Questions tagged [quadrature]
The quadrature tag has no usage guidance.
91 questions
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Detecting I/Q imbalance
Are there any methods of detecting, measuring, and/or estimating I/Q imbalance (from, say, an upstream quadrature mixer and/or ADC), without using or having a controlled test signal (other than ...
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Modeling channel response as complex vs splitting I and Q
If I have a communications channel where a digital QAM signal is transmitted, I can either model the channel's impulse response as a complex $h(t)$, or as 2 separate impulse responses $p(t)$ and $q(t)$...
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Removing I/Q phase rotation
What is the most reliable and agnostic way to correct for a phase rotation of I/Q downconversion - without time alignment of the signal and support different lengths of transmitted and received data?
...
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How to eliminate negative frequencies from IQ signal
I have a 192kHz IQ signal from an RF receiver, and i'm trying to remove signals in the negative (or positive) frequency spectrum.
I see that the negative frequency signals are -90 degrees phase ...
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Are IQ-samples independent from the carrier frequency?
Since i am not sure if i have understood IQ samples correctly, i want to ask the following question:
If i look at inphase and quadrature in an IQ diagramme, the length of the arrow describes the ...
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In-Phase and Quadrature components of low-pass equivalent of a band-pass signal?
I was wondering what is the physical meaning of IN-PHASE and QUADRATURE components?
In the context of low-pass equivalent of band-pass signals.
Any help is appreciated!
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How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)
I've spent many hours reading and doing research about this. I don't attend any university classes or any type of classes that may approach such a topic. I am trying to learn this by my own without ...
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Sending complex signal over a single wire
The G.hn protocol uses OFDM to transmit data. And it sounds like they are doing it on a single wire. OFDM symbols are a complex number with I and Q components. How are they able to send two separate ...
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Recover IQ samples from signal
I have a data acquisition device that provides me with an array of integers that represents a modulated signal (let's say QAM16).
I would like to recover the I and Q samples from the raw time-domain ...
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Complex bandpass filter giving quadrature signal
I have found a technique detailed on page 34 & 35 of this thesis.
In this, the author states a complex bandpass filter can be derived by first making a prototype real valued IIR filter, then ...
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Why is no phase information lost when a received signal goes through a mixer?
I'm sorry if the question is too philosophical or makes no sense, but I need to be able to explain why it doesn't make sense.
When we take the in-phase and quadrature-phase base-band components of an ...
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How to "draw" the function/wave to send symbols using QAM?
Say you have the following 8QAM constellation diagram:
Say, you want to send the sequence:
001 110 101 000 001
How would you draw the function/wave containing the symbols?
My problem in ...
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How do you compute for fc and t in modulating an I and Q component
I know that in a $2^b$-ary QAM system you need to modulate the $I$ and $Q$ components through the mixer and are separated by 90° through a local oscillator (by applying a $\cos$ and $\sin$).
By ...
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IQ FM Demodulation of Wow and Flutter Signal in Software
Background:
I have a recording device that exhibits Wow and Flutter, or periodic frequency deviation. I use this device to record a calibrated 3.15kHz test tone from a tape film to generate a .wav ...
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Maximum Throughput of QAM system
Consider a QAM system designed to transmit over a bandwidth of $3 \ \mathrm{kHz}$. The channel's power constraint imposes a maximum $\mathrm{SNR}$ of $30 \ \mathrm{dB}$. The system can tolerate a ...
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QAM-spectrum with uneven real & non-odd imaginary part
Despite the signal being real, as is seen in the last line of the first picture:
, the exemplary spectrum of the signal shows neither an even real nor an odd imaginary part:
But from my theorems I ...
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Why do SDR receivers emit I/Q samples?
To my understanding hardware receivers for software-defined radio applications basically take the input signal, mix it with the tuning frequency to remove the carrier frequency and then sample the ...
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What type of information can be contained in I/Q (quadrature) data?
I am taking in regards to, for example, the signals captured using a measuring instrument such as a spectrum analyzer. Basically would the I/Q data store all the parameters that my analyzer can ...
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FSK and IQ modulation
I am having trouble understanding the FSK modulation process. There are many ways of demodulating the FSK signal.
What is the advantage of performing the FSK using IQ modulation?
How to demodulate ...
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Quadrature modulation for FM and AM
This might be a naïve question, are these correct statements?
Both amplitude and frequency modulated radio signals nowadays use quadrature modulation and demodulation as a mean to transfer and ...
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How to reconstruct RF signal using IQ data
I have a complex IQ signal: $s = X + Yi$. I know my original $f_0$ was $5\textrm{ MHz}$.
