Skip to main content
11 votes

Simulate bad cell phone reception in the lab

Normally, the WWLAN testing and debug is done in electromagnetically shielded cages in labs when external tower signals (or local 3G-4G repeaters/re-translators) are too strong. The tests are usually ...
Ale..chenski's user avatar
9 votes
Accepted

Simulate bad cell phone reception in the lab

To "simulate" a poorer cell reception you can use RF attenuators between your board and the antenna. They are composed of multiples resistances building a network that will attenuate RF power very ...
Sylvain's user avatar
  • 809
6 votes

Why do baseband processors remain on, and communicating with the tower, when the phone is shut down?

that if you really want to turn off a cell phone, you need to take the battery out No, that's not true, all the phones I know can be fully switched off, usually by holding down the power button. You'...
Bimpelrekkie's user avatar
6 votes
Accepted

5G and Radar Altimeter Interference - Am I Taking Crazy Pills?

This 21 page document contains the following slide: https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf Radar altimeters are inherently wideband ...
SystemTheory's user avatar
5 votes
Accepted

Where do we use arithmetic multipliers in 5G technology?

Multiply-accumulate is a basic operation of most signal processing algorithms. It's found pretty much any place signal processing is performed - filtering, correlation, normalization, Discrete Fourier ...
hacktastical's user avatar
  • 54.5k
5 votes
Accepted

Accidentally connected a GPS antenna to a cellular connector and a cellular antenna to a GPS port. What can go wrong?

Looks like you are using an active GPS antenna which certainly means it has a LNA built-in. If you are setting-up the modem in GSM mode, at higher transmit power (if I recall correctly can go up to +...
eeintech's user avatar
  • 956
5 votes

Simulate bad cell phone reception in the lab

RF is tricky. I wouldn't mess with the antenna, I think the product should be tested in its final configuration. The reason for this is simple: when reception is really bad, your transmitter will ...
bobflux's user avatar
  • 79.1k
4 votes
Accepted

SIM808 registration denied for new SIMs

I got some help from an Aeris engineer with this one. It turns out that when a SIM first registers with the network, it requires better signal quality than subsequent registrations. When the SIM has ...
skot9000's user avatar
  • 113
3 votes

Testing the RF properties of an enclosure

The usual equipment for this kind of test includes Spectrum analyzer. A spectrum analyzer will be much more sensitive than an oscilloscope for detecting sinusoidal RF signals. Anechoic chamber, or at ...
The Photon's user avatar
  • 131k
3 votes

Simulate bad cell phone reception in the lab

Bad reception can not only stem from low signal, but also from the distance to the cell tower. Especially GSM is only designed to go over about 35km. Otherwise the "timing advance" between sender and ...
Marcel's user avatar
  • 227
2 votes

Simulate bad cell phone reception in the lab

Some possibilities: Connect the antenna to a dummy load Use a step attenuator between the antenna and the radio using double shielded coax Conduct your experiments in a shielded room / enclosure ...
Glenn W9IQ's user avatar
  • 5,594
2 votes
Accepted

SIM808 always returns the same temperature

Simcom has discontinued the Temperature readout for cost down reasons. The diodes in the module which are required for temperature readout are no longer assembled. The feature was not useful anyway, ...
doc martin's user avatar
2 votes
Accepted

Top Ground Copper pour in PCB having three RF Sections

My question is I can pour ground copper on my first layer with via fencing and stitching at a distance of wavelength/20. Should I keep the ground pour separate for LoRa, GPS and LTE module? There ...
Voltage Spike's user avatar
  • 84.2k
2 votes

Top Ground Copper pour in PCB having three RF Sections

The currents will be constrained to the area under the transmission line. You can just pour one copper. In addition they are in separate bands so even if they do interfere it will not necessarily give ...
Joren Vaes's user avatar
  • 12.6k
2 votes
Accepted

Is NB-IoT roaming possible?

If you use your favorite search engine and search for terms like "nb iot roaming" you'll find plenty of other pages backing this. I'd interpret this (2017) document from the GSMA in a way that it ...
aslmx's user avatar
  • 141
2 votes

Echo in voice to the caller while receiver with headphone hving wire replace

It seems that somehow your "replacement of wire" has caused a situation where the received signal is partly being sent back or being coupled onto your microphone circuit. Possibly both receiver and ...
Soldersmoke's user avatar
2 votes

Cellular chip antenna feedline width?

The width of the stripline is not a design target in itself. You design a transmission line to have a specific impedance, to match the antenna or whatever is at the other end of the transmission line ...
Marcus Müller's user avatar
2 votes

Can I use MCU's internal oscillator when communicating with GPS and cellular modules?

Asynchronous serial communications places demands on the accuracy of the clock. Some internal calibrated RC oscillators are acceptable, some are not, and some are okay over a limited temperature/Vcc ...
Spehro Pefhany's user avatar
2 votes

Can I use outdoor directional antenna for cellular network indoors

Indoor vs outdoor doesn't matter for gain performance. All that indoor/outdoor means is whether or not it'll stand up to the elements or not. So yes, an outdoor antenna will work just fine indoors.
Aaron's user avatar
  • 7,986
2 votes

Why is FM modulation not used in modern cellular communication?

FSK is a digital adaptation of FM. PSK is a digital adaptation of AM. The same ideas apply just the implementation is different due to tighter control of channels and timing. Bluetooth specifically ...
Passerby's user avatar
  • 73.2k
2 votes

Does using an antenna extension cable violate FCC cert?

The short answer is that should be fine. I have not seen the FCC specifically address this exact question but I think it is fair to say you can infer their answer from their published guidance on ...
Funkyeah's user avatar
  • 301
2 votes
Accepted

What are the units used in Shannon formula calculation?

Your formula for data rate combines Shannon's equation and signal propagation loss into one row. Shannon's equation for an analog communication channel subject to additive white Gaussian noise (AWGN) ...
V.V.T's user avatar
  • 4,347
2 votes
Accepted

Cellular module(4G/3G/GSM) interface to host processor or microcontroller through UART how the data rate is achieved?

How we are able to achieve cellular data rates with respect to UART Data rates? You are not able to. But then, most MCU projects cannot really take advantage of mobile network data rates in the ...
Chris Stratton's user avatar
2 votes

Getting 4G/LTE signal through sheet metal - opening/aperture size needed?

This answer, regarding metal shields, included math from Richard Feynmann's lectures. He spoke of wire mesh with specific spacings between wires. For the field inside the mesh (aperature in a metal ...
analogsystemsrf's user avatar
2 votes

Ground plane for a GSM spring antenna with 4 layer PCB

Adding a couple of points to the answer by Mark Leavitt (not enough rep to comment). I am assuming that the layer that is visible is the bottom signal layer. Microstrip is the easiest but since there'...
Tej Pochiraju's user avatar
1 vote

Why is FM modulation not used in modern cellular communication?

The original cell phones did use FM to/from the handsets, because Motorola had vast experience with FM during WW2 and perhaps before in business radios. The original cell frequency allocations were ...
analogsystemsrf's user avatar
1 vote

Can I use outdoor directional antenna for cellular network indoors

In general, a directional antenna, with its obviously higher gain, would be far superior to an omni-directional antenna. When cell phone performance is bad outdoors, the solution would be a booster ...
vu2nan's user avatar
  • 18.7k

Only top scored, non community-wiki answers of a minimum length are eligible