# 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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### How to prove the Maxwell's equations written using wave number vector? [closed]

I was studying the oblique incidence of a plane wave(EM wave) in a boundary and came across these forms of Maxwell's equations. First I tried to prove them by multiplying them(k×E or k×H) using their ...
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### How is the PASCO microwave receiver realized?

I took a physical lab course where I worked on the microwave PASCO set-up WA-9316. Having a little background on electronics, I wondered how their microwave receiver works and found a more or less ...
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### Why are microwaves unidirectional and radio waves omnidirectional?

I understand that any wave can be given direction using a setup like a phased array. As I read about the properties of EM waves, I find that microwaves are unidirectional in nature. What is it about ...
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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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1 vote
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### Clarification on I/Q Mixer output

I'm working on RF Receiver, it is required to use I/Q Mixer for IF downconversion. Specification as follows below ...
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### IQ mixer LSB and USB image rejection and conversion loss

I am trying to test the rejection and conversion loss of the HMC1056LP4BE IQ mixer. I set the LO to be +10dBm @8.5GHz, IF1: -10dBm @250MHz, IF2: -10dBm @250MHz. Here I am using 3 different ports of a ...
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### Magnetron as receiver

If a magnetron is heated, but no high voltage applied, and microwave power of matching frequency is externally applied to its "output", would that produce a voltage across the HV terminals? ...
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### Why 7 dB power increase after combining identical strength signals?

I have signals from two transmitters that are combined via a power combiner (link). Both signals are at 7 dBm when fed into the combiner on their own. When combining both, the meter either reads 7 dBm ...
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### The problem with sensitivity time controlled (STC) based on pin diode

I'm using sensitivity time controlled (STC) pin diodes of PN:MPP 4201A-206 for our applications. Our operating frequency from 1300 MHz to 1400 MHz. See the schematic diagram below. As device ...
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### Why does an isotropic antenna becomes anisotropic inside a phased array (mutual coupling neglected)?

in this paper the following statement is written: An area A is allotted to each element in the infinite array. This is the maximum area available to each element, and is usually greater than the ...
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### Why do we say that the load impedance must be equal to the characteristic impedance to have adaptation/maximum power transfer?

If impedance matching requires conjugate complex matching of the transmission line to the generator impedance (for optimal power transfer), why do we say that the load impedance must be equal to the ...
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### How to control the repetition rate/mode spacing of a mode-locked laser?

The YouTube video Fundamentals of Frequency Combs says that the repetition rate (mode spacing) of mode-locked lasers can be controlled by CW lasers or microwaves. It says you can take the output of ...
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### Keysight ADS User-Defined Models to AWR/Virtuoso

everyone! In ADS Keysight it is possible to create a model - the so-called User-Defined Model. This is C++ code that describes the Y-matrix of the component. Is there the same possibility in AWR ...
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### Measuring relative phase of two microwave signals at different frequencies

I would like to measure, and ultimately control, the relative phase (and amplitude, but that's easier) of two microwave signals, one at $f_0 \approx 1 \text{ GHz}$ and one at $f_n = n f_0$, where \...
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### Microwave Turntable Absorption

Do microwaves turntables absorb some microwave radiation when being used? I heard that they can act as a minimum load on the magnetron. If this is true, can I interchange microwave turntables? Edit: ...
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### 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....
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### Why do dielectric waveguides support hybrid modes and metallic waveguides do not?

Can anyone explain to me qualitatively why dielectric waveguides (core and infinite cladding) support hybrid modes (E_z and H_z components in the guided wave), while metallic waveguides cannot? I am ...
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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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### Trace capacitance vs telegraphers equation

I haven't taken a course on transmission lines or RF so bear with me. Using EM we can calculate the capacitance and inductance of traces. I'm somewhat confused on the value of this calculation, though,...
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### Why does the IF of an RF mixer not go down to DC?

Consider this mixer: “SMA Triple Balance Mixer RF/LO Freq. 6-18 GHz IF Freq. 2-8 GHz” If my RF is 18 GHz and my LO is 17 GHz then the IF should be 1 GHz. But the product somehow has a minimum of 2 GHz....
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### Problem with S parameter calculation

A load of 50Ω is connected in shunt in a 2-wire transmission line of Z0 = Ω 50 as shown in the figure. The 2-port scattering parameter matrix (S-matrix) of the shunt element is: Method 1 The line is ...
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### Input and output impedance matching for the HMC414 amplifier

I have a question about the impedance matching at the input and output of the HMC414 power amplifier. I don't know exactly where to put this matching, and I wouldn't want to make a mistake. The ...
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### What type of polarization does this wave have?

I just took a test today and one of the questions asked was to classify the polarization of a wave. The wave consisted of x/y components $$E = 3\cos(wt-kz) x + 4 \cos(wt-kz) y$$ I classified this as ...
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### Deriving S-Parameters for Hybrid 90° Coupler with Isolated and Delayed P Shorted from 90° Hybrid Coupler S-Param Matrix

I'm trying to derive the s-parameters for a 90 degree hybrid coupler using the s-parameter matrix that is known for a coupler of this type when the ports are configured correctly. In this situation, I'...
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### The field in a waveguide at exactly the cut-off frequency

Can anyone explain to me qualitatively, what kind of field exists inside a waveguide at EXACTLY the cut-off frequency? I would be grateful if an explanation was given about waveguides with metalic ...
1k 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 ...
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### Are microwave SPDT switches typically reciprocal?

