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Efficient frequency shifting and beam splitting are important for a wide range of applications, including atomic physics.sup.1,2, microwave photonics.sup.3-6, optical communication.sup.7,8 and photonic quantum computing.sup.9-14. However, realizing gigahertz-scale frequency shifts with high efficiency, low loss and tunability--in particular using a miniature and scalable device--is challenging because it requires efficient and controllable nonlinear processes. Existing approaches based on acousto-optics.sup.6,15-17, all-optical wave mixing.sup.10,13,18-22 and electro-optics.sup.23-27 are either limited to low efficiencies or frequencies, or are bulky. Furthermore, most approaches are not bi-directional, which renders them unsuitable for frequency beam splitters. Here we demonstrate electro-optic frequency shifters that are controlled using only continuous and single-tone microwaves. This is accomplished by engineering the density of states of, and coupling between, optical modes in ultralow-loss waveguides and resonators in lithium niobate nanophotonics.sup.28. Our devices, consisting of two coupled ring-resonators, provide frequency shifts as high as 28 gigahertz with an on-chip conversion efficiency of approximately 90 per cent. Importantly, the devices can be reconfigured as tunable frequency-domain beam splitters. We also demonstrate a non-blocking and efficient swap of information between two frequency channels with one of the devices. Finally, we propose and demonstrate a scheme for cascaded frequency shifting that allows shifts of 119.2 gigahertz using a 29.8 gigahertz continuous and single-tone microwave signal. Our devices could become building blocks for future high-speed and large-scale classical information processors.sup.7,29 as well as emerging frequency-domain photonic quantum computers.sup.9,11,14. Engineering of the coupling between optical modes in a lithium niobate chip enables the realization of tunable, bi-directional and low-loss electro-optic frequency shifters controlled using only continuous and single-tone microwaves., Author(s): Yaowen Hu [sup.1] [sup.2] , Mengjie Yu [sup.1] , Di Zhu [sup.1] , Neil Sinclair [sup.1] [sup.3] [sup.4] , Amirhassan Shams-Ansari [sup.1] , Linbo Shao [sup.1] , Jeffrey Holzgrafe [...]

Frequency modulation to amplitude modulation (FM-to-AM) conversion is an important issue that can prevent fusion ignition with high power lasers such as the Laser MegaJoule (LMJ). On LMJ, most of the FM-to-AM conversion is expected in the so-called frequency conversion and focusing system, which is a nonlinear system. However, we propose linear transfer functions to compensate the effect of frequency conversion on FM-to-AM conversion. We show that most of AM distortion can be reduced by practical systems: for beam intensity up to 3 GW/[cm.sup.2], the FM-to-AM conversion level can be divided by at least 2, and we almost cancel intensity modulation for intensities below 1 GW/[cm.sup.2]. OCIS codes: 060.5060, 070.2615, 140.3518, 190.2620.

The process of frequency conversion in a multilayer structure of different media with quadratic nonlinearity is investigated by using the constant-intensity approximation. The values of complex amplitudes of the fundamental radiation and the second harmonic at the outlet of each layer are the entrance values of the corresponding complex amplitudes of the next layer. Analytical expressions for second-harmonic conversion efficiency for the case of n layers are proposed. The factors restricting the efficiency of the process of frequency conversion are analyzed. In layered media, upon frequency conversion, from one layer to the next the optimum values of the phase mismatch between layers changes. The character of the process of frequency conversion of the fundamental radiation to the second harmonic depends not only on the value of the nonlinear coefficients of waves, the phase mismatch, but also on the signs of these parameters. OCIS codes: 190.2620, 190.4400.

A single beamline of the National Ignition Facility (NIF) has been operated at a wavelength of 526.5 nm (2[omega]) by frequency converting the fundamental 1053 nm (l[omega]) wavelength with an 18.2 mm thick type-I potassium dihydrogen phosphate (KDP) second-harmonic generator (SHG) crystal. Second-harmonic energies of up to 17.9 kJ were measured at the final optics focal plane with a conversion efficiency of 82%. For a similarly configured 192-beam NIF, this scales to a total 2w energy of 3.4 MJ full NIF equivalent (FNE). OCIS codes: 140.0140, 140.3070, 140.3515, 140.3530.

