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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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52 views

Should the antenna be 'better' for the transmitter or receiver?

I intend for this to be a general/conceptual question that could apply to any wireless communication setup, however I will use a specific example to make things easier. For my example, I'll be ...
1
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2answers
47 views

Measure ~300kHz Induction Heater RF Power

I have been tasked to gather data from an old running 335kHz 5kW induction heater system. It has no outputs available to give amperage, power etc. Basically there is an assumption that the unit is not ...
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0answers
35 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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1answer
35 views

Un-masked Copper Boundary across RF section

I have seen so many PCB which has an un-masked (without solder mask), copper boundary across RF sections. The boundary has via-stitching and there are also few ...
0
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1answer
45 views

When deforming a resonant circuit into an antenna, why can we cut the inductor in half?

The working principle and fields of an antenna can often be shown by considering a parallel LC circuit. The plates can be moved to opposite ends and the inductor can be stretched out, both of which ...
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1answer
39 views

What is the relation between carrier signal and local oscillator in RF system?

I have a confusion between the carrier signal and the local oscillator and based on my understanding, IQ signal (data) is mixed with carrier signal to become a modulated RF signal and before ...
1
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0answers
18 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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0answers
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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1answer
52 views

How to determine operating frequency range of an unknown 2-port device (with VNA)? [closed]

I have a question on hand: "You have an unknown 2-port device, the black box. Find the operating frequency range. Show how to do this with a VNA. Think of the settings, why?" VNAs can have a very ...
4
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1answer
119 views

Effect of VIA fence on grounded coplanar waveguie (GCPW)

I'm working on a RF Frequency board with up to 6GHz signals. To connect components on the board (Mixer, Attenuator, ...) I decided on using GCPW. I designed my GCPW Using AppCad calculator (free ...
1
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1answer
65 views

How to use the UART functionality in this Bluetooth module?

I'm using a Bluetooth module called SPBTLE-1S whose datasheet is here - https://www.st.com/resource/en/datasheet/spbtle-1s.pdf In the datasheet, it says that I can use the UART functionality by ...
0
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1answer
25 views

SAW Filter input power restriction

I have front end module (915MHz freq band) in circuit Which is having 30dBm output power. Between This FEM and antenna I have to insert filtering circuit. I came across few SAW filters from Murata, ...
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0answers
191 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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1answer
50 views

Difference between hybrid and resistive RF power splitters, and Frequency Response?

I am new into RF measurements, and have got a couple of questions regarding power splitters (hopefully common for all the models that exist in the market). What's the difference between resistive and ...
1
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1answer
91 views

Impedance matching a capacitor load

I am currently trying to impedance match a capacitor as a load. In detail, it is an insulating thin film grown on top of a conductive layer (grounded). We now sputtered small Pt electrodes on top and ...
0
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2answers
162 views

Can I use more than one antenna with a radio module (say rfm69) and switch between those antennas electronically, say by a transistor

I need to know the approximate direction of the radio signal coming to my module, and I have to use very simple hardware and software for this. (Just a microcontroller and one module) What came up ...
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0answers
65 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 ...
5
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1answer
185 views

Routing large RF trace to small SMD pad

I am designing an RF board in Altium where due to the dielectric selected and its thickness, the trace width for a 50 ohm characteristic impedance is thicker than some of the SMD component pads. What ...
1
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1answer
34 views

How to calculated weighted gain of antenna?

I have this test specification for testing antennas and it defines weighted gain as follows: The weighted gain is calculated from the transfer function (S21) using only the gain values within the ...
2
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1answer
35 views

PIN diode in RF switching vs. PIN diode used as photodiode

From what I understand, there are traditional photodiode components that are designed with PIN diodes, in which the gate is activated by light saturation. For a PIN diode component made for RF ...
0
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2answers
26 views

RF connector/ interconnect for Gate signals

I need connector as shown in pictures. I spent good couple of hours trying to find them on Farnell but the lingo for such connectors is little difficult for me. I read a lot too but couldn't find ...
3
votes
1answer
90 views

Microstrip and CPWG transitions on PCB

I've been doing some simple RF boards as part of an internship in a lab, mainly to test particular ICs and prototyping, and mainly using coplanar waveguides. I've now been tasked with designing a ...
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2answers
57 views

rf amplifier saturation when input chirp

I am trying to generate an 11 MHz pulsed chirp signal with center frequency of 4 GHz at a power level of +10 dBm. I have an arbitrary waveform generator that can generate the correct chirp signal, but ...
0
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1answer
66 views

Through Hole (Vertically Mounted) SMA Connector on PCB - Feasible for GNSS Application?

Due to space constraints on a board I am designing, it is ideal to have the GNSS cable connecting vertically onto the top of the board. I haven't been able to find any edge-mounted connectors that go ...
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2answers
88 views

To see an encoded AM radio wave, what kind of Oscilloscope do I need?

