StereoStim DIY Guide

[mantrid]

No, I do not. AC. Period. Nothing to do with modulation or carriers.

Yes, you do.

These medical device usually deliver pulses at a certain frequency. The spectrum is mainly defined by the shape of the pulses, not the pulse frequency. That's a form of modulation.

These low frequency sequences of pulses are passed by a a high-pass filter with a cutoff frequency of a few hundred Hz.

The same happens with Estim signals.

[tudeloo]

No, I still am not. You do not need pulse modulation for an estim device to work and deliver pleasure. I think this is the worst way to build a stim device using a digital modulation!
And still, even with any modulation if your carrier has a DC offset you still have the same problem.

These low frequency sequences of pulses are passed by a a high-pass filter with a cutoff frequency of a few hundred Hz.

Unlikely, that this is the case if the device is used at 2Hz. It would be very inefficient, because of the damping of an hp filter - no power output that you could feel - not to mention the higher degree of filtering you would need, but the passband is way to close to the used frequencies This does not make sense! Lowpass filtering does however make sense with 2-160Hz as it would remove any hf ripple coming in from EMI, but I doubt that it would actually matter, not for stimulus, but for information yes.

Yes, the power spectrum is mainly defined by the pulse shape and peaks at the pulse frequency. That is how we detect signals and decide what message is coming in, good job. It is interesting to know peak power of signals, but other than Stimulus is different from sending and receiving information as we dont need to demodulate it later

Do you even have a degree in EE? Because you are throwing stuff around.

[mantrid]

No, I still am not. You do not need pulse modulation for an estim device to work and deliver pleasure. I think this is the worst way to build a stim device using a digital modulation!
And still, even with any modulation if your carrier has a DC offset you still have the same problem.

Just this -- I wont try to explain it again: A modultated signal will never have DC offset because you cannot modulate with a 0 Hz carrier signal.

Do you even have a degree in EE? Because you are throwing stuff around.

If you are right everything in my software (see signature) is wrong. It should be easy for you to make it better.

When can we expect results?

[tudeloo]

You have no clue what you are talking about.
To everyone else with a functioning brain: a dc offset (also bias) is usually present in circuits if you dont take care of them! This wont be a problem if you send your signal thru the air, you are just lowering your efficiency and signal integrity.
However, in circuits that are always connected (no antenna) this can be a problem: during operation of a device the parts will heat up, one that usually does is the driver stage (mosfets, in general: transitors) and since transistors are dependend on their temperature it can shift their operation point forcing them into saturation etc. If you dont know how to design a solid circuit by biasing you can end up with modulated signals that will have a dc offset (bias)! Offsetting can also be done to ensure op amps opertation point stability... Offsets are always present after op amps if you dont use the right coupling capacitors!

Im1: no modulation, just AC with dc offset

Im2: modulation with dc offset

[hosenguy]

This conversation reminds me of working as a tech on high end Sansuii audio amplifiers back in the 70's. The entire output section was direct (DC) coupled. If even one transistor had gain different than its mate the whole output channel would go up in smoke. I often went through 20 or 30 drivers until I found 2 that were a dead-on match. All due to offset.

[mantrid]

You have no clue what you are talking about.
To everyone else with a functioning brain: a dc offset (also bias) is usually present in circuits if you dont take care of them!

That becomes totally off-topic. You are mixing up terms: Now you are describing data transfer standards that have nothing to do with modulation or estim. DC shifting is no modulation technique. See https://en.wikipedia.org/wiki/Modulation, DC shifting is not mentioned there. But maybe the authors have no brain too ...

The "direct data modulation" in your picture seems to be direct data -- without modulation. IO standards SSTL and HSTL look like this. Digital 2 pin sensors (like LMT01) often output signals like this. But neither data sheets nor specs call this technique "modulation". The term "modulation" is wrong for this kind of data transfer.

The other picture shows two sinusoidal signal signals. I see no relation to modulation.

[tudeloo]

The data modulation is just an example because it looks like you are not capable of imagining that a modulated wave can be offset unless the design engineer doesnt want it to happen and fixes it. I stated where and when it always happens with simple examples and why coupling capacitors are used.

Wikipedia is not a reliable source. Try: microelectronic circuits by sedra and smith or to quote from Digital Communications by Sklar on page 6 : "Modulation is the process by which message symbols
or channel symbols (when channel coding is used) are converted to waveforms that
are compatible with the requirements imposed by the transmission channel."
These are good sources.

And since you do not have any knowledge in analog or embedded design I will stop this discussion right now. You are wrong. Period.