Questions tagged [rf]

Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.

413 questions with no upvoted or accepted answers
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697 views

Design of cavity filter

I try to design a Chebyshev bandpass filter for 6 GHz as a coaxial cavity filter. I know that the filter can be designed with the aid of the coupling coefficients between the resonators and the loaded ...
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1answer
143 views

How do I calculate a PCB antenna trace width?

I'm totally stuck here trying to find a single source that describes how to determine a PCB antenna trace width. I understand how to determine the length based on the targeted wavelength, but the ...
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1answer
325 views

How can I reshape this PCB antenna so that I can still use it with the given circuit?

I'm borrowing the RF design from the MICRF114 Development Kit. Here's user guide- http://ww1.microchip.com/downloads/en/DeviceDoc/50002433A.pdf The circuit I'm using is on p. 35 and the antenna ...
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2answers
278 views

RF choke in Limiter Design

I am studying about limiter... (pic from Skyworks 200480C.pdf) In a limiter design, how should I design the RF choke inductor? If I need to design a limiter at 1-4 GHz and have a spiral inductor ...
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255 views

RF switch for multiple antennas

I'd like to design an RFID reader with 4 output antenna ports. My RFID reader's module maximum output power is 30 dBm. My target is for the maximum output power in the antenna ports to be 30 dBm. ...
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33 views

RFID reader array using row/column RF switches (multiplexers)

I need an 8x8 grid of RFID readers arranged on an 8"x8" board. The RFID tags will be placed only millimeters above each antenna. I was wondering if I could use one 1:8 RF switch (e.g. pSemi PE426482) ...
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54 views

Why circuit from antenna datasheet is like this?

I'm designing circuit with nRF52810 BLE SoC and I have decided to go with ceramic chip antenna because it seems easier than designing printed antenna. The problem is that I'm just a 1st year student ...
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65 views

Eliminate reflections on pulse signal transformer

I am trying to isolate an RLC ringdown signal via an RF signal transformer but I'm having trouble maintaining the signal integrity through the transformer. Below is the simple schematic describing my ...
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51 views

RFI protection for a stepper motor controller

I'm building a remote tuning device for a magnetic loop antenna. It will use a stepper motor to turn the shaft on the mag loop's variable capacitor. The electronics will consist primarily of a ...
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0answers
53 views

Microphonic SAW transmitter?

I built this very simple SAW transmitter, with a simple "spring" antenna for the right frequency. To test it, I tuned a portable receiver to around 433.92Mhz and fine tuned it until I heard silence. ...
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1answer
53 views

Gunn vs. VCO in terms of phase noise and THD

I am trying to compare the THD and noise phase of a Gunn oscillator and a VCO. I conducted an experiment where I measured both parameters for both devices and came up with the following results: (1) ...
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162 views

bearing ambiguity resolve (direction finding) for multiple sources

I am working on wideband direction finding algorithms for passive sensors. I started with Music algorithm. For practical reasons, the spacing can not be maintained lambda/2. For greater antenna ...
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30 views

Using a single MOSFET as an RF switch

I'm assembling a receiver kit from QRP labs. It is an inexpensive kit designed to cover HF. This kit has a BS170 at the input which I assume is intended to disconnect the receiver when the transmitter ...
2
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1answer
96 views

DRM'd hand sanitizer dispenser

We have a newborn and rely on hand sanitizer when changing diapers, and we ran out at an inopportune moment in history. By some stroke of luck, I managed to snag one of those "industrial" touchless ...
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49 views

RF signal Multiplier or Chopper

I'm trying to design a circuit that "multiplies" two signals. I have an electrical unit with two separate circuits. One circuit drives the other one with a square signal. The width of the square ...
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97 views

Why are tv aerial cables so mysteriously sensitive to their positioning and the proximity of people?

Digital TV Reception is not great in our area and sometimes we lose reception when conditions aren't favourable. Being UK Freeview, I'm pretty sure it uses the DVB-T2 standard. Anyway, when ...
2
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1answer
191 views

Thermal Noise in Oscillators

let's consider this circuital model for an LC oscillator in which the parasitic resistance R is affected by thermal noise (represented here with an equivalent noise current source, according to the ...
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60 views

Building a personal RF anechoic chamber in a large walk-in closet?

