Compact Hybrid Coupler Research Articles

Dual-Band/Dual-Mode Rat-Race/Branch-Line Coupler Using Split Ring Resonators

A novel dual-band/dual-mode compact hybrid coupler which acts as a dual-band branch-line coupler at the lower band and as a rat-race coupler at the higher band is presented in this paper. One of the most interesting features of the proposed structure is that outputs of the proposed coupler in each mode of operation are on the same side. This unique design is implemented using artificial transmission lines (ATLs) based on open split ring resonators (OSRR). The low-cost miniaturized coupler could be operated as a dual-band 90° branch-line coupler at 3.3 and 3.85 GHz and 180° rat-race coupler at 5.3 GHz. The proposed coupler could be utilized in the antenna array feeding circuit to form the antenna beam. The structure’s analytical circuit design based on its equivalent circuit model is provided and verified by measurement results.

Dual-Polarized High-Isolation Antenna Design and Beam Steering Array Enabling Full-Duplex Communications for Operation Over a Wide Frequency Range

A new dual-polarized antenna and array are presented for In-Band Full-Duplex (IBFD) applications, offering high inter-port isolation. The single-element antenna system consists of four H-shape slots, stacked patches for wide bandwidth, and two external hybrid couplers. The multilayer antenna is well matched from about 2.1 to 2.4 GHz and provides high isolation in this frequency range in excess of 60 dB. Two different prototypes are simulated and measured to highlight the design process. In addition, a new and compact hybrid coupler with excellent phase and magnitude stability is also presented for improved antenna radiation and IBFD performances. When compared to other similar types of hybrid coupler and antenna systems, the proposed configurations are simple to manufacture, provide a higher isolation bandwidth (10%), and higher gain of 7.3 dBi with cross-polarization levels of 30 dB or lower. The single-element design was also extended to a 2×2 array and studied for different beam steering and feeding scenarios. The operating bandwidths and isolation values offered by these S-band antenna and array systems can support new data link possibilities for beam steering and future low-cost IBFD wireless networks by simple antenna fabrication.

Elliptically Bended Hybrid Ring Coupler

In this paper, a size reduced elliptically bended hybrid ring coupler is proposed with better directivity, isolation factor, coupling factor, better impedance matching and undesired signal suppression for wideband applications. The proposed elliptically bended compact hybrid coupler is desired to operate at 1.8 GHz providing wide bandwidth, better return loss, and isolation with less insertion loss where a novel gradual impedance bending technique is implemented to suppress unwanted signals.

Design and Analysis of a New Hybrid Wireless Power Transfer System With a Space-Saving Coupler Structure

This article is to present the design, analysis, and verification of a new hybrid wireless power transfer (HWPT) system, which has a space-saving coupler structure. The key of the design is to simplify the two coupling capacitor plates into one single frame-shaped plate at each side. Then, the coupling coil for inductive power transfer (IPT) is embedded into the metal frame to form a compact hybrid coupler. Meanwhile, the coupling polarity between the coils is specified to realize the superposition of the inductive and capacitive coupling. As a result, the proposed HWPT system can offer a good comprise of efficiency promotion and a space-saving coupler structure simultaneously. To illustrate the system working principles, the equivalent circuit model is first derived. Then, a detailed analysis is conducted in terms of the reflected impedance. Consequently, the mechanism of the efficiency promotion can be clearly explained. Finally, a prototype is constructed with several experiments, which validate the effectiveness of the proposed HWPT system. Results show that an efficiency increase of 14% over the pure IPT is obtained at 35-cm distance. Moreover, the effects of varying the resonant frequency are also carried out to instruct the practical system design.

Application of the Crank–Nicolson FDTD method for analysis of a wideband multi-section hybrid coupler

In this paper the Crank---Nicolson (CN) finite-difference time-domain (FDTD) method is applied for the analysis of a planar wideband hybrid coupler. The proposed method is applied for analysis of transmission lines. Stability issue is investigated for different cases, including lossless and lossy transmission lines. Sufficient conditions for unconditional stability are derived. As a practical problem, a wideband compact hybrid coupler working on 1---6 GHz frequency band is analyzed using the CN-FDTD method. Measurement results show that the proposed coupler provides coupling of 3 ± 0.8 dB with 90° ± 0.85° phase shift and demonstrate the return loss and isolation better than 16 dB over 1---6 GHz. To validate the accuracy of the method, the results of this scheme are compared with measurements and the conditional stable leap-frog (LF) FDTD method. It is observed that using the CN-FDTD, the temporal step-size can be increased up to 1500 time compared with the LF-FDTD method with still good agreement with the measured results.

Miniaturization of a 90° Hybrid Coupler with Improved Bandwidth Performance

This letter presents a compact hybrid coupler having wider bandwidth compared to a conventional 90° branch line coupler. Coupling between two closely spaced branches is utilized for the improvement. Closed form expressions are derived using a lossless transmission line theory. Further, graphs are presented to determine size of the coupler with the required bandwidth specifications. In the bandwidth calculation, input matching, isolation, phase and amplitude imbalances, all conditions are considered simultaneously. A coupler is fabricated on a 1.58 mm thick FR4 substrate. It occupies 33% area of a conventional branch line coupler. The measured fractional bandwidths for the input matching, isolation, phase and amplitude imbalance conditions are 19.6%, 12.4%, 41.9% and 35.2%, respectively, which is higher than a conventional one.

A Low-loss Phase Shifter with Harmonics Suppression Using Compact Hybrid Coupler

In this paper, a compact low-loss reflector-type phase shifter with harmonic suppression using meander T-shaped branch-line coupler is suggested. The compact coupler for the phase shifter has a size of while a conventional branch coupler has a size of . The phase shifter shows insertion losses of 0.19-0.28 dB at the center frequency of 2.1 GHz, and a measured maximum phase shift of .

Miniaturized branch-line hybrid coupler with broadband impedance matching network

This paper presents a compact broadband branch-line hybrid coupler. It is composed of a miniaturized branch-line hybrid coupler and broadband impedance matching networks. A coupled-line structure is used for the broadband impedance matching network. The branch-line hybrid coupler is realized by using high-impedance transmission lines and distributed capacitors. In order to further reduce the circuit size, the distributed capacitors are placed in the center space of the hybrid coupler and the coupled lines are effectively meandered. For validation, a prototype of the compact hybrid coupler was designed and fabricated at the center frequency of 1 GHz. For given conditions, the proposed hybrid has 29.4% bandwidth which is from 870 to 1170 MHz. Compared to the conventional 3-dB branch-line hybrid coupler, it exhibited a size reduction of 50.8% and an extended operating bandwidth of 66.7%.