I am trying to implement a cardioid pattern with two microphones.
I was reading this paper titled "Digital Filter Array Optimization for Directivity Pattern". The link to download the paper is this.
The premise of the paper is
"Two microphone arrays are used for producing a specific directivity pattern by a time delay between the two microphones. Directional hearing aids are examples of the two microphone arrays application. In this paper, the conventional time delay method was replaced with a digital filter method for directional digital hearing aids."
On the second page of the paper, it states,
"If DF1 and DF2 are optimally designed so as to produce the same magnitude response, but the constant phase difference response between DF1 and DF2, the resulting y[n] in figure 2 should be the same as x[n] in figure 1. "
I'm guessing the above statement should instead read "so as to produce the same magnitude response, but varying phase difference response"
My guess is by keeping the magnitude the same between the two signals, but varying phase should be equivalent of causing a time delay between the two signals. Am i right?
If so, how can I calculate filter co-efficients to vary the phase between the two signals in order to produce an exact time delay of few micro seconds?