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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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Can wax really improve the performance of a FM transmitter?

Why would the use of wax improve the performance of a FM transmitter? Consider this from the video How to build a FM radio transmitter, at 4 min 14 secs: "Theoretically this helps decrease onboard ...
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1answer
69 views

Bigger GPS antenna better or more efficient?

I have the choice between: 1) 35x35mm GPS antenna 71% efficiency glonass, tested on 70x70 GND plane 60% gps 2) 25x25mm GPS antenna 83% GPS, 84% glonass, tested on 50x50 GND plane I have read ...
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0answers
42 views

Non resonant antenna electrical model

I apologize in advance if my question is too naive or incorrect; I am still very new in the difficult domain of RF and antennas. I know that at the first order, a resonant antenna can be modeled ...
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2answers
87 views

Can I use the same antenna for GSM and RF433 MHz?

I've already designed a PCB with GSM/GPRS chip and also with RF 433MHz receiver only (without transmitter). I would like to know if I can use the same antenna for both GSM/GPRS module and RF 433MHz ...
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2answers
40 views

RF Design - Antenna Feed-line Parameters

I am implementing a BLE device with a chip antenna. The device has already been impedance matched to 50Ω and is ready to be connected to the feedline and antenna. The antenna datasheet has a ...
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2answers
93 views

Why do long cables measured with a VNA show a “drop” in their attenuation curve?

I'm measuring the attenuation of several cables with a VNA (Keysight N5234A). When I measure the attenuation of long cables (10 m, 30 m, 40 m or 50 m) I realize that a "drop" appears at 500MHz (see ...
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1answer
151 views

Why can't we divide the electromagnetic spectrum into arbitrarily many radio frequency bands?

I understand there is concern over the limited amount of wireless spectrum available for allocation but am somewhat confused as to why. Couldn't we just divide the electromagnetic spectrum into as ...
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1answer
25 views

Rf Module Receiver With Pt2272 always gets signal

I am just trying to on and of an led with rf module. I have tried lots of module but my works end up with same result. When I feed my receiver, with led connected to data out, it always powers the ...
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2answers
84 views

differential grounded coplanar waveguide, GND-sig-sig-AVDD instead of GND-sig-sig-GND

I know we can route microstrips on top of both ground and power planes, but can we use Grounded coplanar in this arrangement? bottom is GND In top layer we have one GND and a PWR. All gaps are 0.15mm ...
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1answer
104 views

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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1answer
36 views

Comb generator vs. known EMC emitter - different measurements in shielded tent vs. 3 meter chamber

I've got an EMC testing setup of a 1 meter shielded tent, and a very high gain EMC antenna. I'm seeing a phenomena that I can't quite explain. I have a known product that was tested in an accredited ...
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3answers
87 views

Low capacitance value capacitors in LC bandpass filter

I am going to try to build a Butterworth LC bandpass filter. However, using some online calculators result in some very low value capacitors (sub-1pF). I am thinking that the performance will not be ...
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0answers
62 views

Does regularly spaced via stitching contribute to standing waves on an RF PCB?

Should vias be irregularly spaced? Can consistent spacing between ground vias create standing waves. Has anyone ever heard of this? I've been doing this for awhile and I've never heard this and ...
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1answer
60 views

2.4 GHz Chip antenna layout

I am am new to RF design and I need to place a chip antenna due to space limitations. The only antenna that is easily available to me has a very weird layout. There is no physical connection from the ...
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0answers
46 views

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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2answers
29 views

Power Ratings of RF Attenuators In Series

If I connect RF attenuators in series, does the power rating of the attenuator closest to the antenna have to be high enough to handle the expected RF power on its own? Or does the placing attenuators ...
6
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1answer
101 views

High Frequency Characteristics of Solder-Filled Vias

If a via gets plugged with solder, does this destroy its ability to pass high frequency (RF noise) currents? Since there is no longer a surface along which the high frequency currents can travel due ...
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1answer
187 views

What's the catch with these JFETs?

I'm designing a low-noise, high-bandwidth (100 MHz) pre-amp using JFETs. The choice for JFETs was because it needs to operate with large source impedances (>10 kΩ). I spent a while looking for a ...
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0answers
58 views

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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2answers
93 views

RF - sma pth connector impedance matching to cpw

I am designing a 4-Layer PCB with an SMT GPS/GNSS receiver (1575.42 MHz), where it connects to an external antenna through an SMA Connector. I have already done all the calculations of CPWG using ...
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2answers
44 views

coplanar waveguide vs microstrip for gnss and cellular?

coplanar waveguide vs microstrip for gnss and cellular? I read on internet microstrip is better for signals <30Ghz but some gps manufacturer (Delorme) said that coplanar is most efficient so it's ...
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0answers
82 views

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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0answers
20 views

RF and encapsulation materials

I have a WiFi application that we need to encapsulate for environmental reasons. We did some test shoots with Krayden PA2692 since the molder had experience with it. It's a polyamide material. The ...
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1answer
61 views

gilbert cell mixer implementation and balun

1) How do I interface LC balun with mixer using differential current RF+ and RF- input signals ? 2) How should I deal with the load impedance (RL) for LO+ and LO- which is almost infinite because it ...
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1answer
174 views

How to calculate the impedance of a rectifier?

I am working on RF energy harvesting. Now I am trying to calculate the impedance of the rectifier, in order to do the impedance matching. An antenna (50 ohm) receives RF signal (915 MHz) and finally ...
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2answers
91 views

RF communication vs Bluetooth [closed]

I'm starting a new project in my Electrical Engineering degree at my university and I need help. Overall, my project is about a mini robot that collects data and sends it (via wireless communication) ...
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2answers
110 views

Why radiowave cannot pass through steel mesh?