We report 32% efficient frequency doubling of single-frequency 1029 nm light to green light at 514.5 nm using a single-pass configuration. A congruent composition, periodically poled magnesium-doped lithium niobate (PPMgLN) crystal of 50 mm length was used to generate a second-harmonic power of 2.3 W. To our knowledge, this is the highest reported power and efficiency achieved in the second-harmonic generation of single-frequency green light in a single-pass configuration. OCIS codes: 160.3730, 190.2620, 190.4400, 230.4320.

The temporal-resolution of the frequency-domain method for the identification of the impedance locus depends on the basis frequency used in the current waveform construction, i.e., the higher basis frequency provides the better temporal resolution. The impedance locus can be characterized by the impedance parameters [Z.sub.o], [beta], and [[tau].sub.m]. The frequency distribution of limited number of data in the impedance locus would affect the accuracy of the estimated impedance parameters. Therefore, we investigated the relationship between the estimation accuracy of the impedance parameters and the frequency coverage of the impedance locus in relatively low to high impedance conditions (dc impedance [Z.sub.o] = 51 k[ohm]-45 M[ohm]). As the basis frequency, 100 Hz was enough for the usual impedance with [Z.sub.o] less than 203 k[ohm]. On the other hand, 10 Hz and 1 Hz were required for the medium-level ([Z.sub.o] = 517 k[ohm]), and high-level ([Z.sub.o] = 45 M[ohm]) impedance, respectively. The required basis frequency, accordingly the temporal resolution, depended much on the central relaxation time [[tau].sub.m] which affects the frequency distribution on the impedance locus. The results of this study are expected to serve as the reference of the frequency selection in the frequency-domain analysis of the skin impedance. Index Terms--Basis frequency, central relaxation lime, frequency-domain method, skin impedance, temporal resolution.

This brief presents the design and implementation of a 40-GHz flip-flop-based frequency divider which incorporates a novel latch topology with two distinct tail current sources and an enabled cross-coupled pair during the tracking mode. The proposed topology will speed up the latch operation and increase the driving capability. It is capable of performing frequency division at 40 GHz without shunt or series peaking inductors. The circuit was fabricated in a 0.18-[micro]m SiGe BiCMOS process, where only CMOS transistors were used. It draws an average current of 5 mA from a 1.8-V supply voltage. Index Terms--Current-mode logic (CML), frequency divider (FD), high speed, latch, wireline transceiver.

An all-MOS linear voltage-to-frequency converter (VFC) chip with 520-kHz/V sensitivity is presented in this paper. This circuit converts an input voltage into frequency by charging and discharging a capacitor. An all-MOS voltage window comparator (VWC) with reduced propagation delay is designed to improve the linearity of traditional VFCs. The propagation delay of the VWC is discussed to resolve the tradeoff between bandwidth and linearity of V-FC. The proposed VFC is verified on silicon using the Taiwan Semiconductor Manufacturing Company 1P5M 0.25-[micro]m process. The measurement results show that the linearity error is less than 1%, and the sensitivity is 520 kHz/V at an input voltage range from 0.1 to 0.8 V. Index Terms--Linearity, sensitivity, voltage window comparator (VWC), voltage-to-frequency converter (VFC).

Continous frequency shifting of a train of mode-locked pulses of light by up to plusmn 400 GHz is reported using electrooptic frequency shifting (EOFS). Dynamic, continuous, and accurate shifting of the optical pulses is achieved by controlling the phase and power of a single frequency microwave signal in a travelling wave phase modulator structure.

An optical wavelength converter is described and discussed.

