# Buliding a larger matrix from a smaller one

I have my matrix $$h$$ of size $$2N\times 2N$$ in this form

$$h=\begin{pmatrix} a & b \\ c & d \end{pmatrix}$$ where $$a,b,c,d$$ are smaller matrices which i don't know. Is there any simple way to get this matrix? $$\begin{pmatrix} a &0& b&0 \\ 0 &a& 0&b\\ c &0& d&0 \\ 0 &c& 0&d\\ \end{pmatrix}$$

• Check out KroneckerProduct – chuy Jun 25 at 14:41

MatrixForm[h = {{a, b}, {c, d}}]

$$h=\left( \begin{array}{cc} a & b \\ c & d \\ \end{array} \right)$$
KroneckerProduct[h, IdentityMatrix@2] // MatrixForm

$$\left( \begin{array}{cccc} a & 0 & b & 0 \\ 0 & a & 0 & b \\ c & 0 & d & 0 \\ 0 & c & 0 & d \\ \end{array} \right)$$