Dual Directional Coupler Research Articles

Wigner distribution of elliptical quantum optical vortex

We calculate the Wigner quasiprobability distribution function of the quantum elliptical vortex in elliptical beam (EEV), produced by coupling squeezed coherent states of two modes. The coupling between the two modes is performed by using beam splitter (BS) or a dual channel directional coupler (DCDC). The quantum interference due to the coupling between the two modes promises the generation of controlled entanglement for quantum computation and quantum tomography.

무선 주파수 전력 측정을 위한 광대역 전력 센서 개발

본 논문에서는 300~3800MHz 주파수 대역에서 150mW~150W의 평균전력과 피크 전력을 검출할 수 있는 무선전력 검출센서의 개발에 대하여 기술하고 있다. 제안된 무선전력 센서는 기본적으로 전력의 크기를 검출하는 기능 외에 입력 신호의 주파수를 알아낼 수 있는 기능과 VSWR 측정 기능을 가지고 있다. 본 논문의 검출 센서는 듀얼 방향성 결합기의 설계, 입력 전력을 검출하여 DC 데이터로 분석할 수 있는 전력 검출부의 설계, 정확한 캘리브레이션 데이터 추출 방법 등의 세부 과정을 통하여 개발이 완성된다. 개발된 듀얼 방향성 결합기는 300~3800MHz 대역에서 0.085dB의 삽입손실과 3.8GHz에서 최소 30dB의 directivity 성능을 가지고 있다. 개발된 무선전력 센서는 주파수 결정능력과 함께 순방향 입력전력의 크기를 0.25dB 이내의 오차로 분석할 수 있고, 300~3800MHz의 주파수에서 150W의 고출력 동작에서도 1.17~1.96의 VSWR을 측정할 수 있는 성능을 지닌다. This paper describes the development of a power sensor for wireless signal over the ultra wideband range of 300~3800MHz with the detecting range of 150mW~150W. The proposed power sensor fundamentally has the function of not only detecting wireless power, but recognizing frequency and measuring VSWR. The development of the power sensor is completed through the design of dual directional coupler, design of power detector block which produces DC data using the corresponding RF input power level, and establishment of collecting the exact calibration data. The dual directional coupler has the operating frequency of 300~3800MHz with the 0.085dB of insertion loss, and directivity of 30dB at least at 3800MHz. The developed power sensor has the capability of power sensing with less than 0.25dB of resolution as well as measuring VSWR of 1.17~1.96 under the practical operating situation of very high power up to 150W at 300~3800MHz.

A dual directional coupler with unique asymmetric coupling values at 1.7–2 GHz

AbstractRadio characteristic evaluations of each component through the entire communication system can be performed by using the signal sampling methods, which give information of the precise statistics and high qualified specifications. Particular modern trends on electrical devices demand extremely miniaturized dimensions to meet the hand‐held system units, such as personal communication services, mobile RFID applications and other possible products including crucial factors of low‐profile and mobility. It is eventually aimed to avoid unnecessary waste of manufacturing products, and guarantee the mobility, ease of use and so forth. Thus the multi‐mode electrical devices providing numerical advances in a single structure are needed and this is the motivation of further experiments. In this study, we propose a novel dual directional coupler design schemes including derivative calculations and its completely manufactured prototype. It has been designed by promoting three parallel coupled transmission lines with novel mathematic formula and auxiliary simulation systems. Outstanding technical features can be high isolation and directivity characteristics and these will be illustrated within the statistical tables and graphics for verification. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 775–780, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23188

All optical logic gates based on an asymmetric nonlinear directional coupler

The performance of three different asymmetric dual core nonlinear directional couplers which includes an increasing and a decreasing self-phase modulation profile (SPM) was investigated. The asymmetry is associated to the SPM profile of one of the channels. Looking at the transmission characteristics of the device, through the direct- and cross-channel, we did a study of the extinction ratio (Xratio) of the devices. It was observed that in the operation of the three couplers, the performance of AND, XOR and OR gates are dependent on the nonlinearity profile of the coupler. For all configurations, an AND port with gain was observed. We can conclude that to operate the asymmetric coupler as a logic gate one has to control the nonlinearity profile to optimize the transmission characteristics thorough the extinction rate coefficient (Xratio).

Coupling to nanophotonic waveguides using a dual grating-assisted directional coupler

An analysis of a device we have called a dual grating-assisted directional coupler (DGADC) in silicon-on-insulator technology is presented. The device enables efficient coupling from optical fibres to small waveguides, typically <1 µm in cross-sectional dimensions. Coupling efficiency and device length are determined as functions of layer thicknesses and refractive indices, grating periods, depths and duty ratios, and finally wavelength. For our example calculation of coupling to a 250 nm silicon waveguide, this efficient and robust coupler can have coupling efficiency as high as 90%, while the wavelength range can have an FWHM of ~1.6 nm at resonance. Fabrication tolerances have also been analysed and they are up to two orders of magnitude larger than those of a GADC with only one grating.

