Electromagnetic Engineering - Science topic

This is the typical signature if a bad contact (loose connector) somewhere in your setup

Dear Meenakshi

Please, see the following reference. It is a study about many wearable material parameters:

I hope to find the answer in the following pdf

The catch for the design of such kind of structures is the right combination of protein and silicon computers; the silicon computer in genal will not tell you the shape you should use..but once you have a shape in mind you can nicely analyze it in great detail which is not to easy for the protein computer (your brain); there are many books which discuss tansitions of all kind..but the gernal rule it..avoid sharp steps and try to implement for or less smooth transients from one cross-section to another...use you intuition there...and then ask he silicon computer jow he likes this.

Contact ANSYS support, They can give you better guidance, possibly without loosing your file and data.

You should know that this is not governed by quarter wave transition rules. A quarter wave transformer transforms between two different impedances not two impedances that are the same. The flare will introduce an effective lumped capacitance at the join and may be to compensate for other parasitic inductance or capacitance at the transition.

It probably isn't, but it may just be a badly designed transition. Not everything in published papers is good, especially if that wasn't the main point of the paper.

Hi

for applying phase differences in the spiral antenna generally use a compact feed network with a Wilkinson power divider. You can also use the following articles:

“Square-spiral antenna with unbalanced-excitation”

"Wide-beam spiral antenna with three folded arms fed by compact three-way Wilkinson power divider"

If this is a monopole then it is quarter wave resonant. You usually see matching slots in microstrip patches, which are half-wave resonant, however slots could still be used here to change the match.

Making the monopole round increases its bandwidth compared to a thin wire monopole. Thick monopoles have a wider bandwidth than thin monopoles. The shape of the ground changes both the match and the bandwidth, usually the match determines the bandwidth so changing one changes the other.

This is not a microstrip patch with a partial ground, it is a monopole fed from microstrip, with an edge ground rather than a flat ground perpendicular to the monopole.

Dear Meenakshi Kohli:

As you know, The polarization in which E field radiates energy in both the horizontal plane and vertical plane and in all the planes in between is known as circular polarization. In this polarization, electric field has two linear components which are perpendicular to each other with equal amplitude and 90 degree phase difference. The resulting E-field rotates in a circle around the direction of propagation. Based on direction of rotation there are two types viz. RHCP and LHCP. Circularly polarized light signal can be generated by passing linear polarized light signal through quarter wave plate (λ/4) at angle of 45 degree to the optical axis of plate.

############****

The advantages of Circular Polarization:

➨No polarization adjustment is required as it is fixed using OMT (Orthomode Transducer).

➨There is less chance of cross pol interference.

➨RFID reader does not have to be on the same plane and similar heights as RFID tags unlike linear polarization RFID reader.

➨RFID reader does not require to know the tag orientation unlike linear polarized RFID reader. Hence it is used for applications where one does not know the orientation of RFID tags while reading the data.

disadvantages of Circular Polarization

##########****

disadvantages of Circular Polarization:

➨It makes cost of antenna system higher.

➨It offers slightly lower cross pol isolation.

➨It offers shorter read range for RFID reader

You can benefit from this valuable article about your topic:

"Linear to left- and right-hand circular polarization conversion by using a metasurface structure"

Abstract:

By using a metasurface (MS) structure, a linearly polarized wave is converted to circularly polarized waves. Both right- and left-handed circular polarizations (RHCPs and LHCP) are obtained by a simple configuration in the proposed structure which consists of 16 unit cells arranged in a 4 × 4 layout. Each unit cell contains five horizontal and parallel strips embedded in a rectangular frame in which a single diagonal strip is placed from one corner to the opposed one. It is shown that the orientation of the diagonal line determines the handedness of the converted signal to be either LHCP or RHCP. In order to show the working conditions of the MS structure, scattering parameters are found for both co-polarized and cross-polarized responses. Axial ratio, an indicator for polarization conversion, is then obtained by dividing cross-polar response to co-polar response to demonstrate the transformation. The structure works for horizontally and vertically polarized linear waves in a wide band frequency range which is approximately 510 MHz. Since the suggested MS model is composed of a simple geometry for polarization conversion, it can be easily adjusted in any desired frequency bands for a variety of applications from the defence industry to medical, education, or communication areas.