What would one need (besides many foam absorbers) to build an in-home small anechoic chamber for transmissions in the UHF to L-bands (specifically 500Mhz - 2 Ghz), and what resources would you point ...
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28 views

Parasitic Passbands in distributed filters

it is known that if we realize a filter (for instance a low pass filter) by using distributed elements (transmission lines), there will be some parasitic passbands (which moreover show a behaviour ...
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80 views

Does regularly spaced via stitching contribute to standing waves on an RF PCB?

Should vias be irregularly spaced? Can consistent spacing between ground vias create standing waves. Has anyone ever heard of this? I've been doing this for awhile and I've never heard this and ...
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82 views

High SNR FM demodulation

So I need to demodulate the FM signal from a sensor with highest SNR possible, at least 70-75 dB. IF is 10.7 MHz, max. deviation is 200 kHz but I can change those values if needed. Baseband signal ...
2
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72 views

2.4GHz RF design losing signal

First time poster here, please excuse holes in the plot. I have a simple wireless design made of an MCU (atmega328p) and an NRF24L01 module, powered through a 3.3V regulator, talking to a similar ...
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53 views

Question related to two closely separated signals that need to be analyzed by a spectrum analyzer

Question The settings of a spectrum analyzer are given as following: Center Frequency = 1.89 GHz, RBW = 10 kHz, VBW = 10 kHz and Span = 50MHz. The Reference Level is set to -20 dBm and ...
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1answer
195 views

Alternative wireless technology for passive RFID tags

I am working on a project where I have 3 boxes and a RFID reader (mfrc522) attached at the bottom of each box. I keep my wallet/keys/etc in these boxes and a LCD screen displays what is in each box ...
2
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1answer
139 views

Power amplifier simulation and real time experiment mismatch problem

Thanks in advance to anyone who will take the time to read my first post here. At present, I am doing a simulation of a power amplifier in LTSPice. The schematic and relevant files are uploaded in a ...
2
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1answer
191 views

BLE and Bluetooth Classic Coexistence?

we are designing a fairly compact PCB for a communications device. We are looking at using BLE as a link for voice to a separate microphone, and BT Classic to be paired with a smartphone. We are using ...
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0answers
91 views

Beam Steering range of a phased array antenna system

What is the beam steering range of a phased array dependent on? For example, if I use an antenna array of Nx1, with a phase shifter resolution of \$\frac{2\pi}{k}\$ and the antenna elements spaced at \...
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990 views

Spectrum Analyzer vs. RF Power Meter?

I own several spectrum analyzers and build various RF boards at all kinds of frequencies. I was looking over a BLE FCC test report for emissions, and I saw this lab uses a RF power meter to measure ...
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2answers
602 views

Impedance Matching: Minimum Reflection vs Maximum Power Transfer

The minimum reflection is achieved when the two "circuits" being connected have the same impedance. This makes sense because all the components of the wave can propagate without needing to be modified....
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1answer
491 views

Qucs model for 2.4 GHz matching circuit

I am designing a matching circuit for an EFR32BG13 SoC. The current board layout looks like this: In addition to the visible layers (top and bottom), layer 2 is a solid ground plane and layer 3 is a ...
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76 views

Transfer function of loop-back bias circuit for RF amplifier

I am trying to implement a current mirror as part of a bias circuit for a RF amplifier. I want to do a transfer function of the bias circuit since it creates a loop from the amplifier fet drain to ...
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0answers
323 views

Different balun configurations

I am looking for a balun to be used as a single-ended to differential converter, 1:2 impedance ratio, including range 1.5-2.5GHz, SMT and phase balance as good as possible (and return loss). Center ...
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287 views

Does anyone know what the heck this is?

