Monday, 11 June 2012

2G Band pass

This filter was a real pain to get hold of. Since the 2G path is only single-conversion for now (I'm actually working on a front-end improvement with a 2 GHz...10 GHz YIG oscillator), the requirements were pretty demanding. The 1G path actually tunes up to 1200 MHz, so that I was looking for a band pass filter with a pass band in the region from 1.2 GHz to a little over 2 GHz.

I still need to take a picture of the amplitude response but the pass band is from 1200 MHz to just above 2000 MHz with pretty steep skirts. It apparently originates from an old Hewlett Packard spectrum analyser and I got it reasonably cheap off an US-based surplus seller.

Band pass filter for the 2G path.

Update, got screen shots of  the filter response and return loss (looks like I forgot to calibrate, ah well...):

The 3db-bandwidth is about 980 MHz from 1074...2053 MHz.
Not sure if this measurement is meaningful, I forgot to calibrate when I changed the frequency span.  The return loss is about 15 dB or better over the pass band.

Front panel connectors and cable

Inside view of the front panel. I would love to use 0.141" hard line coax to connect the front panel connectors to the slim modules but I'm breaking my fingers trying to bend the coax. I wonder if I could use the semi-rigid 0.141" coax instead, I think to remember that Sam recommended using the hard line coax for high power connections (which the input connectors kind of are). Alternatively, I also have 0.086" aluminium hard line coax.

Wednesday, 6 June 2012