@https://www.cambridge.org/core/journals/international-journal-of-microwave-and-wireless-technologies/article/linear-to-left-and-righthand-circular-polarization-conversion-by-using-a-metasurface-structure/E7C13343D20D53D7A113C8484F8A214F.

############

Also you can take a look at:

"Linear and circular-polarization conversion in X-band using anisotropic metasurface"

@https://www.nature.com/articles/s41598-019-40793-2

I hope it will be helpful...

Best wishes....

Yes, I would like to receive this code. Thanks very much for your general sharing.

Please send to this following email: zhaoliang0526@163.com. Thanks.

Hello,

Few papers are attached for your help.

Thanks,

During alternation voltage source, dielectric material lead losses due to polarization, so we use minimum dielectric material constant for insulators.

Best tools you may try

1. Microsoft word

2. LATEX

3. Scrivener

4. Freedom

5. Google docs (online)

According to your pictures, you are talking about very short cylinders, and in this case, I guess it is not required that the strength of the force is independent of the z component of the position (if z is incident with the axis of the cylinder).

If you place a ferromagnetic ring coaxially inside the left configuration it will indeed experience a radial force toward the magnet. The total force on the ferromagnetic ring will be zero, of course, but if it were made from an elastomer filled with ferromagnetic particles, its diameter could increase under the influence of the magnet.

I'm not sure yet about the right configuration.

Please find an article dealing with shielding of static magnetic fields here:

Dear sir:

Thank you for sharing this important and valuable information .....

With best wishes....

BTW, I did not know that direct notation with quotes works!

I usually use the global (project) notation with "$" prefix. Like $eps without quotes. It was required in older versions to use global $parameters in the material editor.

Do you specify your "eps" on the design level?

Dear Franklin:

I agree with the opinions of my colleagues mentioned above, that it's difficult to find the problem since we can't see all the settings.

But you could benefit from this valuable article about your topic:

"Heat Transfer Modeling of Power Cables in Tunnels"

@https://www.comsol.com/paper/heat-transfer-modeling-of-power-cables-in-tunnels-18877.

Electric power, in cities or for power plant outflow, is most often transmitted through underground cables. Due to increased electricity demands power suppliers make large investments to house these cables in deep or shallow tunnels.

The thermal environment is complex, with different kind of cables placed in different configurations, transmitting different powers. These are hard to take into account theorically, so thermal simulations using COMSOL Multiphysics® software were undertaken to measure the inaccuracy of the empirical models.

The Conjugate Heat Transfer interface is used, 2D and 3D models were developed and showed that several hypotheses lead to underestimation of the hottest cable temperature and two interesting possibility for improvement were found: the heat transfer correlations and cables proximity effects.

I have attached the pdf files ....

I hope it will be helpful...

With my best regards ...

Hi Yechiel Asraff ,

Yes, that's essentially what both Malcolm White and I were saying initially. In the far field, the magnitude of the S21 is just given by the Friis transmission equation where the gain of the isotropic radiator/receiver is set to 1.

Now, on the phase, I see that you responded to Malcolm about the same time I was replying initially and since it posted above mine, I hadn't seen that in later posts. You're generally on the right track. Essentially, again in the far field, you can use e^(-ikd) to produce the radial phase shift. The question is what the angular phase behavior looks like, and as you indicate, includes both polarization as well as position. In the far field, there's no radial (longitudinal) component of the field, so if we put Z along the direction of propagation, that just leaves you with the X and Y components at an isotropic field probe. So, we're back to needing two components, just as you allude to in your response to Malcolm.

