Is frequency alone enough when selecting a crystal oscillator?
For many applications, frequency, accuracy and operating temperature are the main selection criteria. In high-speed communications, RF systems, GNSS, and precision test and measurement equipment, however, the spectral quality of the clock signal is just as important.
This is where phase noise becomes critical.
An oscillator does not generate a perfectly pure frequency. Small, short-term phase fluctuations spread noise around the carrier in the frequency domain. Phase noise is normally expressed in dBc/Hz at a specified offset from the carrier, such as 1 kHz.
Lower phase noise indicates a cleaner reference clock, helping reduce the effect of clock noise on system performance.
Higher phase noise produces more noise around the carrier. This can degrade signal quality in RF systems, communication equipment, and frequency synthesizers.
Phase noise in the frequency domain is closely related to clock jitter in the time domain. Excessive jitter reduces sampling and timing margins, increasing the risk of errors in high-speed interfaces and network communication systems.
In GNSS and satellite communication systems, clock noise can affect frequency synthesis, signal processing, and weak-signal detection. A cleaner reference clock helps limit these effects.
The reference clock is part of the measurement chain. Its phase noise can influence the noise floor and accuracy of signal generators, spectrum analyzers, frequency counters, and other precision instruments.
Different systems require different combinations of phase noise, frequency stability, temperature performance, and frequency-control capability. YXC offers low-phase-noise solutions across SPXO, TCXO, VC-TCXO, and OCXO product families.
A standard crystal oscillator, or SPXO, is suitable when the design requires a fixed-frequency clock with low phase noise but does not need temperature compensation or external frequency adjustment.
Using 24.576 MHz as an example, the low-phase-noise version of the YSO110TR can achieve phase noise of −153 dBc/Hz at a 1 kHz offset.
The series covers frequencies from 1 MHz to 125 MHz and is suitable for high-speed communications, industrial control, and other applications requiring a clean reference clock.
A TCXO combines low phase noise with improved frequency stability over temperature.
At 10 MHz, the YSO510TP and YSO512ET can achieve phase noise of −150 dBc/Hz at a 1 kHz offset. The YSO510TP offers frequency stability down to ±0.05 ppm.
These products are suitable for communication equipment, GNSS receivers, and test and measurement systems that require both low clock noise and stable frequency performance.
A voltage-controlled TCXO adds an external frequency-adjustment function to temperature-compensated performance.
At 10 MHz, the YSV350TP can achieve phase noise of −141 dBc/Hz at a 1 kHz offset. It is designed for clock systems that require frequency calibration, synchronization, or fine adjustment.
An OCXO maintains the crystal at a controlled temperature to provide higher frequency stability and very low phase noise.
Available YXC series include:
At 100 MHz, the YOV1409SM can achieve phase noise of −155 dBc/Hz at a 1 kHz offset, with frequency-stability options from ±10 ppb to ±50 ppb.
Selected 10 MHz OCXO series can achieve phase noise as low as −165 dBc/Hz at a 1 kHz offset. These devices are suitable for high-performance communications, precision measurement, and frequency-reference applications.
| Oscillator Type | Recommended Series | Example Phase Noise | Key Selection Value |
|---|---|---|---|
| SPXO | YSO110TR | −153 dBc/Hz at 1 kHz, 24.576 MHz | Fixed-frequency, low-noise clock |
| TCXO | YSO510TP, YSO512ET | −150 dBc/Hz at 1 kHz, 10 MHz | Low phase noise with temperature stability |
| VC-TCXO | YSV350TP | −141 dBc/Hz at 1 kHz, 10 MHz | Temperature compensation with frequency adjustment |
| OCXO | YOV1409SM and other YOV series | Down to −165 dBc/Hz at 1 kHz for selected 10 MHz series | Very low phase noise and high frequency stability |
Phase-noise values should always be compared under the same carrier frequency, offset frequency, output, supply, load, and test conditions.
As communication speeds, data bandwidth, and measurement accuracy increase, oscillator selection is moving beyond nominal frequency and accuracy. Engineers must increasingly evaluate several related parameters:
Low phase noise is not an isolated datasheet specification. It is an important foundation for a clean, stable reference clock in high-speed and high-precision systems.
YXC provides low-phase-noise SPXO, TCXO, VC-TCXO, and OCXO products for different frequency, stability, and phase-noise requirements. Contact the YXC team for detailed specifications and product-selection support.
