Wednesday 27th March 2024
Understanding Quartz Crystals in IoT: Ensuring Wireless Application Performance
IoT, or the Internet of Things, is a term that has become an integral part of today's world.
Wi-Fi, Bluetooth, 5G and many other wireless applications are a daily companion for most people these days.
However, in order for all this to work smoothly, every component must be tailored to the requirements of the wireless sector. This also applies to the small quartz crystals and oscillators that set the pace in many electronic applications. But what exactly is the function of the components in wireless applications? And what needs to be considered when using the small frequency control products in IoT applications?
You can find the answers to these questions and more important information in our technical document.
Jauch Crystals for IoT Applications
Requirements for Crystals in Wireless Applications
Generally, RF (Radio Frequency) circuits transmit and receive radio waves in predefined and narrow frequency bands. To avoid any interference with other frequency bands, and to improve reception sensitivity for long distance transmission, the overall frequency accuracy may be limited to a few tens of ppm’s relative to the specified reference RF frequency.
Most RF receivers or transmitters typically use AT-cut crystals with frequencies in the range of 13.560MHz to 52.0MHz to create a reference frequency that is used to generate RF reception or transmission frequencies at several hundreds of MHz or even in the GHz range.
As the accuracy of the crystal-based reference frequency (measured in ppm) converts to the RF range, strong requirements apply to the frequency accuracy and stability of the reference clock generated by the crystal.
Accordingly, strict specifications may apply to the frequency tolerance, the frequency stability and the aging of the crystal over the expected lifetime of the customer’s product.
Furthermore, the crystal-based reference clock should be free of spurious frequencies, which could cause an unwanted RF transmission at frequencies close to the actual RF trans-mission carrier frequency.
Total “ppm” Budget for Wireless Applications
According to the RF / wireless standards being used, different total “ppm” budgets are valid. Some RF standards require a total “ppm” budget as narrow as +/-20ppm, whereas in others +/-40ppm is
acceptable.
How to meet +/-20ppm “overall” with a Crystal
Some RF-ASICs or RF-SoCs offer the possibility to compensate the frequency tolerance at +25°C and the frequency pulling due to load capacitance tolerance by a module per module frequency compensation.
Two of the frequency compensation methods that can be applied are either the fine-tuning of the frequency synthesizer that generates the RF frequency based on the crystal frequency, or by load capacitance tuning of the built-in crystal load capacitors inside the RF-ASIC.
In case of doubt, the RF-ASIC datasheet should include information which frequency compensation method is recommended by the IC supplier for their RF-chip
Jauch Crystals for IoT Applications
Requirements for Crystals in Wireless Applications
Generally, RF (Radio Frequency) circuits transmit and receive radio waves in predefined and narrow frequency bands. To avoid any interference with other frequency bands, and to improve reception sensitivity for long distance transmission, the overall frequency accuracy may be limited to a few tens of ppm’s relative to the specified reference RF frequency.
Most RF receivers or transmitters typically use AT-cut crystals with frequencies in the range of 13.560MHz to 52.0MHz to create a reference frequency that is used to generate RF reception or transmission frequencies at several hundreds of MHz or even in the GHz range.
As the accuracy of the crystal-based reference frequency (measured in ppm) converts to the RF range, strong requirements apply to the frequency accuracy and stability of the reference clock generated by the crystal.
Accordingly, strict specifications may apply to the frequency tolerance, the frequency stability and the aging of the crystal over the expected lifetime of the customer’s product.
Furthermore, the crystal-based reference clock should be free of spurious frequencies, which could cause an unwanted RF transmission at frequencies close to the actual RF trans-mission carrier frequency.
Total “ppm” Budget for Wireless Applications
According to the RF / wireless standards being used, different total “ppm” budgets are valid. Some RF standards require a total “ppm” budget as narrow as +/-20ppm, whereas in others +/-40ppm is
acceptable.
How to meet +/-20ppm “overall” with a Crystal
If the total “ppm” budget is only +/-20ppm, it means that the overall frequency stability of the MHz reference clock including all contributions like frequency tolerance at +25°C, frequency stability over the operating temp range, long term aging and frequency pulling due to load capacitance tolerance should be kept below +/-20ppm, which isn’t an easy task if using crystals.
Some RF-ASICs or RF-SoCs offer the possibility to compensate the frequency tolerance at +25°C and the frequency pulling due to load capacitance tolerance by a module per module frequency compensation.
Two of the frequency compensation methods that can be applied are either the fine-tuning of the frequency synthesizer that generates the RF frequency based on the crystal frequency, or by load capacitance tuning of the built-in crystal load capacitors inside the RF-ASIC.
In case of doubt, the RF-ASIC datasheet should include information which frequency compensation method is recommended by the IC supplier for their RF-chip
For more information on the Jauch Quartz range please contact our sales team on +353 1 8020044 or email sales@futura.ie
