Branch-line Hybrid Coupler Research Articles

Compact Antenna Array With Port Decoupling for LTE-Standardized Mobile Phones

A compact dual-element antenna has been designed at 710 MHz for newly emerging long-term evolution (LTE) personal wireless communication standard applications. The proposed antenna consists of two printed meander-line monopoles with edge-to-edge separation of nearly ?/45. The antenna elements are printed on FR-4 substrate and are located at the top edge of the ground plane measuring 50 × 87 mm2. An LC-components-based branchline hybrid coupler is used to decouple the antenna elements. The prototype antenna has been evaluated through the scattering parameters, radiation patterns, envelope cross correlation, and the channel capacity measurements. Isolation between the ports is better than 35 dB with matched ports at 710 MHz. The antenna offers reasonable multiple-input-multiple-output (MIMO) performances that make it suitable for LTE-standardized mobile phones.

Design of miniaturised branch-line and rat-race hybrid couplers with harmonics suppression

Shunt open-stubs are used to design reduced size branch-line and rat-race couplers with suppressed harmonics. The band stop response of shunt stubs has been utilised to suppress the harmonics. Design graphs are presented to ease the design process. Even–odd mode analysis is carried out to investigate in-band and out-of-band performances of the couplers. Two branch-line and one rat-race couplers have been fabricated. Experimental results of the designed couplers agree well with the theoretical predictions. For the branch-line coupler, up to fifth harmonic suppression and 37% size reduction are obtained. Up to seventh harmonic suppression and 69% size reduction are obtained for the rat-race coupler.

Symmetric Reverse-Coupling Waveguide Orthomode Transducer for the 3-mm Band

We describe the design, construction, and performance of a waveguide orthomode transducer (OMT) for the 3-mm band (84-116 GHz). The OMT is based on a symmetric backward coupling structure and has a square waveguide input port (2.54 mm times 2.54 mm) and two single-mode waveguide outputs: a standard WR10 rectangular waveguide (2.54 mm times 1.27 mm), and an oval waveguide with full-radius corners. The reverse coupling structure is located in the common square waveguide arm and splits one polarization signal in two opposite rectangular waveguide sidearms using broadband -3-dB .E-plane branch-line hybrid couplers. The device was optimized using a commercial 3-D electromagnetic simulator. The OMT consists of two mechanical blocks fabricated in split- block configuration using conventional CNC milling machine. From 84 to 116 GHz, the measured input reflection coefficient was less than -17 dB, the cross polarization was less than -30 dB, the isolation between the outputs was greater than 50 dB, and the insertion loss was less than 0.35 dB at room temperature for both polarization channels. The device is suitable for scaling to higher frequency.

A Design Methodology for Miniaturized 3-dB Branch-Line Hybrid Couplers Using Distributed Capacitors Printed in the Inner Area

This paper proposes a methodology to design and optimize the footprint of miniaturized 3-dB branch-line hybrid couplers, which consists of high-impedance transmission lines and distributed capacitors. To minimize the physical size of the coupler, the distributed capacitors are placed within the empty space of the hybrid. The proposed design methodology calls for the joint optimization of the length of the reduced high-impedance transmission lines and the area of the distributed capacitors. A prototype at S-band was designed and built to validate the approach. It showed a size reduction by 62% compared with the conventional 3-dB branch-line hybrid coupler while providing similar performance and bandwidth.

The Design of Low LO-Power 60-GHz CMOS Quadrature-Balanced Self-Switching Current-Mode Mixer

This letter describes the analysis and measurement of a complementary metal-oxide semiconductor (CMOS) quadrature-balanced current-mode mixer with a 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> branch-line hybrid coupler and self-switching current-mode devices. The proposed mixer, using 0.13 mum 1P8M CMOS technology, can downconvert a 60 GHz RF signal to a 2 GHz intermediate frequency (IF) signal, with a local-oscillator power of 0 dBm at 58 GHz. In the design, the mixer had a single-end conversion gain of 1 dB and an input-referred 1 dB compression point of 2 dBm. The LO-RF isolation of the mixer can achieve -37 dB while using 3 mA from a supply voltage of 1.2 V.

Application of Composite Right/Left Handed (CRLH) Transmission Lines based on Complementary Split Ring Resonators (CSRRs) to the Design of Dual-Band Microwave Components

In this letter, composite right/left handed transmission lines based on complementary split ring resonators are applied to the design of dual-band microwave components. Specifically, impedance inverters operative at two (arbitrary) different frequencies (one of them within the left-handed band and the other within the right-handed band) are designed and applied to the implementation of a dual-band branch line hybrid coupler. The characterization of this device reveals good performance and dual-band operation. The fabricated device is small, fully planar, and vias are not required.

