Generic term for coding information onto another carrier signal

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27 views

internal circuitry of LM1596/1496 perform modulation

The following is the inner circuitry of LM1596 which is a modulator and a demodulator: I wanted to get an abstract idea as to how this circuit actually works and performs de/modulation... I have a ...
2
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2answers
55 views

How are the original signal and the AM signal related?

Use the TIMS “Variable DC” module to generate a 1V DC signal. Use the “Adder” module to add this DC signal to the message signal generated in task 1 (this will produce the ...
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1answer
54 views

carrier in carrier [on hold]

I am working on Comtech modem 625 there is an option carrier in carrier that mean we can transmit and receive the signal at a same time. I want to know this logic how can we communicate by using ...
11
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4answers
3k views

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?
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1answer
56 views

About the combination of two signals with capacitors

Here is a link of an article I've been reading. http://www.analoguehaven.com/moog/thereminblack/hotrod.pdf In page 4 there is a circuit schematic. Notice there is a part called variable pitch ...
2
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1answer
51 views

Orthogonal Frequency Division Multiplexing (OFDM)

I am not a professional but I'm trying to figure out how OFDM works. It is clear to me that OFDM works with closely spaced subcarriers with orthogonal frequency. Each subcarrier gets modulated with a ...
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1answer
67 views

Spread spectrum

Are Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Sequence (DSSS) modulations? I am confused because I have read that these are also used e.g. with Gaussian Frequency-Shift ...
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2answers
49 views

What is the required bandwidth for QAM modulation?

Why is the allocated bandwith smaller with QAM-16 or 64 compared to e.g. QAM-4? I am not a professional so I'm looking for an intuitive explanation.
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1answer
31 views

Calculating Data rate function of bandwidth and SNR

I plotted BER vs SNR for BPSK modulation in Matlab and I am given bandwidth of channel (bandlimited channel). lets say it is BW1. I would like to find the data rate based on this information. I am ...
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1answer
41 views

Channel Coding with Higher modulation

Just had a theoretical question. I'm reading a book on LTE, and I came across an introductory section that talks about using higher modulation with channel coding. I understand that usually using ...
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1answer
61 views

Estimate the bandwidth required to transmit 1Mbits/s of data using a modulation scheme which comprises 32 different frequencies and 2 amplitude levels

Estimate the bandwidth required to transmit 1Mbits/s of data using a modulation scheme which comprises 32 different frequencies and 2 amplitude levels Yes, this is a homework question that ive been ...
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2answers
74 views

Drive electo-optic modulators with FPGA

I am currently using an FPGA (Virtex II NI RIO7831R) to generate the clock for a pulse generator used to drive a Linbo3 optical phase modulator. ...
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1answer
35 views

How to identify when a pulsed rf supply is active

I have a signal that consists of a 13MHz RF signal inside a pulse envelope (around 100ms on, 300ms off). I want to convert this to a 0-5V pulse that will just tell me when the primary RF signal is ...
3
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5answers
562 views

Transmission of a digital signal over a medium

A digital signal is said to have a infinite bandwidth. If a transmission medium cannot have infinite bandwidth then how can a digital signal be transmitted over such mediums? Please correct me if I ...
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3answers
115 views

An alternative way to make a VCO?

from what I am able to understand, a voltage controlled oscillator is "controlled by a voltage" when this voltage is applied to vary the value of the tank circuit: eg this could happen by applying ...
0
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2answers
68 views

How to calculate the RMS of an AC PWM?

I am looking at a servo, which is driven by PWM. The PWM signal itself modulates NOT DC but a sine AC, so when Throttle is set to 100%, I can see a rather nicely drawn sine wave. But when Throttle is ...
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1answer
33 views

Amplitude modulation transmission distortion

I need to clarify a question. Let's say that in a wire I carry a current modulated in time so that it is an amplitude modulation of a sinusoidal carrier with a modulating sinusoidal wave. In frequency ...
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5answers
129 views

Does increasing the amplitude of a signal also increase the data rate?

