GPS advanced OCXO module for LTE and 4G base stations

March 31, 2014 // By Jean-Pierre Joosting
The IQCM-100 GPS advanced OCXO module for use in LTE and 4G base stations, from IQD, achieves a holdover specification of 1.5 microseconds over a period of 24 hours when locked to a 1PPS (Pulse Per Second) input from an external GPS receiver, easily meeting industry standard holdover requirements.

Incorporating an adaptive algorithm which has the ability to ‘learn’ from a stable GPS signal over a period of 2 days, the algorithm can be adjusted to allow for errors. Frequency is accurate to within ±1E-12 when locked to a 1PPS GPS signal and can compete with the performance of many atomic clock references.

Housed in a 65 x 65mm hermetically sealed thru-hole package, the IQCM-100 offers an HCMOS output, operating temperature range of –10 to 60°C, 5-V supply voltage and a current input of 2 mA during warm up.

The module incorporates a low drop out voltage regulator coupled to a highly stable internal OCXO which is conditioned by a digital-to-analogue converter which in turn is fed from an ARM microcontroller. This controls an FPGA which provides the 1PPS output and is fed from the accurate GPS signal.

Further, the product offers some 21 internal algorithm parameters to the user. Using a serial data word output, the user can access information including current status (warm up, holdover or lock); time since attaining lock status; current phase shift between signal input and output; average phase shift over the last hour.