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This paper describes a design of time-to-digital converter (TDC) using a two-level conversion scheme. The first level is accomplished by a multi-phase sampling technique with the aid of delay-locked loop (DLL). Then the input signal and its adjacent sampling clock are manipulated and sent into a vernier delay line (VDL) sampling circuit at the second level. The proposed TDC can provide high resolution with less hardware compared to one level VDL sampling circuit with the same dynamic range. A new architecture of dual DLL circuit is also implemented to stabilize delay control against process and ambient variations. A test chip is designed and fabricated in 0.35-[micro]m logic technology. With an input reference clock within 130 to 160 MHz, the TDC achieves 24 to 30 ps resolution. The DNL is less than [+ or -] 0.55 LSB and INL is within +1 to -1.5 LSB. Index Terms--Delay-locked loop, time-to-digital converter (TDC), Vernier delay line.

In this paper, a new coding architecture for M-ary fiber-optic synchronous code division multiple access (CDMA) network is proposed to provide real-time multimedia broadcasting. In contrast with variable bit rate (VBR) transmission, the constant bit rate (CBR; i.e. isochronous) transport is more preferable in views of networking simplicity. We apply bit-stuffed unipolar m-sequence and maximum a posteriori (MAP) receiver in the proposed network. The system performance is determined by the following parameters: (1) number of simultaneous access broadcasting hosts K, (2) received laser power, (3) input bit rate, and (4) dimension of M. Furthermore, the adverse impact (thermal noise, APD noise) in the photodetection process is carefully analyzed. Numerical results reveals that for binary case, the aggregate capacity can achieve 10.2 Gbps.

This paper investigates the feasibility of a radio-over-fiber network, which employs a single high-power Nd:YAG laser shared among many microcells. External amplitude modulators are employed at both base station (BS) and radio ports (RP's) to form an optical fiber distribution network. The distortions induced by the uplink remodulation are analyzed. The optimal preamplifier gain in the uplink is estimated for given sensitivity and dynamic range (DR). Appropriate modulator linearization and thermal-noise suppression schemes are utilized together to improve the DR. The clipping distortion for the predistortion-linearized modulator is also considered. The result shows that the effects of clipping and higher order distortions have little impact on the estimation of the system performance. A numerical example shows that a 100-mW Nd:YAG laser can provide for a macrocell of 5-km radius up to 16 microcells and 1600 channels when a 20-dB modulator linearization and 10-dB thermal-noise suppression are employed. The experiment setup uses a two-tone test to verify the theoretical calculation. The measurement agrees with the theoretical estimation very well. Index Terms - Microcellular, optical fiber network, radio port.

The proper electrode placement in applying cepstral coefficients for electromyogram (EMG) signature discrimination was investigated. We measured EMG signals of different motions with two electrode arrangements simultaneously. Electrode pairs were located separately on dominant muscles (S-type arrangement) and closely in the region between muscles (C-type arrangement). The application of the cepstral method to signals derived from a C-type arrangement did not achieve the same discrimination as with a S-type arrangement. We used a simplified model to elucidate the poor performance in C-type signals. The bandwidth of signals obtained from S-type placement is wider than that from C-type. Narrower bandwidth decreases the importance of the more discriminative parts for both autoregressive (AR) and cepstral methods. The cepstral method is more sensitive to such variation, so the degradation in performance is more serious for the cepstral method. Second, the amplitude of C-type signal is lower than the S-type; therefore, the C-type signal is more sensitive to the disturbance of noise, especially in the high-frequency band. As high-frequency noise increases, the spectral difference between different EMG signals is gradually dominated by the low-frequency part, which is more informative. Thus, the performances of both methods are improved with increasing high-frequency noise. The improving rate of the AR method is faster than the cepstral method; therefore, its discriminative efficiency may exceed the cepstral method with C-type arrangement. Index Terms - Electrode arrangements, EMG signals, spectral distance measure.

A new technique for classifying patterns of movement via electromyographic (EMG) signals is presented. Two methods (conventional autoregressive (AR) coefficients and cepstral coefficients) for extracting features from EMG signals and three classification algorithms (Euclidean Distance Measure (EDM), Weighted Distance Measure (WDM), and Maximum Likelihood Method (MLM)) for discriminating signals representative of broad classes of movements are described and compared. These three classifiers are derived from Bayes classifier with some assumptions, the relationship among them is discussed. The conventional MLM is modified to avoid heavy matrix inversion. Six able-bodied subjects with two pairs of surface electrodes located on bilateral sternocleidomastoid and upper trapezius muscles were studied in the experiment. The EMG signals of 20 repetitions of 10 motions were analyzed for each subject. Experimental results showed that mean recognition rate of the cepstral coefficients was at least 5% superior to that of the AR coefficients. The improvement achieved by the cepstral method was statistically significant for all the three classifiers. Reasons for the superiority of cepstral features were investigated from the feature space and frequency domain, respectively. The cepstral coefficients owned better cluster separability in feature space and they emphasized the more informative part in the frequency domain. The discrimination rate of the MLM was the highest among three classifiers. Incorporation of the cepstral features with the MLM could reduce the misclassification rate by 10.6% when compared with the combination of AR coefficients and EDM. Proper choice of five of ten motions could further raise the recognition rate to more than 95%.

A detailed analysis of optical coherent phase diversity single-filtered and dual-filtered FSK receivers corrupted by shot and phase noise is presented. With delay and cross-product detection, the effect of various parameters, including bandwidths of filters, delay time, frequency deviation and noises, are investigated. The tolerance of phase noise is quite large, when small time delay in the demodulator and appropriately large frequency deviation is selected. It is also shown that there exists an optimal bandwidth for the first filter in the dual-filtered FSK receiver. For a total linewidth equal to half of the bit rate, the power penalty incurred (at BER = [10.sup.-9]) is 1.92 dB when the modulation index is 4, provided that an optimal filter bandwidth and a frequency deviation-delay product of 0.25 are used.

Byline: Yu-Cheng Fan, Hen-Wai Tsao In this paper, we propose a dual pyramid watermarking method for JPEG-2000. The robust pyramid watermark is embedded into the host image by changing the wavelet coefficients according to the characteristics of wavelet transformation, regions of interest, and Embedded Block Coding with Optimised Truncation (EBCOT) to protect copyrights. The fragile pyramid watermark records the characteristics of the coefficients in the high-high band to detect slight changes and authenticate the owner of the images. Experimental results show that the proposed technique successfully survives JPEG-2000 compression, image cropping, pepper noise, scaling and rotation and can detect modification of the host image.