Miniaturization and harmonic suppression branch-line coupler using short-circuit anti-coupled line

In this article, short-circuit anti-coupled lines structure is applied to design a miniaturised microstrip branch-line hybrid coupler. The proposed structures can achieve both a significant reduction of size and harmonic suppression. As the short-circuit anti-coupled lines structure is constructed entirely from microstrip lines, the couplers can be easily fabricated using conventional printed-circuit board process. The performance of the proposed couplers is as good as that of the conventional structures and deep harmonic suppression in addition. The design and simulation have been performed using full-wave analysis based on ADS Momentum.

A Quadrature Radar Topology With Tx Leakage Canceller for 24-GHz Radar Applications

A quadrature radar topology with a Tx leakage canceller is presented. The canceller is composed of four branch-line hybrid couplers, a 90deg delay line, and a Wilkinson combiner. It has high Tx-to-Rx isolation and wide bandwidth characteristics. The isolation is 35.27 dB at 24 GHz and does not drop below 30 dB over a 2-GHz bandwidth. Given that the isolation of the branch-line hybrid coupler is 21.5 dB, the enhancement of the isolation is expected to be 13.77 dB. A quadrature Doppler radar front-end with the canceller was implemented. The noise level in the mixer output is lower by 9 dB compared with that of a conventional quadrature radar. This radar can measure speed as low as 0.76 mm/s, which correspond to a 0.12-Hz Doppler shift. It is also able to detect signs of the Doppler shift from a moving target due to its quadrature topology.

A new active RF phase shifter using variable gain, drain Voltage controlled PHEMTs:A 2.4-GHz ISM implementation

Phase shifters operating at RF bands are an essential component of phased and adaptive arrays circuits. In this letter, an active phase shifter is proposed, using vector summing of an in-phase and a quad-phase replica of the incoming signal. The proposed scheme was designed and implemented using a Wilkinson power combiner/divider, a branch line hybrid coupler and single-stage variable gain amplifiers (VGAs), achieving continuous phase shift within the range of [0/spl deg/, 90/spl deg/]. The manufactured prototype is suitable for WLAN operations in the 2.4-GHz ISM band. Details of the phase shifter design and experimental results are presented.

Reflection-Type Ferroelectric Phase Shifter With Defected Ground Structure

In order to obtain a low-loss ferroelectric phase shifter, we were designed and fabricated the reflection-type ferroelectric phase shifter with the defected ground structure (DGS) resonators. The ferroelectric phase shifter is consisted of a 3-dB 90° branch-line hybrid coupler and terminated reflective circuit with tunable ferroelectric DGS resonator which can provide a high Q resonator characteristic at high frequencies. The design parameters of equivalent circuit for the tunable DGS resonator are derived by circuit analysis method and three-dimensional full wave finite element method. At 13.5 GHz, the fabricated phase shifter exhibited an insertion loss of better than 3.4 dB.

Optimum Reflection-Type Phase Shifter Using (Ba,Sr)TiO3 Thin Film

In this paper, in order to obtain a large differential phase shift with a little change in applied voltage, a ferroelectric reflective load circuit has been designed on top of barium strontium titanate (Ba,Sr)TiO3 [BST] thin film. The design of the ferroelectric reflection-type phase shifter is based on a reflection theory of terminating circuit, which has a reflection-type analogue phase shifter with two ports terminated in symmetric phase-controllable reflective networks. To achieve large amounts of phase shift in low bias-voltage range, the effects of change of capacitance and transmission line connected with two coupled ports of a 3-dB 90° branch-line hybrid coupler have been investigated. A large phase shift with a small capacitance change in the parallel terminating circuit has been demonstrated in the paper.

An annular-ring microstrip antenna fed by a co-planar feed circuit for mobile satellite communication use

A new configuration of circularly polarized annular-ring microstrip antenna (ARMSA) fed by a branch-line hybrid coupler placed at the inner part of the ARMSA and its design method using an equivalent circuit are presented. Since the ARMSA has a narrow bandwidth and high-input impedance, a parasitic element placed above the ARMSA is employed for not only obtaining a broadband characteristic, but decreasing the input impedance down to 50 /spl Omega/. A hybrid coupler to generate circular polarization, therefore, can be connected to the co-planar space of the ARMSA directly without a large-size matching circuit and a very low profile and simple structure can be achieved. The ARMSA is excited at the TM/sub 21/ mode to produce a conical pattern, which has a high gain in a low-elevation angle for mobile satellite communications. An effective design method using the equivalent circuit is indicated and, as a result, it is obvious that a broadband characteristic is obtained when each resonant frequency of the ARMSA and parasitic element is identical. Experimental results in the L-band showed satisfactory characteristics for vehicle antennas.

