Questions tagged [microwave]
Microwaves are radio waves with a frequency from 300MHz to 300GHz which corresponds to a wavelength of one meter down to one millimeter. Often in RF engineering however it is used to refer to a narrower region such as 1 to 100GHz.
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Underwater communication trough cable
I wanted to build a device which can stay and move underwater (let's say, for instance, 15m underwater).
Since RF frequencies are very attenuated by water and VLF antennas would be too high, I was ...
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What makes conical coils that good in microwave circuits?
Conical coils are often used in microwave technology.
Can someone explain what makes this shape so unique? How does this shape affect parasitic capacitances?
Some conical coil photos:
This is NOT ...
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Is MIMO equivalent to link aggregation?
Is MIMO the wireless version of link aggregation in wired networks?
I'm not asking if MIMO is a similar link aggregation protocol like LACP or PAgP. What I'm asking is, if it is the same concept as ...
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Jacket diameter of coaxial cable : how to read those documentations?
Before anything: I am not an electrical engineer: I don't know very much coaxial cables (just the very basics). I need to do some orders of magnitude calculation of heat transport of typical coaxial ...
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Upper RF limit in discrete design
I was curious, what is viewed as the practical upper frequency limit of circuits using discrete components?
It's well known a 20Ghz oscillator is hard to design using discrete components due to the ...
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Spherical waves in far field region
in my antennas book (I do not put its reference because it is not in english) it is written that, at high distance from the source, the electromagnetic field radiated by it is a spherical wave.
This ...
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Advice needed for replacing a microwave fuse
The fuse from my microwave blew out last week. I removed the fuse and measured it with a multimeter to confirm the problem (It was measuring as infinite resistance)
The fuse cap reads the following: ...
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Can these S-parameters be derived?
I have been trying to derive the S-parameters of a lossless T-junction of transmission lines. Here's a diagram from Google:
This is an exercise in microwave network analysis, not in design, so the ...
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How to choose a 50 Ohm RF attenuator for radio, bluetooth and wifi power measurements
I have built a power meter with AD8318, a chip which contains a logarithmic amplifier, often used for power measurements.
I have read its datasheet and it is written that the maximum input power is ...
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Reasons to use open circuit stub over a short circuit stub
I am having trouble with this question which states: suggest two reasons why the use of an open circuit stub might be preferable to a short circuit stub in microwave circuit design (microstrip)
Could ...
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Dielectric slab waveguide
let's consider the so called dielectric slab waveguide (references for image and equations: here, page 53):
I do not know much about it, I know only that it is a planar guiding structure which is ...
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Elliptical polarization and waveguides
It is known that a generic harmonic electric field which propagages in free space has an elliptical polarization (if you want to read the proof, look at this, slides 72 - 99).
My question is: what ...
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Switch Mode Power Amplifiers
Suppose that in a switch mode power amplifier (class E or F) a 100% "non overlap" of current and voltage waveforms is achieved at the drain or collector.
How would there be any output power if there ...
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Trace width for breaking out 100Ω differential microstrip from 0.5mm pitch BGA
See bottom of post for the actual questions
First, some context:
I'm making a DisplayPort switch as a hobby project
DisplayPort's high speed lines require 100Ω ± 10% differential impedance, which I'...
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Is it safe and feasible to use a "damaged" transformer?
I want to make my own DIY spot welder, so I'm trying the instructions I found on several places (for instance, here, here or here) about using an old microwave transformer. I salvaged it from a broken ...
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Is it safe to touch 8 volts?
Let me say first that i'm a noob in electricity.
I measured the voltage from my diy microwave-transformer-welder and it was 8.
I have no idea how much amps run through it but the fact that it creates ...
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Drive a magnetron with low power via a CCFL backlight driver
[EDIT] My real question here is: can a magnetron from a microwave oven be used to output low power microwaves? If so, how can I achieve this? If not, what is a source for low power microwaves? In this ...
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Waveguide excitation through coaxial antenna
let's consider a waveguide excited with a coaxial cable antenna:
You may see that this structure is sized with a distance between the antenna and the plate equal to \$\lambda/4\$. My professor has ...
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One port Vector Network Analyzer (VNA) Calibration without the given standard Calibration Kit
I am trying to do a one port VNA calibration for measuring filters at the GHz band. The VNA that I am using is Keysight E5063A. However, I am running into some conceptual as well as some practical ...
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Why don't these even/odd mode transmission line results math up?
In Pozar's Microwave Engineering, he analyzes the Wilkinson power divider using even-odd mode analysis. His results match the expected values and power conservation is satisfied. Similar derivations ...
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Attenuation and Insertion Loss for a 2 port network
in my university lectures the insertion loss and the attenuation of a 2 port network have been defined in the following way (and I have an extremely basic question about them):
the Lnsertion Loss L ...
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What piece of technology is able to record the exact phase of microwaves?
I had this question on the physics community, but I thought this would be appropriate to cross-post here.
I read that in VLBI, the signals of microwaves (on the millimeter scale) are recorded and ...
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Can I replace this filtering network with a saw filter chip?
The above image is the Application Circuit from the A7105 radio transciever chip's data sheet.
I think I am beginning to understand the purpose of most of these components.
I suspect that the ...
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Why does 1/4 wavelength have a ground plane and 1/2 wavelength needs none?
Why does 1/4 wavelength have to have a ground plane and 1/2 doesn't?
I know that an antenna that has half a wavelength does not need the ground plane (example a dipole antenna) and when using a ...
