Among the most basic of antenna properties is angular resolution. Several methods exist for increasing radar resolution. Pulse compression is the classic method of producing increased resolution along the antenna boresight axis. For a moving platform, synthetic aperture techniques vastly increase the along track resolution. In this paper, an innovative method called scanned time/angle correlation (STAC) is presented which provides increased antenna angular resolution. This angular resolution is shown to be independent of antenna size and frequency and unlike synthetic aperture techniques requires motion of neither the target nor the platform.
Two bistatic SAR image quality metrics are postulated. The combination of the two metrics provide a quick and computationally non-intensive means of predicting bistatic SAR image quality as a function of collection geometry. The metrics are based on local orthogonality criteria. By noting the fact that all SAR imaging techniques essentially map the downrange and Doppler frequency onto the image plane, it is observed that the downrange and crossrange direction vectors can be obtained via the gradients of the isorange and isoDoppler contours respectively. Using the criteria that maximum image information content is obtained if the downrange and crossrange directions are orthogonal, a metric is postulated which relates the isorange and isoDoppler contour grandients in such a way as to be maximum under such orthogonal conditions. A secondary measure of merit is also postulated related to isoDoppler contour density and crossrange resolution for a given CPI. A good qualitative correlation between the image metrics and reconstructed images of a representative collection of point scatterers was shown to exist.
In bistatic and multistatic systems, a variety of observables may be used to obtain a final target location. The total target location error will depend upon what observables are used to obtain the location, the individual measurement errors, and the viewing geometry. In planning for a bistatic mission, it is advantageous to have a tool for a priori estimation of target location error as a function of all potential sensor and target positions. This paper presents one such tool, based upon a modification of the dilution of precision (DOP) methodology long utilized in GPS navigation and developed herein into a system of equations specifically for use in a bistatic sensor system. This tool is a system of equations which allow easy determination of a figure of merit, the bistatic position dilution of precision (BPDOP). The BPDOP gives a direct, quantitative measure of the target location effectiveness of a given bistatic sensor geometry for any given potential target location. The paper derives the equations for the BPDOP for six observables: the monstatic range, the bistatic range; the monostatic and bistatic azimuth angles; and the monostatic and bistatic depression angles. Several example scenarios are simulated.