I can calculate the magnitude/amplitude of $s$: $A = \sqrt{X^2 + Y^2}$
and phase, $\phi = \arctan\left(\frac ...
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What is the advantage of measuring IQ data non-digitally?
So I know In-phase and Quadrature (IQ) data can be used to analyze changes in both phase and amplitude of the signal. I also know that if I know the I component of the signal (which I could get by ...
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Generating QPSK Constellation Diagram
I was wondering how a diagram like this is generated.
I am generating a QPSK signal using MATLAB by taking a cos and sin wave, multiplying each one by either 1 or -1 and adding them together to form ...
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Play IQ data in the soundcard
I have short-wave digital receiver that send RP packets with IQ components over network depend of the RF frequency and passband. I need to work with the telephone passband (0.3 - 3.4 kHz). The task is:...
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Root raised cosine pulse shaping peak value
I am using a FIR filter to generate Root Raised Cosine pulse for an IQ modulator.
How can I predict the peak value at the output, depending on the roll-off factor of the pulse ?
Knowing that :
FIR ...
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IQ imbalance amplitude
I have to fix the amplitude of measured IQ receiver data. According to my information about the data, I can estimate that one signal needs to be corrected to the other in amplitude. The phase offset/...
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Doing analysis using IQ demodulation in Python
I'm trying to doing an analysis using IQ demodulation. I'm doing this by taking a noisy signal which has a desired signal in it. The desired signal has a frequency that is almost stable, which I'm ...
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Addition of two signals in polar coordinates
There is quadrature detector which receive radio signal and return its amplitude and instantaneous phase after performing hilbert transformation and transferring the signal to zero frequency. The main ...
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Reconstruction of BandPass Signal from Complex Envelope
From what little I've been able to gather, the complex envelope preserves all information required for the reconstruction of the original signal and that it basically sends a low pass version of a ...
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Quadrature modulation
I have a question:
What is the difference between
$ I \cos(t) - Q \sin(t) $ and $ I \cos(t) + Q \sin(t) $
except that they are phase shifted 90 degrees ?
On the internet I can find both ...
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Difference between these two digital down conversion methods
I can think of two possible methods of digital down conversion. One seems superior to the the other for most cases, but I'd like to get some DSP experts' comments on the practical differences between ...
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What is the connection between analog signal to noise ratio and signal to noise ratio in the IQ plane in a quadrature demodulation system?
We would like to compute the quantitative relation between analog noise near the LO frequency and the statistics of points found in the IQ plane after IQ demodulation.
In order to completely ...
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Spectral density of signal written as quadratures
Suppose I have a real-valued random signal $f(t)$ written as
$$f(t) = I(t)\cos(\Omega t) - Q(t)\sin(\Omega t)\, .$$
What is the relationship between the spectral densities of $I$ and $Q$ and the ...
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IQ imbalance on quadrature signal
Hi I am attempting to develop a reasonable IQ balance mechanism for a quadrature signal coming from a software defined radio.I can balance out the amplitude and phase differences at one frequency ...
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Quadrature subsampling result not as expected
Let's suppose I have an ADC running at 81.824MHz. I am quadrature subsampling a signal that is at 143.5MHz using a sampling rate of 81.824MHz/4 = 20.456MHz = Fs. I expect the signal to appear at ...
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Splitting a Complex FIR Filter into Real Filters
I'm working on a software defined radio project on a PIC32 MCU. I'm using a CMX 973 quadrature frontend to provide I and Q. I'm independently low passing I and Q with carefully matched analog filters ...
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Software defined radio panadapter
I am trying to make a panadapter for a software defined radio and I am a little bit stuck and hope someone can help me.
I have an I Q signal from my radio. (Actually I am using an IQ wav file from ...
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How to get the quaternionic analytic signal of a image?
The 2D discrete image signal's quaternionic fourier transform can be described as F(u,v), and its 2D analytic signal often be described as:
$$
F_q(u,v) = (1 + \mbox{sgn}(u))(1 + \mbox{sgn}(v)) F(u,v) ...
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IIR biquad coefficients for negative frequencies in IQ data?
Assume I have a (single real float channel) biquad IIR filter implemented in C, and some coefficients for a bandpass filter (right out of RBJ's cookbook).
If I convert the input, output, data path, ...
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How do you alter the phase relationship between I and Q in a quadrature signal?
I am collection a quadrature signal from a radio. The I and Q signals go through a sound card at a sample rate of 192000, and then a FFT is performed on the signals.
Due to various reasons, the ...
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What exactly is a complex envelope?
I have seen this be mentioned a couple of times in some books I read, so I want to make sure. Is the complex envelope simply the summation of the real and quadrature components of a signal, whereby ...
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