Frequency Link Research Articles

Hyperfine structure and absolute frequency determination of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of [formula omitted] near 532 nm

Hyperfine structures of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of molecular iodine at the blue end of the tuning range of a frequency-doubled Nd:YAG laser are measured by using two I 2-stabilized lasers. The absolute frequencies of the observed transitions are determined by a frequency link to an optical frequency reference (the R(5 6)32-0:a 10 hyperfine transition), using an optical frequency comb generator. The observed hyperfine transitions are good frequency references for both frequency-doubled Nd:YAG and Nd:YVO 4 lasers in the 532 nm region. High-accurate hyperfine constants are obtained for the P(1 4 2)37-0 transition by fitting the measured hyperfine splittings to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions.

Three-Phase Immittannce Converter

The immittance converter has an input impedance that is proportional to the admittance of a load connected across it's output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently a constant voltage source is converted into a constant current source and a constant current source into a constant voltage source. The immitance converters consist of only the passive elements reactor L and capacitor C are suitable to use in a high frequency link of power electronics.We proposed some types of immittance converters and some applications to power electronics equipment. In this paper, we propose a new 3-phase immittance converter consist of each three L, C elements to obtain an alternating current source from a 3-phase voltage source without control.This paper shows the configuration of the new 3-phase immittance converter that operates on either the anti-phase or the in-phase between the input voltage and the output voltage, and it's voltage-current transformation characteristics and efficiency characteristics.

Current-Sensor-Less Control of High Frequency Link Type Inverter for Photovoltaic System

It is required to use the DC current sensor in the photovoltaic system which is controlled by the maximum power point tracking. To eliminate this expensive sensor, this paper shows how to estimate DC output current of PV array by using the main capacitor voltage and on-duration of the main semiconductor switch in high frequency link type inverter. The experimental data show the proposed technique is helpful to practical use.

Accurate frequency atlas of molecular iodine near 532 nm measured by an optical frequency comb generator

An optical frequency comb generator (OFCG) at 1064 nm with a modulation frequency of 2 GHz is developed for an accurate optical frequency link between iodine absorption lines near 532 nm. With the OFCG, we have measured frequency differences between seventeen 127 I 2 transitions with a measurement uncertainty of about 240 Hz (relatively 4.3×10 −13), which is mainly contributed from the frequency repeatability of iodine-stabilized Nd:YAG lasers. The measured transitions provide an attractive frequency reference network and are excellent candidates for the practical realization of the meter.

A comparative study on dimming control methods for electronic ballasts

This paper presents a comparative study on the performance characteristics between the variable switching frequency and variable DC link voltage control schemes for the dimming operation of electronic ballasts using a half-bridge series-resonant parallel-loaded inverter. Attributes under investigations include (1) average input current of the inverter; (2) dimming characteristics; (3) variations of the filament power and starting voltage throughout the dimming range; (4) dead time boundaries for ensuring zero-voltage-switching in the inverter. An approximated fundamental-frequency model that includes the characteristics of the nonlinear lamp resistance and filament resistance is used. Theoretical predictions are favorably verified with the experimental measurements in two 36 W Ballast-lamp systems.

Radio resource management in multiple-chip-rate DS/CDMA systems supporting multiclass services

This paper is concerned with radio resource management in multiple-chip-rate (MCR) DS/CDMA systems accommodating multiclass services with different information rates and quality requirements. Considering both power spectral density (PSD) over a radio frequency (RF) link and the effect of RF input filtering on the receiver in MCR-DS/CDMA systems, criteria for call admission are presented and the system performance is derived. The system performance in MCR-DS/CDMA systems is strongly affected by radio resource management. A minimum total-power-increment-based resource management scheme for an efficient resource management is proposed. The performance of this scheme is compared with that of a random-based resource management scheme in terms of the new call blocking probability, handoff call dropping probability, and normalized throughput. In addition, in order to reduce the handoff call dropping rate, reallocating subsystems assigned for communicating calls is proposed. The minimum total-power-increment-based resource management scheme yields better performance than the random-based resource management scheme for multiclass services.