I face an ambiguity when considering the carrier frequency, signal frequency, bandwidth and data rate. When I consider the Shannon formula, I wonder if increasing the transmission power also means ...
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1answer
21 views

A question related to “quadrature carrier multiplexing”

While studying 'Qaudrature carrier multiplexing', I came across these statements in my text material: "Precisely varying the phase of a high-frequency carrier sine wave in a hardware circuit ...
2
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1answer
64 views

Working of ring modulator

I am having trouble understanding how this ring modulator works i.e. how it multiplies the input & carrier to give us appropriate output? Any help or guide will bedeeply appreciated. Reference - ...
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1answer
54 views

In Analog to Analog conversion , why we multiply instead of adding?

When we use AM i.e Amplitude Modulation , we multiply the source signal with the carrier , My Question is , why don't we add the signals ? it would be easier to modulate and demodulate I think.
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0answers
37 views

How to prove FM is superior to PM for tone modulation for a given signal?

How to verify that for tone modulation FM is superior to PM for the signal x(t) where \$ x(t)= 8cos(\omega_0 t) + cos(5\omega_0 t) \$?
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1answer
64 views

Emulating greyscale on a 1-bit LCD

I have an LCD (the DOG-M 102x64, with a uc1701 controller) that I am driving (over SPI, but that's somewhat irrelevant) from an AVR (ATMega16 @ 8 MHz) - all in all, a fairly low spec'd screen with a ...
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1answer
106 views

How to shift signal to baseband using local oscillator frequency?

If the input to a demodulator is a signal having the spectrum shown below, how would I figure out what local oscillator frequency is required to shift the signal to baseband? Is there a formula for ...
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0answers
15 views

MU-LAW COMPANDER for a 10-bit Quantzer … ? how many level will be needed to represent the lowest 30% of the signal for U=0 and U=10

for a 10-bit Quantzer how many level will be needed to represent the lowest 30% of the signal for U=0 and U=10 ? I know it it is u=0(simply no compression) so # of level = 0.3(2^10) which is = 307.2 ...
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2answers
109 views

Space vector PWM signals

I have done few BLDC motor controllers with trapezoidal modulation and they work fine. Now i'm trying to build another one with space vector modulation but as it doesn't work well i'm getting more and ...
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1answer
67 views

Can I hard wire an IR remote directly into the receiver?

I have a IR remote control and a clock (which it is designed to control.) I would like to remove the IR LED from the remote and the sensor from the clock, and run a wire between the two (so the clock ...
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1answer
150 views

38 kHz signal arduino demodulation

I need to demodulate signal with frequency 38 kHz coming from remote controller without IR receiver. I need to demodulate it and as a result get information from it. Is there any examples of similar ...
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0answers
64 views

High voltage, low current switching

I am using a high voltage low power integrated circuit (tracopower). I need to siwtch the output with a square wave signal up to 500 Hz. The problem is high voltage transistors also work with high ...
2
votes
1answer
100 views

Radar - How to keep IF constant?

A basic block diagram for FMCW radar I will be using, modified MIT radar project: MIT block diagram I My transmit frequency is 2200-2600 MHz, my receive frequency is ~2200-2600. I want my IF ...
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1answer
41 views

Analog modulation trainer

i am making communication trainer as my FYP i am confused on analog communication module .. I have 2 options first one to make different blocks of analog like mixers, filters , amplifiers ,phase ...
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1answer
77 views

Appropriate use of the word “modulated”

I don't use the word "modulated" very much and I would like to make sure I use it correctly. The TSSP77038 IR receiver module is a device that detects infrared light turning on and off quickly at a ...
0
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1answer
200 views

Implementation of PSK modulation/demodulation

I want to implement a BPSK modulation/demodulation using a microcontroller (Arduino Due). The carrier signal should be at 1-50 MHz and the information rate at 300 KHz. For the sender part I would ...
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0answers
38 views