So where do you get them? The answer is pretty simple. You need a vector antenna/radiation pattern for the antenna creating the field. Any complete spherical radiation pattern requires measurement of two orthogonal polarizations at each point. Often, we only think of the scalar components to get a total power/gain in each direction, but if we want to understand circular/elliptical polarization components, etc. or perform near-to-far-field conversion, it's necessary to keep the relative phase information for each component. Once you have that information, you can work out your far-field magnitude and phase for each of the two components by applying the appropriate distance correction.

This shouldn't be surprising if you consider that's essentially how the pattern was obtained to begin with. Whether through direct far-field measurement or near-to-far-field conversion, the pattern is determined by measuring two orthogonal polarizations at a fixed distance from the antenna under test (AUT) creating a spherical surface around the AUT. From that, we know the magnitude and phase of two orthogonal polarizations on that surface and can calculate the magnitude and phase for any other spherical surface (or other arbitrary surface if we wanted) around the AUT. After all, that's what near-to-far-field conversion does. It's just more complicated since the field structure changes between near and far fields, while far-to-far-field can just be determined (or at least estimated) by the radial change.

Hope that helps.

Michael

Dear Mridul Verma

I suggest you to go through the following articles:

1. https://arxiv.org/pdf/1806.04574.pdf

2. https://etd.ohiolink.edu/apexprod/rws_etd/send_file/send?accession=osu1274730653&disposition=inline

3. https://www.irjet.net/archives/V6/i3/IRJET-V6I31355.pdf

Kind Regards

For every metal (or material) used for coil (or other devices) in production of em waves, there should be a minimum required voltage vr for production of em waves.

The impedance of an antenna can be anything from a few ohms to very high. A properly designed antenna will match to the impedance of the driving source for optimum power transfer. The 50 ohm value of the port is arbitrary and can be set to any value desired. Cable impedances come in many different values, such as 50, 75 and 300 ohms. Sometimes a low value antenna impedance is desired such as 10 ohms when connected to a low impedance solid state circuit.

Hi,

You See Rotman Lens Antenna, it's the same exemple,

Hello,

few papers are attached....kindly go through and clear the doubts.

Thanks,

Hello,

you can refer these papers for simulation in HFSS.

Thanks,

Did you mean helical antennas? I think 400 MHz to 900 MHz is a very wide band for a helical antenna.

Dear Meenakshi Kohli ,

You have to investigate and improve the matching between the source impedance and the input of the UHF port. You can measure S11 and see whether the resonance center frequency is lies at the minimum of S11. The minimum must at least lower than S11= -10dBs. May be you need to fine tune the path to the UHF antenna. Also, the radiation resistance may be smaller much deviated from the source resistance.

Best wishes

Meenakshi Kohli you can use a plane wave test source in a room with the EM wave pointing towards the window side (open wall). Use low power at the test source. Keep the AUT in between the test source and window at far-field distance. This should work for small antennas whose dimensions are small compared to window opening. If the window can be opened, you can open it for tests.

1. The Directivity Gain of the helix is directly proportional to spacing (S) between the helical turns.

Hence, Higher directivity can be achieved by increasing the spacing (S) between the helical turns results.

Pitch Angle (alpha) and spacing (S) between the helical turns are directly proportional:

Spacing: S= C tan (alpha);

Hence, increase in pitch angle (alpha), results in increase in spacing (S) between the helical turns and it will results in following advantages.

Good question

Length of the Helical antenna gives its Axial Length, A= NS. Axial Length A=NS, value also gives the modes of operation.

The value of length of helix, NS can be selected based on the following conditions

1. A=NS must be much smaller than wavelength, Lamda of helical antenna. It gives maximum radiation along the axis of helix. (End-fire radiation)

2. Directivity is directly proportional to the axial length NS. for higher directivity number of turns in helix must be more.

