CC1120 spurious at XOSC/2

Axel Lavroche

Other Parts Discussed in Thread: CC1175, CC1120

Hello,

For a specific utilisation I use a CC1120 and a CC1175 on a same board and i've some trouble with some spurious at each XOSC/2 : Each 16MHz i've a big spurious that degrades the sensivity of my product.

I've already read the datasheet and i've seen the warning concerning this specific point.

My question is : Is there some tip to reduce the value of this spurious?

Thanks in advance, Best regards, Fabien

over 10 years ago

0 TER over 10 years ago

TI__Guru**** 317180 points

It's limited what you can do about the value but you can try to see if there is a crystal frequency that moves the spurious out of the band(s) of interest.

0 Axel Lavroche over 10 years ago in reply to TER

Prodigy 130 points

Thanks for jour answer. We use the chip in order to do some hopping frequency device with a 30MHz band so we need to block some specific frequencies and it's complicated...

0 TER over 10 years ago in reply to Axel Lavroche

TI__Guru**** 317180 points

Is it acceptable with a given performance degradation for some channels and if so, how much? Which datarate, deviation, rx badwidth are you using?

0 Axel Lavroche over 10 years ago in reply to TER

Prodigy 130 points

We loose at the worst case 30db of sensitivity. Spurious are approximatively at -70dbm after an extern lna...

I'm surprising by the Level of these spurious...reason of my question... Perhaps i've do some mistakes concerning the routing of my board...

Thanks for your answer

0 Sverre over 10 years ago in reply to Axel Lavroche

TI__Mastermind 39860 points

The degradation in sensitivity gets worse at lower RX filter BW.

We measured the degradation some time ago as:

1.2 kbps, 10.9 kHz BW: 28 dB

38.4 kbps, 104 kHz BW: 13 dB

50 kbps, 104 kHz BW: 12.5 dB

100 kbps, 208 kHz BW: 11 dB

500 kbps, 833 kHz BW: 4.5 dB

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CC1120 spurious at XOSC/2