Short-circuit Termination Research Articles

Parameter extraction method for reflection-asymmetric bianisotropic metamaterial slabs using one-port measurements

An effective microwave method is developed for extracting electromagnetic properties of bianisotropic metamaterial (MM) slabs. As a non-iterative method, it utilizes only the one-port (air-backed and metal-backed MM slab) scattering (S-) parameter measurements. This is a useful feature especially for vector network analyzers, such as MS46131A, MS46121B, and R60, performing only one-port S-parameter measurements. Electromagnetic properties of a bianisotropic MM slab formed by C-shaped resonators are measured by an X-band (8.2–12.4 GHz) rectangular waveguide setup. The effect of any gap between the short-circuit termination for metal-backed measurements and the end of the MM slab on extracted electromagnetic properties is also examined for evaluating the possible error for proposed method.

Beamwidth-Reconfigurable Circularly Polarized Slot Antenna Based on Half-Mode Substrate-Integrated Waveguide

Beamwidth-reconfigurable antennas are useful for the intersatellite link of low earth orbit formation flying and constellation, as they prevent unauthorized satellites from eavesdropping. In this article, a circularly polarized slot array antenna based on a half-mode substrate-integrated waveguide (HMSIW) for the K-band beamwidth reconfiguration is proposed using a new radio frequency (RF) switch structure and a pair of modified −45° and +45° linearly polarized HMSIW slot arrays for the dual operation of a single-pole double-throw (SPDT)/a power divider (PD) and easy integration with other components, respectively. The RF switch structure consists of a T-junction PD, λ/4 lines, and beam lead PIN diodes with current control resistors and without a DC block circuit for low DC power consumption and size reduction. The −45°/+45° linearly polarized HMSIW slot arrays providing linear and circular polarizations (LP and CP, respectively) are operated for CP. The use of a short-circuited termination instead of dissipative termination results in easier integration with other components because the 16 radiating slots consume most of the input power. The dimension of the beamwidth-reconfigurable antenna including the bottom metal layer is 157.2 × 23.3 × 0.254 mm3 (12.5λ0 × 1.86λ0 × 0.0202λ0). The RF switch for the SPDT shows the insertion losses of 1.8–2.3 and 16.7–24.2 dB and an isolation of 20.9–33.4 dB for both outputs within the 10-dB bandwidth. The RF switch for the PD has an insertion loss of 3.9–4.8 dB. The one- and two-antenna operation modes of the CP antenna provide the gains of 9.44 and 6.99 dBic, the axial ratios of 2.24 and 3.47 dB, and the horizontal beamwidths of 35.8° and 78.2°, respectively.

Branch module for an inductive voltage adder for driving kicker magnets with a short circuit termination

For driving kicker magnets terminated in a short circuit, a branch module for an inductive voltage adder has been designed and assembled. The module has been designed for a maximum charging voltage of 1.2 kV and an output current of 200 A considering the current doubling due to the short circuit termination. It features three consecutive modes of operation: energy injection, freewheeling, and energy extraction. Therefore, the topology of the branch module consists of two independently controlled SiC MOSFET switches and one diode switch. In order not to extend the field rise time of the kicker magnet significantly beyond the magnet fill time, the pulse must have a fast rise time. Hence, the switch for energy injection is driven by a gate boosting driver featuring a half bridge of GaN HEMTs and a driving voltage of 80 V. Measurements of the drain source voltage of this switch showed a fall time of 2.7 ns at a voltage of 600 V resulting in a voltage rise time of 5.4 ns at the output terminated with a resistive load. To meet both the rise time and current requirements, a parallel configuration of four SiC MOSFETs was implemented.

Feasible Extraction Method for Electromagnetic Properties of Multilayer Metamaterials With Short-Circuit Termination

An extraction technique is proposed for electromagnetic characterization of metal-backed multilayer metamaterial (MM) structures demonstrating reflection-asymmetric property. It uses recursive scattering parameters for direct and reversed configurations of a multilayer structure. The algorithm was validated by comparing the extracted electromagnetic properties of multilayer structures composed of different MM unit cells with those determined by one-layer-only S-parameter methods. Two-layer and three-layer multilayer structures composed of MM slabs with C-shaped and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> -shaped rings and an FR4 material were fabricated and measured for experimental validation. A sensitivity analysis was also conducted to quantitatively evaluate the performance of our method against a small air gap between the multilayer structures and the short-circuit termination and between adjacent MM slabs within these structures. Strong agreement was observed between the resulted obtained using our method and measurements.

