QRP PA devices for 10 GHz


Greg - ZL3IX
 

We've recently seen a couple of posts on this group about higher power (and expensive) PA devices, but what are guys using for the lower powers, maybe 0.5 - 2W? Are there devices around for a more reasonable price? I'm making fair progress with my home brew transverter for 10 GHz, and the next stage will be to produce a little power on the band. ideas?


Neil Smith G4DBN
 

HMC952A looks reasonable at around £37 plus tax at Mouser and £34 at Digikey in 10-off Cheaper from Arrow/Richardson RFPD, but DK/Mouser deal with UK import VAT, saving customs fees. I just bought ten in case they decide to go on back order adn 52 week delivery, like some parts.

https://www.digikey.co.uk/product-detail/en/analog-devices-inc/HMC952ALP5GE/1127-3364-ND/5813138

https://www.mouser.co.uk/datasheet/2/609/HMC952A-972562.pdf

35 dBm saturated , P1dB 32 dBm, and over 30dB gain at 10368 MHz internally matched and with a power detector. Needs negative bias and interlocks for bias loss, overcurrent, and needs a temperature monitor. Power is +6V at 1400 mA quiescent and 2 A flat out.  The PCB needs to shift heat well, the pad is 3 x 3 mm and needs to lose 10 watts,  Thermal resistance is already pretty high, so cooling is a serious challenge, even if the PCB has lots of vias under that pad and it is soldered to a copper case or spreader.

There are still some gasfet devices around, but of the current crop of non-obsolete parts, this one looks to be best value. HMC487 is lower power, lower gain and double the price for no obvious benefit.

Neil G4DBN

On 07/05/2021 21:36, Greg - ZL3IX wrote:
We've recently seen a couple of posts on this group about higher power (and expensive) PA devices, but what are guys using for the lower powers, maybe 0.5 - 2W? Are there devices around for a more reasonable price? I'm making fair progress with my home brew transverter for 10 GHz, and the next stage will be to produce a little power on the band. ideas?
_._,_._,_



Neil Smith G4DBN
 

Price with tax, delivery duty paid was £40.60 each for ten-off from Digikey.  No need for an EAR declaration.

Neil G4DBN

On 07/05/2021 22:10, Neil Smith G4DBN wrote:

HMC952A looks reasonable at around £37 plus tax at Mouser and £34 at Digikey in 10-off Cheaper from Arrow/Richardson RFPD, but DK/Mouser deal with UK import VAT, saving customs fees. I just bought ten in case they decide to go on back order adn 52 week delivery, like some parts.

https://www.digikey.co.uk/product-detail/en/analog-devices-inc/HMC952ALP5GE/1127-3364-ND/5813138

https://www.mouser.co.uk/datasheet/2/609/HMC952A-972562.pdf

35 dBm saturated , P1dB 32 dBm, and over 30dB gain at 10368 MHz internally matched and with a power detector. Needs negative bias and interlocks for bias loss, overcurrent, and needs a temperature monitor. Power is +6V at 1400 mA quiescent and 2 A flat out.  The PCB needs to shift heat well, the pad is 3 x 3 mm and needs to lose 10 watts,  Thermal resistance is already pretty high, so cooling is a serious challenge, even if the PCB has lots of vias under that pad and it is soldered to a copper case or spreader.

There are still some gasfet devices around, but of the current crop of non-obsolete parts, this one looks to be best value. HMC487 is lower power, lower gain and double the price for no obvious benefit.

Neil G4DBN

On 07/05/2021 21:36, Greg - ZL3IX wrote:
We've recently seen a couple of posts on this group about higher power (and expensive) PA devices, but what are guys using for the lower powers, maybe 0.5 - 2W? Are there devices around for a more reasonable price? I'm making fair progress with my home brew transverter for 10 GHz, and the next stage will be to produce a little power on the band. ideas?
-- 
Neil
http://g4dbn.uk


Greg - ZL3IX
 

Looks like just the sort of thing I'm looking for, Neil, although, as you say, dissipating the heat will be a serious challenge. I'm not sure how to go about that, and will have to do some research on the thermal resistance of vias. I guess it would need a copper heat spreader, which would need to be pre-heated before attempting to solder the device. That's all new territory for me! Luckily one appears to be able to use the internal reference diode as a temp sensor, so at least the device can be shut down when too hot.