Dual grating-assisted directional coupling between fibers and thin semiconductor waveguides

A novel dual grating-assisted directional coupler (DGADC) for coupling an optical fiber with a thin semiconductor waveguide is proposed. As an example, a DGADC in silicon-on-insulator is discussed. Maximum coupling efficiency in excess of 90% can be obtained using this coupler, while the highest coupling efficiency previously reported was only 40%.

Preliminary design of high-power wave-guide/transmission system for multimegawatt CW requirements of 100 MeV proton LINAC

Development of a 100 MeV CW proton LINAC has been planned at CAT. This LINAC will be needing CW rf power in the frequency ranges of 350 MHz and 700 MHz for its RFQ and DTL/CCDTL/SFDTL structures respectively. The power to the accelerating structures will be produced by either 1 MW CW or 250 kW CW klystrons/inductive output tubes (HOM IOTs). The power needed by respective feed points in the structure is max. 250 kW which will be powered by splitting the power from 1 MW klystron/klystrode into four channels by using a wave-guide system. In case of using 250 kW tubes the power to the structures will be provided directly from each tube. Two types of wave-guide transmission system have been considered, viz, WR 2300 for 350 MHz rf needs and WR 1500 for 700 MHz rf needs. The typical wave-guide system has been designed using the 1 MW CW klystron followed by wave-guide filter, dual directional coupler, high-power circulator, three 3 dB magic TEE power dividers to split the main channel into four equal channels of 250 kW each. Each individual channel has dual directional couplers, flexible wave-guide sections and high power ceramic vacuum window. The circulator and each power divider is terminated into the isolated ports by high power CW loads. Out of the four channels three channels have phase shifters. Present paper describes the technological aspects and design specifications-considerations for these stringent requirements.

Rf probe technology for the next generation of technologicalplasmas

We describe radio frequency (rf) analysis of technological plasmasat the 13.56 MHz fundamental drive frequency and integer narrow-band harmonicsup to n = 9. In particular, we demonstrate the use of harmonic amplitudeinformation as a process end-point diagnostic. Using very high frequency (vhf)techniques, we construct non-invasive ex situ remote-coupled probes: adiplexer, an equal-ratio-arm bridge, and a dual directional coupler used as asingle directional device. These probes bolt into the plasma-tool 50 Ωtransmission-line between the rf generator and matching network, and hence donot require modification of the plasma tool. The 50 Ω probe environmentproduces repeatable measurements of the chamber capacitance and narrow-bandharmonic amplitude with an end-point detection sensitivity corresponding to a2 dB change in the harmonic amplitude with the removal of 1 cm2 of photoresist.The methodology and design of an instrument for the measurement of theplasma-tool frequency response, and the plasma harmonic amplitudeand phase response are examined. The instrument allows the monitoring of theplasma phase delay, plasma-tool short- and long-term ageing, and processend-point prediction.

High performance dual directional couplers for near-mm wavelengths

A low loss, high directivity dual directional coupler has been developed suitable for fabrication in waveguide bands up to WR3 (220-325 GHz). The design uses waveguide split on the E plane centerline with three waveguides running side by side and coupling holes made by drilling through all three guides. Construction is relatively simple and the resulting structure is very robust mechanically. Typical coupling is 15 dB, directivity is 25-30 dB, and the insertion loss of the WR3 coupler is 0.5 dB.

High power continuous wave microwave system at 3.7 GHz

The lower hybrid current drive (LHCD) system is an important system in superconducting steady state tokamak (SST-1). It is used to drive and maintain the plasma current for 1000 s with a duty cycle of 17%. The LHCD system is being designed to launch 1 MW of radio frequency (rf) power at 3.7 GHz. The rf source is comprised of two high power klystron amplifiers, each capable of delivering 500 kW rf power. In this article, the results obtained during installation and commissioning of these klystrons are presented. Two klystrons (model TH2103D) have been successfully installed and commissioned on dummy loads, delivering ∼200 kW power for more than 1000 s. The maximum output power that could be obtained is limited due to the available direct current (dc) power supply. The test system is comprised of a TH2103D klystron, a low power rf (3.7 GHz/25 W) source, two high power four port circulators, two high power dual directional couplers, two arc detector systems, and two dummy water loads. To avoid rf breakdown in the rf components of the transmission line, the system has been pressurized with dry air to 3 bar. To energize and operate the klystron, a high voltage dc power supply, a magnet power supply, an ion pump power supply, a −65 kV floating anode modulator power supply, and a filament power supply are used. An arc detector unit has been installed to detect and initiate action within a few microseconds to protect the klystron, waveguides, and other rf passive components during arcing. To protect the klystron in the event of an arc, a fast responding (&amp;lt;10 μs), rail gap based pressurized crowbar unit has been used. The entire system is water cooled to avoid excess temperature rise during high power continuous wave operation of the klystron and other rf components. The tube requires initial conditioning. Thereafter, the output rf power is studied as a function of beam parameters such as cathode voltage and beam current.

