Wide Operating Frequency Range Research Articles

Optimization of a High-Frequency Current Transformer Sensor for Partial Discharge Detection Using Finite-Element Analysis

High-frequency current transformer (HFCT) sensors are widely used for partial discharge detection due to their versatility, high sensitivity, and wide bandwidth. This paper reports on a finite-element analysis (FEA) methodology that can be employed to optimize HFCT performance. The FEA model consists of accurate 3D representations of the sensor components. Two different FEA software modules were used in order to cover the wide operating frequency range of the sensor. The simulation computes the frequency response of the sensor in the range 0.3–50 MHz for various HFCT geometric and material parameters, specifically the number of winding turns, spacer thickness, aperture size, and core material. A prototype HFCT was constructed and the measured response compared with that of the simulation. The shapes of the responses were similar, with the simulated sensitivity being higher than the measured sensitivity by 1 dB on average. The measured low-frequency cutoff of the sensor was found to be only 0.05 MHz lower than that of the simulation.

Operation of a liquid-fueled and valveless pulse detonation rocket engine at high frequency

To increase the operating frequency and enhance the propulsive performance of a pulse detonation rocket engine (PDRE), a valveless mode with the purge gas based on liquid fuel was developed. Liquid gasoline, oxygen-enriched air, and nitrogen were utilized as fuel, oxidizer, and purge gas respectively. Supply of these propellants was controlled by the periodic pressure oscillations in the detonation tube. The purge gas with the highest supply pressure was filled into the detonation tube first. The fuel and oxidizer were injected after the inner pressure decaying to a relatively low level. This delay and the vaporization of the liquid fuel prevented pre-ignition of the fresh detonable mixture. The PDRE can work stably from 10Hz to 160Hz in this scheme. Fully-developed detonation waves were proved to be obtained successfully at a maximum frequency of 130Hz. Both oxygen volume fraction and supply pressure of the purge gas were tested to determine the limits for stable operation. The propulsive performance of a practical PDRE at a wide operating frequency range was also tested and the maximum thrust was obtained at 140Hz. Compared to the results without purge gas, introduction of a purge gas extends the ranges of supply pressure and operating frequency.

Integrated Magnetics and Multiferroics for Compact and Power-Efficient Sensing, Memory, Power, RF, and Microwave Electronics

The coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric (ME) coupling, including electric field control of magnetism, or vice versa, through a strain-mediated ME coupling in layered magnetic/ferroelectric multiferroic heterostructures. Strong ME coupling has been the enabling factor for different multiferroic devices, which, however, has been elusive, particularly at RF/microwave frequencies. In this paper, most recent progress on new integrated multiferroic devices for sensing RF and microwave electronics will be presented, including novel RF Nano-electro-mechanical systems ME resonators with picotesla sensitivity for dc magnetic fields and novel gigahertz magnetic and multiferroic integrated inductors with a wide operation frequency range of $0.3\sim 3$ GHz, a high quality factor close to 20, and a voltage tunable inductance of 50% $\sim 150$ %. At the same time, we will also demonstrate other tunable RF devices, including integrated non-reciprocal tunable bandpass filter with ultrawideband isolation more than 13 dB. These novel magnetics and multiferroic devices show great promise for applications, such as compact, lightweight, and power-efficient sensing, memory, RF, and microwave integrated electronics.

Design and evaluation of a downconverter based on MicroTCA.4

Modern low-level RF (LLRF) control systems of particle accelerators are designed to achieve extremely precise field amplitude and phase regulation inside the accelerating cavities. The RF field signal is usually converted to an intermediate frequency (IF) before being sampled by ADC. As the down-conversion is an important procedure of digital signal processing in LLRF system, designing a high performance and broad band downconverter compatible with various accelerators is important. In this paper, the design of a downconverter based on MicroTCA and its performance evaluation on different frequency points are presented. The major design objective of this module is a wider operating frequency range and more flexibility in application.