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Change closing transistor to opening in a Microwave Radar Switch?
Preamble: I have little knowledge of electronics in detail, but I know how to solder, have a working brain and am fearless :)
There are many low-cost Microwave Radar Switch PCBs out there (very ...
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"Rigorous" motivation behind the model of transmission line for microwave engineering
I am trying to understand under a rigorous enough point of view the model of transmission lines.
More specifically I am interested to this question under the context of microwave engineering.
...
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How to rewind microwave transformer to isolation transformer
I'm thinking of getting an auto transformer and rectify it to make mains isolated 240V 8A DC power supply. I would like to know if its possible to rewind an old microwave transformer to 1:1 isolating ...
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How to unground microwave transformer
I'm trying to make MOT tesla coil and would like to connect secondary coil in series. The low voltage end of secondary is connected to the body of the transformer. I don't particularly want to ...
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How is it possible that emitting electrons create alternating charges in the cavities of a magnetron?
In a magnetron, electrons are emitted from the cathode and create alternating charges in cavities (fig). These alternating charges produce oscillations in the cavities which result in electromagnetic ...
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What are possible defences against Frey effect? [closed]
"Frey Effect" is named after Dr. Allan H. Frey, an American neuroscientist, who first published information about microwaves causing humans to hear sounds, including clicks, voices, etc. Frey Effect ...
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How does a microwave oven modulate its output power?
My microwave has multiple power settings, ranging from 500 watts to 1500 watts. My question is how is the power reduced/modulated?
I can think of a few options (but I don't know which one is correct/...
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RLC equivalent model and Impedance Smith Chart
I have done some impedance measurements on an unknown 1 port device. I have measured its impedance at different frequencies (from 10 MHz to 600 MHz) and I have seen it on the normalized (on 50 Ohm) ...
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Meaning of "raised structure" in microwave networks
Can you help me to understand what "raised structure" means and why it determines the following property of the S matrix?
Reference: here.
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Path of a signal traveling on a mismatched transmission line
I have a basic question about the path of a signal traveling on a transmission line with a short circuit as termination.
Suppose that this line is driven by another line (at left) with Zc = 50 Ohm ...
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Low Pass Step and Low Pass Pulse sith Vextor Network Analyzer
I have an extremely basic question about time domain measurements with Vector Analyzer. It is something that is not explained in simple words in all datasheets/guides (maybe they think it is obvious ...
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How is a transmission line with a different characterisitc impedance shown on the smith chart?
A transmission line can be shown on the smith chart as a clockwise rotation, each 180 degrees corresponding to a quarter wavelength. But this is when the characteristic impedance (Z0) of the ...
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How does this coupler work?
I've bought a few 50MHz-6GHz directional couplers (SEDC-10-63+,) each for 75$. Here is a picture of this expensive coupler:
Unfortunately one of these couplers was not working from the beginning so I ...
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Time Domain Measurements with Vector Analyzer
In my university I have done some time domain measurements with a VNA (by using the transform operation of the instrument). Precisely, I have selected the measurement of the real part of S11 while ...
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Definition of quality factor as function of frequency
I have seen that some electrical components (which contain R,L,C elements) datasheets shows the curve of the quality factor Q with respect to frequency, and not simply its value at the resonance ...
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Meaning of coupling factor for a resonance cavity
I was reading this paper about resonant cavities, and on page 6 it introduces the concept of coupling factor β, which is defined as the ratio between the power loss in the total circuit (including the ...
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Can a Unilateral Amplifier be Unstable?
When designing microwave amplifiers, stability is an important factor to consider. Stability is usually measured with the K factor. In a unilateral network, S_12 = 0, and this makes the K factor ...
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Magnetic field expression in a rectangular waveguide
I was reading the chapter of Fundations of Microwave Engineering (Robert E. Collin) about transmission lines and waveguides, and I have a question about the electromagnetic field in a rectangular ...
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How to block / lessen EM-radiation/signal from home Wi-Fi router? [closed]
1) What materials and how can I use to completely block radiation from two antennas of my WiFi router?
2) What materials and how can I lessen by 20-50% radiation/signal from the third router antenna?
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Attenuators in Waveguides
Let's consider for instance a rectangular waveguide with TE01 mode.
As shown here, a possible attenuator may be realized with a metal card placed so that it is tangential to the electric field. Here ...
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Reflection Coefficient with Electric Field and Voltage
In different situations the input reflection coefficient (of a waveguide, of a transmission line etc) is defined differently.
Wikipedia says:
The reflection coefficient may also be established ...
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Measurement of Isolation in a Directional Coupler
I want to measure the isolation of the following directional coupler (for more details of that specific component, go here).
Isolation can be evaluated through the scattering parameter S21, but how ...
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Importance of EM to microwave design?
I am curious, how important is a general understanding of electromagnetics to microwave circuit design?
I have looked at Pozars book which provides some background on EM and transmission lines in the ...
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Example of computation of S matrix
Let's consider the slide 1 of this material.
I have understood the computation of S11, but not that of S21.
I do not understand:
- why there is the circuit with V and two impedances Z0 and there is ...
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Measurement of Resistor Parasitics Inductance and Capacitance
I have seen people doing some measurements of parasitic capacitance and inductance of some resistors, by using a vector analyzer and analyzing the graph of S11 with respect to frequency.
To get this ...
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Computation of the Scattering Matrix of a Transmission Line
let's consider this transmission line (with losses) in which a and b denote respectively the reflected and the incident waves at each port:
This exercise asks to find its scattering parameters ...
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