Viron - you could just create one circle within a 2-D array whose number of rows and columns are identical to the diameter of your circle. For example, using code similar to yours
r = 50;
n = 1000;
X = repmat(linspace(-r,r,n), n, 1);
Y = rot90(X);
C = X.^2 + Y.^2 <= r^2;
imagesc(C)
axis image
The radius r for our circle is 50. We use linspace to create a row array of n elements from -r to r (so the interval [-50,50]). We then use repmat to repeat this row n times. We then rotate this matrix by 90 degrees counter-clockwise to get the Y (this should be identical to your use of meshgrid). We then create one circle as you have already done with the only difference being that the circle of radius 50 is now inside a square with the a length and width being the diameter of your circle.
We can then again use repmat to repeat the C to how many circles we want in the x and y direction.
nc = 10;
MC = repmat(C, nc, nc); % multiple circles
imagesc(MC)
axis image
