Questions tagged [rf]
Short for Radio Frequency, i.e. 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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Zero - IF receiver main limits
I was reading these slides about receivers architectures, and I have some questions about Zero - IF receivers:
Precisely:
Why is the spectrum around the carrier (i.e. the 2 "side bands") mirrored ...
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Is the TPS54202 buck converter a good solution to pass the FCC SDoC?
I want to design a PCB with the ESP32-WROOM module which has bluetooth. I want to pass the FCC verification. I would use a linear regulator, but it makes too much heat. My input is 14V car battery, ...
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What IF amplifier configuration can I use in my receiver?
I am making a superhet SSB CW receiver with a crystal filter on the input after the mixer.
Do I have to use IF transformers as the coupling method (1) or can I use capacitor coupling with resistors ...
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"Interpolation" oscillator working principle
I was reading Soviet amateur electronics magazines and stumbled upon an interesting oscillator.
It uses two high-frequency crystals (27.14 and 26.67 MHz) to to get a low-frequency output (465 kHz).
...
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RFID reader technology
Hopefully this isn't too broad of a question, I will narrow it down the best I can.
We need to add RFID tags to feeders on our pick and place machine, to determine that they are loaded into the ...
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Axial ratio of a square microstrip antenna
I am currently designing by CP microstrip antenna using CST. The picture is shown below. However, when I view the axial ratio plot, also shown below it is way above 3dB at 90 degrees. the patch is 31,...
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Quality Factor and Frequency Bandwidth in a matching network
it is known that the Quality Factor appears in the formulas for transformation of an impedance series bipole to a parallel one. A simple example is this one:
Now I have three questions:
1) I have ...
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Amplifier for pulsed Radar motion sensor
I have a radar motion sensor, IPM-170.
The output of the sensor is as follows:
The AC motion signal is -+300uv and there is a DC bias around 150mv.
I am applying the following circuit so I can run ...
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AD8318 Maximum Input Voltage
let's consider AD8318, a chip which contains a logarithmic amplifier, often used for power measurements.
I have read its datasheet and there is a thing that I do not understand: no maximum input RF ...
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What is input to the RF power amplfiier (gate of the MOSFET)?
I have read that the RF PA is a block just before the antenna. So, the input to the RF PA (voltage signal at the gate of trasistor in the PA) should be a modulated signal and thus the PA just does the ...
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Deriving admittance matrix for shortened quarter-wavelength transmission line
For Reduced-size branch-line and rat-race hybrids for uniplanar MMIC's , how to derive equation (2) ?
and is the imaginary constant j needed in equation (1) ?
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Spectrum Analyzer Sweep Times Sub 1-ms vs. EMI Test Receivers?
I've got a Rigol DSA 832 and I have a client design that sends out a 1ms message every 100ms.
The original protocol was a 1ms message every 6 seconds, which was darn near impossible to capture on ...
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Power efficient oscillator topologies?
I'm building an oscillator for a battery powered capacitive position sensor and I need it to have a high swing (>800 mV) at the output while keeping power consumption low enough. I'm feeding the ...
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Design and simulation of cross coupled oscillator in ADS
I am currently designing a low power consumption and low phase noise VCO in ADS. But while performing the transient response I'm not getting the oscillating waveform in the output. I have attached the ...
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LNA circuit not working
I am trying to simulate a LNA circuit from the book "Design of CMOS RF Integrated Circuits and Systems"
However, the LNA circuit still does not give POSITIVE GAIN.
Any help ?
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Assuming a coaxial cable is matched with the load antenna, what is the DC voltage at the entrance of the cable if the length of it goes to infinity
This is a question from a previous year's exam which I'm having difficulties solving.
Given a load impedance of Zl = 48-i14 [ohm], we want to plan our coaxial cable with an impedance that gives a ...
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How to read polar coordinates of radiation pattern
I have a PCB antenna which datasheet provides the following radiation pattern graphs:
There seems to be a "weak" direction which the antenna signals is going to be very weak.
Which direction is the "...
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Are magnetically tunable surface acoustic wave devices commercially produced?
I have been reading up on studies of magnetically tunable surface acoustic wave devices, in general they note the relative velocity change or in some cases a frequency shift if it is part of an ...
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Has anyone designed a low noise amplifier in the ISM band (24 GHz) using the discrete fet CEL CE3520K3?
I have been trying to design an LNA in the 24 GHz ISM band using CE3520K3.
The FET is inherently unstable and one cannot use resistor loading at the input, resistive loading at the output, source ...
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Unitary property of scattering matrix
From s-parameter lossless network definition , The sum of the incident powers at all ports is equal to the sum of the reflected powers at all ports.
But how do we derive the above unitary property ...
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Measured doppler shift error biggest on direct flight on target
Following scenario:
There is a radar on a plane which emits a CW Signal and outputs the measured doppler shifts from the reflection of a static target.
I can see from the data, that the error of the ...
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Unexpected loadline in ADS simulation
NOTE: This question is related to a homework project.
I’m designing a PA for the 850-880MHz band. We have quite a lot of freedom for doing that. Only two requirements are specified:
The amplifier ...
