Mass-Produced Quartz Oscillators as Low-Cost Replacement of Passive Rubidium Vapor Frequency Standards

High precision oscillators that are capable of effectively operating over large temperature ranges and extreme temperature transients as well as providing excellent aging and holdover are continuously sought by industry. The wireless telecommunications industry, in its constant quest to minimize the cost of base stations, has reduced the usage of GPS in applications such as UMTS. Consequently, it requires oscillators with reliable and proven aging, where the oscillator free-runs and maintains an accuracy of better than 40 ppb for a minimum of ten years. Other applications require oscillators that must exhibit excellent temperature coefficients. For CDMA applications that oscillator is expected to provide better than 10 microseconds time-error over a 24 hour period (holdover). In wireline applications oscillator stability and holdover capability is paramount for building integrated timing supply (BITS) clocks, timing signal generators (TSG) and synchronization supply units (SSU). Similarly, applications exist in the Aviation, Navigation, Instrumentation, Military and other markets. In the past these industries had only two choices: rubidium atomic standards, or limited quantities of virtually non-reproducible precision crystal oscillators. In this paper we present a class of extremely precise, yet reproducible oscillators, developed by Frequency Electronics, Inc. These oscillators are identified as the FE-405A Series, and are capable of providing any frequency from 1 pps to 100 MHz with an aging characteristic of better than 20 ppb/10 years, accumulated time error of less than 10 microseconds in 24 hours and with temperature coefficient of < 1 x 10^-10 over the temperature range of -40degC to +75degC. These devices are currently being mass-produced using standard manufacturing techniques at approximately one-third the cost and one-fifth the power dissipation of rubidium vapor frequency standards. Quartz oscillators with internal MEMS acceleration compen- sation are also discussed. These oscillators provide as much as 30 dB reduction in vibration sidebands for vibration from DC to 2 KHz.