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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50 views

What is counterpoise?

I was reading about the radio telescope - Murchison Widefield Array (MWA) situated in western Australia. Antennas of this telescope are quite unique and different from usual dish radio telescope. In ...
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My oscilloscope tells me I vibrate at 60Hz. How?

As I live in North America, my initial hypothesis is that I'm picking the 60Hz from my house's power line. But, to my understanding, my body can't be a 60Hz antenna (1/4 wave antenna length for 60Hz ...
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Wireless RF Serial Link 865-869MHz 2KM range (WIR-1186)

Wireless RF Serial Link 865-869MHz 2KM range (WIR-1186) is what I am using for my project's wireless meter reading. It works fine. My doubts are that the same module used for nearly for same purpose ...
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36 views

Use an RF transmitter to directly transmit Ultrasonic sensor data to the receiver [closed]

I want to connect a Ultrasonic sensor directly with a RF transmitter. Then receive this signal from RF reciver connected to an ES8266 micro controller. The receiving part is simple. But I am stuck at ...
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1answer
32 views

How to interpret the S-parameters of this result?

I'm designing an FSS in CST MWS that should be providing maximum reflection for the band (12 to 15)GHz and hence minimum transmission to this band. I've got the results has shown here. How do I find ...
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1answer
21 views

RFID Transponder transmission and reception working

I am reading about RFID systems and designs, and I stumbled upon this Digikey article. I am really confused with Figure 5 in that article. In the above IC diagram, I am really confused with pin 2, ...
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1answer
44 views

Oscillator drift on presence of hand

I am trying to use the oscillator described in "Experimental Methods In RF Design" book page 4.9 fig 4.13 C. I have attached a drawing here. Sorry for the bad drawing. The values inside the brackets ...
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1answer
41 views

Strange result when simulating RF low pass filter with Pspice

I'm trying to simulate a RF low pass filter in Pspice. The result don't match with my calculations and a filter simulator I found online. Does anyone know what I'm doing wrong in Pspice? My ...
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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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1answer
85 views
+50

How to calculate Doppler Shift for multipaths from moving objects?

Let's say we have a radar where the transmitter and receiver are placed together, and form an angle theta with a target object moving with velocity ...
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what would the world look like if we could see the lower frequency EM spectrum? [closed]

hypothetical question because curious: what would the world look like if we could see the lower frequency EM spectrum like radio and microwave radiation? Also are there any photos of the world and ...
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Is MIMO equivalent to link aggregation?

Is MIMO the wireless version of link aggregation in wired networks? I'm not asking if MIMO is a similar link aggregation protocol like LACP or PAgP. What I'm asking is, if it is the same concept as ...
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About cascode tuned circuits

In the following 2-stage cascode tuning amplifier, assuming that both tuned circuits have the same resonant frequency. Is the output voltage 90 degrees "delayed" with respect to the input (i.e. vo = -...
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1answer
65 views

SuperHeterodyne receiver

In a superheterodyne receiver, let us assume, I have a signal in the RF range of 88MHz to 108MHz. From what I have read, my understanding is that by tuning the local oscillator frequency, we can make ...
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1answer
48 views

Formula derivation of Doherty power amplifier from circuit diagram

I'm having a hard time understanding how formulas are derived from the diagram of a simple Doherty power amplifier circuit, as pictured below. While I understand the concept behind load modulation ...
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2answers
84 views

Is there a safe or better way of using an AAA battery in place of an AA battery in small electronic devices/ sensors, when in bind like pandemic?

