IWR1843: Noise Figure of LNA of receiver block

Hi,

We typically assume 25C for the system temperature, and we don't provide the noise figure to individual components without our silicon, so I cannot provide you with the LNA noise figure. The link budget equation uses the overall system's noise figure, so it shouldn't be necessary for link budget calculations.

Best,

Nate

Hello Nate,

Thank you for reply.
I understand that you cannot provide the LNA noise figure.
Let me ask you more question.
I would like to estimate rough SNR using the above formula.

Please see the following link;
www.docsity.com/.../
1) IWR1843
It is indicated "Noise figure = 15dB(77 to 81GHz)" on Page28 of IWR1843's datasheet.
Is "Noise figure = 15dB" the noise figure of the overall receiver of IWR1843 excluding antenna(Ta)?

2) IWR1843AOP
It is indicated "Effective isotropic noise figure = 10dB" on Page32 of IWR1843AOP's datasheet.
Is "Effective isotropic noise figure = 10dB" the noise figure of the overall receiver of IWR1843AOP excluding antenna(Ta)?
Please let me know the definition of "Effective isotropic noise figure".

3) If you have any document about SNR calculation of TI's radar, please let me know.

Please advise.
Thank you,
Shoko

Shoko Sakaguchi said:

Is "Noise figure = 15dB" the noise figure of the overall receiver of IWR1843 excluding antenna(Ta)?

Yes. Since antenna is not a part of the IWRL1843, it is not included in the noise figure.

Shoko Sakaguchi said:

Is "Effective isotropic noise figure = 10dB" the noise figure of the overall receiver of IWR1843AOP excluding antenna(Ta)?

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1192287/iwr6843aop-what-does-effective-isotropic-noise-figure-mean

Best,

Nate

Hello, 

Thanks for reply. 

Regarding IWR1843's Noise figure = 15dB(77 to 81GHz), you said: 

> Since antenna is not a part of the IWRL1843, it is not included in the noise figure. 

Thus, IWR1843's Receiver Noise figure is 15dB. 

Regarding IWR1843AOP's Effective isotropic noise figure = 10dB, TI said: 

> (Effective isotropic noise figure) = (Receiver Noise figure) + (Antenna gain) - (Losses) 

Assuming that Antenna gain is 7dBi and Losses is 1dB, 
IWR1843AOP's Receiver Noise figure will be 4dB. 

What is the large difference of these Receiver Noise figure? 

I understand that the receiver block in IC between IWR1843 and IWR1843AOP are considered equivalent. 

And, I think that IWR1843AOP's the value of Antenna gain and Losses are suitable. 

Please advise. 

Regards, 

Shoko

Hi,

I agree that this seems odd that there would be a discrepancy of this size. Let me check with colleagues internally and get back to you in 24 hours. If you do not hear back, feel free to post on this thread.

Best,

Nate

Hi,

By definition of noise figure, NF = SNRin/SNRout. Since the antenna gain of the AOP package is about 5 dB, that is likely the cause of the difference.

Best,

Nate

Hello, 

I cannot understand the cause of the difference you say. 

Please explain it with more details. 

Thanks, Shoko 

Hi Shoko,

The Noise figure is determined by the ratio of Input SNR / Output SNR

https://en.wikipedia.org/wiki/Noise_figure

When the EINF is calculated, it gets 5 dB of signal gain from the gain of the antenna. So, the output SNR increases by 5 dB. Therefore, the EINF is 5 dB lower than the NF because it gets to use the antenna gain.

Best,

Nate

Hello, 

Thank you for reply. 

I understand what you mean. 

Let me confirm to make sure; 

- (Effective isotropic noise figure) = (Receiver Noise figure) + (Antenna gain) - (Losses)  This formula is incorrect. 

- Receiver Noise figure of both IWR1843 and IWR1843AOP is 15dB. 

Please advise. 

Regards, 

Shoko 

Hello, 

Thanks for reply. 

(Effective isotropic noise figure) = (Receiver Noise figure) - (Antenna gain) + (Losses) 

(Receiver Noise figure) = (Effective isotropic noise figure) + (Antenna gain) - (Losses) 

Assuming that Antenna gain is 7dBi and Losses is 1dB, 

IWR1843AOP's Receiver Noise figure = 10dB + 7dBi -1dB = 16dB 

Thank you, 

Shoko