Branch-line Hybrid Research Articles

A miniaturized MMIC analog phase shifter using two quarter-wave-length transmission lines

This paper describes a miniaturized monolithic-microwave integrated-circuit (MMIC) analog phase shifter using two quarter-wave-length transmission lines. A conventional analog phase shifter employs an analog phase-shifter topology using a 3-dB 90/spl deg/ branch-line hybrid requiring four quarter-wave-length transmission lines. Thus, in the first stage of our study, we present a new analog phase-shifter topology using only two quarter-wave-length transmission lines. The phase shifter here has only one-half as many transmission tines as a conventional analog phase shifter using a 3-dB 90/spl deg/ branch-line hybrid, and the circuit can be miniaturized to less than one-fourth as compared to the conventional analog phase shifter. Furthermore, we show that the operating frequency range of the phase shifter is very wide and can obtain large phase variation with small capacitance variation. Next, an experimental Ku-band MMIC analog phase shifter is presented. A phase shift of more than 180/spl deg/ and an insertion loss of 3.6/spl plusmn/1.1 dB are obtained at the frequency range from 12 to 14 GHz. The chip size of the experimental MMIC phase shifter is less than 3.0 mm/sup 2/.

Asymmetric four-port and branch-line hybrids

Two different asymmetric branch-line hybrids, a conventional-direction asymmetric branch-line hybrid (CABH) and an anti-conventional-direction asymmetric branch-line hybrid (AABH) are discussed and their design equations are derived. On the basis of the derived design equations, a uniplanar CABH was fabricated with coplanar waveguide (CPW) technology and measured.

Millimeter-wave silicon MMIC interconnect and coupler using multilayer polyimide technology

This paper reports our latest progress in developing low-loss and low-crosstalk silicon MMIC interconnects for millimeter-wave applications. The proposed silicon/metal/polyimide (SIMPOL) structure based on multilayer polyimide technology is extremely effective in reducing noise crosstalk, and also provides very low line loss, even at the millimeter-wave regime. The measurement results of the developed SIMPOL structures demonstrate extremely low noise crosstalk (<-40 dB) in the entire frequency range (up to 50 GHz), which is limited by the dynamic range of the measurement equipment, and excellent insertion loss (<-0,25 dB/mm) up to 45 GHz. In addition, the SIMPOL concept is applied for the first time successfully in the design and fabrication of branch-line hybrids at millimeter-wave frequencies, 30 and 37 GHz.

Design of a multisection impendance‐transforming branch‐line hybrid using a genetic algorithm

A design method for a multisection impedance-transforming branch-line hybrid using a genetic algorithm is proposed. In contrast to the previous design methods, an asymmetric structure is introduced to optimize the hybrid. Optimization is performed within the impedance range to achieve the realizable hybrids with a microstrip line in a desired frequency range. The hybrid designed by the proposed method has 3–10% more bandwidth than the previous results. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 436–439, 1999

Design of a multisection impendance-transforming branch-line hybrid using a genetic algorithm

A design method for a multisection impedance-transforming branch-line hybrid using a genetic algorithm is proposed. In contrast to the previous design methods, an asymmetric structure is introduced to optimize the hybrid. Optimization is performed within the impedance range to achieve the realizable hybrids with a microstrip line in a desired frequency range. The hybrid designed by the proposed method has 3–10% more bandwidth than the previous results. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 436–439, 1999

Arbitrary power division branch-line hybridterminated by arbitrary impedances

If a four-port network is terminated by arbitrary impedances, conventional methods for even- and/or odd- mode excitation analyses cannot be used because no symmetry planes exist. Under these conditions, new design equations for an asymmetric branch-line hybrid with arbitrary power division are introduced. A uniplanar branch-line hybrid terminated by 45, 35, 60 and 50 Ω with a power splitting ratio of 3 dB was fabricated and measured.

Design of compact multilevel folded-line RF couplers

A new design methodology for compact multilevel multiconductor folded-line couplers is presented in this paper. The approach is based on a general network representation of folded-line structures as interconnected coupled lines in a multilayered environment. Simple design equations are presented for compact directional couplers using two-level C-sections, and branch-line hybrids with single and cascaded C-sections. The new folded-line couplers exhibit a significant reduction in foot print compared to the conventional designs. The directional and hybrid folded-line coupler designs are validated by full-wave electromagnetic simulation. Also, a 3-dB branch-line hybrid using three folded-line sections is fabricated. The measured response is found to be in good agreement with the proposed theory.

3 dB branch-line hybrid terminated by arbitrary impedances

New design equations for a 3 dB branch-line hybrid terminated by arbitrary impedances are presented. On the basis of these equations, simulations and measurements have been carried out using coplanar-waveguide technology.

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.

