Thin Film Ferroelectric Compact Branch-Line Coupler Based on D-CRLH Unit Cell and YBCO HTS Microstrip

Abstract

In this paper, two new compact branch-line couplers (BLCs) are proposed. The first is designed and implemented using D-CRLH unit cells made of copper microstrip line. The new design occupies only 52 % of the area of the conventional BLC that operates at 1.8 GHz. The structure has been fabricated and the experimental results have been compared to the simulated ones and very good agreement has been obtained. Advanced design system circuit simulator and the CST full wave EM simulator have been used to simulate the proposed BLCs. The second BLC is designed using YBCO high-temperature superconducting (HTS) microstrip rather than copper to achieve low insertion loss, and more compact size. Three cases of this coupler with different substrate materials are studied. The design of YBCO on lanthanum aluminate (LAO) substrate attains an optimum BLC performance compared to the one using D-CRLH. All parameters of the second design are enhanced compared to the first one, the insertion loss is enhanced from -0.1268 to -0.007 dB, return loss is enhanced from -35 to -41 dB, isolation is enhanced from -25 to -36 dB, and the area is reduced from 246 to 53.55 mm 2 . Moreover, the tunable frequency BLC is designed using thin film layer of BST ferroelectric material, the layer is sandwiched between the LAO substrate and HTS microstrip line, the response shows a & Siddig Gomha

A Novel Compact Broadband Quasi-Twisted Branch Line Coupler Based on a Double-Layered Microstrip Line

“…Each of the four transmission lines (TL) has a length of λ g /4, where λ g is the guided wavelength. Thereby, the dimensions of the BLC are primarily based on the operating frequency, and thus in low frequencies, the BLC extends over a large area of the host device board and hence leads to an increased size [ 4 ]. Another inherent issue with a conventional BLC is the limited bandwidth characteristics of no more than 50% that restrict their applications and require a large multi-sections circuit to gain wideband characteristics, which in turn increase the circuit’s area [ 5 ].…”

“…Many efforts have been reported that address the above limitations. For example, the concept of coupled line unit cells was introduced in [ 4 ] to create a dual composite right/left-handed (D-CR/LH) unit cell, which results in a design that has a miniaturized area of ~52% of that of a conventional BLC at 1.8 GHz with a relative bandwidth of 18%. T-shaped slots and open stubs were employed in the horizontal and vertical arms of the BLC, resulting in a 30% bandwidth improvement and a 12.3% size reduction [ 5 ].…”

“…The majority of the aforementioned prototypes were based on composite right/left-handed structures to create branch lines, which might result in unfavorable characteristics that are associated with miniaturization such as shallow return losses for input ports, poorly isolated ports, and narrow bandwidths in some cases [ 3 , 4 , 6 , 8 ]. In addition, the structures of right/left-handed transmission lines probably increase the structure’s complexity, which results in a challenging practical realization despite the overall size reduction.…”

A Novel Compact Broadband Quasi-Twisted Branch Line Coupler Based on Double-Layered Microstrip Line

“…Each of the four transmission lines (TL) has a length of λg/4, where λg is the guided wavelength. Thereby the dimensions of the BLC are primarily based on the operating 2 frequency, thus in low-frequency the BLC extend over a large area of the host device board, and hence lead to an increased size [3]. Another inherent issue with a conventional BLC is the limited bandwidth characteristics of no more than 50%, which restrict their applications and would require a large multisections circuit to gain wideband characteristics, which in turn increases the circuit's area [4].…”

“…Many efforts have been reported that address the above limitations. For example, the coupled line unit cells concept was introduced in [3] to create a dual composite Right/Left-handed (D-CR/LH) unit cell, which results in a design that has a miniaturized area of ~ 52% of that of a conventional BLC at 1.8GHz with a relative bandwidth of 18 %. T-shaped slots and open stubs were employed in the horizontal and vertical arms of the BLC, resulting in a 30% bandwidth improvement and a 12.3% size reduction [4].…”