This paper proposes a new topology of a frequency doubler using a dynamic-loading technique to achieve higher operating frequency, larger output swing, larger bandwidth and lower phase noise compared to traditional designs. Implemented in a standard 0.35-[micro]m digital CMOS process and at a 1.5-V supply, the proposed frequency doubler measures a maximum operating output frequency of 4 GHz with a bandwidth of 2.4 GHz while consuming a power of 3.7 mW. The single-ended output amplitude is ranging from -3.0 to -6.5 dBm, and the phase noise is as low as--111 dBc/Hz@500-kltz offset. Index Terms--CMOS frequency doubler, frequency multiplier, frequency synthesizer, frequency conversion.

Blue energy upconversion emission in Tm[superscript 3+] -doped siO[subscript 2]-P[subscript 2]O[subscript 5] channel waveguides is described and discussed.

Smart antenna is considered as one of the most effective means for enhancing wireless system capacity. When fractional loading is accompanied with slow-frequency hopping (SFH), soft capacity can be realized in time-division multiple access (TDMA) wireless networks. Then, the interference reduction due to smart antennas, power control, and discontinuous transmission can be directly translated into capacity gain. This paper addresses the capacity gain due to multiple-beam (MB) smart antennas in TDMA wireless systems with soft capacity. The system capacity is determined analytically and by simulation. MB smart antennas with practical antenna pattern are used in this study. Perfect power control and discontinuous transmission are assumed in the simulation and the theoretical analysis. A novel call admission control algorithm is proposed to enhance the system capacity without degrading the signal quality. The TDMA system is assumed to be global system for mobile communications (GSM)-like, however, the analysis can be extended and applied to other TDMA systems. Index Terms--Call admission control, performance analysis of wireless systems, slow-frequency hopping (SFH), smart antennas, soft capacity, wireless network simulation.

Steady-state analysis of soft-switching converters is discussed in this paper. Finding the steady-state solution of soft-switching converters by means of start-up transient simulation may involve onerous computations and convergence failure, because of the mix of fast and slow natural frequencies determined respectively by the presence of soft-switching Lr-Cr cells elements and bulky L-C filter elements. The numerical method proposed in this paper shows high reliability and fast convergence, thanks to the adoption of an interval analysis based technique for the detection of commutations and of a compensation theorem based technique for the analysis of commutations. Some examples of steady-state analysis of two dc-dc converters, an inverter and a power factor corrector are presented to highlight the good performances of the simulation algorithm. Index Terms--Compensation theorem, interval analysis, soft-switching converters, steady-state analysis.

An analysis is proposed for second-harmonic generation (SHG) in nonlinear dielectric media. Both second- and third-order nonlinear interactions are taken into consideration.

Techniques of varying electron density of the picosecond laser-produced plasma are discussed, with focus on investigating efficiency levels in generating fifth-order harmonic from plasma at a solid's surface. Several harmonic levels are analysed.

A study has been conducted to investigate the possibility of forming quadratic solitons in new settings, unexplored wavelength bands, and novel materials where the different waves forming the solitons experience significant absorption losses or linear gain depending on the wavelength band to which they belong. It has been found that the action of linear absorption and gain can reshape these signals. New chirped solitary-wave solutions were found to theoretically allow exact compensation.

Research was conducted to examine the tunable 50-fs pulse generation in the 250-310-nm ultraviolet range. The optical parametric amplifier visible pulses and corresponding second harmonic ultraviolet outputs pumped by a new high-repetition-rate ultrafast regenerative amplifier that is designed to produce transform limited sub-50-fs pulses at 100-300-kHz repetition rates is described. The system could be further optimized for the production of even shorter pulses at these ultraviolet wavelengths.