A 6.7 MHz to 1.24 GHz $\text{0.0318}\;{\text{mm}^{\text{2}}}$ Fast-Locking All-Digital DLL Using Phase-Tracing Delay Unit in 90 nm CMOS

In this paper, an all-digital delay-locked loop (ADDLL) with a phase-tracing delay unit (PTDU) has been proposed to achieve wide-operating frequency range, low power, and low cost. For the wide-range DLL, the long delay line is replaced by a PTDU which includes two gated ring oscillators (GROs) for generating the wide delay range with a reduced die area. According to the dual-loop control scheme in this work, the input clock rising edge and falling edge are tracked independently to ensure that the ADDLL output maintains the duty cycle of the input reference. Furthermore, the ADDLL utilizes an open-loop scheme to achieve fast lock time of five clock cycles for all supported input frequencies. The proposed ADDLL has been fabricated in TSMC 90 nm CMOS technology and supports a wide-operating frequency range from 6.7 MHz to 1.24 GHz within a small active area of ${0.0318}\;{\text {mm}^{2}}$ . The measured peak-to-peak and root-mean-square jitter at 1.24 GHz are 2.22 ps and 424.62 fs, respectively. The ADDLL consumes 14.5 mW while operating at 1.24 GHz.

Compact photonic crystal circulator with flat-top transmission band created by cascading magneto-optical resonance cavities.

A new type of compact three-port circulator with flat-top transmission band (FTTB) in a two-dimensional photonic crystal has been proposed, through coupling the cascaded magneto-optical resonance cavities to waveguides. The coupled-mode theory is applied to investigate the coupled structure and analyze the condition to achieve FTTB. According to the theoretical analysis, the structure is further optimized to ensure that the condition for achieving FTTB can be satisfied for both cavity-cavity coupling and cavity-waveguide coupling. Through the finite-element method, it is demonstrated that the design can realize a high quality, nonreciprocal circulating propagation of waves with an insertion loss of 0.023dB and an isolation of 23.3dB, covering a wide range of operation frequency. Such a wideband circulator has potential applications in large-scale integrated photonic circuits for guiding or isolating harmful optical reflections from load elements.

Low-Frequency, Low-G MEMS Piezoelectric Energy Harvester

This paper reports the design, modeling and fabrication of a novel MEMS device for low-frequency, low-g vibration energy harvesting. The new design is based on bi-stable buckled beam structure. To implement the design at MEMS scale, we further proposed to employ residual stress in micro-fabricated thin films. With an electromechanical lumped model, the multi-layer beam could be designed to achieve bi-stability with desired frequency range and excitation amplitude. A macro-scale prototype has been built and tested to verifies the prediction of the performance enhancement of the bi-stable beam at low frequencies. A MEMS scale prototype has been fabricated and tested to verify the frequency range at low excitation amplitude. The MEMS device shows wide operating frequency range from 50Hz to 150Hz at 0.2g without external proof mass. The same device with external proof mass has lower frequency range (< 10Hz) with boosted deflection amplitude.

An LTCC Coupled Resonator Decoupling Network for Two Antennas

An integrated low-temperature co-fired ceramic (LTCC) coupled resonator decoupling network (CRDN) for two coupled antennas is proposed in this paper. By virtue of LTCC technology, a second-order CRDN is realized by two tightly coupled lumped-element resonators in a volume of 3.2×2.5×1.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Theoretical analysis has revealed that a wide range of mutual admittance of a CRDN can be realized by choosing appropriate I/O coupling elements while the coupled resonators can be consolidated in an LTCC device. This “one-fit-all” feature allows for decoupling a wide range of coupled antennas with different form factors for a given frequency band. To prove the concept, two LTCC CRDNs for decoupling different forms of antennas working in the 2.45-GHz band are designed, fabricated, and tested. Measurement results have demonstrated that significant improvement in isolation can be achieved within a wide operating frequency range in all cases. The presented design theory and circuit topology are general and can be applied to both symmetric and asymmetric two-element antenna arrays.

