Tagged Questions

Exchange of information between devices. Communication can be wired or wireless.

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0
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1answer
41 views

Background functionality of a mobile phone

I'm asking this question out of curiosity. In general, we have around 6 to 7 radios in a smartphone. the modulation schemes, estimation procedures, synchronization methods are different for each ...
0
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0answers
49 views

AND gate mysteriously and ludicrously slow

I've made a 3 input AND gate from 4 NANDs in order to daisy-chain 3 motor drivers jrk 21v3 and get the current value out of them. The problem is, the command is sent OK, the driver responds OK with ...
1
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0answers
52 views

When is impedance matching necessary? Isn't it much less efficient on all other aspects?

I understand that discontinuities of the physical properties of conductors create reflections much like dioptres reflect a bit of light, but : in which cases does impedance matching become ...
1
vote
1answer
17 views

Cell Voltage Relaying in a Battery Management System

Question: If I have 48 lithium cells connected in series as a pack, how would I best go about physically implementing a system to measure, isolate, and relay cell voltages to a centrally managed ...
1
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3answers
52 views

Physical significance of group delay

What is the physical significance of the group delay of a system/filter?. Why is the slope of the phase response critical in a communication system.
0
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0answers
20 views

What sampling rates will give uncorrelated samples of x(t).considering the mean of the Random Variable 'x' to be zero?

What sampling rates will give uncorrelated samples of x(t) ? Considering the mean of the Random Variable 'x' to be zero. My Thinking: Since the mean of the random variable 'x'is zero,then it will ...
0
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1answer
60 views

Data transmission in ocean

What is the greatest depth where we can communicate with the submarine over the sonar system in ocean? Also, how can we calculate how much data can be transmitted using this method?
2
votes
1answer
40 views

when to use auto correlation and when to use fourier transform

In communication, if we don't know any prior information about the signal, we perform an auto correlation say Rx(T) and take the Fourier transform of Rx(T) to analyze the power spectrum. Supposing ...
0
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0answers
28 views

Microwave communication systems / data transfer rate vs data transfer speed

I'm researching about microwave communication systems, and I have to distinguish the difference between data transfer rate vs data transfer speed. I comment it will be something like you have a ...
0
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1answer
33 views

Fastest short-range (millimeter) wireless data transfer rates? [closed]

This question asks about the limits of wireless data transfer rates. I'd like to know what speeds have been accomplished, and more importantly, some of the design details of their underlying systems ...
2
votes
2answers
90 views

Very long transmission-line design tips

I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used: - A DC power supply (24vdc) - B Digital comm - C Ground As ...
0
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0answers
25 views

What are the most important metrics for evaluating the quality of a communication protocol

In a discussion with some Phd students I heard them mentioning Packet Loss Rate, Channel Utilization and Delay are the main metrics to evaluate the quality of a (wireless) communication channel. What ...
0
votes
1answer
28 views

parameter that limits data rate in communication

In communication, the maximum data rate that can be achieved is given by Shannon as C=B*log2(1+SNR) bits/sec. Supposing that I've a very high SNR and an infinite bandwidth, then can data be ...
0
votes
2answers
37 views

sampling rate, data rate and bandwidth

I'm new to digital communication. How are the terms data rate and sampling rate related to the term "bandwidth" . Am I missing something here?.Can someone explain me in detail? thanks in advance, ...
0
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0answers
37 views

RS485 half duplex communication issue

I have a London MR400s taximeter and I wanted to communicate with it so I have connected it with my PC using RS485 half duplex cable. I am using termite terminal for polling and receiving the data. ...
0
votes
3answers
68 views

using C libraries inside verilog

I'm implementing a radio in Verilog. the time taken for bit reversal while computing the FFT is more. it is almost equal to a symbol time (OFDM system). Can I use a FFT library in C, which can be ...
0
votes
2answers
53 views

Industry standard ways of connecting boards / modules?

There are literally thousands of different types of connectors when I'm searching on a distributor such as element14, and I'm not sure what are the "standard" ways of connecting boards together. ...
0
votes
1answer
59 views

Connection problem with RS485 system on PC with RS232 port

I am developing a system in which I have to integrate hardware. I am from computer background, so I don't have much knowledge about hardware systems. The issue is I have to integrate with London ...
1
vote
2answers
183 views

Communication between micro controllers - I2C, SPI, UART?

