Quadrature Hybrid Coupler Research Articles

Single-chip Si optical single-sideband modulator

We demonstrate an integrated Si optical single-sideband (OSSB) modulator composed of a parallel dual-ring modulator (PDRM) and a quadrature hybrid coupler (QHC). Both the PDRM and the QHC are carefully designed for 30 GHz opearation, and their operations are verified by measurement. The Si OSSB modulator successfully generates a single sideband with larger than 15 dB suppression of the undesired sideband.

A New Dual Circularly Polarized Feed Employing a Dielectric Cylinder-Loaded Circular Waveguide Open End Fed by Crossed Dipoles

This paper presents a new dual circularly polarized feed that provides good axial ratio over wide angles and low cross-polarized radiation in backward direction. A circular waveguide open end is fed with two orthogonally polarized waves in phase quadrature by a pair of printed crossed dipoles and a compact connectorized quadrature hybrid coupler. The waveguide aperture is loaded with a dielectric cylinder to reduce the cross-polarization beyond 90 degrees off the boresight. The fabricated feed has, at 5.5 GHz, 6.33-dBic copolarized gain, 3-dB beamwidth of 106°, 10-dB beamwidth of 195°, 3-dB axial ratio beamwidth of 215°, maximum cross-polarized gain of −21.4 dBic, and 27-dB port isolation. The reflection coefficient of the feed is less than −10 dB at 4.99–6.09 GHz.

Design and Development of a Hybrid-Coupled Waveguide Multiplexer for a Multiband Receiver

This paper describes a waveguide hybrid-coupled multiplexer for frequencies around 400 GHz. The designed multiplexer has three bands with 25-GHz bandwidth and no frequency gap between channels. The multiplexer is composed of two identical waveguide branch-line quadrature hybrid couplers and two identical bandpass filters based on waveguide inductive iris windows. In order to find the critical element of the multiplexer, network analysis was carried out using signal flow graphs. The multiplexer was fabricated based on direct machining technology with machining accuracy in the order of a few microns. S -parameters measured with a vector network analyzer show excellent agreement with simulations.

Silicon Micromachined Waveguide Quadrature-Hybrid Coupler at Terahertz Frequency Band

A waveguide quadrature-hybrid coupler operating from 350 to 410 GHz is designed and fabricated using the deep reactive ion etching (DRIE) silicon micromachining technique. The four-port branch-line coupling configuration with five branches is used as the basic structure of the coupler. The size of the coupler is about 6.3 mm × 6.3 mm × 1 mm, which is much smaller than the flange used in the vector network analyzer (VNA). Because it is difficult to measure all the characteristics of a four-port coupler with a small size using the two-port VNA with big-size flanges, four testing topologies with different bended input/output waveguide ports are designed for measurements. The terahertz (THz) wedged-type absorbing material is adopted as the replacement of the conventional waveguide matching load because the size of the conventional waveguide matching load is too large to use. Measured results of the proposed coupler are in good agreement with simulated results, indicating that the average insertion loss is 0.9 dB and the isolation is better than 20 dB. Effects of the DRIE process on the coupler’s performance are discussed in detail.

Compact printed quadrifilar helix antenna for universal RFID hand-held reader

This paper presents a compact printed quadrifilar helix antenna (PQHA) for portable UHF RFID reader applications. The circularly polarized PQHA is fed by a feeding network with quadrature-phase and equal amplitude output signals. The quadrature-phase feeding network is composed of a 180° power splitter and two wideband quadrature hybrid couplers implemented by lumped-element circuits. The miniaturized antenna is a one-wavelength resonance type and can preserve high antenna gain. Moreover, the bandwidths of impedance and axial ratio cover the global UHF RFID band (860–960 MHz). The measured impedance bandwidth is about 34.1% and the axial ratio bandwidth covers 700–1,000 MHz. The measured maximum gain is 5.8 dBic and the 3-dB beamwidth is 168°. The height of the entire system is only 79 mm, the radius is 35 mm, and the FR4 substrate for the feeding network is only 80 × 80 × 1.6 mm3. The proposed antenna is suitable for handheld UHF RFID reader applications.

A Novel Compact Low Loss Waveguide Image Rejection Filter Based on a Backward Coupler with Band Pass Filters for 100 GHz Band

This paper describes the design and test observation result of a novel waveguide image rejection filter (IRF). The IRF is based on a quadrature hybrid coupler as a backward coupling structure, followed by Band Pass Filters (BPFs), and matched loads for the image-frequency termination. A prototype IRF shows return loss of better than 18 dB, and an image rejection ratio of more than 25 dB over 4 GHz band for stratospheric ozone spectra at 110 GHz when the LO frequency and IF frequency are 104 GHz and 6 GHz, respectively. We installed the prototype IRF into an ozone-measuring system and successfully observed an ozone spectrum at 110 GHz in single sideband (SSB) mode. This IRF has the advantages of low transmission loss, compact size, and easy scalability for sub-millimeter frequencies.