Optical frequency link between an acetylene stabilized laser at 1542 nm and an Rb stabilized laser at 778 nm using a two-color mode-locked fiber laser

We have demonstrated optical frequency link of two frequency-stabilized laser diodes operating at 1542 nm (a rotational-vibrational line of isotope acetylene molecule) and 778 nm (an Rb two photon transition) using a two-color mode-locked fiber laser. The laser produces a frequency comb (300 fs pulse) in the 1560 nm region and, through the second harmonic generation (SHG) process, another frequency comb (100 fs pulse) in the 780 nm region. Beat note signals have been observed between each of the stabilized laser radiation and a mode of the mode-locked fiber laser in the vicinity of the stabilized laser frequency. The S/N ratios were 25 dB and 30 dB with 100 kHz resolution bandwidth for beat notes at λ=1542 nm and λ=778 nm, respectively. Preliminary result has shown the potential of the system for frequency measurements with the accuracy of below 100 kHz. This limitation will be overcome by improving the frequency counting system using a phase-locked tracking oscillator and installing a PZT element in the fiber laser cavity. Supposing the accuracy of the mode spacing is similar to the case of a mode-locked Ti:sapphire laser, the accuracy of kHz level is very presumable.

Combined Franz-Keldysh and quantum-confined Stark effect waveguide modulator for analog signal transmission

A novel approach to the design of electroabsorption waveguide modulators for use in broadband, analog radio frequency (RF) links is presented. The approach utilizes a linear combination of two electroabsorption effects (the Franz-Keldysh effect and the quantum-confined Stark effect) to improve the spurious-free dynamic range of the waveguide modulator. Measured transfer curves verify simultaneous improvement in linearity and modulation efficiency for an exemplary combination structure. Residual absorption is modeled to determine the impact on modulation efficiency.

Concept of a wireless indoor video communications system

The aim of this paper is to describe and specify the concept of a future wireless indoor video communications system. The radio frequency link operating in the 2.4/5.8 GHz ISM-band is considered as the transmission medium. First, the general concept of the system which is based on a decentralized/distributed topology is illustrated in detail. Then, the physical layer of the system which is based on a combination of TDMA and FDMA is examined. The system supports variable rate transmission and is flexible. As modulation both QPSK and 16-QAM are taken into account. The channel coding is based on a powerful Reed–Solomon code. The control signals, sent at the beginning of the TDMA frames, with carrier-sensing based on correlation are used to detect the free time-slots. An example of the access to the network is given. Furthermore, the simulation results with a link-budget evaluation are analyzed. It is shown that the maximum data rate at 2.4 GHz, using a 16-QAM modulation can be up to 26.8 Mbit/s.

An externally powered, multichannel, implantable stimulator-telemeter for control of paralyzed muscle.

An implantable integrated stimulator and telemetry system has been developed. The system is capable of fulfilling the stimulus and telemetry needs of advanced functional neuromuscular stimulation (FNS) applications requiring multiple channels of stimulation and multiple channels of sensor or biopotential sensing. This system provides a command control structure, an inductive radio frequency link providing power to the implant device as well as two-way transcutaneous communication, an ASIC for decoding the command and for providing functional control within the implant, and modular circuitry providing the application specific implant functions. Biocompatible hermetic packaging, lead systems, and in-line connectors suitable for long-term implantation, provide encapsulation for the circuitry and access to the electrodes and sensors used in the application. The first implant configuration realized from this modular system is targeted for clinical implementation in persons with tetraplegia at the C6 level for restoration of hand function, using wrist position as the command control source. The implant device realized has ten channels of stimulation and telemetry used to control and sense a joint angle transducer implanted in the radio-carpal joint of the wrist. A prototype device has been fabricated and is undergoing testing in an animal.

Implantation of a 16-Channel Functional Electrical Stimulation Walking System

A 16-channel electrical stimulation system was implanted in a 39-year-old patient with T10 paraplegia to restore sit to stand, walking, and exercise functions. System implantation required two surgical sessions. In the first session, the posterior muscle set consisting of bilateral semimembranosus, adductor magnus, and gluteus maximus muscles were exposed and epimysial electrodes sutured at the point of greatest muscle contraction. Closed double helix intramuscular electrodes were implanted in the erector spinae. Two weeks later, epimysial electrodes were attached to the eight anterior muscles consisting of the tibialis anterior, sartorius, tensor fasciae latae, and vastus lateralis with all 16 electrode leads passed to the anterior abdominal wall. The electrodes were connected to two eight-channel stimulators placed in the iliac fossae, and the system was checked by activating the individual muscles. The implanted stimulators received stimulation instructions and power via a radio frequency link to an external control. Stimulation patterns for standing, walking, sitting, and exercise functions were chosen from a preprogrammed menu via a finger key pad. After 3 weeks of restricted patient activity, all electrodes stimulated either the target muscle or had an acceptable spillover pattern. The patient is undergoing a 16-week rehabilitation course of stimulated exercises gradually increasing in intensity. At the conclusion, the goal is to discharge the patient with the system for spontaneous use. Although long term followup is required to determine system reliability, preliminary clinical results indicate that targeted, repeatable, functional muscle contractions in the lower extremity can be achieved with a system consisting of epimysial electrodes.