This paper deals with the design considerations, fabrication process, and performance of coplanar waveguide (CPW) heterojunction FET (HJFET) down- and up-converter monolithic microwave integrated circuits (MMIC's) for V-band wireless system applications. To realize a mixer featuring a simple structure with inherently isolated ports, and yet permitting independent port matching and low local oscillator (LO) power operation, a 'source-injection' concept is utilized by treating the HJFET as a three-port device in which the LO signal is injected through the source terminal, the RF (or IF) signal through the gate terminal, and the IF (or RF) signal is extracted from the drain terminal. The down-converter chip incorporates an image-rejection filter and a source-injection mixer. The up-converter chip incorporates a source-injection mixer and an output RF filter. With an LO power and frequency of 7 dBm and 60.4 GHz, both converters can operate at any IF frequency within 0.5-2 GHz, with a corresponding conversion gain within -7 to -12 dB, primarily dominated by the related filter's insertion loss. Chip size is 3.3 mmx2 mm for the down-converter, and 3.5 mm x 1.8 mm for the up-converter.

Coupled-wave equation numerical analysis was employed in examining uniform and lambda/quarter-wave-shifted distributed feedback lasers exhibiting highly nondegenerate four-wave mixing. Carrier heating, longitudinally variable pump fields, carrier spatial and spectral hole burning were found to affect mixing. Conjugate waves may be produced in 1 THz bandwidth with 20 db or more efficiency for small and moderate distributed feedback coupling coefficients.

A buck converter operating at constant switching frequency, whose active switches and recovery diode commutate at zero-voltage-switching (ZVS), with zero capacitive turn-on losses, is proposed. By using the parasitic capacitances of the switches as resonant capacitors, multiresonance is created. The resonant stage takes place only after the resonant inductor has been discharged, thus avoiding a resonant current peak; the devices are subjected to the same stresses as their counterparts in conventional hard-switching converters. A high efficiency is obtained.

This paper presents an analysis and experimental results for a frequency-controlled series-resonant dc-dc converter that consists of a Class-D zero-voltage-switching (ZVS) series-resonant inverter and a center-tapped synchronous rectifier. If the dc output voltage is low, the efficiency of the converter is dominated by the efficiency of the rectifier. Low on-resistance metal-oxide-semiconductor field-effect transistors (MOSFETs) are used in the rectifier instead of diodes because the forward voltage drop across the rectifying device is low, resulting in a high efficiency. The dc output voltage is regulated against variations in the load resistance and the dc input voltage by varying the operating frequency. Experimental results are presented for a converter with a dc input voltage of 150 V, an output voltage of 5 V, and a dc load resistance ranging from 0.5 to 5.5 [ohms]. The measured efficiency was 86% for a 50 W output and 89% for a 25 W output. The theoretical results were in good agreement with the measured results.

The problem of extracting multiple frequencies from phase-only data is addressed. Multiple frequency estimation is accomplished by reconstructing the Fourier transform of the complex-valued time signal and then finding peaks in the frequency domain. We present a set of conditions under which a discrete-time complex sequence can be completely specified by its phase-only information. Two candidate multiple frequency estimation schemes are introduced, one based on a closed-form least-squares inverse, the other an iterative reconstruction algorithm. The uniqueness of the closed-form solution and the convergence of the iterative scheme have been proven under certain conditions. Several examples are given, including the case where the phase is quantized as would happen in an analog-to-digital (A/D) converter. Extensions to the multidimensional case, and to the case of real-part only reconstruction are straightforward.

A time-to-digital converter was designed, fabricated and tested. The converter circuit features superconductive counters based on toggle flip-flops with destructive readout, pulse detectors, parallel-to-serial converters and shift registers. HYPRES' library of standard RSFQ cells was used for the implementation of the circuits in HYPRES' standard Nb process with a 1.0 kA/cm2 critical current density.

Interface circuits were developed for chip-to-chip data transfer between single flux quantum circuits at GHz rates. The circuit, which were operated at speeds of up to 3 Gigabits per second, used an enhanced version of the SFQ/Latch converter, a 3X-to-10X latching amplifier and modified variable threshold logic or/and gate. The distribution of the applied current to latching elements was ensured by microwave modeling programs.