A 1.6–2.3-GHz RF MEMS Reconfigurable Quadrature Coupler and Its Application to a 360$^{\circ } $ Reflective-Type Phase Shifter

This paper presents the design, fabrication, and measurement of a reconfigurable quadrature hybrid coupler and a tunable low-loss reflective-type phase shifter built using the Cavendish Kinetics RF microelectromechanical systems switched capacitor devices. The quadrature coupler tunes from 1.5 to 2.2 GHz with 20–50-MHz steps, and $> {\hbox {20-dB}}$ reflection and isolation. The phase shifter covers 360 $^{\circ } $ at 2.0 GHz with an insertion loss of ${\hbox {2.0}} \pm {\hbox {0.5}}~{\hbox {dB}}$ at different phase states. The linearity measurements show that these devices can handle up to 5 W of input power at 1.8–2.2 GHz with an input third-order intercept point $( {\rm IIP}_{3}) > 44~{{\hbox {dBm}}}$ over all phase states. The measured second and third harmonic components are $ at 30 dBm of RF input power. The application areas are in-phase shifters for micro and pico base-stations in the 1.7–2.3-GHz range.

Design of Ultra-Low-Power 60-GHz Direct-Conversion Receivers in 65-nm CMOS

This paper has explored an ultra-low-power design of two 60-GHz direct-conversion receivers in a 65-nm CMOS process for single-channel and multi-channel applications under the IEEE 802.15.3c standard, respectively. One subthreshold biasing 0.4-V transconductance mixer is designed with a compact quadrature hybrid coupler (160 μm × 210 μm with measured 3-dB intrinsic loss) in receivers to achieve low power (8 mW for single channel and 12.4 mW for multi-channel) and high gain (55 dB for single channel and 62-dB for multi-channel). One three-stage low-noise amplifier employs high- Q passive matchings. A double-layer-stacked inductor is utilized for matching in the single-channel receiver and a high-impedance transmission line is utilized for matching in the multi-channel receiver, respectively. In addition, one new modified Cherry-Hooper amplifier is applied for the variable-gain amplifier design to achieve high gain-bandwidth product and high power efficiency. The single-channel receiver is implemented with 0.34- mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> chip area. It is measured with a power consumption of 8 mW, a minimum single-sideband noise figure (NF) of 4.9 dB, a 3-dB bandwidth of 3.5 GHz, and a maximum conversion gain of 55 dB. The multi-channel receiver is implemented with 0.56- mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> chip area. It is measured with a power consumption of 12.4 mW, a 3-dB bandwidth of 8 GHz (59.5 ~ 67.5 GHz), and a maximum conversion gain of 62 dB. The measurement results show that the two demonstrated 60-GHz direct-conversion receivers can achieve high gain and low NF with ultra-low power in 65-nm CMOS.

BANDWIDTH IMPROVEMENT OF A COMPACT QUADRATURE HYBRID COUPLER WITH HARMONIC REJECTION USING LUMPED ELEMENTS

A compact quadrature hybrid coupler with harmonic suppression using lumped-element band-stop resonator is proposed for bandwidth improvement. Conventionally, harmonic rejection is realized by three band-stop resonators in lumped hybrids. The using of three band-stop resonators realizes better harmonic suppression while exhibiting narrower frequency response. So as to improve operation bandwidth behavior, the number of band-stop resonator applied in the proposed topology is minimized to one. Trading ofi with acceptable reduction in harmonic rejection, the proposed hybrid enlarges working bandwidth with fewer numbers of lumped devices. Detailed design and theoretical analysis are presented and the expressions of lumped elements with dependence of rejected frequency are obtained. To validate the analysis, three 2.45GHz couplers are fabricated on an FR-4 printed circuit board. The experimental results exhibit 27.3%, 26.9% and 23.3% operation bandwidth with better than 16dB, 17dB, and 21dB harmonic suppressions at 4.9GHz, 6.1GHz, and 7.35GHz, respectively. Less than 0.8dB amplitude imbalance and 2 - phase error are achieved for all the three couplers, which are matched well with theoretical analysis.

Compact broadband quadrature hybrid coupler using planar artificial transmission line

A novel compact size broadband quadrature hybrid coupler based on a planar artificial transmission line which can be used for WLAN application at 2.4 GHz is presented. The planar artificial transmission line is composed with both a dual transmission line and the Π-model technique. The occupied size of the proposed broadband hybrid coupler is merely 47% of the size of a conventional design. The compact size coupler demonstrates well-behaved wideband response and good agreement with measurement.

