A Fourier Synthesis Character Generator

The authors (from the Lincoln Laboratory of MIT) detail a demonstration unit for generating the Arabic octal numerals 0 through 7, synthesising the deflection waveforms for each character from artificially generated sine and cosine terms of 5 harmonic frequencies, with a reference frequency of 30 kHz. As the X and Y deflection waveforms required to scribe each unique character are synthesized from five harmonics having a fundamental frequency of 20 kHz, an amplitude-stable reference of these 5 harmonic frequencies, both sine and cosine terms, plus the inverses, must the generated. Ripple counter U4 and quad NAND gate U5 form in combination a divide-by-5 counter, dividing the 800 kHz reference to 160 kHz, which is divided further again by the first three stages of ripple counter U6, which produces in succession the 4th, 2nd and 1st (fundamental) harmonic reference square waves of 80 kHz, 40 kHz and 20 kHz.

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