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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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How does FCC define “co-located tranmitters”? What testing is needed for a product using multiple approved modules?

I'm planning a design that will use a Raspberry Pi and an XBee PRO 900-HP, both of which are certified modules. I am not an RF engineer and this would need to have the absolute bare minimum of ...
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39 views

Appropriate driver amplifier to amplify an FPGA pin voltage for RF applications

I'm trying to built a nanoseconds RF transmitter using an FPGA and an up-converter. However I don't know the correct configuration (I prefer a single IC) in order to drive a nanosecond pulse (pulse ...
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23 views

Calculating low-pass filter prototype specifications

So I'm just wondering what I need to figure out before I can actually calculate anything here, (only considering the a-part now)? I understand that 2.5 GHz should be 3dB and 3.75 GHz should have 25 dB ...
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24 views

Using TWS-BS-6 and RWS-374-3 for analog audio transmission?

I'm really new to electronics and thought I'd build a simple walkie-talkie as a hobby and education project. A friend suggested I consider using the TWS-BS-6 and RWS-374-3 for the radio transmission ...
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103 views

How is the power of a SSB-SC signal half that of DSB-SC signal?

Intuitively I get it that my SSB power has to be half of DSB power but mathematically I am unable to get this. Say working for tone modulation. $$m(t)=mA\cos(w_mt)$$ where m is modulation index. ...
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29 views

Unleveled vs Leveled RF Power

I'm reading over a manual for a RF generator and I've come across the terms leveled and unleveled RF power. I'm curious what the difference is between leveled RF power and unleveled RF power.
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55 views

JFET colpitts oscillator - very unstable

I've designed, simulated and build this simple JFET colpitts oscillator and I couldn't get it to work with real parts. I didn't have BF256B jfet model so I simulated it using some generic one. The ...
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1answer
31 views

Finding Z-parameters from a two-port network and using them to find S-parameters

So I have the two-port network and I want to find out the Z-parameters of it (and later, use that to find the S-parameters). For the assignment, \$R_x=8Ω\$. From what I understood, I should null ...
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23 views

s-parameter matrix analysis

So I'm trying to figure out how I can analyze S-parameter matrices. The i. should be pretty straightforward, though I'm not 100% sure if I am correct with what it means. I'm assuming that there's ...
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20 views

Correct way to calibrate SDR RX into a measuring receiver

While playing with my SDR (Software Defined Radio) Board, I was interested in performing a TX output power table at different center frequencies and TX antenna gains. However, unfortunately, I do ...
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67 views

Cell Tower ERP a Specific Case

If a specific cell tower contains transmitters with an output power of 120 W along with antennas having 16.5 db of gain, would this not result in an effective radiated power in the kW range? The ...
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66 views

How to make the receiver send signal back to the transmitter with wireless RF 433MHz module

I want to buy a RF transmitter & receiver 433MHz on the internet for our research project which deals with radio frequency. I badly need the concept of having the receiver notify the transmitter ...
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40 views

Receiving DCF77 clock radio signal

I scavenged a loop antenna from a meteo-station that gets synched from DCF77 (77.5 kHz) clock signal. My idea was to implement a direct down-conversion with a microcontroller and decode the message ...
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2answers
36 views

ETSI EN 300 220-1 General performance criteria

In Chapter "general performance criteria" the standard states that these criteria, for receiver performance tests, are equivlent: after demodulation, a data signal with a bit error ratio of 1% ...
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50 views

Keyfob decode using GNU Radio Companion

Found this project to decode Hella Keyfobs https://github.com/bastibl/gr-keyfob Try to decode mine, but somehow the signal is way different from the one from the above Repo. From the repo: Mine: ...
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Power spectral density FCC vs CE 300 328 difference

Both FCC and CE 300 328 has power spectral density test, may be with little difference. We bought 2.4ghz radio which has FCC pass report with 30dbm power and its pass the power spectral density test. ...
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1answer
33 views

How to convert from S-parameters to power gain?

With reference to the part below, which states 17dB gain at 500MHz for Vce = 12.5V https://www.digikey.co.uk/product-detail/en/stmicroelectronics/PD55003TR-E/PD55003TR-E-ND/1664253 It's data sheet ...
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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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1answer
54 views

Device's ground riding on a non-ground signal

The question is somewhat conceptual, feel free to close if it's too off-topic. If I take my portable (battery-powered) oscilloscope and try to measure the mains voltage, the connection polarity ...
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1answer
88 views

F-parameters instead of S-parameters

What are the F-parameters, how are they computed in CST and what is the relationship between S- and F-parameters? In CST, they can be obtained, when running the integral solver and having a farfield-...
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2answers
81 views

Colpitts values for NXP's SA605?

I'm trying to put together a simple superhet radio, receiving at 161.75MHz (this is for AIS reception.) I've been trying to design around NXP's SA605 chip (see SA605) but I'm having a hard time ...
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4answers
130 views

How to radiate a positive oscillating voltage?

I am trying to build a simple AM transmitter, transmitting only a carrier wave and thus silencing the noise on my radio standing next to my circuit. I built this circuit on a breadboard. It's a ...
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what is the purpose of having a “thru cal” on RF PCB?

I often find a thru cal on RF PCB like picture below. What is the purpose of having this thru cal thing on the board? One purpose I can think of is to test whether the designed transmission line is ...
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Questions about stability circle and impedance matching

I'm a RF circuit beginner and got stuck in stability related issues. According to Pozar's textbook, output stability circle is a contour in the "gamma_L" plane and its arc represents the "gamma_L" ...
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1answer
46 views

Coax cable shielding understanding at AC

I know that AC changes its polarity once a cycle. We use coaxial cable for protecting the signal from magnetic interference. But if the cycle is negative then it it will flow in the shielding, won't ...
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2answers
48 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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4answers
104 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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13 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
50 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
65 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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3answers
72 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
70 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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1answer
65 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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1answer
80 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
94 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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1answer
787 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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1answer
52 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
32 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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77 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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83 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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39 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 ...
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1answer
55 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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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
49 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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0answers
53 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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1answer
79 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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54 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
109 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
56 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 ...