Low-profile circularly polarized GNSS antenna

In this article, we present a low-profile and low cost antenna for GPS (L1–L2–L5), Galileo (E5–E1–E2), and Glonass (G1–G2) standard. This antenna is a dual-feed planar patch antenna with four slots to achieve dual-band operation. The radiating element is fed by a wideband 90° quadrature hybrid coupler to obtain circular polarization on the both bands. The quadrature feeding is achieved using a three-branch-line hybrid coupler. The return loss bandwidth of the system (S11 ≤ −10 dB) is 22% in the lower band and 14% in the upper one. The axial ratio (AR) bandwidth in broadside direction (AR= 3 dB) is 20% in the lower band and 11.3% at the upper one. The antenna gain is 6 and 8.4 dBi in the normal direction at the central frequency of 1.23 and 1.6 GHz, respectively. The total dimensions of the antenna are 170 mm2 with a thickness of 7.524 mm. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2811–2814, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27175

비접촉 마이크로웨이브 프루브 시스템의 I/Q Demodulator를 위한 MMIC Mixer의 설계

A MMIC (Monolithic Microwave Integrated Circuit) mixer chip using the Schottky diode of an GaAs p-HEMT process has been developed for the I/Q demodulator of non-contact near field microwave probing system. A single balanced mixer type is adopted to achieve simple structure of the I/Q demodulator. A quadrature hybrid coupler and a quarter wavelength transmission line for 180 degree hybrid are realized with lumped elements of MIM capacitor and spiral inductor to reduce the mixer chip size. According to the on-wafer measurement, this MMIC mixer covers RF and LO frequencies of 1650MHz to 2050MHz with flat conversion loss. The MMIC mixer with miniature size of 2.5mm×1.7mm demonstrates conversion loss below 12dB for both variations of RF and LO frequencies, LO-to-IF isolation above 43dB and RF-to-IF isolation above 23dB, respectively.

Thin‐film barium strontium titanate varactor tunable dual‐band quadrature hybrid coupler

AbstractA thin‐film barium‐strontium‐titanate (BST) and a conventional silicon varactor tunable dual‐band quadrature hybrid couplers are characterized and compared in this article. Both structures are composed of four quarter‐wavelength sections at a frequency located between the two operating frequencies, and with two pairs of open‐ended stubs. Frequencies tuning make used of BST interdigital and silicon varactor diode capacitors connected at the open‐ended stubs. The characterized BST interdigital capacitor presents a capacitive‐tunability of 52% through an applied voltage of 0 to 25 V, while 82.5% is for the selected commercial silicon varactor diode. The silicon varactor‐tuned dual‐band coupler exhibits 45.9 and 5.2% center operation tuning frequency for the first and the second band, respectively, while 29.2 and 4.3% are achieved by the BST tunable coupler. With two‐tone nonlinear characterization test, the BST tunable coupler biased at 0 and 25 V presents a better IP3 of +25.45 and +35 dBm, respectively, while +11.5 and +34 dBm are obtained for the silicon varactor tunable coupler. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:858–867, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26719

A NOVEL WIDEBAND CIRCULARLY POLARIZED ANTENNA FOR WORLDWIDE UHF BAND RFID READER APPLICATIONS

This paper presents the novel design of a wideband circularly polarized (CP) Radio Frequency Identiflcation (RFID) reader microstrip patch antenna for worldwide Ultra High Frequency (UHF) band which covers 840{960MHz. The proposed antenna, which consists of a microstrip patch with truncated corners and a cross slot, is placed on a foam substrate (r = 1:06) above a ground plane and is fed through vias through ground plane holes that extend from the quadrature 3dB branch line hybrid coupler placed below the ground plane. This helps to separate feed network radiation, from the patch antenna and keeping the CP purity. The prototype antenna was fabricated with a total size of 225 £ 250 £ 12:8mm 3 which shows a measured impedance matching band of 840{1150MHz (31.2%) as well as measured rotating linear based circularly polarized radiation patterns. The simulated and measured 3dB Axial Ratio (AR) bandwidth is better than 23% from 840{1050MHz meeting and exceeding the target worldwide RFID UHF band.

Multi-layer quadrature hybrid coupler design composed of multiple circular sectors

A hybrid coupler design composed of multiple circular sectors is presented. It is designed to cover wireless local-area network bands at 2.4, 5.25 and 5.8 GHz, ultra-wideband at 3.1–4.8 GHz, digital multimedia broadcasting at 2.6 GHz and WiMax at 3.5 GHz. The coupler achieves an amplitude imbalance of 1 dB and a phase error of 5° at the outputs within the design frequency range. The developed coupler was compared with other existing designs in literature. It demonstrated advantages in terms of wide operating bandwidth as well as small physical size.