Basically I have two microcontrollers that I need to communicate with each other. Both controllers send and receive data. Basic idea that I have: I2C, SPI - What I think we can NOT use these ...
2
votes
1answer
63 views

Finding the Power developed by the Nominal Frequency in FM

Question The sinusoidal signal \$f(t) = \cos(2 \pi f_m t)\$ is applied to the input of an FM system. The corresponding modulation signal output for \$f_m = 1kHz\$, is $$Q(t)=100 \cos(2 ...
0
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0answers
61 views

1 Mbps satellite channel with a 270 ms delay

Consider 500 byte frames sends on a satellite channel with a 270 ms delay on send an receive by 1 Mbps rate. by ignore the length of ACK message and using Slide Window technique, how many bits need ...
1
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0answers
73 views

Finding the bandwith of FM by using Bessel functions with 1% rule

Question A 100-MHz carrier is frequency modulated by a 10-kHz sinusoid so that the peak frequency deviation is 30 Hz. Using Bessel functions with 1% rule, i.e. 40 dB down from the unmodulated ...
0
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2answers
73 views

How wireless communication works?

When an AC signal is transmitted through a conductor, direction of flow of electrons is continuously alternated. In wireless communication signal is transmitted through air, in this case which ...
5
votes
1answer
364 views

Transceivers in the field of FPGAs: When and why will we use them?

I am recently getting myself into the field of FPGA design and development, and lately I've found myself hearing a lot about transceivers. I tried searching the net for some answers about these ...
0
votes
1answer
32 views

Prove a theorem about an upper bound for entropy of a random vector

There is a theorem that: if Z is any zero-mean, complex random vector with covariance \$E[ZZ^H]=R_z\$, then \$H(Z)\leq \log|{\pi eR_z}|\$, with equality holding if and only if Z has a circularly ...
0
votes
4answers
115 views

How does a CPU choose a path? [closed]

This is the most baffling question of all other concepts. I ask my teacher "How does the computer choose a path?" "They program it" "How do they program it?" "..." I have a basic understanding ...
1
vote
1answer
53 views

Link Capacity and the Shannon-Hartley Theorem

I'm reading Computer Networks: A Systems Approach by Peterson and Davies. One of the examples demonstrates the relationship between link capacity and the Shannon-Hartley Theorem. We can find the ...
0
votes
0answers
37 views

Form of the received signal in a MIMO communication

I am reading an article which is related to MIMO communication networks. Consider that there are \$U\$ users, each of them have \$J_{u}, u=1,...U\$, different layers. We want to calculate the received ...
1
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2answers
60 views

Address and communicate with multiple devices in a matrix

I have a large matrix of devices, "nodes", that I would like to address and communicate with - assume > 50 nodes. Each of the nodes have a controller that receives data from a central microcontroller ...
0
votes
1answer
48 views

How to find the fundamental frequency and present harmonics from a graph?

I'm having a very hard time understanding frequency and harmonics and now that I'm working on problems, I am completely perplexed. The problem reads as follows - Assume that string of bits ...
0
votes
1answer
93 views

Finding the power output when one single sideband at m=0.4 is transmitted together with the carrier component which is reduced by 26dB

Question An AM transmitter has an output of 24kW when modulated to a depth of 100%. Determine the power output from first principles when one single sideband at m=0.4 is transmitted together ...
0
votes
1answer
109 views

Daisy Chaining ADC Sensors

I'm creating a grid of 200+ pressure sensors and need a clean way to get their values back to the master controller without a mess of wires. To me it seems like daisy chaining all the sensors ...
0
votes
2answers
185 views

Double Side-band Amplitude for Radio Transmission & Single Side-band Reduce Carrier for Point-to-point Transmission

What are the reasons which lead to the use of double side-band amplitude for radio transmission, and single side-band reduce carrier working for point to point transmission? Thank you for your help.
0
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2answers
65 views

communication 101 [closed]

I have a couple of really basic questions. (1) When a device(Device 1) communicates to another device(Device 2), do the devices have to operate in the SAME frequency for the data transmission to take ...
1
vote
0answers
50 views

Which communication protocol to use [closed]

Consider two devices having a basic radio transceiver (and use the same frequency) and a base station which uses a different frequency radio. The data from base station should be broadcasted to both ...
0
votes
2answers
66 views

Why is the data rate a function of the length of the transmission line?

