Analysis and Design of a Phase Interpolator for Clock and Data Recovery

In this paper,a detailed analysis of a phase interpolator for clock recovery is presented. A mathematical model is setup for the phase interpolator and we perform a precise analysis using this model. The result shows that the output amplitude and linearity of phase interpolator is primarily related to the difference between the two input phases. A new encoding pattern is given to solve this problem. Analysis in the circuit domain was also undertaken. The simulation results show that the relation between RC time-constant and time difference of input clocks affects the linearity of the phase interpolator. To alleviate this undesired effect, two adjustable-RC buffers are added at the input of the PI. Finally,a 90nm CMOS phase interpolator,which can work in the frequency from 1GHz to 5GHz,is proposed. The power dissipation of the phase interpolator is lmW with a 1.2V power supply. Experiment results show that the phase interpolator has a monotone output phase and good linearity.

2.5Gb/s/ch 0.18μm CMOS Data Recovery Circuit

A 2.5Gb/s/ch data recovery （DR） circuit is designed for an SFI-5 interface. To make the parallel data bit-synchronization and reduce the bit error rate （BER） ,a delay locked loop （DLL） is used to place the center of the data eye exactly at the rising edge of the data-sampling clock. A single channel DR circuit was fabricated in TSMC＇s standard 0. 18μm CMOS process. The chip area is 0. 46mm^2. With a 2^32 - 1 pseudorandom bit sequence （PRBS） input,the RMS jitter of the recovered 2.5Gb/s data is 3.3ps. The sensitivity of the single channel DR is less than 20mV with 10-12 BER.

Realization of 40 GHz Short Time Windows and Their Applications in High Speed Optical Time Division Multiplexing Systems

Optical Time Division Multiplexing （OTDM） is known to be capable of transmitting single channel high bit rate data stream with low speed electro-optical components. A cost-effective, compact and stable short time window with low insert loss, low phase noise, low timing-jitter and high speed performance is essential for ultra-high speed OTDM systems using phase and amplitude modulation formats. In this paper, we review three promising methods to obtain 40 GHz short time window including Electro-Absorption Modulator （EAM）, Dual-Parallel Mach-Zehnder Modulator （DPMZM） and Fiber Loop-Polarization Modulator （FL-PolM）. Sub-picosecond short pulse source generation, optical time division denlaltiplexing and clock recovery are realized respectively by using the short time window based on the three methods. By using DPMZM based pulse source and EAM based Clock Recovery （CR） and dermltiplexer, error free transmission of 640 Goit/s （160 Gbaud/s Pol-Mux DQPSK） single channel signal over 400 km single mode fiber is proven to be experimentally successful.

High efficiency spreading spectrum modulation using double orthogonal complex sequences

This paper presents a novel scheme of high efficiency spreading spectrum modulation using double orthogonal complex sequences （DoCS）. In this scheme, input data bit-stream is split into many groups with length M. Each group is then mapped into a word of width M and then utihzed to select one sequence from 2u-2 DoCS sequences each with length L. After that, the selected sequence is modulated on carrier in quadrature phase shift keying （QPSK） mode. In addition, a new method named forward phase correction （FPC） is put forward for carrier recovery. Theoretical analysis and bit-error-ratio（BER） experiment results indicate that the proposed scheme has better performance than the conventional direct sequence spread spectrum（DSSS） scheme both in bandwidth efficiency and processing gain of the receiver.

基于周期阵列抽样孔的非迭代实时相干衍射成像

提出了一种从远场衍射强度图样实现实时相干衍射成像的迭代方法.该方法利用特殊设的周期正方阵列抽样针孔对待测物体的涅耳衍射场的波前进行抽样,用CCD录其远场衍射图样.算机中对其处理,可以直接从远场衍射图样的逆里叶变换中提取物波的抽样振幅数据,利用标量衍射理论对物体重现.因为该方法只需要对一幅远场衍射图样进行测量,避免了迭代算法,而且从理论上不需要透镜,它可以较广的波长范围内实现实时相干衍射成像.

Phase problems in optical imaging

Because the phase contains more information about the field compared to the amplitude, measurement of the phase is encountered in many branches of modern science and engineering. Direct measurement of the phase is difficult in the visible regime of the electromagnetic wave. One must employ computational techniques to calculate the phase from the captured intensity. In this paper, we provide a review of our recent work on iterative phase retrieval techniques and their applications in optical imaging.

Robustness properties of dimensionality reduction with Gaussian random matrices

In this paper, motivated by the results in compressive phase retrieval, we study the robustness properties of dimensionality reduction with Gaussian random matrices having arbitrarily erased rows. We first study the robustness property against erasure for the almost norm preservation property of Gaussian random matrices by obtaining the optimal estimate of the erasure ratio for a small given norm distortion rate. As a consequence, we establish the robustness property of Johnson-Lindenstrauss lemma and the robustness property of restricted isometry property with corruption for Gaussian random matrices. Secondly, we obtain a sharp estimate for the optimal lower and upper bounds of norm distortion rates of Gaussian random matrices under a given erasure ratio. This allows us to establish the strong restricted isometry property with the almost optimal restricted isometry property(RIP) constants, which plays a central role in the study of phaseless compressed sensing. As a byproduct of our results, we also establish the robustness property of Gaussian random finite frames under erasure.