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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Cell phone detector circuit design [on hold]

This circuit I found on the internet detects mobile frequencies that transmit to the base station in the range of (0.9 to 3 GHZ). I want to understand how can I get or calculate the values of some ...
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36 views

What are the trade-offs of transmission bands?

If I were designing an RF circuit how do I determine what band the circuit should operate on? What are the trade offs? and why is the higher the frequency the lower range? It is quite un-intuitive for ...
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49 views

MHz oscillator probe impedance?

I find something weird going on in my 100MHz oscillator probe. I always thought the probe has a resistance of 1M ohm, but apparently at 13MHz, when I put a 2.2k ohm resistor in series with the probe, ...
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1answer
43 views

Improving RF sensitivity

I'm trying to improve the range on my 433 MHz radios that are using the CC430F5137. Based on 25.3.3 in http://www.ti.com/lit/ug/slau259e/slau259e.pdf, it seems like decreasing the RX filter BW can ...
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38 views

Rf amplifier in AM receiver

I have an Analog electronics class project about AM receiver. In the project, it is stated that RF amplifier will be used after antenna. What kind of amplifier is this RF amplifier, voltage, current ...
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2answers
52 views

Buffering/matching large signal to drive 5 ohm capacitive load at 13MHz (RF)

I built a Pierce oscillator that generates 13.5MHz @ 7Vpp signal from a V_cc=12V. But I need to drive a capacitive load of 5 ohms @ 6Vpp. I'm not sure how to do this. First I need a buffer to prevent ...
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1answer
37 views

How to detect several agents within a radius, what is the best and easiest way to do it?

I have a room with 30 objects which may or not be present, and I want to be able to detect which objects are in the room. My first idea was to attach a RFID tag to each one of these objects and have ...
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40 views

Self-oscillation in a commercial RF amplifier

I purchased several 50 ohm (in/out), 35 dB gain photomultiplier tube (PMT) amplifiers from a vendor assuming I could use them to read out the voltages on my PMTs. The amplifiers are AC coupled with a ...
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55 views

Switching between transmit and receive in a transceiver

My current project involves building a proximity sensor that uses RF and is low-cost (so no microcontrollers). I've come across two circuits that look quite promising, a transmitter and a receiver. I ...
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1answer
33 views

TI CC2538 radio turns off after connecting UART

Need help regarding Texas Instruments CC2538 RF module. (https://store.ti.com/CC2538DK-CC2538-Development-Kit-P4532.aspx) The module has an operating range from 2.1V to 3.6V I'm trying to use the ...
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1answer
30 views

Analyzing reflection and transmission without a VNA

The wikipedia page for network analyzers mentions "reflection and transmission of electrical networks are easy to measure at high frequencies" but doesn't give any hint on how this is done or what it ...
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1answer
125 views

Impedance matching with only capacitors?

I need to do impedance matching for 33 + j32 ohm source and 16.5 + j0 ohm load. The copper traces adds 99 ohm impedance and 20 degree electrical length. According to smith Chart below, I need to use ...
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57 views

cellphone detection

I'm searching for advice of how to detect cellphones. So, I think that I need a Radio-frequency detector. From the scratch I'm planning to use arduino with some-board (or make it by myself). There are ...
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1answer
28 views

How to determine dielectric constant and loss tanget of a PCB board at a specific frequency?

I need to know dielectric constant (relative permittivity) and Tan loss of a FR4 board at 2.45 GHz. The specification of the manufacturer is as it is below: Dielectric Constant: Test method ...
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0answers
12 views

How to De-embed 3-port Network on ADS

ADS 2013 no longer has odd-port de-embedding. I want to eliminate the effect of a 3-port balun board on the measurement of the antenna. How can I do that in ADS? I tried using a 4-port de-embedding ...
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1answer
44 views

How to minimize characteristic impedance mismatches caused by vias?

This question springs from an answer here. When using stripline configurations for rf signalling, the conductors are routed on an inner layer of the pcb, sandwiched between two ground planes. I ...
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2answers
48 views

Which of these Stripline Impedance Calculations is correct?