The length of a transmission line is limiting the highest possible data rate on that line. Why are faster signals more likely to become corrupted on long transmission lines than on shorter ones, with ...
1
vote
0answers
80 views

Why is “throughput” called “bandwidth”?

But back in school, I had learned that the "bandwidth" of a communication channel is the frequency of the highest-frequency signal minus that of the lowest-frequency signal that it can carry. Yet in ...
0
votes
1answer
130 views

Why AM is preferred over FM in long distance communication?

In almost all long distance communication AM is preferred over FM. Do type of modulation has anything to do with this or it is just depending on transmitting frequency?
1
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0answers
59 views

Ethernet communication [closed]

I want to make a simple program which achieves Ethernet communication. Specially I will try to connect this ENC28J60 Ethernet LAN Network Module and make a simple real time monitoring application ...
-7
votes
1answer
94 views

Signal jammer circuit design [closed]

This is a circut for a jammer for the 450Mhz , but my calculation says it's for 277Mhz. If I want to prepare for a gsm 900 , what changes would I have to make .
0
votes
1answer
97 views

Two arduino unit communication

OK plain and simple I'm not sure to use IR or RF. This is short distance up to maybe 10 ft. I have an Arduino Uno that I have all set up here. I press a button and it carries out its code. This is ...
1
vote
2answers
83 views

Amplitude modulation of unit step signal

What will be the amplitude modulated signal, if the input is an unit step signal? You can take any carrier signal (though I would recommend sine wave) and take any carrier frequency because that is ...
1
vote
1answer
61 views

Beagleboard USB Packet sniffer

I had picked up a beagleboard a few weeks ago and had then looked into the USB sniffer project that had been created a while back. (https://gitorious.org/beagleboard-usbsniffer/) I understand that ...
2
votes
2answers
53 views

Trying to Understand Spurious Sideband Interference (and some causality problems…)

Suppose I have a radio and I intend to transmit a 0.1 µs pulse on a 100 MHz carrier. Fourier theory tells me that this signal will produce some sideband interference resembling a Sinc function. ...
0
votes
2answers
95 views

Pictures of different adapters, trying to understand how they work (PLC to PC communication)

I purchased the blue adapter in the picture as a USB/RS232 converter. It takes in the RJ12 cable from my PLC, and converts it to a USB input. Now when I try to use an RJ12-DB9 Female and then connect ...
1
vote
1answer
93 views

How does USB 3.0 negotiate power states?

I noticed, in another question, a comment regarding USB power states. I know that USB 2.0 negotiated power by tying the D+ and D- lines to specific voltages but I can't seem to find any information ...
0
votes
1answer
108 views

Can I transmit data over RJ12 to a PC from a PLC?

I have a Click PLC which has two RJ12 ports. I have successfully programmed it using C# and nModBus as a slave, but now I want to test the PLC as a master and the PC as a slave and noticed my laptop ...
0
votes
4answers
125 views

Slowest transmission speed supported by TOSLINK TX and RX?

I'm writing an Arduino communication library that uses differential Manchester coding (see: http://forum.arduino.cc/index.php?topic=257985.0). I'm wondering how to communicate between two Arduinos ...
1
vote
1answer
124 views

Shannon versus Nyquist bit rate calculations

I am confused with the shannon channel capacity formula Versus nyquist bit rate. nyquist formula contains signal levels while Shannon formula doen't, how to refer to signal Levels in shannon's ...
0
votes
0answers
14 views

How do Coherence Time and Coherence Bandwidth influence the decision on the diversity scheme?

I came across a statement in a lecture slide which states: Coherence Bandwidth and Coherence Time govern our decisions about the diversity scheme that we would choose The lecture is in the field ...