Prototype planar four barrier GaAs/[Al.sub.0.7] [Ga.sub.0.3] As heterostructure barrier varactors (HBV's) for frequency tripling from 80 to 240 GHz have been fabricated using a process in which the device surface channnel is etched prior to the formation of the contact pad-to-anode air-bridge finger. Formation of the device air-bridge finger after etching the surface channel is facilitated by a trench planarization technique and yields a device with minimal parasitic capacitances. Planar four-barrier HBV triplets with nominal 10-[[micro]meter] diameter anodes have been tested in a crossed-waveguide tripler block; as much as 2 mW of power has been generated at 252 GHz with a flange-to-flange tripling efficiency of 2.5%. These devices are the first planar or multibarrier HBV triplets reported and their output powers are nearly double that of previous whisker-contacted single-barrier HBV's. Index Terms - Frequency conversion, millimeter-wave diodes, semiconductor heterojunctions, varactors.

By pumping a single-mode optical fiber with a powerful broadband nonselective dye laser, we obtain a high-efficiency wideband continuum (530-930 nm) with nonlinear conversion efficiency exceeding 90%. Experimental conditions for a coherent regime of broadband stimulated Raman scattering are created, which in combination with the broadband self-phase modulation and the four-photon parametric processes leads to a spectral broadening and to the continuum formation. The influence of the pump laser spectral linewidth on the nonlinear conversion efficiency is analyzed and investigated by comparative experiments at narrow-band and broadband laser excitations. Key words: Nonlinear frequency conversion, single-mode fiber, broadband laser pumping.

This paper shows that by transforming both sides of the matrix converter to the d-q-o frames of their respective frequencies, there is significant simplification in the transformation matrix which enables the network of one side to be integrated to the other. Thus, it is possible to design for operation with field vector control on the motor side and unity displacement factor on the supply side. Laboratory experimental and digital simulation results are presented to substantiate the theory. The matrix converter used in the test is based on three modules of voltage-source SPWM converters to implement the nine switches and it has the innovative feature that the SVC voltages (for displacement factor improvement) can be derived from the zero-sequence voltages.

A new heterostructure device is developed using Heterostructure Barrier Varactors (HBVs), which are more accurate, fast, with temperature-dependent DC and large signal time-dependent electron transport properties. The model combines thermionic and thermionic-field emission currents put at abrupt heterointerfaces with drift-diffusion current movement in a heterostructure device. The model's working and the results are discussed.

Accurate and efficient simulations of the large-signal time-dependent characteristics of second-harmonic Transferred Electron Oscillators (TEO's) and Heterostructure Barrier Varactor (HBV) frequency triplers have been obtained. This is accomplished by using a novel and efficient harmonic-balance circuit analysis technique which facilitates the integration of physics-based hydrodynamic device simulators. The integrated hydrodynamic device/harmonic-balance circuit simulators allow TEO and HBV circuits to be co-designed from both a device and a circuit point of view. Comparisons have been made with published experimental data for both TEO's and HBV's. For TEO's, excellent correlation has been obtained at 140 GHz and 188 GHz in second-harmonic operation. Excellent correlation has also been obtained for HBV frequency triplers operating near 200 GHz. For HBV's, both a lumped quasi-static equivalent circuit model and the hydrodynamic device simulator have been linked to the harmonic-balance circuit simulator. This comparison illustrates the importance of representing active devices with physics-based numerical device models rather than analytical device models.

Analysis of a planar diode multiplier from 85-170 GHz is described. The doubler uses a waveguide mount with two series pairs of diodes in a balanced structure. Because of the difficulties in conventional scale model measurements, numerical electromagnetic simulation based on the finite element method was chosen for the analysis, using a commercial program. To optimize the diode design, the de-embedded diode terminal impedance was studied, as well as the power balance between the diodes. The analysis showed that the matching of the diode impedance to that of the waveguide is quite sensitive to the diode substrate thickness. Thicknesses from 25-100 [[micro]meter] in GaAs were studied as well as 100-[[micro]meter]-thick quartz. The accuracy of the theoretical analysis was verified by careful measurements using a slotted line to determine the diode terminal impedance under large signal pump, for frequencies between 80 and 90 GHz. Good agreement between the measured and simulated diode terminal impedance was observed, although full agreement requires the addition of an empirical loss term. Several options are considered for the source of this loss.

