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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Why do microwave ovens, with metal walls, not blow up?
Why does a microwave oven with metal (?) walls work fine, but if I (theoretically) put a metal spoon in it, "bad things" may happen?
Maybe these internal walls are not conductive?
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Is a microwave's output power proportional to the mass of its contents?
My friend and I are having a heated debate.
On the one hand, he thinks that a microwave oven that is empty, consumes almost no power (not considering lights, lcd, etc). He says that once you put an ...
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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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Why do microwave ovens use magnetrons?
With a lot of advancement in solid state electronics and signal manipulation, isn't it easier to simply take high amplitude signals with frequencies near 1 MHz and multiply the signals using diodes ...
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Are TV coaxial cables compatible with WiFi antennas?
If I replace an old, roof-mounted TV antenna with a 2.4GHz WiFi (IEEE 802.11) antenna; can I use the existing coax? Or will I need to run all new cable?
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How dangerous is a magnetron?
I took apart a microwave, and when I saw the magnetron, I conviniently remembered that I had heard that magnetrons were dangerous. I decided to research this a bit further (I know, great timing) and ...
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What causes loss of power over lifetime of a magnetron?
The power of a magnetron declines over time\$^1\$. While not noticable for most consumer applications (A 2000-hour lifetime would last over 20 years if the device is used only 15 minutes a day), this ...
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Big discrepancy between theoretical and actual power through my pulse generator
I am trying to acquire some skills about pulse generation, but that's not easy.
I've tried to derive the power dissipated by the input resistor in my pulse generator, but it turns out to be much ...
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90° Bend: Mitered vs Curved
On RF PCBs to bend a trace 90° you have many choices but among them Curved and Mitered bend considered as a good choice from performance POV (Both shown below).
For many years I thought that if you ...
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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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A few questions on PIRs and other motion detectors
I grew up incorrectly believing that motion detectors (as part of burglar alarm systems) were designed to detect movement, when in actual fact it is the movement of a heated (like body heat) object ...
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should I open a solder mask over a high speed microstrip line in a PCB?
Top layer of the PCB, 50 Ohm microstrip line transmitting 650 MHz/1.3 Gbps (corrected: 1.3 GHz) rectangular pulses.
To keep good signal integrity, should I remove a solder mask ink over the top of ...
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Can I improve the directivity of an X-band radar module with integrated plane-patch antenna?
Lots of detail provided in case it's needed.
I'm continuing to tinker with remote proximity sensors driven by an Arduino (and eventually just an ATMEGA* chip and its safety buddies) and have a pretty ...
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Radio frequencies, what are the limits?
What is the correct range of frequencies for radio waves? Wikipedia's article on radio waves states that all frequencies below 300 GHz are radio waves, while the article on the radio spectrum states ...
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Wavelengths blocked by a certain metal mesh
Introduction: I've heard about a theory, according to which you can check if there is any leakage in your microwave oven by putting your mobile phone inside and call it. However, I gave it a try and ...
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What are the bare minimum parts needed to operate a magnetron?
I recently took apart a microwave, and I managed to get a magnetron out of it, as well as a transformer that appears to be the power source for the magnetron, but looks a little small for the ...
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GaN pulsed operation
Does anybody have experience biasing and pulsing a microwave GaN HEMT? I've just ordered a 10 Watt S-band transistor. I know all about bias sequencing. This application is pulsed. I've read about ...
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Differences between a planar coil and coplanar waveguide to create a local 1D AC magnetic field
Coplanar waveguides (for example picture look here) are often used in research to create a local in-plane magnetic field. Now if compared to a planar microcoil like this,
driven by a AC voltage in ...
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Transmission lines with same impedance but different dimensions
Suppose we connect two transmission lines with characteristic impedances \$Z_1\$ and \$Z_2\$. The reflection coefficient looking into the transmission line with impedance \$Z_2\$ is
$$
\Gamma=\frac{...
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Help reverse engineering RCWL-0516 microwave proximity detector module
I got a cheap RCWL-0516 microwave doppler radar proximity sensor module to evaluate. The RF part of this has surprisingly few components (what looks like a MMBR941M NPN and a hand full of passives)... ...
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How strong is the electrical field inside a microwave oven?
I'm interested in figuring out the approximate peak electrical field strength inside a microwave oven. The question is not so much about the exact number, but rather what reasoning to use to work it ...
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Industry standard measure for coaxial cable stiffness?
Is there an industry standard measure for coaxial cable stiffness? By stiffness I mean the spring force experienced when bending or deforming the cable.
In my search for a highly flexible lab test ...
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What's the use of an impedance matching network when the transmission line has the same impedance of the antenna?
I'm designing a PCB including Quectel's BG77 LTE module.
In the application note I read:
The antenna ports have an impedance of 50 Ω.
Then this reference design is proposed for the antenna interface:...
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How Reflex Klystron works
I have a doubt on how exactly a reflex klystron works(as an RF source). In wikipedia it says that,
The electrons are fired into one end of the tube by an electron gun. After passing through the ...
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How to design wide band amplifiers?
