Lange Coupler Research Articles

Compact Reflectometers for a Wideband Microwave Breast Cancer Detection System

The design of compact wideband microwave reflectometers for the purpose of inclusion in a breast cancer detection system is presented. In this system, a wideband frequency source is used to synthesize a narrow pulse via the step-frequency synthesis method. The reflectometer undertakes measurements in the frequency domain and the collected data is transformed into the time/space domain using IFFT. In order to accomplish reflection coefficient measurements over a large frequency band, compact wideband couplers and power dividers are used to form the reflectometer. Two compact six-port reflectometer configurations are investigated. One uses the Lange coupler and the Gysel power divider and the other one employs a 3dB slot-coupled microstrip coupler and a 2-stage Wilkinson power divider. The reflectometer employing the slot-coupled coupler and the Wilkinson divider provides a wider operational bandwidth, as shown by simulation results performed with Agilent ADS.

A 3-dB Quadrature Coupler Suitable for PCB Circuit Design

A quadrature 3-dB coupler, which combines the advantages of a coplanar waveguide and microstrip line structure suitable for single-layer substrate printed circuit board (PCB) circuit design is proposed. As compared to the conventional Lange coupler, the proposed coupler with the advantages of increasing the coupled linewidths and coupling spacing without using extra bonding wires can solve the drawbacks of Lange coupler. In addition, the proposed structure can easily be realized in a single-layer substrate by PCB manufacturing processes to eliminate the effects and uncertain factors from a multilayer substrate. Good agreements between the simulation and measurement in the frequency range from 0.45 to 5 GHz can be seen. With the operation bandwidth ranging from 1.8 to 2.8 GHz, the measured results of the return loss are better than 18.2 dB and insertion losses of coupled and direct ports are approximately 3plusmn0.1 dB; the relative phase difference is approximately 89.8deg. The dimension of the circuit is 2.7 cm times1.6 cm times0.08 cm

Inductively Compensated Parallel Coupled Microstrip Lines and Their Applications

A simple method using lumped inductors to compensate unequal even- and odd-mode phase velocities in parallel coupled microstrip lines is presented. The singly and doubly compensated cases are analyzed to enable the optimum inductor values and the electrical lengths of the compensated coupled lines to be calculated from closed-form expressions. The technique proposed not only improves the performance, but also yields a more compact design. To demonstrate the technique's broad range of applicability, the compensated coupled-line structure is used to enhance the performance of a 900-MHz Lange coupler, a 1-GHz multisection 10-dB coupler, a 900-MHz planar Marchand balun, and a 1.8-GHz parallel coupled bandpass filter

A PCB-compatible 3-dB coupler using microstrip-to-CPW via-hole transitions

A 3-dB coupler by implementing microstrip-to-coplanar waveguide (CPW) via-hole transitions is proposed. The proposed coupler, with the advantages of wider coupled line widths and spacing without using any bonding wires, can eliminate the uncertain factors of conventional Lange couplers caused by the printed circuit board (PCB) manufacturing processes. The proposed coupler can be easily fabricated on a single-layer PCB substrate instead of using multilayer substrates. Good agreements between the simulation and the measurement in the frequency range from 0.45 to 5 GHz can be achieved. The measured results at the center frequency of 2.4 GHz have the return loss better than -15dB; the insertion loss of coupled and direct ports is about 3/spl plusmn/ 0.2dB and the relative phase difference of 89/spl plusmn/0.3/spl deg/. The dimension of the coupler is 3.1cm /spl times/ 1.8cm.

The design of a dual polarized QUASI‐YAGI antenna array

AbstractIn this article, the design of a dual‐polarized quasi‐Yagi antenna array is described. The quasi‐Yagi elements are fed by broadband microstrip‐to‐CPS balun. A feeding circuit that contains multiple Lange couplers is designed to feed a 2 × 2 array of quasi‐Yagi elements. A 30% bandwidth (1.4 to 1.75 GHz) is achieved for VSWR and gain. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1164–1169, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21550

Millimeter-Wave Lange Coupler Design and Its Application in the Monolithic Image Rejection Mixer Design

This paper reports on the design of a Ka-band monolithic Lange coupler and its application in the monolithic fourth-harmonic image rejection mixer. Detailed design and analysis using Ansoft-HFSS simulator have been carried out. The simulated results of the Lange Coupler show the insert loss is better than −3.64 dB; the amplitude balance is less than 0.55 dB and the phase balance is less than 0.65° from the 90° phase difference over the 30 to 40 GHz frequency range. The Lange Coupler is employed in a monolithic image rejection mixer that is fabricated by a commercial 0.18-μm pseudomorphic high electron-mobility transistor (pHEMT) process. The chip size is 1.4 mm × 1.9 mm. The image rejection ratio (IMR) is from 15 to 34 dB in the RF frequency range of 30 to 40 GHz.