A New High Precision Power Detector of Complex Voltage Signals

Abstract A current-mode bipolar power detector based on a novel synthesis of translinear loop squarer/divider is presented. The circuits consist of a single multiple-output current controlled current differencing transconductance amplifier (MO-CCCDTA), two current controlled conveyors (CCCII), and one resistor and one capacitor that are both grounded. The errors related to the signal processing and errors bound were investigated and presented in the paper. The PSpice simulation and experimental results are depicted, and agree well with the theoretical anticipation. The measurement results show that the scheme improves the accuracy of the detector to better than 0.04 % and wide operating frequency range from 50 Hz to 10 MHz. The maximum power consumption of the detector is approximately 5.80 mW, at ±1.2 V supply voltages.

V – I converter‐based voltage‐controlled oscillator with improved linear gain characteristic

A voltage–current (V–I) converter-based voltage-controlled oscillator (VCO) is adapted to generate multiple-phase clocks for clock and data recovery for a display driver IC. The proposed V–I converter changed the second-order current equation of the VCO to a first-order current equation of the VCO, to achieve a wide operating frequency range, a linear gain (K VCO) within a wide control voltage, low power, and a small area without any extra circuits, such as a low-to-full amplifier. Owing to the V–I converter, K VCO is changed from 8.43 to 2.05 MHz/mV with a wider V ctrl range, and its tuning range is changed from 114 to 452 MHz with a linear gain characteristic. The proposed VCO is implemented in a 1P6M 1.8 V technology and is suitable for the phase-locked loop used in flat-panel display interfaces that operate from 0.3 to 2 Gbit/s.

Reverse Current Characteristics of InP Gunn Diodes for W-Band Waveguide Applications.

InP is considered as the most promising material for millimeter-wave laser-diode applications owing to its superior noise performance and wide operating frequency range of 75-110 GHz. In this study, we demonstrate the fabrication of InP Gunn diodes with a current-limiting structure using rapid thermal annealing to modulate the potential height formed between an n-type InP active layer and a cathode contact. We also explore the reverse current characteristics of the InP Gunn diodes. Experimental results indicate a maximum anode current and an oscillation frequency of 200 mA and 93.53 GHz, respectively. The current-voltage characteristics are modeled by considering the Schottky and ohmic contacts, work function variations, negative differential resistance (NDR), and tunneling effect. Although no direct indication of the NDR is observed, the simulation results match the measured data well. The modeling results show that the NDR effect is always present but is masked because of electron emission across the shallow Schottky barrier.

7.3: Depletion‐Mode Oxide‐TFT Shift Register with Wide Operating Frequency Range for AMOLED Displays

This paper proposed a shift register circuit for GIP (Gate driver In Panel) in active matrix organic light emitting diode displays which enable cost innovation and narrow bezel. The shift register circuit which is made up with depletion mode oxide TFTs is designed to be driven at low operation frequency for power reduction in still image as well as to be driven at high operation frequency for motion picture quality improvement in moving image. However, it is especially difficult to operate at low frequency because oxide TFTs easily have negative Vth and zero gate‐source voltage turns out to be unable to shut down current path. The proposed shift register is integrated in a 15‐inch HD (1366 × 768, 105ppi) AMOLED panel, it is ensured that the shift register have wide operating frequency range from 1Hz to 240 Hz. In Addition, it is verified that the panel operates at high temperature(60°C) during 1,000 hours without any problems.

A wideband low‐spur 0.18‐µm CMOS phase‐locked loop with bandwidth calibration

SummaryThis paper presents a 0.18‐µm complementary metal‐oxide‐semiconductor wideband phase‐locked loop with low reference spurs. The dual‐level charge‐pump current calibration technique is proposed to maintain a constant loop bandwidth for wide operation frequency range and achieve low reference spurs. The first level charge‐pump current calibration is seamlessly incorporated in the automatic frequency band hopping control and the mechanism also ensures enough negative transconductance for the voltage‐controlled oscillator to function throughout the whole frequency range. The charge‐pump current mismatch is calibrated by the second level charge‐pump current calibration combined with the pulse‐width scaling technique. The operation frequency range of the phase‐locked loop covers from 4.7 GHz to 6.1 GHz. The measured phase noise is−116 dBc/Hz at 1‐MHz offset and the reference spurs are below−66.8 dBc. Copyright © 2015 John Wiley &amp; Sons, Ltd.

