= Two-element radio interferometer
{title2=$I(\theta)=2I_0[1+\cos(2\pi b\sin\theta/\lambda+\delta)]$}
A <two-element radio interferometer> coherently combines signals from two receiving <antennas>. With equal single-arm <wave intensity> $I_0$, projected baseline $b$, free-space <wavelength> $\lambda$ and imposed <phase difference> $\delta$, its directional response is the displayed formula. It follows by adding the two <complex amplitudes> and taking the squared <modulus>. Near the normal to the baseline, the first null is $\lambda/(2b)$ from a maximum. This narrow response repeats in <interference fringes>, so a long baseline alone does not give an unambiguous image.
Back to article page