I really hope I'm posting this in the right section. I was strolling down the street and looked up at this massive barrel object mounted to a utility pole. It's hard to tell from the pic, but it ...
2
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1answer
123 views

Sequencing modes for FCC “Intentional Radiator” test

I'm FCC certifying as an "intentional radiator" a product that uses a custom antenna and off the shelf Broadcom WiFi module. The module has an antenna port, so single-modular and limited single-...
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2answers
360 views

Discrete Distributed Amplifier

I read about distributed amplifiers. I know they are used in MMICs, but I wonder whether it would be possible to build a distributed amplifier with discrete components. In my opinion, it would have ...
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67 views

Is a board with on-board radio disabled an unintentional/intentional radiator?

If a board with the onboard radio (e.g., Bluetooth) chip disabled by software using a jumper, would it be considered to be an intentional or unintentional radiator? That is, the onboard radio can be ...
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1k views

How to find the resonant frequency of a human body?

I've read that the human body has resonant frequencies somewhere around 50MHz. I also think it would be interesting to look for values in other ranges like 10-100 kHz. I'm wondering how to build a ...
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134 views

High Frequency Ferrites for Transformers

There are many Ferrite material grades Available.The optimum frequencies start around 20KHz and extend well into the MHz range.There are also many core sizes to go from watts to Kw .Planar cores are ...
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0answers
886 views

Getting the best range with XBee-Pro 900 XSC S3B

I have a pair of 900 XSC S3B xbee pros and a couple 2dBi duck antennas. I just did a simple outdoor range testing and only got about 2,000 feet. I was outdoors without any buildings in the way, but ...
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206 views

Interpreting Data Sheets (“Typical Applications”)

I've recently been researching various transceivers, but I run into trouble as soon as I get to the "typical applications" section of the data sheet. With the Si4464 for instance, the example ...
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1answer
104 views

When are 1:1 baluns worth it?

I am trying to build an antenna to connect to the GOES-16 satellite (downlink at 1690,1MHz, linear polarization) with my SDR. My plans are using a 1m offset parabolic dish with a BiQuad feed, ...
2
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1answer
191 views

RF limiter for -20dbm

I am working on a receiver in which I would like to limit the RF power at input to -10dBm to -20dBm, the receiver is working for frequency 1GHz. I Have checked pin diode limiters and shottkey diode ...
2
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1answer
108 views

Does the feed line contribute to the function of a PCB patch antenna?

First let's make sure I've got my terminology right. The following are both 2.4GHz antenna: The first is a simple coaxial antenna that's just cut to the appropriate length for the relevant ...
2
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1answer
162 views

Resistive on-die termination

It is widely known that resistive termination (e.g. 50 Ohm to ground) is superior when noise is no concern. Specifically in the block diagrams of RFICs I see many 50 Ohm resistors to ground directly ...
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1answer
285 views

What is the End of Train Device RF Path?

A railway end of train (EOT) device is applied to the last car in a train consist. It communicates in the 450 MHz band with a head of train device in the lead locomotive. Modern trains can reach ...
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2answers
73 views

What is the purpose of this capacitor in the SA602A circuit and how do I choose its value?

I'm trying to use the SA602A mixer and I'm not sure what the capacitor between the emitter and the base does. I'm using this mixer because I've seen it being used in the Norcal40. However in the ...
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58 views

Detecting an electrical connection without a complete circuit

Wired Fencing In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive ...
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34 views

Calibrate for an inaccurate 50 ohm load in a DIY Vector Network Analyser (VNA) based on a VSWR RF bridge

I have built a "DIY VNA" using a frequency generator, an SDR receiver, a RF Reflection Bridge and a 50 ohm load. This is used to measure "VSWR values" of antennas to see what frequencies they are ...
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68 views

Making my own coaxial hardline

I need about 50mm of coax hardline. I don't have any at home, but I do have a lathe, some copper, and some teflon stock. Can I make my own coax hardline on the lathe? According to my calculations, ...
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41 views

Prevent Reception from an Extended Distance (Beyond Design)

I have a magnetic field that is being induced onto a power line by a transmitter, which is following the length of the power line to the receiver. The receiver communicates via a loosely coupled coil ...

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