Currently available high-precision crystal units are not completely satisfactory for use in certain airborne or missile-borne equipment primarily because they cannot maintain the necessary frequency stability while being subjected to environ¬mental disturbances such as high frequency vibration or shifts in orientation.nA specification sheet, Exhibit WWRN 61-11, was prepared to list those requirements which were considered to be necessary or desirable in high-precision crystal units for use in aircraft or missiles. The requirements were deliberately designed to demand advancement in state-of-art techniques. The purpose of this study was to investigate the feasibility of the requirements and to establish realistic degrees of compliance for those requirements where complete satisfaction could not be attained.nAs expected, it was not possible to produce crystal units which would meet all of the requirements listed. However, It was possible to comply with most of them and to approach the others much more closely than would be expected from evaluation of conventional high-precision crystal units. Design developments made during this study resulted in significant improvements in performance during shock, vibration, and orientation test conditions.nA brief history of this study is given, tracing the develop¬ment of the design which was used on the feasibility-model units. A discussion of evaluation equipment and techniques is included because making accurate measurements of crystal performance proved to be the most difficult portion of the work. Design information for the feasibility-model crystal units is presented. Each of the original goal requirements is listed and comments are made on the extent to which each goal is practical at the present state of the art. A recommended specification is presented to outline realistic requirements for high-precision crystal units of this type.
展开▼
