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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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41 views

Testing the RF properties of an enclosure

I need to measure RF (cellular) blocking properties of an enclosure. Is there an off-the-shelf set of tools for doing this? I'm assuming a MHz signal generator and an oscilloscope with an antenna ...
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3answers
77 views

Selecting coaxial cable and connector for PCB referring to required frequency

I want to transmit my 24GHz signal from PCB through coaxial to antenna. I wonder how to chose best match for it, also the power is -5dBm, 50 ohm. It's based on ADF5901 2ch PA. I have found two good ...
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1answer
111 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
152 views

Transmission Line open and short analysis

I have a transmission line with the following given parameters: Characteristic impedance at 50 ohms, phase as measured using VNA or PNA and frequency. (I can get S parameters as well) Other ...
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0answers
12 views

First order PLL power consumption

For a system level project I want to estimate the impact having a single vs. multiple PLLs. Is there a first order estimate that relates power, jitter (total integrated phase noise) and possibly ...
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1answer
342 views

Understand simple FM transmitter, inductance, resonance

I learn electronic , I try to understand this project, simplest FM transmitter : The project is describe here : https://makezine.com/projects/super-simple-fm-transmitter/ The inductance of L1 (Strip ...
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1answer
42 views

How to choose a blocking capacitor for RF power amplifier

I'm using a power amplifier that requires an external blocking capacitor for the input and output ports and I'm trying to decide the best value to use. My understanding of this is that I choose a ...
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1answer
55 views

SDR Signal Generator Frontend

I am working on a board that can take the output of an SDR (or VCO) and provide high accuracy amplitude control (+- 0.5dB). This is an opensource project that I will hopefully launch on crowdsupply ...
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2answers
164 views

How to increase sensitivity of audio-frequency pickup coil

I am building an instrument intended to pick up weak (~100 picotesla) 25 kHz oscillating magnetic fields with Faraday induction. As shown in the photo, I have a 4-layer solenoid coil for pickup ...
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1answer
162 views

How to calculate the output impedance of a adjustable RF amplifer to match the input of a mixer using SA605 chip

I have a FM receiver design I wish to implement using the SA605 chip. The stage before feeding the signal to the SA605 chip is a RF amplifier. I know I have to impedance match between each stage to ...
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1answer
245 views

LoRa SX1272 BOM missing components

I am designing a PCB that will have LoRa communication using the SX1272 , currently I am using the Reference Design for both 868 and 915MHz (image below). But the BOM attached is missing components ...
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1answer
57 views

Does a Vcc layer cause noise to a 4-layer RF PCB?

I'm designing a 4 layer GPS tracker PCB with the 2nd layer as ground and 3rd as Vcc. Is this a good practice? I know a gnd layer is good but I'm not sure how to distribute the positive of the supply ...
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1answer
168 views

Common-mode chokes in series

Is it common practice to combine common mode chokes back-to-back in series to eliminate/reduce RF interference in different frequency bands? As a random example, placing this in series with this in ...
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1answer
39 views

EN 300 328 CE radio certification with power limit

We have developed product for Malesia country, where we need local SIRIM certificate. RF module we used in our product is 2.4Ghz wifi mesh, with max 30dbm (1 watt) output power capacity. To get ...
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2answers
704 views

Formula for Field Strength

According to this document on page 3, the formula for Field strength is stated as follows: I can't find reference to this formula elsewhere and was wondering if someone can verify this is correct, in ...
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2answers
210 views

RF Voltage Multiplier

My project partner and I are working on making a rf-dc energy harvesting circuit capable of lighting an LED (even intermittently) or trickle charging a coin cell battery over a long time. We are ...
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3answers
55 views

How do I terminate a directional coupler?

I'm using a directional coupler for a radar application using frequencies of 5.3-5.9GHz. The directional coupler linked above is matched to a 50ohm characteristic impedance. How do I terminate the ...
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1answer
62 views

Contradicting ideas about differential signal route, confining fields vs Increasing impedance

By initial sense I think we must: keep pair intra-distance as close as possible for field cancellation. Fill surround of pair with GND plane and have via near to it to confine the fields, prevent ...
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1answer
82 views

Implementation of Decoupling capacitor [closed]

I have schematic for decoupling capacitors (3 set of 0.1uF,1nF,10pF): And I've implemented that in this way: And there is ADI reference for easy evaluation: And the ground pins of decoupling caps ...
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0answers
52 views

Using Arduino Uno to isolate receiving radio frequencies [closed]

I'm trying to get a project started dealing with low radio frequency scanning. I want to receive radio signals in the range of 25hz - 100hz and discard signals in a higher band. Is this ...
10
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1answer
729 views

