TABLE OF CONTENTS As discussed in chapter 11, direction estimation using the monopulse procedure assumes only one target being present within the beamwidth. Several targets within the main beam will cause mutual estimation errors. The resolution limit for an individual direction estimation for single targets is given by the beamwidth of the sum beam. This is the well-known Rayleigh limit for all conventional radar systems with reflector antennas and also for phased-array radars, which only form sum and difference beams. The limit is given according to chapter 4 by the fundamental relation for the beamwidth ? = ?/ D, ? the wavelength and D the antenna or aperture diameter. Both parameters are determined by the general system requirements and cannot be changed arbitrarily.
A resolution beyond the limit given by the beamwidth can only be achieved by suitable array processing methods with an active receiving array with access to individual receiving antenna elements or at least to subarrays. This improved angular resolution is called superresolution.
For the target range R and beamwidth ? the lateral resolution is given simply by b = R ?. For a beamwidth of ? = 1 or ? = 0.01745 (radians) and R = 30 km follows b = 523 m. Because the range resolution is usually about 100 m there is a mismatch between these resolution values and an improvement would be very desirable. With superresolution a resolution improvement by a factor of four...
