Wednesday, 5 July 2017

9 GHz local oscillator source and new test gear

I recently acquired an Analog Devices ADF41020 18 GHz PLL evaluation board.
It comes fitted with a Hittite HMC515 11.5 - 12.5 GHz VCO which after quite
some effort I replaced with a Hittite HMC510 8.45 - 9.55 GHz VCO. The new VCO
will in fact lock from 7.6 Ghz to 10 GHz. I am getting about 3.5 dBm out of the board.
The output is a lot cleaner than the cheap YIG based oscillator I was using for a 9 GHz
LO.  The board itself cost $150 and the replacement VCO $35. I had considerable
difficulty in soldering the part in place. I watched all the YouTube videos on how
to do this sort of thing but it didn't work out as easy as they said it would. The biggest
issue was the ground plane sucking away all the heat and making it almost impossible
to get the solder to flow with the hot air tool, also the no clean flux would boil
away with the slightest amount of heat and lift the chip off the board.
Next time I will practice on some trashed boards but I am too impatient.
The Hittite VCO is the chip in the bottom right corner.
While the Hittite VCO is an expensive part it does also have a divide by 2 and
a divide by 4 output which could make it useful for a multi-band converter.
Still it makes a change doing hardware for once rather than software.

DVB-S2 displayed on an E4405B

I also recently bought yet another spectrum analyser for my lab. I felt I got it at
a really good price and it is a very clean example. It is only rated to 13.2 GHz.
I do have a much older HP 8952L that can be tricked to cover 24 Ghz but
I have never needed to use the upper range.

Spike QPSK Analysis
Spike Real time OFDM analysis of a 2 MHz DVB-T signal

Finally I have had the opportunity to experiment with the Spike software
package that comes with the Signal Hound BB60C for carrying out modulation
analysis. The software is constantly evolving and upgrades are free. So hopefully
in time many more modulation analysis features will be added. I would like to see
COFDM added, it is on their roadmap but not in the near future.

I have a couple of other projects in progress at the moment but they will be
the subject of another blog .

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