need a 10x10 crossing switch, with 100Hz to 6KHz BP and low RF suceptibility
Between integrate circuits and discrete transistors, wich design would you choose ?
Between integrate circuits and discrete transistors, wich design would you choose ?
It has far more to do with layout than technology.
What is the RF band that you are vulnerable to?
What is the RF band that you are vulnerable to?
I agree with the previous post that the frequencies that you want
to exclude from any type of design are important. The distance to
the source is just as important. Close to a source E or H fields
needs different shielding solutions (this is called nearfield). The
opposite is farfield when the source is several wavelengths away.
Lots of materials used for fixing EMC/EMI problems are available
but you have to do the selection based on an accurate description
of what the problem is. The modulation type of the RF (if known)
is also useful in the selection of "fixes".
Often it is the intrinsic diodes in solid state devices that rectify
RF and to me the choise between IC´s or transistors is not a clear one
(without testing). Multiplexer IC's (FET or MOS) are used for switching
audio but still have protection diodes. A signal generator and small
nearfield sniffer antennas (for H or E field) to inject RF into different
circuit solutions would be my own way. (sniffer antennas also work
the other way around)
to exclude from any type of design are important. The distance to
the source is just as important. Close to a source E or H fields
needs different shielding solutions (this is called nearfield). The
opposite is farfield when the source is several wavelengths away.
Lots of materials used for fixing EMC/EMI problems are available
but you have to do the selection based on an accurate description
of what the problem is. The modulation type of the RF (if known)
is also useful in the selection of "fixes".
Often it is the intrinsic diodes in solid state devices that rectify
RF and to me the choise between IC´s or transistors is not a clear one
(without testing). Multiplexer IC's (FET or MOS) are used for switching
audio but still have protection diodes. A signal generator and small
nearfield sniffer antennas (for H or E field) to inject RF into different
circuit solutions would be my own way. (sniffer antennas also work
the other way around)
Emitting Frequencies: 30MHz (100W), 490MHz (50W), phone bands, wifi.
@davidsrsb, @Instrumental, yours arguments are clever : a condensed PCB is a
of solution.
@Instrumental : "Often it is the intrinsic diodes in solid state devices that rectify
RF and to me the choise between IC´s or transistors is not a clear one
(without testing). Multiplexer IC's (FET or MOS) are used for switching
audio but still have protection diodes."
You point exactly to the question : is there a less sensible technology or better IC ?
@davidsrsb, @Instrumental, yours arguments are clever : a condensed PCB is a
of solution. @Instrumental : "Often it is the intrinsic diodes in solid state devices that rectify
RF and to me the choise between IC´s or transistors is not a clear one
(without testing). Multiplexer IC's (FET or MOS) are used for switching
audio but still have protection diodes."
You point exactly to the question : is there a less sensible technology or better IC ?
Surroundings seems a bit demanding but not horrible. I once did a
controller for a 2000W SW transmitter with the antenna feed
(open wire & balanced) a few meters away. Double die cast metal boxes
with feed-through filters inside a small box inside a bigger box with
processor and stuff. How many connectors, manual switches and control
lines there are influences what is easy to do. EMI gaskets around
all the lids. This way the inside can take whatever electronics is
best for the audio switching regardless of what happens outside the
boxes. My controller went to Sodankylä in northern Finland to be a
part of some ionospheric research experiment. Divide and conquer is
a useful strategy when it comes to shielding electronics. Individual
compartments for subcircuits is used a lot in microwave designs.
controller for a 2000W SW transmitter with the antenna feed
(open wire & balanced) a few meters away. Double die cast metal boxes
with feed-through filters inside a small box inside a bigger box with
processor and stuff. How many connectors, manual switches and control
lines there are influences what is easy to do. EMI gaskets around
all the lids. This way the inside can take whatever electronics is
best for the audio switching regardless of what happens outside the
boxes. My controller went to Sodankylä in northern Finland to be a
part of some ionospheric research experiment. Divide and conquer is
a useful strategy when it comes to shielding electronics. Individual
compartments for subcircuits is used a lot in microwave designs.
Emitting Frequencies: 30MHz (100W), 490MHz (50W), phone bands, wifi.
The first two require low pass filtering on all I/O
330R and 1nF is effective
I would use an IC crosspoint on a PCB with a full groundplane layer. Keeping all signal I/O and power on the same side of the case and PCB
Metal casing and you should be all right.
The first two require low pass filtering on all I/O
330R and 1nF is effective
I would use an IC crosspoint on a PCB with a full groundplane layer. Keeping all signal I/O and power on the same side of the case and PCB
Metal casing and you should be all right.
Feed-through capacitors are useful in a high RF environment. 1nF is again a good value. What connectors are you thinking of?
Any wires going to the box will carry RF current on the outside
of cable shields. These currents will also go across the surface
of the box so a metal box made of folded sheet metal is not enough.
Any gaps will transmit a part of the RF into the box. This is a
surprising phenomena that current across a gap is a good antenna
just as voltage on a metal rod is. Die-cast boxes and EMI gaskets
is a cheap solution. Without the gaskets a few contact points where
the screws hold the lid is not enough and corrosion can make it even
worse. Anodized aluminium is also a bad choise, no EMI gaskets will
work on an insulating surface.
of cable shields. These currents will also go across the surface
of the box so a metal box made of folded sheet metal is not enough.
Any gaps will transmit a part of the RF into the box. This is a
surprising phenomena that current across a gap is a good antenna
just as voltage on a metal rod is. Die-cast boxes and EMI gaskets
is a cheap solution. Without the gaskets a few contact points where
the screws hold the lid is not enough and corrosion can make it even
worse. Anodized aluminium is also a bad choise, no EMI gaskets will
work on an insulating surface.
I would have expected more IC references but may be it's a specialized audio domain...
CD22M3494 seems to be interesting : I didn't found any application even in datasheet. Evaluation module are no longer avalaible.
CD22M3494 seems to be interesting : I didn't found any application even in datasheet. Evaluation module are no longer avalaible.
You have not mentioned how many simultaneous cross-points can/must be
ON at the same time. The choise of IC's will depend on this. Transistors
(of any suitable kind) at each cross-point can do all variants.
ON at the same time. The choise of IC's will depend on this. Transistors
(of any suitable kind) at each cross-point can do all variants.
Stopping RF penetrating on shields is why you should keep cables to one side only. Once you have wires to both sides of the box, stopping RF current flowing through it becomes hard
No, then you can get a voltage maximum instead. RF interference is energy taking whatever route
it fancies. Current on the outside of a well-shielded box does no harm at all like inside/outside
of a waveguide.
where else can I get sharp remarks 😛
Project is a monitoring system with up to six listeners hearing 1 or 2 sources among 8.