Longer Delays from Fused-Quartz Delay Lines by Multiple Passage Techniques

Long-range, shipboard, search radars employing moving target indication (MTI) use mercury delay lines with delays of 2000 to 4000 microseconds as signal-storage devices. As a result of the tests and investigations, the multiple-delay-line method was concluded to be the most satisfactory way of using quartz delay lines in search-radar MTI systems. The recirculation-frequency-separation system was critical of adjustment and would probably be difficult to adjust and maintain in fleet use. This method, however, did have flexibility since by adjusting one oscillator frequency, the delay times could be changed in multiple delay-line delay time. Of the three methods, the recirculation-time-separation method had the least to offer since it not only showed sever gating transients but also supplied the information for only part of the radar cycle. The multiple-delay-line method was the most promising because it was simple and required no additional circuits (other than the booster i-f amplifiers) for replacement of mercury delay lines. It is recommended that commercial production be encouraged for high quality quartz suitable for use as delay lines.