Alternative low-noise realizations for narrow-band recursive digital filters

Alternatives to Munson and Liu´s structures [1] are given, which also realize a second-order section having both poles and zeros, with low sensitivity and roundoff noise. Instead of realizing zeros separately from poles, zeros are combined with poles in poles preceding zeros form. An illustration is worked out for comparison, and it is shown that such a realization could have better signal-to-noise ratio without any additional hardware.