Questions tagged [high-frequency]
This tag marks questions related high frequency (radio) circuits.
2
votes
1answer
66 views
Change in duty cycle of a transistor (BJT)
simulate this circuit – Schematic created using CircuitLab
I have recently been working on a project in which my requirement is to transmit the data through a transistor, at a typical speed of ...
7
votes
1answer
86 views
High Frequency Characteristics of Solder-Filled Vias
If a via gets plugged with solder, does this destroy its ability to pass high frequency (RF noise) currents? Since there is no longer a surface along which the high frequency currents can travel due ...
0
votes
2answers
107 views
High pass filter for use in amplifier circuit
I've designed an amplifier for a small ac signal (amplitude of around 5mV, frequency 252kHz) with a BJT (2N2222.)
The BJT is set up in a common emitter amplifier configuration, with the biasing ...
4
votes
2answers
418 views
Question relative to pads for capacitors - high frequency
In the article
Compact sub nano second pulse generator using avalanche transistors, I read P. 874
Further, we used pads on a doublesided
0.062” FR-4 epoxy glass laminate pc-board for
...
4
votes
2answers
317 views
Calculating Wattage for Resistor in High Frequency Application?
I am making a MOSFET driving circuit.
Frequency : 400 kHz [50% duty cycle]
Gate voltage: 12 V
Total gate charge : 210 nC as per datasheet IRFP460
Rise time: 100 ns
[Q=I*t]
Current: 2.1 A
Gate ...
5
votes
2answers
413 views
How does one measure the Fourier components of a signal?
I attended a lecture on ground penetrating radar (GPR). I am used to reflection seismic where the incoming pressure amplitude is measured as a function of time.
In GPR, instead the Fourier components ...
0
votes
0answers
40 views
What kind of Modulation? Who transmits on 850 MHz (LTE-Uplink or GPRS?)?
Hey, I found an interesting Signal on 850MHz (in Germany). It is not symmetric and very strong (relative to many others due to bad antennas). On the right side the bandwith is permanently used, on the ...
0
votes
1answer
55 views
Can I bridge output IO's from an FPGA that is driving a clock source to drive longer tracks?
Scenario
I have a motherboard and a daughterboard that couple through two headers.
The motherboard has a 16x16 array of ultrasound speakers each with their own drivers, that works. I drive them ...
13
votes
4answers
1k views
Why isn't there a non-conducting core wire for high-frequency coil applications
Background
The commonly known skin effect formulas are derived and only apply to solid conductors. The commonly used "skin depth" only applies in these cases. It is for this reason that in some ...
0
votes
1answer
54 views
Can you make an electric gamma ray emmiter by adding up frequencies with freq. mixers up until you reach gamma ray herz quantities?
I just thought this up. Theoretically if you can add freq numbers you can get to large quantities like in a calculator, only this time mixing electric frequencies using amounts of circuitry right? Is ...
1
vote
1answer
83 views
Need a technique to rectify high voltage high frequency
I recently made a high frequency transformer which I will be using to drive a large spark gap tesla coil. I machined the bobbin at work from nylon and bought the 60x55x15 cores on Mouser to form a ...
1
vote
1answer
84 views
Switching high voltages with MOSFET at high frequencies
I need to rectify 220V 50Hz AC power to obtain 48V DC output voltage. Up to 40A current can be drawn from the DC side. 10% ripple is acceptable on the rectified voltage.
I am considering two ...
0
votes
0answers
69 views
Choosing an inductor for a bias T
I'm creating a Bias-T circuit for a certain application. When choosing my inductor to block my AC-signals I know for example the proper inductance to choose etc. However, what I am having trouble with ...
1
vote
1answer
47 views
Paralleling LVPECL outputs?
I have a pretty unusual application here, where I need to drive a fast differential signal fanning out into 8+ 100ohm transmission lines. The unusual part is this: the transmission lines must be ...
0
votes
2answers
51 views
Passive Elements At high Frequency [parasitic effects]
What would the magnitude Response curve for a Resistor, Inductor and Capacitor look like [with parasitic effects not ideal components] ? From what I have gathered they would look something along the ...
1
vote
1answer
107 views
What's the role of Ground Plane in high frequency boards?
Here is an image of an LNB circuit:
As you can see there is some Vias that is pointless for me(blue circles). Why didn't the designer connect these components to the ground line around the circuit ...
1
vote
1answer
74 views
What's this length-tunned shape in this circuit?