A Wide-Locking-Range Dual Injection-Locked Frequency Divider With an Automatic Frequency Calibration Loop in 65-nm CMOS

This brief presents a wide-locking-range injection-locked frequency divider (ILFD) that uses an automatic frequency calibration loop. The proposed ILFD uses the ring oscillator to provide the high division ratio with small chip area. A dual-injection scheme is proposed in order to achieve the wide locking range of the ILFD. The free-running frequency of the ILFD is automatically digitally calibrated to reflect the frequency of the injected signal from the voltage-controlled oscillator. To control the frequency of the ILFD, the load current is digitally tuned with 3-bit control signal. The ILFD is fabricated using 65-nm CMOS process, and by tuning the load current, it achieves the wide operation frequency range of 14.1-45.8 GHz. When the input signal of 30 GHz is injected, the locking range of the ILFD is 7.2 GHz, while the power consumption is 2.5 mW from a 1-V supply voltage.

Depletion Mode Oxide TFT Shift Register for Variable Frame Rate AMOLED Displays

This letter demonstrates a shift register circuit at the backplane of depletion mode oxide thin-film transistors (TFTs), which can cover variable frame rates for low-power active matrix organic light emitting diode (AMOLED) displays. The proposed scheme focuses on the stable gate control of a pull-up TFT by securing the charging and discharging paths at the wide operating frequency range. In a prototype high-definition (HD: 1366 × 768) AMOLED panel, it is ensured that fabricated shift registers operate at the wide frame frequency range from 1 to 240 Hz. The measured current consumptions are 30, 4, 6, and 5.8 mA for four clock signals, VGH of 24 V, VGL1 of -6 V, and VGL2 of -14 V at a frame rate of 120 Hz.

Pulsewidth control loop with a frequency detector for wide frequency range operation

A pulsewidth control loop (PWCL) with a frequency detector for wide frequency range operation is presented. The proposed PWCL is implemented with a duty cycle controlled circuit and frequency detector to correct the wide range frequency and duty cycle of the input clock. The duty cycle controlled circuit is able to modify the gain with different frequency and duty cycle ranges. The frequency and duty cycle of the input clock are detected by the frequency detector. The frequency detector is based on a ring oscillator and the input clock duty cycle and frequency are detected within two input clock cycles. The proposed circuit has been fabricated in a 0.35μm CMOS technology. The proposed circuit generates the output clock of 50% duty cycle with the input range from 20% to 80% and frequency range 50–800MHz. The measured duty cycle error is less than 1% within the frequency range from 50MHz to 800MHz.

Wireless Power Transfer System with an Asymmetric 4-Coil Resonator for Electric Vehicle Battery Chargers

This paper proposes a high-efficiency wireless power transfer system with an asymmetric four-coil resonator. It presents a theoretical analysis, an optimal design method, and experimental results. Multicoil systems which have more than three coils between the primary and secondary side provide the benefits of a good coupling coefficient, a long transfer distance, and a wide operating frequency range. The conventional four-coil system has a symmetric coil configuration. In the primary side, there are source and transmitter coils, and the secondary side contains receiver and load coils. On the other hand, in the proposed asymmetric four-coil system, the primary side consists of a source coil and two transmitter coils which are called intermediate coils, and in the secondary side, a load coil serves as a receiver coil. In the primary side, two intermediate coils boost the apparent coupling coefficient at around the operating frequency. Because of this double boosting effect, the system with an asymmetric four-coil resonator has a higher efficiency than that of the conventional symmetric four-coil system. A prototype of the proposed system with the asymmetric four-coil resonator is implemented and experimented on to verify the validity of the proposed system. The prototype operates at 90 kHz of switching frequency and has 200 mm of the power transmission distance between the primary side and the secondary side. An ac-dc overall system efficiency of 96.56% has been achieved at 3.3 kW of output power.

