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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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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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385 views

How to analyze/decode a Manchester encoding?

I have a barcode scanner working on 433Mhz (FSK). Since this is relatively old product and the PC software is not working with Windows 10's and I can't use the SDK anymore. I therefore have decided to ...
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146 views

RF switch for multiple antennas

I'd like to design an rfid reader with 4 output antenna's ports. My rfid reader module maximum output power is 30 dBm. My target is for the maximum output power in the antenna ports, to be 30 dBm. If ...
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141 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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294 views

Advice on Coplanar Waveguide and Ground layout of Antenna

I've this antenna model AH316M245001-T. Datasheet: http://www.mouser.com/ds/2/396/chipantenna01_e-587795.pdf RF signal will be routed using CPW with ground vias. RF freq. is 2.4Ghz, 50ohm line. I ...
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66 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

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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49 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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60 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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68 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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135 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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279 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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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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125 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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857 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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182 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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91 views

First PCB project design critique requested (RF) EDITED

This is my first ever RF PCB project and it'd be great to receive some guidance to make this project 'first-time-right'. It's purpose is to transmit and receive signals at two different frequencies: ...
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20 views

Realizing a prototype filter in ADS or any other simulator

I'm trying to design a stub-filter, and I'm stuck on realizing the filter design using Richard's transformations and Kuroda identities. I'm building a 5th order Chebyshev LP-filter for 2.6 GHz pass-...
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103 views

On purpose shorted capacitor in schematic

I've come across this schematic from an RF device where I've spotted some weird configuration of capacitors. There are, all around the schematic, some shorted capacitors which I can't figure out what ...
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25 views

What causes the fail-safe bit to be set in the SBUS protocol?

What causes the fail-safe bit to be set in the SBUS protocol? I know that the when the link between the transmitter and receiver is lost, the fail-safe bit is set, however, what constitutes a 'lost ...
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83 views

Noise floor raising at high RF input power after filtering

I have a USRP b205mini with AD9364 transceiver. When it receives a very high RX input of about -5 dBm at different frequencies, not in the original RX range, the noise level raises slightly. The RX is ...
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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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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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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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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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57 views

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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29 views

2 tone test with RF mixer

I am designing a system that uses RF to probe the nonlinearity of a target. It works as follows. Transmitter sends out 2 RF frequencies, such as 900 and 910MHz. The target/reflector has a ...
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40 views

Generate ultrashort rise times with photoconductive switch or photodiode

I am trying to produce voltage pulses with very short rise time (<15 ps), medium width (20 ns) and amplitudes up to 15 V. As a promising candidate I selected photoconductive switches and ultrafast ...
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22 views

CST Studio Space State Matrices

I am new to using CST Studio and I am trying to figure out how to see the state space matrices (A,B,C,D) of a designed antenna to describe its radiation pattern in other software. Any help on the ...
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24 views

Load Impedance Derivation

I'm having some trouble deriving this equation for transmission line theory: From: http://www.antenna-theory.com/tutorial/txline/transmission3.php When I sub the Telegrapher's equations into eqn ...
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75 views

Amplitude Modulating a simple Laser using an RF transformer

I know I can modulate a laser using an audio transformer see pic and website below. Pen Laser website I was wondering if it’s possible to modulate a simple pen laser using RF signals in the RF range ...
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110 views

LoRa RX-Single Mode Inconsistent RX-Timeout Interrupts

I'm trying to implement LoRa communications using an SX1276 module (DRF1276G) and an ATmega328P on a custom PCB. I've got it mostly working but I'm having a strange issue with the timeout interrupt. I'...
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84 views

Reflection on a matched transmission line

A matched load with source using a transmission line (assume real load and matched using quarter wave transformer) should not have any reflection ideally. But we can see that the load impedance is ...
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45 views

Active phased antenna array for Wi-Fi efficiency compared to a directional antenna?

I'm interested in mesh networking of poorly controllable autonomous aerial vehicles (like blimps), so i wonder whether it is viable to use a phased antenna array versus a few traditional directional ...
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397 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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109 views

Help decoding line code

I have collected a burst signal from a radio device using an RTL-SDR and gnuradio and demodulated the FSK, but am having trouble deciphering what the line code is. Signal is at 151.3MHz Here is the ...
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120 views

LoRa radio transceiver for PtP mesh?

So after being informed on the Amateur Radio Exchange this isn't quite HAM/Amateur Radio, posting here. So I'm, well, very new to general RF/radio in general other than basic WiFi, but I'm looking at ...
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46 views

Interfacing LoRa SX1301 IC to third-party RF front-end

I am reading the datasheet of SX1301. I got struck at SX1301 RX operation using a third party RF front-end topic (Page 22). The page (22) says: In that mode the ...
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118 views

Self Resonant Frequency VS Package Size for capacitor

In general belief, smaller capacitors have better charactristic(more capacitive behaviour) in high frequency than bulky capacitors. On contrary in one of my RF project (8.5GHz - 9.5GHz) when checking ...
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61 views

How to go about decoding baseband from RF?

I'm designing the avionics portion of an ADS-B transponder and have everything done except the one thing I just can't figure out is decoding and encoding the baseband signal. I'm kind of under the gun ...
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424 views

FSK: Bit rate - Frequency deviation - Rx bandwidth relationships

I just started using a couple of low power radio modules in my project (HopeRF RFM69HCW). I made them work; they successfully transmit messages in a limited range (5-10 meters). Now I would like to ...
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88 views

Designing a 50 ohms castellated pad

we are designing a module in the 900MHz band which will have a RF output. We are using castellated pins to connect to another board. My question is: how can we make a 50 ohm pin output for the RF ...
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110 views

Development of proprietary WiFi protocol

I would like to do some customizations to IEEE 802.11 MAC layer protocol and implement it on hardware. I searched rigorously but I could not find any chipset with 802.11 PHY (RF + baseband chipset) ...
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2k views

What does the attenuation setting do in an RF spectrum analyzer?

I have to make measurements of the RF power which a circuit is delivering, and I am using an RF spectrum analyzer for that purpose. I am a beginner in this topic, so I apologize if the question is too ...
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40 views

What sets the MAG of a BJT?

Suppose you design ideal matching networks on the input and output of your transistor so ALL we're concerned with is the transistor and the packaging. What semiconductor physics or parasitics or ...
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66 views

closed loop zero in second order PLL with a proportional-integral filter

Why does the closed-loop zero in second-order PLL with a PI filter enhance the phase noise near PLL bandwidth frequency? I know that it enhances the phase margin but i can't find the logic behind why ...
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119 views

How to do fast RF on/off keying

I'd like to make a circuit that essentially produces very brief bursts of an RF signal, for example RF at 10MHz to 200-300MHz bursts of tens to hundreds of nanoseconds. For example this could be just ...
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112 views

Antenna gain, effective aperture and SNR

I'm trying to predict the SNR of different antenna. I have a good propagation model to calculate path loss/received power. My question is in the signal-to-noise ratio equation there are terms, Ae, for ...
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270 views

886MHz ETSI duty-cycle requirement

We are designing a 868MHz keyfob, which is transmitting in a band with a 1% duty-cycle limit. According to the ETSI EN 300 220-1 standard section 5.4, the duty-cycle should be measured for a period ...
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219 views

Diode ring mixer (difference between strong and weak LO)

I've built a simple diode ring mixer according to this video. The mixer works, checked it on several frequencies. The application of the mixer is to isolate the IF from a 27 MHz FSK signal. As my LO ...