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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6answers
676 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 ...
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5answers
94 views

Can we use any electromagnetic wave (eg: radio wave, light waves etc) for cooking food?

A microwave oven cooks food using microwaves. The oscillating electric field in microwaves rotates the water molecules in our food. As all waves have oscillating electric fields, my question is why we ...
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0answers
20 views

How to design a complementary split ring resonator (CSRR)?

I've been looking for references that could help me to design a CSRR with no success. Basically, given a desired resonance frenquency, I want do design/calculate a CSRR that meet the needs ...
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0answers
44 views

What is the difference between a cavity resonator and a faraday cage?

In my internet research, I found that several people believed microwave ovens act as faraday cages and some said they act as cavity resonators.  I know that Faraday cages block incoming electric ...
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1answer
28 views

Power limiter purpose in a receiver

let's consider the following blocks diagram for a receiver of a pulse RADAR (but I suppose my question regards many kinds of receivers) My book says that T/R Lim means a power limiter which is ...
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2answers
45 views

MOT Power Increase

Your average mid level MOT can support around 1000 watts or 2000 volts at 0.5 amps. To quadruple the power of that, I need 4000 volts at 1 amp. Could you combine several MOTs or alter one's windings ...
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2answers
133 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 ...
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2answers
54 views

Waveguides and optical fibres

Why at microwave frequency we prefer rectangular waveguides while at optical frequency circular waveguides (i.e. optical fibres). Can we have rectangular optical fibres.
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1answer
57 views

2.4/5.8 GHz Microstrip Antenna Design

SE, I am trying to replicate the F-shape microstrip antenna design shown in: https://www.researchgate.net/publication/330747527_Dual-Band_Monopole_Antenna_for_RFID_Applications in Keysight's ADS, I ...
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1answer
52 views

Microwave detection circuit verification

I want to develop a circuit which can detect electromagnetic waves (radio wave, microwaves.) This circuit will just act as a tamper detect and not physically measure/compute the radiation. I have ...
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1answer
45 views

Stability of a RF Amplifier

In this article a RF Amplifier Design is proposed. It's written that (page 2): In an RF transmission network, if the reflection coefficient of a certain port is greater than 1, positive feedback will ...
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2answers
62 views

Is it possible to transform a microwave transformer into a current measuring transformer?

I have an old microwave transformer with only the primary coil and I'd like to know if I can modify it to transform it into a current measuring transformer.
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2answers
54 views

In an open-circuited transmission line (microwave circuits) the current in the return path is completely zero?

Since the current meets the open boundary and gets reflected back does this mean that the return path has zero current always on it? Or there is also a standing wave there as well with a current with ...
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4answers
77 views

Is the antenna gain time dependent?

Premise The antenna gain of a transmitting antenna relates its radiation intensity U(θ,ϕ) to its input power as shown in the following formula: $$G(θ,ϕ)=\frac{U(θ,ϕ)}{P_{IN}/4\pi}$$ Where the ...
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1answer
36 views

Correct calibration of reflection (S11) measurement

Following situation (apologies for my potential stupidity, I am very new to RF): I am doing a reflection/S11 measurement using a cut-off piece of coaxial cable (no stub, just a straight cut). The idea ...
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0answers
27 views

Single Section Branch Line Coupler at 73 GHz

SE, I am having trouble making sense of my simulation charts for a branch-line coupler tuned to 73.5 GHz. I followed Keysight's tutorial given by the link below. https://www.keysight.com/us/en/assets/...
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1answer
69 views

What causes the electromagnetic waves to prefer one dielectric over another?

it's known, and there are some devices that exploit this phenomenon (see the references if you want), that if an electromagnetic source (antenna) is placed between two different dielectric layers, the ...
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1answer
46 views

Printed dipole vs ordinary (3D) dipole

In order to make a comparison between an ordinary (3D) half - wavelength dipole and its printed (planar version), I've done a simulation in both cases. Both were designed to work at 3GHz (100mm ...
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1answer
55 views

Impedance matching of an amplifier circuit with a filter at the input and output

I created an amplifier circuit with a filter on the output. I did impedance matching on the input and then did matching on the output as well. From the graphs below, is the circuit more matched? ...
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0answers
40 views

Interpretation of the characteristics for amplifier circuits with and without a filter

I've run simulations in AWR software for hmc414 amplifier without and with filter on output. The conclusion after the first simulation is that this amplifier is unilateral. Unfortunately I don't know ...
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1answer
31 views

Avoiding thermal noise to enter low temperature while not using dissipative element

Let's assume that we want to interact with a circuit at very low temperature \$T2\$ to avoid any source of noise. The voltage interacting with this circuit must have a specific target value \$V0\$. ...
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2answers
46 views

Find the noise figure for a receiver front end [closed]

I'm editing this question as suggested in the comments. This is indeed a homework question for an old course that I'm reviewing, and the idea is not to solve it for me, but to show me how such ...
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0answers
38 views

Impedance matching - amplifier and surface acoustic wave (SAW) filter

How would I properly do impedance matching for the amplifier and saw filter at the output of the circuit?
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0answers
32 views

What happens if you connect a “slant 45 radio unit” to a linear parabolic antenna?

If I understand it correctly the only difference between linear polarization and slant polarization is that slant polarization is just a 45-degree rotated version of linear polarization, and that ...
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1answer
107 views

Why is a microstrip line unbalanced?

