This paper proposes a new AFC (automatic frequency control) circuit employing a double-product type frequency discriminator to enable fast acquisition in very-low CNR (carrier to noise power ratio) environments. The frequency step responses of the proposed AFC circuit are theoretically analyzed. In addition this paper evaluates the performance of the proposed AFC circuit by computer simulation in very-low CNR environments. The simulation results confirm that click noise at the frequency discriminator causes large frequency tracking error and that this error can be improved by increasing the delay time of the double-product type frequency discriminator. The frequency error can be also reduced by introducing the proposed frequency discriminator to modify the frequency error detection performance. The acquisition time of the proposed AFC circuit can be reduced by about 100 symbols compared to the conventional cross-product type AFC circuit.

Discussed here is reduction of power dissipation for multi-media LSIs. First, both active power dissipation Pat and stand-by power dissipation Pst for both CMOS LSIs and GaAs LSIs are summarized. Then, general technologies for reducing Pat are discussed. Also reviewed are a wide variety of approaches (i.e., parallel and pipeline schemes, Chen's fast DCT algorithms, hierarchical search scheme for motion vectors, etc.) for reduction of Pat. The last part of the paper focuses on reduction of Pst. Reducing both Pat and Pst requires that both throughput and active chip areas be either maintained or improved.

A very simple but general scheme has been developed to calculate burst error occurrences due to cycle slip in clock recovery on frequency-selective Nakagami-Rice fading channels. The scheme, which we call the "Equivalent Transmission-Path Model," plays a role in connecting "wave propagation" with "digital transmission characteristics" in a general manner. First computer simulations assuming various types of delay profiles identify the "key parameters in Nakagami-Rice fading" that principally dominate the occurrence of cycle slips. Following this a simple method is developed to calculate the occurrence frequency of cycle slips utilizing the nature of the key parameters. Then, the accuracy of the scheme is confirmed through comparison between calculated values and simulation results. Finally, based on the scheme, calculated results on cycleslip occurrences are presented in line-of-sight fading environments.

In this contribution an algorithm for joint detection in fast frequency hopping/multiple frequency shift keying (FFH/MFSK) multiple access (MA) systems is presented. The new algorithm - referred to as REC algorithm - evaluates ambiguities which occur during the decision process and iteratively reduces the number of candidate symbols. The REC algorithm is of low complexity, suitable for every addressing scheme, and effective for both an interference-only channel and a fading channel. For the interference-only channel the REC algorithm enables maximum likelihood (ML) joint detection with low computational effort.

This paper reports on a high-speed silicon bipolar transistor with an fT and fMAX of over 40 GHz, we call it the Advanced Boro-silicated-glass Self-Aligned (A-BSA) transistor. In basic BSA technology, a CVD-BSG film is used not only as a diffusion source to form the intrinsic base and the link base regions but also as a sidewall spacer between the emitter and the base polysilicon electrodes. An A-BSA transistor offers three advancements to this technology: (1) a graded collector profile underneath the intrinsic base region to suppress the Kirk effect; (2) an optimized design of the link base region to prevent the frade-off effect between fT and base resistance; and (3) a newly developed buried emitter electrode structure, consisting of an N++-polysilicon layer, a platinum silicide layer, and a CVD tungsten plug, to prevent the emitter plug effect. Furthermore, our transistor uses a BPSG filled trench isolation to reduce parasitic capacitance and improve circuit performance. In this paper, we describe device design, process technology and characterization of the A-BSA transistor, with it we have performed several application ICs, operating at 10Gb/s and above. The A-BSA transistor achieved an fT of 41 GHz and an fMAX of 44 GHz under optimized conditions.

A slotted waveguide planar array using a single-layer feed circuit is applied to high frequency and high gain use. The remarkable efficiency of 75.6% is realized for the gain of 35.9 dBi in 22 GHz band and 64% is realized for 35.1 dBi in 60 GHz band. Each antenna consists of only two components; a slotted plate and a groove base plate, and are highly mass produceable.

This paper proposes a novel Doppler frequency shift compensation technique to achieve terrestrial and low earth orbit (LEO) satellite dual mode DS/CDMA terminals robust to high Doppler shift and multipath fading. In order to satisfy the requirements of wide dynamic range and high accuracy simultaneously, the proposed scheme employs two stage compensation scheme, i.e., coarse compensation to keep dynamic range of about 100 kHz and fine compensation to satisfy its resolution of about 30 Hz, using block demodulation technique. Computer simulation results show that the proposed scheme can sufficiently compensate for the offset frequency up to the range of about 100 kHz at the terrestrial and LEO satellite combined mobile communication systems.

