UnknownEditor replied to the topic: Solid State Microwave Ovens

Just went to talk on this topic at IMS 2016. Cost is slightly lower than $1/W right now for solid-state amps for commercial heating. An order of magnitude price reduction is needed. Don't hold your breath waiting to buy a SS oven any time soon.

madengr replied to the topic: Solid State Microwave Ovens

I read somewhere the cost of a consumer oven magnetron is $5 to $15. I suppose until the price of LDMOS gets down to that, you won't see it happen. You still need all the other components anyway.

UnknownEditor replied to the topic: Solid State Microwave Ovens

Not Exactly Phillips (NXP) has been showing solid-state ovens at IMS for the past three years. I would have expected this to be on the market by now, but it is not. If you are it IMS 2016 next week you could ask them what is going on.... I plan to visit that booth.

Steve

www.electronicsweekly.com/news/design/th...solid-state-2016-01/

andysek replied to the topic: Impedance of free space

Direct Z measurement is not possible, as is the "normal" R resistance.
We know that Z is a coefficient, convenient in practice and defined as E / H.
(more on theory, for example in the book V.Volman Engineering Electrodynamics).

By definition - Z = E / H

It is therefore necessary to measure E and H at a given point. this can be done using a field level meter, eg SMP2 WaveControl. The polarities of both vectors should be perpendicular to each other and to the direction of the source.

The second method involves the use of power gauge measurements. We measure E and P (power - using a power meter). The power meter antenna should be calibrated to an isotropic antenna.
Then S = P / A, S - dense power (Poyting vector), A - effective area of the antenna aperture.

hence S = E H or E ^ 2 / Z

with E ^ 2 / Z = P / A

Z = E ^ 2 A / P
The measurements are best done in the anechoic chamber.

Microwaves101 replied to the topic: Impedance of free space

I like the idea of measuring permittivity of free space E0 by a testing a capacitor. Then solve for eta=1/(c x E0)

Steve

tc replied to the topic: Impedance of free space

Z=Sqrt(L/C) it works both ways. The L and the C are usually per unit length but lumped values are frequently used.

steve barak replied to the topic: Impedance of free space

Z=Sqrt(L/C), but I think it's a distributed parameter, not a lumped one. Think Transmission Lines.

Desert Sage replied to the topic: Impedance of free space

The ratio of mu zero to epsilon zero has units of ohms (per meters cancel).

In a carefully controlled experiment with parallel plate capacitor with plates spacing settable with micrometer precise epsilon zero can be determined empirically. Know or measuring the speed of light you can solve for Z zero or mu zero.

Hertz measured wavelength in earliest of experiments and if he knew frequency he would know the speed of light. (He basically used reflections off a wall and a probe to measure VSWR without a slotted line.)

I am sure there are many ways but not too easy or we would have done experiments in EE or Physics labs!

madengr replied to the topic: Impedance of free space

Well if a 50 Ohm coaxial airline is measured to be 50 Ohms, and the dimensions are exact, then E0/u0 have the same ratio in the airline as in free space, so free space must be 377 Ohms/meter. I suppose the historical direct measurement is the speed of light c=1/sqrt(E0*u0), but that still leaves an unknown term. Some smart people obviously figured it out.

I suppose if you had a hypothetical sheet of material of 377 Ohms/sq. then it would have no reflection, but any material has Er>1 so you'd still get a reflection. Once, on paper, I came up with an tapered lossy line of sheet resistance, that if you made it infinitely long, would have zero reflection down to DC. Making it shorter should provide a good termination without needing a ground connection at the other end. Of course any infinitely long line would do that, but the taper let it use an arbitrary sheet resistance and start at a width of arbitrary Z0. I suppose something along those lines, but in 3D.

N10sive replied to the topic: Tuning U.FL / Antenna Cable Assemblies

If you are talking about a module, it is most likely the supplier assumes a 50Ohm line and that the U.Fl SMT connector is 50Ohms.

In a finished product with an antenna, the manufacturer has most likely "tuned" the antenna to the desired frequency without using a matching network.

In the case of cellular, it is also difficult to have a desired matching network, for a multi-band antenna etc. There are also less stringent parameters specifications for VSWR in cellular, at least in the lower bands.

This is also due to cost, efficiency, space-constraints, etc.

Dave replied the topic: earthing quality measurement with an antenna

Probably not to any useful degree.

It sounds like what you want to do is a Kirchoff current loop using the air interface as a known impedance to close the loop. If that's so, you've also got the coupling from free space into the earth terminal to consider.

I think you'll run into problems with mismatch between the source and the antenna, mismatch between the antenna and the earth terminal, variations in the distance between the antenna and earth terminal, possibly polarisation, and maybe also multi-path effects all adding uncertainty to the measurement.

Interesting idea though.

Microwaves101 replied to the topic: Calculate antenna gain from measured data.

This reply came from an actual antenna engineer, not some poseur like me...

"A common way to get gain from measured antenna data is to use the substitution method, i.e. using the exact same range setup, swap out the antenna under test with a standard gain horn and measure the horn antenna. You may need to measure multiple standard gain horn antennas to cover the frequency band of your antenna under test measurement.

Compare the raw measured amplitude of the SGH to the raw measured amplitude of the AUT and use the reference gain curve of the SGH to determine gain."

Hope that helps,
Steve

VladVlad replied to the topic: Calculate antenna gain from measured data.

I think you can calculate first an antenna directivity D and full radiated power Prad using your far-field measured data. Next step is to estimate the power Pdeliv delivered from the source generator to the antenna input port. Pdeliv ~ Pgenerator - Ploss - Preflected. Then the antenna gain G =~ D*Prad/(Pgenerator - Ploss) where Ploss is the attenuation in all circuits between the antenna input and generator.

If you need more help send me email vvolmanatemfieldbookdotcom and check website <a href="http://emfieldbook.com" target="_blank" rel="nofollow">emfieldbook.com</a> Wing

Desert Sage replied to the topic: Online Calculator to design Circularly Polarized Microstrip Antennas

I clicked on link on www.edaboard.com and it works from there but not the link here. Don't know why?

dfmona replied to the topic: Online Calculator to design Circularly Polarized Microstrip Antennas

Sorry for the inconvenience, I messaged a colleague in FT. MAYERS Florida USA, he tested the link and said it was working, its probably gonna take some time to work around the problem. In the meantime, I could provide you with some pictures of some results of the online tool if you are interested.

Desert Sage replied to the topic: Online Calculator to design Circularly Polarized Microstrip Antennas

New Mexico, U.S.A.

dfmona replied to the topic: Online Calculator to design Circularly Polarized Microstrip Antennas

Hi, I verified the address seems ok from my side of things, where are you from? maybe is a country thing that we need to work out over here.

O and we added two additional tools.

www.lap.ele.ita.br/microwave_tools.html

Desert Sage replied to the topic: Online Calculator to design Circularly Polarized Microstrip Antennas

The link does not work. Please verify address.