3 phase from single phase AC

[rave154]

Thanks gyula,

a beehive indeed

looking at the pdf and Figure 1-2. Relationship between time and frequency domain... the left hand half of it shows the imposition of 2 sine waves on a single screen and behind that the two sine waves themselves....ignore the right hand half for now.

whats shown on the screen is that when the two waves upward peaks coincide...then the resultant waveforms peak is bigger than either of the two..and of course..when one peak is going up and the other down then the resultant peak is now as far down ( you know what i mean )

now, in my DC i cant see how this varying voltage will occur if both my DC signals are 12V, ie..in my schematic..if both mosfets are ON....then the coil will still have 12V across it.and if only 1 mosfet is ON..it will still have 12V across it.

hmm.....do i need to go to AC to do what i want?

[gyula]

Hi,

Yes I think you go in the right direction with your last question.

Years ago I built mixers both with FETs and bipolars but always used a tuned LC circuit for selecting a third frequency from the inputted other two and they were linear and not switching mixers. Without a tuned LC circuit I found low output voltages at any mixed frequency component. of course it always depends on the actual value of the working loading of the following stage after the mixer or the actual load at the mixer output.
With a wideband (i.e. frequency independent for a wide range) load all the mixed outputs are present with an amplitude the nonlinearities of the device or devices constitutes and how their phase shifts with the rest of the components in the circuit let them develop.

The kind of mixer you try is a switching type mixer and indeed one of the AC input signals should be connected to either the same input the other AC input is connected or to another electrode, for instance to its drain and no supply voltage is used... See Figure 28, page 16 for such a mixer in this link:
http://www.plextek.com/papers/mixers2.pdf but there are such elsewhere in the web too. Chapter on FET mixers start at page 14, first they show active mixers that need supply voltage (not shown) but in Fig. 28 one of input AC comes to the drain electrodes via a wideband transformer, no supply voltage.
A balanced mixer is shown which cancel at the output the AC input to the gate electrodes, if this is not ok for your application then use only one FET in your shown schematic, one AC input could go the gate and source as usual and the second AC input could go to the upper end of the coil with also respect to the source, no need for the DC supply. The output could be from a coupling coil coupled to the other coil, i.e. use a 1:1 transformer like a bifilar coil when used normally, not in bucking mode. Sorry but I did not build such switching mixers, I give my best "shots" but still I am not sure if such switching mixer is the best for your task which is: i want, two pulsed DC signals of different frequencies down the same wire This even sounds like a TPU task?

rgds, Gyula

[rave154]

Gyulasun,

thanks for that information, i will read through it tomorrow ( late here now )

the past few days, ive been looking at and collectiong various pieces of soundcard software that allow amplitude modulation of up to 3 signals .... i seem to have found what im looking for.

3 different freq's modulated onto a base wave going into the left channel./....and another different set of 3 freq's going into the right channel

so now i can take the output from my sound card now, either left channel or right channel as i wish, into my audio amplifier...and then onto the coil, left channel to winding-A of the Rodin coil, right channel to winding-B of the Rodin coil.....

getting a bit........TPU'ish i know.....but....oh well...might as well follow the trail..after all, whats the alternative....turn on the TV and watch american gladiators?

we shall see if anything happens......if it does youll be the first to know