In this work, a statistical analysis is performed for a simple constrained high-order Yule-Walker (YW) tone frequency estimator obtained from the first equation of the constrained high-order YW equations. Explicit expressions for its estimation bias and variance are efficiently derived by virtue of a Taylor series expansion technique. Especially, being explicit in terms of frequency, data length and Signal-to-Noise Ratio (SNR) value, the resulting bias expression can not be obtained by using the asymptotic analyses used for the parameter estimation methods. The obtained expressions are compared with their counterparts of the Pisarenko tone frequency estimator. Simulations are performed to support the theoretical results.

Considered is the theory of several dielectric waveguide phenomena for which the vector nature of the electromagnetic field is essential. These phenomena are the following rotation of the plane of polarization in chiral and twisted waveguides, Bragg's reflection in a twisted waveguide in a narrow frequency band, and excitation of a waveguide at a near-cutoff frequency.

This paper proposes a technique for estimating the harmonic frequencies based on instantaneous frequency (IF) of speech signals. The main problem is how to decompose the speech signal into the harmonic components. For this purpose, we use a set of bandpass-filters, each of whose center frequencies changes with time in order to track the instantaneous freuency of its output. As a result, the outputs of the band-pass filters become the harmonic components, and the instantaneous frequencies of the harmonics are accurately estimated. To evaluate the effectiveness of the approach, we apply it to pitch determination of speech. Pitch determination is simply accomplished by selecting the correct fundamental frequency out of the harmonic components. It is confirmed that the pitch extraction using the proposed pitch determination algorithm (PDA) is stable and accurate. The most significant feature of the PDA is that the extracted pitch contour is smooth and it requires no post-processing such as nonlinear filtering or any smoothing processes. Several examples are presented to demonstrate the capability of the harmonics estimation technique and the PDA.

The influence of cochannel, adjacent channel and intermodulation constraints on the capacity of the frequency band in the dynamic channel allocation problem is estimated. Algorithms including a backtracking phase with partial reassignment of currently assigned requirements are proposed. Numerical examples show a strong possibility of a 20% capacity improvement compared to the conventional strategies.

This paper discusses the performance of non-coherent reception for M-ary spread-spectrum (M-ary/SS) signals in the presence of carrier frequency offset. In general, the M-ary/SS scheme is expected to be of higher spectral efficiency than the conventional DS/SS schemes, but its performance may be degraded by the carrier frequency offset. We, therefore, analyze the effect of carrier frequency offset on the performance of the non-coherent M-ary/SS system with orthogonal modulation using a set of sequences generated by the Hadamard matrix. As a result of the analysis, it has been found that the carrier frequency offset may cause a great deal of degradation in the performance, and that its effect has a distinctive property which is due to the characteristic of Hadamard matrix, at the same time. Making use of this property, we propose two schemes that can mitigate the effect of carrier frequency offset: one is based on choise of the code sequences, the other is on the error correcting code. The effectiveness of the schemes is evaluated in the terms of symbol-error-rates through analysis and computer simulation.

This paper proposes a multiple optical wideband frequency modulation system and clarifies its phase noise insensitivity. In this system, an optical carrier is phase-modulated by a conventional FM signal to generate many sidebands in optical frequency band. The n-th order sideband component yields also FM signal with frequency deviation of n times the one of original FM signal. Therefore, by selecting the high order optical sideband, the wideband optical FM signal can be obtained. Moreover, if some sidebands are simultaneously extracted and multiplied at the receiver, a wideband FM signal with larger frequency deviation and no laser phase noise can be obtained, and FM threshold extension can be realized.

A 0.1-µm gate-length GaAs MESFET technology is reported. A 48.3-GHz dynamic-frequency divider, and an amplifier with 20-dB gain and 17.5-GHz bandwidth are successfully fabricated by integrating over-100-GHz-cut-off frequency MESFETs using a new lightly-doped drain structure with a buried p-layer (BP-LDD) device structure.

Time-frequency representations (TFRs) have been developed as tools for analysis of non-stationary signals. Signal dependent TFRs are known to perform well for a much wider range of signals than any fixed (signal independent) TFR. This paper describes customised and sequential versions of the signal dependent TFR proposed in [1]. The method, which is based on the use of the Radon transform at distance zero in the ambiguity domain, is simple and effective in dealing with both simulated and real data. The use of the described method for time-scale analysis is also presented. In addition, the paper investigates a simple technique for detection of noisy chirp signals using the Radon transfrom in the ambiguity domain.

Multifrequency microwave radiometry has been investigated for non-invasive measurement of temperatures in a human body. In this paper, we propose a new temperature profile model function, which is based on thermo-physiological considerations, for use in model fitting method of retrieving a temperature profile from a set of multifrequency radiometric data. The microwave radiometric technique using the new model function was tested by numerical simulations against animal experiment and clinical data reported elsewhere. The results show that the microwave radiometric technique can be used effectively to measure temperature profiles in tissues over a depth range from 0 to about 4.5 cm.

The distributed measurement-based quasi-fixed frequency assignment (also known as quasi-static adaptive frequency assignment-QSAFA) methodology is a practical solution for frequency assignment in the emerging TDMA personal communications networks (PCN/PCS). Five different QSAFA algorithms are studied in this paper under different interference threshold settings. It is found that a simple aggressive algorithm without using a threshold (LIA-Least Interference Algorithm) performs the best under the conditions studied. The performance of this algorithm is also justified by the theoretical proof presented at the end of this paper.

Spectrum scrambling can be applied in vehicle telephones for more secure communication. This letter shows a spectrum scrambling method using real coefficients M band uniform QMF banks. Once QMF banks are designed, spectrum scrambling filters can be realized with simpler procedures. By introducing selectors in the filters, the scrambling scheme may be easily varied in real time processing. Design examples and experimental simulations are included.

To support high bit rate and high quality indoor radio communication systems, we have to solve intersymbol interference (ISI) problem caused by frequency-selective fading. Recently multi-carrier modulation technique is considered to be one of the effective methods for this problem. In this paper we propose Partial Frequency ARQ (Automatic Repeat reQuest) system which can achieve effective ARQ scheme for multi-carrier packet communication. This system operates partial retransmission of erroneous power faded packets, and it is superior to the traditional ARQ systems. Furthermore two different protocols are examined for this system: Static Carrier Assignment (SCA) and Dynamic Carrier Assignment (DCA). By computer simulation we found that DCA method can achieve better performance than SCA in terms of both throughput and packet transmission delay.

The subject is the horizontal coil's temperature rise in DY for high frequency by being unavoidable for the tendency of more information on display monitor equipments. Writers made the temperature-balance model from a point of view that this temperature rise is coming from the heat rise and the conductivity, and we expressed the temperature rise of DY by using amount of the heat rise and conductivity characteristics of each element. Also, we indicated the method to decide about the selection of the wire size of coils, the section area and deflection sensitivity, with regard to reducing the temperature rise. We confirmed the effect of the temperature rise reduction by about 9 on products, under the condition of 64 kHz horizontal frequency.

A method of tone recognition has been developed for dissyllabic speech of Standard Chinese based on discrete hidden Markov modeling. As for the feature parameters of recognition, combination of macroscopic and microscopic parameters of fundamental frequency contours was shown to give a better result as compared to the isolated use of each parameter. Speaker normalization was realized by introducing an offset to the fundamental frequency. In order to avoid recognition errors due to syllable segmentation, a scheme of concatenated learning was adopted for training hidden Markov models. Based on the observations of fundamental frequency contours of dissyllables, a scheme was introduced to the method, where a contour was represented with a series of three syllabic tone models, two for the first and the second syllables and one for the transition part around the syllabic boundary. Corresponding to the voiceless consonant of the second syllable, fundamental frequency contour of a dissyllable may include a part without fundamental frequencies. This part was linearly interpolated in the current method. To prove the validity of the proposed method, it was compared with other methods, such as representing all of the dissyllabic contours as the concatenation of two models, assigning a special code to the voiceless part, and so on. Tone sandhi was also taken into account by introducing two additional models for the half-third tone and for the first 4th tone of the combination of two 4th tones. With the proposed method, average recognition rate of 96% was achieved for 5 male and 5 female speakers.

Microwave radiometry has been investigated for non-invasive measurement of temperature in human body. Recent trends are to explore the capability of retrieving a temperature profile or map from a set of brightness temperatures measured by a multifrequency radiometer operating in a 1-6GHz range. The retrieval of temperature from the multifrequency measurement data is formulated as an inverse problem in which the number of independent measurement or data is limited (7) and the data suffer from considerably large random fluctuations. The standard deviation of the data fluctuation is given by the brightness temperature resolution of the instrument (0.04-0.1K). Solutions are prone to instabilities and large errors unless proper solution methods are used. Solution methods developed during the last few years are reviewed: singular system analysis, bio-heat transfer solution matched with radiometric data, and model-fitting combined with Monte Carlo technique. Typical results obtained by these methods are presented to indicate a crosssection of the present-state-of-the-development in the field. This review concludes with discussions on the radiometric weighting function which connects physical temperatures in object to the brightness temperature. Three-dimensional weighting functions derived by the modal analysis and the FDTD method for a rectangular waveguide antenna coupled to a four layered lossy medium are discussed. Development of temperature retrieval procedures incorporating the 3-D weighting functions is an important and challenging task for future work in this field.

