In this paper, a predistorter using low frequency intermodulation (IM) signals is proposed. The harmonic generator of the proposed predistorter that consists of a hybrid coupler and four diodes biased separately extracts a second order low frequency IM signal. And with multiplication of second order IM signals, fourth order IM signal is obtained. A vector modulator, modulate fundamental signal with low frequency IM signals, generates predistortion IM signals and controls amplitude/phase of them with modulation factors. As a result, this predistorter is suppressed individual order intermodulation distortion signals of power amplifier effectively. The suggested predistorter has been manufactured to operate in Korea PCS base-station transmitting band (1840-1870 MHz). The test results show that the third order IM is cancelled more than 20 dB and the fifth order IM is cancelled about 10 dB for CW two-tone signals. Also, it's improved the adjacent channel power ratio (ACPR) more than 10 dB for CDMA (IS-95) signals.

In the problem of determining the major frequency components of a signal disturbed by noise, a model selection criterion has been proposed. In this paper, the criterion has been extended to cover a penalized cost function that yields a componentwise shrinkage estimator, and it exhibited a consistent model selection when the proposed criterion was used. Then, a simple numerical simulation was conducted, and it was found that the proposed criterion with an empirically estimated componentwise shrinkage estimator outperforms the original criterion.

A novel signal processing technique using adaptive neural network algorithm is applied for the on-line detection of harmonic current components generated by nonlinear current loads in the single-phase diode bridge rectifier and it can efficiently determine the harmonic current components in real time. The validity of this active filtering processing system to compensate current harmonics is proved on the basis of simulation results.

Higher-order harmonics and distortions generated by nonlinearity of capacitance-voltage characteristic of a single varactor and an anti-series-connected varactor pair are analyzed and compared. The effect of linear and parabolic terms of nonlinearity to harmonics outputs and distortions is discussed. It is shown that an anti-series-connected varactor pair has a completely suppressed linear term and reduced parabolic term. The advantage of an anti-series-connected varactor pair is theoretically explained.

Harmonic distortions of a recently developed lightweight film-type ESPAR (Electronically Steerable Passive Array Radiator) antenna are investigated experimentally. These distortions arise from the nonlinearity of the varactor diodes that are directly integrated with the parasitic radiator elements to control the antenna's radiation pattern. A reactive-near-field measurement technique that employs low-interference probes in an ultra-small anechoic box is used to reduce experimental time and cost. An anti-series varactor pair is introduced and compared with the conventional single varactor. Consequently, an ESPAR antenna equipped with the anti-series varactor pair exhibits remarkable suppression of nonlinear distortion. In particular, the second- and the third-order harmonic is reduced by approximately 20 dB and 12 dB from the level of a single varactor type ESPAR antenna, respectively.

A novel delta-sigma modulator that utilizes a resonant-tunneling diode (RTD) quantizer is proposed and its operation is investigated by HSPICE simulations. In order to eliminate the signal-to-noise-and-distortion ratio (SINAD) degradation caused from the poor isolation of a single-stage quantizer (1SQ), a three-stage quantizer (3SQ), which consists of three cascoded RTD quantizers, is introduced. At a sample rate of 10 Gsps (samples per a second) and a signal bandwidth of 40 MHz (oversampling ratio of 128), the modulator demonstrates a SINAD of 56 dB, which corresponds to the effective number of bits of 9.3.

Two novel linearization processes in electro-absorption-modulator (EAM) are proposed and demonstrated. These two modulation schemes are used to compensate the nonlinear component of the EAM by controlling the DC bias voltages of the each EAM separately. The simulations on the nonlinearity of EAM and linearization process are performed in both time and frequency domains. From a serially cascaded modulation simulation, a reduction of 16 dB in IMD3, 45 dB in IMD5 and the following increase of 15 dB in linear dynamic rage (LDR) are achieved. In dual-parallel modulation experiment at 8 GHz, a reduction of 23 dB in IMD3 and the following increase of 15.1 dB in LDR of are achieved compared to those of a single EAM operation.

