Using JDSU Equipment to Test and Troubleshoot CPD, Impulse Noise, and Ingress in the Return Path
● Common Path Distortion (CPD) is created by non-linear mixing from a diode junction created by corrosion and dissimilar metal contacts. It’s not just dissimilar metals, but dissimilar metal groups. There are 4 main groups of metals:
1. Magnesium and its alloys
2. Cadmium, Zinc, Aluminum and its alloys
3. Iron, Lead, Tin, & alloys (except stainless steel), and
4. Copper, Chromium, Nickel, Silver, Gold, Platinum, Titanium, Cobalt, Stainless Steel, and Graphite.
●CPD is second and third order intermods from the forward channels intermixing and creating distortions, which fall everywhere. CPD will make CSO/CTB worse for forward performance.
● Separation depends on forward channel plan. NCTA, HRC, and IRC plans that use NTSC, 6 MHz spacing will have beats every 6 MHz. PAL could be every 7 or 8 MHz.
●The original culprit was the old feed-through connectors. Dissimilar metals from the copper clad, aluminum center conductor and the stainless steel seizure screw.
■Noise Readings
●Be careful with spectrum analyzer, noise level readings. 2 dB/div is a good scale for sweeping and 5 or 10 dB/div is best for the spectrum mode.
●The level displayed is based on the RBW setting and will be very different from one setting to another. A -20 dBmV noise floor with 30 kHz RBW is really 1.2 dBmV in a 4 MHz bandwidth and there’s usually a correction factor associated with
|
|
|
|
|
|
|
Application note & Design Guide |
|
|
|
|
Please see the document for details |
|
|
|
|
|
|
|
|
|
|
|
English Chinese Chinese and English Japanese |
|
|
2006/9/6 |
|
|
|
|
|
|
|
|
236 KB |
- +1 Like
- Add to Favorites
Recommend
All reproduced articles on this site are for the purpose of conveying more information and clearly indicate the source. If media or individuals who do not want to be reproduced can contact us, which will be deleted.
Integrated Circuits
Discrete Components
Connectors & Structural Components
Assembly UnitModules & Accessories
Power Supplies & Power Modules
Electronic Materials
Instrumentation & Test Kit
Electrical Tools & Materials
Mechatronics
Processing & Customization
