What is a timing oscillator?
A timing oscillator in regard to GNSS timing is a fixed internal oscillator circuit that is placed within the clock.
In most implementations, this oscillator circuit is traditionally tuned by the frequency output of the GNSS receiver. By tuning to the frequency of the receiver the oscillator will continue to oscillate(for a certain time) at the same frequency as the GNSS receiver if the GNSS receiver has lost its usable GNSS signals.
The frequency of the oscillator will allow the outputs of each port to continue to deliver time and date information despite not having a GNSS/external time source.
When the usable GNSS signals are lost, the internal oscillator of the clock does not have a frequency reference source. Therefore, the oscillator starts to drifts from its frequency reference and consequently the accuracy of the time signals decreases.
The better oscillators will have better accuracy with less drift when the external time source or GNSS signals are lost.
Typically there are two types of oscillators: crystal and atomic.
Crystal oscillators hold accuracy for less time but are on average are the cheaper option. They work by using the mechanical resonance of a vibrating crystal to create an electrical signal at a certain frequency.
Atomic oscillators are used in atomic clocks in addition to GNSS time source. Atomic oscillators tune an electronic oscillator by using the frequency of the signals produced by the natural vibrations of atoms, this frequency reference is used to output the desired oscillating signal to output the precise time.
However due to the scarcity of the resource needed to make these types of oscillators they are typically far more expensive than crystal oscillators.
Types of oscillators
TCXO or Temperature Compensated Oscillator is a type of oscillator that will compensate for the accuracy of the oscillator if the temperature increases. This ensures that the accuracy of the oscillator is more accurate by holding a constant output oscillator frequency.
A VCTCXO is a voltage-controlled version of the TCXO. This means that the oscillator can have its frequency changed with a change in input voltage. This allows greater tuning of the oscillator when there are variations in the supply voltage by maintaining a stable oscillation frequency.
OCXO or Oven Crystal Oscillators are oscillators that are equipped with a circuit that maintains a crystal's temperature to hold a constant output oscillation frequency. the high stability and better accuracy is achieved by maintaining a near-constant crystal temperature regardless of the ambient temperature, the OCXO oscillator is experiencing.
Rubidium oscillators are the cheapest tier of atomic oscillators, thus the cheapest atomic clocks.
The RB oscillators are used as reference sources to tune an internal crystal oscillator using the natural frequency vibrations produced by the atoms transitions in Rubidium-87.
Typically rubidium oscillators are more accurate than pure crystal oscillators but less accurate than other atomic clock options.
Caesium oscillators are much like rubidium oscillators where they tune an internal crystal oscillator using the natural frequency produced by the atoms transitions in Cesium-133.
Due to the scarcity of cesium, it is the most expensive atomic clock on the market, but it is also the most accurate. It is also used as the primary standard of the second in the Internal System of Units.
“One second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the two hyperfine levels of the ground state of the Cesium 133 atom”
Unfortunately, due to size and cost limitations Tekron products do not support Cesium Atomic clocks at this time. However, if you are interested in a Cesium clock check out the Microchip 5071A.