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Cable and BPF ( Signal Generator)

swimming3744
Prodigy 160 points
Other Parts Discussed in Thread: ADS5295

Hi Everyone !

I have an ADS5295 evm and TSW1400 evm and i'm capturing data from a signal generator, however, the cable (BNC-SMA) i'm using doesn't have a Band pass filter (BPF). Therefore, i guess i'm not getting good results when capturing some signals :

Sine signal

Square signal

Ramp signal


So, Where can i get or order this cable with a BPF ? , What are the specifications of the BPF ?, I would appreciate any suggestions or comments. Thanks !

Regards,

Ian 

  • 0
    TI__Mastermind 29220 points

    Hi,

    I am moving this post to the medical forum because that device is supported by that group.  I would suggest also that you take a look at the part number of the transformer coupling on your EVM and look up the datasheet for that transformer.  The last plot at 150K would be much too low a frequency for the passband of the transformer, although that usually just means a loss of amplitude, not a distortion.  A square wave have some 'droop' to it if the frequency were too low for the AC coupling, but the other two plots at 1M should not be too low i would think.  A bandpass filter would turn any of these signals into a sine wave after the harmonics of the fundamental are removed, however.  (In the high speed group, we will usually use an LC bandpass filter with a passband of 3% or 5% from a vendor such as TTE.)

    Regards,

    Richard P.

  • 0 in reply to Richard Prentice
    TI__Genius 14540 points

    Hi,

    Bandpass filtering a single tone sinusoidal input signal can help performance and is recommended.  However, the filter can only do so much and the performance of the signal generator is a huge factor.

    As Richard stated, applying a square wave or ramp pattern to a bandpass filtered input would convert such signals into sinusoidal signals.  

    For our device characterization we use filters from TTE such as the ones shown below:

    Thanks,

    Christian