[DEMO BGT60TR13C] How to select an appropriate value of if_gain_dB

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Frank-W
Level 2
Level 2
25 sign-ins 10 replies posted 5 questions asked

Hello,

Could you please share some background knowledge of "if_gain_db", one of the sensor configuration parameters? 

I got some description as follows from one of the header files. My gut feeling tells me to pick 60 dB to get IF signal greatly amplified before being fed to ADC. However, one of your infineon examples picked 33 dB. What is the tradeoff strategy that we should keep in mind when selecting an appropriate value for if_gain_dB

if_gain_dB: applied to the IF signal before sampling. Valid range is [18 - 60]dB
 
Best regards,
/Frank
 
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Deepa_V
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First comment on KBA 50 likes received 250 replies posted

Hi @Frank-W ,

Apologies for the delay in response !

'if_gain_dB' is the amplification factor that is applied to the IF signal coming from the RF mixer before it is fed into the ADC (allowed values in the range [18,60]).

Internally, the values for HP gain (possible values: 18dB, 30dB) and VGA gain (possible values: 0dB, 5dB, 10dB, ..., 30dB) are computed from if_gain_dB. HP gain is chosen as high and VGA gain is chosen as low as possible to reduce noise. HP gain is 18dB if_gain_dB is less than 30, otherwise HP gain is 30dB. VGA gain is chosen such that the sum of HP gain and VGA gain is as close to if_gain_dB as possible.

Also, note that it is not possible to set all values of if_gain_dB exactly. The configured value and actually set value of if_gain_dB might differ by up to 2dB.

Hope this helps !

Best Regards,

Deepa

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Deepa_V
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First comment on KBA 50 likes received 250 replies posted

Hi @Frank-W ,

Apologies for the delay in response !

'if_gain_dB' is the amplification factor that is applied to the IF signal coming from the RF mixer before it is fed into the ADC (allowed values in the range [18,60]).

Internally, the values for HP gain (possible values: 18dB, 30dB) and VGA gain (possible values: 0dB, 5dB, 10dB, ..., 30dB) are computed from if_gain_dB. HP gain is chosen as high and VGA gain is chosen as low as possible to reduce noise. HP gain is 18dB if_gain_dB is less than 30, otherwise HP gain is 30dB. VGA gain is chosen such that the sum of HP gain and VGA gain is as close to if_gain_dB as possible.

Also, note that it is not possible to set all values of if_gain_dB exactly. The configured value and actually set value of if_gain_dB might differ by up to 2dB.

Hope this helps !

Best Regards,

Deepa

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Hello Deepa,

Thanks for your reply.  I just found what you described in the specification of BGT60ATR24C. It would be great to have the same information cloned into the spec of BGT60TR13C.

What is VGA? I thought it was the abbreviation of variable programmable amplifier. However, the attached screenshot states it is a low noise voltage gain amplifier.  Or Does the gain consists of both low noise voltage gain amplier ( 1st gain stage with the choice of 18 or 30 db) + variable programmable amplifier (0, 5, 10 ...30 db)? and the VGA abbr. applies to both amplifiers?

Best regards,

/Frank

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Deepa_V
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First comment on KBA 50 likes received 250 replies posted

Hi @Frank-W ,

As stated before, 'if_gain_dB' is the amplification factor that is applied to the IF signal coming from the RF mixer before it is fed into the ADC. More specifically, it's the amplification factor attained by the signal while it passes through the analog baseband (Please refer Figure 4 of the BGT60TR13C_Datasheet_V2.4.6) which consists of the  high pass filter (HPF), VGA and anti-aliasing filter (AAF). VGA is basically a low noise voltage gain amplifier and I suppose you are confusing the term with PGA which is Programmable Gain Amplifier. Please note that the VGA gain in this case is also variable and programmable through SPI. 

Best Regards,

Deepa

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