Improvement of Precision in TCXO

Compact precision low-power TCXO shows comparable performance to OCXO

A dramatic increase in telecommunication data traffic in mobile devices such as smartphones has now started to require the installation of small cells and optical transport networks. Up till now, atomic frequency standards or OCXO have been used as reference clocks for synchronizing networks. To cater to the demand for cost reduction, Murata has accomplished stability of frequency in TCXO that is comparable to that of OCXO by improving the precision of TCXO .

The data traffic at base stations of mobile networks has been getting closer to its maximum capacity because of ever-increasing mobile traffic due to distribution of online video and other data. One of the suggested solutions for this problem is to increase the number of small cells, and by doing that, to reduce the load of work on macrocells. As a result, the demand for small cells is expected to increase in the future. 

One of the main reasons for that is installation cost: the cost for increasing the number of macrocells is enormous, whereas the cost for small cells is low. The base stations for these cells are equipped with precision clocks. 

The highest-grade clocks in the core system of each telecommunication company use the atomic frequency standard of cesium, rubidium, etc. to accomplish an extremely high precision. 

The equipment installed in the base stations is designed to synchronize to the atomic frequency standard. If it should lose synchronization for any reason, the equipment must use its own reference of precision for maintaining its communication. For that purpose, a certain degree of precision is set for holdover and free-run: the former uses stored synchronized data to maintain the precision of its own internal reference clock for a fixed time, and the latter operates at its own precision.

The precision TCXO(HS-TCXO)XT(N)CLH_J series provides temperature characteristics comparable to OCXO, allowing the precision of ±100 ppb over a temperature range from -10°C to 70°C (±200 ppb over a temperature range from -40°C to 85°C). The product can achieve a sufficient precision for operation under the holdover and free-run modes. We are currently developing new products that will have a more extensive operating temperature range. 

With its IC construction technology, Murata has developed a single chip IC for TCXO, where an oscillator circuit and a temperature compensation circuit are both mounted; the latter was configured to achieve a higher-order temperature compensation function (the load capacitance of quartz crystal can be varied by changing the voltage of the compensation circuit). Optimization of blank design by simulation has helped us develop quartz crystals with no frequency dip . HS-TCXO has used all of the above-mentioned technologies to establish precision temperature characteristics as well as a compact low-power feature comparable to OCXO. 

Photograph of the exterior of HS-TCXO

Photograph of the exterior of HS-TCXO

Chip TCXO block diagram

Chip TCXO block diagram

OCXO block diagram

OCXO block diagram

Temperature characteristics of conventional TCXO (-30°C to 85°C)

Temperature characteristics of conventional TCXO (-30°C to 85°C)

Temperature characteristics of HS-TCXO (-40°C to 80°C)

Temperature characteristics of HS-TCXO (-40°C to 80°C)

Temperature characteristics of HS-TCXO (-10°C to 70°C)

Temperature characteristics of HS-TCXO (-10°C to 70°C)

Glossary

OCXO (Oven Controlled crystal Oscillator) : Oven controlled crystal oscillator. A crystal oscillator equipped with a temperature-controlled chamber.
TCXO (Temperature compensated crystal Oscillator) : Temperature compensated crystal oscillator.
Clock: A source of signal.
Small cell: A small base station for in-building and small area wireless service.
Macrocell: Base stations for wireless service in use today.
Frequency dip: Abrupt fluctuation of resonant frequency that occurs when temperature is changed continually in a quartz crystal.

Products & Markets