Skip to main content

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.

Filter by
Sorted by
Tagged with
36 votes
5 answers
19k views

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?
Kamil's user avatar
  • 6,024
25 votes
9 answers
4k views

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 ...
Matthew Goulart's user avatar
19 votes
4 answers
17k views

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 ...
LUFER's user avatar
  • 371
16 votes
3 answers
4k views

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 ...
Vishwa Mithra Tatta's user avatar
16 votes
8 answers
41k views

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?
voices's user avatar
  • 1,089
14 votes
4 answers
39k views

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 ...
skillz21's user avatar
  • 506
13 votes
4 answers
6k views

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 ...
Joren Vaes's user avatar
  • 12.6k
13 votes
2 answers
380 views

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 ...
MikeTeX's user avatar
  • 1,898
11 votes
1 answer
4k views

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 ...
pazel1374's user avatar
  • 934
10 votes
2 answers
2k views

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 ...
Maximal Ideal's user avatar
10 votes
6 answers
3k views

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 ...
questioner's user avatar
9 votes
2 answers
4k views

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 ...
Sergei Gorbikov's user avatar
9 votes
2 answers
5k views

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 ...
Joshua Nozzi's user avatar
8 votes
3 answers
2k views

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 ...
Tommaso Bendinelli's user avatar
8 votes
2 answers
2k views

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 ...
hryghr's user avatar
  • 1,199
8 votes
3 answers
7k views

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 ...
user16871's user avatar
  • 237
8 votes
1 answer
538 views

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 ...
johnnymopo's user avatar
8 votes
1 answer
2k views

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 ...
James Last's user avatar
7 votes
2 answers
704 views

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{...
ashwmk's user avatar
  • 73
7 votes
4 answers
13k views

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)... ...
jdesbonnet's user avatar
7 votes
1 answer
6k views

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 ...
Alex I's user avatar
  • 3,491
7 votes
2 answers
1k views

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 ...
DakotaD's user avatar
  • 801
7 votes
3 answers
2k views

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 ...
Kinka-Byo's user avatar
  • 3,550
6 votes
3 answers
808 views

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:...
Yuri's user avatar
  • 118
6 votes
2 answers
508 views

Monopole antenna with coil design

(Note: I'm a beginner in antenna theory) When browsing for low cost antennas online, there seems to be class of monopole antennas that have a coil or two built into the monopole, and are advertised to ...
小太郎's user avatar
  • 223
6 votes
2 answers
9k views

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 ...
Kinka-Byo's user avatar
  • 3,550
6 votes
2 answers
8k views

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 ...
bytestorm's user avatar
  • 215
6 votes
2 answers
3k views

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 ...
S.s.'s user avatar
  • 2,780
6 votes
1 answer
107 views

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}\$)...
qtc0's user avatar
  • 107
5 votes
6 answers
2k views

Why do we need to use transmission line theory?

I just started to learn transmission line theory. I'm still confused about a lot of things. Every source says that we need to use transmission line theory when the length of the wire is 1/4 or longer ...
Analog's user avatar
  • 399
5 votes
3 answers
321 views

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. ...
Joren Vaes's user avatar
  • 12.6k
5 votes
1 answer
671 views

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 ...
DakotaD's user avatar
  • 801
5 votes
2 answers
814 views

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 ...
Prerna's user avatar
  • 171
5 votes
2 answers
585 views

Simple method to generate nonuniform magnetic radiation in a region of 0.5 mm?

I need an antenna that can generate a nonuniform magnetic field over a very tiny region at 5 GHz. (By nonuniform, I mean that the field vectors are diverging as much as possible. I will place this ...
Steven Sagona's user avatar
5 votes
2 answers
902 views

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 ...
pazel1374's user avatar
  • 934
5 votes
1 answer
5k views

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?
rishabh jain's user avatar
5 votes
1 answer
214 views

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, ...
dknapp's user avatar
  • 53
5 votes
1 answer
2k views

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) ...
Allan M's user avatar
  • 53
5 votes
5 answers
23k views

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 ...
Ishank's user avatar
  • 133
5 votes
3 answers
969 views

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 ...
C_Computing's user avatar
5 votes
2 answers
499 views

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 ...
Kamil's user avatar
  • 6,024
4 votes
2 answers
57k views

Microwave starts working when door opens - how dangerous is it?

I've just rented a house that came with an equipped kitchen, and I've found that the microwave has a rather weird behavior - opening the doors seems to trigger it to start working, which the owners ...
joaocandre's user avatar
4 votes
4 answers
1k views

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 ...
Kinka-Byo's user avatar
  • 3,550
4 votes
4 answers
586 views

Tapered line for a SP4T RF switch

I need to use HMC241AQS16 brand RF SP8T switch on an FR-4 board. The RF ports of this QSOP package integrated circuit have 50 ohms impedance. But there is a problem, the leads of the chip have just 0....
adba's user avatar
  • 311
4 votes
2 answers
199 views

How is the "open" component of the vector analyzer calibration kit made?

I've done some measures of S parameters with a VNA a long time ago. I'm not an expert om this, but I remember the procedure of calibration, which was using, for a single port, the three lumped ...
Kinka-Byo's user avatar
  • 3,550
4 votes
2 answers
241 views

Microwaves going through a hole - attenuation?

We have a microbalance that has a "hangdown wire" supporting a sample pan in a steel chamber. We need to heat this with microwaves, most probably at the common 2.4GHz of microwave ovens. ...
Dirk Bruere's user avatar
4 votes
2 answers
300 views

Can I test the EM shielding of a material with a spectrum analyzer?

I am a hobbyist and I am intersted in testing some materials for their ability of reflectance/absorbance/transmittance for microwave radiation and I want to know if a spectrum analyzer is suitable ...
Tintin's user avatar
  • 75
4 votes
2 answers
5k views

Which is the cause of "scan losses" in a linear phased antenna array?

in a linear phased array it is possible to move the peak angle ("beam steering") by applying proper phase shift between the excitation currents: The second picture represents the array ...
Kinka-Byo's user avatar
  • 3,550
4 votes
3 answers
892 views

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 (...
Mitu Raj's user avatar
  • 11k
4 votes
1 answer
155 views

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 ...
sharptooth's user avatar
  • 12.5k

1
2 3 4 5
11