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.

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86 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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175 views

Looking for criticisms for a VNA-like meter I am designing

I would like some help from anyone who could let me know any flaws or improvements in my design they can find and help me reconsider any last minute design fixes before I send my new project off to be ...
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58 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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104 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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1answer
678 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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1answer
151 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
147 views

Help with 144Mhz small signal amplifier not amplifying

I attempted to build a single transistor amplifier to try and increase the voltage signal coming from a Si5351 module, set to 144 Megahertz. My primary goal is to increase the voltage about 3 to 4 ...
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143 views

Why DDR4 Specs recommend that Address, Control and Clock buses be referenced to VDD?

Micron's Technical Note TN-40-40: DDR4 Point-to-Point Design Guide, page 19, says (emphasis mine): Timing Budget Suggested practice is to look at the design from a timing budget standpoint to provide ...
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52 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 ...
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72 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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70 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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78 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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91 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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93 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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85 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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1answer
428 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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1answer
58 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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295 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 ...
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1answer
332 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. ...
3
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170 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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69 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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148 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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898 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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1answer
160 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, ...
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93 views

Anything obviously suboptimal about this design?

RF novice here, this is the first PCB I've designed and I'm just wondering if anyone more experienced than I (which is most people) sees anything glaringly wrong/bad/in need of improvement with this ...
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24 views

How to correctly document wireless network choice for a project?

Disclaimer: I have limited wireless knowledge at the moment, I'm currently following the Certified Wireless Network Administrator study guide. I'm working on an RC car and have the following network ...
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54 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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144 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 ...
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1answer
211 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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1answer
192 views

Gain of a Dual Gate MOSFET

simulate this circuit – Schematic created using CircuitLab This is the schematic of the circuit but tried to find the gain of this circuit, assuming 50 % of the Duty Cycle for the LO, and M2 ...
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36 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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91 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 ...
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54 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
280 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 ...
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1answer
184 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 ...
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1k 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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81 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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2answers
406 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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2k 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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228 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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2answers
563 views

RF amplifier not working

I designed an RF amplifier that should amplify signals in the FM band of 88 to 108MHz. The circuit is as shown below: The input to the circuit is connected to an USRP through an SMA cable. The output ...
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1answer
228 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 ...
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1answer
137 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 ...
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1answer
194 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
311 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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42 views

Is it possible that a 12V transformer is creating EM interference that's coupling onto a long antenna cable?

I have an Arduino Mega, Adafruit RFM96W 433MHz LoRa Transceiver Breakout and 2 Channel OptoCoupler Relay Module. https://www.adafruit.com/product/3073 https://www.amazon.co.uk/SUNFOUNDER-2-Channel-...
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48 views

Why is a low resolution ADC (e.g. 4-bits) a bad idea for a Zero-IF GPS/GNSS RF front-end?

This is another follow-up from this fascinating question (the other follow-up question is here) for the design of an RF front-end for a GPS/GNSS SDR receiver. In a comment to the accepted answer, it ...
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35 views

EMI Shielding on PCB

I'm thinking about replacing an 915MHz RF module on a PCB I designed with an equivalent circuit directly implemented on my PCB to overcome some supply chain issues. The module I'm replacing has an EMI ...
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66 views

Need help understanding RF radio parameters

I am experimenting with the SPSGRF-915 RF transceiver, particularly with the different center frequencies. My question mainly revolves around the situation where multiple devices can transmit at the ...
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64 views

Connect headset to radio

I would like to connect a headset to my radio (Cobra AM845.) The Cobra radio has a 2,5mm audio jack and the headset has a 3,5mm audio jack. I made a PCB to connect the together as: When I close ...

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