DDS questions

The performance is clearly superior to the ICOM. Congratulations.

I am absolutely amazed by the quantity and quality of your documentation. This would take a normal human a year to complete.

I'm interested. Can you name some of the best and who sells them?

LMX2820 (TI) and 8V97003 (Renesas) are two of the best integrated PLL/VCO parts I've seen. The LMX2595 has similar specs but the LMX2820 has some nice advantages, such as lower flicker noise and the ability to drive both phase detector inputs externally.

Look them up on octopart.com and you'll see that they are all sitting in Chinese warehouses by the tens of thousands, waiting for buyers who don't mind paying 4x-5x MSRP.

ADF4371 (62.5 MHz - 32 GHz) also looks good. Some stock left at Mouser.

Of all these parts, I've only messed with the LMX2820 in person. I have a demo board for the Renesas part but haven't gotten around to powering it up and trying it out yet.

-- john, KE5FX

I have published a synthesizer based on LMX2594 (15 GHz) in Dubus 1/22. I will put it on my web site sooner or later, but the chip is currently vapourware. <

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There is 1 hittite HMC-451 output amplifier populated to drive a HMC-220 ring mixer. The TI dongle & software cannot tell it from an eval board.

There will be a companion clock generator with either a

100 MHz crystal oven or a CVHD-950. The oven/VCXO can be locked to an external 10 MHz reference. It delivers 300 MHz for LMX2594 in fractional mode or 400 MHz for LMX2594 in integer mode. 400 MHz uses 2 SAW filters after the multiplier, 300 MHz uses 2*3pole LC, top coupled. I could not find a nice 300 MHz SAW filter that is not EOL or has less than 10 dB loss.

A previous version had some 10 MHz spurious from the 1/10 prescaler. It also had only 300 MHz.

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It could be used for a DDS also, but currently there is no need to rush it because of the 2594.

At least it has some filtering after the output doubler. The ADF5356 had a subharmonic that was horrible.

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If someone wants to play with these things, there are enough boards. Hot air soldering is required, minimum.

cheers, Gerhard DK4XP

Very good info. Thanks

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Very interesting. Thanks

Mike VE3BTI

We use the LMX2571 as the internal trigger generator in one product. Jitter is great. It was a huge pain to program, as TI doesn't reveal the code that they use in the demo kit. Everybody has to figure it out for themselves. The data sheet is 62 pages long and the app note is another 31.

We have to suspend triggers while reprogramming the synth, which some users don't like.