Neil Smith G4DBN
 

I'm going to try a PCB with 0.3 mm PTH in a tight pattern, solder it to the spreader first, let it cool, then use a stencil to fill the holes with paste and put the whole assembly in my oven for reflow. Another approach is to get the PCB fab to fit the devices, then  use low temp solder to fix the PCB to the spreader. If the two-step process isn't successful, I'll go one-step for the while thing.  When that fails, I'll go back to silver epoxy.

I haven't decided what connectors to use yet.  I have some tab-launch SMAs rated to 27 GHz, but I think I prefer the idea of these: https://www.digikey.co.uk/product-detail/en/cinch-connectivity-solutions-johnson/142-0761-811/J798-ND/673171 which are cheaper than the Amphenol SV Microwave versions.

I wonder if using GCPW lines for the RF connections might mean I can use solder resist over the lines so I can solder the connectors at the same time as the components. I'll have a chat to my friendly neighbourhood CPWG expert. Doubtless everyone will say I will get away with ENIG or HASL on FR4, but where's the fun in that?  I know there are others working on designs using the same little chip and they are certain to be better than my feeble attempts.

I have other stuff to get finished first though. LOTS of other stuff.

Neil G4DBN

On 09/05/2021 01:13, Greg - ZL3IX wrote:
Looks like just the sort of thing I'm looking for, Neil, although, as you say, dissipating the heat will be a serious challenge. I'm not sure how to go about that, and will have to do some research on the thermal resistance of vias. I guess it would need a copper heat spreader, which would need to be pre-heated before attempting to solder the device. That's all new territory for me! Luckily one appears to be able to use the internal reference diode as a temp sensor, so at least the device can be shut down when too hot.


Oguzhan Kayhan
 

Hello
It would be nice to have any pcb designs to be able to use it specially with the transverters that Neil is preparing
I would definitely love to get one


On Sun, May 9, 2021 at 1:24 PM Neil Smith G4DBN <neil@...> wrote:
I'm going to try a PCB with 0.3 mm PTH in a tight pattern, solder it to
the spreader first, let it cool, then use a stencil to fill the holes
with paste and put the whole assembly in my oven for reflow. Another
approach is to get the PCB fab to fit the devices, then  use low temp
solder to fix the PCB to the spreader. If the two-step process isn't
successful, I'll go one-step for the while thing.  When that fails, I'll
go back to silver epoxy.

I haven't decided what connectors to use yet.  I have some tab-launch
SMAs rated to 27 GHz, but I think I prefer the idea of these:
https://www.digikey.co.uk/product-detail/en/cinch-connectivity-solutions-johnson/142-0761-811/J798-ND/673171
which are cheaper than the Amphenol SV Microwave versions.

I wonder if using GCPW lines for the RF connections might mean I can use
solder resist over the lines so I can solder the connectors at the same
time as the components. I'll have a chat to my friendly neighbourhood
CPWG expert. Doubtless everyone will say I will get away with ENIG or
HASL on FR4, but where's the fun in that?  I know there are others
working on designs using the same little chip and they are certain to be
better than my feeble attempts.

I have other stuff to get finished first though. LOTS of other stuff.

Neil G4DBN

On 09/05/2021 01:13, Greg - ZL3IX wrote:
> Looks like just the sort of thing I'm looking for, Neil, although, as
> you say, dissipating the heat will be a serious challenge. I'm not
> sure how to go about that, and will have to do some research on the
> thermal resistance of vias. I guess it would need a copper heat
> spreader, which would need to be pre-heated before attempting to
> solder the device. That's all new territory for me! Luckily one
> appears to be able to use the internal reference diode as a temp
> sensor, so at least the device can be shut down when too hot.







--
73
de TA2NC