In this paper, the problem of carrier synchronization for coded signals in burst communications is addressed. Low SNR, phase jitter, and relatively large initial frequency offset are assumed. A new concept is introduced: synchronization using an array of Kalman trackers, where each tracker is associated with different initial conditions. Based on this concept, an improved joint data detection and carrier synchronization scheme for trellis coded signals is proposed. The proposed scheme uses an array of decision directed Kalman trackers, each initialized with different initial conditions and updated based on tentative decisions from the Viterbi decoder. This scheme reduces drastically the number of cycle slips and hang-ups encountered in the classical PLL and improves significantly the receiver's BER performance. The implementation complexity is relatively low and no special hardware is required.
This work presents a cascaded fourth-order ΣΔ modulator for multimode baseband-frequency (BF) receiver. Each stage of the proposed modulator contains a resonator that introduces a pair of conjugate zeros to minimize the in-band noise, and furthermore provides optimum noise transfer functions for multimode receiver. The proposed modulator also features low distortion, swing suppression, and high dynamic range (DR). As the simulation results, the DR of our multimode cascaded ΣΔ modulator is approximately 80dB for four wireless standards.
It is known that the capacitance mismatch affects the nonlinearity of pipeline analog-to-digital converters (ADCs) and that larger capacitances tend to have a smaller mismatch. On the other hand, small capacitances are desirable because they reduce the current consumption. Therefore, to achieve a low-power, high-resolution ADC, it is necessary to perform capacitance mismatch evaluation and determine the appropriate capacitance. In this letter, a method for capacitance-mismatch measurement and the experimental results are described. The measurement results show that the mismatch is sufficiently small at the capacitance determined based on the noise requirement for 0.13-µm CMOS ADCs.
We demonstrate simultaneous optical modulation by frequency shift keying (FSK) and intensity modulation (IM) using a newly developed high-speed FSK modulator, for optical packet systems where payload and label signals are, respectively, in IM and FSK format. The modulator consists of four optical phase modulators, with traveling-wave electrodes to obtain high-speed frequency switching and large frequency deviation in FSK modulation.