Rb frequency standard with expanded operating temperature range (-55/spl deg/C to +95/spl deg/)

Second and third generation cellular telephone systems demand better and better frequency standards at low cost and high volume. In particular, frequency references for cell stations must operate un-attended for long periods of time over a very wide temperature range. Because of the large number of cells required, the hardware cost and reliability of all elements in the cell station become critical to the economic viability of any cellular system. These considerations have led to requests for Rb frequency standards capable of operating at temperatures above 90/spl deg/C. In an effort to meet these requests, Frequency Electronics, Inc. developed the FE-5652A Rb frequency standard, a wide temperature range device, which operates from -40/spl deg/C to +85/spl deg/C, with less than 1E-10 frequency error. This unit employs a thermoelectric cooler to maintain the Rb absorption elements at acceptable temperatures at the high end of the ambient temperature range. In the paper, modifications to the FE-5652A design that allow it to operate from -55/spl deg/C to +95/spl deg/C are discussed. Performance data over this extended temperature range are presented, and tradeoffs associated with this performance are discussed.