TABLE OF CONTENTS Implementation of Figures 8.1 and 8.2 for angle measurement involves forming beam patterns f 1( ?) and f 2( ?), combining them to obtain ?( ?) and ?( ?), and forming the error signal ?/ ?. This error signal may be smoothed and used as output data, or fed back to control the beam position through an antenna servo or beam-steering computer.
Although the ? and ? symbology may seem to imply monopulse implementation, it applies equally to all measurement and tracking systems. In Figure 8.3(a), the two beams are formed sequentially, and signals from each are stored over one or more complete switching cycles, after which ?, ?, and ?/ ? are computed from the stored signal voltages. A common type of analog process, Figure 8.3(b), uses an automatic gain control (AGC) loop with long time constant to perform the normalization and to extend the dynamic range of signals accommodated by the receiver. In Figure 8.3(c), the beams exist simultaneously and signals are fed to an RF network, which forms ? and ?. Normalization is again performed by an AGC loop that is closed on the ? receiver output and gives open-loop control to the ? channel. If the two beams in (a) and (b) are displaced by ? k ? 0.3 ? 3 (crossing near the -1 dB...
