Glossary

Allan Deviation (ADEV) is a measure of frequency stability that shows how an oscillator's frequency changes over different averaging times. It helps engineers evaluate both short-term and long-term stability, providing a comprehensive view of timing performance across a wide range of operating conditions.
ADEV is typically presented as a graph of stability versus averaging time (τ), making it easier to assess oscillator performance and identify the dominant noise sources affecting the signal. Lower ADEV values indicate better frequency stability and more accurate timing.
ADEV is widely used to characterise high-performance frequency and timing products, including OCXOs, atomic clocks and GNSS-disciplined oscillators, for applications where precise frequency control, timing and synchronisation are critical, including telecommunications, AI data centres, GNSS/PNT, defence, space, IoT and other next-generation connected systems.

A crystal resonator (Xtal) is a passive component that uses a quartz crystal to provide a stable frequency and is used as the frequency reference in oscillators and timing circuits.
Rakon’s crystal resonator types include tuning fork, standard SMD, and leaded crystal resonators.

Generally, XOs are lower in cost than TCXOs as they do not have temperature compensation. They are simply quartz crystals combined with basic oscillation circuitry. XOs can offer high frequencies with low performance. They are typically used in telecommunication networks and other broadband applications.

Rakon’s advanced quartz-based resonator technology. It is made with Rakon’s NanoQuartz™ microfabrication process, delivering unprecedented resonator and oscillator performance.

 A small cellular base station that plugs into an existing internet connection and provides strong mobile signal in the home. (See also small cells definition). 

A filter is an electronic component that allows desired frequencies to pass while reducing unwanted signals. It is used to improve signal quality and minimise interference in RF and timing systems.
Rakon offers crystal, ceramic, and SAW (Surface Acoustic Wave) filters, each designed for specific frequency ranges and applications.

Frequency drift is the gradual change in an oscillator’s output frequency over time, often caused by ageing, temperature fluctuations, and internal material effects. As drift accumulates, timing errors increase, and system stability may decline, especially when external references such as GNSS or network signals are unavailable. In telecom, space, defence, GNSS, IoT, and consumer sectors, frequency drift impacts signal accuracy and synchronisation across systems. Managing drift is essential for reliable performance during reference signal interruptions.

 A complete subsystem that provides up to 48 outputs from the same ultra stable reference oscillator. 

Frequency drift is the gradual change in an oscillator’s output frequency over time, often caused by ageing, temperature fluctuations, and internal material effects. As drift accumulates, timing errors increase, and system stability may decline, especially when external references such as GNSS or network signals are unavailable. In telecom, space, defence, GNSS, IoT, and consumer sectors, frequency drift impacts signal accuracy and synchronisation across systems. Managing drift is essential for reliable performance during reference signal interruptions.

Holdover is the ability of a timing system or oscillator to maintain accurate frequency, phase, and timing when its main reference signal, such as GNSS or network synchronisation, is temporarily lost. In telecommunications, space, and defence, systems rely on internal oscillators to keep signals aligned and errors controlled during outages. In GNSS, PNT, and IoT, holdovers allow devices to operate smoothly and maintain accurate time during interruptions, minimising disruptions to positioning and data flow.

Micro-jumps are extremely short, difficult-to-detect jumps in an oscillator’s frequency. Although subtle, they can cause timing and positioning errors and increase the risk of losing GNSS signals. Detecting micro-jumps requires high-resolution testing to capture the rapid, transient jumps in frequency that may be missed by standard measurement techniques.

The micro-jump test is especially important for oscillators used in GNSS receivers, telecommunications, space, defence, test equipment, and IoT devices, where precise timing and frequency stability are critical.

Rakon’s proprietary photolithography microfabrication process on quartz wafers.

An oscillator is an electronic device or circuit that generates a stable, periodic electrical signal (a clock signal) at a defined frequency, typically using a crystal resonator and associated components.
Rakon’s core oscillator families include OCXO & OCSO, TCXO, VCXO & VCSO, VCO, and XO.

OCXOs are used in applications where precise reference clocks are needed to secure high volume data traffic. Stabilities can be as tight as less than 1 part per billion (ppb). OCXOs are generally more expensive, physically larger and consume more power than a TCXO.

An oven controlled oscillator using Surface Acoustic Wave (SAW) technology instead of a quartz crystal.

Phase error is the difference in phase between a signal and its reference, indicating misalignment within the signal’s cycle. In RF systems, phase error impacts signal coherence, modulation accuracy, and synchronisation quality.

Phase-locked oscillators (PLO) are frequency sources that deliver a signal of high spectral purity. Integrated stable reference is the key building block of PLOs, enabling a better close-in phase noise and achieving a lower noise floor. PLOs are generally used in communication and radar applications.