Is there a safe or better way of using an AAA battery in place of an AA battery in small electronic devices/ sensors, when in bind like pandemic? For possible use in small electronic devices without ...
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1answer
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How does a micro interpret high freq rf signals from an antenna

If an antenna is receiving a frequency higher than the clock speed of the cpu, then how is the cpu able to interpret the data being received by its antenna?
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1answer
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In RF433 Mhz module What is the Bandwidth and Data rate that used to transfer data?

many of document I have read it that tell me this module has 2MHz and Data rate equal to 10Kbps and using ASK modulation how did it transfer 10Kbps on 2MHz what my question is why did used a large BW ...
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1answer
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Finding the correct capacitor for a 433MHz RF with HT12D

I have a 433MHz RF antenna connected to a HT12D. The transmitter is powered by a 9v battery with a HT12E. The receiver is powered by 5Vdc. I am trying to power the unit using a 12-0-12 center tap ...
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1answer
31 views

Band Switching Circuit

I am building an oscillator circuit at 4-6 GHz and I am trying to make a band switching circuit to add capacitors up to 10pF. Every band switching diode and low capacitance transistor I have tried ...
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0answers
42 views

Quadriga Open software [closed]

There is a driving course tutorial in Quadriga Software. I would like to use the same tutorial with amendments to simulate a scenario with a single transmitter and eight other receivers. The main ...
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1answer
24 views

How to use two antennas with a single Bluetooth module? (BLE repeater)

I am working on a project that uses small Bluetooth low energy (BLE) beacons to track important items. However, we have run into a situation where one location will store these items underground in a ...
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2answers
122 views

RF 50 ohm dummy load PCB design

I am a rookie on both RF and PCB design and I am currently trying to do a 50 ohm 11 watt dummy load project for 100MHz-1GHz. My calculations are done for the load but I have some questions about ...
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1answer
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How to do via fencing of an RF trace with a 5V front copper plane and a GND back copper plane?

Background I am a building a board to send RTTY via a Radiometrix NTX2B as part of my final year High Altitude Balloon (HAB) project. I have just created a PCB which I uploaded to JLCPCB for ...
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61 views

A switch without thershold voltatge

I'm working with in RF system with the same RF coil for transmitter and for receiver. I wait 100us microseconds while the coil is dischaged to change the transmitter mode to emitter mode. If I open ...
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Verifying an existing Micro chip RF component range with my calculations

I'm trying to understand how the microchip RN4871 chip range is calculated. I know the chip Antenna used in this module. According to its datasheet, RN4871 has a range of 10m. So my calculations ...
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2answers
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How do we separate source signals in spread spectrum?

In a point-to-point mode, that is, one transmitter and one receiver, I understand how a spread spectrum receiver can read the transmitted signal from a spread spectrum transmitter by knowing the code. ...
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4answers
610 views

Why should a receiving antenna be impedance matched to 50 ohm instead of a lower impedance?

I'm in the process of getting to grips with RF design and am having some trouble understanding why we should always match antennas to \$50\Omega\$. I understand from the maximum power transfer ...
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3answers
115 views

Will an RF modulator provide NTSC System M spec video from a DVD player?

I've been attempting to recreate the effect of an old NTSC television broadcast lately with the use of DVDs. The DVD-Video spec allows for up to 720 x 480 pixels at a display rate of 29.97 frames per ...
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DC input for SMA connector

I have a circuit with a SMA female connector for DC input. Is it possible to connect to a 1.5V AAA battery? What is the easiest way?
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37 views

Digital Frequency Measurement

The circuit in the figure below is a circuit for measuring frequencies for RKE systems (a key fob, for example). The frequencies for which this circuit was created, was used to measure frequencies ...
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1answer
54 views

Controlling a digital switch using Python through USB

I have an RF digital switch that takes two digital inputs (AB) in order to decide from which antenna port to take the input. Is their a simple way to use Python to send the AB values through the USB ...
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3answers
55 views

Reference Request: RF and EM books with a simulation componet [closed]

Does anyone have any book recommendations on EM and RF which integrates a simulator? I find EM/RF to be interesting fields which I want to get some overview of but given that it's very applied in ...
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Antenna impedance matching within metallic enclosures

What im trying to achieve is kind of an chip antenna breakout board, since it must sit within a metallic groove. The plan is a PCB of 10mm diameter with an U.Fl connector on the back and an antenna ...
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78 views

Upper RF limit in discrete design

I was curious, what is viewed as the practical upper frequency limit of circuits using discrete components? It's well known a 20Ghz oscillator is hard to design using discrete components due to the ...
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3answers
117 views

How to demonstrate mathematically the conditions of reflection in transmission line?