A three-terminal quantum device utilizing photon-assisted tunneling in a multilayer structure is proposed and analyzed in terms of its high frequency amplification characteristics. The operation principle of this device includes photonassisted tunneling at the input, formation of a propagating charge wave due to the beat of tunneling electrons and its acceleration, and radiation of electromagnetic waves at the output. Analysis of these operations, discussion of similarities and dissimilarities to classical klystrons, and estimation of the power gain and its frequency dependence are given. A simple example demonstrates that amplification up to the terahertz frequency range is possible using this device.

A high-frequency approximate method for calculating the diffraction by a smooth convex surface is presented. The advantage of this method is the validity of it in the caustic region of the creeping rays where the Geometrical Theory of Diffraction (GTD) becomes invalid. The concept used in this method is based on the Method of Equivalent Edge Currents (EEC), and the equivalent line currents for creeping rays which are derived from the diffraction coefficients of the GTD are used. By evaluating the radiation integral of these equivalent line currents, the creeping ray contribution which is valid within the caustic region is obtained. In order to check the accuracy and the validity of the method, the diffraction problem by a perfectly conducting sphere of radius a is solved by applying the method, and the obtained results are compared with the exact and the GTD solutions. It is confirmed from the comparison that the failure of the GTD near the caustic is removed in this method and accurate solution is obtained in this area for high-frequency (ka8). Furthermore, it is also found that this method is valid in the backward region (0θ90, θ is an observation angle mesuered from an incident direction), whereas not in the forward region (90θ180).

This paper presents a new Frequency Shift Keying (FSK) demodulation method using the Short Time-Discrete Fourier Transform (ST-DFT) analysis to combat large frequency offset with time variation in low earth orbit (LEO) satellite communications systems. This demodulation method can demodulate the received signal only by searching for the instantaneous spectrum energy peaks without complicated carrier recovery. In addition, it is insensitive to the signal-to-noise ratio (SNR) degradation caused by the excessively wide bandwidth of the receiver front-end band pass filter. Furthermore, the ST-DFT analysis combined with a differential encoding scheme gives FSK demodulation method a potential robustness against large and fast time-varying frequency offset.

The performance of an M-ary spread-spectrum multiple-access (M-ary/SSMA) scheme in the presence of carrier frequency offset is discussed in this paper. The influence of carrier frequency offset on the non-coherent reception of M-ary/SSMA signals is examined and it is shown that the carrier frequency offset degrades the performance remarkably, yet. this influence has a distinctive property. Making use of this property, we propose a new M-ary/SSMA scheme that can mitigate the influence of the carrier frequency offset. The scheme is based on the assignment of two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The effect of simultaneous transmission is evaluated in terms of bit-error-rate performance with the carrier frequency offset. As the result, it is observed that the satisfactory bit-error-rate performance can be achieved in the presence of carrier frequendy offset.

M-ary orthogonal keying (MOK) systems under carrier frequency offset (CFO) are investigated. It is shown that spurious signals are introduced by the offset frequency components of spectrum after multiplication in correlation detection process, and some conditions on robust orthogonal signal sets are derived. Walsh function sets are found to be very weak against CFO, since they produce large spurious signals. As robust orthogonal signal sets against CFO, the rows of circulant Hadamard matrices are proposed and their error performanses are evaluated. The results show that they are good M-ary orthogonal signal sets in the presence of CFO.

There are many kinds of transmission lines such as uniform, nonuniform and nonlinear ones terminated by linear and/or nonlinear subnetworks. The nonuniform transmission lines are crucial in integrated circuits and printed circuit boards, because these circuits have complex geometries and layout between the multi layers, and most of the transmission lines possess nonuniform characteristics. On the other hand, the nonlinear transmission line have been focused in the fields of communication and instrumentation. Here, we present a new numerical method for analyzing nonuniform and nonlinear transmission lines with linear and/or nonlinear terminations. The waveforms at any points along the lines are described by the Fourier expansions. The partial differential equations representing the circuit are transformed into a set of ordinary differential equations at each frequency component, where for nonlinear transmission line, the perturbation technique is applied. The method is efficiently applied to weakly nonlinear transmission line. The nonuniform transmission lines terminated by a nonlinear subnetwork are analyzed by hybrid frequency-domain method. The stability for stiff circuit is improved by introducing compensation element. The efficiency of our method is illustrated by some examples.

