Waveguide Investigations with 

 Millimicrosecond Pulses 



By A. C. BECK 



(Manuscript received October 11, 1955) 



Pulse techniques have been used for many waveguide testing 'puryoses. 

 The importance of increased resolution hy means of short pulses has led to 

 the development of equipment to generate, receive and display pidses about 

 5 or 6 millimicroseconds lo7ig. The equipment is briefly described and its 

 resolution and measuring range are discussed. Domi7ia7it mode waveguide 

 and antenna tests are described, and illustrated. Applications to midtimode 

 waveguides are then considered. Mode separation, delay distortion and its 

 equalization, and mode conversion are discussed, and examples are given. 

 The resolution obtained with this equipment provides information that is 

 difficult to get by any other means, and its use has proved to be very helpfid 

 in ivaveguide investigations. 



CONTENTS 



1 . Introduction 35 



2. Pulse Generation 36 



3. Receiver and Indicator 41 



4. Resolution and Measuring Range 42 



5. Dominant Mode Waveguide Tests 43 



6. Testing Antenna Installations 45 



7. Separation of Modes on a Time Basis 48 



8. Delay Distortion 52 



9. Delay Distortion Ecjualization 54 



10. Measuring Mode Conversion from Isolated Sources 57 



11. Measuring Distril)uted Mode Conversion in 1 ong Waveguides 61 



12. Concluding Remarks 65 



1. INTRODUCTION 



Pulse testing techniques have been employed to advantage in wave- 

 guide investigations in numerous ways. The importance of better resolu- 

 tion through the use of short pulses has always been apparent and, from 

 the first, eciuipment was employed which used as short a pulse as pos- 

 sible. Radar-type apparatus using magnetrons and a pulse width of 

 about one-tenth microsecond has seen considerable use in waveguide 

 research, and many of the results have been published.' • - 



35 



