# Tagged Questions

Modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with the amplitude of low-frequence modulating signal which typically contains information to be transmitted.

21 views

### How to use phase codes for modulating a pulse

I am working on phase codes (examples - Frank, P1, P2, Zadoff Chu) to generate minimum side-lobes on matched filtering. I considered a sinosoidal carrier wave at $45\textrm{ mHz}$, and phase modulated ...
32 views

### ssbmod single sideband modulation artifacts

clc; clear all; close all; [c,fs]=audioread('60hz.wav') r=ssbmod(c,160, fs) r=r/max(max(abs(r))) audiowrite('artifacts.wav',r,fs,'BitsPerSample',24) I am trying ...
46 views

### Frequency modulation: Implementation and interpolation

Phase modulation is defined as: $$f_c(t+f_{m}(t))$$ That is the carrier $f_c(t)$ is shifted in time by an amount specified by the modulation function $f_m(t)$. To achieve frequency modulation simply ...
26 views

### Why does QAM use two cycles instead of one per byte?

If you look at this image, you can see that you have 256 possible binary values by modulating the amplitude (the radius of the trigonometric circle) and the phase (the degrees) of the carrier. ...
12 views

### Bandwidth of ofdm symbol in a visible light communication system

What is the difference of the bandwidth of the LED and the optical channel? If ofdm symbols are transmitted over this system, is the bandwidth of ofdm symbol equal to BW of the LED or of the channel.
48 views

### Gardner Timing Recovery for Repeated Sybmols

I am implementing the Gardner Timing Error Detection algorithm for a QPSK signal. I understand the concepts behind it but I am curious as to what effect repeated signals can have on the phase lock. ...
38 views

### Visible light communication and LED modulation

I work on a VLC system in which 16-PAM symbols with complex pilot symbols are as ifft input. I made the ifft output real and positive. Now how should i use these ofdm symbols to modulate LED? Their ...
44 views

### How to find a know signal in another signal which contains other signals along with the signal i need in python

I am working on BPSK with sound waves a carrier waves. Actually I am modulating my data with some known sync bits along with the information I need to send. So the things I will be having at ...
46 views

### The little problem with Kalman filter

I am trying to simulate the Kalman Filter. I have the covariance matrix P_{0|0}. Tell me please, how can I get the predicted (a priori) estimate covariance matrix ...
24 views

### why does the decision boundary change in BPSK? is it true?

I am working on modulation and demodulation of BPSK using python. i made a code for modulation and demodulation,while demodulate i tried to compare my actual data bit stream with demodulated bit ...
33 views

### How to derive the transmitted signal from a constellation diagram

Let us assume we have $16$ symbols to transmit. We can represent these $16$ symbols by $16$ unique signals and transmit. If at the receiver we can identify these $16$ signals correctly, we have ...
171 views

### FSK Demodulation, Bit Timing Recovery

I am currently implementing acoustic FSK modulation and demodulation. I am not a signal processing guy so any help about the bit timing recovery would be very appreciated. Currently I implemented the ...
56 views

### What is a $BT$ (Bandwidth-Time) product with reference to modulation?

I would like to know what does Bandwidth-Time product mean. I understand that Bandwidth ($B$) = 1/Symbol Time ($T$), hence $BT = 1$. But how can it vary? What is its significance? e.g. When we say ...
22 views

### Choosing modulation frequencies

A square wave $s(t)$ is modulated by two functions, $y_{1}(t) = \sin (2\pi f_{1}t)$ and $y_{2}(t) = \sin (2\pi f_{2}t)$, which are combined into a single function $x(t) = y_{1}(t)s(t) + y_{2}(t)s(t)$. ...
26 views

### How to calculate transmission capacity of a channel with multiple frequencies? [duplicate]

So I have the following question: If a transmission channel uses an analog carrier wave that is modulated by eight amplitudes and sixteen frequencies per bit time, then what is the ...
58 views

### How to set a Carrier Wave for DBPSK Modulators in gnuradio?

for a Project I need to build an Audio Modem in GNU Radio. I decided, that it would be the best to use DBPSK Modulation, because that is fast and relatively noise resistant. But as it seems, the ...
48 views

### M-Array DPSK decoding and encoding

So i'm trying to figure how how to do the encoding and decoding of an M-array Differential Phase Shift Keying (DPSK) signal. I understand how to do it for binary DPSK, but on higher ordered signals I'...
29 views

### Reasoning Behind Additional Phase Shift in DPSK

In MATLAB's Comm System Toolbox there is an option for 'Phase Rotation', defined as the phase difference between previous and current modulated symbols when the input is zero. This is the first time I'...
35 views

### how to sample and modulate a gps gold code

I am trying to simulate the data transmission of a GPS satellite. Telecommunications is not my field so I am struggling a bit with some concepts. I managed to generate the Gold code of the GPS ...
62 views

I am using an on-chip SAR adc where for some reason I can only get accurate signal reconstruction and filtering when I sample at almost 100 times my desired sampling frequency. Specifically, the ...
54 views

### Smoothing an LFO Sawtooth Wave

I'm trying to smooth a Sawtooth wave coming out of my LFO. Effectively the transition from 1.0 to -1.0 in a 1 sample step is causing clicks and pops if I modulate my audio signals amplitude with ...
19 views

### Reduction of Sample Size of a Gaussian Pulse

I need to sample a gaussian wave of pulse width of 1 us which is being modulated by a cosine wave of GHz frequency. The different cases that I am interested in are 1) The initial phase of the cosine ...
42 views

### IFFT-based OFDM system

Please explain, mathematically, how can a bank of modulators be replaced with the IFFT in an OFDM system?
87 views

### Audio frequency modulation algorithm

I have a digital audio signal (float samples). I need to apply the Vibrato effect to a signal. "Vibrato" is no common term, but it is the same as the frequency modulation. So, I need to modulate my ...