260 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



High-Frequency Crystal Units for Primary Frequency Standards. A. 

 W. Warneri. I.R.E., Proc, 40, pp. 1030-1033, September, 1952. 



A new approach to the design of crystal units for primary frequency standard 

 use has resulted in crystal units in the 3- to 20-mc frequency range characterized 

 by high Q and low capacitance in the series arm of the equivalent electrical 

 circuit. By utilizing the overtone frequency of specially shaped AT-cut quartz 

 plates, both Q and the rate of impedance change with frequency are enhanced 

 together, and in addition the stability with time of the crystal unit is increased 

 because of a larger frequency-determining dimension. Additional characteristics 

 of the crystal units include small size, stability under conditions of vibration and 

 shock, and low-temperature coefficient. Crystal-oscillator stabilities of one part 

 in 10^ per month have been achieved without recourse to stabilized circuits. 



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