This is something of a basic question, but don't want to assume prior to buying an expensive switch. Are microwave (think up to 20GHz) switches typically reciprocal? When reading specification sheets, ...
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### Decoding/Demodulating audio data in Patent US4877027A [closed]

I'm interested in decoding/demodulation audio/voice data sent using microwave pulses as described in this patent: US4877027A - Hearing system In the patent it's shown that voices or any other audio ...
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### How to power this RF microwave solid state switch

I have the following RF switch: After googling for several hours, I have found that it is a solid state switch, from DC to 26.5GHz. I've also been able to test that between the golden plated female ...
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1 vote
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### Design of feed gap of a dipole antenna

I am unsure of the formula used to calculate the feeding gap of a dipole antenna. When I go through some research papers, the formula given to calculate the feed gap of a dipole antenna is L/200. I ...
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1 vote
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### Are there non-unscrewable microwave oven bulbs? [closed]

I recently emptied a Samsung microwave oven of its components and came across the lightbulb, which appeared at first glance to be fitted in a diamond shaped holder. Though when I looked through the ...
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### Why can S21 be simply calculated as 2Vout/Vgen?

For one of the four S-parameters - the S21 - why is that S21 can be translated as 2Vout/Vgen? Is there a simple explanation for it?
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### How can I tell whether a waveguide supports hybrid modes or not?

When studying metallic waveguides, it was taken for granted that the TE and TM (and potentially TEM) formed a complete set, that is, any electromagnetic field in the waveguide could be written as a ...
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### Proof of voltage in lossless line

I'm currently a newbie in electronics engineering, and I want to prove the formula for a lossless Transmission lines, but I'm struggling with it. Assuming we know the formulas for U(z) = Ud0(exp(-γ*z)+...
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### Designing a pseudo-Doppler transmitter

I am thinking about creating a CW transmitter based on the pseudo-Doppler effect (educational purposes, nothing special in mind). For this purpose, $n$ antennas will be placed in a straight line, ...
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### Spurious resonance in microstrip transmission line

We were trying to study the broadband response of a microstrip line on a 1.5mm thick Rogers AD1000 substrate whose Dk=10.7 and loss tangent=0.0023 at 10 GHz. The trace width is 1.2 mm. The S21 is ...
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### Friis Transmission Equation for Wideband Transmission

it's known the following Friis transmission equation: $$P_{rx} = P_{tx} \cdot G_{tx}(f) \cdot G_{rx}(f) \cdot \left(\frac{c}{4 \pi R f}\right)^2$$ It's nice but, as far as I'm concerned, it works only ...
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1 vote
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### S Parameters Channel Modelling Time domain representation of insertion loss

Below is the insertion loss waveform obtained after S parameter of a channel.The waveform is in frequency domain. May I know what is the equivalent time domain waveform and how to obtain it from this ...
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### 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 ...
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### PCI wifi board (Ubuntu OS) to experiment with microwave signals

I would like to use a PCI WiFi board under Ubuntu OS to experiment with microwave signals. I would like to be able to access the board through the software driver and be able to turn on or turn off ...
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### Why are transmission lines and waveguides needed for high frequency?

At low frequency, we can just use a piece of wire to connect electrical components, but why are special transmission lines and waveguides needed for high frequency circuits? Also I am confused by the ...
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### Wire heating from microwave signal

How would one calculate the temperature change in a wire into which a microwave signal of a given frequency and power is applied?
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### Trace width at high frequency

What trace width and height is required for a 1 A current at 3 GHz? Can the cross section of the trace be smaller than in case of DC or low frequency currents because of the skin effect? Will the ...
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### Microwave signal / oscillating magnetic field

What is the most effective way of applying a homogeneous oscillating magnetic field at high frequency(3 GHz) to an area of about 5x5mm^2? Helmholtz Coils are not practical due to the high frequency ...
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### What resistor is needed to discharge a capacitor of about 3kV (inside a microwave)

I've already made a capacitor discharge tool for a 300V capacitor and works fine using the 2 resistors that were on the PCB with the capacitor. I need to upgrade this to discharge a microwave ...
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### B-field strength inside current loop antenna

I want to comprehend the design of a microwave antenna designed by Sasaki et al. (arXiv:1605.04627 [cond-mat.mes-hall]) As can be seen in Fig 2a the magnitude of B is strongest in the center of the ...
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### Homogeneous magnetic field inside aperture of PCB

I need to create a homogeneous magnetic field of a certain strength across a 10mm diameter opening of a PCB by using a current track on said PCB around the opening. The signal sent through the ...
1 vote
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### Coaxial Connector Termination

I am studying microwave engineering at university, but I never had a possibility to try to manufacture anything that I have been learned in my courses. So I have decided to try it by myself. I have ...