  We revisit the free field construction of the deformed $W$-algebra by Frenkel
and Reshetikhin [Comm. Math. Phys. 197 (1998), 1-32], where the basic
$W$-current has been identified. Herein, we establish a free field construction
of higher $W$-currents of the deformed $W$-algebra associated with the twisted
affine Lie algebra $A_{2N}^{(2)}$. We obtain a closed set of quadratic
relations and duality, which allows us to define deformed $W$-algebra
${\mathcal W}_{x,r}\big(A_{2N}^{(2)}\big)$ using generators and relations.
