A presentation about Analog and Digital Signals and how to convert between them.

1. Signal: A signal is information converted into electrical form and is
suitable for transmission. It is a single-valued function of time that
conveys information in the form of voice, music, picture, etc. Signal
is of two types: Analog signal and Digital signal.
1- Analog signal is continuous variation of voltage or current,
such as a sine wave.
Some examples of analog signal are sound produced
by vibrating a tuning fork ,speech and Heartbeat signals.
2- Digital signal:
Those signal, which has discrete step-wise variations or pulses of
voltage or current, is called digital signal.
Digital signal is in the form of rectangular waves.
the transistor will have two-state operations i.e.,
output is either low or high.
Since digital operation has only two states (i.e., ON or OFF)

4. Digital communication systems have several advantages over analog
systems:
1.High-Quality Information: Digital systems offer superior information
quality in the digital era.
2.Efficiency and Reliability: Digital communication devices operate more
efficiently, stably, and reliably than analog counterparts. The impact of noise
is less due to error correction capabilities.
3.Multiplexing: Digital systems can integrate multiple signals on the same
transmission channel using digital transmission techniques.
4.Data Encryption: Digital systems use data encryption, enhancing security
and protection.
Despite these benefits, digital systems have drawbacks, including
complexity and the need for a broader bandwidth compared to analog

6. Parity is an error-detection mechanism in digital communication.
In even or odd parity, a single binary parity bit is added to a data set, creating a predetermined total count of
1s. If an error occurs during transmission or storage, it alters the parity bit, signaling a discrepancy. For
example, in even parity, the parity bit is adjusted to maintain an even count. The receiving system checks
the parity, and a mismatch indicates an error. Parity provides a simple and effective means to detect single-
bit errors, enhancing the reliability of data transfer and storage in digital systems.
Then, following cases are possible-
•If total number of 1’s is even and even parity is used, then receiver
assumes that no error occurred.
•If total number of 1’s is even and odd parity is used, then receiver
assumes that error occurred.
•If total number of 1’s is odd and odd parity is used, then receiver
assumes that no error occurred.
•If total number of 1’s is odd and even parity is used, then receiver
assumes that error occurred.

7. At Sender Side-
•Total number of 1’s in the data unit is counted.
•Total number of 1’s in the data unit = 3.
•Clearly, even parity is used and total number of 1’s is odd.
•So, parity bit = 1 is added to the data unit to make total number of 1’s
even.
•Then, the code word 10010011 is transmitted to the receiver.
Consider the data unit to be transmitted is 1001001
and even parity is used.

9. - An analog to digital converter (ADC) can be modeled as two processes: sampling, quantization and
encoding.
- Sampling converts a time-varying voltage signal into a discrete-time signal, a sequence of real
numbers.
Analog-to-digital converter
- Quantization replaces each real number with an approximation from a finite set of discrete values. Most
commonly, these discrete values are represented as fixed-point words.
- Encoding is the process of converting data from one form to another. There are several types
of encoding, including image encoding, audio and video encoding, and character encoding.

10. Nyquist's theorem states that a periodic signal
must be sampled at more than twice the highest
frequency component of the signal.
Frequency of sampler >2xmax.frequency of signal

11. - Quantization – process of assigning the analog signal samples to a pre-determined discrete level.
- The number of quantization levels, L depends on the number of bits per sample, n where:
Where:
L = number of quantization level
n = number of bits in binary to represent the value of the samples
n
L 2


12. Coding:
• The process of representing quantized values digitally is called coding
• The analog signal is represented digitally by the following series of binary
numbers: 10, 11, 11, 11, 10, 01, 00, 01, and 10.