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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What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave-length long?
What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave long? I have been told that this the the basis of what is known as a wave guide &...
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21 views
Deriving formula for microstrip filter performance
Is there a way to derive the formulas for common microstrip filter designs from EM?
I have seen tables for certain designs but I can't find any resource which derives them
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1answer
40 views
Limits on frequency generation using nonlinear device + resonator cavity
I recently saw a schematic of an RF device which supposedly could generate a ~1GHz sine waveform via a 50MHz square wave run through a diode and fed into a cavity resonator.
What I'm curious about is ...
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58 views
Will a vacuum tank shield against microwaves?
I am working on an experiment that involves 50-250W of microwave radiation. The antenna will be inside a small vacuum chamber (~2ft Dia x 3ft long) with ~1.5" steel walls. There are a handful ...
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1answer
81 views
How is the antenna return loss measurement impacted by the cable's return loss?
Say you have an antenna (2.4 GHz) for which you want to know the return loss using a VNA. The connection between your VNA port 1 and the antenna is through a coax cable (e.g., Murata). The cable's own ...
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4answers
90 views
How to Filter Harmonics in Wideband VCOs
I have a need for a RF signal generator, but I figured it would be a fun project to design a crude one myself. The main technical challenge I'm stuck on is how to filter out the harmonic content ...
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1answer
26 views
Coaxial cable test with VNA to estimate Wave Velocity and Attenuation
I'm doing a lab course concerning microwave measurements, during which I'm supposed to test an open, short and 50 Ohms terminated coaxial cable. The cable is connected to a VNA at the S_11 port and ...
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1answer
37 views
S-parameters vs device model
Many vendors provide both S-parameters and simulation models for their devices. Having encountered device models that when simulated, don't result in exactly the same S-parameters as the touchstone ...
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2answers
59 views
GND plane and reference potential
I have seen that most of RF printed board circuits have a GND plane which is connected to the power supply ground terminal and serves as a return path for current from different components on the ...
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4answers
853 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 ...
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2answers
30 views
power waves and scattering matrix
I have some doubts about the concept of power waves used in the description of the scattering matrix of an N-port component. In particular, I was wondering what is the most general and correct ...
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2answers
37 views
Amplitude plot of voltage standing wave on a transmission line
edit: I just found a site almost perfectly describe the issue, https://ophysics.com/w3.html
I found this graph on Google but couldn't find an explanation of it, it is similar to the one presented in ...
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5answers
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Material that doesn't let microwaves through, but is transparent to IR
Does a material exist that is transparent to infra-red light, but is opaque to microwaves (S-Band, about 2.5 GHz)? I am basically looking for a filter I can put in front of a infra-red sensor.
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3answers
52 views
How can I prevent microwave radiation absorption by a camera lens/electronics inside the microwave (behind the shield)?
Let's say I put in an endoscope like camera with the lens at the inside edge of the box and the wire behind metal sheet. Here's a mockup:
Possible idea: The lens is behind a holes but the hole is ...
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1answer
31 views
Evaluation of input and output impedance of a RF amplifier
I have a doubt about the meaning of input and output impedance of RF amplifiers. I'll take as example the amplifier CMA-252LN by Mini Circuits .
In its datasheet it is not clearly written their input ...
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23 views
Effect of feeder length in microstrip patch antenna
Summary of the question : Why reflection coefficent changes with microstrip feeder line length ?
Explanation of the question:
I'm working on re-simulating this paper : Microstrip Patch Antenna Array ...
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2answers
92 views
What kind of camera could work inside a microwave?
I want to record video inside a microwave, is it possible?
What if it was hid behind a shield or the same galvanized material as the door? The detailed structure may completely ruin visibility tho
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20 views
Effective Medium approximation of wet asphalt
So I'm trying to model the effects of wet and dry road surfaces for mm wave communication. My first attempt was to model the road as dry asphalt covered with a thin layer of water, but I'm not sure ...
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1answer
30 views
Friis transmission equation: how do I consider power loss along other directions?
I do not understand a basic concept about Friis transmision equation between two antennas:
where Dt and Dr are the antenna directivities (with respect to an isotropic radiator) of the transmitting ...
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1answer
33 views
Far field radiation and spherical waves
I have a basic doubt about electromagnetic waves emitted by a certain source.
Depending on the shape and on the physical properties of the antenna, its electromagnetic waves may have different ...
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2answers
53 views
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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2answers
120 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 ...
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2answers
57 views
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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2answers
26 views
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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2answers
83 views
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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3answers
44 views
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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29 views
Can a metallic rectangular waveguide support hybrid modes?
Studying the basics of guided waves in metallic rectangular waveguides, filled with homogenous dielectric material, I see that there is always a distinction between TE and TM modes. I understand that ...
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1answer
58 views
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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1answer
52 views
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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1answer
28 views
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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0answers
31 views
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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1answer
36 views
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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1answer
27 views
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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1answer
67 views
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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1answer
28 views
Trace width for breaking out 100Ī© 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 100Ī© Ā± 10% differential impedance, which I'...
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1answer
97 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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3answers
108 views
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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1answer
56 views
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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2answers
52 views
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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2answers
49 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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25 views
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
54 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
40 views
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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2answers
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 ...
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0answers
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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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4answers
4k 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 ...
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0answers
22 views
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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1answer
72 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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2answers
65 views
“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
120 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 ...