Here is an image of an LNB circuit:
Probably you heard something about length-tunned traces that they use in high-frequencies PCBs. There is something similar to the length-tunned traces in the PCB(...
7
votes
1answer
1k views
Does it matter what size of via you use in high frequency circuits?
Here is an image of an LNB and there is some different "Via"s in the PCB that I don't know Why do they use different size of Vias in such circuits. Why? Any reason?
I showed two Vias using two arrows ...
6
votes
2answers
518 views
What do these parts of this PCB do?
Here is an image of an LNB circuit:
There is some parts in this circuit that I cannot know what they are. Marked them using blue circles. What are these parts and what do they do?
They looks like ...
0
votes
3answers
130 views
What's this component and how could these screws affect it?
Today, I was seeing the circuit of an LNB deeply and a part of it catched my attention. Here is an image of the circuit:
And here is two images of the bottom and the two components that catched my ...
0
votes
2answers
271 views
How to determine the current rating of Litz wire winding at high frequency?
How can we determine the current rating of a litz wire winding at high frequency?
This is my try:
For example, if we use 660/38 litz at 85kHz, we can see the equivalent AWG is 10 (reference). Then, ...
1
vote
3answers
110 views
High voltage to low voltage in ps/nanosecond time (Zener/opamp?)
So I have a signal that goes from 0 to ~800volts in 30ns. I would like to use this signal to trigger a camera (input impedance of 50ohm) which takes a max of 10 volts and requires the rise time to be ...
4
votes
1answer
112 views
Maximum via frequency
I am designing a 18 layer, 2.5mm board using the material FR408HR and I am wondering about maximum via frequency, because I should use them for PCIe 2.0 (5 Gbps).
I have not found a specific ...
2
votes
0answers
66 views
High frequency switching applications
I was reading that for high frequency switching applications with
semiconductors, the ratio of the electron to hole mobility should be high.
Why is it so? Is it a necessary condition always? Or ...
26
votes
8answers
7k views
Why is 50 Ω often chosen as the input impedance of antennas, whereas the free space impedance is 377 Ω?
In order to efficiently deliver power to a different part of a circuit without reflection, the impedances of all circuit elements need to be matched. Free space can be regarded as a further element, ...
45
votes
13answers
10k views
Why do fundamental circuit laws break down at high frequency AC?
We're just starting the whole RF scene having dealt with DC and low frequency AC for all our previous courses.
I understand that at high frequency AC, fundamental circuit laws don't apply anymore ...
-3
votes
2answers
165 views
Is there any way to convert 50 Hz directly to 1 MHz? [closed]
I want to know whether there are any ways to convert 50 Hz AC to 1 MHz without Voltage Controlled Oscillators?
If I'm correct, all the normal circuits convert the AC to DC and then use it to ...
1
vote
3answers
439 views
Is it possible to measure frequency upto 500Mhz with 50Mhz oscilloscope?
Is there a way to measure higher frequency measurements with a 50 MHz oscilloscope (eg rigol ds1054z)? Perhaps some post processing of captured waveforms? Or with the help of some adapters?
I have a ...
1
vote
2answers
195 views
Design a tank circuit for class C power amplifier using ADS
I am trying to figure out the best values for the tank circuit values (L and C) in order to compare the amplifier's efficiency with the output power
I have chosen the tank value L1 and C7 to resonate ...
0
votes
1answer
62 views
Impedance Matching Network with tracks+connectors in between (practice)
I've been struggling on how to design (and develop in practice) an impedance matching network with some traces/tracks/paths (whatever you wanna call it) and some connectors in between. So here is the ...
1
vote
0answers
88 views
Resonant, autotuned nanopulser
My need is to build (or purchase, if existent) a nanopulser, but not an ordinary one: it has to have some specific characteristics.
The premise is:
I have a device which acts as a variable capacitor ...
0
votes
2answers
107 views
High current/high voltage/high frequency measurement
I have a circuit that I'm having trouble understanding. It measures the current flowing through a conductor. The measured load is 20-100 Amps, 9kHz-34kHz, and approx. 340 volts. The main conductor ...
3
votes
2answers
317 views
How to amplify a low Amplitude, High frequency signal from Ultrasonic Transducer?
I am working with some ultrasonic transducers, the receiver gets a signal of around 10 mVp-p at 125 kHz and for its purpose needs a gain of around 10.
So far have a simple inverting OP-Amp setup, ...
