• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 21 subscribers
  • Views 372 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2615EVM-CVAL: Low output power at high frequencies

Drew Nakamura
Prodigy 50 points
Part Number: LMX2615EVM-CVAL

I'm having trouble with this eval board producing low output power at higher frequencies (14-15GHz). I'm aware that the datasheet plots out the output power for either a 50ohm resistor or 1nH pull-up, but since the eval board comes with a different pull-up configuration I wanted to know if 7.5-12.5dBm output power is even possible. 

I'm currently seeing output power in the range of (-8.5, -5.5)dBm at these frequencies, which is nowhere near close to what I expected based off the datasheet. I'm designing for single-ended operation so I currently have the RFOUTAM connected to a 50ohm termination. RFOUTAP is connected directly to a spectrum analyzer using a barrel to try and minimize any loss. 

I'd be happy to discuss this issue over the phone if that would facilitate a more effective discussion.

Thanks!

  • 0
    TI__Genius 9920 points

    Not sure if LMX2615 datasheet Figure 17 and Figure 18 can answer your concerned.

  • 0 in reply to Shawn Han
    TI__Mastermind 27581 points

    Drew,

    I measure about -5 dBm disregarding losses at these frequencies.

    With matching, this can be improved about 0.8 dB.

    Board losses are substantial and cannot be ignored.  I calculate about 5 dB a these frequencies.  See chart below.

    So accounting for losses and matching, maybe this could be about 1 dBm for resistive pull-up.

    WIth an inductor and a stub tuner, I got a direct measurement of about 5.5 dBm.  Accounting for losses, maybe 10 dBm. 

    See plots for board loss and tuner with inductor.

    Regards,
    Dean