A 400–500 GHz Balanced SIS Mixer with a Waveguide Quadrature Hybrid Coupler

We have developed a 400-500 GHz low-noise balanced SIS (Superconductor Insulator Superconductor) mixer, which is based on a waveguide RF quadrature hybrid coupler. The RF quadrature hybrid was designed and fabricated as a broadband hybrid with good performance at 4 K. The fabricated RF quadrature hybrid was measured at room temperature with a submillimeter vector network analyzer to check amplitude and phase imbalance between two output ports. Then the balanced mixer was assembled with the RF hybrid, two DSB mixers, and a 180 IF hybrid. Several important parameters such as noise temperature, LO power reduction, and IF spectra were measured. The LO power reduction is defined as how much LO power the balanced mixer saves compared with a typical single-ended mixer. The measured noise temperature of the balanced mixer was similar to 55 K at the band center which corresponds to similar to 3 times the quantum noise limit (hf/k) in DSB, and similar to 120 K at the band edges. The noise performance over LO frequency was almost the same as that of the worse DSB mixer used in the balanced mixer. In addition the LO power required for the balanced mixer is similar to 11 dB less than that of the single-ended mixers.

A New Planar Artificial Transmission Line and Its Applications to a Miniaturized Butler Matrix

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A miniaturized quadrature hybrid coupler, a rat-race coupler, and a 4 <formula><tex>$\times$</tex></formula> 4 Butler matrix based on a newly proposed planar artificial transmission line are presented in this paper for application in ultra-high-frequency (UHF) radio-frequency identification (RFID) systems. This planar artificial transmission line is composed of microstrip quasi-lumped elements and their discontinuities and is capable of synthesizing microstrip lines with various characteristic impedances and electrical lengths. At the center frequency of the UHF RFID system, the occupied sizes of the proposed quadrature hybrid and rat-race couplers are merely 27% and 9% of those of the conventional designs. The miniaturized couplers demonstrate well-behaved wideband responses with no spurious harmonics up to two octaves. The measured results reveal excellent agreement with the simulations. Additionally, a 4<formula formulatype="inline"><tex>$\,\times\,$</tex></formula>4 Butler matrix, which may occupy a large amount of circuit area in conventional designs, has been successfully miniaturized with the help of the proposed artificial transmission line. The circuit size of the Butler matrix is merely 21% of that of a conventional design. The experimental results show that the proposed Butler matrix features good phase control, nearly equal power splitting, and compact size and is therefore applicable to the reader modules in various RFID systems. </para>

Varactor-Tuned Dual-Band Quadrature Hybrid Coupler

A tunable dual-band quadrature hybrid coupler for mobile GSM bands (900 and 1800MHz) is proposed and characterized. The structure is composed of four quarter-wavelength sections at a frequency located between the two operating frequencies and two pairs of open-ended stubs. Frequency tuning is achieved by modifying the electrical length of the open-ended stubs with varactor-diode capacitors. A dual-band tunability of 33% and 10% is obtained for the first and the second bands, respectively

A 90-nm CMOS Doherty Power Amplifier With Minimum AM-PM Distortion

A linear Doherty amplifier is presented. The design reduces AM-PM distortion by optimizing the device-size ratio of the carrier and peak amplifiers to cancel each other's phase variation. Consequently, this design achieves both good linearity and high backed-off efficiency associated with the Doherty technique, making it suitable for systems with large peak-to-average power ratio (WLAN, WiMAX, etc.). The fully integrated design has on-chip quadrature hybrid coupler, impedance transformer, and output matching networks. The experimental 90-nm CMOS prototype operating at 3.65 GHz achieves 12.5% power-added efficiency (PAE) at 6 dB back-off, while exceeding IEEE 802.11a -25 dB error vector magnitude (EVM) linearity requirement (using 1.55-V supply). A 28.9 dBm maximum Psat is achieved with 39% PAE (using 1.85-V supply). The active die area is 1.2 mm/sup 2/.

Fine-tuning of the resonant frequency using a hybrid coupler and fixed components in SAW oscillators for gas detection

A method for fine-tuning of the resonant frequency of a typical delay line (DL) SAW oscillator by means of a procedure simple and widely used in microwave circuits is presented. It consists of a quadrature hybrid coupler in whose coupled ports, two identical terminations are placed. Each of them is composed of a set formed by a fixed capacitor C and a fixed inductor L in series. In this way no variable components are used. Therefore the phase can be adjusted for every sensor once the polymer film is deposited and measured. The output signal has the same amplitude than the input one and its phase is changed depending on the value of C and L. The oscillator designed in this way exhibits stable frequency response and operates with a wide range of coatings in measurements with volatile organic compounds (VOCs).