase response realization. Moreover, a narrowband model of left-handed section has been shown to prove the couplers equivalent circuit at the center frequency. To broaden the operational bandwidth multisection quarter-wave transformers have been proposed. The exemplary rat-race coupler with two-section impedance transformers has been designed and manufactured. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:341-347, 2014.

A submillimetre-wave SIS mixer using NbN/MgO/NbN trilayers grown epitaxially on an MgO substrate

We have designed, fabricated and tested a quasi-optical superconductor–insulator–superconductor (SIS) mixer employing distributed NbN/MgO/NbN tunnel junctions and NbN/MgO/NbN microstriplines at submillimetre-wave frequencies. These trilayers were fabricated by dc- and rf-magnetron sputtering on an MgO substrate at ambient temperature so that the NbN and MgO films were grown epitaxially. Our SIS mixer consists of an MgO hyperhemispherical lens with an antireflection cap and a self-complementary log-periodic antenna made of a single-crystal NbN film, on which the distributed SIS junctions and the two-section impedance transformers were mirror-symmetrically placed at the feed point of the antenna. As designed, the junctions are 0.6 μm wide and 15.5 μm long, which is sufficient to absorb the incoming signal along this lossy transmission line, assuming a current density of 10 kA cm−2. The mixer showed good I–V characteristics, with subgap-to-normal resistance ratios of about 13, although weak-link breaks were observed above the gap voltage. The minimum double side band receiver noise temperature was 334 K at 678 GHz, including the input noise of about 200 K as estimated by the standard technique. The noise temperature gradually rose to 672 K at 820 GHz. This behaviour may be caused by RF losses from the weak-link parts, due to the steps between the distributed junctions and the microstriplines being less than 1 μm wide.

Analytical derivation of a two-section impedance transformer for a frequency and its first harmonic

The feasibility of an electrically small two-section transformer (total length one-third-wavelength at the fundamental) capable of achieving ideal impedance matching at a fundamental frequency and its first harmonic is demonstrated, analytically. To achieve this, the exact solution to the resulting transcendental transmission line equations for two sections is obtained with no restrictions. The parameters of the transformer are presented in explicit closed form and are exact. The results of this study are useful for a number of practical design problems, including dual-band antennas and RF circuits in general.

Two-section impedance transformer with arbitrary length

A simple approach for matching a purely resistive load impedance to a given transmission line is presented. The parameters of the transformer can be accurately computed from presented equations. In this approach, the length of each section, as well as the characteristic impedance, can be properly chosen in order to minimize the total length of two sections while obtaining relatively wider bandwidth compared with the case of two sections of equal length. This approach provides much shorter total length and reduces the insertion loss of the matching section, while providing almost the same bandwidth property as compared with a single quarter-wavelength transformer section.