Design and realization of a broadband single-side-band mixer with a very short settling time

To achieve high range resolution in synthetic aperture radar imaging a frequency synthesizer with high bandwidth is a possible solution. To operate in the required frequency band an LF-signal usually has to be upconverted. In this paper we describe the design and realization of a broadband Single-Side-Band Mixer with a very short settling time between frequency steps of arbitrary length inside a high bandwidth. Compared to already existing SSB-Mixers, our novel concept has three major advantages: At first, the mixer could be used in combination with an arbitrary signal source. Due to a modular circuit concept it is possible to use the system for different input frequency ranges. Moreover, just by changing single modules, the output frequency-range can be adapted to individual requirements. Thirdly, as a main advantage, the system is able to generate a high frequency output span with a very fast settling time between frequency steps. Even with applied steps up to 400 MHz, the settling time remains below 3 μs, which is more than 5 times faster than the settling time of similar synthesizers

Motion compensation of short-range, wide-beam synthetic aperture radar

Up to now, SAR systems are a well known possibility for long-range detection. Applying them for short-range applications with wide-beam antennas, of course, does not increase the resolution but the probability to detect hidden targets with an anisotropic radar cross section significantly in comparison to other detection systems. Working with an appropriate wavelength even improves the possiblity to look through natural cover like grass. An application is detecting fawn while pasture mowing. The main issue in such applications is the antenna's motion in range direction as it is carried by cars or traction engines. If motion is not compensated, the phase cannot be reconstructed correctly, the resolution gets poorer and, in worst case, the target even disappears. Conventional methods for motion compensation either fail for wide beam antennas, since for contributions of wide angles the phase reconstruction is incorrect, or is not applicable for realtime data processing, because the processing time due to interpolation or similar steps is very high. We present a method of image reconstruction regarding motion of the antenna as well as wide beamwidth. This method is analyzed concerning processing time in comparison to the conventional image reconstruction. In our system we use a combination of algorithms. There is shown a comparison for different algorithms dependent of the antenna's motion and aperture angle