High temperature superconducting space-qualified multiplexers and delay lines

A high temperature superconducting (HTS) four-channel multiplexer and a delay line were fabricated, space qualified and tested as part of the U.S. Navy's High Temperature Superconductivity Space Experiment II (HTSSE-II). The multiplexer had an architecture that included two branch-line hybrids and two identical parallel-coupled line filters per channel. Its operation was centered at 4 GHz, with 50-MHz-wide channels. It was fully integrated, with microstrip interconnections between channels and thin-film load terminations in the out-of-phase port of the output hybrid. The delay line was made up of two cascaded modules for a total delay of 45 ns between 2 and 6 GHz. Both devices were made using 5-cm-diameter LaAlO/sub 3/ wafers coated with epitaxial thin film YBa/sub 2/ Cu/sub 3/O/sub 7/, on both sides in the case of the delay line. Both devices operated at 77 K.

High-temperature superconducting four-channel filterbanks

A high-temperature superconducting four-channel filterbank was fabricated and tested. The device was made in microstrip configuration with an architecture that included two branch-line hybrids and two identical parallel-coupled line filters per channel. The filterbank was fully integrated, with microstrip interconnections between channels and thin-film load terminations in the out-of-phase port of the output hybrid. >

A multisection broadband impedance transforming branch-line hybrid

Measurements and design equations for a two section impedance transforming hybrid suitable for MMIC applications and a new method of synthesis for multisection branch-line hybrids are reported. The synthesis method allows the response to be specified either of Butterworth or Chebyshev type. Both symmetric (with equal input and output impedances) and non-symmetric (impedance transforming) designs are feasible. Starting from a given number of sections, type of response, and impedance transformation ratio and for a specified midband coupling, power division ratio, isolation or directivity ripple bandwidth, the set of constants needed for the evaluation of the reflection coefficient response is first calculated. The latter is used to define a driving point impedance of the circuit, synthesize it and obtain the branch line immittances with the use of the concept of double length unit elements (DLUE). The experimental results obtained with microstrip hybrids constructed to test the validity of the brute force optimization and the synthesized designs show very close agreement with the computed responses.

New small 90° hybrid coupler

The two classical 90° couplers (Lange coupler and branch-line hybrid) are not appropriate for frequencies around 1–5 GHz. The small 90° coupler proposed by the authors is the implementation of the Wheatstone bridge in uniplanar transmission lines. It is dedicated to narrowband applications. The coupler is demonstrated at a centre frequency of 4 GHz.

Planar-circuit-type 3-dB quadrature hybrids

The performance of a conventional branch-line 3-dB hybrid tends to deteriorate with increasing operation frequency because of a pair of low impedance series line sections. This paper treats planar-circuit-type 3-dB quadrature hybrids using a rectangular disk, and realizes good characteristics comparable to those of an ideal branch-line hybrid over a wide operation frequency range by efficacious devices without destroying the simple-shaped configuration. In addition, a method of broadening the hybrid property is examined, and hybrids with flat coupling, e.g., a relative bandwidth of 25%, are obtained at various operation frequencies. These theoretical results are verified experimentally. >

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.

Monolithic image-rejection optoelectronic up-converters that employ the MMIC process

The authors present very small 30-GHz-band monolithic image-rejection optoelectronic up-converters that employ the HEMT MMIC process for the first time. MMIC HEMT optoelectronic mixers are characterized by their direct photodetection and nonlinear characteristics. It is shown that common-source configurations have higher response than common-drain configurations, and up-converter applications are preferable to down-converter applications based on the HEMT direct photodetection characteristics. These characteristics are used to realize 30-GHz-band monolithic image-rejection optoelectronic up-converters. An in-phase divider and a branch-line hybrid with two HEMT optoelectronic mixers are successfully integrated in an MMIC chip with an area of 1.5 mm*1.1 mm. Fundamental performance is demonstrated and excellent wideband performance, which comes from the well-balanced operation of monolithic integrated circuits, is confirmed. These monolithic optoelectronic mixers can be used to realize compact and cost-effective one-chip optical receivers, for fiber optic links which support millimeter waves. >

An extremely small 26 GHz monolithic image-rejection mixer without DC power consumption

This paper describes several design methods for an extremely small 26 GHz monolithic image-rejection mixer. The bias dependence of the drain LO injection mixer is also investigated. Consequently, it was found that there exists an optimum bias point for minimum conversion loss, and the mixer performed well even with zero drain bias voltage. The mixer is fabricated using a uniplanar technique. It consists of drain LO injection mixers, a reduced-size branch-line hybrid, and a Wilkinson divider with a compact layout. The chip measures only 1.6 mm*1.3 mm, which is the smallest among those reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A branchline hybrid, using valley microstrip lines

The branchline hybrid is investigated as an application of valley microstrip lines to a circuit that consists of valley microstrip lines both with and without a slit. It is shown that valley microstrip lines can be utilized for configuring a circuit in accordance with theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multisection broadband impedance transforming branchline quad hybrid suitable for MMIC realisation

A two section impedance transforming branchline hybrid is reported. Such a hybrid is a very useful component for microwave monolithic integrated circuit implementation of a variety of circuits. It is shown that such a hybrid can be optimised to yield a wide operating bandwidth as well as practically realisable branchline impedances. Both equal and unequal power division with 90 degrees relative phase shift are feasible. Computed and measured results show that a 50-35 Omega two section optimised hybrid with equal power division has 30% bandwidth over which the power balance is better than 0.5 dB. The return loss and isolation are better than 20 dB over this bandwidth. >