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Analog/To/Digital Converter

IP.com Disclosure Number: IPCOM000086809D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Tseng, SC: AUTHOR

Abstract

An analog-to-digital converter is illustrated in which the input signal is converted into a variable frequency signal, and multiresonant filters, reference oscillators and mixers are employed to factor out the equivalent weighted binary values from the input signal to produce the component binary outputs.

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Analog/To/Digital Converter

An analog-to-digital converter is illustrated in which the input signal is converted into a variable frequency signal, and multiresonant filters, reference oscillators and mixers are employed to factor out the equivalent weighted binary values from the input signal to produce the component binary outputs.

ln the figure, the analog input 10, in the form of a variable voltage signal, is converted into a variable frequency signal by means of a voltage controlled oscillator 12 which, by way of example, produces signals in the range of 1K to 16K, where K is a constant (to be ignored in the subsequent explanation).

The variable frequency signal is connected to the multiresonant filter F-8, and to the filters F-4, F-2 and F-1 via the OR amplifiers 0-4, 0-2 and 0-1, respectively. The filter F-8 is resonant to the frequencies f9 to f16, which it will pass to resistor R-8. Similarly, filter F-4 has a low impedance to signals having a frequency of f5, f6, f7 and f8. Filter F-2 passes signals of frequency f3 and f4, while filter F-1 passes signals of frequency f2 only.

Oscillator 1C is a reference oscillator having a frequency of f8, which is successively halved to f4 and f2 by dividers 16 and 18. The outputs of each of the filters F-8, F-4 and F-2 is connected to a corresponding mixer M-8, M-4 or M- 2 which yield the sum and difference of the two signals. Only the difference signal is exploited in the present apparatus. The second input to each of the mixers originates with corresponding reference frequency generator 14, 16 or 18.

The outputs from each of the mixers M-8, M-4 and M-2 are connected to all of the lower order "OR" amplifiers 0-4, 0-2 and 0-1, respectively.

The table illustrates the principle of the conversion. The zero analog input level is converted to a frequency of f1. This frequency will experience a high impedance at filter F-8, and no signal will appear across R-8 and no output at X8. The f1 signal will similarly be applied via the "OR" amplifiers 0-4, 0-2 and 0-1 to the filters F-4, F-2 and F-1, respectively, all of which exhibit a high impedance to the frequency f1. Consequently, there will also be no outputs at X4, X2 or X1, as would be expected for a zero input.

If an analog input of 13 occurs, the oscillator 12 will yield a frequency of f14, which will pass filter F-8 to produce an X8 output and an input frequency of f14 to...