There is an antenna on the nose. That’s just a pure emitter. There is a first receiver just behind the antenna. And then there is a second receiver right at the tail. The homing systems takes the radar echoes received from both points and makes a comparison. If the signal is stronger in one end or the other, then that is where the target should be.

The rear-facing antenna is used to sample the radar beam that the fighter is using to illuminate the target, so that a semi-active radar seeker can measure the Doppler shift in the return form the target by comparing the frequency of the transmitted and reflected energy.