A compact and wideband rat-race coupler using two-section ring and artificial transmission lines
- PDF / 1,053,882 Bytes
- 6 Pages / 595.276 x 790.866 pts Page_size
- 40 Downloads / 226 Views
A compact and wideband rat-race coupler using two-section ring and artificial transmission lines Sara Khanmohamadi1 • Ahmadreza Eskandari1 Received: 20 February 2020 / Revised: 15 October 2020 / Accepted: 3 November 2020 Ó Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A compact and wideband microstrip rat-race coupler employing two-section ring and artificial transmission lines (ATLs) is reported in this paper. The bandwidth is highly improved by using a two-section rat-race coupler. The physical size of the planar circuit is reduced based on the substitution of the microstrip line with an ATL. The area of the proposed design footprint is 35% of the area of the conventional similar design. The proposed coupler operates over a frequency range of 0.9 GHz to 1.85 GHz. In the desired band, the maximum measured amplitude imbalance is 0.6 dB, the phase variation is ± 7°, and the measured return loss is greater than 15 dB with isolation better than 20 dB. The prototype has been fabricated and measured, and the results are compared with the simulated data to validate the theory. Keywords Artificial transmission line (ATL) Microstrip Rat-race coupler Wideband
1 Introduction Rat-race coupler is one of the passive components that are extensively used in microwave applications. This coupler, also known as 180° hybrid coupler is a four-port network, which is commonly used in RF applications as modulators and demodulators, dividers and combiners, power amplifiers, balanced mixers, and in the feed network of antenna arrays. It can be analyzed by the even–odd mode analysis [1]. The design of rat-race couplers has been a subject of wide research over the past years. The conventional ratrace is composed of three sections of k/4 transmission lines and a section of 3k/4. It has some advantages, such as its simple design and a high degree of isolation between the input ports. It also has significant drawbacks, such as a relatively narrow bandwidth and a large occupied area due to the requisite 270° transmission line (TL) section. Due to the intrinsic narrowband nature of the common design, its & Ahmadreza Eskandari [email protected] Sara Khanmohamadi [email protected] 1
Department of Electrical Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran
application to wideband systems is thus limited. In the last decade, studies were mainly focused on size reduction [2–7] and bandwidth improvement [8–11] techniques. Several methods have been proposed to reduce the physical size of a rat-race coupler. Artificial transmission lines (ATLs) [12, 13], metamaterial transmission lines [14], electromagnetic-bandgap (EBG) structures [15]. Folded lines, periodic stepped-impedance resonator structure, open-circuited stubs, coupled lines, lumped elements, and fractal structures [3, 4, 16, 17] are miniaturization strategies used to reduce the occupied area of the microstrip ratrace coupler. Also, various techniques have been proposed to improve the bandwidth of the rat-race co
Data Loading...