Directivity, D= {(15NSC^2)/(lambda)^3}

3. Axial ratio (AR)= {1+(1/2N)}, Number of turns must be more to reduce axial ration.

4. HPBW and BWFN are inversely proportional to square root of axial length. Therefore for unidirectional radiation NS value must be more.

In general if number of turns is more then it gives high directivity and almost unidectional radiation.

Comparative study on Japan n Korea... In recent years, the development and market participation of major makers of next-generation eco-green vehicles has been accelerating. Consumer interest has also increased. Consumer characteristics, consumption type, characteristics of next-generation eco-friendly vehicles, and government policies on next eco-green vehicles. In Korea, there was no significant difference by gender, age, monthly average income, and consumer type. However, there was no significant difference in purchase intention by gender, age, and monthly income, Respectively. In the case of Japan, there was no significant difference by gender, age, monthly income, and consumer type. In Korea, on the other hand, images such as brand, color, and design have positive effects on eco-friendly vehicles. In the case of Japan, image and stability have a positive effect on consumers' purchasing behavior. Therefore, it is important for Japanese consumers to consider not only the image of purchasing an eco-friendly vehicles, but also the safety of the vehicles body, appear. In the case of Korea, the socio-environmental value-seeking type has a significant relationship with the purchasing intention. In the case of socio-environmental value-seeking type, the government's support policy such as carbon dioxide tax, direct support from the national or local governments, gasoline tax, Carbon tax and fuel related tax relief showed positive effects. In the case of Japan, the price-seeking type and the socio-environmental value-seeking type were found to have a significant relationship with the purchasing intention. Both the price-seeking type and the socio-environmental value-seeking type showed that the carbon dioxide tax, Direct support, gasoline tax, gasoline tax, and carbon tax, etc. have positive effects... Yim, K. H., & Chong, M. Y. (2017). A Study on the Influence of Consumer Type on the Choice of Next-Generation Eco-Friendly Vehicle and Consumer Purchase Intention-Comparative Study on Japan and Korea. Journal of digital convergence, 15(11), 133-146.

You do not seem to understand microwave components at all. You need to be very careful, or else things will not do what you expect them to. You need to read about microwave components.

A transformer that uses a 70 ohm section I expect is a quarter wave transformer which will match 100 ohms at one end to 50 ohms at the other. The splitter sees two lines going away from it in parallel. For the 50 ohm line to be matched the two lines need to be 100 ohms each so that in parallel they are 50 ohms.

A 70 ohm line quarter wave long is a standard inverting transformer which looks like 100 ohms at one end if there is 50 ohms at the other, so if it has a 50 ohm line going out it presents the 100 ohms at the other end that the single input line needs at the split.

To get from one 50 ohm line to a 250 ohm line you need a quarter wave long line of impedance square root of 12500 ohms, which is close to 111 ohms.

The lines are almost never exactly a quarter wave long because the steps in size look like capacitors which have a similar effect to extra line length, so the line lengths are usually shorter.

If the transformer doesn't work at the frequency you want, find out which frequency it does work at, then if that frequency is too high or low, make the quarter wave section longer or shorter by the ratio of the two frequencies, which will get you very close.

The thickness of the metal has a much smaller effect than the width of the metal and the thickness of the dielectric, but it does have some effect. The empirical formulae for impedance use width, and an effective width can be used in these formulae. The effective width is calculated by a simple formula that includes the thickness.

Any good conductor, e.g. a metal surface, reverses the direction of circular polarization on reflection, for all frequencies for which it is a good conductor.

It all depends on the parameters...what are you REALLY interested in..the field vs current ar one point..the field homogeneity..saturation properties etc etc..you may find a lot of hint in the IMMW proceedings (Intl magnet measurement workshops)and Also on the JACOW pages as well as in the CERN library ...CDS CERN..(all public access with free downloads.In addition you may look into the CERN accelerator school proceedings for magnetic measurements (via CDS CERN)

Hi Mohammadreza Arab ,

I wasn't sure how to insert Greek characters in RG answers, so my0 stands for the permeability of vacuum = 4 * pi * 10^-7.

