10
votes
Accepted
Impact of rain fade on 60 GHz radio links
There is a good summary of rain fade at 60 GHz here "Is There Rain Fade on 60 GHz Wireless Signals?"
This includes estimates of attenuation for various levels of rain:
Drizzle (.25 mm/h)...
- 5,761
6
votes
Accepted
Is it theoretically possible to make an anti-jammer for WiFi?
No, you cannot jam a jammer away. For two signals to cancel, they need to be perfectly 180° out of phase. But the phase changes with distance from both transmitters - so the only possible scenario ...
- 90.3k
5
votes
Accepted
Why do amplifiers have minimum frequencies?
Low frequency noise can become fatal to the high frequency noise performance if the low frequency signal is not prevented to be amplified. Low frequency noise can be strong in semiconductors when ...
- 136
5
votes
Why do amplifiers have minimum frequencies?
What would the impact of using a microwave LNA or PA on HF frequencies be?
If it's AC coupled, it has a low frequency cutoff.
Besides that, there's going to be filters and bias networks ; if the ...
- 71.9k
3
votes
Why do amplifiers have minimum frequencies?
A while ago I played a little with SiGe transistors such as BFG425W and BFP650. I built some cascaded amplifiers and a noise source. The noise generator had about 5 stages of amplification.
I noticed ...
- 2,603
2
votes
Accepted
How do I calculate the hex value for the bandwidth setting on an SX126x?
I agree that hardcoding the table is the most appropriate way.
But for reference, the formula appears to be approximately:
Bits 0-2 of register value: exponent
Bits 3-4 of register value: divider
BW ...
- 7,414
2
votes
Antenna polarization confusing
I get it for a regularly shaped antennas, however, how would I know it in case of a meandered line.
Not at all from looking at it alone.
First of all, this seems to be a multi-band antenna, which ...
- 90.3k
2
votes
Multiple Direct Digital Synthesizers (DDS) to Increase Sample Rate
Old thread, but the AD9166 can do what you want. It has a high speed DAC going up to 12 GS/s and the NCO can be digitally modulated with I/Q at several GS/s. So the data stream is not that much faster,...
- 21
2
votes
Accepted
Balanced vs differential signals
This is my view of the problem
According to the electromagnetic theory of guided TEM waves: the current flowing at the surface of the central conductor and that at the inner surface of the shielding ...
- 783
2
votes
Balanced vs differential signals
Here are some equivalent circuits you may find illustrative:
simulate this circuit – Schematic created using CircuitLab
Consider for sake of argument, the values of impedances don't matter, ...
- 27k
1
vote
Accepted
Matching network for a radio
Here is the datasheet for the IC
https://www.nordicsemi.com/-/media/Software-and-other-downloads/Product-Briefs/nRF52840-SoC-PB-23.pdf?la=en&hash=60847B0615FA41626CC73C9E5286C34F2481685E
General ...
- 742
1
vote
Matching network for a radio
It may be that the transmitter output impedance is low, but it'll usually be designed to drive a 50 ohm load through its specified matching network. Similarly, the receiver input impedance may not be ...
- 2,525
1
vote
Accepted
3 dB Power Divider Used as Power Combiner S Matrix Explanation
The sum port of a Wilkinson is a superposition of the S-Matrix. Your answer is correct.
\$ [S] = {\frac {-j}{\sqrt {2}}}\begin{bmatrix}0 & 1 & 1 \\ 1 & 0 & 0 \\ 1 & 0 & 0 \end{...
- 237
1
vote
Accepted
AM radio spectations - how does it work
That is your final amplifier. It is also your oscillator and modulator.
L1, C3, and C4 form a pi filter. However, they are also a positive feedback path, sending the emitter signal back to the base ...
1
vote
Frequency detector/comparator problem
There are a variety of frequency-to-voltage and voltage-to-frequency ICs, if you want to go down that route.
Another option, if you want to make such a system, would be to use the output of a non-...
- 29.6k
1
vote
Accepted
Frequency detector/comparator problem
NOTE: In your 2nd and 3rd schematics, components with the same reference designators have different values and do different functions. This is very confusing. Please update your post so the ...
- 18k
1
vote
Accepted
Implementing a light software stack on STM32 to send and receive data using 433Mhz RF modules
How do I generate the training preamble?
alternating 1 and 0. For 36 bit long sequence, generate:
010101010101010101010101010101010101
Do I have to do this for ...
- 338
1
vote
Accepted
Can you calibrate your VNA to show matching circuit behavior, without the antenna connected?
Can VNAs be calibrated somehow to show the behavior of VNA->Match->Antenna even though it is actually physically connected as ...
- 162k
1
vote
Taiwanese Regulations of 433 MHz
For the current document in English have a look here: https://www.ncc.gov.tw/english/files/12013/102_968_170120_1.pdf
All other links seem to be dead.
The relevant paragraph appears to be ...
- 11
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