The back-to-back barrier-N-[N.sup.+] (bbBNN) varactor is a nonlinear device being developed for frequency multiplier applications above 100 GHz. Its symmetrical C-V characteristic, low series resistance, freedom from external bias and suitability to planarization make it an ideal choice for high frequency, low power, odd harmonic generation. In this paper, the performance of a 220-GHz waveguide tripler using, for the first time, a planar GaAs bbBNN device integrated on a quartz microstrip circuit is presented. A new split-waveguide block design has been employed to provide the proper embedding impedances to the device at the input and third harmonic output frequencies. A flange-to-flange tripling efficiency of 7% has been obtained at 220 GHz with an output power in excess of 700 [micron]W. This is believed to be the highest conversion efficiency yet reported for a tripler with an integrated device at this frequency. Theoretical calculations indicate that substantial improvement is possible with modest changes to the device and circuit parameters.

Schottky varactor frequency multipliers are used to generate local oscillator power at millimeter and submillimeter wavelengths. The equivalent circuit of the Schottky varactor contains a junction capacitance, a junction conductance, a series resistance and a model for electron velocity saturation. At millimeter wavelengths the equivalent circuit is affected by the edge effects, which are due to the small-area circular anode. The correction factors due to the edge effect for the junction capacitance and for the series resistance are available in the literature. In this work the electron velocity saturation is modeled by limiting the velocity of the transition front between the depleted and undepleted layer. By using this model the maximum current of the diode is given by the actual area of the transition front between depleted and undepleted layers, and is therefore related to the capacitance correction factor. The new model has been tested by analyzing a two diode balanced doubler for 160 GHz presented earlier in the literature. The agreement between the theoretical results and the measurements is excellent. The new diode model is useful in optimization of varactors for high millimeter and submillimeter wave frequencies.

InGaAs/InAlAs single-barrier varactor (SBV) diodes are tested as frequency quintuplers. The diodes were tested in a crossed-waveguide structure and provided output frequencies between 148 and 187 GHz. The highest observed flange-to-flange efficiency was 0.78% at an output frequency of 172 GHz. This is nearly four times greater than the best quintupler efficiency obtained for previous SBV varactors made from the GaAs/AlGaAs materials system.

This paper describes the performance of planar back-to-back Barrier-N-N+ (bbBNN) devices for frequency multiplier applications. A tripling efficiency of 3.3% has been achieved using these devices in a 200 GHz crossed waveguide mount. This is the first experimental result with a bbBNN waveguide frequency multiplier. A technique has been developed for characterizing planar bbBNN devices with a network analyzer, which gives both the series resistance and voltage dependent capacitance of the device. The experimental results are compared with the theoretical multiplier performance, calculated using a large signal analysis approach.

Here a large deflection angle, low optical frequency-shift acousto-optic device is presented. This is realized by two successive acousto-optic interactions in the same cell. The relevant parameters of operation are analyzed in detail. A practical case with paratellurite material is then considered. Results from numerical computations leading to practical design parameters are given and compared with experimental ones.

Monolithic approaches of the development to V-band frequency converters have the advantages of lighter weight and lower cost over conventional hybrid approaches for high volume insertions into satellite communication systems. This paper presents the design, fabrication, and performance of a monolithic V-band frequency converter chip set using 0.2 micrometer AlGaAs/InGaAs/GaAs pseudomorphic HEMT technology. This chip set consists of three monolithic macrocells and a microcell: an upconverter, a downconverter, and a frequency multiplier for LO signal. A monolithic balanced amplifier microcell is also used to form the LO chain. Individual components, including amplifiers, mixer, and frequency doublers are also described. The superb measured results obtained from this chip set show great promise of the MMIC insertions for the system applications, and represent state-of-the-art performance of MMIC at this frequency.

