Chris Bartram G4DGU
The problem trying to use a 144MHz IF at 10GHz is akin to trying
to use top band as an IF for 2m! It is very difficult indeed to
design a simple, low-cost filter to reject the image adequately.
That is particularly true if you wish to make it free from
adjustments. I have been there!
My solution, which was available off the shelf, was a simple
two-pole filter using orthogonally polarised circular WG
resonators sharing the same length of guide. The design produces
50dB+ rejection at 10008MHz with between 1 and 2dB loss at
10368MHz. I came up with that I when I designed my transverter.
The design did go through a number of iterations in which I tried
to eliminate adjustments. I almost got there, but the very
accurate machining which was required put the costs of manufacture
through the roof. The final version, while extremely reproducible,
did need to see my VNA for set-up.
I have looked at other solutions using eg. resonators realised in some forms of substrate integrated waveguide. Some look promising, but other activities have interfered, and I'd like to get back on the air before I decide to do any more work on the project!