Remote-coupled sensing of plasma harmonics and process end-point detection

A remote-coupled dual-directional coupler used in the single-directional mode for process harmonic end-point detection is described. Harmonic end-point detection of photoresist stripping and chamber cleaning of silicon dioxide is demonstrated in three different plasma tools for two plasma chemistries (pure O 2 and 10% O 2 in CF 4, respectively). The responding harmonic number is found to be determined by the frequency response of the plasma tool, whereas the harmonic amplitude response is proportional to the volume of injected etched material, either from a wafer surface or chamber wall. The technique described uses a non-invasive remote-coupled probe which can be employed without re-engineering the plasma tool.

Multistable all-optical switching behavior of the asymmetric nonlinear directional coupler

Asymmetric dual core nonlinear directional couplers that include an increasing self phase modulation profile are examined. The asymmetry is associated with the self phase modulation profile of one of the channels (direct channel). Looking at the transmission characteristics of the device, through the direct channel, one observes that, when pumping in the direct channel, there is a decrease in the critical power which is lower compared with the symmetric coupler, and the critical power is a single-value function of the nonlinearity. For the pump power in the cross channel the transmission function of the coupler presents regions of multistability, where the coupler presents more than one critical power for certain values of the self phase modulation profile index. It was also observed that all the profiles under study, with increasing self phase modulation profile, present this behavior. For the studied profiles, one region of multistability was observed where three possible critical powers were observed. However, for the exponential profile, a second region was observed for a higher value of the self phase modulation profile parameter. It is concluded that to operate the asymmetric coupler in a single-value region for the critical power, the exponential self phase modulation profile presents the best behavior for the profiles under study.

Optical Multistability on the Asymmetric Nonlinear Directional Coupler

Asymmetric dual core nonlinear directional couplers that include an increasing self phase modulation profile are examined. The asymmetry is associated to the nonlinear refractive index profile of one of the channels (direct channel). Looking at the transmission characteristics of the device, through the direct channel, one observe that, when pumping in the direct channel, there is a decrease in the critical power which is lower compared with the symmetric coupler, however the critical power is a single valued function of the nonlinearity. For the pump power in the cross channel the transmission function of the coupler present regions of multistability, where the coupler presents more than one critical power for certain values of the self phase modulation index. For the studied profiles one region of multistability was observed, where three possible critical powers were seen. It is concluded that the asymmetry leads the coupler to operate in a multivalued function of the critical power for certain values of the nonlinear parameter. To operate the asymmetric coupler in a single valued region for the critical power one has to avoid the multistable region of the device.

A laboratory test unit for exhausted gas cleaning by electron beam and combined electron beam–microwave irradiation

At the Electron Accelerator Laboratory, NILPR, Bucharest developed a small laboratory test unit (max. gas flow rate=1 Nm 3/h) for exhaust gas cleaning by means of electron beam and combined electron beam–microwave irradiation. The aim of these methods is to obtain the concomitant removal of the NO x and SO 2 by precipitation with ammonia. Several parameters such as residence time and dose, reaction temperature, argon and NH 3 concentration, etc. were investigated. The removal efficiencies were: only for electron beam irradiation 63–80% for SO 2 and 0–63% for NO x ; for combined electron beam–microwave treatment 68–95% for SO 2 and 0–70% for NO x . Also, the presence of a small concentration of argon in the irradiated gaseous mixture increases the SO 2 removal efficiency (between 5% and 10%) for both electron beam and electron beam–microwave treatment. As electron beams generator was used the Linear Accelerator ALID-7 (5.5 MeV, 670 W). The microwave applicator consists of a power-controlled generator with a 2.45 GHz magnetron of 850 W maximum output power, a launcher to fit to waveguide WR430, a dual directional coupler and a three stub tuner for impedance matching. Our tests also demonstrated that the combined method electron beam–microwave irradiation, due to the additional use of microwave energy, leads to the decrease of the electron beam average power from 30% to 50%, at the same removal efficiency.