Wideband balanced AlGaN/GaN HEMT MMIC low noise amplifier

A 3-16 GHz wideband AlGaN/GaN high electron mobility transistor (HEMT) low noise amplifier (LNA) on silicon carbide substrate, using balanced configuration with a coplanar waveguide Lange coupler, is designed and fabricated. This LNA shows a minimum noise figure of 4 dB with associated gain of 20 dB with gain flatness of /spl plusmn/3 dB across the 3-16 GHz frequency range. The output third order intercept point of 38 dBm is achieved at 8 GHz.

An X-Band Front-End Module Using HTS Technique for a Commercial Dual Mode Radar

A front end module of receiver has been designed to eliminate the interference between the tracking and searching radar used in commercial radar application. The module is located at the receiving path of the searching radar. The proposed module includes two parts, the HTS superconducting filter and cryogenic low noise amplifier. The bandwidth of the eight-resonator HTS hairpin filter is 2% at the X-band frequency. Low insertion loss (below1 dB) and good skirt rejection (down to 60 dB at 50 MHz from the pass-band edge) are obtained. The two-stage low noise amplifier is designed by commercial low noise HEMT devices, NE321000. Two Lange couplers are located at output and input port of each amplifier stage to improve the return loss and to make LNA easily match to optimal low noise impedence. The cryogenic amplifier shows 30 dB gain and 0.4 dB NF at 77 K in X-band. A very high rejection is necessary for the elimination of unwanted spurious signals. The acceptable specification is 110 dB down at 500 MHz away from the band-edge of the filter. In general, the skirt rejection of a hairpin HTS filter is pretty good near the pass-band edge, but may become worse far from the pass-band edge. To meet the requirement of this commercial radar application, a high rejection suspended stripline filter is put after the low noise amplifier. The whole module shows an maximal NF of 1.5 dB, a gain of 25 dB around pass-band frequencies, and a rejection of better than 110 dB at 500 MHz away from the band edge of the filter. It totally solves the interference problem in this dual mode radar.

A design of wideband 3-dB coupler with N-section microstrip tandem structure

New design equations and a 3-dB microstrip coupler example for N-section tandem connected structure with wide bandwidth are presented. The proposed four-port S-parameters and equations are obtained from a port reduction method. The designed microstrip 3-dB coupler not only does not need high impedance lines, but also uses tight coupling gaps differently from conventional couplers such as Lange couplers, parallel coupled line couplers, etc. The measured data agrees well with the expected data, which show a wide bandwidth of 42%, an amplitude imbalance of /spl plusmn/0.5 dB, a phase unbalance of 1.0/spl deg/, and isolation characteristics of 15 dB at the band of 3.6 to 5.5 GHz.

Balanced topology to cancel Tx leakage in CW radar

Balanced topology in radar front-end is presented, which can reduce Tx leakage to receiver drastically. The balanced radar front-end which is composed of a differential cross-coupled oscillator, two Lange couplers, and a Wilkinson combiner is implemented using commercially available InGaP/GaAs heterojunction bipolar transistor technology. The tuning range of voltage control oscillator is 320 MHz from 25.307 to 25.627 GHz. The peak output power is 0.8 dBm. Average Tx-to-Rx isolation is about 40.5 dB. Since the isolation of the Lange coupler is 19 dB, the additional cancellation due to balanced topology is expected to be 21.5 dB. The chip size is 1.05 /spl times/ 1.70 mm/sup 2/.

A New Overlay Coupler for Direct Digital Modulator in GaAs HBT

A new overlay coupler has been realized at millimeter-wave frequency with an area that is less than one-half that of the Lange coupler. It was used to construct a binary phase-shift keying (BPSK) modulator, employing balanced reflection topology, in which the HBTs acted as switches. It was shown that the BPSK modulator could be modulated at 1 Gb/s at 28 GHz.

