In the ideal cosine filter, sometimes referred to as a duo-binary filter, frequency response consists of a cosine function at low frequencies, and total attenuation at high frequencies.

In FilterSolutions, the passband frequency is set to the infinite attenuation point.

Nyquist's first criteria may be satisfied by the cosine filter when used in conjunction with bipolar signaling.

Mathematically, the frequency response of the cosine filter may be written as:

The ideal cosine filter frequency response is shown below:

Ideal Cosine Filter Frequency Response