It is known that a coaxial cable needs a balun to provide an optimal supply of a dipole antenna, because of the common mode current that comes back to the transmitter through the external surface of ...
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1answer
28 views

Estimating Safe Pulsed RF Power given Continuous Wave Power Rating

For a university project I am designing a RADAR transmit/receive module at 9.4 GHz. Right now I'm working on an input power limiter to protect an LNA, but my colleague designing the LNA quotes its ...
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3answers
239 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 ...
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1answer
71 views

Why aren't magnetic substrates so used for RF printed circuits?

I've recently started working in microwave field, so I don't have big knowledge except for basic theory. What I've noticed is that, in rf and microwaves printed circuits (for instance for microstrip ...
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1answer
54 views

Reflection coefficient in a microwave amplifier

I have a question about the reflection coefficient in a microwave amplifier (two-port network), what is it and what is it based on?
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1answer
49 views

Scattering matrix in microwave amplifier

What exactly is the scattering matrix in a microwave amplifier. I tried to deduce from lectures what it is used for in a microwave amplifier, but all I found were the formulas corresponding to the ...
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1answer
102 views

What is the meaning of Directivity and Reflection coefficient for a RX antenna? [closed]

it's known that the circuital models of TX and RX antennas are the following ones: They are fine, but I find it hard to understand the meaning of some concepts when applied at the RX case. For ...
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0answers
68 views

Multiple Direct Digital Synthesizers (DDS) to Increase Sample Rate

I’m looking to generate a RF signal sampled at around 10 GSPS operating above the 3GHz mark. In order to maximize data throughput, the signal will be modulated at that frequency (rather than mixing in ...
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0answers
60 views

What is the purpose of a superstrate above a printed antenna?

I've seen that there are some planar antennas which are not simply a metal patch above a substrate, but present also a dielectric superstrate. Some examples of this configurations are: This planar ...
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0answers
40 views

Bode Fano criterium and low Q-factor

I am currently studying the Bode-Fano criterium and how it can be used to design wideband amplifiers. It's stated that a low load Q-factor (high resistive component with respect to the imaginary one) ...
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2answers
59 views

Are distributed element filters really distributed?

When looking at distributed filters etched into PCB, I have a hard time understanding why they called distributed. Most of them can be broken into sections and have basically a 1 to 1 correspondence ...
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0answers
37 views

Single balanced mixer, multi-tone analysis

I realized the circuit shown below on ADS. Schematic of the mixer can be shown below. As can be clearly seen from the figure below, to perform a multi-tone analysis RF signal is feeded with two ...
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1answer
92 views

Significance of the center-tapped transformers in mixer circuits

How does center-tapped transformer work on the circuit given below? In analog rectifier circuits, one of ports of the center-tapped transformer is connected to a sinusoidal source while others are ...
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3answers
81 views

How does a wifi antenna work?

let's consider a common wifi antenna (used in routers) like this: I don't understand some its basic features: 1) Is it a dipole or monopole antenna? I see only one conductor, so I'd say it's a ...
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2answers
317 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{...
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1answer
53 views

What is beam coupling coefficient for linear beam klystron?

What does beam coupling coefficient exactly tell? For eg. a voltage gain coefficient tells how much times the input was amplified. So what does beam coupling coefficient tell, like does it tell how ...
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2answers
47 views

How reflection occuring in antenna fed by transmission line affects performance?

Transmission line considered is lossless. Basically the configuration is simple. For transmitter side : a non ideal source (can be voltage current or power) feeding a transmission line (TL1) with ...
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1answer
102 views

Why aren't antennas placed at the ceiling of a microwave oven

From what I have understand, microwave ovens work by emitting microwave electromagnetic waves from some antenna. Please correct me if I'm wrong. In my microwave oven I have seen some empty holes at ...
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1answer
64 views

How can a resonator do band-pass filtering?

I've read many times some statements about resonators like this (reference): Resonant circuits are circuits, which offers a high impedance or low impedance (for parallel and series resonance ...
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1answer
54 views

Multiple Resonances along a transmission line

in "Lessons in Electric Circuits", VOL III, ChPT 14, all the possible configurations of standing wave for a certain transmission line are shown. For instance, this is the case of a ...
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2answers
101 views

Reference node in a transmission line

in "Lessons in Electric Circuits", VOL III, ChPT 14, there is a SPICE simulation of this transmission line: The author writes: Running this simulation and plotting the source impedance ...
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0answers
37 views

Why does the peak power change with the spectrum analyzer's span?

Consider a continuous wave signal being displayed on a spectrum analyzer at f=5GHz. It's a single peak. When I put marker on the peak it shows me the peak measured power. Now when I decrease the span ...
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0answers
29 views

How to find the distance between two arms of a hairpin resonator?

In this picture I want to find the value of W_cap(the distance between two arms of hairpin resonator). I have the length, width, quality factor and coupling co-efficient of the resonator.
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1answer
63 views

What is relation between power deposition and frequency?

1. What is relation between power deposition and frequency in electromagnetic waves? 2. Is it true that even very low power elec.mag.waves can be "dangerous" for long time health if ...
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1answer
44 views

I need help with hairpin filter design. Can anyone help me with the design steps and equations? [closed]

I have the coupled line design. But don't know how to convert it to a hairpin structure.
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1answer
54 views

Modelling a non-linear resistor on ADS

How can I model a non-linear resistor whose current changes according to the equation shown below on Advanced Design System (ADS) or AWR Microwave Office? $$i(t)=v-v^2-v^3$$ Where v is voltage ...

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