KBand Focal Plane Array Integrated Downconverter Module 1
K-Band Focal Plane Array: Integrated Downconverter Module #1 8/7/2008 Matt Morgan and Tod Boyd National Radio Astronomy Observatory
IDM 1 is Complete
IDM 2 is Not Complete – One Key Part Missing I mistakenly ordered the wrong size feedthru header for this module. They have been re-ordered, and are expected to arrive in mid-September.
IDM 1: 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.
IDM 1: Measured Gain IF Response shows a lot of ripple. I believe this is related to cavity effects on the PCB-side – which will not be present on IDM 2.
IDM 1: Measured Image Rejection Image rejection at ± 1. 2 -3 GHz offsets is better than 35 d. B.
IDM 1: Measured Image Rejection Image rejection at ± 5. 9 -7. 7 GHz offsets is better than 32 d. B.
IDM 1: Measured Gain Compression Output 1 d. B compression point is about +7 d. Bm.
IDM 1: Measured LO Power Requirements
IDM 1: Measured Channel Isolation There seems to be excessive crosstalk between channels (-20 d. B), having a strong IF dependance, but virtually no RF/LO dependance – this strongly suggests that the crossover is occuring in the IF circuit inside the PCB cavity.
IDM 1: Measured Return Loss Poor return loss needs investigation.
IDM 1: Measured Return Loss Poor return loss needs investigation.
IDM 1: 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 d. B gain ripple Gmax – Gmin 3 d. B 8 d. B presumed PCB cavity effect output power Pout -25. 5 0. 5 d. Bm assuming predicted front-end gain headroom HR +40 d. B +33 d. B probably ok LO 1 power required PLO 1 -3 5 d. Bm +1 8 d. Bm LO 2 power required PLO 2 +3 5 d. Bm image rejection IR 25 d. B 32 d. B channel isolation Iso 30 d. B 20 d. B presumed PCB cavity effect return loss RF input IF output LO 1 input LO 2 input -17 d. B -19 d. B -12 d. B -10 d. B -11 d. B -6 d. B -12 d. B need to verify transition designs mass M 250 g 316 g IDM 2 will be much less, average should still meet spec
Future IDM 1 Revisions 1. Modify ALH 444 bias circuit for better gain repeatability. 2. Modify PCB cavity to include a metal barrier between IF circuits in both channels – this should improve channel isolation and IF gain flatness 3. Investigate cause of return loss problems – may require re-design of the transitions 4. Raise the lid above the filters to prevent de-tuning. 5. Clean up other minor PCB issues
- Slides: 17