Three dimensional passivated-electrode insulator-based dielectrophoresis.

In this study, a 3D passivated-electrode, insulator-based dielectrophoresis microchip (3D πDEP) is presented. This technology combines the benefits of electrode-based DEP, insulator-based DEP, and three dimensional insulating features with the goal of improving trapping efficiency of biological species at low applied signals and fostering wide frequency range operation of the microfluidic device. The 3D πDEP chips were fabricated by making 3D structures in silicon using reactive ion etching. The reusable electrodes are deposited on second glass substrate and then aligned to the microfluidic channel to capacitively couple the electric signal through a 100 μm glass slide. The 3D insulating structures generate high electric field gradients, which ultimately increases the DEP force. To demonstrate the capabilities of 3D πDEP, Staphylococcus aureus was trapped from water samples under varied electrical environments. Trapping efficiencies of 100% were obtained at flow rates as high as 350 μl/h and 70% at flow rates as high as 750 μl/h. Additionally, for live bacteria samples, 100% trapping was demonstrated over a wide frequency range from 50 to 400 kHz with an amplitude applied signal of 200 Vpp. 20% trapping of bacteria was observed at applied voltages as low as 50 Vpp. We demonstrate selective trapping of live and dead bacteria at frequencies ranging from 30 to 60 kHz at 400 Vpp with over 90% of the live bacteria trapped while most of the dead bacteria escape.

A Practical Approach for Controlling the Shape of the Radiation Pattern of a Microwave Log-Periodic Antenna for Wideband Applications [Antenna Applications Corner

The log-periodic antenna (LPA) is a wideband frequency-independent antenna, used in many applications including direction-finding (DF) receivers. The direction finding is an important parameter measured by a direction-finding receiver in electronic support measures (ESM) systems. Amplitude-comparison direction finding (ADF) is one of the widely used angle-of-arrival measurement techniques in electronic support measures systems across the world. Many EW engineers have derived the mathematical equation for the estimation of the angle of arrival based on this popular technique. The angle of arrival accuracy using this technique depends on the number of antennas used in the configuration, channel imbalances, the beamwidth, and the shape factor of the antennas. To obtain good angle-of-arrival accuracy with the amplitude-comparison technique, the log-periodic antenna is one suitable antenna. Normally, electronic support measures systems are wide open in frequency (the bandwidths of electronic support measures receivers are a few thousands of MHz), and hence the antennas exhibit nearly the same beam shape (beamwidth and shape factor) over these wide operating frequency ranges so as to have a uniform angle-of-arrival error distribution across the frequency spectrum. However, a log-periodic antenna offers some variations in half-power beamwidth over a wide frequency spectrum at microwave frequency ranges, which is reasonably good, but is not enough to obtain uniform angle-of-arrival error patterns throughout the operating frequency range. Similarly, a uniform shape factor is also important across the bandwidth. The radiation beam of a log-periodic antenna over a wide operating frequency range thus need to be controlled. A practical solution to this problem, along with experimental results, are presented in the current paper.

Half-Rate Clock-Embedded Source Synchronous Transceivers in 130-nm CMOS

This paper describes the characteristics of a half-rate clock-embedded source-synchronous signaling scheme to identify its constraints and to optimize the transceiver topology in the presence of a band-limited channel. The proposed signaling combines the half-rate clock to the common mode of the differential data with its mixing phase off by 0.5 UI. Two transceivers with resistive-load and inductive-load receivers are implemented in 130-nm CMOS technology to verify their feasibility for use as serial links. The prototype transceivers achieve a wide operating frequency range 2.25-6 and 5.6-8 Gb/s, respectively, satisfying bit error rate of <;10 -12 measured at Tx-Rx linked configuration by 5-in-long FR4 trace with 2 31 -1 PRBS. The power efficiencies of transceivers at maximum data rates are 6.4 and 4.6 mW/Gb/s, respectively.