Method of measuring the null angle of a monopulse antenna and apparatus therefor

A method of measuring an angular direction of null in the difference pattern of a monopulse antenna, comprising the steps of:

• transmitting an RF signal from an array antenna including a plurality of antenna elements having a predetermined phase relationship to said monopulse antenna;
• changing the direction of said monopulse antenna in sequence so that it faces the respective antenna elements;
• receiving the RF signal every time the direction of said monopulse antenna is switched;
• acquiring values of the radiation electric fields which said respective antenna elements form and the difference signals which said monopulse antenna produces in each direction of said respective antenna elements;
• acquiring the ratios of the acquired difference signals to the corresponding radiation electric fields, wherein said step of acquiring the ratios comprises the step of dividing the difference signal in each direction of said respective antenna elements by a corresponding one of the calibration values;
• and
• acquiring the null angle in the difference pattern of said monopulse antenna in accordance with the acquired ratios, wherein said step of acquiring the null angle comprises the step of acquiring a continuous signal pattern by effecting interpolation processing of the acquired ratios,
• wherein the step of acquiring values of the radiation electric fields comprises the steps of
• acquiring the sum signal which said monopulse antenna produces in each of the directions of said respective antenna elements every time the boresight axis of said monopulse antenna is oriented toward any one of said antenna elements;
• acquiring relative values of the radiation electric fields of said respective antenna elements in accordance with the acquired sum signals;
• and
• storing the relative values for calibration.

An apparatus for measuring an angular direction of null in a radiation pattern of a monopulse antenna, comprising:

• means connected to said monopulse antenna for changing the direction of said monopulse antenna;
• a transmitting phased array antenna facing said monopulse antenna and including a plurality of antenna elements, a like plurality of phase shifters each connected to a respective one of said antenna elements, and a controller for causing respective desired amounts of phase shift to be set in the respective phase shifters, said transmitting antenna being capable of radiating a test signal, said antenna elements being capable of changing the phase of signals passing therethrough;
• a signal processor means receiving the sum signal and the difference signal from said monopulse antenna to acquire the null angle by processing these sum and difference signals,
• and means intercoupling said means for changing and said signal processor means for controlling the phase shift determined by said controller based on the direction determined by said means for changing.

A method of measuring an angular direction of null in a radiation pattern of a monopulse antenna, comprising the steps of:

• transmitting a predetermined RF signal from an array antenna including a plurality of antenna elements having a predetermined phase relationship to said monopulse antenna;
• receiving the RF signal at said monopulse antenna;
• acquiring sum and difference signals which said monopulse antenna produces in each direction of the respective antenna elements;
• and
• acquiring the null angle in the radiation pattern of said monopulse antenna in accordance with the acquired sum and difference signals, comprising acquiring the ratios of the acquired difference signals to the corresponding sum signals wherein said step of acquiring the null angle further comprises acquiring a continuous signal pattern by effecting interpolation processing of the acquired ratios.

A method of measuring an angular direction of null in a radiation pattern of a monopulse antenna, comprising the steps of:

• transmitting a predetermined RF signal from an array antenna including a plurality of antenna elements having a predetermined phase relationship to said monopulse antenna;
• receiving the RF signal at said monopulse antenna;
• acquiring values of the radiation electric fields which said respective antenna elements form and the difference signals which said monopulse antenna produces in each direction of the respective antenna elements;
• and
• acquiring the null angle in the radiation pattern of said monopulse antenna in accordance with the acquired field values and difference signals, comprising acquiring the ratios of the acquired difference signals to the corresponding radiation electric fields wherein said step of acquiring the null angle further comprises acquiring a continuous signal pattern by effecting interpolation processing of the acquired ratios.