ADS42JB46: Why input analog bandwidth is larger than sample rate

Hi Kang,

About question one, I know undersample, but the input bandwidth should less than sample rate I think, such as input frequencies are 800~900 MHz and sample rate is higher than 200 Msps,,, such a process is undersampling, right?

But for ADS42JB46, the input bandwidth is 0~900 MHz, how undersampling works? I think it will appear alias on the first Nyquist region and appear failures.

Regards,

Nan

Hi Kang,

About question two, uh,,, if the SYNC is handshaking signal, so how this signal output from ADS42JB46, because there is no SYNC out ports except SYNC in ports, the SYNC signal will be included in the ILA section?

By the way, I'm sorry. I don't find the handshaking progress of SYNC from above link, can you show more details?

Thanks!

Regards,

Nan

Nan,

please review the app note. The wider input bandwidth can support 800 to 900MHz of RF input.

Hi Kang,

Yes I know that SYNC should come from FPGA( Receiver) to ADC( Transmitter), 

So my question is how SYNC "request" transfer from ADC to FPGA,,,, because I don't find any I/O ports to do this.

Regards,

Nan

Hi Kang,

Sorry I didn't make it clear. My question is that if input bandwidth( such as 600~900 MHz) is larger than sample rate( 200 Msps),

the ADC will not restructure the original signal properly although undersample the analog signal, because it violates the sample principle,,,,,

Regards,

Nan

Hi Kang,

The all thing I have seen shows that only transmitter can receive SYNC request, but in ADS42JB46 datasheet, I can't understand why this ADC can "generate" a SYNC request,,,, because there is no relational I/O ports to realize this function.

Hi Kang,

So why the input bandwidth is 900MHz, this bandwidth value is larger than ADS42JB46's sample rate,,, I don't know why?

Hi Kang,

So the bandwidth 900MHz, means that the MAX frequency I can detect is 900MHz, but not 0~900MHz, right?

For example, if the input analog is between 900MHz~1000MHz, this ADC will not work normally, right?

It can not support input frequency which is higher than 900MHz, right?

Hi Kang,

Yes, I know your answer, but I just confused with the values this figure shows, I thinks there is something wrong when you write this form.

Regards,

Nan

Hi Kang,

The confusion is here:

ADS42JB46 data sheet, product information and support | TI.com

I get your answer I think, like this:

If my figure is right, my confusion is that why this 160 Msps ADC has such a wide input analog bandwidth.

And my point is that if the input frequency is higher than 900MHz, the input signal amplitude will lower than full-scale minus 3 dB, so the signal can not be sampled properly.

Hi Kang,

Yes, I get your answer, which means the valid or proper input frequencies range this ADC can sample is between 0~900 MHz, and after 900 MHz, the sample information will be bad.

In your figure, you show me that some single frequency points like 70/170/230 MHz, for single frequency , this ADC with 160 Msps can work well.

My point is that if the input bandwidth is lower than 160Msps/2 (80 MHz), meanwhile the MAX frequency lower than 900 MHz, such as 100~180MHz, 800~880MHz, but not 900~980MHz,,,,,,,,,,,this ADC will work well.

Regards,

Nan