Ka‐band PHEMT MMIC VCO with wide tuning range

AbstractA Ka‐band MMIC VCO utilizing 0.15‐μm T‐gate GaAs P‐HEMT technology is presented. The VCO exhibits a low‐phase noise property with wide tuning range of up to 3 GHz. A balanced buffer amplifier is also developed to ensure that the output power is higher than 10 dBm. The best measured phase noise at 1 MHz offset is −106 dBc/Hz. By varying the bias voltage of the on‐chip varactor, the frequency can be continuously tuned from 33.3 to 36.3 GHz. In this frequency range, output power higher than 10 dBm has been measured without using the buffer amplifier. The buffer amplifier exhibits a typical gain of 5 dB with 15‐dBm output power. A Lange coupler provides good matching between the VCO and the amplifier. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 333–336, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11206

Simulation of Single-Stage Tunable Amplifier Using Ferroelectric Materials

The non-linear electric field dependence of ferroelectric thin films can be used to design frequency and phase agile components. Tunable components have traditionally been developed using mechanically tuned resonant structures, ferrite components, or semiconductor-based voltage controlled electronics, but they are limited by their frequency performance, high cost, high losses, and integration into larger systems. In contrast, the ferroelectric-based tunable microwave component can easily be integrated into conventional microstrip circuits and attributes such as small size, light weight, and low-loss make these components attractive for broadband and multi-frequency applications, many of these components are essential elements in the design of a microwave sensor and/or circuit. It has been reported that with a thin ferroelectric film placed between the top conductor layer and the dielectric material of a microstrip structure, and the proper DC bias scheme, tunable components above the Ku band can be fabricated. Components such as phase shifters, coupled line filters, and Lange couplers have been reported in the literature using this technique. In this work, simulated results from a full wave electromagnetic simulator are obtained to show the tunability of a single stage amplifier. Input and output matching networks are simulated on a ferroelectric thin film to control the frequency response of the amplifier.

A wide-band reflection-type phase shifter at S-band using BST coated substrate

The design and experimental results of a wide-band monolithic reflection-type phase shifter are presented in this paper. The phase shifter fabricated on Ba/sub 0.6/Sr/sub 0.4/TiO/sub 3/ (BST)/sapphire consists of a coplanar waveguide (CPW) Lange coupler, a series resonated LC termination, and a bias network. The CPW Lange coupler results in a power split of 3.5 dB/spl plusmn/0.5 dB in the range of 1.6-3.2 GHz. The BST interdigital capacitor has a tunability (C/sub max//C/sub min/) of 3.1 with 140 V. Measured and simulated performance of a series resonated LC termination was described. The phase shifter has achieved a phase-shift range of over 90/spl deg/ with an insertion loss of better than 2.0 dB and a return loss of higher than 14 dB in the frequency range of 1.9-2.5 GHz over a bias voltage range from 0 to 160 V. A figure-of-merit of maximum 72/spl deg//dB at 2 GHz was obtained. The smaller phase shifter using the folded-type CPW Lange coupler, which maintains a smaller aspect ratio for easier packaging, has an insertion loss of better than 2.3 dB with a phase-shift range of over 130/spl deg/ at 2.5 GHz. Two-tone measurements of the phase shifter indicate an input IP/sub 3/ of 32 dBm with 0 V and 41.9 dBm with 60 V. Total size of the monolithic BST phase shifter is 11.2 mm /spl times/ 4.9 mm /spl times/ 0.43 mm for the straight coupler design and 5.4 mm /spl times/ 6.5 mm /spl times/ 0.43 mm for the folded-type design.

Compact single-chip W-band FMCW radar modules for commercial high-resolution sensor applications

Two compact single-chip 94-GHz frequency-modulated continuous-wave (FMCW) radar modules have been developed for high-resolution sensing under adverse conditions and environments. The first module contains a monolithic microwave integrated circuit (MMIC) consisting of a mechanically and electrically tunable voltage-controlled oscillator (VCO) with a buffer amplifier, 10-dB coupler, medium-power and a low-noise amplifier, balanced rat-race high electron-mobility transistor (HEMT) diode mixer, and a driver amplifier to increase the local-oscillator signal level. The overall chip-size of the FMCW radar MMIC is 2/spl times/3.5 mm/sup 2/. For use with a single transmit-receive antenna, a 94-GHz microstrip hexaferrite circulator was implemented in the module. The radar sensor achieved a tuning range of 1 GHz, an output signal power of 1.5 mW, and a conversion loss of 2 dB. The second FMCW radar sensor uses an MMIC consisting of a varactor-tuned VCO with injection port, very compact transmit and receive amplifiers, and a single-ended resistive mixer. To enable single-antenna operation, the external circulator was replaced by a combination of a Wilkinson divider and a Lange coupler integrated on the MMIC. The circuit features coplanar technology and cascode HEMTs for compact size and low cost. These techniques result in a particularly small overall chip-size of only 2/spl times/3 mm/sup 2/. The packaged 94-GHz FMCW radar module achieved a tuning range of 6 GHz, an output signal power of 1.5 mW, and a conversion loss of 5 dB. The RF performance of the radar module was successfully verified by real-time monitoring the time flow of a gas-assisted injection molding process.

