Tagged Questions

A signal is a stream of information in the form of a varying quantity. Usually in electronics, signals can be in the form of voltages, currents, or radiated electromagnetic fields.

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0
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1answer
27 views

Choosing the right sampling frequency for WLAN 802.11ac signal (BW : 80 MHz)?

I’ve got a WLAN 802.11ac signal & it’s bandwidth is 80MHz, now I would like to know the ideal sampling frequency for this signal. As per the nyquist theorem , the sampling frequency could be 160 ...
2
votes
2answers
274 views

Area under Dirac Delta function

What is the difference of the area calculation for the Dirac delta function when using different limits of integration? $$\int_{-\infty}^{\infty}\delta(x)dx = 1$$ but ...
-3
votes
1answer
30 views

exam problem finding impulse response from a given system? [on hold]

I search but i did't find useful way to answer it please how to get the impulse response from a given given system
2
votes
1answer
125 views

Why it has used BPSK modulation after OFDM?

I am quite new to OFDM modulation. I am reading this from a tutorial. In one of its parts, for showing amplitude variation of the OFDM signals, there is a graph that has used 8 sub-carriers and BPSK ...
0
votes
1answer
63 views

Comparison of Series and Parallel LC Filters for Noise Reduction

Since there are two basic types of LC circuits that can be used for passing/blocking signals, I'd like to know the differences when using series or parallel LC circuits for noise at a known frequency. ...
1
vote
0answers
50 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 ...
0
votes
0answers
19 views

How is 802.11 (Wifi) received signal strength (RSS) measured and reported to software?

I have looked around for a while now to find an answer to this question, but answers I find do not fully answer my question. I found this response interesting from another question on this site. ...
-2
votes
2answers
49 views

Systems and signals - integration with dirac's function and step function

I'm taking the introductory course to systems and signals and the mathematics of integration using the step function and Dirac's function and For the first integral, I just don't know how to ...
1
vote
1answer
40 views

Replace Electret Microphone With Arduino Output

I have the following circuit for a simple FM transmitter. I want to replace the electret microphone with a simple tone generated by an Arduino (or equivalent) that will be broadcast over FM radio. ...
1
vote
2answers
115 views

Is it possible to amplify near zero signals?

Is there an amplifier has an ability to amplify any signal down to -500 dBm? If there is not, can it be possible? If it is not possible, what is the weakest ever signal that can be amplified?
-2
votes
1answer
59 views

Can I read coax signal entering through a coax usb adapter through a program? [closed]

I want to enter a coax signal through usb to my laptop and be able to read it so as to stream it through the web so that i can read it elsewhere reversly (using another usb coax adapter and take it ...
1
vote
1answer
32 views

Determining whether piecewise function y[n] = {x[n] if n even, -x[n] if n odd} is time invariant

$$ y[n] = \begin{cases} x[n], & \text{if }n\text{ is even} \\ -x[n], & \text{if }n\text{ is odd} \end{cases} $$ My usual way of solving time invariance problems is to do this: $$y[n-m] = ...
2
votes
1answer
61 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 ...
1
vote
1answer
52 views

VHDL internal signal assignment

I am new to VHDL and tried to implement a simple example from a book, what represents a 2bit register and the testbench. Compiling the files works well, and signals the stimulate the register (reset, ...
0
votes
1answer
40 views

How to get BPSK data from I/Q signal

I am using AD8347(0.8 GHz to 2.7 GHz Direct Conversion Quadrature Demodulator) to demodulate a BPSK modulated carrier wave. There is no intermediate frequency used. By feeding the signal into this ...
2
votes
1answer
37 views

Difference between SINR SNR

I am bit confused between these two terms. I understand SINR is signal to interference+ noise ratio and SNR is signal to noise but isn't interference noise too? Then why have he segregated these two ...
0
votes
1answer
63 views