The small-signal analysis of an injection-locked semiconductor laser frequency conversion efficiency for a highly nondegenerate four-wave mixing reveals that cavity resonance increases the converted signal output. The similarity between converted signal frequency and the resonant mode is subjected to the nonlinear gain effect with resultant frequency conversion. The frequency conversion is not symmetrical with gain peak and the mode of converted signal appearance.

A new torque control method is described that is suitable for general-purpose induction motor variable speed drives driven by superaudible frequency PWM inverters. The primary magnetic flux reference is compensated, using only current sensors, on the basis of the inverter angular frequency and the slip angular frequency so that motor torque can be generated according to load torque. The superaudible frequency PWM signals are generated by divisions of duration times of the voltage vectors, determined on the basis of the primary magnetic flux reference. Experiments showed that high-performance torque characteristics suitable for general purpose inverters could be obtained by this method.

The conversion gain and noise power of YBa2Cu3O7 microbridge mixers were studied. Several experimental mixers, fabricated by radio frequency sputtering, were subjected to an 18.5 gigahertz wave and a 20 gigahertz wave which serve as the low ouput and radio frequency signals, respectively. The conversion gain and noise power of the devices were then measured at different temperatures. Results show that the mixers have relatively low conversion gain and their noise powers were found to be comparable in magnitude to the white noise levels measured in deliberate gain boundary links.

In this paper, the small signal analysis of the conventional parallel resonant converter (PRC) operating in the continuous conduction mode will be given. This analysis is based on the state-plane approach that has been successfully used to obtain the steady-state response for resonant converters. Applying perturbation directly to the steady-state trajectory, a discrete small signal model for the converter can be derived in terms of the input voltage, switching frequency, and the converter state variables. Furthermore, it can be shown that this method can be applied to resonant converters in general, regardless of the order of their resonant tanks. Based on the derived closed-form solution, frequency responses of two transfer functions will be obtained: input-to-output and control-to-output transfer functions. Finally, computer simulation and experimental results will be reported.

An experiment conducted at the Philips Laboratory on extracavity frequency doubling is reported. It employed the 1315-nm beam of a chemical oxygen-iodine laser with lithium iodate crystals of length 1.1 and 2.2 cm as the doubling medium for irradiation. Results show the generation of visible 686-W continuous wave laser power for a beam size of 657 nm although an analytical study of data obtained indicates the possibility of attaining higher outputs.

Synchronous front-end PWM rectifiers are compatible with variable-frequency inverters because they generate a near sinusoidal input current with a controllable power factor and allow for the instantaneous reversal of power flow. Of the numerous publications in this area, however, none has dealt with the problems caused by input line voltage unbalance. As this paper shows, such problems include a significant distortion in the input current waveforms, considerable increase in the dc capacitor ripple current and voltage, and more importantly, the generation of subharmonic components in the inverter output voltages. The objective of this paper is to analyze the effects of input line voltage unbalance starting with the distortion in the input line currents and extending to the dc bus components and inverter output line voltages and currents. Analytical results are next used to obtain system design curves as a function of input voltage unbalance for all major system components. Finally, key predicted results are verified on a 2-kVA prototype unit.

A very small, ultra-wideband MMIC balanced frequency doubler, which employs line-unified HEMT configurations, is proposed. A chip size of 1.0 mm x 0.9 mm is achieved with a conversion loss of 8-10 dB in the 4-40 GHz output harmonics frequency range and fundamental frequency signal isolation of better than 21 dB above the input fundamental frequency of 7 GHz. Circuit parameters are optimized in a novel and simple prediction using an equation derived from HEMT's dc characteristic and a linear-state CAD software package. The doubler promises to realize miniaturized, wideband MMIC transmitters/receivers.

A study on the limitations of the barrier-intrinsic-n+ (BIN) diode frequency tripler and the problems faced in its use reveals the GaAs semiconductor mean drift velocity applied in the device as over-rated. Results show the BIN diode frequency tripler's poor performance in high-frequency generation due to the large resistance-capacitance circuit and the minimal capacitance-voltage variation of the BIN structure which uses a back-to-back configuration. Further, the high electric field distribution in the structure does not allow optimization in performance.