This paper presents a new sort of multilayer piezoelectric ceramic transformer for switching regulated power supplies. This piezoelectric transformer operates in the second thickness extensional vibration mode. Its resonant frequency is higher than 1 MHz. First, numerical simulation was implemented using a distributed constant electromechanical equivalent circuit method. It was calculated that this piezoelectric transformer, which has higher than 200 mechanical quality factor Qm, could work with higher than 90% efficiency and in more than 20-W/cm3 high power density. Second, a trially fabricated transformer, which is 15 mm long, 15 mm wide and 2.2 mm thick, was examined. Modified PbTiO3 family ceramics were used for the piezoelectric transformer material, because of the large anisotropy between electromechanical coupling factors kt and kp. Obtained results indicate that the piezoelectric transformer has good resonant characteristics, with little spurious vibration, and exhibits 16-W/cm3 power density with high efficiency at 2 MHz. Moreover, a switching regulated power supply, applying the piezoelectric ceramic transformer, was built and examined.

In this paper, we subjects the case that frequency–shift–keying (FSK) modulation and phase locked loop (PLL) demodulator are used in frequency hopped spread spectrum (FH–SS) communication system. So the carrier frequencies of undesired transmitters may come into collision with the carrier frequency of desired transmitter in this communication system, we evaluate the response of PLL by two sinusoidal inputs so as to estimate how the response of PLL demodulator is affected by the collision of carrier frequencies. First, we compute the synchronization diagrams of PLL with two sinusoids. From this, it is indicated that allowable value of amplitude ratio of interference transmitter's signal to disired transmitter's signal decreases with increasing FSK modulation width of desired transmitter. Next, we calculated the output of PLL demodulator with two sinusoids. To this end, it is shown that the allowable value of amplitude ratio is bounded by a constant value even if FSK modulation width is enough small.

We propose and demonstrate an excellent linearly frequency-swept laser diode (LD) for sensing system utilizing frequency-moduleted continuous-wave (FMCW) technique. In order to linearly sweep the optical frequency, we adopt a reference interferometer and an electric phase comparator. The interference beat signal of the reference interferometer is phase-compared with an external reference rectangular signal having a fixed frequency near the interference beat signal frequency by a lock-in amplifier. The error signal from the lock-in amplifier is fed back to the modulating signal of the injection current of the LD. Thus, a phase-locked loop composed of optical and electric circuits can be established, and the beat signal frequency is locked to the frequency of the reference signal. The optical frequency of the LD is, therefore, excellently linearly swept in time. In order to experimentally confirm the linearlity of the proposed method, we apply this light source to the FMCW reflectometry. Resultingly, the improvement of the linearity is estimated to be about 10 dB. And the theoretically limited spatial resolution of the FMCW reflectometry is achieved.

We report the development of high-performance small-scale AlGaAs/GaAs collector-up heterojunction bipolar transistors (C-up HBT) with a carbon (C)-doped base layer. Oxygen-ion (O+) implantation is used to define their intrinsic emitter/base junctions and zinc (Zn)-diffusion is used to lower the resistivity of their O+-implanted extrinsic base layers. The highly resistive O+-implanted AlGaAs layer in the extrinsic emitter region sufficiently suppresses electron injection even under high-forward-bias conditions, allowing high collector current densities. The use of a C-doped base is especially effective for small-scale C-up HBT's because it suppresses the undesirable turn-on voltage shift caused by base dopant diffusion in the intrinsic area around the collector-mesa perimeter that occurs during the high-temperature Zn-diffusion process after implantation. Even in a small-scale trasistor with a 2 µm2 µm collector, a current gain of 15 is obtained. A microwave transistor with a 2 µm10 µm collector has a cutoff frequency fT of 68 GHz and a maximum oscillation frequency fmax of 102 GHz. A small-scale C-up HBT with a 2 µm2 µm collector shows a higher fmax of 110 GHz due to reduced base/collector capacitance CBC and its fmax remains above 100 GHz, even at a low collector current of 1 mA. The CBC of this device is estimated to be as low as 2.2 fF. Current gain dependence on collector size is also investigated for C-up HBT's and it is found that the base recombination current around the collector-mesa perimeter reduces the current gain.

