Sine wave multi frequency

[EL NINO]

So far, in my opinion, the only detector with 2 sine frequencies is the Aka Intronik.

[Altra]

I doubt there is any one ideal way to do this. For example, if you want a 1x and 3x frequencies you could do it this way:



The top waveform is coil current. You can adjust the short ramplet duty cycle to change the amount of TX energy between the 1x & 3x frequencies. This is probably best done by watching an FFT.
Here's another way of producing 1x and 3x frequencies:



It's not necessary that the ramplets be symmetrical. Here's the DFX TX waveforms:

This is very interesting. A while back we were discussing the same thing. I was working a CZ like circuit. My tx was a 5khz square wave, band passed at 5 and 15khz. My complaint was low sensitivity for low conductors. The cause was a weak 3rd harmonic. You suggested using a signal like the DFX Tx. So I programmed the Tx just like your illustration. To my suprise when I looked at the spectrum, the 15khz had a higher magnitude than the fundamental 5khz. In turn it threw all the ratios off like salt balance and GB, so I shelved the project. But from what you are saying here, I can tweek the 3rd by adjusting the short periods. When I get some time I'll give it a try..

Thanks

[Carl-NC]

Yes, adjust the timing to adjust energy ratio. This will also mess up the salt ratio and probably GB, depending on how you do GB.

[PolarisBlitzX]

Could you provide more details on what you're referring to? Are you discussing generating a sine wave with multiple frequencies, signal processing, or something else? Happy to help if you're looking for insights on waveform generation, modulation, or practical applications!

[boilcoil]

Another option to build a sinusoidal signals is to use the microcontroller's DAC. This even not need to be a highresolution - 5 bits are enough.

[pito]

for two square wave use cd4060, if you need sine add filters.

[moodz]

...generating high power sine waves is fairly easy using additive half sines and an allpass filter because it will allow passage of odd harmonics ...
For instance I use the waveform below generated from a square wave source simple biresonance and consumes only 75 ma from a 12 volt source to generate practically equipower sine waves at 20 and 60 Khz with clean spectrum and no wasted energy. Those "ramplet" waves are simply weird.

[mateatek]

Could you provide more details on what you're referring to? Are you discussing generating a sine wave with multiple frequencies, signal processing, or something else? Happy to help if you're looking for insights on waveform generation, modulation, or practical applications!

It is not difficult to generate a sine wave of multiple frequencies. The difficult thing is to be able to fit this to the transmitter coil. You could give me an idea of how to vibrate a coil at multiple frequencies.

I just noticed that I was answering someone who shouldn't have. It only advertises.

[Olly]

I'm using a fairly large FPGA to do some exprimenting with so I'm inclined to sticking with sine waves for now as they are easy to generate and combine. I guess I'll take the hit in current consumption and force drive the coil using a power amplifier.

Choosing the set of frequencies to use also needs careful attention as I plan on direct sampling with a 768kHz ADC and then doing synchronous demodulation. The trick is to get an integer number of waves for each of my frequencies to fit exactly into my overall sampling window.

I'm attempting to generate up to 4 frequencies within my complex waveform and have the facility to individually adjust the relative amplitude of each.

[moodz]

I already published the circuits how to make sine and half sine ...even quarter sine TX. High power and minimal current draw. An FPGA makes things a lot easier to do things synchronously but oversampling means you won't need a preamplifier since with the right ADC you can't actually implement an amplifier with lower noise than the ADC sample step resolution ... I get approx 6 nanovolt resolution on my 24 bit oversampled implementation and I am only demodulating single frequency .... Not sure that multiple frequency is actually needed.

[Aziz]

...generating high power sine waves is fairly easy using additive half sines and an allpass filter because it will allow passage of odd harmonics ...
For instance I use the waveform below generated from a square wave source simple biresonance and consumes only 75 ma from a 12 volt source to generate practically equipower sine waves at 20 and 60 Khz with clean spectrum and no wasted energy. Those "ramplet" waves are simply weird.

This is a very nice wave form Moodz!
I would be interested on the TX circuit and spice simulation. I don't know where to search for.
Aziz

[pito]

TX circuit
Aziz

regular audio amplifier , the speaker coil is driven by multi frequencies.

[moodz]

Not a regular audio amp ... A "D" class amp like the TP32xx series from TI that have 100khz bandwidth and can achieve around 90% efficiency into a half ohm coil.

[moodz]

TPAxx ...typo

[pito]

to big