A new theoretical formulation for calculation of the specific attenuation due to precipitation particles on terrestrial and satellite radio links

The propagation of high frequency electromagnetic waves through rain is affected by absorption and scattering, which both lead to signal attenuation on satellite or terrestrial super high frequency (SHF) and extremely high frequency (EHF) links. Many factors govern rain effects on waves propagating in the atmosphere, namely raindrop size distribution, rain cumulative distribution, water temperature, refractive index and operating frequency. A high degree of accuracy in the calculation of specific attenuation caused by rain (attenuation per km) is of importance when planning high frequency radio communication systems. Until now, the kR α expression has been widely used for such calculations. This relationship in which R (mm/h) represents the rain rate, α and k parameters determined for each frequency by interpolation, can be considered to be a compromise between the complexity and a simplified approach of the Van de Hulst relationship. In this paper, we present a new theoretical model based on physical laws and allowing the calculation of specific attenuation caused by all kinds of hydrometeor particles on high frequency electromagnetic waves. This method, which we derived from the forward scattering amplitude and the Van de Hulst relationship, is governed by wave polarization, the wave incidence angle, the radio link operating frequency, and precipitation particle size distribution in the climate of interest. Its application gives theoretical results which are in very good agreement with data gathered on terrestrial or earth-satellite links in several localities around the world. This new proposed model can be easily used and will constitute a very useful tool for evaluating satellite and terrestrial radio link performances, mainly in the future which will bring an expansion of high frequency satellite systems.

A High FrequencyLink DC/AC Converter using a Three-Phase Output PWM Controlled Cycloconverter.

High frequency link DC/AC converters for UPS are characterized by small size and weight of the isolation transformers. Two types are considered in the high frequency link DC/AC converters. One is called a DC/DC converter type, and the other is a cycloconverter type. The DC/DC converter type can be constructed easily, but the efficiency is low because of many steps of power conversion The system configuration for the cycloconverter type with a single phase output has been proposed, but the cycloconverter type which directly converts high frequency voltage into three phase line voltages is not studied.In this paper, the system configuration and the control method of the high frequency link DC/AC converter with three-phase output voltages using the PWM cycloconverter are proposed. This system can control flow of power bidirectionally, and charge the DC power supply and compensate instantaneous reactive power. Simulations and experiments are carried out to confirm the feasibility of the proposed system.

High Frequency Link Type DC/AC Converter for UPS with a New Voltage Clamper.

This paper proposes a new type of high frequency DC/AC converter developed for flexible, compact and high efficiency uninterruptible power supply (UPS) systems. The proposed DC/AC converter consists of a high frequency inverter, a high frequency transformer and a cycloconverter with a new voltage clamper. This cycloconverter is capable of being operated by both sourcecommutation and self-commutation (commutation by turning off the switching device). Consequently, by choosing between the two commutating methods, based on consideration and the internal voltage drop caused by commutating reactance, a commpact and efficient UPS can be realized. The voltage clamper effectively reduces power loss of the conversion system. Fabrication of a 10 kVA high frequency link type DC/AC converter is described and its loss reduction effect is demonstrated.

Bilateral series resonant inverter for high frequency link UPS

A bilateral series resonant inverter for a high frequency link uninterruptible power supply is described. The proposed inverter consists of a zero current switched series resonant convertor, a high frequency transformer and a zero current switched cycloconvertor, where bidirectional power flow and high efficiency are obtained. In the proposed inverter, the output voltage is regulated by controlling the resonant tank energy. The switching pattern of the cycloconvertor is fixed to obtain the high frequency transformer. A new control scheme to minimise the output ripple voltage is suggested and verified through computer simulation and experiment, and the effects of the circuit parameters on the output voltage ripple are discussed.

