Another foray into Multi-loop Coil Antenna design
Another foray into Multi-loop Coil Antenna design
(OP)
I'm still working through some of the transmit refinement for our antenna design. I've had a chance to actually see what is being measured by using a Tektronix Spectrum Analyzer. Definitely an eye opener. Now comes another interesting question about our antenna system. If you check my original thread, http://www.eng-tips.com/viewthread.cfm?qid=231049 , I drew up a representation of the receive antenna(similar to a Magnetic Read Head) design. Currently we are using a static 5V DC derived from 24V and a voltage divider, to monitor a break in the wiring. We are blocking the DC from the rest of the receiver section with polarized tantalum caps to reduce issues with specific frequencies becomming unstable. What my question comes down to is this.
Does any one know, or had experience with, the affect of leaving a static DC potential on a large inductor and then bombarded it with a bipolar pulse from another antenna. I've noticed that with the antenna monitoring circuit enabled in the system, I can see a fairly vigorous transition on the supply system when our LCD backlight extinguishes, along with the output of the post processing stage amplifiers. When the monitoring is disabled, I no longer see any transitions in the power supplies, or the post processing during the backlight transitions. Because we work with such low frequencies, and the method to detect the metal is treated as a slower(5-12Hz) sine wave. I'm unsure of a viable way to shunt the current spikes to ground while still enabling the monitoring and detection signals to properly pass. Realistically I'd like some ideas as to what effect the power supplies can be seing from the static poential resting on the antenna when it's being bombarded with a frequency, and if it's possible to filter that response out.
Does any one know, or had experience with, the affect of leaving a static DC potential on a large inductor and then bombarded it with a bipolar pulse from another antenna. I've noticed that with the antenna monitoring circuit enabled in the system, I can see a fairly vigorous transition on the supply system when our LCD backlight extinguishes, along with the output of the post processing stage amplifiers. When the monitoring is disabled, I no longer see any transitions in the power supplies, or the post processing during the backlight transitions. Because we work with such low frequencies, and the method to detect the metal is treated as a slower(5-12Hz) sine wave. I'm unsure of a viable way to shunt the current spikes to ground while still enabling the monitoring and detection signals to properly pass. Realistically I'd like some ideas as to what effect the power supplies can be seing from the static poential resting on the antenna when it's being bombarded with a frequency, and if it's possible to filter that response out.





RE: Another foray into Multi-loop Coil Antenna design
For example, if you ran DC through a coil with a ferrite core, it might drive the core to a point where the signal of interest pushes the core into a non-linear region.
Based on the description of your system, it seems obvious that a modest DC current through the core is likely to have no impact.
RE: Another foray into Multi-loop Coil Antenna design
RE: Another foray into Multi-loop Coil Antenna design
RE: Another foray into Multi-loop Coil Antenna design
Usually when a system is spread out over a large area, from conveyor belt to user interface, the subsystems could be distributed in a manner such the the user interface (in the office?) would be very far away from the signal processing subsystem (adjacent to the coils). Inherently designed so that all the signal processing circuits have a nice quiet shielded chassis all to themselves. It seems like this system isn't designed in that manner.
RE: Another foray into Multi-loop Coil Antenna design
RE: Another foray into Multi-loop Coil Antenna design
The usual E3 problems are related to shielding, "grounding" (not necesarily involving the planet's dirt layer), signal return paths, loop area, unintended coupling, wiring practices, etc.
In the military avionics world we have E3 specialists that are involved from start to finish. They tell (or remind) the system and box designers what to do with respect to such details as (for example) proving 360° bulk shield termination around each mil spec connector (details!).
In your case, based on very limited information, in sounds like you have noise getting on the power supply.
The problem is, the coupling mechanism might be so obscure that you will never notice it - and therefore you will never 'in a million years' describe it in your posts. In other words, we can't see it from here. It's one if the inherent limitations of this medium (must keep it in mind).
Advice: start thinking in terms of weak signal communications systems. Such receivers typically have plenty of shielded modules to keep noise away from the low amplitude front end circuits. Try to isolate the noisy user interface from the signal processing circuits. Maybe use an isolated battery to power the signal side as a temporary test to confirm or exclude coupling paths.
Ultimately, you may have to read up about E3 design practices, or hire a subject matter expert. The short version of E3 is that the control methods are the exact opposite of what's done to intentionally radiate radio signals.
RE: Another foray into Multi-loop Coil Antenna design
RE: Another foray into Multi-loop Coil Antenna design