Klein Heidelberg – a Ww2 Bistatic Radar System That Was Decades Ahead of Its Time 1

We present a description and analysis of the German WW2 bistatic radar system Klein Heidelberg. A brief account is given of the nature of the electronic war between the Allied bomber aircraft and the German air defence system, to show the context in which the Klein Heidelberg system evolved. This is followed by a description of the development of Klein Heidelberg, a technical description, and an assessment of its performance. Next, a discussion of its operational significance, of what happened after WW2, and finally some conclusions and some lessons learned that may be relevant to the development of present-day bistatic radar systems. In particular, we show that its performance was impressive, yielding detection ranges of Allied bombers in excess of 300 km, but that it became operational too late to make any significant difference to the course of WW2. 1. CONTEXT The term bistatic refers to a radar in which the transmitter and receiver are in separate locations (Figure 1). In practice this means that they are separated by a considerable distance, usually understood to be of the order of the target range, so as to distinguish it from smaller separations designed only for receiver isolation from the transmit signal, and this gives bistatic radars some different and distinct properties compared to conventional monostatic radars [2, 3]. Bistatic radar is presently a subject of significant interest and research in many countries worldwide, which is reflected in the large volume of publications in academic journals and at conferences. The purpose of this piece is to present and analyse information on a German WW2 bistatic 1 This is a substantially-expanded version of a paper published in IEEE Transactions on Aerospace and Electronic Systems [1]. It places greater emphasis on the historical background, and includes information that could not be included in that paper for reasons of space. In addition, online publication of this version should allow wider access, and should allow easy correction and updating as and when new information is brought to our attention – as we hope very much that it will. But if reference is made to this work, please cite the published reference [1]. * Hugh Griffiths holds the THALES/Royal Academy of Engineering Chair of RF Sensors at University College London. Nick Willis is retired (sort of). Email addresses: [email protected], [email protected]