Quadrature Directional Couplers Research Articles

Design and Implementation of a 2.4-GHz Fully Integrated Butler Matrix for Smart Antenna System

This work proposes and analyzes a low-cost fixed microstrip beamforming system based on a uniform linear array with four rectangular patch antennas controlled by a Butler matrix that operates in the 2.4 GHz ISM band. A 4×4 Butler matrix consisting of four hybrid quadrature directional couplers, two crossovers, and two 45° phase shifters was designed and implemented to control the beam direction of the entire system. Similarly, a comparative study is performed between two different antenna arrays, the first consisting of a conventional linear antenna array and the second antenna array consisting of four patch antennas loaded with metamaterial structures on the ground plane. Finally, the electrical performance of both smart beamforming systems was evaluated, and their potential application as a wireless power transmitter was evaluated. Four beams with distinct orientations were created in each situation. The smart antenna based on a conventional array has a higher gain, while the smart antenna based on metamaterial structures has a higher HPBW.

Simulation Design of 3dB Orthogonal Directional Coupler

Directional couplers can isolate, mix, and orient signals, and play an important role in RF circuits. In this paper, the quadrature coupler is firstly analyzed theoretically. According to the results of the theoretical analysis, a microstrip 3dB quadrature directional coupler with a new structure based on 2.2GHz is designed using ADS after the design objective is given. After repeated simulation optimization, the coupling degree is optimal.

Designing a downsized quadrature directional coupler

To miniaturize directional couplers, the replacement of their quarter-wave sections with electrodynamic structures with equivalent characteristics at smaller physical dimensions is used. It is shown that the structures used have filtering properties and act as low-pass filters. It is set at what cutoff frequency the low-pass filters must be calculated to obtain a phase shift of 90 degrees.

Broadband Equal-Split Directional Couplers Composed of Cascade- and Tandem-Connected Coupled-Line Sections Having Unequal Lengths

A new concept of broadband equal-split coupled-line directional couplers is proposed. The proposed couplers are based on coupled-line sections, all having the same coupling coefficient, and feature frequency characteristics similar to the ones obtained for classic symmetrical three-section coupled-line couplers. It is shown that appropriate cascade- and tandem-connected coupled-line sections, having all the same coupling coefficients and different electrical lengths allow for achieving equal power split in a broadband frequency range together with the quadrature differential phase response. Therefore, a very flexible design process is possible, in which directional couplers with different bandwidths and coupling imbalances can be realized by changing solely the electrical lengths of the coupled-line sections. Moreover, the proposed networks require significantly lower coupling coefficients and feature slightly shorter overall electrical lengths than their classic counterparts. The theoretical analysis of the proposed circuits is shown in the paper and is followed by the design and measurements of two broadband equal-split quadrature directional couplers operating at the center frequency of 2 GHz.

Realization of High-Performance Broadband Quadrature Directional Couplers in UMS PH25 Technology

The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems have to be overcome to achieve the high-performance of the resulting integrated couplers, i.e., the realization of appropriate coupling together with appropriate characteristic impedances, and the equalization of inductive and capacitive coupling coefficients that are inherently different in inhomogeneous dielectric structures. Three different solutions that allow for achieving strong coupling in the selected UMS PH25 process were selected and experimentally investigated, showing the possibility of such circuits’ realization. In each of the presented integrated couplers, capacitive compensation techniques were applied for coupling coefficients’ equalization.

Broadband Integrated <inline-formula> <tex-math notation="LaTeX">$8 \times 8$ </tex-math> </inline-formula> Butler Matrix Utilizing Quadrature Couplers and Schiffman Phase Shifters for Multibeam Antennas With Broadside Beam

A novel realization of a broadband $8 \times 8$ Butler matrix having phase progressions 0°, ±45°, ±90°, ±135°, and 180° has been proposed. The presented network is composed of coupled-line 3-dB/90° directional couplers and Schiffman phase shifters that ensure its broadband amplitude and phase characteristics. The proposed solution allows for a fully planar realization without any interlayer connections, which has been achieved by both rearrangement of the matrix layout and realization of the selected crossovers as tandem connections of quadrature directional couplers. The proposed concept has been verified experimentally by the design of a Butler matrix operating within 2.5–3.5 GHz and applied in a multibeam antenna array with broadside beam.

Phase Property of Central-Symmetric Four-Ports Applied to Quadrature Directional Coupler Design in Asymmetric Coupled-Line Technology

Properties of ideally matched lossless four-port networks having central symmetry have been investigated. It has been shown that such networks feature ideal quadrature differential phase characteristics. It is shown that this unique property can be utilized for phase improvement of asymmetric coupled-line directional couplers. The presented theoretical investigation has been proven by measurements of two different directional couplers with a central symmetry designed in technology of multilayer asymmetric coupled lines.

