Marek Kropidłowski

Switched-current technique for video compression and quantization

Portable consumer products need low-cost, low-power chips for realization of signal processing and image compression functions. In this paper a modification of such a chip for a digital video camera is presented. The chip contains an image sensing array composed of photodiodes, a two-dimensional DCT processor and an entropy coding section. The processor is designed in a switched-current (SI) technique and contains current mirrors and memory cells. In order to examine these elementary cells, an experimental chip in AMS 0.8 /spl mu/m technology was fabricated.

SI-Studio, a layout generator of current mode circuits

The paper presents automatic layout generation of analog current mode circuits.Chip area, power consumption and speed operation is controlled.An experimental chip was fabricated in CMOS technology.The chip was tested in the environment based on FPGA.Measurement results of realized filter pairs and filter banks are presented. This work is the answer to the so far unsolved problem of generation of integrated circuits topography for current mode circuits. Synthesis methods corresponding to already existing digital methods are proposed. Among others - the following has been shown: a digital adaptation of the row strategy for analog cell design, as well as performance control of the circuits with respect to chip area, power consumption and speed operation. The proposed algorithms are integrated with the already-existing tools for automatic layout generation of analog circuits with behavioral description at the beginning. At each stage of the synthesis process - an architecture description in the VHDL-AMS language was used, which so far has been not useful to synthesize. On the basis of the elaborated expert system, layouts of a filter pair and a filter bank were generated. The circuits were fabricated in TSMC 0.18 µ m CMOS technology and results of measurements are presented. The elaborated approach makes a contribution to the realization of current mode circuits with complexity not achievable up to now.

Design automation of a lossless multiport network and its application to image filtering

The paper presents expert tools which are elaborated on the basis of synthesis method of lossless nonreciprocal multiport circuits, composed of gyrators and capacitors. The algorithms are written in C++ and the tools compose a user friendly environment for design automation of filters, filter pairs and filter banks. It is possible to design in this environment not only classical structures like Butterworth, Chebyshev, and Cauer (elliptic) filters. The lossless nonreciprocal prototype circuit allows to design more complex filters, including allpass sections necessary to improve filter phase characteristics. However, the most important possibility is to design multiport circuits, especially in the case of not fully determined filter specifications. On each stage of the design process VHDL-AMS is used to describe the circuits. The obtained prototype gyrator-capacitor circuit can be implemented in OTA-C, SC (switched-capacitor) or SI (switched-current) techniques to realize the filter in CMOS technology. In the paper SI technique is used for layout generation of an image filter in order to illustrate the elaborated synthesis algorithms and tools.

Switched-current implementation of two-dimensional DCT for image processing

Switched-current (SI) circuits are suitable to operate on the same chip with digital circuits in low-voltage supply. This property is very important for applications in portable devices like digital cameras. Switched-capacitor implementation of the two-dimensional (2D) discrete cosine transform (DCT) was reported in the literature. In this paper, the design method of a 2D DCT for SI implementation is presented. An experimental chip was fabricated in AMS CMOS 0.8 /spl mu/m technology. The results of testing are reported.

Switched-current filter design for image processing systems

The paper presents a design method of two-dimensional. (2-D) switched-current (SI) filters. Because of SI technique compatibility with the standard digital CMOS technology, it is very convenient to use such filters in image processing. Operation of a system containing 2-D filters in a pre-processing stage is described. Such a system can be implemented in portable one-chip devices like digital video cameras.

Low-voltage switched-current circuits for mixed signal systems

It is shown in the paper that switched-current (SI) circuits are able to operate on the same chip with digital circuits at low-voltage supply. This property is very important for applications in portable devices like digital cameras or cell phones. In this paper the properties of an SI memory cell are presented. Experimental chip in AMS CMOS 0.8 /spl mu/m technology was fabricated. The results of testing are reported.

EDA tools for designing ΣΔ modulators working in the currentmode

The article presents original tools for automating designing sigma-delta modulators working in the current mode. The solution makes it possible to optimize any modulator structure, to verify the compliance of the project with technological rules and to automate designing the layout of the circuit. The tools are compatible with popular design environments for CMOS circuits and with languages for describing circuit architectures. The proposed solution offers the designer the freedom of defining parameters expected of the modulator. The final result of the design process is a modulator topography obtained in a fully automated way and ready for fabrication. The effectiveness of the tools is demonstrated with an example of a modulator based on a current-to-frequency converter. The result of the design process was an SNDR coefficient equal to 76dB and the Walden’s FoM equal to 616fj/step for 20kHz bandwidth. Streszczenie. W artykule zaprezentowano autorskie narzędzia służące automatyzacji projektowania modulatorów sigma-delta pracujących w trybie prądowym. Przedstawione rozwiązanie umożliwia optymalizację dowolnej struktury modulatora, weryfikację zgodności projektu z regułami technologicznymi oraz automatyzację projektowania layoutu układu. Narzędzia zgodne są z popularnymi środowiskami projektowania układów CMOS oraz językami opisu architektury układów. Zaproponowane rozwiązanie oferuje projektantowi swobodę definiowania oczekiwanych parametrów modulatora, a finalnym rezultatem procesu projektowego jest w pełni automatycznie uzyskana topografia modulatora nadająca się do fabrykacji. Skuteczność narzędzi zademonstrownao na przykładzie modulatora bazującego na przetworniku prąd-częstotliwość. W wyniku procesu projektowego uzyskano współczynnik PSNR równy 76dB oraz Walden’s FoM równy 616fj/step dla pasma 20 kHz. (Narzędzia służące automatyzacji projektowania modulatorów sigma-delta).

Computer tools for switched-current filter design

The paper is devoted to design automation of switched-current (SI) filters. Three computer tools were elaborated recently by the authors. Two of them are useful at the stage of behavioral synthesis for symbolic analysis and design of a lossless prototype circuit. The third program, for layout generation of current mirrors, can be used for silicon assembly of an SI filter. In the presented synthesis method current mirrors are basic parameterized cells of such filters. The current mirrors are composed of transistors where width-to-length ratios of channels are determined at the behavioral synthesis stage of the filter.