An S-Band Reflection-Type Phase Shifter - A Design Example Using Ferroelectrics

AbstractOne of the challenges faced in using ferroelectrics in high frequency devices is how to effectively use the material in a circuit design. A compact reflection-type phase shifter fabricated on sapphire substrates coated with ferroelectric barium strontium titanate (BST) thin-films has been built which shows the promise of using BST thin films in the design of tunable microwave devices. The phase shifter, fabricated as one monolithic assembly, consists of a 3dB coupler, meandered line inductors and tunable interdigital capacitors. A continuously variable phase shift range of more than 100° using the branch-line coupler was obtained at a center frequency of 2.95 GHz, and more than 90° phase shift over 200 MHz bandwidth with a bias voltage range from 0 V to 175 V. The phase shifter using the Lange coupler has over 700 MHz bandwidth centered at 2.2 GHz with a phase shift of more than 90° and an insertion loss less than 2 dB and return loss of greater than 14 dB, over a bias voltage range from 0 V to 160 V. The loss of the BST phase shifter presented in this work is on the order of other commercially available RF front-end components, such as bandpass filters and RF switches. This holds promise for the practical realization of smart antenna systems in cellular handsets and wireless LAN cards.

Design and Simulation of a Tunable Multilayer Lange Coupler

Full-wave electromagnetic simulators based in the method of moments (HP-EEsof Momentum) and in the finite difference time domain technique (Remcom's XFDTD) are ideal to analyze and study the effect of ferroelectric materials on the output response of microwave passive structures. The nonlinear electric field dependence of ferroelectric thin films has been used by the microwave research community to design tunable components. The fabrication of these structures is expensive and time consuming, hence, estimated results of the S-parameters using electromagnetic simulators are desirable previous to the fabrication process. In this work, BSTO ferroelectric thin film is used on MgO to simulate the output response of a K band multilayer Lange coupler. The S-parameters of the couplers are estimated for different bias conditions for the BSTO. Isolation, insertion loss, coupling, and return loss are computed for different bias conditions.

Six‐finger Lange coupler on 3 mil GaAs substrate using multilayer MMIC technology

AbstractThis paper presents the design and test data for six‐finger Lange couplers on a 3 mil GaAs substrate using the multilayer MMIC process. We achieved coupling of 3.3±0.5 dB, isolation greater than 20 dB, and return loss better than 15 dB over most of the 8–16 GHz frequency range. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 322–327, 2001.

Compact reflective-type phase-shifter MMIC for C-band using a lumped-element coupler

The design and results of an ultra-compact single-load reflective-type monolithic-microwave integrated-circuit phase shifter at 6.2 GHz for a satellite radar system is presented in this paper, which has been fabricated using a commercial 0.6-/spl mu/m GaAs MESFET process. A 3-dB 90/spl deg/ coupler with lumped elements enables significant circuit size reduction in comparison to former approaches applying microstrip branch line or Lange couplers. Phase control is enabled using MESFET varactors with capacitance control ratios (C/sub max//C/sub min/) of only four. Equations are derived to precisely describe the phase control ranges versus capacitance control ratios for different load configurations to allow efficient optimizations. Furthermore, the design tradeoff between low loss and high phase control range is discussed. Within a phase control range of 210/spl deg/, a loss of 4.9 dB/spl plusmn/0.9 dB and a 1-dB input compression point of higher than 5 dBm was measured for the designed phase shifter. The circuit size is less than 0.5 mm/sup 2/, which, to our knowledge, is the smallest reflective-type phase-shifter size reported to date.

The influence of the bumping height on the performance of flip‐chipped CPW Lange couplers

AbstractThe influence of the bumping height on the performance of flip‐chipped CPW Lange couplers is investigated. The coupler design method is done by measurements of a coupler integrated in a multilayer thin‐film MCM‐D. The reasons for the detuning are identified, and solutions to easily predistort the design or reduce the detuning effect are given. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 263–267, 2001.