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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator

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rhb:
Very interesting work.  It got me to wondering if one could load a predistorted waveform instead.  I'd like to have a go at it.

Can someone point me to the instructions for loading ARB waveforms?  The thread is so long now we need an index page.

alexvg:
Here is the schematic of the first filter implemented (11th order filter without the compensation filter).


To design the filters, I use :
- Iowa Hills RF Filter Design v2.2 (http://www.iowahills.com/9RFFiltersPage.html)
- RF Tools - LC Filters Design Tool (https://rf-tools.com/lc-filter/)
- LTspice XVII (most of work is done with this software)

To measure the FY6600, I use :
- Rigol DS1054Z (oscilloscope)
- Siglent SSA3021X-TG (spectrum analyzer)
- UNI-T UT181A (multimeter)
- 50R terminators, 20dB attenuator, 2GHz+ BNC/BNC cable...

alexvg:
I've done the new 5th order filter with sorted components : +/-1nH inductances and 0.3% capacitors.
I've changed the 50MHz oscillator with this model : Connor-Winfield D75J-050.0M (+/-1ppm)
https://www.digikey.fr/product-detail/fr/connor-winfield/D75J-050.0M/CW657CT-ND/1965865

The schematic is highly optimized with the components I have and PCB parasitics inductance/capacitor.



This curve result provides 60dB SPUR with the new 5th filter than 50dB with 11th order filter.
Yellow : New 5th order filter
Magenta : 11th order filter


The lineary between new 5th order filter and 11th order filter
The new 5th order filter provides very good linearity for sine signal (+/-0.3dB 0-30MHz) and multitone signal (+/-0.35dB 0-60MHz)
Yellow : New 5th order filter with sine sweep 1MHz to 30MHz
Magenta : 11th order filter with sine sweep 1MHz to 30MHz
Green : New 5th order filter with multitone sweep 1MHz to 12.45MHz
Blue : 11th order filter with multitone sweep 1MHz to 12.45MHz




The rejection of multiple points of this new 5th order filter
125MHz at -32dB
146MHz at -41dB
250MHz at -58dB


The same curve compared to old 11th order filter
Yellow : New 5th order filter
Magenta : Old 11th order filter


1MHz square signal comparison
Yellow : New 5th order filter
Magenta : Old 11th order filter


5MHz square signal comparison
Yellow : New 5th order filter
Magenta : Old 11th order filter


10MHz square signal comparison
Yellow : New 5th order filter
Magenta : Old 11th order filter


25MHz square signal comparison
Yellow : New 5th order filter
Magenta : Old 11th order filter



Conclusion of this new 5th order filter

Pro :
- Simple to implement
- Very good SPUR
- Very good rejection
- Very good linearity

Con :
- The square signal is awfull, probably due to lots of phase variations.

Note:
I use the term SPUR for SPUR, harmonics and artefacts (provides by sine sampling/phase error...)


Next ?
I'm going to remove the implemented new 5th order filter using 0805 SMD.
I'm working on a little more complex 7th order filter using 0603 SMD.
The goal is to provide more better features with a quasi-linear phase (useful for square signal).

alexvg:
I've performed a measurement of the frequency response of provided cables.

Yellow : BNC/BNC short cable
Green : BNC/Banana => Banana/BNC cable.

soundtec:
Theres a new version 6 software become available for the fy6800 from feeltech,looks like it has the firmware update option too ,might try it later on .

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