This paper reports on the properties of thin-film thermal switches that are monolithically fabricated on high-Tc superconductive filter. Operating at a wide temperature range of 50-77 K, it was found that the switch could control the center frequency by -10 MHz with an increased insertion loss of less than 0.7 dB. In an on-off switching operation of filter characteristics using thin-film switches, power consumption was approximately 20 mW at 77 K, and the signal decay time as a switching speed was 30 ms at 76 K with a switch current of 70 mA. The decay time decreased exponentially as the switch current or the temperature setting increased.

In this paper, the Pisarenko and the Constrained Yule-Walker (CYW) estimators of a tone frequency are first newly derived from the viewpoint of using directly the autocorrelation coefficients. Then, simulation of these two estimators is carried out in some detail. The simulation results show that compared with the Pisarenko estimator the CYW estimator, which has not been adequately studied, works poorly for low and moderate Signal-to-Noise Ratio (SNR) values. However, in case of high SNR value, it yields very small bias and comparable estimation variance, and thus produces more accurate tone frequency estimates.

The magnitude of low frequency noise is studied in a Nb-(nanoconstrictions)-NbN system with adjustable current-voltage characteristics. We find that the magnitude of low frequency noise decreases sharply with increasing the subgap conductivity of the device. We suggest a qualitative explanation of this observation in terms of gradual build up of the nanoconstriction region by field assisted growth. The decrease of low frequency noise is related to the "cleanliness" of the system as measured by the amount of Andreev reflection-related conductivity. The scaling of the magnitude of low frequency noise with device resistance is also discussed.

A new frequency hopped spread spectrum system is introduced. The frequency hopped signal is a combination of multi frequency and multi phase signals and is referred to as Frequency Hopped/Joint Frequency-Phase Modulation (FH/JFPM). A noncoherent receiver for the FH/JFPM signals is introduced and an exact expression for the bit error rate is obtained. A performance analysis of this system is given in the presence of broadband and partial-band noise jamming. The optimal jamming strategy is evaluated. The results show that under these jamming conditions the FH/JFPM perform better than the FH/M-ary DPSK and FH/M-ary FSK systems. It is also shown that for a given channel bandwidth and data rate, the FH/JFPM system has more processing gain than its FSK or DPSK counterparts.

This paper examines the retransmission probability and throughput characteristics of slow-frequency-hopping spread spectrum transmission in Rayleigh fading indoor channels of multi-cell environments. Because signal strength in a Rayleigh fading indoor channel changes slowly, retransmission probability is little influenced by the retransmission unit length and error correction capability when retransmission unit length is shorter than the fading period. With the 83.5MHz bandwidth of the 2.4GHz ISM (Industrial, Scientific, and Medical) band in the USA, quaternary phase shift keying (QPSK) is expected to provide a throughput of nearly 1Mbps in each cell when we assume a shadowing margin of 18.1dB and we use 4 cells, 100 hopping frequencies, a transmission power of 600mW, and a transmission distance of 20m. And also with the 26MHz bandwidth of the 2.4GHz ISM band in Japan, QPSK is expected to provide a throughput of nearly 1Mbps in each cell under similar conditions but with 26 hopping frequencies and a transmission power of 260mW.

The biological effects of power frequency electric and magnetic fields have been a source of concern for the past many years, especially since 1979 when an epidemiological study report suggested a positive relationship between childhood cancer and exposure to power frequency electromagnetic fields from residential overhead power lines. The extensive studies of dosimetry and biological effects have since been carried out. It is believed that power frequency electromagnetic fields does induce biological effects (no serious threat to human health). The clear explanations for the possible interaction mechanisms remain to be identified. The problem with the study on dosimetry has been lack of theory that applies to the physical interaction of power frequency electric and magnetic fields with humans. At present, it seems to be widely accepted that the density of induced currents in the human body can be used as the decisive parameter in evaluating human exposure to these fields. In order to predict the distribution of induced current density inside a human body exposed to electric fields, magnetic fields, or electric and magnetic fields that coexist, the precise measurements of electromagnetic environments are necessary. According to necessity, the fields have to be characterized in terms of strength, orientation and phase angle. This paper presents: (1) Measurements of power frequency electromagnetic environments in 187kV substation yard and in the vicinity of the ground under 187 kV line using laboratory-made instruments; (2) Development of magnetic field exposure monitor; and (3) Review of state of the art of theoretical dosimetry for electric fields, magnetic fields and combined electric and magnetic fields, and evaluation method of human exposure for the future research.