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Single-frequency AM Receiver?
Previously today, I tried to make an extremely simple AM receiver without a tuner. It didn't really work (I'm still trying to work on it), but I also tried to make an AM receiver that is tuned to one ...
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GPS PCB RF Design and Performance Impact
I have designed a vehicle tracker for two-wheelers which is installed in 500 bikes. I am facing an issue with GPS performance (lock percentage is quite low for more than 75% bikes). This makes me ...
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Low latency wireless audio transmitter
I am working on a project that requires low latency wireless point to point audio transmission at short distance using a digital transmission technique (ideally 24bit 96khz audio, 30 metre max) at a ...
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Schematic diagram of a double-balanced Gilbert cell mixer
For the following gilbert cell circuit, I have few questions.
I understand that R1 to R4 as well as M1 to M6 are parts of the double-balanced differential topology which helps to eliminate the DC ...
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First PCB project design critique requested (RF) EDITED
This is my first ever RF PCB project and it'd be great to receive some guidance to make this project 'first-time-right'.
It's purpose is to transmit and receive signals at two different frequencies: ...
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How does this transmitter work/how to tune it?
I have used a few 433MHz ASK transmitters. They're cheap, readily available, and work reasonably well.
Based on this application note from Murata I tried to build my own.
I replaced the NE68030 ...
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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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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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Creating a balanced dipole from two monopole chip antennas for use on small PCBs
I'm trying to use a monopole chip antenna on a PCB much smaller than the one recommended in the datasheet. I am wondering if I can get away with a much smaller board by using two monopole antennas ...
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How to find new ABCD parameters when reversing 2-port network
I have an ABCD matrix represenataion which is defined as:
For such a problem, what approach should I follow in order to organize the new ( reversed) network ports voltages and currents properly. I ...
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Near-me area network embedded emitters with a Raspberry Pi server receiver
I am making a toy for 4-year old children with 10-20 pieces in wood, as in this picture with four wooden boards with names:
The goal is that each wooden board triggers a sound, such as "Hello" or "...
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Electro magnetic interference with Arduino Uno and a portable radio
I'm surprised when I'm working with Arduino Uno, by just sitting beside a portable radio, like when I was powered on both Arduino & Radio and when they are close to each other I got some noise ...
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How to convert Inductor to series transmission line?
My objective is to understand the travelling wave amplifiers, but I am stuck on how to realize inductors in transmission lines.
But, I am basically stuck on how to convert a series inductor to a ...
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2 tone test with RF mixer
I am designing a system that uses RF to probe the nonlinearity of a target. It works as follows.
Transmitter sends out 2 RF frequencies, such as 900 and 910MHz.
The target/reflector has a ...
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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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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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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 ...
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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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Active phased antenna array for Wi-Fi efficiency compared to a directional antenna?
I'm interested in mesh networking of poorly controllable autonomous aerial vehicles (like blimps), so i wonder whether it is viable to use a phased antenna array versus a few traditional directional ...
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True near field distance for a short monopole antenna
Antenna properties:
Height x Diameter = 3.3 inches x 1.4 inches
Test Frequency: 900 MHz
(Wavelength = 33 cm or 13 inches)
I see some conflicting formulas to calculate the near field distance for ...
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Help decoding line code
I have collected a burst signal from a radio device using an RTL-SDR and gnuradio and demodulated the FSK, but am having trouble deciphering what the line code is.
Signal is at 151.3MHz
Here is the ...
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LoRa radio transceiver for PtP mesh?
So after being informed on the Amateur Radio Exchange this isn't quite HAM/Amateur Radio, posting here.
So I'm, well, very new to general RF/radio in general other than basic WiFi, but I'm looking at ...
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Interfacing LoRa SX1301 IC to third-party RF front-end
I am reading the datasheet of SX1301. I got struck at SX1301 RX operation using a third party RF front-end topic (Page 22). The page (22) says:
In that mode the ...
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Self Resonant Frequency VS Package Size for capacitor
In general belief, smaller capacitors have better charactristic(more capacitive behaviour) in high frequency than bulky capacitors.
On contrary in one of my RF project (8.5GHz - 9.5GHz) when checking ...
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Unbalanced RF output to FEM module with balanced input
I have a working ZigBee system based on ATMEGA256RFR2.
(Datasheet)
On page 33 you can check the RF system of this IC.
Now I want to use a FEM module to increase the performance and I found the ...
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How to go about decoding baseband from RF?
I'm designing the avionics portion of an ADS-B transponder and have everything done except the one thing I just can't figure out is decoding and encoding the baseband signal. I'm kind of under the gun ...
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Clamp-biasing at JFET Gate in RF Circuits
Reading the book Communications Circuits by Clarke and Hess, I came upon a chapter entitled "Clamp-biased Square Law Device" (Chapter 4 - 4.9).
It took me a while to realize that they were ...
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How to simulate an RF power source in LTSpice?
I am testing out an RF power amplifier that I have designed in LTSpice. How do I model the input RF power source to the amplifier in LTSpice?
