Performance limitations in a programmable digitally tuned CMOS OTA-C 2nd-order bandpass filter architecture /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | A digitally programmable digitally tuned analog filter architecture based on an analog continuous-time CMOS OTA-C (operational transconductance amplifier and capacitor) was developed and characterized with emphasis on the factors that inherently limit the performance of filters utilizing this architecture. This versatile architecture is tuned using a microprocessor, giving this architecture the capability of conducting in-field self tests and operating at high Qs and high frequencies. The filter architecture consists of three basic functional blocks: a controllable filter, a Performance Measurement System which characterizes the filter's performance, and a tuning algorithm which evaluates the filter's performance and appropriately adjusts the control parameters. Unlike the master/slave analog tuned filter structures, this architecture uses direct performance measurements as the basis for the tune which allow independence from matching analog components and the use of filters that do not behave ideally. Limitations of this architecture include that it is expensive since it is not monolithic and requires extensive support circuitry and that tuning times are lengthy. The controllable filter is designed to give independent control of filter parameters for a 2nd-order bandpass filter. However, inherent coupling of the control mechanisms to the controlled filter parameters is a major performance limitation of this architecture. The practical range of center frequencies considering process variation is 3.0kHz to 1.8MHz with a resolution of [plus or minus]0.25%, while the practical range of filter Qs is 0.5 to 20 with a resolution of [plus or minus]0.5%. Over-ordering of the transfer function which reduces the resolution and range of the control mechanisms and produces gaps in the control range has been modelled. The effect of the nonlinear distortion of the OTA has been incorporated into an amplitude-dependent nonideal model of the filter's performance. The Performance Measurement System and Timing Algorithm are relatively robust with the primary performance limitations being in the hardware and not the measurement and tuning algorithms. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Electrical engineering." |
| Physical Description: | 2 volumes : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |