The dissertation is devoted to solving the actual scientific and technical problem of developing and researching the principles of construction and creation of recurrent logarithmic analogue-to-digital converters for improving metrological characteristics.
Conversion in modern LDCs on switched capacitors is carried out with a fixed or variable base of the logarithm. Among the multitude of such LDCs, in particular, serial, bit-by-bit, parallel, with pulse feedback and recurrent, at the moment the least studied are recurrent.
The introduction substantiates the relevance of the topic of dissertation research, formulates the purpose of the research and the scientific and technical tasks necessary for its achievement, shows the connection of the research with scientific programs and topics, indicates the scientific novelty of the obtained results, their practical value and the personal contribution of the recipient.
In the first chapter, an analysis of the current state of logarithmic analog-to-digital converters is carried out. The classification of logarithmic analogue-to-digital converters has been made, and the properties of integral logarithmic analogue-to-digital converters have been analyzed, when developing integral LACs, preference is given to using the same structural blocks in their converters. Therefore, most integrated LDCs are pipelined, providing an average accuracy equivalent to 8 binary digits.
Prospects for the development of integral logarithmic analog-to-digital converters are considered.
In the second chapter, the general principles of the construction of recurrent LDCs are developed, the implementation of recurrent LDCs with a constant and variable in the transformation process with a logarithm base is considered and their generalized structural diagrams are created, an assessment of accuracy and speed is given depending on the logarithm base to simplify the design and practical implementation of converters with given parameters.
In the third chapter, physical models of recurrent LDCs are developed, sources of errors are established, mathematical models of recurrent LDCs errors are created, errors are estimated taking into account the parameters of modern components and it is shown that the dominant error is the error due to the influence of parasitic interelectrode capacitances.
Mathematical models of the errors of recurrent LCPs are proposed, which make it possible to analytically assess the accuracy of LCPs.
Errors due to the influence of parasitic capacitances of the LDC increase in absolute values along with the increase in the number of conversion cycles. The biggest increase in errors is in the first 2-3 beats of the conversion, and after 10 beats, the increases are negligible.
Errors due to the influence of parasitic capacitances of the LACP decrease in absolute values with an increase in the capacity of the storage capacitors (C1 and C2) of the capacitor cell and a decrease in the number of LACP bits. Errors from parasitic charge transfer are positive, and errors from control voltage transfer are negative, as a result of which their partial mutual compensation takes place in the resulting error, which becomes positive.
In the fourth chapter, the physical simulation of the developed recurrent LACP with a constant and a variable base of the logarithm is carried out. The principle schemes of recurrent LDCs are presented, during the development of which special attention was paid to their prospects for manufacturing using the technology of integrated circuits. New technical solutions for recurrent LDCs with both a constant and a variable logarithm base are proposed. What is new is the implementation of the reference voltage divider from the same L-shaped blocks of two resistors. The reference voltage divider for recurrent LDCs of series conversion with a constant base is simpler and contains only 8 blocks. To implement the reference voltage divider for recurrent LDCs of bit-by-bit conversion with a variable base, the number of blocks increases significantly, and for an 8-bit LDC, 64 of them are needed. The conducted studies confirmed that to ensure an increase in the accuracy of recurrent LDCs above their nominal bit rate, it is necessary to choose the base of the logarithm for LDCs of this higher bit rate.