The dielectric resonator method is now widely accepted as a precise measurement method for determining the dielectric properties at microwave frequencies. This paper describes the measurement results of εr, tan δ and TCf determined by a round robin test of this method. The resultant measurement errors were Δεr/εr0.10%, Δtan δ0.5105 and ΔTCf0.5 ppm/K, where Δdenotes a standard deviation. The causes of measurement errors and the conditions to improve the measurement accuracy are discussed.

An experimental SAR (Specific Absorption Rate) estimation system based upon the thermograph method using a thermograph camera and newly developed homogeneous dry-phantom human models are presented. Experiments are conducted using this system and UHF fields to obtain SAR distributions in the human head irradiated by hand-held portable radios. Experiment results show that the estimated peak SAR's due to the radiation waves from radios of 1W transmitting power are lower than 2W/kg and so conform to the recommendations of the radio-frequency radiation safety guidelines. The developed system enables the surface SAR distributions on the phantom model to be precisely estimated; a function not available with the original system. System parameters required for providing precise estimations are discussed first, and then experiments are conducted to estimate SAR's in the human head exposed to a UHF hand-held portable radio's near field. Finally, estimated data are examined from the viewpoint of radio-frequency exposure safety guidelines.

This paper describes a nondestructive measurement method for complex permittivity of dielectric material at pseudo microwave frequencies. The resonator used in this study has a cylindrical cavity filled with a sapphire material of a well known complex permittivity. The resonator is divided into two parts at the center. A dielectric substrate specimen is clamped with these halves. Relative permittivity εand loss tangent tan δ of the specimen are obtained at 3 GHz using the TE011 resonance mode. The accuracy of the present method is evaluated through the comparison of the measured values by the new method with those at around 10 GHz by the conventional empty cavity resonator method. The errors of measurements are smaller than 1% and 1105 for εand tan δ, respectively.

An estimation method for efficiently calculating the field intensity in the Fresnel region of broadside colinear array antennas is developed, and its performance is experimentally verified. The calculation utilizes only the antenna design data, and is readily applicable to arbitrary array antennas. This method can provide a safety protection zone in the proximity of array antennas, in order to protect radio communication personnel and general public from the potentially hazardous radiofrequency exposure.

An improvement of Q evaluation is discussed. The Resonance Curve Area method was confirmed to give a deviation in the order of 6104. The result was three times more accurate than the widely known Q evaluating method which utilizes the cursor function installed in a network analyzer. A discussion is also made on the physical validity of the RCA method. It is shown that the application of the RCA method improves the accuracy of the cavity perturbation method. Actual measurements have shown that the deviation of dielectric constant is less than 1% and that of the loss tangent is less than 3%, in the order of 104. The accuracy of the RCA method was estimated to be three times that of the conventional cavity perturbation technique. The consistency of the perturbation with other methods has also confirmed. The accuracy comparison to more accurate formulae derived from a rigorous solution have shown that the difference is sufficiently small.

In this paper, the relationship between the recursive least square (RLS) method with a U-D decomposition algorithm and ARMA lattice filter realization algorithm is presented. Both the RLS method and the lattice filter realization algorithm are used for the same applications, such as model identification, etc., therefore, it is expected that the lattice filter algorithm is in some ways related to the RLS. Though some of the proposed lattice filter algorithms have been derived by the RLS method, they do not express the relationship between RLS snd ARMA lattice filter realization algorithm. In order to describe the relation clearly, a new structure of ARMA lattice filter is proposed. Further, based on the relationship, a method of model identification with frequency weighting (MIFW), which is different from a previous method, is derived. The new MIFW method modifies the lattice parameters which are acquired without a frequency weighting and obtain the parameters of an ARMA model, which is identified with frequency weighting. The proposed MIFW method has the following restrictions: (1) The used frequency weighting is FIR filter with a low order. (2) By using the parameters of the ARMA lattice filter with ARMA (N,M) order and the frequency weighting with L order, the new ARMA parameter with the frequency weignting is with ARMA(N-L,M-L) order. By using the proposed MIFW method, the ARMA parameters estimated with the frequency weighting can be obtained without starting the computation again.

