Bill Ress wrote:
Hi Tom,

Thanks for sharing your thoughts on the phased array approach.

I especially appreciated your block diagrams which really helped. I'm sorting through the approach and will likely have some questions.

Regarding amplifiers for 5.7 GHz, Sirenza has a 1/4 watt for $4.80. It draws 165mA @ 5V or 7 amps for 43 of them.

Now here's the real heartburn device. The Hittite HMC409LP4 (I think the one you referred to) provides just over 1 watt, costs $8.52 (not bad at all) but runs 615mA at 5V - or  26 Amps for 43 antennas. If that input power doesn't bother anyone - there's part of our design!

I've never heard any estimates of what DC power Eagle is planning to deliver. Is that figure available yet?

Thanks again Tom for your time and thoughts.

Regards...Bill - N6GHz
Bill -- it was the Hittite HMC408 that we looked at. We (N4HY, W3GPS & I) got one of the HMC408 eval boards and tested it in Sep.'05. I presented a quick summary of our tests at the Eagle working group meeting in Pittsburgh in Oct.'05. I looked around for my PowerPoint presentation and found it; it can be gleaned on my "freebie" website at http://mysite.verizon.net/w3iwi/HMC408.ppt. The presentation, as posted, has one glaring error: the Hittite brick is missing from Slide #7. It's pretty obvious, bur it is a block between the DB6NT  upconverter and the -16 dB directional coupler. I never had a reason to re-present the talk, so I never bothered to fix the drawing.

Anyway, the main conclusions from our "quickie" tests were
  1. It worked as advertised in the data sheet (within ~ 1 dB which was comparable to our measurement accuracy).
  2. We concluded that we could affect you could optimize efficiency at any given power output level by tweaking Vctl.
  3. The peak DC>RF efficiency we saw was ~ 22% for Vctl in the 3.5-4V range and Vcc1=Vcc2=5V.
  4. There is a possibility of doing even better by doing a more careful optimization of Vcc1 and Vctl. I suspect that Vcc2 needs to be the recommended 5V. This is especially true if we are going to be able to use constant envelope BPSK.  (i.e. something approaching Class-C).
  5. Any amplifier can be easily shut down by setting Vctl=0.
Let's hope we can find a more efficient amplifier chip!

73, Tom