Electromagnetic Devices Applications of EBG for Systems Communications

This paper presents the study and applications of EBG (Electromagnetic Band Gap)/PBG (Photonic Band Gap) substrates, of planar microstrip structures, including quadrature directional couplers, rat-race (ring coupler) and impedance transformers. Through specific programs developed in FORTRAN PowerStation, the frequencies and couplings for each structure are obtained. Also are used the PACMO—Computer Aided Design in Microwave program developed by H.C.C. Fernandes. Results of the dimensions and coupling of these devices, varying the frequency band (cellular communication and Wimax systems) and permittivity of the substrate, are obtained, comparing the results of conventional materials with EBG/PBG materials in the s and p polarizations.

An Novel Compact Quadrature Hybrid Using Broadside-Coupled Meander Lines

In this paper, we present a novel compact 3-dB quadrature directional coupler by introducing Hilbert curve to the conventional meander line structure. The proposed coupler uses a modified broadside coupled meander lines featuring Hilbert curves to achieve a smaller size. The structure of the coupler is suitable for multilayer printed circuit board (PCB) implementation. The proposed coupler with an operation range of 470 MHz–860 MHz is verified by the accordance of simulation and measurement with a measured return loss and isolation better than 19 dB and exhibiting a coupling of 3.4±0.5 dB in the working frequency range. The dimension of the manufactured coupler is 11.50 mm × 8.90 mm × 1.70 mm. It is the smallest coupler to the authors' knowledge in the frequency range of 470–860 MHz.

Analysis and design of a wideband lumped-element quadrature directional coupler for complementary metal-oxide semiconductor implementation

This study proposes a new wide band quadrature coupler structure using a lumped-element technique. The theoretical operating conditions of the proposed structure are also analysed. The operating bandwidth is extended and the phase shift difference error is reduced by introducing two matching frequency points. When the designed centre frequency is 6 GHz, a theoretical calculation shows that the operating bandwidth is 2 GHz and the phase shift error ranges from −5.9 to 1.76°. A coupler with 6 GHz centre frequency is also designed in a 0.13 µm CMOS process and simulated using Cadence Spectre. The active area of the coupler is 560 µm×640 µm. The post-layout simulation shows that the operating bandwidth has strong tolerance to the process variations.

Broadband quadrature coupler with slotted ground plane

AbstractThe design of an edge‐coupled quadrature directional coupler, which has a broadband performance and relaxed coupled‐line spacing, is presented. A slotted ground plane is used underneath the coupled region in order to relax the requirement for a narrow slot between the coupled lines. The simulated and measured results show that the designed coupler exhibits a coupling of 3 ± 1 dB across the band 3.8 GHz to 9.8 GHz, when the spacing between the coupled lines is 0.12 mm. Without the slot in the ground plane, the spacing should be less than 0.001 mm to achieve the same value of coupling across that band. This broadband coupling is accompanied by an isolation and return loss in the order of 13 dB or better across the band 3–10 GHz. The designed device has a compact size with a dimension of 30 mm × 20 mm. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 328–331, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23080

Optimum compensating susceptance and position for quadrature directional coupler

AbstractThe optimum susceptance and position for compensation of the match and isolation performances of a quadrature directional coupler are perspicuously derived in this paper. Furthermore, various frequency responses of the coupler with either capacitive or inductive loading are given to elucidate the characteristics of a susceptance‐loaded quadrature directional coupler as well. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 90–95, 2001.

Quadrature directional couplers using multisection coupled lines

New structure and design methods of directional couplers that can achieve both loose coupling and tight coupling by use of multisection coupled lines are presented. Output voltage formulas at each port are derived from the coupled-line theory. Measured results agree very well with predicted ones. Since the proposed couplers are very small in size and have suitable shape for high-density integrated circuits, they have potential applications in portable terminals for mobile communication systems.

Two-octave bandwidth monolithic analog phase shifter

The cascaded-match reflection-type phase shifter (CMRTPS) was recently introduced to utilize the full bandwidth of its 3-dB quadrature directional couplers. A monolithic realization of the CMRTPS is presented that maintains a high level of performance over two octaves, while using experimental one octave bandwidth offset multilayer folded directional couplers. Standard GaAs foundry processing was used to fabricate the MMIC. At the 10-GHz center frequency, the measured relative phase shift varied from 0 to 98 degrees , with a decreasing bias potential from 0 to -10 V. A maximum r.m.s. phase error of +or-2.8 degrees is maintained across the 4.4 to 16.1 GHz frequency range, for all bias levels.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Synthesis, design, and construction of ultra-wide-band nonuniform quadrature directional couplers in inhomogeneous media

A computer-aided synthesis design procedure is given for nonuniform quadrature directional couplers in inhomogeneous media. A wiggly geometry is used which effectively slows the odd-mode phase velocity to match the even-mode phase velocity. The wiggly geometry results in improved isolation and increased effective dielectric constant. This technique provides a shorter coupler length due to increased effective dielectric constant. Cubic splines of strip width, strip spacing, and wiggle depth as functions of coupling coefficient are computed using static capacitances of uniform coupled lines. These functions are then used as synthesis functions to evaluate the continuous physical parameters of nonuniform coupled lines by using the continuously varying coupling coefficient. A nonuniform interdigitated coupler is introduced to realize the tight coupling values. >