Martello
Development of the transmitter solid state power amplifiers was based on using up to 40 (one for each row); thus the total complexity was eased in that there were now 40 rows rather than 60.
Each row may be energized by a transistor amplifier module which is mounted at the corresponding level in the central spine, the number of amplifiers fitted, and so the power radiated, depending upon the operational requirement up to the maximum of 40. Whether or not driven by a transmitter, each row has a receiver system including a low noise r.f. amplifier, and the 40 outputs at i.f. are fed to the b.f.n.
The r.f. transistor power modules have been developed after a long period of evaluating transistors from all available sources, worldwide. Life tests of complete modules indicate a very high degree of reliability even when subjected to electrical maltreatment such as badly mismatched loads. Even so, it is not yet possible to provide high peak powers with solid-state devices. Thus, in order to achieve the requisite detection performance, S723 (like other solid state radars) has to use lower peak power pulses of longer duration than in a comparable radar employing thermionic tubes. The S723 transmitted pulse length is 150 uS, compressed to 0.25 uS - the same as in the S713.
The performance of the S723 is summarized in figure 18, where it will be seen that, despite the lower transmitter power, the effects of the lower noise figure and slightly increased antenna aperture combine to give a longer range detection capability than the S713, on comparable targets.
Both S713 and S723 are in production as together they enable the Company to offer the most appropriate solution to different defence requirements.
The arguments of comparison can be complex and protracted but in the simplest terms for defence applications where utmost height accuracy and resistance to noise jamming are prime objectives, the scales may come down in favour of the S713; but where the air defence forces are able to accept slightly broader height data and the incidental advantages of solid state operation are paramount, the S723 could be preferable. Another difference is that the S723 consumes rather less power from the mains supply source; this is of varying importance. depending on the deployment of the radars and the availability of fuel.
A decision on which radar is preferable for a particular case is only reached after full consideration of details of the application, including logistic and operational aspects. In some cases a variant of the basic design embodying special features is appropriate e.g. S713A, S713B etc. However, in summary, all Martellos have the following common characteristics:
(a) Wide-band, unrestricted frequency agility (ECCM)
(b) Ease of establishing accurate beamshapes and low sidelobes across the total bandwidth of the radar.
(c) Ease by which elevation beam angles and shapes can be changed to suit particular operational needs.
(d) Parallel rather than serial processing.
(e) Considerable gain in dynamic range over systems employing single receiver channels.
These Martello features are inherent in its design but in common with multi-beam 3D radars in general, there are the advantages that ground clutter is mainly confined to the lowest beam and the effects of jammers are minimized in that not all elevation beams are likely to be affected simultaneously.
THE FUTURE
It is difficult to imagine the advances which will come in the next 50 years of radar. Perhaps Martello will then be seen as one of the milestones along the way, especially if some of its techniques find new applications. Two at least are probable: the use of the L-Band transistor power modules for other purposes such as Air Traffic Control radars, and the beam forming techniques for a variety of defence require-ments including passive and multistatic radar sensors.
ACKNOWLEDGMENT
Information on Martello has been taken from the work of the team led by H. N. C. Ellis-Robinson, OBE, the Director of Martello Projects, MRSL., who conceived the principle of Martello and to whom the author is greatly indebted.
REFERENCES
1 WARDROP, B., 'The Role of Digital Processing in Radar
Beam-forming', GEC Journal of Research, 3, 1, p. 34, 1985.
2 WALLINGTON,
J. R., 'The Role of Analogue Beamforming in Radar', GEC Journal of Research,
3, 1, p. 25, 1985.
3 ROGERS, A., 'Wideband Linear Squintless Array', Marconi
Review, 187, p. 221, 4th Quarter, 1972.
4 NIEDERLEITHNER, 1., 'The Theory
and Design of a Low Noise Figure Microwave Mixer', Marconi Review, 214, p. 153,
3rd Quarter, 1979.
The article above is taken from "The GEC Journal of Research", Vol. 3 No.2 1985 pages 104-113 and has been reproduced with the kind permission of the Editor.