Field-oriented control of an induction machine in a high frequency link power system

A field-oriented controlled induction machine drive operating with a high-frequency single-phase sinusoidal voltage link is presented. System performance is investigated by computer simulation and is verified by test on an actual prototype system. A control loop is proposed for minimizing the link-voltage fluctuation. The capability of rapid demagnetization of the induction machine by current regulation is investigated. A new current modulation technique called switch mode selection is proposed and its performance is compared with the conventional delta modulation technique. >

Consideration on high speed AC motor drive using high frequency link power converter.

Consideration on high speed AC motor drive using high frequency link power converter.

Bilateral DC to AC convertor using a high frequency link

The paper describes a bilateral high frequency DC/AC convertor for uninterrupted power supply applications. The proposed convertor can also function as a battery charger without any additional power circuit components. Moreover, this convertor provides ohmic isolation between the DC source and the load at high switching frequencies for the forward and reverse power flow modes of operation. Consequently, the convertor exhibits high power density.

Intracranial pressure telemetry system using semicustom integrated circuits.

A new generation of implantable, telemetric transmitters for intracranial pressure (ICP) measurements have been developed. A unique technique used in packaging the silicon piezoresistive pt essure transducer provides excellent long-term stability. Pulse code modulation is used for data transmission over a radio frequency (RF) link. To minimize the component count, two semicustom, bipolar integrated circuits are used. The transmitter electronics are housed inside a 29 ×20 ×7 mm titanium package along with the pressure transducer and two lithium batteries. Even though the transmitter consumes less than 0.4 mW of power, it is turned on remotely via RF signal transduction only on demand in order to extend the lifetime of the batteries to years. The pressure input of the transmitter has a dynamic range of -100- +200 mmHg with a 0.3 mmHg resolution and a 1 mmHg accuracy. Long-term in vitro and in vivo pressure baseline stabilities of better than 1 and 2 mmHg per month, respectively, have been achieved.

Power electronics, control of the electromechanical energy conversion process and some applications

Some fundamental considerations regarding power electronics and machine electronics are discussed. The historical development of ideas in this field is examined, the applications in the field of electric traction for rail vehicles are summarised and possible future developments are outlined. A systematic approach to power electronics, based upon the control of energy flow in switching convertors, is presented. This approach takes into consideration the different possible switching functions, the modulation functions, the realisation of these switching and modulation functions, the realisation of these switching and modulation functions by practical power semiconductor switches and the different classes of forced turn-off and commutation in power electronic circuits. Subsequently the concepts of topology and structure are defined, leading to different generic topologies for singular convertors. The structure of the five different families of composite convertors are examined, and practical examples are given. The systematic approach to machine electronics presented in the paper is based on a power flow model, using the unifying concept of rotating field theory. In combination with previously defined systematics for power electronics, this enables a systematic approach to the different classes of variable speed drives, based on power flow considerations. The historical developments of some power electronic and machine electronic ideas are traced, starting at the beginning of this century. Since the introduction of power semiconductor switches, applications of the older ideas have increased exponentially in all fields, making it impossible to cover all of them. As a consequence the development of power electronics and control of machines by electronic convertors in the field of electric traction is discussed in some detail, because this represents a record of important engineering achievements in this field. In conclusion, the present state and future trends of power and machine electronics are examined. This evaluation covers the development in the field of switching devices regarding the improvement of interfacing between signal and power electronics, the decrease of switching transition times, the reduction of device losses during conduction, and device developments for decreasing energy storage devices in convertors. The development of power electronic convertors for the reduction of the number of components in the topology and the development of convertors with a high frequency link are then covered, related to the expected development of switching devices. New directions of development regarding the electronic conditioning of the electromechanical energy conversion process concerning the elimination of undesirable effects and losses are important. The implementation of these trends by utilising the improved switching characteristics of power electronic switches and the information processing capability of microprocessors is discussed. This is then extended toward control aspects, where both these characteristics enable solutions not possible hitherto. Field control of AC machines imparts control characteristics equal to, or better than, those obtainable with DC machines to the systems, while the processing capability of microprocessors allows the configuration of adaptive machine electronic systems. Finally attention is given to the interfacing of power electronic and machine electronic systems to the power supply network. If the exponential growth of the installed capacity of equipment in the future is to be handled, active compensation of the distorted currents drawn from the supply by this equipment will have to be considered seriously.