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# Frequency Generator

IP.com Disclosure Number: IPCOM000079956D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 34K

IBM

Peard, M: AUTHOR

## Abstract

Shown in Fig. 1A is a waveform for which it can be demonstrated that it does not present any third harmonic. Considering a whole period, this pattern is in an UP level from 0 to alpha 1 = 70 degrees, from alpha 2 = 90 degrees to alpha 3 = 110 degrees, from alpha 4 = 250 degrees to alpha 5 = 270 degrees and from alpha 6 = 290 degrees to 360 degrees, and it is at a DOWN level from alpha 1 - 70 degrees to alpha 2 = 90 degrees, from alpha 3 - 110 degrees to alpha 4 = 250 degrees and from alpha 5 = 270 degrees to alpha 6 = 290 degrees.

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Frequency Generator

Shown in Fig. 1A is a waveform for which it can be demonstrated that it does not present any third harmonic. Considering a whole period, this pattern is in an UP level from 0 to alpha 1 = 70 degrees, from alpha 2 = 90 degrees to alpha 3 = 110 degrees, from alpha 4 = 250 degrees to alpha 5 = 270 degrees and from alpha 6 = 290 degrees to 360 degrees, and it is at a DOWN level from alpha 1 - 70 degrees to alpha 2 = 90 degrees, from alpha 3 - 110 degrees to alpha 4 = 250 degrees and from alpha 5 = 270 degrees to alpha 6 = 290 degrees.

By filtering this pattern in a low-pass iilter, the obtained signal is a sinusoid having the frequency of the input pattern.

Thus a multifrequency generator is built to provide the conventional frequencies: 700 Hz, 900 Hz, 1100 Hz, 1300 Hz, 1500 Hz, 1700 Hz, 1900 Hz. By using this waveform for these particular frequencies, the fifth harmonics would range from 3500 Hz to 9500 Hz and a filter having a cutoff frequency equal to 3000 Hz is adequate.

The circuit shown in Fig. 1B permits generation of the pattern at the above frequencies. A clock provides a signal having a 600 ns period and this signal is used to generate the seven frequencies ranging from 700 to 900 Hz.

As can be seen from Fig. 1A, this pattern presenting symmetric and antisymmetric properties for generating the whole period, it is only necessary to consider the alpha 1 and alpha 2 values for the first quarter of the period.

For the various frequencies to be generated, the values...