Transfer of non-classical properties in dual channel directional coupler

Quantum uncertainties of the quadratures and the photon statistics are analyzed in the coupling interaction between two modes of radiation via a dual channel directional coupler. The motivation of this work is to control the quantum properties of one light beam by another. Under the rotating wave approximation we show that if one of the modes is coherent (classical) and the other one squeezed, then the squeezing and non-Poissonianness of the photon statistics can be induced in the coherent mode. It is also shown that the transferred squeezing and non-classical number statistics in the second mode is of a new type. In the affected mode the squeezed quadrature remains squeezed, whereas the other quadrature is anti-squeezed, throughout except at the times where both of them return to a coherent value. The photon number of the affected mode shows both sub-Poissonian and super-Poissonian statistics as time evolves.

An improved calibration technique for on-wafer large-signal transistor characterization

The on-wafer measurement of complex quantities and absolute power levels of active devices is truly significant for nonlinear device characterization and modeling. An original procedure, which allows one to perform both the vector and the power calibrations at the RF wafer probe tips used for on-wafer measurement of two-port devices, is presented. The measurement system is based on an automatic vector network analyzer with coaxial directional couplers and RF coplanar wafer probes. A new error model of the dual directional coupler, which samples the power waves traveling at device output, allows one to take advantage of the coaxial section at the output of the measuring system for calibrating the power level up to the on-wafer probe tips. >

Microwave Components Using Ferrimagnetic Pastes

Ferrimagnetic pastes have been developed using Mg-Mn, Mn-Ni, Li, and Cu-doped magnesium ferrite aluminate and YIG powders. Isolators and circulators fabricated using these pastes on alumina substrates have been partly reported earlier. These devices exhibited higher insertion losses compared to those on YIG/ferrite substrates. Photomicrographs of Li-ferrite have been taken and these reveal cracks which may be responsible for high loss. The thermal co-efficient of expansion has also been found for this paste.Thick-film dual directional couplers have been fabricated using the field-displacement phenomena in wide microstrip lines. The coupling from one auxiliary line to the other on either side of the wide line can be changed by switching the polarity of the magnetic field. The performances of these devices have been compared with those on ferrite substrates over the frequency range from 2 to 8 GHz. A bandwidth of 600 MHz for a 15-dB coupler has been obtained with Li-ferrite paste.

Reappraisal of computer-corrected network analyser design and calibration

A rigorous analysis is carried out of a typical dual-directional coupler network analyser to demonstrate the application of a new circuit analysis technique based on the principle of matrix renormalisation, described in a companion paper, to cascaded multiport networks. The manner in which previously published calibration equations were derived is explained in detail. The analysis is carried out external to the network in terms of voltage excitation and the voltage responses at the accessible ports of the network under mismatched conditions. Each section of the network is represented by a generalised scattering matrix defined in terms of voltage-wave S-parameters with complex normalisation. In this manner, a knowledge of the internal flow paths of the network is unnecessary, in contrast to the flowgraph method employing the nontouching loop rule. The analysis shows that current methods of network analysis, based on the power-flow concept, have given rise to certain misconceptions because source mismatch does not contribute to systematic error-as is generally believed. In addition, these misconceptions appear to have led to the adoption of general design principles for network analysers that are unnecessarily complicated because the effects of mismatches, discontinuities and poor directivity can be completely eliminated by calibration in terms of air-dielectric line standards, provided that all port mismatches are invariant between the reflection and transmission modes of operation.

Bulk nuclear polarization of solid3He

Measurements are given on the bulk nuclear spin polarization in a liquid-solid3He mixture cooled by compressional cooling to below 5 mK in a magnetic field of 54.5 kG. Owing to the low Pauli spin susceptibility of liquid3He, the observed polarization is primarily due to solid3He. A maximum average nuclear polarization of 47% was observed, although the corresponding solid3He polarization is believed to be higher. Our novel detection system, using a dual directional coupler for cw NMR, is a simple and versatile means of working in the awkward frequency range around 180 MHz. We also report transient heating measurements in the3He system which indicate that the internal thermal equilibrium time in bulk solid3He on the3He melting curve appears to be quite short (less than 5 min) at these temperatures. One type of transient measurement is complicated by the dramatic effect of the contribution of the3He nuclear magnetization to the total local magnetic field. This contribution is considered via a simple model.

Dual adjacent directional coupler

The design of a compact dual directional coupler, which can be readily broadbanded using existing published data, is presented. The two coupled output transmission lines are laterally aligned on opposite sides of the main transmission line. Experimental results of a 0.3–2.0GHz 23dB coupler are presented.