Monitoring the natural recovery of potential induced degradation in poly-crystalline photovoltaic modules

Potential induced degradation (PID) is a defect that has a severe effect on the performance of photovoltaic (PV) modules in field conditions. It is caused by leakage currents and the accumulation of sodium ions (Na+) between the anti-reflective coating and the encapsulation. In the experiment reported on here, PID was artificially induced through a PID stress test, where the surface of a poly-crystalline p‑type module was covered with an aluminium sheet connected to the positive terminal of a high voltage power supply (1000 V), while the short-circuited module terminals was biased to the negative terminal. This stress test was applied to two similar poly-crystalline p‑type modules, A and B, for 48 hours and 20 hours respectively. The duration of the stress test determines the degree of PID severity induced. The length of the test resulted in Module A’s power decreasing by 88% and Module B’s by 40%. Electroluminescence and current-voltage measurements were taken at regular intervals over a period of more than a year to monitor the natural recovery of the modules. These measurements show that the natural recovery of severe PID modules is possible, but slow. After the test period, the maximum power of Module A and Module B had recovered to 63% and 96% of the original level. PID experienced in the field is generally less severe than for the modules in this study, so PID recovery could be achieved by adopting a process of setting affected strings at open-circuit in turns.

Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination

Requirements for an Inductive Voltage Adder as Driver for a Kicker Magnet with Short Circuit Termination

28 GHz dual‐layer substrate integrated waveguide slot array antenna combined with quad‐polarization

This article presents a compact slot array antenna combined with quad-polarization for mm-wave applications. A novel modified short-circuit termination with inclined slot is proposed in this paper and a dual-layer structure has been adopted to achieve miniaturization and also to design a circular polarization feeding network. Two linear polarization feeding networks are designed independently so that four polarization states can be realized. Four polarization states, namely vertical linear polarization, horizontal linear polarization, left hand circular polarization (LHCP), and right hand circular polarization (RHCP) can be switched by feeding corresponding ports. Judging from impedance matching and axial ratio (AR), the antenna exhibits wide bandwidth. The −10 dB impedance bandwidth and 3 dB AR bandwidth are better than 14.2% (26-30 GHz) with gain about 5-8 dBic for both LHCP and RHCP. The linear polarization states have |S11| < −10 dB and a gain of 5-7 dBi over 26.5-29.5 GHz (10.7%). The size of the slot array antenna is 65 × 65 × 1.156 mm and measured results are consistent with simulations.

Miniaturized and enhanced bandwidth Marchand balun using CSRR

A novel and miniaturized Marchand balun is proposed using two quarter-wave edge coupled transmission line and two complementary split-ring resonators (CSRR) unit cell in the ground plane. These coupled lines are joined with the help of an uncoupled microstrip line. The short circuit and open circuit terminations are assigned at the specified ports. Two rectangular shaped CSRR cells improve the circuit performance. A step impedance technique has been applied at the balanced ports to enhance the bandwidth. This proposed design produces a fractional bandwidth of 18.75% at the centre frequency with a maximum magnitude and phase imbalance of 0.56 dB and 0.85°. This design occupies a total circuit area of 0.515 λg (30.72 mm) × 0.279λg (16.63 mm). The circuit has been designed at 2.4 GHz centre frequency using low-cost FR4 substrate material. The simulated and measured results are in acceptable accord in terms of magnitude and phase response.

Two-Level Stability Analysis of Complex Circuits

A new methodology is proposed for the small- and large-signal stability analysis of complex microwave systems, containing multiple active blocks. It is based on a calculation of the system characteristic determinant that ensures that this determinant does not exhibit any poles on the right-hand side (RHS) of the complex plane. This is achieved by partitioning the structure into simpler blocks that must be stable under either open-circuit (OC) or short-circuit (SC) terminations. Thus, the system stability is evaluated using a two-level procedure. The first level is the use of pole-zero identification to define the OC- or SC-stable blocks, which, due to the limited block size, can be applied reliably. In large-signal operation, the OC- or SC-stable blocks are described in terms of their outer-tier conversion matrices. The second level is the calculation and analysis of the characteristic determinant of the complete system at the ports defined in the partition. The roots of the characteristic determinant define the stability properties. The Nyquist criterion can be applied since, by construction, the determinant cannot exhibit any poles in the RHS. In addition, one can use pole-zero identification to obtain the values of the determinant zeroes. Because the determinant is calculated at a limited number of ports, the analysis complexity is greatly reduced.