I cannot understand the reason for cutting off radio waves with metal mesh. I do not understand the theory that holes are small enough for wavelengths . I think the wavelength is vertical to the ...
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0answers
16 views

Combining Texas instruments' CC2592 2.4-GHz Range Extender with non Texas Instruments tranceiver (Atmega256rfr2)

Was looking at TI's CC2592 2.4-GHz Range Extender, I like it and was interested in combining it with AVR Atmega tranceiver. But in the datasheet of CC2592 it is written: "The CC2592 device is a range ...
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0answers
71 views

How does this double-tuned antenna work?

I am trying to understand how the attached circuit works, for tuning a transmission/receiver antenna (L1) for double frequency (HF, 500 MHz on the left output and 202 MHz LF right), to be used in ...
6
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1answer
51 views

Phase Noise In a Voltage Controlled Oscillator

I am particularly new in VCO design. I am required to build a negative gm oscillator with f=7.4 GHz with a tuning range of 300 MHz. The phase noise should be -110 dBc/Hz at 1 MHz offset. I sized the ...
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0answers
33 views

NFC Antenna Feed Lines

I've designed a number of boards in the past that use NFC but I don't think the RF performance has ever been exceptional. These boards have an NFC chip (generally the STM M24SR64-YMN6T/2) connected to ...
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0answers
28 views

Antenna formed from the RF module shielding wall and cover

Can anyone provide details how an antenna can be designed from RF module shielding wall or cover? More specifically if any company is making this kind of antenna product for general communication or ...
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1answer
101 views

Are my calculations wrong?

So I'm trying to make relatively a large square coil antenna that will operate at 125kHz frequency. The width and height of antenna are 300mm (30cm) and wire diameter is AWG24 (0.51mm) and I'd like ...
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0answers
72 views

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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1answer
63 views

Is it parallel or series

In the figure below, an RLC circuit, the author in the book says, that the resonant circuit sees Rs and RL to be parallel so he combined them (R total = the parallel sum of Rs and RL), is it right ...
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2answers
118 views

“RF energy harvesting” Can rf transmitter be a rf signal generator?

I'm trying to build an rf energy harvester. But having some problem. The harvester should collect the 915Mhz signal. Can I use 915Mhz rf transceiver + 915mhz amplifier as the rf signal source? How ...
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3answers
208 views

How to find the frequency of any device? [closed]

Are there devices which can figure out at what frequency every device transmitting radio frequencies operate at precisely? Say from a high of 2.4 GHz microwave to a low of 402 Hz pacemaker.
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0answers
17 views

Single Ended DAC to Differential Input Modulator

I'm trying to drive a differential input IQ modulator (LT5571) with a single ended DAC (MCP4912) for modulation of a narrow band signal (~10kHz max). Because of the nature of the low frequency ...
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4answers
2k views

Can I run 125kHz RF circuit on a breadboard?

I was wondering if making a low frequency RF circuit on a breadboard is viable.
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1answer
45 views

Cutoff or Corner Frequency for Coax Cable

I'm trying to understand better what the significance of the cutoff frequency for coax cables is. I have a case where a cable is considered for use at frequencies up to 3% higher than the manufacturer'...
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0answers
25 views

RF device connection issue

I have a surface acoustic wave based separator device built on piezoelectric (PZT) substrate and this is mounted on a PCB for the external connection as you can see from the picture. When I was ...
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2answers
83 views

Smith chart of λ/4 Transmission Line

I came across the following slide on power combiner circuit and I have questions about it. Why traverse across the upper half circle ? Why "ZT-line is the geometric mean of Zout and Zin." ?
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0answers
58 views

Audio PWM over Radio [closed]

I'm working on a project in which I must send audio over RF such that remote speakers can pick up the signal around a house/apartment. The goal is to broadcast music from a single device somewhere in ...
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0answers
28 views

EN 300 328 Receiver (RX) Blocking | BLE DTM Implementation with Signaling Analyzers?

We are working through a Nordic NRF 52832 certification, and are getting the device CE tested. We are running into some issues getting our device connected to the R&S CMW 500 signaling analyzer ...
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0answers
107 views

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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1answer
64 views

In actual OFDM trasmitter, is the stepwise waveform after IFFT put on the carrier as it is?

I simulated OFDM on MATLAB,though,the spectrum of it is not white(flat shape). Why? IFFT circuit of actual transmitter uses higher IFFT order than the count of subcarriers? P.S. I simulated with the ...
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0answers
28 views

Realizing a prototype filter in ADS or any other simulator

I'm trying to design a stub-filter, and I'm stuck on realizing the filter design using Richard's transformations and Kuroda identities. I'm building a 5th order Chebyshev LP-filter for 2.6 GHz pass-...
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1answer
45 views

What should be assumed regarding the upper frequency of sma connectors

There are infinitely many sellers of sma connectors of various kind in ebay or other stores. This one is an example. But they very seldom specify what is the maximum frequency at which the device can ...
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0answers
48 views

Microphonic SAW transmitter?

I built this very simple SAW transmitter, with a simple "spring" antenna for the right frequency. To test it, I tuned a portable receiver to around 433.92Mhz and fine tuned it until I heard silence. ...
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0answers
45 views

Reactance of a dipole antenna

I am interested in calculating the input impedance \$Z_{in}=R_{in}+jX_{in}\$ of a dipole antenna numerically. However, I am unsure how I would compute the imaginary part of the impedance (\$X_{in}\$). ...