Complex numbers manipulation

I have a complex number s of the form s=[1/sqrt(NN\$_{t})] e^{j\phi_{k}}\$ S\$_{o}\$ is another complex number. It is given that |s-s\$ _{o}\$|<= \$\epsilon\$ where 0< \$\epsilon\$< 2 It ...
0
votes
1answer
67 views

Use of Audio Tranformers in Amplification

I came across this ckt to make a wireless ear phones using Infrared Signals from IR LEDs. I am unable to understand the use of Audio Transformer here to amplify the audio signal, instead OpAmps would ...
0
votes
0answers
37 views

Linear time invariant system transfer function is known - calculate output signal

Here is my task: a) Calculate and sketch amplitude spectrum of u(t), b) u(t) is input signal for linear time invariant system whose transfer function H(jw) is shown. Calculate output signal uo(t) ...
0
votes
1answer
38 views

Sync filter in a lock-in amplifier

I've got two questions: What does a sync filter in a lock-in amplifier? What are pros and cons of using it?
1
vote
3answers
139 views

Sin signal from PWM

I wrote a program in order to use Pulse Width Modulation to simulate a sinusoidal signal. Added a low pass filter to get rid of the noise and the traces of it being a discrete signal. Added a half ...
2
votes
1answer
50 views

Radar maths I and Q components

I have just started work with radars. I read that incoming signal in case of Doppler radar is frequency shifted. On adding it to original signal we get Doppler shift. But we don't do it directly. ...
1
vote
1answer
81 views

Making Device to Send Data to Smartphones: 100m range, 1kb/s bandwidth, low power

What I want to make: A device that immediately sends a notification if the device incurs a moment of high acceleration. The notification needs to denote the acceleration. There is no guarantee that ...
0
votes
6answers
101 views

Converting PWM to bidirectional square wave?

Is it possible to make bi-directional ( symmetrical) square waveform from PWM signal? Im talking about 40 kHz frequency and 0.5v /-0.5v peak to peak signal.
0
votes
1answer
77 views

Signal targeting a cell phone

I'm a computer scientist, in college I had a (basic) telecommunications course. I've found it interesting, but had afterwards no opportunity to use apply it professionally, which is of course not ...
1
vote
1answer
51 views

Digital filter implementation

Digital filters work on digital data. When we implement digital filters in hardware, does that data which was stored in the form of bits needs to be converted back to its quantized voltage level? If ...
0
votes
1answer
29 views

Connecting GPIO and SPI signals via cable

There is a requirement in one of our systems to transfer signals from one board to another board in the same system. The signals are GPIOs and SPI lines from I.MX6 processor and it is in 3.3V ...
0
votes
1answer
34 views

Hardware Implementation of Discrete time Systems

Discrete systems work on sampled signal values. Suppose if we want to implement such a system like a discrete amplifier (i.e., \$y[n] = A\cdot x[n]\$), how do we make sure that the input to this ...
-2
votes
1answer
83 views

Radio signals blocked by red bricks / aluminum insulation

Do red bricks home/building and aluminum insulation diminish the strength of radio signals?
1
vote
1answer
42 views

Nyquist Sampling rate

We have \$z(t)=\cos(100πt)\cos^2(500πt)\$ . Find Nyquist sampling rate. Well, I know that \$f_s=2f_{max}\$. My main problem is that I am not entirely sure if I could re-write the above signal as: ...
0
votes
0answers
56 views

Simplest signal level/clip LED indicator?