Reflection-Based Short Pulse Generation in CMOS

In this letter, a low cost, compact, and systematic method for generating a short pulse and efficiently delivering it to low impedance loads is proposed. The load can be a resistive on-chip or off-chip load, an antenna, or another stage such as a power combiner. The technique is inspired by time-domain reflectometry from a short-circuited termination. The technique is fully compatible with the CMOS technology. To show the feasibility of the idea, two chips are fabricated and tested in a low cost 0.11- $\mu \text{m}$ CMOS process with fT ≈ 80GHz. The full-width at half maximum (FWHM) of the pulses are 6.8ps and 8.8ps, and the amplitudes over a 50 ${\Omega }$ load are 0.62V and 1V. Either of the chips occupies ${1160\times 540\,{\mu \mathrm {m}}^{2}}$ in area.

Open/short circuit terminations of efficient ACS-fed CRLH small antennas

A design of asymmetric coplanar strip-fed (ACS) CRLH antennas for multiband operation is presented in this paper. Two different possible termination of the antenna is discussed. Comparison between ACS short circuit and ACS open circuit termination confirm that the open circuit termination has extra resonance band. The antenna resonance frequencies were optimized for WIMAX/WLAN frequencies. The antennas have compact size of 13.5 × 26.5 mm2 thanks to the asymmetric configuration. The antenna has size reduction up to 50% as compared to the patch antennas which are operated as the same frequency bands. The antennas are tested experimentally to validate the agreement between simulated and measured data.

45 GHz Wideband Circularly Polarized Planar Antenna Array Using Inclined Slots in Modified Short-Circuited SIW

This paper presents a $Q$ -band planar circularly polarized (CP) antenna array with a wide bandwidth, in terms of both impedance matching and axial ratio (AR). A centered 45°-inclined slot in the broad wall of a substrate-integrated waveguide (SIW) with a modified short-circuited termination is first introduced to realize a wideband 45° linearly polarized radiation, incorporated with a pair of inductive vias for impedance matching. Then, orthogonally integrating two proposed slots with an SIW 90° directional coupler, a wideband CP element is designed and its beam exhibits a good AR over a relatively wide angular region in one direction. Following this, a two-layer SIW is employed to design a CP antenna array. Four CP elements are arranged in a rotational manner in the top layer, and they are sequentially fed by a four-way power divider in the bottom layer with an incremental phase delay of 90° to achieve a conical CP beam and higher gain. The performances of the power divider and cross-layer coupling slot are examined in the wide operating band. The proposed CP array antenna is prototyped at $Q$ -band, and measured results show that the antenna has $\vert S_{11}\vert dB, AR $\times \,\, 30$ mm $\times \,\, 1$ mm.

Wideband Bandstop Filter With Extreme Sharp Skirt Selectivity

A novel and simple wideband bandstop filter with extreme sharp skirt selectivity is proposed. The wideband bandstop response with multi-transmission zeros and large skirt-band attenuation rate is realized based on the modified coupled-line sections with open-/short-circuited termination and two quarter-wavelength transmission lines. In order to simultaneously improve stopband rejection (SR) and passband return loss, the gray boxes with different circuit structures are introduced. For demonstration, a designed prototype operating at 1 GHz with 64% relative bandwidth of 17-dB SR is simulated, fabricated, and measured.

Reducing the beam impedance of the kicker at the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

The present four-terminal kicker at the rapid cycling synchrotron (RCS) at the Japan Proton Accelerator Research Complex has the power-saving benefit that it allows beam extraction by doubling the excitation currents with two shorted ends. In this configuration, two terminals of the kicker are connected to the pulse-forming line while the other two are terminated in a short circuit. On the other hand, beam instabilities are excited in the RCS by the kicker beam impedances, which result from the short-circuit termination of the kicker. In this paper, we describe a scheme to reduce the beam impedance of the kicker using diodes (nonlinear devices), while retaining the benefit of the doubled kicker excitation currents. We employ a simulation technique to determine the beam impedance of the kicker, even when such nonlinear devices and long cables are included. The characteristic of beam impedance measured using the accelerated beams is well explained by that obtained from the simulation.

