Techniques and Facilities for Microwave Radar Testing* 



By E. I. GREEN, H. J. FISHER, J. G. FERGUSON 



Methods and devices are described for testing microwave radars in the radio 

 frequency range from about 500 mc to 25,000 mc, and at associated video fre- 

 quencies. In general, the same instruments and techniques are applicable also in 

 testing microwave communication systems. 



Introduction 



' I '*HAT radars are marvels of ingenuity has long since become common 

 -*■ knowledge. This ingenuity is reflected, however, in complexity of 

 circuits. A rough index of this is found in the number of vacuum tubes, 

 which for a single radar may range from 50 to 250. Notwithstanding the 

 most careful design, it is easy for the radar performance to become impaired 

 under operating conditions. 



Not only is radar complex, but its performance criteria are less tangible 

 than those of conventional communication systems. Ordinary radio is to 

 some extent self-testing in that reception of intelligible speech or signals 

 frequently constitutes a sufficient check of satisfactory performance. With 

 radar, the greater the range coverage and the more accurate the data, the 

 more valuable the information is likely to be. However, the working range 

 may fall to a fraction of the possible maximum or some other degradation 

 or malfunctioning may occur, with nothing in the operation of the radar to 

 tell that this has happened. Since lack of maximum performance may have 

 serious military results, measurement of performance assumes the utmost 

 importance in radar work. 



The new techniques and new frequency ranges employed for radar ne- 

 cessitated the wartime development of a wide variety of new types of test 

 equipment. A large part of this development work was concentrated at 

 Bell Laboratories and at the N.D.R.C.'s Radiation Laboratory at M.I.T., 

 working in close coordination with one another and with the technical 

 services of the Army and Navy. In the manufacture of radar test equip- 

 ment, Western Electric took a major part. This article discusses the tech- 

 niques of radar testing and describes the types of test gear developed by 

 Bell Laboratories and manufactured by Western Electric. These cover 

 the radio frequency range from about 500 megacycles to 25,000 megacycles, 

 together with associated video frequencies. 



Because of its importance during the war, emphasis has been placed on 



* Presented at A.I.E.E. Winter Convention, New York, N. Y., January 21-25, 1946. 

 Published by Elec'l. Engg., Trans. Sec, May 1946. 



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