# Questions tagged [quadrature]

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### Do all phase quadrature signals form orthogonal pairs with their in-phase versions

I have been studying analog modulation, in that i found a concept of quadrature carrier multiplexing which says that two baseband signals with possibly different bandwidths can be modulated to occupy ...
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1 vote
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### Analog FM & IQ modulation

I am exploring the possibilities of IQ modulator. I want to do analog FM modulation (range $0$ to $5 ~ kHz$) using IQ modulator. So far, I can modulate the signal digitally inside of the STM32 ...
• 11
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### Plotting Constellation Diagrams

I'm working with some IQ data from the paper A Wideband Signal Recognition Dataset. Specifcally I've been trying to plot the constellation diagram for some the modulations within the dataset, however, ...
108 views

### MSK without I/Q data

I just started a while ago with DSP and slowly staring to understand the concept of I/Q and what it means. I successfully could decode some bfsk, bpsk and wanted to move to msk which as not easy to ...
• 5
124 views

### Error in complex signal with imperfect quadrature phase and amplitude (textbook question)

I am working on the following problem: I have a solution that I am pretty confident is correct as have checked the output in python. However, it is long and the entire time I was answering the ...
• 245
1 vote
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### Amplitude modulation in SDR [closed]

I understand the theory of amplitude modulation. However, I couldn't understand it's implementation in SDR, which use IQ data, and I would like to learn end to end amplitude modulation system in ...
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### Is the phase of a IQ point related to the local oscillator frequency?

When considering a direct conversion SDR receiving or emitting architecture, we can "represent" the received or transmitted signal as the sum of two components, the I and Q component. Each ...
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487 views

### What tricks can one play on a bandwidth-limited IQ modulator?

I would like to create a pulsed RF signal that has a carrier frequency of 2 GHz by IQ up-conversion. The pulse should be 2-4 ns long. The carrier phase has to jump by 90° in the centre of the pulse. ...
• 193
534 views

### How does the quadrature sampling lower the sampling rate?

According to this tutorial, by exploiting quadrature sampling with IQ signals, we then have the benefit that each ADC operates at half the sampling rate of standard real-signal sampling (This ...
• 155
1 vote
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### How are discontinuities in quadrature modulated signal QAM physically produced?

In quadrature modulated signals, for instance: I am unclear how the "discontinuities" in the waveform at the junction of each data point can be physically produced? Taking a speaker as an ...
• 113
1 vote
58 views

### Doubt on Signal Processing Step

I am using a Radar Sensor. So applying Signal Processing on the Radar Sensor Data. PrevSample and PastSample are Radar IQ samples for a present and previous Sweep detecting tiny movement. In the ...
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### Interpolating Filter for Quadrature Detector with one ADC

Single ADC is sampling at 16000 Hz the I and Q outputs of quadrature detector. So each I and Q signal is sampled at 8000 Hz, with phase offset 90 degrees between them. Bandwidth of interest is 3400 Hz....
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### Quadrature Detector with a single ADC

I have a quadrature detector, which provides I and Q baseband signals with 4 kHz bandwidth, set by detector's LPF. I digitiize them on two ADCs with sampling frequency 48 kHz, make Hilbert ...
• 27
329 views

### Performing IQ imbalance correction on sampled quadrature signals

What are the techniques which can be used to perform digital IQ amplitude and phase correction in a wideband receiver system when input signals can be of unknown different frequencies and occupy ...
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### How to test I/Q modulation with only one branch (I or Q)?

Given is a direct-conversion I/Q up- and downconverter system. Receiver and transmitter share the same (10MHz) reference and hence the LO frequency is identical and there is an (unknown) phase ...
• 473
814 views

### Quadrature demodulation, homodyne detection, lock-in detection - what's the difference?

Quadrature demodulation Homodyne detection Lock-in detection What is the difference between these terms? Are they all synonomous? In my mind they kind of are, so I'm never sure which to use. I ...
• 241
2k views

### What techniques are available for correcting constellation rotation due to phase ambiguity?

In order for a receiver to recover a baseband signal, it needs a carrier signal equivalent to that used by the transmitter for upconverting the original baseband signal. Unless pilot tones are used, a ...
• 143
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