Most of the millimeter wave mixers used in the amateur radio sector are subharmonic mixers that
are also used for transmission. The transmission power generated in this way is usually around 0.2
mW SSB or even less. Power amplifier chips for these frequencies are offered by Teledyne. These
chips achieve a power of over 200 mW at 23 dB gain (TSC 115-145G-5S4C). However, these parts are
very difficult to get and even more difficult to work with. Standard bond devices are no longer
sufficient here.
Another possibility to generate a strong CW transmission signal is the frequency multiplication
method. I have already described some possibilities in previous publications. A frequency doubler
from VDI was available to me, which promises an output power of approx. 200 mW at 122-134 GHz.
For this, however, a control power of 0.5-0.6 watts must be generated at 61-67 GHz. The efficiency of
this doubler is given as approx. 30%.
The search for a suitable amplifier that would generate this power was very time-consuming. Finally,
I found what I was looking for at gotMIC. This company produces a wide range of chips for the 60
GHz band. I have already used two of them as multipliers in my previous CW transmitters. When I
asked about this chip gAPZ0079, I got the information that there is a similar amplifier also available
as an SMD version in a soldering case, type: gMPA0038A. This version is much more expensive, but
of course much easier to work with. I decided in favor of this SMD version.
It should be mentioned here that the procurement of the information required for developing the
amplifier, receiving an offer and the parts was very difficult and time-consuming …!
Then again the shortened description of the already existing multiplier that is to be used to control
the 60 GHz power amplifier.*
Here you can find a original article in pdf CW Power TX for 122 and 134 GHz
Enjoy reading!
*Text from Michael Kuhne DB6NT article
Picture: from the original article