I was looking to modify a circuit that would take a signal from a guitar, impedance-match, amplify and bias it so that it would be readable by the ADC of a micro-controller, effectively based off this ...
1
vote
1answer
73 views

Output resistance of Emitter Follower

I have to measure \$R_{in}\$, the input resistance seen by the signal. It was told me, that the quickest way is measuring the voltage gain using oscilloscope, insert a resistor before \$R_B\$, ...
0
votes
2answers
79 views

Internal resistance of signal source

It was told me that a signal sent to the circuit can be rapresented by \$V_{sig}\$ and \$R_{sig}\$, where \$R_{sig}\$ is the internal resistance of signal source. Now, let's consider that we have a ...
0
votes
2answers
61 views

Singnals, filters and power output

I have couple of questions: A square signal goes through a low pass filter and in the output of a circuit we get a sine. What happens there? Give a scheme? This is really weird, because, from what ...
0
votes
1answer
40 views

FM and phase/frequency deviation

I have a small understanding issue here, so I would be very glad if someone could help me a bit! We are given this FM modulated signal to volts; ...
0
votes
2answers
184 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.
1
vote
0answers
114 views

How to get fourier series of 8-bit character to be transmitted?

I have been reading this in a book, but can't understand how he used the 8-bit in fourier series equation to get the result below. The transmission of the ASCII character ‘‘b’’ encoded in an 8-bit ...
0
votes
1answer
59 views

Average signal power (signals and systems - discrete signal)

I am trying to find the average signal power of some discrete functions. For a finite interval, I can use the formula: ...
2
votes
2answers
270 views

Function generator outputs

A function generator has a 50 ohm and 600 ohm main outputs: http://www.ece.mtu.edu/labs/EElabs/EE2303/model_25.pdf What does it stand for? What is the difference? Is that about the load resistance?
2
votes
2answers
58 views

Multipath fading in mobile radio systems

Here is the problem that left me thinking: "In a mobile radio system (e.g., cell phones), there is one type of degradation that can be modeled easily with sinusoids. This is the case of multipath ...
0
votes
1answer
85 views

Drum machine circuit diagram

I'm having trouble understanding this circuit. Can someone help me get through it? I'm trying to understand what the signal is doing from start to end but keep running into electrical deadlocks.
1
vote
2answers
115 views

Which harmonics will be missing when duty cycle = 30%?

After some Googling, I found that every n=(1/duty cycle)th harmonics will be missing in the spectrum of a pulse wave. E.g. a 20% duty cycle will have their 5th and 10th harmonics missing. However, if ...
0
votes
2answers
91 views

Building an RSSI map for an indoor positioning system

As I study so far, Indoor positioning mechanisms are built with two approaches: Trilateration, triangulation: Directly calculate/compute position with signal fading/RSII data which mobile device ...
5
votes
1answer
89 views

How much difference in net length is ok?

Sorry, but I couldn't find a better title. Consider the following: I have an address/data bus interface. Intended frequency of the D/A bus would be around 10-50MHz. According to the datasheet of the ...
0
votes
0answers
34 views

Link integrity test pulse vs carrier signal

Ethernet uses a refinement of ALOHA, known as Carrier Sense Multiple Access (CSMA), which improves performance when there is a higher medium utilisation. When a NIC has data to transmit, the NIC ...
2
votes
1answer
72 views

Remove DC offset and rectify

I'm using ACS712 hall effect current sensor to detect presence of current in the power line of a remote device. I don't need exact current value but rather just want to know if it's above certain ...
0
votes
1answer
48 views

Distance confusion about Shuncom SZ05-ADV ZigBee module

I ordered this module looking at the datasheet that it has a range of 2000m LOS distance. But now when I test it, I can receive signal from a maximum of 50m distance! It sends 2.4GHz signals. As far I ...
7
votes
7answers
320 views

Measuring direction of object (or angle of signal origin)

I am interested in somehow tracking the "compass" direction of a moving object from a reference-station -- in other words, something similar to submarine sonar systems (although I'm unsure how those ...
0
votes
2answers
103 views

What is “M” in Hartley's law?

If Hartley's law is: $$ C = 2 B \log_2 M $$ I know this equation is part of calculating the capacity of a channel. I also understand that: \$C\$ is the digital bandwidth, in bits/second \$B\$ is ...
0
votes
2answers
90 views

fourier transform for non-stationary signal

I have read that for non-stationary signal we break the signal into smaller segments by applying a window function . My question is how this can help to make the signal has a fixed features or to ...