122 GHz transverter


Let's try a harmonic mixer concept designed by Philipp DL2AM and Michael DB6NT.
It is based on article "122.250 GHz transverter technique" by Philipp DL2AM in Dubus 2/2018.
Tx output : 30 - 100 W (multiplier and IF mixer)
                    1 - 2 mW (only multiplier for beacon)
RX NF : > 20 dB

122 ghz transverter

122 ghz transverter


Click on image, download and extract my Excel sheet "Link budget v2.1" to calculate microwave links up to 1000 GHz. Calculation of atmospheric attenuation (ITU-R P.676-12) is included.

microwave link budget




1. Offset dish and tripod with pan/tilt mount


Same design as for my 76 GHz transverter and pan/tilt head.
A TVSat offset dish for 11 GHz is not the best solution for 122 GHz because of poor surface accuracy, additional loss is around 10 dB. But let's try, otherwiese I have to use a link station dish for 37 GHz.



2. W2IMU Dual mode feed horn


hdl_ant software by W1GHZ is a good choice to calculate a dual mode feed horn. It is a circular wave guide with a diameter of 1.8 mm and the aperture is 3.8 mm (depth of 6 mm).
Wave length = 2.45 mm
WR-8 : 2 x 1 mm

122 ghz dual mode horn



3. PLL with 13.5 GHz output


I use a modified NORT PLL to obtain 13567.3333 MHz for the transverter input. I removed the internal 20 MHz quartz and mounted a SMA connector which is an external reference input now.
See more under electronics.

13567.3333 * 3 * 3 + 144 IF = 122.250000 GHz

NORT

Another solution is a 13.4 GHz PDRO from CTI locked to 13.5673333 GHz, REF-In could be a 135.673333 MHz signal.
Current consumption @ 12 - 15V DC: 240 mA
Signal locked output : 4.6 V
RFout = 14.5 dBm

13 ghz PDRO PLL

13 ghz PDRO PLL



4. Triple multiplier module and power supply PCB


Multiplier CMA 382400
Input: 13.5673 GHz, 14.5 dBm
Ouput: 3 x 13.5673 = 40.702 GHz, max. 100 mW

38 ghz multiplier

Power supply for triple multiplier for TX and RX mode.

122 ghz power supply



5. Harmonic mixer


PCB no.47 made by Michael Kuhne DB6NT and a MA4E1310 single diode as subharmonic mixer.

122 ghz mixer board

Mixer housing

122 ghz mixer board

122 ghz mixer board

MA4E1310 single diode: Here you can see 5 diodes, each 0.6 x 0.3 mm

122 ghz mixer diode

At first I glued the mixer PCB with silver conductive adhesive solder (e.b. E-solder 3021A and 3021B) into the housing. Then I put the housing in an oven for 1-2 hours at 80-100C.
With the use of a stereo microscope I glued the diode on the mixer PCB. Use only a very very small drop of silver glue for both solder pins. Therefore I used a very thin needle. Again put the housing in an oven for 1-2 hours at 80-100C.



122 ghz mixer diode



6. IF module


PCB no.26 made by Michael Kuhne DB6NT.



IF module housing

122 ghz IF interface



7. GPS disciplined reference oscillator to drive NORT or PDRO module


Here I use a nice Mini-GPSDO by Leo Bodnar. It has 1 output (3.3V CMOS level) from 450 Hz to 800 MHz and it uses GPS receiver for very stable output frequency.
Output power up to 13.7 dBm
Current consumption @ 5V DC: 200 mA
Output frequency is 135.673333 MHz to drive PDRO from CTI

GPS reference



8. IF receiver/transmitter


Therefore I use the good, old FT-290R or my FT-817. I have upgraded my FT-817 with an additional IF output. In combination with e.g. SDR# and a Lenovo Convertible Miix 320 Tablet computer I can find small signals to adjust frequency and dish orientation.



9. Accu pack


I use a 12V LiFePO4 accu with 10Ah because of its light weight, only 1.4 kg.



10. Test results