TRF370417: Tale signal after the fall edge

Enbo Zhang

Part Number: TRF370417

Dear TI Tech support,

I bought a TRF370417 IQ modulator recently and trying to use it together with a pulse generator to gate an RF sine wave(as shown in the first attached image). But I got two weird tale signals after each pulse(second image).

The I/Q are connected to a TTL pulse generator(3.3V output), and the RF signal is generated by a signal generator. I believe the input and output RF cables are all 50Ohm so the impedance should match. Could you help me take a look at the problem?

Any help will be greatly appreciated!!

Thanks,

Enbo

over 2 years ago

0 Kang Hsia over 2 years ago

TI__Guru 65864 points

Enbo,

Please do check the input waveform if there are any transients. You will need to make sure your pulse input does not have any ringing.

0 Enbo Zhang over 2 years ago in reply to Kang Hsia

Prodigy 10 points

Hi Kang,

Thank you very much for the quick response. The attached image is shows the 100ns input pulse for I. There are about 10-20ns unstable signal after the rise and fall edge. Do you think this is the reason of the tale signals as described above?

+1 Kang Hsia over 2 years ago in reply to Enbo Zhang

TI__Guru 65864 points

Hi Enbo,

yes, possibly. These are simply ringing. You may need to make sure there are slew rate control going into the pulse, and the pulse control is "coherent" with the rising of the signal so there are no early/late effects of the pulse.

These ringing will be modulated into RF frequency, and therefore, may be more drastic on the RF spectrum

0 Kang Hsia over 2 years ago in reply to Kang Hsia

TI__Guru 65864 points

also, I noticed you are input 3.3V I/O, this may exceed the P1dB point of the modulator.

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TRF370417: Tale signal after the fall edge