I want to see an AM carrier wave and the resulting encoded frequency and the DC (I think) out of the wave, the information getting to my earpiece. What kind of Oscilloscope do I use for seeing the ...
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0answers
61 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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1answer
42 views

Type of RF Coil [closed]

I am trying to source parts for a project (Listed Below) and unsure what kind of RF Coil the blogger is mentioning. I am a novice and have managed to source most the other parts but this one component ...
0
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3answers
160 views

Can a USB Oscilloscope be used reliably and accurately for RF projects?

Are USB based oscilloscopes "sensitive" or able to be used with RF circuits? In particular, are they able to see the waveforms, carrier wave, etc. of something like a crystal set? I saw something ...
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1answer
140 views

Oscilloscope waveform shows overlapping levels, second harmonic?

What could be causing this 40 GHz signal to look like two overlapping waveforms on a 63 Ghz real time oscilloscope? On the scope I see the signal out of a 40 GHz signal generator outputting a CW sine ...
0
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1answer
69 views

Drone's Remote control not powering on! [closed]

I am using bayangtoys X16 GPS drone. I managed to solder the "alfa APA-M04 7 dBi gain RP-SMA directional panel antenna Wi-Fi" on the board, and it was working absolutely fine. Until, I put hot glue on ...
1
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3answers
126 views

Measure impedance of PCB antenna with very small ground plane

I have recently been designing different PCB antennas with very small ground planes due to design restrictions. I use a VNA to measure the impedances, but am having trouble measuring them correctly. ...
1
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1answer
33 views

Choosing between ipex connector and SMA Connector for LoRa, LTE and GPS

I have completed designing of PCB with LoRa (868 MHz), GPS and LTE (1800 MHz). Earlier version of my PCB had this SMA connector. But now the PCB will be placed in enclosure and I am thinking to ...
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1answer
110 views

What is needed link budget? [closed]

Assuming I want to send a signal 1 km away from a 2.4 GHz antenna with 5 DBI gain and recieving antenna of 2.15 DBI gain. What is the minimum needed power at the receiver (not the minimum transmitter ...
0
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3answers
137 views

Does a Crystal Radio coil require enameled wire or insulated turns?

When creating a coil for a Crystal Radio, why do I have to have insulated windings? Why does it matter if the individual turns touch each other? When it "shorts out" in this context, what does that ...
0
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5answers
298 views

Why are cell towers so high? [closed]

Why do cell towers need so much height? Does the height increase antenna gain because it may provide directionality?
0
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1answer
55 views

Single tone signal generation at microwave frequency with best phase noise and spurious performance

What is the best way to generate a single tone signal with best phase noise and spurious performance? Is frequency multiplication the best way? single stage multiplication or multi stage ...
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1answer
229 views

Why microwave links on cell towers have high frequency?

Why microwave links are in the higher microwave spectrum (I don't know exactly but I guess it's around 20-40GHz). If by Friis Equation higher frequencies have lower range then why use higher frequency ...
4
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1answer
159 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 ...
0
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1answer
53 views

How does adding more coils to an AM tuner coil allow it to tune Shortwave?

I have seen several tutorials about how to turn an AM radio into a Shortwave radio. They add more coils to the inductor (is that the correct name for the tuning coil?). Here is one example, https://...
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2answers
54 views

Direction Coupler

While testing a direction coupler (i am testing 30 dB DC ), I found that when I am giving signal at port 1 and output at port 2 (through port), it provides insertion loss and at coupled port its ...
1
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1answer
149 views

How can a phone transmit the signal back to tower? [closed]

If cellphones have such a low power transmitter (around 200mW for LTE) and also doesn't have directionality then how can they talk back to the tower even though they are so powerful and built ...
0
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2answers
60 views

How to derive voltage applied to an antenna, where transmitter power is known & identical tx/rx antennas are used with known gain/impedance?

Question: Imagine a transmitter + transmitter antenna with the following characteristics: 433Mhz transmitter transmitting 10dBm Into an impedance matched (50 ohms) antenna, omni-directional, 3dBi ...
11
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4answers
1k views

RF vs. audio of the same frequency

From an article by an engineer at Cisco Systems: An RF signal can have the same frequency as a sound wave, and most people can hear a 5 kHz audio tone. No one can hear a 5 kHz RF signal. Why not?
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1answer
139 views

Do the FCC's regulations make any sense?

I have read on the following page that the maximum permissible exposure MPE standard FCC have is 1 mW/cm2 for RF wave above 1500 MHz for general population. http://www.rfcafe.com/references/electrical/...
0
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1answer
127 views

What is this RF Frontend IC?

This is a picture of the PCB for a Tile Bluetooth tracker. I cant find any info on this chip, and I've looked for a while for the logo. here is a closer picture. The logo looks like three ticks, ...
5
votes
1answer
95 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
72 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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2answers
104 views

Why FM has larger range than cellular network [closed]

I can receive FM signal about 50km away from the transmitting station but I lose signal from cell towers in about few km (1-3km)
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0answers
153 views

Semtech LoRa sx1276 transceiver IC: modifying its reference matching network

After reading the following post: sx1276 Understanding matching network and having some followup questions, I wondered if I could just remove all the passives (optimizing PCB real state) and go from ...
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0answers
78 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 ...