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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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Struggling with patch gps smd antennas connections

I'm struggling with antenna connections to GPS module in my PCB design. My antenna is a smd passive patch antenna, "SGGP.25.4.A.02 from Taoglas". The antenna shape and recommended footprint is in the ...
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57 views

High data rate (~1-5 Mpbs) Point to Point Radio

I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional ...
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2answers
53 views

does adding Vias through the antenna feed line change impedance?

I have a GPS through-hole patch antenna, the through hole need to be connected to the bottom layer and then from there the feed-line flows to the GPS receiver. But I want the GPS receiver to be on top ...
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54 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
86 views

How to increase range of AM radio waves? [closed]

As a personal project, I made a very simple AM transmitter with an idea from an online tutorial, using a 1 MHz crystal oscillator (plus power source, antenna, breadboard, etc.). However, when using ...
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80 views

Are headphones with EMF measurement of 10,000 milligauss harmful to me?

I used a EMF detector app on my phone and measured the EMF output on my wired headphones. It measured around 10,000 milligauss on one part of both ear cups. Since wearing these headphones on my head ...
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56 views

Discrepancy between simulation and measurement for a voltage doubler/ rectifier design at 5.8 GHz

I am designing a pretty straight-forward voltage doubler at 5.8 GHz with MACOM's MA4E1317 diode, which I have used before and know from previous experience that matches pretty well with the spice ...
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1answer
112 views

Impedance matching for push-pull RF amplifier

I am working on the output matching network of a commercial push-pull class AB amplifier based on LDMOS BLF188. The output matching network consists of a 1:4 transformer and a Toroid with 8 turns The ...
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2answers
57 views

Noise power at receive antenna with finite transmit SNR?

I have seen a few examples of link budgets, and they all assume that the total noise at the Rx is just going to be -174 dBm + 10 log BW. However, this seems to me to assume that the transmit signal is ...
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1answer
110 views

A beginner that could use a few tips on wiring my first circuit involving relays

I am in no way experienced or knowledgeable with circuits or electronics passed installing my own car subwoofers and amps, or swapping out pickups on a guitar which means I only basically know how to ...
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190 views

Explain this circuit

I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand the calculation behind it, and the reason for emitter inductor, 3.9k collector ...
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66 views

Impedance matching of a RF power amplifier based on the s2p file

I'm designing the input/output impedance matching circuit for a RF power amplifier, based on the vendor supplied s2p file. I designed separately the input/output matching circuit at the given working ...
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52 views

XBee Pro Antenna Options - do the U.FL antennas have better range than the chip or micro pad antennas?

Logically the U.FL dipole antenna will have better range than the other two options, as it's a larger antenna, but is this actually true? How do the three antennas perform in relation to each other ...
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2answers
61 views

Question about the power rating of a RF power amplifier

In HMC453ST89's datasheet, it gives the electrical specifications when Vs = +5V: The max. output power is around 32.5dBm, about 1.6W. But for a 50 Ohm load, 1.6W means the peak voltage is about 12V. ...
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1answer
65 views

How close to P1dB can I go?

I'm trying to decide on a safe input power to a power amplifier. The amplifier in question is SE5004L. The datasheet specifies that the amplifier output 1-dB compression point has a minimum value of ...
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2answers
129 views

Can somebody please explain the antenna and mixer stage of this AM superheterodyne receiver?

This is from an Elenco AM/FM superheterodyne radio receiver kit. The shown area is the AM antenna and mixer stage. The wire leading from the top right corner is Vcc. Q7 simultaneously oscillates ...
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2answers
83 views

Project - How to onstruct a circuit to introduce and control a 0-300ms delay in an RF feed from a Sky Box to multiple TV sets? [closed]

Just bought a new TV! It's "smart" but where my previous dumb TV didn't, my smart TV introduces a delay over HDMI from my Sky+HD box compared to the RF2 output which is wired via coax cable to the ...
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How do microstrips actually represent lumped components?

I'm having trouble understand intutively how microstrips repersent lumped element components. All we are told is that, high impedance sections on a microstrip line repersent inductors and low-...
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1answer
35 views

How to stop erroneous signals on startup of an RF circuit

I have a really janky setup where I'm using an ESP and some transistors to "push" the buttons on an RF remote control, used for controlling electrical outlets. The circuit works perfectly during ...
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56 views

Creating a balanced dipole from two monopole chip antennas for use on small PCBs

I'm trying to use a monopole chip antenna on a PCB much smaller than the one recommended in the datasheet. I am wondering if I can get away with a much smaller board by using two monopole antennas ...
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2answers
76 views

I don't know how to choose an adequate antenna

I need to choose an antenna for a long range free space communication (~10km), and I currently have a receiving antenna, but I don't understand enough to be able to pick an adequate emitter. The ...
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1answer
54 views

Equivalent Series Resistance of 13.56 MHz RFID Antenna

I am designing a system that uses the MFRC522 by NXP Semiconductors and I am having a bit of difficulty designing the antenna. NXP provide an antenna design guide under the application note AN1445 ...
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1answer
115 views

How to design RF PCB to ensure the 50 ohm impedance

I do not have any experience designing RF circuits and I am finding many challenges for my project. One of them is to match the 50 ohm impedance that some components demand. In the input of my PCB I ...
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1answer
53 views

My mobile detector circuit won't work

I'm trying to get C3 to detect RF signals from a mobile phone. Amplify this signal to detect it using an LED. My main issue is simulating the antenna on multisim since multisim doesnt have an antenna!...
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1answer
82 views

Generating a realistic sine wave in MATLAB

I'm working on a simulation on MATLAB and I need a realistic sine wave which has harmonics. So I know there would be harmonics at 2f,3f... but I am not sure how to determine their amplitude. I tried ...
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97 views

How to find new ABCD parameters when reversing 2-port network

I have an ABCD matrix represenataion which is defined as: For such a problem, what approach should I follow in order to organize the new ( reversed) network ports voltages and currents properly. I ...
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37 views

Propagation Constant in Transmission Line - Approximation

This is more of a math question but I feel like the maths.stackexchange people won't like these approximations hence I'll stick here. I'm trying substitute in the conditions for a low-loss ...
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1answer
33 views

How could i calculate the voltage induced in a detector circuit by picking up RF signals from a Mobile phone?

