SLAAEH6 September   2024 TAA5212 , TAA5412-Q1 , TAC5111 , TAC5111-Q1 , TAC5112 , TAC5211 , TAC5212 , TAC5212-Q1 , TAC5311-Q1 , TAC5312-Q1 , TAC5411-Q1 , TAC5412-Q1 , TAD5112 , TAD5112-Q1 , TAD5212 , TAD5212-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Infinite Impulse Response Filters
    1. 2.1 Digital Biquad Filter
  6. 3TAC5x1x and TAC5x1x-Q1 Digital Biquad Filters
    1. 3.1 Filter Design using PurePath™ Console
      1. 3.1.1 Example of Programming Biquad Filters Using PurePath™ Console
    2. 3.2 Generating Coefficients N0, N1, N2, D1, D2 using a Digital Filter Design Package
    3. 3.3 Avoiding Overflow Conditions
    4. 3.4 Biquad Filter Allocation on Recording Channel
    5. 3.5 Biquad Filter Allocation on Playback Channel
    6. 3.6 Biquad Filter Programming Example on the TAC5x1x
  7. 4Typical Audio Applications of Biquad Filters
    1. 4.1 Parametric Equalizers
    2. 4.2 Crossover Networks
    3. 4.3 Voice Boost
    4. 4.4 Bass Boost
    5. 4.5 Removing 50Hz–60Hz Hum With Notch Filters
  8. 5Summary
  9. 6References

2 Infinite Impulse Response Filters

Equation 1 specifies the transfer function of an infinite impulse (IIR) digital filter.

Equation 1. H ( z )   =   b 0   +   b 1 z - 1   +   b 2 z - 2   +   . . .   +   b M z - M 1   +   a 1 z - 1   +   a 2 z - 2   +   . . .   +   a N z - N

When the coefficients of this transfer function are quantized for fixed point implementations, the resulting errors due to quantization and the recursive nature of the filter can significantly alter the desired filter characteristics and lead to instability. Partitioning this transfer function into a set of cascaded lower-order filters reduces the sensitivity to coefficient quantization. Cascaded Biquad IIR filter implementations have been proven to be effective in minimizing these effects.