Even with gapless capture, the task of resolving RF interference problems is challenging enough that it deserves to be guided by a systematic process. One such process includes:
. Step 1. Capture
In this step, data is acquired using long-duration recording to ensure the capture of the culprit event. Long duration is required because the signals in the RF environment are often long duration. Also, RF environments change over time and typically have crowded spectrums. Moreover, the increasing bandwidth of modern communication signals means the noise spectrum is wider and interactions are often intermittent, subtle or transient.
. Step 2. Search
Once acquired, a recording is played back and analyzed in the lab, as necessary, to extract information about the culprit interferer. Signal search tools, which can perform automatic searches based on many different criteria, are highly recommended for finding interferers in very large records. The search results in a list of signals from the data record that matches the criteria. Once found, these signals can be clipped out and played back using a signal analysis application.
. Step 3. Re-capture Data
Once the engineer has a better understanding of the problem scenario or what the potential culprit interferers are, it may be necessary to capture more specific recordings. In this optional step, the engineer uses that knowledge of the culprit to trigger additional recordings with better signal-to-noise ratio. These recordings can focus on a specific reaction of a victim receiver to a specific culprit interferer. Here, a dual-channel recording system may prove especially useful as it can be configured to use one of its channels to trigger the recording.
. Step 4. Analyze
Finally, the engineer can uncover the effect of the culprit interferer using analysis software.
Utilizing this process, engineers not only acquire knowledge of the RF environment, but are also able to record information in the frequency band over a long duration. As a result, they can efficiently use RF recording to record, search and analyze target signals in complex RF environments.
Not covered in this paper but also very useful is the fact that these recording systems have significant amounts of pre-trigger capability that allow us to record many seconds of data prior to the actual trigger event.
This opens up the possibilty of applying some signal processing to the data in the triggering channel to make a sophiticated criteria based trigger.
It doesn't matter that this processing could take seconds; the pre-trigger capability of the recording channel provides the time.
Thank you for your comment that it is actually the knowledgable Engineer that is critical to solving the interference problem and your keen observation [borne out of experience] that there is often a whole lot of detective work done before the measurement system even becomes necessary. I certainly agree with your assertion.
This was a short paper in which I attempted to show that a recording system can be very useful for helping to root-cause a specific interference problem caused by signals in the external environment that are both intermittent and probably non-compliant.
Having a permanent record of the signal environment, which is known to cause an interference problem with some RF system or device, affords us the luxury of processing this data "offline" back in the lab.
Even with a recording system, it can still be tricky to capture the actual culprit signal, as it occurs, because the analyzers triggering system may false trigger on other signals too.
Note that I'm suggesting it is generally not too efficient to record hours and hours of data.
Even a few seconds of recording at wide RF bandwidths can produce Giga Bytes of data.
After all, who has time to process that much data.
It is usually much better to selectively record.
In that case I posited that an additional independently tunable receiver could be tuned specifically to the frequency and bandwidth of the suspected intererence signal to provide more selective triggering capability, since the recording in the afflicted channel could be initiated by this trigger channel.
This is funcionally equivalent to a frequency selective trigger with the added benefit that we can trigger off of out-of-band signals.
in standing down, the users, will tell you the noise interference problems, and the locations, and when they have occurred , "you just have to ask" don't worry about ambiguity, and when you have solved, " good luck " ask again.
Dave, i so enjoy your company's expertise. i value the technical thought as first class. active voice and problem solvers, " i thank you "
from Ralph T. Gerwing yvr.ca Metro Vancouver Cheers.
pretty penny this analyzer your promoting, but, in real world problem solving " especially building new band services " it is very valuable indeed.
"" Tracking down interference in complex RF environments "" well yea, but:
Interference usually is in the receivers, hand-helds, base stations or auxiliary receivers.
If the hand-helds are moving about, then interference zones may be noticed by the users. , in a particular building, a geographic square block, or fraction of a larger area.
The engineer is in the know, who is a close frequency user. as adjacent channel user, or third intermodulation contributor. all of this comes into play "the math" and analysis before, the recording data comes into play.
The recorder itself, just shows, the place and time values. ' it is not really the solver of the fact " however an item of merit you may of wanted to touch on was.
Propagation measurements, of band by band comparison, to fulfill an existing radio footprint plan system. that is of merit, similar or better.
In my studies of this, equal merit or better, the recording data is "Missing" or has not been done at all.
A lot of new systems are poorly designed in coverage. getting in building coverage has been a failure, the recording analyzer will tell you what you have now, and when the new system goes in, what you have got to replace it with .
Now i am simplifying my thought here, as this is a very important topic. \
i will say, in my work experience as a principal, i ordered ten percent of project value to be in Test equipment, and bought many pieces of gear, by your wonderful company ""AGILENT""
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