Keysight 3458A Noise Performance in DCV Sampling Mode

This paper describes an evaluation of the Keysight 3458A digital multimeter (DMM) noise performance. A DMM noise model is given in closed form for all ranges and integrating analog-to-digital converter (IADC) aperture times. When the DMM is used for sampling, different sources of noise contribute to the total noise of the sampled signal. Their combined effect was measured using both short-circuited input terminals and spectrally pure Josephson arbitrary waveform synthesizer. Both white noise and ${1/f}$ noise were evaluated. The results confirmed that the internal IADC can be used to measure DMM input referred noise when the IADC quantization noise is smaller than the instrument front-end analog circuitry-related noise. Further, it is shown that the DMM noise can be effectively measured with short-circuited input terminals when using double integer output format, but not always when using single integer output format. The manufacturer specifications were confirmed on all but the 100-V range.

A high selective filtering small size/dual band antenna using hybrid terminated modified CRLH cell

AbstractThis article presents a new small size dual band metamaterial antenna. The antenna is realized using a single cell of a suggested modified version of composite right left handed transmission line terminated by a hybrid capacitive loading with short circuit termination. The hybrid termination leads to decrease the size of the antenna whereas the modified composite right left handed cell configuration leads to introduce dual band antenna functionality at 2.5 and 2.92 GHz. The antenna size is only 31 × 26 mm2. Compared to, single band, non‐selective, conventional patch antenna, the size of the proposed antenna is only 9 and 11.5% at the two former frequencies, respectively. Despite the small size, the antenna gain is more than 3.5 dBi at the two operating frequencies. Moreover, the antenna has a high roll off beyond the operating frequency band which leads to high selective characteristics. The antenna can suppress 100% of the nearby signal power beyond its bands by 300 MHz at lower band and 200 MHz at upper band. The antenna design is discussed; the full wave simulation and experimental measurements are introduced for validating the results.

Generalized Stability Criteria for Power Amplifiers Under Mismatch Effects

Potential instability of power amplifiers (PAs) under mismatch effects is analyzed, with emphasis on the ease and generality of application of the stability criteria. The methodology is based on the evaluation of a large-signal version of the $\mu$ factor, considering mismatch effects in the fundamental frequency and three relevant sidebands: the baseband, the lower sideband and the upper sideband. This requires an outer-tier scattering-type conversion matrix of order 3 $\times$ 3 to be obtained, with the rest of sideband equations acting as an inner tier. It is taken into account that the circuit behaves nonlinearly with respect to the termination at the fundamental frequency. The consideration of three sidebands will enable the prediction of the two major forms of large-signal instability: incommensurable oscillations and frequency divisions by two. The analysis is preceded by an evaluation of the circuit own stability properties (proviso) under open and short circuit terminations at the sidebands, for all possible values of the termination at the fundamental frequency. Three different $\mu$ factors can be defined between any two ports of the scattering matrix. The analysis of the relationships between these factors and their continuity properties will allow the derivation of a single number able to characterize the PA potential instability for each fundamental-frequency termination. Results have been exhaustively validated with independent circuit-level simulations based on pole-zero identification and with measurements, using a variable output load and loading the PA with an antenna.

Direct characterization of plasmonic slot waveguides and nanocouplers.

We demonstrate the use of amplitude- and phase-resolved near-field mapping for direct characterization of plasmonic slot waveguide mode propagation and excitation with nanocouplers in the telecom wavelength range. We measure mode's propagation length, effective index and field distribution and directly evaluate the relative coupling efficiencies for various couplers configurations. We report 26- and 15-fold improvements in the coupling efficiency with two serially connected dipole and modified bow-tie antennas, respectively, as compared to that of the short-circuited waveguide termination.

High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\hbox{F}}^{-1}$</tex></formula> GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source–pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox{F}}^{-1}$</tex></formula> PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Omega$</tex></formula> resistor.

RESOLVING PHASE AMBIGUITY IN THE INVERSE PROBLEM OF REFLECTION-ONLY MEASUREMENT METHODS

We have applied the phase unwrapping technique to resolve the phase ambiguity problem arising from complex expressions of scattering parameters, for re∞ection-only measurement conflgurations, since, at some instances, only one side of the sample under test is accessible for electromagnetic measurements. We considered two difierent measurement conflgurations for testing the applicability of the phase unwrapping technique as: 1) two identical samples with difierent lengths ∞ushed by a short-circuit termination and 2) one sample shorted by a varying short-circuit termination. For each measurement conflguration, the underlying expressions for the re∞ection scattering parameters are derived. For both cases, we evaluated the suitability of the phase unwrapping technique by considering a highly-dispersive medium (distilled water) as our test sample. We note that continuity of the real part of the complex wavelength is a key issue in the unwrapping technique for (one-port) re∞ection-only measurements.