Difference Between Mid Tread & Mid Rise Quantization


Mid-tread and mid-rise quantization are two types of analog-to-digital converter (ADC) quantization techniques. The main difference between these two techniques lies in the way the quantization levels are distributed.

In mid-tread quantization, the zero level is placed exactly in the middle of the quantization range, and the positive and negative levels are distributed symmetrically around it. In contrast, in mid-rise quantization, the zero level is not included in the quantization levels, and the positive and negative levels are distributed asymmetrically around it.

The following table summarizes the key differences between mid-tread and mid-rise quantization:

Feature Mid-tread quantization Mid-rise quantization
Zero level Placed in the middle of the quantization range Not included in the quantization levels
Positive levels Distributed symmetrically around the zero level Distributed asymmetrically around the midpoint between the lowest positive level and the zero level
Negative levels Distributed symmetrically around the zero level Distributed asymmetrically around the midpoint between the highest negative level and the zero level
Total number of quantization levels 2^n 2^n-1

Here, "n" represents the number of bits used in the ADC.

Mid-tread and mid-rise quantization are two commonly used quantization methods in signal processing. These methods differ in how they assign numerical values to the analog signal levels.

Feature Mid-tread Quantization Mid-rise Quantization
Threshold Level 0 (Vmax+Vmin)/2
Quantization Steps Even number Odd number
Quantization Error Distributed over ±Q/2 Distributed over 0 to ±Q/2
Effective Number of Bits (ENOB) Slightly higher than mid-rise Slightly lower than mid-tread
Usage Telephony General purpose

In mid-tread quantization, the threshold level is set to zero. The analog signal is then divided into a series of evenly spaced levels or quantization steps. The quantization error is distributed over the ±Q/2 range, where Q is the size of the quantization step. This method is commonly used in telephony and digital audio.

On the other hand, in mid-rise quantization, the threshold level is set to (Vmax+Vmin)/2, where Vmax and Vmin are the maximum and minimum voltage levels of the analog signal, respectively. The analog signal is divided into a series of odd numbered quantization steps. The quantization error is distributed over the range of 0 to ±Q/2. This method is commonly used in general-purpose applications such as data acquisition systems.

The effective number of bits (ENOB) is a measure of the quality of the quantization. In general, the ENOB is slightly higher in mid-rise quantization than in mid-tread quantization. However, the difference in ENOB is small and may not be significant in many applications.

In summary, the choice between mid-tread and mid-rise quantization depends on the specific requirements of the application. Mid-tread quantization is commonly used in telephony and digital audio, while mid-rise quantization is used in general-purpose applications such as data acquisition systems.

       

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