This paper proposes Coherent-HYBrid Direct-Sequence Fast-Frequency-Hopping (CHYB-DS-FFH) CDMA with Adaptive Interference Cancelling (AIC) for cellular mobile communications. The features of CHYB-DS-FFH are symbol-by-symbol frequency diversity and low chip-rate DS multiplexing both of which are based on a coherent FFH modulation and demodulation scheme. The combination of coherent FFH, space diversity, and AIC is very effective for reducing the performance degradation due to interference. Computer simulations demonstrate BER performance of a 2 hop 500-kHz-interval frequency hopping system using () a linear canceller or () a nonlinear canceller. Both systems employ the two branch space diversity reception of 10kb/s QPSK with FFH over a 1MHz system bandwidth. In quasi-static channels, the average BER performance is 10-2 with average Eb/N0 less than 8dB. In dynamic fading channels under full interference conditions, CHYB-DS-FFH with the linear adaptive interference canceller realizes a BER of 10-2 at the average Eb/N0 of 15dB with maximum Doppler frequency fD of 5Hz, whereas CHYB-DS-FFH with the non-linear adaptive interference canceller achieves the same BER at the average Eb/N0 of 15dB with fD, equal to 30Hz.

This paper proposes a digitalized quadrature modulator for burst-by-burst carrier frequency hopping in TDMA-TDD systems. It employs digital frequency synthesis and a multiplexing modulation scheme to give the frequency offset to the modulated IF signal. Moreover, to reduce the frequency settling time of the RF synthesizer below the guard time duration, a phase and frequency preset (PFP) PLL synthesizer is employed. By employing the digital modulation scheme, the proposed modulator needs only one D/A converter, as a result, the complexity of adjusting the DC offset and amplitude between analog signals of the in-phase and the quadrature phase is eliminated. The performance of the proposed modulator is analyzed theoretically and simulated by computers. Theoretical analyses show that the frequency settling time with 15MHz hopping width in the 1900MHz band is reduced by more than 75% from that of the conventional synthesizer. The settling time is less than 40µs which is shorter than the typical guard time of the burst signal format. The analyses also show that the power consumption of the proposed modulator is lower than that of the conventional modulator employing a full band digital frequency converter. Furthermore, the computer simulation confirms that the power spectra and the constellations of the proposed modulator for the coherent and the π/4-shift QPSK modulation schemes can be successfully generated.

An improved reflection wave method was described for measurement of complex permittivity of low-loss materials over 100MHz-1GHz range. The residual impedance Zr and stray admittance Ys surrounding the test sample, which terminated the transmission line, were evaluated using sapphire as a reference material. The correction by the obtained Zr and Ys gave accurate values of complex permittivities of alumina and mullite ceramics as 100MHz-1GHz.

Among various photonic switching technologies, photonic frequency division multiplexing technology is most promising. In this paper a novel photonic FDM (Frequency Division Multiplexing) system is proposed. The proposed system consists of n (multiplicity of frequencies) independent subnetworks, each of which is identified by a specific frequency, and of which each network topology is identical. When a connection is required by a terminal, the network selects a subnetwork that can afford it, and assigns a frequency representing the selected subnetwork to the terminal. This system eliminates frequency converting devices and traffic concentration equipment, which will reduce the size and cost of the system. A very small sized switching system of very large capacity will be easily realized. In this paper, first we will address the basic concept of the proposed system, and then discuss some technical problems and their solutions concerning network configuration, switch matrix structure, subscriber network configuration, control scheme and frequency multiplicity. Some experimental results are also mentioned.