We present measurements of kilohertz and megahertz sine waves synthesized using a Josephson arbitrary waveform synthesizer. A 4.8 kHz sine wave synthesized using an ac-coupled bias technique is shown to have a stable 121 mV peak voltage and harmonic distortion 101 dB below the fundamental (-101 dBc (carrier)). We also present results of our first phase-noise measurement. A 5.0 MHz sine wave was found to have distortion 33 dB lower than the same signal synthesized using a semiconductor digital code generator. The white-noise floor of the Josephson synthesized signal is -132 dBc/Hz and is limited by the noise floor of the preamplifier.

A multiphase low-jitter delay-locked loop (DLL) with harmonic-lock prevention, targeted at a gigabit parallel link interface, is delineated. A three-input four-state dynamic phase detector (PD) is proposed to obviate harmonic locking. Employing a low-jitter delay element and a new type of PD, the DLL is compact and feasible in its nature. The DLL is designed using a 0.35 µm 2P4M CMOS process with 3.3 V supply. Experimental results show that the circuit avoids false locking.

This paper describes how the symmetry of a three-phase circuit prevents the symmetric modes of several subharmonic oscillations. First, we make mathematically it clear that the generation of symmetrical 1/3l-subharmonic oscillations (l=1,2,) are impossible in the three-phase circuit. As far as 1/(3l+1)-subharmonic oscillations (l=1,2,) and 1/(3l+2)-subharmonic oscillations (l=0,1,) are concerned, the former in negative-phase sequence and the latter in positive-phase sequence are shown to be impossible. Further, in order to confirm the above results, we apply the method of interval analysis to the circuit equations and obtain all steady state solutions with unsymmetric modes.

A K-band MMIC subharmonically pumped mixer integrating local oscillator (LO) amplifier has been developed. For up-converter application, it is necessary to reduce the leakage of second harmonic component of LO frequency to RF port, which is generated by nonlinear operation of LO amplifier. A quasi-lumped short-circuited stub using microstrip structure has been successfully applied to the MMIC mixer to enhance 2fLO-suppression. We propose a new configuration of a quasi-lumped short-circuited stub, which reduces the influence of parasitic elements of via-holes. The developed MMIC has a one-stage LO amplifier and it has shown about 10 dB-improvement of 2fLO-suppression compared to conventional configuration using a quarter-wavelength short-circuited stub.

Generally, a siren of ambulance is used to let drivers know that an ambulance is approaching. Although the siren system is effective to alert the drivers and pedestrians, the sound of siren is noisy in a cabin of ambulance. In this paper, an active noise control (ANC) system to control the sound of siren using headset is proposed. The proposed ANC system selectively controls only the sound of siren, and other sound such as speech is not affected at all. The achieved attenuation level by the proposed ANC system is more than 20 dB.

A first-order investigation of the transport and energy-loss processes in silicon dioxide is worked out in the frame of the Spherical-Harmonics solution of the Boltzmann Transport Equation. The SiO2 conduction band is treated as a single-valley spherical and parabolic band. The relevant scattering mechanisms are modeled consistently: both the polar and nonpolar electron-phonon scattering mechanisms are considered. The scattering rates for each contribution are analyzed in comparison with Monte Carlo data. A number of macroscopic transport properties of electrons in SiO2 are worked out in the steady-state regime for a homogeneous bulk structure. The investigation shows a good agreement in comparison with experiments in the low-field regime and for different temperatures.

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr substrate by molecular beam epitaxy (MBE). Their maximum size is 1380.16 µm3. The morphology of the VOPc single crystal was investigated from the results of UV/VIS spectra and RHEED. They suggest that the VOPc single crystal may be grown with pseudomorphic layers. The growing process was expained by Volmer-Weber model. The third order nonlinear optical property of VOPc single crystal was measured with Maker fringe method. The value of the third order optical susceptibility (χ(3)) of VOPc single crystal was estimated to be about 10-9 esu from the result of Maker fringe.

