Ut-Va Koc

Frequency Estimation in Intradyne Reception

We report on an optical intradyne receiver experiment with frequency estimation. Frequency estimation allows, if performed prior to block phase estimation or other phase recovery techniques, for a much higher frequency difference between transmit laser and local oscillator laser. We demonstrate the feasibility of our approach in a 20-Gb/s quadrature phase-shift keying experiment

A 5-b 10-GSample/s a/D converter for 10-gb/s optical receivers

A 5-bit 10-Gsample/s A/D converter (ADC) is fabricated in a SiGe BiCMOS process to digitally compensate the signal distortion in a 10-Gb/s optical receiver. A fully differential, flash-type ADC has a wideband track-and-hold amplifier to mitigate the timing skew, followed by high-speed comparators with very small metastability error. It achieves a 4.1 effective bits at low input frequencies and 2.8 effective bits at full-scale 4.9-GHz input signal at 10-Gsample/s.

DCT-based motion estimation

We propose novel discrete cosine transform (DCT) pseudophase techniques to estimate shift/delay between two one-dimensional(1-D) signals directly from their DCT coefficients by computing the pseudophase shift hidden in DCT and then employing the sinusoidal orthogonal principles, applicable to signal delay estimation remote sensing. Under the two-dimensional (2-D) translational motion model, we further extend the pseudophase techniques to the DCT-based motion estimation (DXT-ME) algorithm for 2-D signals/images. The DXT-ME algorithm has certain advantages over the commonly used full search block-matching approach (BKM-ME) for application to video coding despite certain limitations. In addition to its robustness in a noisy environment and low computational complexity, O(M(2)) for an MxM search range in comparison to the O(N(2) . M(2)) complexity of BKM-ME for an NxN block, its ability to estimate motion completely in DCT domain makes possible the fully DCT-based motion-compensated video coder structure, which has only one major component in the feedback loop instead of three as in the conventional hybrid video coder design, and thus results in a higher system throughput. Furthermore, combination of the DCT and motion estimation units can provide space for further optimization of the overall coder. In addition, the DXT-ME algorithm has solely highly parallel local operations and this property makes feasible parallel implementation suitable for very large scale integration (VLSI) design. Simulation on a number of video sequences is presented with comparison to BKM-ME and other fast block search algorithms for video coding applications even though DXT-ME is completely different from any block search algorithms.

12.5-GHz optically sampled interference-based photonic arbitrary waveform Generator

This work presents an actively sampled photonic arbitrary waveform generator based on differential lithium-niobate electrooptic modulators. Ultralow timing jitter 1550-nm mode-locked laser time samples three serially connected Mach-Zehnder modulators, which are driven by six 12.5-Gb/s signals. This equivalent of photonic digital-to-analog converter allows for synthesis of high-quality arbitrary waveforms (>30-dB spurious-free dynamic range) over Nyquist bandwidth without loss of performance.

Discrete-cosine/sine-transform based motion estimation

A new motion estimation scheme, discrete-cosine/sine-transform based motion estimation (DXT-ME) utilizing the principle of orthogonality of cosine and sine functions to estimate, in the transform domain, displacements from the motion information contained in the pseudo-phases of the images of moving objects, is proposed. The computational complexity of this method is only O(N2)+Odct for an image of size N×N in comparison to O(N4), the complexity of the full search block matching approach, where Odct is the complexity of DCT/DST coding. Furthermore, incorporation of DXT-ME with DCT-based video standards achieves further savings of computations and makes symmetric codecs feasible. Unlike the pel-recursive algorithm, this scheme is not susceptible to noise. For complicated scenery or large moving objects, simple preprocessing is performed on images to extract the features of moving objects before applying DXT-ME. Simulation on some video sequences is presented to compare this scheme with the block matching method.

A Single-Chip 125-MHz to 32-GHz Signal Source in 0.18-

We present a 4.4-mm2 single-chip synthesized signal source with 125 MHz to 32 GHz continuous frequency coverage with a minimum frequency step smaller than 10 Hz. The chip is fabricated in a 0.18-μm SiGe BiCMOS 1P6M technology. A core fractional-N synthesizer using a 20-MHz reference frequency has four LC-VCOs and a 4- to 8-GHz synthesizable range. Post-synthesis blocks extend the frequency coverage up to 32 GHz and down to 125 MHz through frequency multiplication and division. In different operation modes, the chip, including a balanced 50-ohm load driver, consumes from 284 to 498 mW. The phase noise performance achieves -117.6 dBc/Hz at 1-MHz offset from a 6-GHz output frequency and -83 dBc/Hz in-band noise. The integrated phase noise is -28 dBc and the absolute jitter is 1.05 psRMS at 6-GHz output. The jitter is maintained nearly constant (between 0.9 and 1.2 psRMS) across the whole output frequency range.

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Conventional coherent detection attempts to synchronize local lasers with transmit lasers indiscriminately without considering individual noise contributors. Handling each contributor properly, we proposed a novel approach for quadrature-phase-shift-keying to enable realization of coherent communication without need of synchronization

m SiGe BiCMOS

Inter-pixel interpolation is required for most subpixel motion estimation schemes but it undesirably increases the overall complexity and data flow and deteriorates the estimation accuracy. We develop DCT-based techniques to estimate subpel motion at different desired levels of accuracy in the DCT domain without interpolation by establishing subpel sinusoidal orthogonal principles and showing that subpixel motion information is preserved in the DCT of a shifted signal under some conditions in the form of pseudo phases. Though applicable to other areas, the resulting algorithms from these techniques for video coding are flexible and scalable with very low complexity O(N/sup 2/) compared to O(N/sup 4/) for block matching methods. Importantly, DCT-based methods enable simplification of the heavily loaded feedback loop of conventional hybrid video coder design, resulting in a high-throughput, low-complexity fully DCT-based coder. Finally, simulation results show a comparable performance of the proposed algorithms with block matching methods.

Digital coherent quadrature phase-shift-keying (QPSK)

Background and standards: video communications motion-compensated DCT video coding video coding standards. Algorithms: DCT-based motion estimation interpolation-free subpixel motion estimation DCT-based motion compensation schemes MPEG-4 and content-based video coding. Architectures and implementation: dual generation of DCT and DST efficient design of video coding engine low-power and high-performance design. Applications: end-to-end video over IP delivery.

DCT-based subpixel motion estimation

This paper presents the behavioral simulation of a fourth-order multi-bit continuous-time bandpass /spl Delta/-/spl Sigma/ analog-to-digital converter (ADC) for direct radio frequency (RF) conversion in multi-band 3G base stations. With a 2.1 GHz carrier frequency, the conventional method requires a sampling frequency greater than 8 GHz. To overcome the design complexity, jitter issue, and high power consumption anticipated for a design at such a high sampling-rate, we propose a new mirrored-image sampling technique to achieve targeted ADC performance at a much lower sampling rate. Detailed analysis of stability and signal-to-noise ratio (SNR) find the optimum DAC topology and design parameters. With an RZ33%-DAC, the ADC is capable of digitizing a 2.1 GHz RF signal with a 20 MHz band at 2.8 Gsamples/sec, and achieving a 87 dB SNR.