Different sources are giving me drastically different characteristic impedance values, and am hoping someone will verify them for me. Generally, with microstrip, I start with an online calculator to ...
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2answers
32 views

Shared antenna on multiple 2.4Ghz receivers

I want to use several 2.4 Ghz transcievers (not sure which IC yet, either Atmel AT86RF*** or TI CC) in order to build a simultaneous multi-channel sniffer. The transciever output is differential. I am ...
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40 views

Balun/matching network question

I am having problem to verify what an app note (AN068) explains to calculate Balun values. I would appreciate if someone could tell me what/where am I doing wrong? The summary of the RF part: Blue ...
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1answer
45 views

303 Mhz Wireless Transmitter

I am in need of a 303 MHz transmitter. Similar to this (just different freq): https://www.sparkfun.com/products/10534 If I purchase the item above and replace the crystal with a 303 MHz one like ...
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1answer
22 views

Using RF for relative direction finding for short ranges (sub 10m)

I'm considering building a short-distance direction finder to determine the relative position of two objects. I want to be able to determine direction through other objects, which eliminates IR or ...
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0answers
32 views

Best RF frequency for my application

I need to design a device that can transmit an RF signal about 200 meters. The data transferred is very simple. One device simply has a button, that when pressed transmits a two-digit ID to the ...
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30 views

Bluetooth antenna design

I am building a system with bluetooth/wifi/GSM. Since I am an RF noob, I have some questions regarding antennas. Some modules come with loop antenna and if you want to create your own PCB there is a ...
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1answer
28 views

Low latency rf link

I am working on making a low latency rf link that will be used as part of a feedback loop on a remote sensor. Because it is real-time the delay needs to be as small as possible (if sub milliseconds ...
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2answers
521 views

How does the plastic-tube inductor in this wireless transmitter work?

This single layer PCB (solder side shown here) is from an old fan remote: The inductor in the plastic tube is not connected physically to any components; however, the two loops of wire surrounding ...
6
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1answer
68 views

Preferred balun location? (Are differential microstrips preferrable to single-ended?)

I'm designing a PCB with a transceiver that has differential signal pins for rf. These differential signals travel to a balun, which transforms them into a single-ended signal (50-Ohm ...
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3answers
76 views

How to interpret these antenna radiation patterns?

The datasheet for this chip antenna shows a couple of radiation plots, but I don't know how they correspond to the physical orientation of the antenna. I want to orient the antenna so that the ...
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2answers
41 views

Peak-to-peak voltage of WRL-10534?

I'm experimenting with the 434 MHz RF Link transmitter (WRL-10534) from SparkFun. I'd like to determine the peak-to-peak voltage of the RF output, but I don't have access to an oscilloscope that can ...
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3answers
100 views

Is there a metal that will not interfere with smartphone reception as a case?

I want to design an iPhone case that will include a metal plate on the back of it. Is there any kind of metal that will not interfere with the phone's reception?
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1answer
51 views

Power output needed to go through a car

I need to know the power output needed for transmitter if I want that receiver catch this signal? In details, there is a tunnel 4 by 4 meters and a cars in it, cars have a receiver inside and ...
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52 views

Spy camera in a pen with streaming

I want to have a device in a pen, which can somehow transfer video data (or even photo would be great) within a 80-120m range. There're lots of "spy pens" on eBay, but I need one to be able to do its ...
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3answers
247 views

High Altitude Balloon Communication

Our team is planning to make a HAB (High Altitude Ballon) project for our university. We are planning to use XBee pro 868 RF modules (we are in Europe so we can not use 900 MHz band). We have to ...
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4answers
675 views

What is the purpose of holes on edge of the PCB?