I've been designing microwave power amplifiers and LNAs for school, I design in microstrip and my matching networks usually consist of stub/line sections or similar arrangements, I have also designed ...
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How to include magnetic loss in transmission line equations for coaxial cable?
I'm trying to calculate the attenuation per unit length (\$\alpha\$) of a coaxial cable, including dielectric dissipation (\$\varepsilon^{\prime\prime}\$), magnetic dissipation (\$\mu^{\prime\prime}\$)...
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Why does microwave test equipment use N connectors?
Almost all of the microwave test equipment I've ever seen and used has N connectors, with exception of some scopes that use either custom fancy BNCs (keysight does/used to do this)) or SMA.
...
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40 GHz spectrum analyzer with N-type coax input?
We have an old Rohde & Schwarz FSEK 30 that is advertised as having a range from 20 Hz to 40 GHz, with an N-type input connector. My conundrum is that a type-N connector with air dielectric ...
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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 simple meaning of TE10 waveguide [closed]
What does this numeral 10 represents and why do we have TE10 TE11 and then TE20. Where are the rest?
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What's inside this RF absorptive modulator?
I'm trying to understand how a vintage(?) HP 33000 series absorptive modulator works. Unfortunately, I don't have access to the detailed datasheets, so all I've been able to find is this document, ...
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Soldering RG-405 coaxial cable directly to PCB pads meant for U.FL connector
Is there an ideal method to solder a bare cable to a PCB for microwave (5-6GHz) signals?
The U.FL connectors that are normally used in this application are terrible, and there aren't many (or any) ...
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Why is it that a TEM mode propagates in a - Two separate conductor wave guide?
Please someone explain to me in Simple English or Basic equations as to why does a Transverse Electric and Magnetic Modes(TEM) propagate on only two surface Wave ...
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24GHz Radar : IF amplification and strange mixer output
I am currently working on a project where I have to study a microwave Doppler Radar.
Here are some details so that you can better understand it : a local oscillator (LO) at 24GHz is linked to an ...
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Why is a coaxial cable unbalanced?
Let's consider a coaxial cable which supplies a dipole antenna. My reference for all my statements is here.
My reference says:
Note that the current along a transmission line should be of equal ...
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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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GND pin of a RF device
I have a doubt about how to connect the following device (a RF power meter, AD8318) to the external circuitry. Let's consider the device:
There is the input RF coaxial cable, the power supply ...
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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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Vector Analyzer: what is IF bandwidth?
I noticed that if I set IF bandwidth low, the measures done with a vector analyzer are better (with higher SNR) but it is slower.
Precisely, what does it happen when I change it? Can you explain me ...
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Doubly terminated coaxial cable
I was going through the datasheet of ADV7125 DAC and found this sentence confusing.
For optimum performance, the analog outputs should each
have a source termination resistance to ground of 75 Ω (...
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Is it possible to redesign a portable electronic device such that it can be charged by a domestic microwave oven?
Soon after iPhone 6 was introduced there was a prank claiming that the smartphone can be charged by leaving it in a running domestic microwave.
TL;DR don't do it, it is very, very unsafe. There's a ...
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How to measure antenna S21?
Please explain in detail how to take an S21 measurement for an antenna? I know what it is... but how do I physically connect the antenna to the VNA to take the measurement? Thank you in advance!
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Strange shapes on the Wi-Fi module PCB
LG has this Wi-Fi module:
This is a 2X2 Dual Band AC Wi-Fi / BT module. You will see two folded WiFi antennas on upper side and one bluetooth PCB trace antenna at the lower right side.
I found this ...
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Is my VNA broken or miscalibrated, or are these weird results normal?
My company got a new vector network analyzer recently and I'm using it to try to learn more about microwave circuits, especially the resonant cavities that we use in our measurement systems. I've seen ...
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Effect of VIA fence on grounded coplanar waveguie (GCPW)
I'm working on a RF Frequency board with up to 6GHz signals. To connect components on the board (Mixer, Attenuator, ...) I decided on using GCPW. I designed my GCPW Using AppCad calculator (free ...
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Microwave Waveguide system tuning
I am going to built microwave system with following system configuration.
Power Circuit -> Magnetron -> Wave Guide Coupler -> Isolator -> 3 Stub Tuner -> Applicator.
Now, I want to make 3 Stub ...
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How do IMPATT and TRAPATT diodes work?
I was reading some text on microwave devices when i came across these devices.The explanation in the book was very convoluted and difficult to understand. Could some one please explain to me
Basic ...
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Building a personal RF anechoic chamber in a large walk-in closet?
What would one need (besides many foam absorbers) to build an in-home small anechoic chamber for transmissions in the UHF to L-bands (specifically 500Mhz - 2 Ghz), and what resources would you point ...
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Phase noise measurement with IQ mixer
I have a question regarding a measurement scheme of phase noise that I'm trying to implement. The idea is that I have two identical signal generators (I actually do) that generate a sinusoidal voltage ...
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Smith Chart Conjugate Matching
In an example in Pozar's Microwave Engineering, a conjugate matching circuit for maximum gain is designed using Smith chart. In the shown Smith chart, the matching circuit for input is designed. We ...
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