| Summary: | 碩士 === 萬能科技大學 === 工程科技研究所 === 98 === This article is the study of design and implementation of adaptive delta modulation. Reducing the slope overload and granular noise of wideband signal coding is our main purpose, it can also increase the bandwidth of encoding signal and suitable application for video signal. In signal processings ,we combined the basic architecture of digital type delta modulation with decision logic circuit and +1/-1/+0 selection accumulation circuit to change adaptively delta quantitiesΔ. The algorithm of decision logic is when three consecutive 1s or 0s of digital encoded signal occur.Δ changes 2Δ, otherwise Δ unchange. This treatment is simple, wideband and practical.
The Multisim software developed by National Instruments is used in our circuit design. We tooth the values of 5MHz bandwidth of video for circuit simulation and confirm the correctness in our digital circuit design. The total harmonic distortion is less than 2% when we used the parameters of 5MHz video bandwidth and 40MHz sampling frequency. It can satisfy the requirement for high quality video transmission.
Finally, the adaptive delta modulator was implemented in 5cm X 10cm PCB and using 14 IC components through circuit layout software by Design6 developed Altium. This measurement results are consistent with simulation results. The study is verified the availability of the modem for digital video transmission and having practical value.
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