WAVEGUIDE TESTING WITH MILLIMICROSECOND PULSES 



41 



3. RECEIVER AND INDICATOR 



The receiving equipment is shown in Fig. 4. It uses two traveUng- 

 wave amplifiers in cascade. A wide band detector and a video amplifier 

 then follow, and the signal envelope is displayed by connecting it to 

 the vertical deflecting plates of a 5 XP type oscilloscope tube. The 

 video amplifier now consists of two Hewlett Packard wide band dis- 

 tributed amplifiers, having a baseband width of about 175 mc. The 

 second one of these has been modified to give a higher output voltage. 

 The sweep circuits for this oscilloscope have been built especially for 

 this use, and produce a sweep speed in the order of 6 feet per micro- 

 second. An intensity pulser is used to eliminate the return trace. These 

 parts of the system are controlled by a synchronizing output from the 

 pulse generator 100-kc oscillator. A precision phase shifter is used at 

 the receiver for the same purpose that a range unit is employed in radar 

 systems. This has a dial, calibrated in millimicroseconds, which moves 

 the position of a pulse appearing on the scope and makes accurate 

 measurement of pulse delay time possible. 



Fig. 4 also shows the appearance of the pulses obtained with this 

 equipment. The pulse on the left-hand side of this trace came from the 



PULSE 



SIGNAL 



9000 MC 



SYNC 



SIGNAL 

 100 KC 



TW TUBES 



VIDEO 

 AMPLIFIER 



INTENSITY 



PULSER 



0.05/USEC 



100 KC 



PRECISION 



PHASE 



SHIFTER 



SWEEP 

 GENERATOR 



DOUBLE-GATED 

 PULSE 



REGENERATIVE 

 PULSE 



Fig. 4 — Block diagram of millimicrosecond pulse receiver and indicator. The 

 idicator trace photograph shows pulses from each type of generator. 