From the CST help page

Directivity: The directivity of an antenna is defined as "the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions." The radiation intensity is given by the total power radiated by the antenna divided by 4p:

📷

Gain: Accordingly, the gain is defined similarly but is related to the input or accepted power of the structure. In the case of a loss-free antenna (no conductional or dielectric losses), the gain is equal to the directivity. Note, that power flowing out any port is not considered as accepted by the structure.

📷

Realized Gain: The realized gain is defined by gain * (1 - Balance^2), it includes the impedance mismatch loss.

E-field pattern: The electric-field pattern provides a distance-independent characterization of the radiation pattern. It is directly related to the electric field evaluated using the farfield approximation:

📷

Due to its definition, the E-field pattern has the unit of a voltage.

Radiation efficiency: The antenna radiation efficiency is defined as the ratio of gain to directivity or equally the ratio between the radiated to accepted (input) power of the antenna:

📷 or 📷

Total efficiency: The total efficiency is defined as the ratio of radiated to stimulated power of the antenna:

📷

Compared to the input power, the stimulated power considers any occurring reflections at the feeding location.

Reflection efficiency: The reflection efficiency is defined as the ratio of input to stimulated power. Note that the input power is the accepted power, i.e. reflected power and power flowing out any port of the simulated structure are not included.

📷

See? for example, A.A.Kirilenko and A.O.Perov, “On the

common nature of the enhanced and resonance transmission through the periodical set of holes,” IEEE Trans. Antennas Propag., vol. 56, no. 10, pp. 3210–3216, Oct. 2008. + references

ISU general symbols for universal dictionary

m for meter....

10e-3 for mili.....

The International System of Units consists of a set of base units, derived units, and a set of decimal-based multipliers that are used as prefixes.

I am agree in a totality with Jonathan Magnes statement he quoted in his answer of this question.

Ashish

Adding to the colleague above, I would propose to shield the critical parts of the circuit against the interference by near or far electromagnetic radiation sources. This can be accomplished by using ground planes.

Te other solution may be to use balanced wire system such that the common mode signal will be cancelled.

The last precaution is to reduce the impedance level in the circuit such that any induced voltage will induce little or negligible current.

Best wishes

Thanks Rafia Raees.

You are using the so called cold noise measurement technique. This type of measurement using measured s parameter data and noise power values obtained from source pulling about a reflection coefficient with a Gamma of 0.5 or so. Be certain that the device is stable and check to see if the s data returned during measurement makes sense. Is the device matched? As a sanity check that your cal is good, measure a simple item prior to your LNA DUT. A 3 db pad should return ~ a 3 dB NF.

Dear Mohammad

You may search within

these references

http://www.math.ubc.ca/~feldman/math/telegrph.pdf

https://www.sciencedirect.com/science/article/pii/S1007570415001677

Good Luck

i am working on mmwave patch antenna design....what should be the outer and inner diameter of a coaxial cable feed??

I have found for my frequencies 1.85mm and 2.92mm k type connectors are suitable...Is that good one...

Hello,

To measure parameters like permittivity and permeability, it is the transmission lines that is used in transmission and/or in reflection mode. for better understanding of this type of measurement, you can read this application note.

Thanks,

The effect depends strongly on the AC frequence.

I would like to remind my distinguished colleagues that ResearchGate is about scientific research based on the scientific method. Therefore, I believe that RG is not a good place to discuss usefulness of pseudoscientific devices like "Quantum health scanner". Apparently, the use of similar devices has been banned in the US.

Hello,

Practical Rf Circuit Design for Modern Wireless Systems, Volume II: Active Circuits ( by Rowan Gilmore (Author), Les Besser (Contributor) )

An Introduction To RF Circuit Design For Communication Systems 1st Edition

( Roger C. Palmer (Author) )

Thanks

yes, i think it is possible.

