CC1101-Q1: Additional RF parameters needed on this part

Curious: I doubt that TI want to share all this data, why not base your evaluation on the selectivity curves in the datasheet? The performance should not be dependent on the frequency range you are operating in. 

Hi Rob,

We cannot provide most of these parameters to costumers. I am not sure why you are asking for them. What are you trying to do with these numbers? If you want to know the interference tolerance of the device you should look at the selectivity and blocking numbers and curves in the datasheet.

Best regards,

Haiatullah G.

I am asking for this data because its not in the datasheet and its needed to fully optimize the application to be robust against interference at nearby frequencies much stronger than the desired signal and at harmonics of the Local Oscillator where this type of receiver with a very low IF Frequency can be sensitive. The result of this will determine how much signal filtering is needed up front.

Hi,

CC1101 has been used for many years in a variety of noisy and non-noisy RF environments around the world.

Can you please specify which type of RF interference you are referring to (frequency, power level and time duration) ?

Regards,

  Richard

Richard:

My application is required to receive signals in the -80 to -95 dBm range while rejecting any nearby signal that could be as high as -30 dBm... This would require an SFDR of over 70 dB which I am not sure this part is capable of.  The application Frequency is 433.92 MHz so knowing the sensitivity to harmonics of the L.O. will help in designing the front end filter - several of the cell phone bands worldwide fall into these ranges and there could be a cell signal received that is much stronger than the desired signal which again drives the need for SFDR to be as high as possible.

The signal is FSK, 19200 baud, Manchester encoded with 38 KHz deviation currently.  Application is on a Semi Truck for tire system monitoring so one interference case is the driver being on the cell phone which is close to the receiver...

Another issue I am having with the part is that the PLL will not go to 433.92 MHz and becomes very unstable above 408 MHz - any idea what could cause this?  It works fine at 406.800 MHz with a 0x0F0000 frequency setting and a 27.1200 MHz crystal but not at the required 0x100000 setting which yields about 408.8 MHz and a lot of sidebands that show instability.  I have the required 100 nF decoupling capacitors and a tight PCB layout so that should not be the culprit.  the Crystal is showing correct frequency and well within its 30 ppm tolerance as measured on a Rode & Schwarz RF analyzer.

FYI - we are not using the Transmit in the application but I am using it for debug purpose at -30 dBm power level.

Please advise on this second issue - I will characterize the receiver once I get the frequency corrected.

Regards,

Rob

BGM Engineering Services

Question: 27.12 MHz is outside the spec for xtal, why?

I was not able to get a 27.000 MHz and 27.12 MHz should work with a slightly different register value as its 0.44% different.  It would still be within the specified frequency range in the datasheet.  This part should not be that sensitive....

Hi Rob,

This device will not be able to receive a signal if there an interferer that is 70 dB above the signal level. That is what the selectivity and blocking performance in the datasheet indicates. We have other devices like CC1120 that can do this if the interferer signal is ≥2 MHz away from your wanted signal.

On your second question, TI does not guarantee any of the specs in the datasheet if a component outside of the recommended range is used. You can use a crystal with frequency within 26 MHz to 27 MHz for this device. Couldn't you get one in this frequency range? 

Best regards,

Haiatullah G.