Here is a photo of one of Texas Instrument's RF EVMs. Please pay attention to edge of the PCB that has multiple tiny holes. I marked 3 of them with a red circle on the photo. What is the ...
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41 views

Antenna to reject 5.8Ghz Interference

I live a couple miles past where "normal" high-speed internet is available, and for years I have used a radio WAN link on a 70' radio tower to connect to my ISP in town, 4.65 miles away. I have a ...
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1answer
58 views

Cheap 2.4GHz Antenna Tuning

I am planning on making a board which will have some 2.4GHz RF capabilities, and would like to know if there is a cheap way to tune an IFA cheaply. If I had access to the right equipment I could ...
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2answers
252 views

Does this simple RF transmitter circuit actually work?

I've come across this circuit a few times while searching for simple transmitter circuits, and decided to try it. According to this site, it should be transmitting at around 90Mhz. ...
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20 views

Reading Mac data of Zigbee protocol stack

I am working on a project using one of the popular Zigbee based RF-MCU Mac-codebases. I have integrated a sensor to the MCU and the same is reading data and I am sending data to the gateway using the ...
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51 views

ZigBee and Radio Interference [closed]

What are the mechanisms implemented in ZigBee to overcome Radio Interference?
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1answer
45 views

What does it mean exactly “ averaging over eight symbol periods” when calculating RSS?

When reading about RSSI, I usually found that RSSI is measured by averaging the signal reading over eight symbol periods, I could not understand what does it mean exactly and how RSSI is calculated by ...
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2answers
73 views

Pseudo RF in embedded boards

I noticed that wifi-capable embedded boards integrate the RF into the board design instead of having a separate, add-on wifi card. They have meshes that are etched into the board and the rest of the ...
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2answers
77 views

Pass DC through (passive) highpass filter?

Background: I'm a student, working on my final year project. I am designing a front end for a software defined radio. We have an IF frequency at 36Mz (and a BW ~8MHz). We are bandpass sampling this ...
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1answer
41 views

Helical wire antenna normal mode or axis mode?

I have bought theses two RF-transceiver CC1101 module from e-bay(image below), and I want to know if it is a helical antenna in normal mode or in an axis mode. The specification doesn't say anything ...
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3answers
624 views

What will it take to build a DIY 2km (city conditions) RF transmitter (433Mhz)?

This is my first question on this site. I am not an electronics/electrical engineer so pardon my depth of knowledge. I am trying to build an RF transmitter/receiver. These are my end goals : a text ...
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1answer
51 views

coplanar transmission line on both sides of a four layer board

I am designing a four layer board in which i have to run two 50 ohm traces one at the top and other at the bottom side of the board. I have decided to use Coplanar wave guide for both the traces. I am ...
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1answer
61 views

How much RF-interference does a typical desktop computer produce? How much does a metal case without windows reduce it?

It's fairly common now to see desktop computers in cases with large windows cut in the sides. I've always been under the impression that if unshielded, computer equipment will produce a lot of radio ...
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1answer
42 views

pH sensor project: trouble with RF interference

I built this pH sensor project on a breadboard and I'm having a big problem. The output on the voltmeter is completely erratic, and I'm pretty sure it's due to RF interference. When I connect the ...
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43 views

What's the best workflow for creating gerber files from, say, an HFSS project?

I am curious how everyone gets their RF/microwave designs from their preferred simulation/design suite (HFSS is just an example) into a gerber file for fabrication. What's a good workflow, including ...
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How to determine a Signal Generator's Marker (Event) output delay?

I am using an Agilent N5182B Signal Generator for modulating a 2-FSK waveform on a 160MHz RF carrier. For that, I am using a baseband waveform (I/Q mode), generated by a Matlab FSK modulator script. ...
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1answer
44 views

Derivation for the skin depth of a wire given RF signal

I was looking at the equation for the resistance of a wire under RF signal and failed to produce similar results. On WikiPedia article on skin effect this resistance is given by: $$R = \frac{\rho ...
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2answers
40 views

RF Combiner Hardware

I have say, 4 170 MHz signals coming in on 4 BNC cables. I would like to add these signals together. Is there a name for a piece of hardware that does this? Are there any special considerations I ...