AccuBeat has been providing solutions for precision timing, frequency and synchronization to a wide variety of customers for over 25 years.
With a complete range of products from Rubidium oscillators to fully customized solutions, our products are integrated in commercial and industrial sectors, in telecommunications, in research laboratories and in various militaries worldwide. With patented solutions that will protect critical infrastructures from GNSS jamming and spoofing attacks to Ultra Stable Oscillators (USO) for deep space exploration, you can rely on AccuBeat to fully meet and exceed your project goals.
AccuBeat’s precise time and frequency solutions are an essential element for Communications, Telecoms, Mobile and Financial Services.
AccuBeat’s patented anti-jamming and anti-spoofing equipment and solutions ensure continuous operation even in a GPS/GNSS denied environment.
AccuBeat’s defense solutions and systems enable mission-critical timing and synchronization solutions, even in GPS/GNSS denied environments.
The European Space Agency (ESA) will deploy AccuBeat’s Ultra Stable Oscillator (USO) on its JUICE mission to the planet Jupiter.
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The need for Oscillators
Many engineering applications require a precise time and/or frequency reference signal generally obtained from oscillators or clocks. An oscillator is a device that, if submitted to an electrical or mechanical input, outputs a periodic signal, with various degrees of “cleanness’’ and with periodicity T, that is to say with frequency f=1/T. An accurate and stable oscillator is needed where timing is critical, however the host device may need to perform autonomously.
For example; A satellite requires an internal Rubidium Atomic clock, which is synchronized with clocks on earth. Since the satellite could be out of touch with ground stations from time-to-time, when contact is re-established, both the internal and earth clocks must be in perfect synchronization to maintain communication.
Piezoelectric oscillators have had a wide distribution due to their good short-term stability and low cost compared with the cost of atomic standards. Atomic oscillators are used for their remarkable characteristics of both short and long-term stability and accuracy and the most commercially used oscillators are based on Cesium (Cs) and Rubidium (Rb) atomic standards. It is also important to mention Hydrogen standards (MASERs) as they represent the most precise frequency reference, in spite of their limited range of utilization and very high costs.
Why use Rubidium Oscillators?
Due to the quality/cost ratio, Rubidium oscillators represent a good middle solution between quartz and atomic oscillators of high quality (Cs and H maser) and therefore are currently deployed within a large number of technological and scientific applications. A rubidium oscillator provides a very accurate and stable frequency output with stabilities of parts of 1E-11. This is equivalent to a time accuracy of 1 second in several hundred years. The best crystal oscillators exhibit an inaccuracy of 1 second in 10 years, whereas more costly clocks based on cesium and Hydrogen exhibit an inaccuracy of 1 second in 1 million years.
A rubidium-GPS Clock combines a rubidium oscillator with a GPS receiver. The rubidium frequency is locked to the GPS signal, thus combining the excellent Short Term-Stability of the Rubidium Standard with the superb Long-Term-Stability of the GPS signal. The stability and accuracy of the GPS signal is derived from a system of 24 satellites each carrying on board an ensemble of atomic clocks. These are tracked and maintained traceable to UTC/USNO within 100ns. For more information on the GPS system please refer to https://en.wikipedia.org/wiki/Global_Positioning_System
Another fairly important aspect not to be underestimated, is the possibility of synchronizing (or disciplining) any oscillator with a high precision external reference, The oscillator can be disciplined to a satellite system already operative such as GPS, GLONASS or GALILEO or other such systems. In theory, this strategy allows the use of a medium quality oscillator that is periodically re-calibrated through a circuit that receives the signal from an external reference point thereby guaranteeing very high performances.
Based on the above there would be no need to design high quality oscillators, however certain negative aspects may also be involved that should be analyzed and accounted for as well. For example the reception of the external signal may not be possible or the level of the received signal is so low as to become completely unusable. In this case, we face the so called holdover state, i.e. that there is no external link and, consequently, the performances lower to the same level of those of the free, local oscillator, at least until the reference link is resumed. This operation requires considerable time since it is necessary to re-establish and re-evaluate the received signal.
These considerations point to the necessity for rubidium oscillators, which are most commonly used as a redundant source or as the backup of a complex system of prime-rate quality. In fact, the particular characteristics of the stability of rubidium clocks in the medium-term (approximately one day), allows them to be deployed as free (or self-running) oscillators in situations where they are synchronized from an external source. Examples of this include applications such as the nodes of an inferior hierarchic level telecommunication network, denoted as mutually synchronized conditions, or with GPS receivers of good quality, which are able to make up for a possible loss of the reference signal.