Coil Pulsers for Radar 



By E. PETERSON 



RADAR systems in current use radiate short bursts of energy developed 

 by pulsing a high-frequency generator, usually a magnetron. One 

 means of developing the requisite impulses employs a non-linear coil and 

 is termed a coil pulser. Such pulsers are found in substantial numbers 

 among the Navy's complement of precision radars. Most fire control 

 radars on surface vessels are equipped with them, and all modern radar 

 installations on submarines are so equipped for search and for torpedo 

 control. 



History of Development 



Coil pulsers had their origin in the magnetic harmonic generators first 

 built for the telephone plant. Multi-channel carrier telephone systems in 

 general use throughout the Bell System require numbers of carriers, harmoni- 

 cally related in frequency. These are derived from non-linear coil circuits^ 

 which convert energy supplied by a sine wave input into regularly spaced, 

 sharply peaked pulses. 



When development was started on precision radars, one of these circuits 

 generating a power peak of a few hundred watts, several microseconds in 

 duration, was adapted to the purpose.^ Its output was shaped and ampli- 

 fied by vacuum tubes of sufficient power to key or modulate the ultra-high- 

 frequency generator of the radar transmitter. All early fire-control radars 

 were made up in this way; hundreds are still in use. 



The next development of pulsers for fire-control radars was directed toward 

 higher-powered pulses, shorter in duration for good range resolution. These 

 had to be provided by a small package pulser, small enough and rugged 

 enough to mount integrally with the magnetron and the antenna. The power 

 rectifier was to be located at any convenient distance, and the rectified voltage 

 had to be low enough to permit the use of standard low-voltage cables. 

 These requirements put high vacuum tubes at a disadvantage in handling 

 tlie finally developed pulses. Pulse transformers had not attained their 

 present state of perfection in dealing with short pulses at this early stage 

 and the pulser therefore had to work the magnetron directly. 



1 Magnetic Generation of a Group of Harmonics, by Peterson, Manley and Wrathall, 

 B.S.T.J., vol. XVI, p. 437, 1937. 



2 Fire-Control Radars, by Tinus and Higgins, B.S.T.J., January, 1946. 



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