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Part Number: CC1120
I have a problem with the reception of a 169Mhz radio equipped with a CC1120. In particular, I cannot understand if the received packet has a frequency that deviates slightly from the one set.
Is it possible to detect this deviation from the set frequency?
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Are you referring to frequency offset or frequency deviation (modulation parameter)?
The frequency can be offset due to too large crystal tolerance or incorrect load capacitance on the HF crystal.
The best way to measure the accuracy of the HF crystal oscillator is to output an unmodulated carrier wave from the radio and measuring the frequency offset from the wanted frequency using a spectrum analyzer. The relative offset of crystal frequency, typically stated in Parts per Million (ppm), is the same as the relative offset of the RF carrier.
Best Regards, Eirik Please refer to the resources and abbreviations below for explanations and answers to many questions.
SLA - Simplelink Academy, SCS - Sensor Controller Studio, SC - Sensor Controller, TI Cloud Tools, Resource Explorer, Bluetooth low energy software stack, Bluetooth low energy software stack archive, TI BLE Wiki (OLD), BLE Getting Started and FAQ, CC1352R and CC26x2R Intro, Bluetooth SIG Core Spec, CC2640R2F SDG, CC26X2 SDG, CC2650/CC2640 SDG, BLE PACKET SNIFFER
In reply to Eirik V:
I think I did something wrong in the exchange of messages.
Now I have posted a small doc which I hope is clearer.
In reply to Luca Filippucci:
The chip calculates an estimate of the frequency offset in the register FREQOFF_EST. This estimate is calculated when receiving a SYNC word. Hence only small offsets is possible to compensate with this method since the signal has to fit the receiver bandwidth. Therefore the received bandwidth must be large enough to cover the offset which might impact receiver sensitivity.
Refer to this thread for more info:
I have inserted in my code the reading of the FREQOFF_EST0 and FREQOFF_EST1 registers.
My FREQOFF_CFG register is set to 0x22
Doing TX / RX tests trying to keep the Test environment unchanged
I send and receive 7 packets with this configuration:
Centre frequency [MHz]
Channel spacing [kHz]
Frequency tolerance [± kHz]
After receiving the SYNCH word, the registers assume the values below:
How do I interpret the registers?Best Regards.Luca
Please refer to FREQOFF_EST1 in the User’s Guide (SWRU295E)
FREQOFF_EST is given in 2's complement form which means that
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