K-Band Focal Plane Array: Integrated Downconverter Module #1 Matt Morgan and Tod Boyd National Radio Astronomy Observatory 8/7/2008
Jan 17, 2016
K-Band Focal Plane Array:Integrated Downconverter Module #1
Matt Morgan and Tod Boyd
National Radio Astronomy Observatory
8/7/2008
IDM1 is Complete
IDM2 is Not Complete – One Key Part Missing
I mistakenly ordered the wrong size feedthru header for this module. They havebeen re-ordered, and are expected to arrive in mid-September.
IDM1: Measured Gain
The bandpass is a little narrow. I will show later that it is not the filter.I probably just need to raise the lid slightly.
IDM1: Measured Gain
IF Response shows a lot of ripple. I believe this is related to cavity effects onthe PCB-side – which will not be present on IDM2.
IDM1: Measured Image Rejection
Image rejection at ±1.2-3 GHz offsets is better than 35 dB.
IDM1: Measured Image Rejection
Image rejection at ±5.9-7.7 GHz offsets is better than 32 dB.
IDM1: Measured Gain Compression
Output 1 dB compression point is about +7 dBm.
IDM1: Measured LO Power Requirements
IDM1: Measured Channel Isolation
There seems to be excessive crosstalk between channels (-20 dB), havinga strong IF dependance, but virtually no RF/LO dependance – this stronglysuggests that the crossover is occuring in the IF circuit inside the PCB cavity.
IDM1: Measured Return Loss
Poor return loss needs investigation.
IDM1: Measured Return Loss
Poor return loss needs investigation.
IDM1: Measured Return Loss
Poor return loss needs investigation.
Probe Measurements on Filters
Dynamic range of the measurement was limited at the high frequency end,but the passband looks perfect.
Probe Measurements on Filters
Perfect.
Compliance Matrix for Single Pixel Prototype
parameter symbol spec/predicted measurement comments
noise temperature Te 600 – 800 K not measured
gain G 30 dB 30 dB
gain ripple Gmax – Gmin 3 dB 8 dB presumed PCB cavity effect
output power Pout -25.5 0.5 dBm
-25.5 0.5 dBm
assuming predicted front-end gain
headroom HR +40 dB +33 dB probably ok
LO1 power required
PLO1 -3 5 dBm +1 8 dBm
LO2 power required
PLO2 +3 5 dBm +3 5 dBm
image rejection IR 25 dB 32 dB
channel isolation Iso 30 dB 20 dB presumed PCB cavity effect
return loss RF input
IF output
LO1 input
LO2 input
-17 dB
-19 dB
-12 dB
-10 dB
-11 dB
-11 dB
-6 dB
-12 dB
need to verify transition designs
mass M 250 g 316 g IDM2 will be much less, average should still meet spec
Future IDM1 Revisions
1. Modify ALH444 bias circuit for better gain repeatability.
2. Modify PCB cavity to include a metal barrier between IF circuits in bothchannels – this should improve channel isolation and IF gain flatness
3. Investigate cause of return loss problems – may require re-design ofthe transitions
4. Raise the lid above the filters to prevent de-tuning.
5. Clean up other minor PCB issues