CC1125: Intermediate Frequency (IF)

Akash Patel

Part Number: CC1125
Other Parts Discussed in Thread: SMARTRFTM-STUDIO,

Hello,

We are testing the CC1125 using SMARTRFTM-STUDIO with the "Generic 434MHz Bit rate: 1.2kbps, 2-FSK, 12.5 kHz Channel spacing, optimized for sensitivity. (434MHz)" setting.

Looking at pages 13 and 15 in the datasheet (last row in the table), it says "image at -125 kHz." Can we take this to mean that the intermediate frequency (IF) should is 62.5 kHz? Is this a parameter that can be programmed in the device? What is the IFAMP register used for?

Regards,

Akash

over 6 years ago

0 TER over 6 years ago

TI__Guru**** 317180 points

IF programming: 9.13 in www.ti.com/.../swru295e.pdf That said, for this and the IFAMP register, use the settings from SmartRF Studio.

Typically the default IF could be used or no IF is used. The IFAMP register sets the bias current to the IF AMP.

0 Akash Patel over 6 years ago in reply to TER

TI__Expert 6245 points

Hi TER,

Please confirm if the following is correct based on the formula provided:

FREQ_IF = 0x33 = 51 (decimal) (this is from the register setting in SmartRF studio for the setting mentioned in the original post)
F_XOSC = 40 MHz (40 MHz XOSC on the CC1125EM)

f_IF = (40 * 10^6) * (51) / (2^15) = 62,255.859375 = ~ 62.3 kHz

Regards,
Akash

0 TER over 6 years ago in reply to Akash Patel

TI__Guru**** 317180 points

That sounds about right. The IF frequency was designed with high resolution since we didn't know where the sweep spot between 1/f noise and quantization noise would be.

Sub-1 GHz

Sub-1 GHz forum

CC1125: Intermediate Frequency (IF)