Synthetic aperture radar guidance system and method of operating same

A method of operating a synthetic aperture radar comprising the steps of:

• a) transmitting a series of chirped pulses;
• b) receiving reflections of transmitted pulses from an object at a range from the synthetic aperture radar and mixing the received signal with a chirped pulse to produce a dechirped signal;
• and
• c) mixing the dechirped signal with a controllable signal and changing the frequency and phase of the controllable signal as the range changes.

A method of operating a synthetic aperture radar on a flying object to form a map of an area on the ground encompassing a plurality of pixels, each representing a location on the ground, the method comprising the steps of:

• a) pointing a beam of radio frequency energy at a location on the ground;
• b) receiving reflections from objects within the patch of ground centered at the locations during a dwell time;
• c) forming an array of pixels from the received signal, the values of each of the pixels representing objects at a different location within the patch;
• d) assigning values to each of the plurality of pixels in one section of the map by selecting one of the pixels in the array of pixels, the selected pixel in the array representing a location on the ground closest to the location represented by the pixel in the map;
• and
• e) repeating steps a) through d) to assign values to pixels in other sections of the map.

A synthetic aperture radar apparatus comprising:

• a) means for transmitting chirped pulses with a chirp slope, S, and a pulse repetition interval, T.sub.p ;
• b) means for receiving reflected radio signals of the transmitted pulses from an object;
• c) means for determining the range between the synthetic aperture radar and the object;
• and
• d) means, responsive to the range determining means, for changing the chirp slope, S, and pulse repetition period, T.sub.p.