Delta Modulation
Delta modulation (DM) is a type of analog-to-digital conversion technique that samples an analog signal at a constant rate and quantizes the difference between the sampled value and the previous value. This quantized difference, also known as the delta or step size, is then encoded and transmitted to the receiver.
At the receiver side, the encoded delta signal is decoded and added to the previous output to obtain the current output. Due to the use of only one bit for encoding, DM results in a simple and low-cost implementation, but it has some drawbacks such as quantization noise and signal distortion.
To overcome these limitations, variations of DM such as adaptive delta modulation (ADM) and differential pulse-code modulation (DPCM) have been developed. ADM adjusts the step size according to the input signal level, while DPCM encodes the difference between the input signal and a predicted value. These methods improve the performance of DM, making it more suitable for applications such as audio and video compression.
Delta modulation is a form of analog-to-digital conversion technique used in communication systems. It is commonly used for transmitting analog signals in a digital format over a communication channel. Here is a step-by-step explanation of delta modulation:
1. Sampling: The input analog signal is divided into fixed intervals of time, known as sampling intervals. At each interval, the amplitude of the analog signal is sampled or measured.
2. Quantization: The sampled analog signal is then quantized into discrete levels. The aim of quantization is to approximate the continuous analog signal with a limited number of discrete values. The number of quantization levels determines the resolution and accuracy of the digital representation.
3. Delta-Sigma Modulation: In delta modulation, the quantization levels represent the difference between the current sample and the previous sample, known as the delta. Delta-sigma modulation encodes the delta value into a binary sequence. A 1-bit code is used to encode whether the current sample is higher or lower than the previous sample.
4. Encoding: The binary sequence generated by delta-sigma modulation is encoded using techniques like Pulse Code Modulation (PCM) or Differential Pulse Code Modulation (DPCM). PCM converts the binary sequence into a series of binary words, representing the quantized values. DPCM, on the other hand, encodes the difference between successive samples, reducing the amount of data needed for transmission.
5. Transmission: The encoded digital signal is transmitted over a communication channel, which can be wired or wireless. The digital signal can be transmitted using various modulation techniques, such as amplitude shift keying (ASK), frequency shift keying (FSK), or phase shift keying (PSK), depending on the type of channel.
6. Demodulation and Decoding: At the receiving end, the digital signal is demodulated back to its original format using the appropriate demodulation technique. This process involves extracting the encoded binary sequence from the received signal.
7. Reconstruction: The binary sequence is then decoded to recover the original quantized samples and delta values. By reconstructing these values and using an interpolation technique, an approximate version of the original analog signal is obtained.
Overall, delta modulation provides a simple and efficient way to convert analog signals into a digital format for transmission and subsequent reconstruction at the receiving end. It is commonly used in applications like voice communication, video coding, and digitizing instrumentation signals.