Implement Automatic Gain control for 16 QAM

How can I implement an automatic gain control for 16 QAM modulation in Matlab preferably without channel estimation (trial and error may be).
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1answer
69 views

Why is there a guard band in ADSL

I recently learned about ADSL and its modulation method DMT. I know the frequency spectrum is split up into a number of orthoganally spaced bins: Voice(PSTN) - Guard Band - Upstream - Downstream ...
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1answer
67 views

FM signal example

Sorry if this question is too basic, but I'm a software engineer student who must study communication systems. I try to represent a FM signal in a graphing calculator, but I don't know why the result ...
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1answer
103 views

Amplitude Modulation Frequency

In am receivers, we detect the modulating signal by using envelope detector. So, the diode rectifies the signal, and the detected signal has doubled frequency than the original. Does this mean we will ...
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0answers
77 views

Minimum Shift Keying (In-phase, Quadrature Components derivation)

In the derivation of the minimum shift keying in-phase and quadrature components in Simon-Haykin Communication Systems 4th ed (p.387-390) we start off with the definition of the signal to be \$\ s(t) ...
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0answers
42 views

Bandwidth of a 1,2kbit GFSK and a 9,6kbit GFSK

I want to calculate the bandwidth of a GFSK modulation. In the task are two bitrates given, 1,2kbit and 9,6kbit, and the CC1200 (from Texas Instruments) transceiver is used for the transmission. I ...
0
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1answer
125 views

Maximum signal data rate

I have a frequency signal range from 25 Khz to 35 Khz. I know that the the minimum signal sampling to assure reconstruction of the signal from the samples is 70 Khz. Would it be correct to assume ...
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2answers
66 views

Which characteristics of a Radio signal are involved to be selected by radio receiver? [duplicate]

the radio antennas receives millions of signals. how our radio selects the appropriate signal as it's input? which characteristics of the signal are involved for this selection.
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0answers
86 views

Amplitude modulation circuit explanation

I am currently doing an amplitude modulation experiment and I am using the following circuit: I need to know the effect of the various components regards to amplitude modulation. And also what is ...
10
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2answers
646 views

How does the plastic-tube inductor in this wireless transmitter work?

This single layer PCB (solder side shown here) is from an old fan remote: The inductor in the plastic tube is not connected physically to any components; however, the two loops of wire surrounding ...
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1answer
266 views

Power efficiency of SSB-Large carrier

i was studying SSB demodulation and learned that a local carrier is added to the SSB signal to make sure that envelope detection is possible. I came across a problem to find the percentage of power ...
0
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2answers
51 views

frequency modulation and incoming signal selection

I have some understanding of what frequency modulation entails - it entails "adding" a new frequency to the frequency spectrum of a signal. But how, exactly, is a modulated signal selected in the ...
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2answers
229 views

How does this AM Modulator work?

I have been given a question and tasked with identifying the various components. However, this circuit doesn't really seem to make sense to me. Error: RC RE inverted simulate this circuit ...
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0answers
46 views

QAM-modulation-how-data-in-different-frequencies-are-laid-out

Monday 27th October 2014 Q.A.M Animation (URL QAM modulation - how data in different frequencies are laid out?) Can you please explain the two instrument icons at the left hand side of the ...
2
votes
1answer
218 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 ...
2
votes
1answer
84 views

How is CPM Modulation Different from PSK?

Continuous phase modulation has been described to me very similar to wikipedia's definition, which basically indicated that the CPM is different from QPSK, for example, because QPSK abruptly shifts ...
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2answers
136 views

How does an AM-modulated signal sound like in a speaker?

Let us compare two signals: one is a normal sinusoidal signal with single frequency 5khz with 1V amplitude (2V peak-to-peak). The other signal has a carrier frequency of 5khz and 2V peak-to-peak, but ...