David K. Asano

Preparation and properties of polypyrrole

Optimal conditions and improvement methods for electrochemical polymerization of pyrrole (Py) in the presence of sodium p-toluenesulfonate (PTS) as a dopant in water were studied. The electrical and spectral properties of poly-Py (PPy) doped with PTS were compared with those of PPy doped with sodium alkylbenzenesulfonates such as sodium benzenesulfonate (BS), sodium 4-ethylbenzenesulfonate (EBS), sodium 4-n-octylbenzenesulfonate (OBS), sodium dodecylbenzenesulfonate (DBS) and tetraethylammonium p-toluenesulfonate (Et 4 NPTS), prepared under the same polymerization conditions. UV-Vis-NIR absorption spectra were independent of the electrolytes used.

Serial unequal error-protection codes based on trellis-coded modulation

Unequal error-protection (UEP) codes that are designed using trellis-coded modulation (TCM) are proposed for use with a single data stream consisting of information with two levels of importance. To achieve UEP, the proposed scheme encodes the data according to the importance of the information by switching between two codes which use different signal constellations. Using simple trellis codes, it is shown that the error rate of the important information is lower than the error rate for an equivalent equal error-protection scheme.

A three-dimensional sound intensity measurement system for sound source identification and sound power determination by ln modelsa)

This paper describes a full vector intensity probe which advances the field of sound intensity and sound source direction estimation using six matched rotating and variable directional microphones. The probe has three pairs of microphones at an equal spacing of 30 mm that are set up in each of the x, y, and z directions and share the same observation point. The calibration method using the rotating microphone system is effective to correct position errors in the y- and z-axes microphone pairs. Sound intensity measurements using the variable directional microphone method can locate with accuracy a sound source, i.e., the structure parts radiating most acoustic energy. The system can find the maximum sound intensity level and beamwidth of the major lobe, and the peak sound intensity levels of the minor lobes. Therefore, a procedure for sound power determination based on minimum measurement data is theoretically and experimentally discussed. Consequently, it is possible to reconstruct only parts of the syste...

Improved post-detection processing for limiter-discriminator detection of CPM in a Rayleigh, fast fading channel

A simple, robust processing strategy, called the fading magnitude-integrate sample and dump (FM-ISD) processor, is proposed for use with limiter-discriminator detection of CPM signals in Rayleigh, fast fading channels. The FM-ISD processor is introduced as a simplification of an optimal estimator-correlator receiver. The performance is compared to a standard integrator processor and found to provide an improvement in performance for all values of signal-to-noise ratio. The FM-ISD processor is also shown to be robust to changes in modulation format, channel fading rate and pre-detection filter type. >

Acoustic characteristics of an electrodynamic planar digital loudspeaker

In this paper, an electrodynamic planar loudspeaker driven by a digital signal is experimentally discussed. The digital loudspeaker consists of 22 voice coils, 11 permanent magnets, a diaphragm with streamlined sections molded in plastic, and a suspension made of handmade Japanese paper between the diaphragm and the frame. First, the acoustic responses are affected by the arrangement of the voice coils, so an asymmetric arrangement is studied. This asymmetric arrangement is designed to obtain as flat a frequency response to an analog signal as possible. This arrangement is compared with a symmetric one and results show that the flatness of the frequency response around 1 kHz and 4 kHz is improved and that the sound reproduction band is from 40 Hz to 10 kHz. Second, to evaluate the acoustic responses to a digital signal, the digital loudspeaker is driven with a pulse code modulation signal. Results show that the digital loudspeaker can reproduce pure sound with a total harmonic distortion of less than 5% from 40 Hz to 10 kHz, exceeding this value only in a narrow frequency band near 4 kHz. This digital loudspeaker was demonstrated to have good linearity over its dynamic range of 84 dB.

Optimization of coded GMSK systems

In this article, block and convolutional coding for Gaussian minimum shift keying (GMSK) in additive white Gaussian noise (AWGN) channels is investigated. The performance improvement that can be obtained without an increase in bandwidth is found for block and convolutional codes with various block lengths and constraint lengths, respectively, when a simple suboptimal demodulation scheme is used. For a fixed system transmission bandwidth, the tradeoff between the percentage of bandwidth to use for coding and the percentage to use for modulation is examined and optimized for various values of bandwidth.

Single-carrier transmission frequency-domain equalization based on a wiener filter

Recently, frequency-domain equalization for single-carrier transmission (SC-FDE) has been given much attention. For example, the up-link in the 3.9 generation mobile phone long term evolution (LTE) system, an SC-FDMA method using SC-FDE and multiple access will be adopted. However in previous research, there are many papers describing the features and advantages of SC-FDE based on a comparison of SC-FDE and orthogonal frequency-division multiplexing (OFDM) systems. In this paper, we discuss single-carrier transmission equalization in the time-domain (SC-TDE) and SC-FDE in a unified way centered on the Wiener filter based on the minimum mean square error (MMSE) criterion. As a result, we could get useful information and pointers, especially for when we want to replace existing SC-TDE technology with SC-FDE technology.

Modulation and processing gain tradeoffs in DS-CDMA spread spectrum systems

Continuous phase modulation (CPM) schemes are examined for use in DS-CDMA spread spectrum systems. Since the power spectra of CPM schemes are narrower than BPSK schemes, a larger processing gain can be used for the same overall bandwidth after spreading. The processing gain, relative to BPSK, that can be used with CPM is calculated. As an example, it is shown that the performance of an MSK system is better than a BPSK system for an equivalent overall bandwidth.

Phase smoothing functions of full response CPM

Continuous phase modulation (CPM) is examined for low-complexity receivers, i.e. those that operate on only one symbol interval. The tradeoff between the bandwidth and bit error rate (BER) performance of these simple systems is studied. The phase-smoothing functions that minimize the effective bandwidth for a given BER are calculated. A linear and polynomial approximation to these phase-smoothing functions are chosen. The three families are compared using their bandwidth-BER performance tradeoffs, power spectral densities, out-of-band powers, and bandwidth efficiencies. It is shown that CPM schemes with small modulation indices (h<or=0.5) offer good tradeoffs between bandwidth and BER performance.<<ETX>>

Automatic Modulation Identification Using a Frequency Discriminator

In this paper, an automatic identification method based on frequency discrimination is proposed. The proposed method can be used when the received signal is a constant envelope modulation scheme. To test the proposed method PSK and FSK are considered. Using computer simulations, the performance of the proposed method was evaluated and found to be able to distinguish between PSK and FSK well even in the presence of noise.