To make medical telemetry system more reliable in severe electromagnetic environment, we applied spread spectrum communication to ECG data transmission method. Spread spectrum communication system has shown superior performances to other systems, especially, in respect of anti-jamming, which allows it to share the frequency band with current telemetry systems. In this study, we show the characteristics of a spread spectrum transmitter when it is used in the same frequency band as a narrow-band transmitter. The result shows that the spread spectrum telemetry system can use the same frequency band permitted for medical telemetry system.

We report here a pulsed lightwave frequency synthesizer system that is composed of a pulsed lightwave sweep frequency generator and a tracking generator. The key advance in the sweep generator is the use of a dynamically gain controlled EDFA. The combination of feedback and feed forward dynamic gain control effectively compensates EDFA gain fluctuation and equalizes fiber loop loss so that the initial pulse wave form and amplitude is retained in the loop at large circuit numbers. Over 1000 pulsed lightwave frequencies are synthesized in 250MHz steps by the sweep generator. Almost flat response (0.55dB variation) is realized up to 240GHz. The power spectrum decreases by 67% (1.7dB down) at 250GHz. The peak level of the pulses output from the loop is about -4dBm. Tracking generator and total synthesizer system performance are evaluated by (a) beat frequency between the tracking generator and the master lightwave source, (b) beat frequency between two tracking generators, and (c) a frequency chain between the master lightwave source and another HCN stabilized lightwave source via the synthesizer system. A continuous lightwave frequency locked to a frequency selected from the pulsed sweep frequency signal is demonstrated at over 200GHz to have an instability of 5MHz. Absolute accuracy of the lightwave frequency emitted from the synthesizer system is about 10MHz. Therefore, the relative accuracy of the lightwave frequency is as high as 510-8.

The performance of trellis coded hybrid frequency and phase shift modulation (TC HFPSK) with the expurgated phase code and the asymmetric signal constellation is investigated by using the minimum squared free Euclidean distance d 2free and the bit error rate (BER). It is found that TC hybrid 2FSK/4PSK with the expurgated phase code shows larger d 2free than the corresponding TC hybrid 2FSK/4PSK with the complete phase code for varying the angle φ that determines the asymmetric signal constellation. The maximum value of d 2free of TC hybrid 2FSK/4PSK with the expurgated phase code can be obtained when the signal constellation is symmetric. The performance of BER is analyzed in additive white Gaussian noise (AWGN) and fading channels by using uniform error property and error bound based on transfer function. It is found that the coding gain of TC hybrid 2FSK/4PSK with the expurgated phase code over uncoded hybrid 2FSK/2PSK at BER=10-4 are 2.71dB and 4.74dB in AWGN and fading channels, respectively. The performance improvements of TC hybrid 2FSK/4PSK with the expurgated phase code over TC 8PSK at BER=10-4 are 0.68dB and 4.07dB in AWGN and fading channels, respectively.

A calculation method by the improved three-fluid model is shown to describe phenomenologically temperature and frequency dependence of surface resistance Rs for high-Tc superconductors. It is verified that this model is useful to describe temperature dependence of Rs for such high-Tc superconducting films as Y-Ba-Cu-O (YBCO), Eu-Ba-Cu-O, and Tl-Ba-Ca-Cu-O films. For the frequency dependence of Rs of a YBCO bulk, furthermore, the measured results which have not depended on f2 in the frequency range 10-25 GHz, can be described successfully by this model. Finally, a figure of merit is proposed to evaluate material quality for high-Tc superconductors from the values of electron densities and momentum relaxation time determined by the present model.

In this paper, we propose an efficient method (called DIRIC algorithm) to allocate carrier frequencies so as to minimize intermodulation products in two-level SCPC systems in which Hub station and many Remote stations communicate each other through satellite transponder. We also present a very efficient method to evaluate intermodulation products with substantially reduced CPU time in two-level SCPC systems. We compare and analyze the performance of several frequency allocation methods to extend DELINS-INSDEL algorithm (which is proposed by Okinaka) to two-level SCPC systems. When the proposed algorithm is applied to systems with modulated carrier, it is verified that this algorithm has the same efficiency as the unmodulated carrier. It is also shown heuristically that certain initial assignment algorithms perform better than random assignment.