ADC12DJ3200: S-parameter

Lilian Chang

Part Number: ADC12DJ3200
Other Parts Discussed in Thread: ADC32RF45

Hi Team,

Could you please help to explain what's the S11/S21 stand for in the S-parameter of ADC12DJ3200? If it is same as below picture? My customer want to know the transfer function or flatness of the ADC...

Why S22/S12 is not 0 and same as S11/S21?

In this model, S11 carries information about the ADC’s input impedance (ZIN), whereas S21 carries

information about the ADC’s transfer function when the system (source) impedance is Z0.

over 7 years ago

0 Brian Kincaid over 7 years ago

TI__Intellectual 2750 points

Lilian,
I have forwarded your question to an engineer familiar with this device.
Regards,
Brian

0 Jim Brinkhurst1 over 7 years ago in reply to Brian Kincaid

TI__Mastermind 44680 points

Hi Lilian

Sorry for the delay in responding. I have discussed this in more detail with the engineer who created the .s2p file that I sent you. That measurement was done using a different methodology than was used for the ADC32RF45 s-parameter application note you are referring to. (http://www.ti.com/lit/pdf/sbaa219)

In the ADC12DJ3200 .s2p measurement the INA+ and INA- ports are considered ports 1 and 2 for a 2-port, single-ended measurement approach. Here is what the notations mean:

The ADC32RF45 model parameter S11 is actually the input return loss for the differential input. This is usually referred to as SDD11 in most literature. These methodology and terminology differences explain why the S22 and S12 values for the ADC12DJ3200 .s2p file are not set to 0 as done in the ADC32RF45 s-parameter document. (http://www.ti.com/lit/pdf/sbaa219)

I hope this is helpful.

Best regards,

Jim B

0 Lilian Chang over 7 years ago in reply to Jim Brinkhurst1

TI__Intellectual 1555 points

Hi Jim,

So many thanks for your explanation.

As your mentioned, in the ADC12DJ3200 .s2p measurement S21 is energy transferred from INA+ to INA- , so do we have s-parameter of ADC transform function like which is defined as in ADC32RF45 model?

Because my customer want to use the s-parameter of transfer function to design the external matching.

0 Jim Brinkhurst1 over 7 years ago in reply to Lilian Chang

TI__Mastermind 44680 points

Hi Lilian

Here is SDD11 data (input return loss data for the differential analog input port) based on the earlier .s2p file.

/cfs-file/__key/communityserver-discussions-components-files/73/1348.ADC12DJ2700_5F00_TRMCalibration_5F00_Sdd11_5F00_031716.txt

Hopefully this is helpful to the customer.

Best regards,

Jim B

0 Lilian Chang over 7 years ago in reply to Jim Brinkhurst1

TI__Intellectual 1555 points

Hi Jim,

Thanks for your reply.

I don't think SDD11 data (input return loss data for the differential analog input port) is what we want...

Can find information about equivalent NW model or transfer function of ADC12DJ3200 like which is identified in ADC32RF45 ?

0 Jim Brinkhurst1 over 7 years ago in reply to Lilian Chang

TI__Mastermind 44680 points

Hi Lilian
We don't have a model in exactly the same form as what is given in the S-parameter document for the ADC32RF45. Please also note that the matching technique covered in that document is applicable over a relatively narrow frequency range (1700 to 2000 MHz or 1500 to 2100 MHz). What frequency range is the customer trying to optimize in their ADC12DJ3200 application?
Best regards,
Jim B

0 Jim Brinkhurst1 over 7 years ago in reply to Jim Brinkhurst1

TI__Mastermind 44680 points

Hi Lilian

Per our discussion off-line, if the customer only needs to capture signals up to 3 GHz then the ADC amplitude response is likely flat enough and no matching network is needed. This will also depend on the performance of the balun selected over that frequency range.

Best regards,

Jim B

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ADC12DJ3200: S-parameter