0
votes
1answer
108 views
EHF RF Transmitter and Receiver
We are working on a blood glucose meter that will measure BG readings through radio waves with a frequency between 60-70 GHz.
That range is necessary to allow penetration through the tissue and we ...
0
votes
1answer
108 views
Asynchronous SRAM routing crosstalk concerns
I'm routing a large BGA SRAM that is connected to a BGA FPGA, and there's about 40 signals altogether connecting the two. I'm using Henry Ott's recommended 8-layer stackup:
1 ________________Mounting ...
2
votes
1answer
107 views
High voltage high speed low current amplifier
I want to design an amplifier that can take an 8MHz signal (even square) with an amplitude of only a few volts (1-3V) and amplify it up to 160V but I only need it to deliver about 60mA. I also want to ...
5
votes
4answers
2k views
Is there a small (6-pin) DIP I can use to generate multi-MHz squarewave clocks with an external crystal?
I'm building a circuit that I'd like to run at 8 MHz to begin with, but I want to be able to try it out at 10, 12, 16, 20, and, maybe, 25 MHz. I know that many microcontrollers have the ability to ...
5
votes
2answers
799 views
Build a High-Voltage High-Frequency Power Supply
I need to build a HV HF power supply to ionize gas. The specifications are 12V input voltage and 10kV output voltage @ 13.56MHz. I know this is not an easy task at all, since in this frequency area, ...
22
votes
3answers
2k views
Why solder mask are not applied to RF PCBs
I've gone through some of the RF PCB designs. In which solder masking on the traces are not present. Like this one
Is there a specific reason or performance issue to remove that?
0
votes
0answers
35 views
determine the cutoff frequency of a nMOS in common gate with gate resistance
I have to determine the upper cutoff frequency of this circuit.
I absolutely mustn't use the laplace domain because it's too time consuming so not compatible with the time I have at the exam.
A rapid ...
0
votes
2answers
94 views
Sram circuit design recommendations
I'm trying to design a simple SRAM board (using a cypress Cy7c1011cv33) to connect to my lattice machox3 starter kit's pin connectors. But I have some design questions, after reading their "SRAM Board ...
1
vote
2answers
125 views
High Speed Signal on Large Circular Ring
It's frequently communicated that when working with signals in the Ghz range, routing is extremely important to signal integrity. Pretty much any inclusion of unnecessary stubs is out of the question, ...
0
votes
2answers
132 views
High frequency AM demodulation
I'm building an light communication device(pretty much lifi) using AM and am mostly done with every part except for demodulating the signal. The signal looks like with a 1.8432MHz carrier wave(serial ...
2
votes
2answers
57 views
Radars and high frequency relation
Whenever I seach for radar implementations, independently of application (weather, military, autonomous vehicles, speed limiters, etc) it always comes in many flavours: huge antennas, small antennas, ...
-1
votes
1answer
174 views
Common source amplifier, source degeneration and determining the cutoff frequency
I have a n-MOS transistor with the following biasing network:
I have to determine the cutoff frequency due to GS and GD capacitances
The method used by my book is to first redefine the ...
0
votes
1answer
65 views
Multi-fixed-station AM receiver
I'm in the pencil-and-paper stage of building a radio receiver that has the following characteristics:
AM shortwave/HF
three fixed frequencies - 3.33, 7.85 and 14.67 MHz
single upper sideband with ...
0
votes
1answer
44 views
Problem with calculating high frequency response of a CE amp
I have this amp:
The parameters of the transistor are hfe=120, Cje=40pF and Cjc=4pF. I am also told to assume Cpi = Cje = 40pF and Cmu = Cjc= 4 pF.
From that I should calculate fh and compare it ...
0
votes
0answers
2k views
Smallest circuit for Ultrasonic Mist Maker or humidifier
I am working on Ultrasonic Mist Maker or humidifier circuit, but does not found any good circuit.
As search on google that we have to make about frequency 1.6MHz to convert water into mist. using ...
4
votes
1answer
422 views
How come esp8266 is able to generate 2.4 GHz wifi signals
I am wondering how it is possible to generate 2.4 GHz, if its core clock frequency is much lower than GHz scale.
0
votes
0answers
30 views
NMOS varactor Simulation Help?
I am trying to simulate a pair of NMOS transistors as varactors (BSD connected). However, am not getting any resonance at the particular frequency of interest. When I am simulating it, it is giving a ...