I believe yes, Amir hossein Aref it depends on what/which molecule you are considering. As for example if we consider weaker bonded CH3CL, in which C-Cl specifically. Then we can calculate the energy require to break this bond. Like for 9 debye the breaking energy lies near about 3.5eV.

So theoretically you can break these like weaker bonds using electric/magnetic force, And if you can build a machine which such capabilities you can also practically break these type of bonds.

Dual band refers to a device which uses two different frequencies to communicate.

Dual radio refers to a device which uses two different protocols to communicate.

Maybe an illustration would help. A dual band device is like a person at a party who can move between two different rooms (different frequencies) to talk with other people, while a single band device would be limited to talking to people in only one room. On the other hand, a dual radio device can speak with people who speak in two different languages, while a single radio device can only speak one language.

A dual radio device is typically used as an intermediary between two different networks like 802.11 (like WiFi) and 802.15.4 (like many wireless sensors).

Dear Baraa,

Thank you for sharing the details of your FSS design with us. I assume that the parameters of your periodic FSS structure are those of a square or rectangular lattice? From what I remember about FSS measurements in rectangular waveguide simulators, the lattice of your perodic structure must be at least rectangular in form and you need to place two unit cells side-by-side across the broad dimension of the waveguide. This is to emulate the correct symmetry and periodic boundary conditions of the full lattice. Did you use side-by-side elements in your waveguide simulations and measurements, or just one element? You can think of this two-element arrangement as generating an infinite set of image elements with respect to the side walls of the waveguide. You would be not able to simulate a triangular lattice in a rectangular waveguide, for example. Whilst I would fully expect your computed and measured results to agree well for whatever FSS element you place in the waveguide, the trick in an FSS waveguide measurement is to mimic the actual periodic boundary conditions that occur in a full lattice. If you've only modelled and measured a single FSS element in the waveguide, the results would not pertain to the same lattice parameters of a fully periodic (free-space) structure involving that element. My previous comments about the plane-wave decomposition and frequency-dependent angle of incidence in the waveguide measurement would still apply to the case of two side-by-side elements placed in the waveguide.

Regards,

Ray

Thank you very much for your help, Dr. Søren Kyale

Two points:

- The inner diameter of the coil has to be larger than the outer diameter of the magnets in order to let the battery-magnets-assembly move freely.

- The polarizations of the magnets have to be directed in opposite directions.

If you would just like to amaze your students by a simple setup which produces (rotary) movement you can avoid the tedious task of winding a long coil: Just take an AA-battery, one magnet, a short chipboard screw (made from steel) and a short piece of flex wire. Put the magnet on the head of the screw, connect the upward pointing tip of the screw to the negative pol at the bottom of the vertical battery. Due to the magnet, the screw and the magnet will hang from the bottom of the battery. Connect the wire to the positive battery pole, and touch the side of the magnet with the other end of the wire. Magnet and screw will start to rotate fast.

Positivity (positive attitude) leads to the hope of improving the disease and in my opinion it really accelerate the speed of recovery from a disease.

For curing cancer pranayam (breathing practices) and meditation are really beneficial.

Dear Yuze,

What has been by the colleagues is okay. It is so that alternating current will cause an alternating magnetic field in a plane normal to the flow of the original ac current. This alternating magnetic field will induce secondary alternating current which aids the current nearer the surface and opposes the primary current flowing in nearer the interior. It follow that the current will be nonhomogeneously distributed at the cross section of the conductor where the current is more concentrated at the surface region.

So, the skin effect is the consequence of the induced secondary eddy currents. This effect is always present irrespective of the thickness of the conductor. It is advisable not to make the conductor thicker than the skin depth to save materials of the conductors. However the skin effect is always present irrespective of the thickness of the conductor.

