The Relationship between RF Radio Frequency Equipment and Crystal and Oscillator

Radio frequency refers to radio frequency current, referred to as RF, the English full name is Radio Frequency, which is the abbreviation of a high-frequency alternating current electromagnetic wave. 

The commonly used crystal frequency of RF radio frequency are 13.56MHZ, 19.2MHZ, 24.576MHZ, 26MHZ, 27.12MHZ, 38.4MHZ, etc. 

To ensure a smooth and stable RF signal connection, variables such as crystal frequency deviation at both ends of the receiver, crystal oscillator TS value, and receiver data rate must be considered. Sensitivity (TS), also known as traction value, represents the change of crystal frequency with the change of load capacitance, and the unit is expressed in PPM/PF.

Crystal frequency deviation and TS value: Frequency deviation > data rate, but requires space for TS offset. The TS value is not as large as possible, but requires a reasonable specified range. Due to the difference in the manufacturing process, the TS value of the same type of crystal oscillator produced by different crystal oscillator manufacturers is different.

Receiver Baseband Bandwidth (BBBW): Defined by crystal accuracy and range requirements, the longer the range required, the smaller the BBBW recommends.

Data rate - defined by the application and needs to be optimized:

• Low data rate -> longer range (better receiver sensitivity)

• High data rates -> shorter packet times -> longer battery life

Note：

1. If there is a frequency offset between the transmitter (RF transmitter) and the receiver (RF receiver), the baseband frequencies of logic 0 and 1 will be different. For small offsets, if the ideal offset is chosen correctly, both the logic 0 frequency and the logic 1 frequency will fit the receiver baseband filter characteristics.

2. If the crystal quartz oscillator accuracy is not enough, or the TS value pulling value is not up to standard, the actual frequency offset of the oscillator quartz may be larger than the range that can be tolerated by the receiver baseband filter. In this case, there may be a signal interruption problem between the RF transceiver equipment.

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