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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20 views

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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Water-Cement ratio measurement using microwaves [closed]

I would like to evaluate contact-less water-cement mix ratio measurement using microwaves. Already approached this topic with capacitance measurement but the resolution was too low. The difference ...
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80 views

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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37 views

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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Transient Simulation Wilkinson Power Divider

In ADS, I am trying to simulate Wilkinson power divider with Transient analysis option using microstrip lines. However, I am unable to see the effect of 3 db power dividing. That is, at the output, ...
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1answer
44 views

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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1answer
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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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Radio frequency coil for homogeneous B field over area

Are there any possibilities of creating a coil which would function at high frequency (MHz range , maybe up to a few GHz) and which would give me a B field that could be used to penetrate a certain ...
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54 views

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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2answers
61 views

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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3answers
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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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1answer
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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 electromagnetic ...
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1answer
154 views

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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101 views

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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1answer
64 views

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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31 views

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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2answers
61 views

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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1answer
33 views

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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In a microwave waveguide isolator / circulator, what is this thing?

In this isolator picture, in the background we see load - and black water pipe for cooling, in the front there are two white vertical rectangles through which the cooling pipe goes. What are they? Is ...
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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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What is the Intuition behind the Stability Factor (K) in Microwave Amplifiers?

In microwave amplifier design, there is a Rollett's stability factor (included below), which determines if the amplifier can be unstable. If K > 1, the amplifier is always stable, and if not, it could ...
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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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2answers
59 views

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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1answer
28 views

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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1answer
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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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1answer
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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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1answer
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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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3answers
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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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1answer
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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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1answer
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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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“Trace Max Hold” function in spectrum analyzer

I have seen my professor doing a measurement with the spectrum analyzer in which he wanted to evaluate the frequency response of a bandpass filter. He used a signal generator in sweep mode from 1MHz ...
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1answer
37 views

Orientation of Loop Antenna (receiving mode)

I have done some measurements through a loop antenna similar to that shown in the following picture (all the informations included do not refer to my antenna, it is a picture used only to show its ...
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4answers
96 views

Voltage on a Transmission Line with Ideal Conductors

Let's consider a transmission line with Perfect Electric Conductors. We know that if an external AC source is applied, we get a voltage waveform between the conductors which is function of the ...
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Evaluation of Dominant Mode in a Circular Waveguide

I was doing the analysis of a circular waveguide (precisely, a wave guide with half - circular section of radius a, as shown in the following picture, and in which the shell is a Perfect Electric ...
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34 views

TEM Propagation in Infinite Ferrit Medium

I have realised a question on Collin's Foundations of Microwave Engineering book which is related to TEM propagation in infinite ferrit medium. I could not find a way to establish to relate positive ...
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1answer
37 views

Transmission Line with Short Circuit and Inductor as Loads

let's consider this situation in which the two ports of a transmission line are connected to a short circuit and to an inductor: The transmission line is supposed to be lossless. My book makes a ...
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1answer
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Scattering Matrix with Power Waves and Voltage Waves

I read that for a given N-port network there are two different conventions about defining the incident and reflected waves. This is the first convention: This is the second convention (we see that ...
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One Port Microwave Active Network Electrical Model

let's consider an active one port network: My book does an analysis of it by considering the Poynting Theorem, in which we consider the contributions of active sources (electric and magnetic current ...

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