Adapting the principle of parametron oscillation, a small implantable temperature sensor requiring no internal power supply is described. Since this sensor's oscillation frequency is half that of the excitation frequency, the oscillated signal can be measured from the reception side, free of any signal, interference, simply by positioning the sensor and the excitation antenna so that; 1) they are separated up to 95 cm in the air; 2) a 41 cm gap, the phantom equivalent of the thickness of the human abdomen maintain between them. In the temperature-dependent quartz resonator sensor, oscillation occurs only when frequency and temperature correspond. The excitation power is then adjusted so that the frequency bandwidth narrows. As a result, the margin of error in measuring the temperature is minimized; (0.07).

In this paper, quantization method which can keep the phase and gain characteristics of a reference filter is proposed. The proposed method uses a genetic algorithm and a simulated annealing algorithm. The objective function used in this method is described with two kinds of weighting functions for identifying the phase and gain characteristics respectively. Therefore, the quantization accuracy on the gain characteristic is independent of the accuracy on the phase characteristic. Further, the proposed algorithm can be applied to any types of filters, because the chromosome expresses only their coefficients values. The efficiency of the proposed algorithm is verified by some experiments.

Orthogonal frequency division multiplexing (OFDM) has been receiving a lot of attention in the field of broadcasting because of its ruggedness under multipath environments. One of important issues to realize high quality reception of OFDM signals is to correct frequency and timing offsets between the transmitter and receiver so that orthogonality of the carriers can be maintained. This paper discusses a frequency and timing period acquisition technique for OFDM systems. A new offset estimation technique is introduced that detects both the frequency and timing peirod offsets at the same time by using only one pilot symbol with its suitable frequency assignment. A pseudo noise (PN) sequence is also introduced to assign these frequencies of the pilot symbol so that the frequency acquisition range can be widened. Numerical examples are given to show the estimate variances of the proposed frequency and timing period estimator over both additive white Gaussian noise (AWGN) and multipath fading channels. Also the bit error rate (BER) performance for an open loop acquisition system is examined.

This paper presents the computer simulation results on frequency reuse efficiency and soft handoff statistics in the CDMA forward link according to path loss and cell loading. The soft handoff threshold effect on the handoff statistics is also evaluated. The frequency reuse efficiency is not a fixed value but varying as function of distance from the home cell, path loss slopes, and cell loading. The total soft handoff pecentile ranges from 0.0 to 64.9 according to cell loading, even if path loss slope is constant.

A CMOS fully balanced current-mode filter is presented. A fully balanced current-mode integrator which is the basic building block is implemented by adding a very simple common-mode-rejection mechanism to fully differential one. The fully balanced operation can eliminate even order distortion, which is one of the drawbacks in previous continuous current-mode filter. Moreover, the additional circuit can work as not only common-mode-rejection mechanism but also Q-tuning circuit which compensates lossy elements due to finite output impedance of MOS FET. A prototype fifth-order low-pass lad-der filter designed in a standard digital 0.8µm CMOS process achieved a cut-off frequency (fC) of 100MHz; fC was tunable from 75MHz to 120MHz by varying a reference bias current from 50µA to 150µA. Using a single 3V power supply with a nominal reference current of 100µA, power dissipation per one pole is 30mW. The active filter area was 0.011mm2/pole and total harmonic distortion (THD) was 0.73 [%] at 80MHz, 80µA amplitude signal. Furthermore, by adjusting two bias currents, on chip automatic both frequency and Q controls are easily implemented by typical tuning systems, for example master-slave tuning systems [1].

This letter propose a fast frequency domain adaptive filter algorithm (FADF) for applications in which large order adaptive filters are required. Proposed FADF algorithm reduces the block delay of conventional FADF algorithms allowing a more efficient selection of the fast Fourier Transform (FFT) size. Proposed FADF algorithm also provides faster convergence rates than conventional FBAF algorithms by using a near-optimum convergence factor derived by using the FFT. Computer simulations using white and colored signals are given to show the desirable features of proposed scheme.

This paper proposes a half-chip offset QPSK (Quadrature Phase Shift Keying) modulation CDMA (Code Division Multiple Access) scheme to allow the simple differential detection while realizing a compact spectrum in nonlinear channels for wireless LAN systems. The experimental results show the proposed scheme achieves excellent Pe (probability of error) performances in ACI (adjacent channel interference) and CCI (co-channel interference) environments. Moreover, by employing time diversity and high-coding-gain FEC (Forward Error Correction), the half-chip offset QPSK-CDMA scheme realizes an improvement of 3.0 dB (in terms of Eb/No at a Pe of 105) in Rician fading environments with a Doppler frequency fD of 10 Hz and a delay spread of 40 nsec.