Is there any formula/equation i could use to estimate the voltage induced at the input from the RF signals?
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38 views

Near-me area network embedded emitters with a Raspberry Pi server receiver

I am making a toy for 4-year old children with 10-20 pieces in wood, as in this picture with four wooden boards with names: The goal is that each wooden board triggers a sound, such as "Hello" or "...
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1answer
69 views

Easiest way to find transfer function of a lossless ladder filter after we finish design?

I have completed my Lossless Ladder BPF design, but I don't know how to find the transfer function of the resulting circuit without going through the slow and rigorous process of getting resistances ...
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2answers
47 views

Impedance control for small antenna feed?

I have a BLE board with a 1/4 wavelength antenna and a feed that is about 12mm long. The wavelength of 2.45ghz is 122mm. I've seen various discussions saying anything over 1/10 the wavelength you ...
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91 views

RF switch acting like a splitter

I'm trying to use a pair of RF switches (SKY13421-486LF) to switch two channels between the circuit output and a matching resistor: I have two inputs and want to pass one to the output and dump the ...
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1answer
122 views

RF Splitter/Combiner with vectors in phase and antiphase - Where does the power go if they cancel?

Updated I have a RF splitter/combiner. I am focusing on the black and red vectors. (Picture attached) When the black vector of 0.25V and 0 phase enters the box, it will split. 1/sqrt(2)*0.25V at 0 ...
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1answer
43 views

Matching Networks on Narrowband Multistage Low Noise Amplifier (LNA)

How does the inter-stage matching network of a narrowband LNA compare to that of a wideband LNA for the same multistage design? I've read somewhere that narrowband LNA does not necessarily require a ...
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3answers
130 views

Why does antenna tuner in crystal radio use capacitor and an inductor?

I know that antennas can be capacitive or inductive depending on the relation of antenna length to the \$\lambda\$. I know that crystal radios use both antenna and capacitor for tuning and I don't ...
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2answers
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Why are so many RF remote boards relay-based?

I'm working on a device that illuminates a signal LED when a button on a remote is pressed. I have a working prototype based on a pre-fabricated board I bought on Amazon (see here), and it's nice! But ...
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1answer
105 views

RF Development board layout questions

I was looking at the development board layout for the MMZ09312B and I had a few questions: datasheet: http://cache.freescale.com/files/rf_if/doc/data_sheet/MMZ09312B.pdf Are large polygon pours away ...
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2answers
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RF Antenna design for 2 different operating frequencies

I have noticed that my mobile phone sometimes shows it is using the 3G and then other times the 4G. How is that possible if they are using the same antenna? I assume it would use a microcontroller ...
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1answer
50 views

RF measurement setup

I'm trying to take a simple measurement of ~2.4 GHz (WiFi land) with an RF spectrum analyzer (Tektronix RSA607A) but have so far been unsuccessful. On the RF In ...
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3answers
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bike won't start until rider wear helmet [closed]

I am trying to make a project in which ignition system of bike will not start until the rider would wear a helmet. This can be done through RF Transmitter and receiver, but how it will be achieved? ...
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1answer
87 views

Connection between RF output to the source for minimum loss and maximum power transfer

The bottom device in the left image is an RF generator with ratings 230V, 15A (max), 13.56 MHz and variable controllable output power up to 1250 W. The top device is an auto match. The metal strip ...
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1answer
66 views

Commercial broadband RF amplifiers

In the process of designing a broadband RF amplifier, I've come across some commercial boards, claiming gain flatnesses of +-1db from DC to 1Ghz. Those boards are ridiculously simple, having only one ...
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19 views

Determing proper wireless parameters for HMTRP radio module

I'm trying to properly setup an HM-TRP FSK radio module to send and receive data the best it can at 56kbps. I think I'm wrong with setting it up to use 600Khz "receive bandwidth" and 160Khz "modulate ...
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1answer
38 views

Trying to read the data from an ASK RF transmitter

I'm trying to duplicate the operation of a simple RF remote control (for some remote power outlets). In the remote control there is an unmarked 8-pin microcontroller. I've worked out which pins are ...
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2answers
43 views

What is a tone (in context of IMD)?

I've seen the term "tone" used a lot in RF literature, but haven't found any helpful explanation of what exactly a tone is. I am looking at tone in context of IMD; i.e. the fundamental input tones. ...
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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
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Question related to the interference seen at the spectrum analyzer's receiver

I am preparing for the RF course exam. I have an old question on hand that I am trying to solve. Please review my attempt. Question: A simple spectrum analyzer with superheterodyne receiver ...
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Electro magnetic interference with Arduino Uno and a portable radio

I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise ...
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4answers
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Why are there so many vias on this board?

I was looking at the MMZ09312BT1 development board layout, and I was curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as ...
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1answer
42 views

Receiver Antenna Gain

How is gain defined for a receiver antenna? If we look at a radiating antenna, there is a Pin, and the gain in a particular direction would be the radiation intensity Ur, divided by the radiation ...