5.1 History and Terminology [1]

Suppose an operator is using a stationary radar with a parabolic dish antenna to measure the angular position (e.g., elevation ?) of a stationary point target. The operator probably would first find the antenna position that maximizes the returned signal; the target is now on the antenna boresight, which corresponds to maximum gain G. If the antenna is moved in elevation so the target is slightly off boresight, the change in returned signal is not great because the slope of the beam pattern, d G/d ? is small (in fact, zero on boresight; see Problem 5.1). However, if the antenna is moved in elevation so the target is farther off boresight, d G/d ? is larger, but G is smaller. There is some optimum angle off boresight, ? ₀ , such that a small change in ? produces the maximum observable difference in the overall returned signal. The operator might choose to set the antenna so the target is at that position in the beam, thereby creating the maximum sensitivity of the returned signal to a small change in angle and allowing the most precise measurement of ?.

The lobe switching technique was developed to take...