Best wishes

Hi Smrity,

Thank you very much for your answer and the paper. The SIW paper is very interesting! I could use it for a fanout design in one of our boards.

Best regards,

Wei

When electric charges are moving, stationary charges beside them feel a stronger force than if they are not moving. Stationary charges in front of and behind them feel a weaker force. This can be pictured as distortion of the lines of force by relativistic length contraction - some lines of force move from in front of and behind the charge to the sides. When electrons move and their associated positive charges don't then there is an imbalance in the forces from the two that we call magnetism.

Magnetism is only what electrostatics look like under relativity.

The charges don't change when thy are moving, the space and fields around them become distorted to us, creating imbalanced forces that we call magnetism.

In the solenoid, the electrons are moving, but the positively charged metal lattice doesn't move, so there is an imbalanced force from the two, in most directions.

People have achieved negative absolute temperatures but that is in nano kelvins by magnetic cooling. However the temperature we refer as zero kelvin is actually a little above absolute zero. So basically the negative temperatures we are talking about a temperature above absolute zero that will radiate for sure. But nobody knows what is the absolute zero but be sure it will be some fractions of kelvin below 0 K. I think getting a temperature even like -1 K is hypothetical.

Given that graphene is IR transparent, yet highly conductive, it should provide a workable window for most any Faraday cage.

I just skimmed the article but I think this may work as a window too, unless the substate blocks IR...

Then all you would need is a... https://www.fishersci.com/shop/products/fisher-scientific-traceable-noncontact-infrared-thermometers-3/p-203736

I am not 100% on this. However, I believe it is worth some experimentation.

All Negative criticism greatly appreciated.

Time-varying magnetic fields may heat in 2 different ways:

Regarding your setup (dielectric between capacitor's plates), I'd guess that the dielectric is shielded such that it won't be heated directly. But the plates might be heated (currents induced), resulting in indirect heating of the dielectric by conducted heat.

Yes, it was done using horizontal light beam. See the paper on the effect of light on gravitational forces by light.  Rancourt and Phil.  Tatersall. More experiments are being done this summer using blue laser light.

Thanks so much Mr. Malcolm , Mr Rusan and MR Sudipta 

Hi Akhilesh,

Well, it all depends on your operating frequency. SMA is no good above 26.5 GHz, generally. When you said 1-2mm, I assumed you meant that was the wavelength (in free space), corresponding to about 150-300 GHz. If, instead, you mean that the antenna is 1-2mm in size, perhaps half a wavelength or smaller if used on a high-dielectric constant substrate, then it could be below 100 GHz.

Up to 110 GHz, you have the option of using 1mm coax -- but I can tell you from experience that the connectors, adapters, and cal kits for measurement are EXTREMELY expensive, and frankly don't perform very well. (I had to test a part once in 1mm coax where the performance of the part was far better than that of the test adapters, making the test practically meaningless). I wouldn't recommend it.

Really, for anything above 50 GHz, I would use waveguide. Waveguide to printed-circuit launchers can be made, but are typically custom. If you're geometry just wouldn't support a waveguide housing, then the best I can suggest is to test your antenna on a wafer probe station. Mm-wave wafer probes are readily available, but depending on what you want to measure (beam pattern, etc.) the geometry could be awkward.

Matt

@ Joseph Kay

Your problem is not exactly "... wire in air ...". Your wire is affected by the position-dependent variations of the "magnetic path" of your motor. This comprises - aside from the path through rotor and stator - 2 air gaps. The whole setup is such that the permeability of the path varies with the position of the poles of rotor and stator versus each other. This effect is well-known from BLDC/EC motors and can be used to measure the rotor position.

In principle this setup can be calculated, though a lot of parameters are required and the calculations are non-trivial. If you can get access to some appropriate simulation software (COMSOL and alike) you might get an impression of the changes, geometries and alike. Otherwise you could measure the inductance - gradually (eg. 1 ° per step) rotating the rotor between individual measurements and plotting the results.

Regards