Phase noise is the rapid, random fluctuation in a signal’s phase, appearing as noise close to the main frequency. Lower phase noise means a purer signal and more stable timing. In RF and microwave applications, low phase noise is essential for clear signals, efficient communications, and reliable system performance.

Phase noise and jitter are two ways of describing the same underlying timing instability. Phase noise is measured in the frequency domain (typically in dBc/Hz versus offset frequency), while jitter is measured in the time domain (typically in seconds or femtoseconds). Engineers often convert integrated phase noise into RMS jitter when evaluating clock and oscillator performance.

ppm, ppb, and ppt are units used to describe very small frequency errors relative to a nominal (reference) frequency. Instead of showing the error in hertz (Hz), they express it as a very small fraction of the intended frequency.

• ppm (parts per million) = 10⁻⁶

• ppb (parts per billion) = 10⁻⁹

• ppt (parts per trillion) = 10⁻¹²

These units make it easy to compare frequency accuracy and stability across different operating frequencies.

Example: A 1 Hz error equals:

• 1 ppm at 1 MHz

• 1 ppb at 1 GHz

• 1 ppt at 1 THz

ppm, ppb, and ppt are commonly used to specify frequency performance such as tolerance, stability (short- and long term), temperature effects, ageing, and holdover in filters, crystal resonators, oscillators, clocks, timing systems, and related equipment.

A small, lower cost, cellular base station, typically installed on lamp posts which provides a limited area coverage compared to conventional (macro)base stations. Small cells are expected to reduce the need for macro stations.

A portable device with added data functionality such as internet access, computing and video capability. Examples include smart phones and tablets.

Synchronisation is the coordination of events, processes, or systems so they operate at the same time, at the same rate, or in the same sequence, ensuring smooth operation. In RF and microwave frequency control and timing, synchronisation aligns frequency, phase, and timing to a reference, enabling accurate signal operation. In Artificial Intelligence (AI), high-performance computing (HPC), and distributed systems, synchronisation is critical for coordinating data flow, parallel processing, and communication between computing nodes, ensuring that data is processed accurately, efficiently, and in step across the entire system..

At the heart of SAW oscillators are SAW resonators that use the piezoelectric effect to generate electrically stimulated acoustic waves at a resonant frequency.

A TCXO is essentially a quartz crystal combined with electronic circuitry to make it oscillate and it also removes much of the error in frequency caused by variations in temperature.

Timing refers to when events or signals occur and how precisely they are controlled or measured within a system. In RF and microwave frequency control and timing, timing is the precise control of signal events relative to a reference clock, ensuring accurate signal generation, synchronisation, and system performance.

Timing accuracy describes how closely and precisely a system’s timing matches its intended or reference time. It represents the difference between when an event or signal is supposed to occur and when it actually happens. Higher timing accuracy means smaller timing errors, which enables more reliable system performance, better synchronisation, and precise signal generation. In frequency control and timing applications, maintaining high timing accuracy is essential for reliable data transmission and device coordination.

Timing error is the difference between when an event or signal actually occurs and when it is supposed to occur within a system. It represents any deviation—either early or late—from the expected timing. Timing errors can lead to loss of synchronisation, reduced sampling accuracy, and degraded overall system performance. In frequency control and timing applications, minimising timing error is crucial for ensuring that signals remain aligned, data is transmitted accurately, and devices work together reliably.

Timing Equipment refers to standalone systems whose primary function is to provide precise time and frequency references for other systems. These units generate, maintain, or distribute timing signals to ensure synchronised and reliable operation across platforms.

They are fully integrated and deployable, with standard interfaces to deliver timing outputs such as PPS, frequency signals, or network-based synchronisation.

Rakon provides Timing Equipment such as GNSS receivers and Software Defined Radio (SDR) platforms that deliver precise synchronization and timing services for NewSpace payloads and platforms.

 A Timing Module is a self-contained unit that provides precise timing or synchronisation within a system. It typically integrates a high-stability oscillator, control electronics, and optional disciplining sources (e.g., GNSS) to ensure accurate and reliable time and frequency distribution.

Rakon timing solutions, such as PPSDO (or Smart OCXO), can be used as timing modules in system-level applications. 

 A Timing Subsystem is a functional assembly that generates, conditions, or distributes precise time and frequency signals within a larger system. It performs a defined role in the timing chain but must be integrated into higher-level equipment to operate.
These subsystems provide the critical building blocks for timing performance, including clock generation, frequency synthesis, and signal distribution.
Rakon Timing Subsystems include Master Reference Oscillators (MRO), PLDROs, Digital Pulse Compression Subsystems (DPCSS), Frequency Multipliers, Frequency Synthesisers, and Signal Distribution Amplifiers. 

An extremely stable oscillator used in high-end space and instrumentation applications.

Many applications demand an even higher level of performance than our high stability TCXOs. Rakon’s Ultra Stable TCXOs can achieve stabilities better than 100 parts per billion (ppb) over temperature.