Uniplanar hybrid couplers using asymmetrical coplanar striplines

This paper presents four new uniplanar 3-dB hybrid couplers using asymmetrical coplanar strips (ACPSs) for microwave integrated circuit (MIC) and monolithic MIC (MMIC) applications. Experimental results show that the standard (1.5 /spl lambda//sub g/ circumference) uniplanar 180/spl deg/ hybrid-ring coupler has 3.5/spl plusmn/ 0.4 dB coupling, greater than 21-dB isolation, and greater than 23.4-dB return loss over a 25% bandwidth centered at 3 GHz. The 180/spl deg/ reverse-phase hybrid-ring coupler (1.0 /spl lambda//sub g/ circumference) provides better performance as compared to conventional microstrip hybrid couplers. This circuit has a bandwidth of more than one octave from 2 to 4 GHz with /spl plusmn/0.4-dB power dividing imbalance and /spl plusmn/4/spl deg/ phase imbalance. The 180/spl deg/ reduced-size reverse-phase hybrid-ring coupler (0.8 /spl lambda//sub g/ circumference) maintains the performance of the 180/spl deg/ reverse-phase hybrid coupler with the advantage of smaller size. This circuit also has a bandwidth of more than one octave from 2 to 4 GHz with /spl plusmn/0.3-dB power dividing imbalance and /spl plusmn/3.1/spl deg/ phase imbalance. A new 90/spl deg/ 3-dB branch-line hybrid coupler is also introduced. Experimental results show the insertion loss of this component to be 0.5 dB at 3 GHz, and also greater than 15.3-dB isolation and 17.1-dB return loss over a 10% bandwidth centered at 3 GHz. The circuits were designed and simulated with Sonnet electromagnetic-circuit solver software. The measured results agree well with the simulations.

Endless Phase Shifter—Analysis and Design for 7.4 to 7.7 GHz Band

Endless phase shifters (EPS) are used in space diversity combining networks of digital microwave communication systems. This paper presents detailed analysis of branch-line hybrid coupler, using ABCD matrix, which is a basic block for EPS. Design and development of mixers and control circuits required for the EPS are described. A prototype phase shifter developed in the frequency band 7.425 to 7.725 GHz is also described.

Integrated Balanced BPSK and QPSK Modulators for the Ka-Band

Microwave integrated circuit (MIC) balanced biphase-shift-keying (BPSK) and quadri-phase-shift-keying (QPSK) modulators have been achieved in the 27-GHz band. The modulators are fabricated using a combination of microstrip lines and slot lines, viz., tow-sided MIC. The diodes used are beam-lean Schottky-barrier diodes. Balanced BPSK modulation is performed by path-switching and mode transformation from the slot line to microstrip lines. The insertion loss is 2.2 dB at a carrier frequency of 27 GHz. The phase error and the amplitude deviation are less than 1° and 0.5 dB, respectively. The QPSK modulator consists of two BPSK modulators, a power divider, and a branch-line hybrid coupler. The configuration of the modulator is the parallel-connected type. The insertion loss is 6.3 dB at a carrier frequency of 27 GHz. The phase error is less than 2°, and the rise time and fall time of the modulated earner are less than 300 ps. The isolation between the carrier input port and the QPSK modulated earner output port is greater than 25 dB. These modulators can be extended to the millimeter-wave band.

A Fast-Switching Low-Loss 12-GHz Microstrip 4-PSK Path Length Modulator

A 4-PSK microstrip modulator operating at data rates of up to 800 Mbits/s at 12 GHz is described. The circuit is made of two cells in series. Each cell consists of a 3-dB branch-line hybrid coupler and two BTL p-i-n diodes. One cell provides 0° or 90° phase shifts, and the Other 0° or 180° phase shifts, so that four carrier phase values are obtained by appropriately exciting the two cells. The switching time of each cell is 200 ps. Simultaneous switching of both cells increases the switching time to a maximum value of 400 ps. The phase waveforms are nearly rectangular at the above-mentioned data rates. RF insertion loss is 1 dB ± 0.1dB for the four phase values over the 11.7-12.2 GHz frequency band.

Hybrid Branchline Couplers -- A Useful New Class of Directional Couplers

The hybrid branchline coupler consists of two transmission lines connected alternately by /spl lambda//4 shunt and series branches. The analysis of this structure leads to a class of directional couplers of which the parallel transmission-line and the de Ronde strip-slot types may be regarded as special cases. From the precise design data thus available, a number of 3-dB strip-slot couplers have been built in C band and X band with a performance close to the predicted one.