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EMDrive Cavity V3 test measurements

A project log for EMDrive/satellite

Developing a small fuelless microwave thruster

paul-kocylaPaul Kocyla 02/01/2016 at 08:536 Comments

Test measurement with the new silver cavity V3.
First graph shows the response with no load,
second graph shows the response with cavity attached.
I marked two places where I assume an excitation, the left peak is close to the desired TE013 mode.
However, the graph is not so clean like in theory papers, so I´ll need some help regarding the interpretation of the graph.
(First scale tests don´t give results due to noise - i am working on that)

Graphs show reflected power (at least mostly, if the directional coupler is working as desired :)

Discussions

gstrazds wrote 02/05/2016 at 22:00 point

Personally I would like more description - what do the three variables mean. Phase = in optical circles is the rotation of the electric vector which means there is a linear polarization as opposed to elliptical or even circular polarization; and the ability to rotate the phase! Magnitude = Gain where over time the magnitude drops off as the frequency changes or as the frequency changes; less gain occurs... where a new node is engaged resulting in a new mode structure which appears - these are standing wave structures after all. Where do you get TEO13 mode from; looks like a cavity shape to me.. So what cavity shape is it ? your V3 ? I would like to see the illumination of your thought process.. The other days, I was looking at Magnatrons, Traveling wave tubes, Klystrons.. etc; pondering 60 kilowatts output from one family of device.. then went hmmm 60Kw is lots of juice - whats going to supply that juice. 

which is what I previous said.. 

So I wanted to draw out your thoughts as to the meaning of the graph Cavity V3.  The Blue line represents Magnitude - Do the peaks represent maximum resonance.. the minimums " an absence of resonance"  where is the frequency represented in the graph?  In your writings I read that your RF supply can scan a range of frequencies to find maximum resonance;  where other versions of the EM- Drive have an adjustable  screw to tune the cavity. I thought this is a clever way to set the resonance of the cavity.

If that graph is the output of your scanning feature then those sets of maxima  represent maximum  resonance for that frequency setting.

I still require clarification as to what phase means. So I want to ask a couple of questions. 

What is the output of your RF device. Is it Linearly polarized, elliptically polarized, or circularly polarized, could even be randomly polarized.. I talk about this as the polarization of the microwave signal interacts with the standing waves inside the cavity.  If the phase of two reflected wave forms are out of phase by 90 degrees, the the 3D location of that signal is canceled "actually negative" in that immediate region of the signal by the constructive and destructive interference of that frequency / wavelength. Should your signal be be circularly polarized; I my view it would most successfully interact inside the cavity environment because of the curved angular nature of the cavity itself.

By changing the frequency input the shape of the standing wave structure changes to accommodate itself inside the cavity. to the point where it cancels itself  at the minima resulting in the observed null(s) in the above graph.

There are 2 photos posted on the NASA em-drive web site; although this came through a Forbs article. http://blogs-images.forbes.com/startswithabang/files/2015/11/NASA-truncated-cone-Magnetic-Field-TM212--1200x733.jpg and another one when I find it I will add it here. ( it shows 6 areas of interaction within conical cavity along it's length; It is a 2D view however.)

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Paul Kocyla wrote 02/06/2016 at 17:08 point

I am measuring the wave which is reflected back from the cavity - if my directional coupler is working correctly.

This wave is mixed in a quadrature mixer with the transmitted wave.

As the waves have the same frequency, the mixer gives me two DC voltages which represent the I/Q (in-phase/quadrature) components. From these, the magnitude and phase of the reflected wave in relation to the transmitted wave can be obtained.

The two DC voltages unfortunately have an offset, but it´s good enough to see the magnitude and phase relative to the transmitting frequency.

However, I am not sure about the interpretation of the graph.

According the mode TE013: I selected the cavity dimensions for the target frequency 24.1 GHz  and the mode from TheTravellerEMD´s spreadsheet. Theoretically, this mode has been confirmed for that frequency.

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pomezi wrote 02/02/2016 at 22:16 point

Thank you for responding.

When do you anticipate beginning to test for "thrust" or displacement?

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Paul Kocyla wrote 02/03/2016 at 14:43 point

I started testing on the interferometer platform but didn´t get anything useful - i am not satisfied with the platform, it seems the sensitivity is not good, maybe the platform with everything on it is too heavy or the mounting still has some friction.
I´ll try a different approach: Switching RF on/off with a few hundred Hertz and measuring eventual vibrations by a mechanically coupled microphone-like sensor and FFT. I must take into account the charging/discharging time of the cavity else it won´t work.
The expected forces are just too tiny for good measurements, but i´ll give it a try.

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pomezi wrote 02/01/2016 at 19:44 point

Paul,  What does the Y axis represent and why are there no units there?

What does the red line represent?

I get the blue is magnitude and the green is phase, however can you explain the meaning and significance of those terms as they relate to this experiment?

What do you think this graph is show/not showing?

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Paul Kocyla wrote 02/01/2016 at 22:19 point

Y-axis:
blue -> magnitude of reflected wave
green -> phase of reflected wave
There are no units, because I am still working on the software.
I just take the ADC measurements from the I/Q mixer which contain DC offsets, so the phase and power information is disturbed but  anyway gives me the information i need. The values are not there for a precise analysis, they shall just help to keep the frequency at resonace once it´s  found.

Phase is atan(Q/I) and magnitude is sqrt(Q^2+I^2)

Theory:

I look for peaks where  the reflected power is minimal. Should the frequency drift away from that point, I can use the phase information to determine in which direction to correct the frequency.

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