We are all taught about transmission lines and its associates -- characteristic impedance, reflection, standing wave, etc. It is well known what happens when a transmission line is terminated with ...
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CC1101 frequency bands are out of spec. Frequency ranges are different

The datasheet for CC1101 lists a frequency range of 300-348, 387-464, 779-928MHz. The CC1101 board I have (arduino module with SMA antenna, from Amazon) has a different range, being 309-362, 412-482, ...
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23 views

RC quality factor increase

simulate this circuit – Schematic created using CircuitLab This circuit has a bandwidth of 0.9Hz but I want even lower bandwidth. I have this RC tuning circuit. If i had an RLC tuning circuit ...
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3answers
31 views

HC-05 Bluetooth RF transmit power [duplicate]

The datasheet of the HC-05 Bluetooth module says the RF transmit power is up to +4 dBm RF, but I think that is for boundary value conditions. I am planning to use the it at a data rate of 100 kbps ...
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1answer
49 views

Is there an easy way to interface a receiving 457kHz ferrite rod antenna with a microcontroller (BeagleBone Black)?

I have a (actually two crisscrossed) 457kHz ferrite rod antenna from the internals of an avalanche beacon where 196uH <= L < 204uH and C = 560pF. I need to be able to evaluate the data from the ...
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3answers
84 views

What is purpose of Balun transformer in RF front end

In following RF receiver circuit (30 MHz), two wires of a dipole antenna are connected to SMA connectors and the signal goes to an amplifier. I don't understand what is purpose of this balun ...
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1answer
42 views

What to look for when selecting an RF detector diode

I'm currently diving into the topic of RF detectors and I ask myself which are the key criteria when choosing a diode for a given frequency range. I have a simple detector using a 1N916, which works ...
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32 views

Impedance and resonance frequency of a bias tee

I am a beginner trying to learn about combining impedances and solving for the resonance frequency. I am solving a circuit: simulate this circuit – Schematic created using CircuitLab and I ...
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1answer
33 views

Calculate power of an LTE Signal

I am looking for the formula to convert the power level of an OFDM RF signal to an absolute power level. For example if I have my typical rectangular RF spectrum and the bandwidth of the signal is ...
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2answers
541 views

What kind of oscillator circuit technology is used for 5G technology?

In particular, are 5G oscillators found in cellphones using some kind of SMT/fabricated Gunn diode or Impatt diode(on a chip)? The frequency bands(K band) are beyond the range of crystal oscillators. ...
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0answers
25 views

Determining Z1 for voltage divider of RF Matching Circuit

I have a problem where I was given an RF circuit with a series RL load. I am tasked in finding a matching L circuit and determining the values of the components. I used a smith chart to determine that ...
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1answer
22 views

What hardware limitations limit the number of stations connected to and access point chip?

I am designing a Linux based embedded access point that needs to support as many connected stations as possible. I understand the first limiting factors like CPU, RAM, and available bandwidth. ...
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1answer
46 views

Can these S-parameters be derived?

I have been trying to derive the S-parameters of a lossless T-junction of transmission lines. Here's a diagram from Google: This is an exercise in microwave network analysis, not in design, so the ...
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1answer
32 views

Inconsistent performance of circularly polarized antenna

I have a circularly polarized patch antenna for an RFID reader, with a gain of 8dBi and bandwidth from 914MHz to 919MHz and an axial of 0.34dB. I have read that using a CP RFID patch antenna means ...
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1answer
48 views

Using a via fence without a top layer ground pour

I'm designing a 4-layer 6GHz RF PCB. The top layer is a signal layer and has the RF microstrip traces and the 2nd layer is an unbroken ground plane. I'm leaning against filling the remainder of the ...

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