The cationic dye, E-N-alkyl-4-[2-(4-alkyloxynaphthyl) ethenyl] quinolinium bromide has a wide-bodied chromophore with alkyl groups at opposite ends, i. e. CmH2m+1-D-π-A+-CnH2n+1 X-, where D and A are electron-donor and electron-acceptor groups respectively, π is a conjugated bridge and X- is the bromide counterion. It forms non-centrosymmetric Langmuir-Blodgett (LB) structures in which the packing is dependent upon the combination and compatibility of the alkyl groups. Films of two isomeric analogues where m + n = 34, have a layer thickness of 4.3 nm when the groups are significantly different (m = 12 and n = 22) which decreases to 2.5 nm when they are similar (m = 18 and n = 16). The latter adopts an interdigitating layer arrangement at both the upper and lower interfaces and it is the first example of a Lego-type structure with non-centrosymmetric alignment of the optically nonlinear chromophores. This is evidenced by the second-harmonic intensity, which increases quadratically with the number of layers, i. e. as .

We present two estimation methods for camera rotation from two images obtained by the active camera before and after rotation. Based on the representation of the projected rotation group, quasi moment features are constructed. Camera rotation can be estimated by applying the singular value decomposition (SVD) or Newton's method to tensor quasi moment features. In both cases, we can estimate 3D rotation of the active camera from only two projected images. We also give some experiments for the estimation of the actual active camera rotation to show the effectiveness of these methods.

A three-dimensional beam propagation method based on a finite element scheme is described for the analysis of second harmonic generation devices. For the wide-angle beam propagation analysis, the Pade approximation is applied to the differential operator along the propagation direction. In order to avoid spurious reflection from the computational windows edges, the transparent boundary condition is introduced. Numerical results are shown for quasi-phase matched second harmonic generation devices using periodically domain-inverted LiNbO3 and LiTaO3 waveguides. The influences of the shape of domain-inverted regions and the inversion width on the conversion efficiencies are investigated in detail.

This paper presents the several bifurcation phenomena generated in nonlinear three-phase circuit with symmetry. The circuit consists of delta-connected nonlinear inductors, capacitors and three-phase symmetrical voltage sources. Particular attention is paid to the subharmonic oscillations of order 1/2. We analyze the bifurcations of the oscillations from both theoretical and experimental points. As a tool of analysis, we use the homotopy method. Additionally, by comparing with single-phase and single-phase-like circuits, the special feature of the three-phase circuit is revealed.

In this paper, we study a new hybrid speech coder which employs a modified version of the harmonic sinusoidal analysis to encode the periodic contents of speech waveform and to split the speech spectrum into two frequency regions of harmonic and random components. A reliable fundamental frequency is estimated for the harmonic region using both speech and its linear predictive (LP) residual spectrum. The peak envelope of speech spectrum is encoded in terms of the coefficients of an all-pole spectrum. A harmonic tracking algorithm appropriately interpolates the sinusoidal parameters to achieve a smooth transition between the parameter update points and to reconstruct an essential level of periodicity in the synthetic voiced speech. The random part of spectrum and unvoiced speech are coded using the conventional CELP algorithm. The individual components are then combined at the decoder to obtain the synthetic speech. The proposed hybrid coder which combines the powerful features of the sinusoidal and CELP coding algorithms yeilds a high quality synthetic speech at 4.05 kbps.

As wireless communication is penetrating every corner of the globe, the optimum design and accurate analysis of RF, power semiconductor devices become one of the biggest challenges in EDA and TCAD (Technology CAD) tool development. The performance gauge for these devices is quite different from that for either digital or analog devices aimed at small-signal applications in that the power gain, efficiency, and distortion (or the range of linearity) are the utmost design concerns. In this article, the methodology and mathematical foundation for numerical analysis of large signal distortion at the device simulation level are discussed. Although the harmonic balance (HB) method has long been used in circuit simulation for large signal distortion analysis, the implementation of the same method in device simulation faces daunting challenges, among which are the tremendous computational cost and memory storage management. But the benefits from conducting such a device level simulation are also obvious--for the first time, the impact of technology and structural variation of device on large signal performance can directly be assessed. The necessary steps to make the HB analysis feasible in device simulation are outlined and algorithmic improvement to ease the computation/storage burden is discussed. The applications of the device simulator for various RF power devices, including GaAs MESFETs and silicon LDMOS (lateral diffusion MOS) are presented, and the insight gained from such an analysis is provided.