90° Bend: Mitered vs Curved

On RF PCBs to bend a trace 90° you have many choices but among them Curved and Mitered bend considered as a good choice from performance POV (Both shown below). For many years I thought that if you ...
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2answers
34 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 ...
3
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2answers
315 views

Wi-FI Antenna DC Blocking Capacitor

I have a 2.4GHz Wi-Fi design that uses an SMA connector connected to a dipole whip antenna. The issue is the SMA connector mounts to a metal chassis. This causes a potential issue in where someone ...
2
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1answer
843 views

RF switches for RFID HF 13.56Mhz

I would like to use 1 RFID reader (13.56Mhz, protocol iso14443a) with 2 antennas in a way that I can recognize the location of the tags- if they stand on antenna #1 or #2. For that, I tried to use 2 ...
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3answers
135 views

Aluminum sheet as an underlay for electonic equipment

I am planning to build a NAS into a (sufficiently ventilated) closet. For flame protection and heat spreading, I mean to put a 2x700x550mm aluminum sheet under the equipment. Is this a good idea? ...
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6answers
11k views

Free RF Simulation Software

What free tools are there to simulate RF circuits?
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1answer
45 views

Quadrature modulation Digital to Analog

I want to use an FPGA to generate quadrature modulated signals for use with an RF transceiver (something like MAX2828 ). I am confused specifically about how the digital to analog modulation should ...
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2answers
24 views

Cellular chip antenna feedline width?

I have a chip cellular antenna from Pulse W3544B. In the datasheet it is said to make the transmission line 1.34 mm thick which I feel is too huge and also I wanted to make a strip line for impedance ...
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0answers
57 views

Can you generate a pure sine wave by mixing a fixed frequency sine wave with a variable frequency square wave?

Let us suppose I don't have a DDS available, and instead I have two square wave clocks with frequencies of my choosing. I have the impression that creating a wide bandwidth (multi-decade) sine wave ...
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0answers
25 views

ESP32: 0.1uF Cap Between SENSOR_VP and SENSOR_VN

According to the ESP32 Hardware Design Guidelines, a 0.1uF cap should be added to the SENSOR_VP and SENSOR_VN pads when using them as an ADC. Why is it then that the subcircuit schematics shown in the ...
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0answers
36 views

Passive (or very low power sensor) sensor to wirelessly receive wake signal

Context. I am using an ESP32 and a small circuit to control an electronic lock on my one of my exterior doors. It is powered by batteries. It has a door magnet sensor to detect when the door is open ...
0
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1answer
37 views

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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0answers
51 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 ...
2
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0answers
45 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 ...
5
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1answer
411 views

40 GHz spectrum analyzer with N-type coax input?

We have an old Rohde & Schwarz FSEK 30 that is advertised as having a range from 20 Hz to 40 GHz, with an N-type input connector. My conundrum is that a type-N connector with air dielectric ...
0
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1answer
82 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 ...
4
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1answer
111 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 ...
5
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2answers
810 views

Does antenna feed line length affect impedance

I built my own antenna but when I measure the impedance (VNA) I see they are off. One is 30+25J, the other 15 + 10J. I built these by hand, the only difference I see is the feed line to one is about ...
2
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2answers
1k views

Admittance inverter realisation in filter design

I read some theory about lowpass prototype filters in the "Handbook of Filter Synthesis" by Zverev and in "Microwave Filters for Communication Systems". I read these two because I want to understand ...
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1answer
73 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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1answer
305 views

Embedded microstrip antenna

How well known are embedded microstrip antennas in general and are they feasible. I want to pot a 2.4 Ghz antenna for product reliability/water and shock proof reasons, but finding information and ...
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0answers
49 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 ...
0
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1answer
276 views

IIP2 Second Order Intercept Rule of Thumb

I'm faced with the problem of explaining the harmonic production in a system where the second order intercept points of the cascaded components are unknown. As a way to bolster my explanation, I would ...
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1answer
203 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 ...
3
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4answers
867 views

Non linear device with two frequencies

I got this on an interview question and I still don't know the answer. What output will have a nonlinear device if we will give two random frequencies \$f_1\$ and \$f_2\$? I answered that it will ...
2
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1answer
56 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 ...
2
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2answers
447 views

What does the abbreviation U.FL-LP connector stand for?

I am writing up a document on a product that includes some U.FL-LP connectors. I try to always put the full version of abbreviations when they are first mentioned and I assume U.FL and LP in the U.FL-...
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0answers
177 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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2answers
42 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 ...