what is the nRF52840 in band image frequency for SIG RX C/I test and why?

RE: what is the nRF52840 in band image frequency for SIG RX C/I test and why?

Frank Nie — Thu, 29 Jun 2023 07:35:38 GMT

Hi Ketiljo,

Thanks for your confirm, I'm already fully clear for this question, thanks again!

RE: what is the nRF52840 in band image frequency for SIG RX C/I test and why?

ketiljo — Thu, 29 Jun 2023 07:23:44 GMT

Hi Frank

Sorry, there was a typo. The LO is at fRX - 2 MHz in 2 Mbps mode. So low side injection, direct conversion with only one IF at 2 MHz.

nRF51 is a a superheterodyne receiver with high side injection and 2 IF frequencies.

RE: what is the nRF52840 in band image frequency for SIG RX C/I test and why?

Frank Nie — Wed, 28 Jun 2023 15:32:36 GMT

so, the nRF52 radio receiver is superheterodyne low-side injection(fLO<fRX); and the nRF51 radio is superheterodyne high-side injection(fLO>fRX),that's why nRF51 radio image frequency is fRX+4MHz, nRF52 radio is fRX -2 MHz/4MHz for 1Mbps/2Mbps. right?

RE: what is the nRF52840 in band image frequency for SIG RX C/I test and why?

Frank Nie — Wed, 28 Jun 2023 14:54:44 GMT

Hi Ketiljo,

thanks for your kindly reply,

for "The LO is always at fRX + MHz in 2 Mbps mode on all nRF52 radios" suppose should be" fRX - 2MHz in 2 Mbps"?

fIF (intermediate frequency) is 2MHz in 2 Mbps mode, and fIF is 1MHz in 1 Mbps mode, so image frequency is fRX - 2MHz in 1 Mbps, below is my understanding about the relation among fRX,fIF & fIM, pls correct me if I'm wrong, thanks!

RE: what is the nRF52840 in band image frequency for SIG RX C/I test and why?

ketiljo — Tue, 27 Jun 2023 13:59:20 GMT

Hi Frank

The LO is always at fRX + 2 MHz in 2 Mbps mode on all nRF52 radios. So you will always find the image frequency at fRX - 4 MHz.