LMX8410L: lmx8410l

Dear Praveen, I have forwarded your request to one engineer to help you out. thank you for your patience. Regards, Simon.

Praveen,

Can you describe the scenario more? For example:

- at 7000MHz VCO and RF at 7100MHz, can see the 100MHz at IF

- changed to 8000MHz VCO and RF at 8100MHz but don't see 100MHz IF

When in internal LO mode, the settings for below 7500MHz and above 7500MHz are different. A few questions:

- you are using the LMX8410LEVM?

- in TICS Pro, you entered the desired frequency in "LO (MHz)" box and pressed [CTRL+L] on your keyboard to set the frequencies?

- which customer is this? 

Yes am using LMX8410EVM.
I had used an IF BW of 25MHz.
But till 7500MHz with internal LO the tics pro settings are good (RF = 7525MHz)
After 7500MHz What are the settings we have to make in TICS PRO ?

When we change it to EXTERNAL LO mode, In the DATASHEET they gave as some modifications had to be made. But in the user guide they didn`t gave any modifications. what i had to do ?

sorry LMX8410LEVM

Praveen,

The VCO on the board tunes from 7500 to 15000 MHz

Now it sounds that perhaps you have this set up where the VCO frequency is divided by 2 to create 3750 to 7500 MHz. You increase the frequency and get up to 7525 MHz, which perhaps sound like the VCO is more like at 1560 MHz, which is likely the true upper range of the VCO.

Below 7500 MHz, we use the divide by 2 to create the quadrature phase. Above 7500, we use a poly filter. These require setup changes. The TICSPro gui should automatically do this if you go to the main PLL gui and choose "Internal PLL to Mixer" from the drop down box in the main setup.

When you change the LO frequency, it should automatically do this setup. Now maybe you are changing the VCO frequency and the GUI won'd do the automatic setup for this way.

Regards,
Dean

If the GUI is unable to tune by itself what we have to do ?
And when i connect in EXTERNAL LO mode it is showing harmonics, when i get IF range from 25-225MHz. What settings had to be made to remove this harmonics ?

Praveen,

On the LO tab, for the "Internal LO to Mixer", the boxes change with LO frequency, this is what I was talking about before.

For the "External LO to Mixer", the GUI directs the LO input through the "Direct Path" to the polyphase generator. I don't think that the settings change based on the LO frequency.

Now on the "Mixer" tab, there are additional gain and phase adjustments that can be made that could very well impact these harmonics, but I do not know how to use them.

Regards,

Dean

I had changed all those settings and achieved enough power at the IF out. But this harmonics are creating issue. i need to vary IF from 25-225MHz.
But these harmonics are coming within the band like when IF =25MHz, harmonics are at 50,75 and so on. I cannot use filters in the INBAND range. How can i solve this problem ?

Praveen,

There are a few updates we're trying to make in the GUI. Sorry that it has been causing you trouble.

On the harmonics side, the IF amplifier has adjustments that could be made for the bandwidth, but there aren't high order cut-offs at these bandwidth frequencies that would be needed to really cut out harmonics. Harmonics would mainly be from either the RF signal or the LO source. Few clarifying questions:

- you are seeing these harmonics with both internal and external mode?

- what levels are you seeing in the 50, 75MHz harmonics?

- what levels do you need to have the harmonics under?

Regards,

Brian Wang

ya i had seen the harmonics during both the internal and external LO mode.
50MHz harmonic is at 30dBc, 75MHz harmonic is at around 43dBc,
I need harmonics to be at 65dBc.

My LO is signal is clear. Am feeding it through LMX2595. And RF signal is through LMX2594.

Praveen,

That is about the harmonic level of LMX2594. I assume you have LO clear as in LMX2595 is filtered, but RF signal with LMX2594 is not filtered right?

Also, please standby on the GUI, we are making a fix and update hopefully by early next week.

Thanks!

Regards,

Brian Wang

NO i don`t  think so, because i had used filters at the RF stage and when i feed this RF signal to other IQ Demodulator from AD. That is not producing any harmonics.

I had a question.

There are no filters at the output of the mixers then how the harmonics produced at the output of the mixer gets reduced ?