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TSW1265EVM: TSW 1266

Part Number: TSW1265EVM
Other Parts Discussed in Thread: LMK04808,

I use a TSW 3085 as Tx and a TSW 1266 as Rx. Following the example of evaluate madule and using LMK04808_614p4M_Single_Loop.txt. in TSW 1266 GUI I had a good result in the Rx as shown in the figure

Changing the LO frequency from 2.6 GHz to 500 MHz the spectrum got many repetitions and some carriers polluting the visualization as shown in the figure.

Which option can I change in TSW 1266 GUI to work with lower frequencies in LO?

  • Based on the plot enclosed and the LO frequency of 2600 MHz, I ascertain that your input RF frequency is about 2046.9 MHz. 

    The user's guide states the default RF input range is 1880 MHz - 2390 MHz.  The default LO is 2600 MHz.  The IF is 460.8 MHz +/- 250 MHz.  Your initial performance set-up is within those guidelines and it looks like the EVM is working within expectations.

    When you switch to a 500 MHz LO, how is your input signal changing?  If it did not change, then the IF frequency will be way off and outside the designed filter BW.  It sort-of looks like the RF was changed to something like 446 MHz (or 554 MHz).  In any event, the IF is still off.  What you are seeing in your spectrum is the 500 MHz LO bleed-through getting captured at the ADC (that's the 114 MHz signal).  Then you are seeing what look like the signal/image at LO +/- 54 MHz.  The other CW tones are harmonics of the LO bleed-through.  There is also an image or harmonic of the signal itself.

    In short, the board is not set-up for that type of LO frequency.  If your signal truly is around 500 MHz then you could simply use the ADC to capture the signal directly without the need for the demodulator to convert it to a lower frequency.


  • Thanks for the answer.

    Which option should I change in the TSW1266 GUI to capture the signal without an LO?

    For a 500M capture without an LO? should I change the sampling rate to 1.2288 GHz?

  • Check out the schematic of the TSW1265.  You can download it from the TSW1265EVM product page on  A copy of the relevant section is pasted below for reference.

    You can bypass the mixer and inject directly at the IF frequency.  For channel A, you would need to make some solder modifications to the board.

    • Remove R118, R8, R54
    • Place R71, R9

    Then you can inject signal at J10 connector (SMP).  You can inject at 500 MHz directly; there is no need to change the sampling rate.  You can operate the ADC in a higher Nyquist zone.


  • Thank you very much,
    In my application I export the 32000 data received into a .csv file using a TSW 1266 as receiver. Because of this a very high sampling rate would not be ideal.

    Seeing the mentioned documentation I saw that one can change the components to support other frequency bands for the oscillator LO and RF receiver. Can I design a filter to operate at 500 MHz by replacing the tsw 1266 components?

  • Sorry, I miss-typed before.  I meant to look at the schematic of the TSW1266 which is on the TSW1266EVM product page.  I hope that was not your confusion.

    The TSW1266 already has an IF filter of 460.8 MHz +/- 250 MHz so you can pass a 500 MHz signal without issue.  If you need/want a different filter or a narrower band filter, then you may adjust the filter components accordingly.


  • In my application I will have to use an LO.

    In this doc:, in section 3.3.2 the author talks about changing the filters to change the RF and LO oscillator input frequency bands . Section 3.3.1 provides a filter design tool.

    This documentation:, shows the schematic of the TSW 1266.

    As you wrote, I think it may be these filters that cause the error when I use a LO oscillator with a frequency of 500 MHz.

    I would like to confirm that the filters that will determine this range are positioned just after connector J4 (For LO) and J2 (For RF input).

  • Yes, but some others as well:

    • Yes, you will likely need/want to modify filter/match on the RF input (just after J2 connector)
    • Yes, you will likely need/want to modify filter/match on the LO input (just after J4 connector)
    • You may want to change the balun.  BD0826J50200A00 is rated 800 MHz to 2600 MHz.

    The changes above may not be super critical.  If you come in at a lower frequency than originally intended then the match may not be optimized for the different frequency, but everything will still work.  You will likely see a reduction in gain due to the mis-match on the RF and LO ports.

    Here is the other kicker: the new IF frequency.  The board is configured with an IF frequency of 460.8 MHz +/- 250 MHz.  If your new IF is outside of that window then the IF filter must be modified.  This would need modifications on the filter before and after the LMH device.  If the IF is within the filter window then the signal will pass; however, then your leakage signals (i.e. RF and LO) will pass too and likely cause some problems with unwanted spurious.