Questions tagged [pll]

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symbol synchronization

PLL is typically used in carrier synchronization and its diagram is well known, consisting of a multiplier, a low pass filter, and a VCO. In "Phase-locked Loop" at wiki (https://en.wikipedia.org/wiki/...
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Instantaneous frequency, PLLs, frequency mixing, cross-correlation and the cross-correlation matrix

This is as much a request for comment and critique as anything else. I am looking at tracking how a system perturbs an input that is a (real) sinoid of varying frequency. ...
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2nd Order Type 2 PLL for Tracking Frequency Error

This is a "DSP Puzzle", Please preface your answer with spoiler notation by typing the following two characters first ">!" as the intention is for readers to think through what the solution might be ...
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34 views

Help on understanding Gardner's original paper for QPSK symbol timing recovery?

I am fairly new to DSP and RF receivers in general, and I was recommended to read Gardner's original paper for symbol timing error recovery for QPSK signals. I have a question regarding an equation ...
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1answer
84 views

Carrier Tracking Loop: Tracking noise vs Phase Noise Trade-off

I would like to compare two different implementations of carrier tracking loop which differ in the way phase detection happens in the PLL. I am using PSK modulation for the data. In the first ...
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1answer
12 views

Converting PLL Discriminator into Doppler error

I'm writing a GPS receiver SDR software, and I have calculated the PLL discriminator ouptut as atan(Q_Prompt,I_Prompt) I would like to know the formula that converts the discrminator output to doppler ...
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1answer
95 views

PLL for Phase Demodulation and Carrier Tracking

I've been playing around with using a PLL for phase demodulation and it's working pretty well. The PLL locks to the carrier and the error term is the demodulated message signal. However, depending on ...
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74 views

Phase difference calculation for non divisible sample rate to frequency

I am learning DSP and I am trying to simulate a simple phase difference calculator between two sinusoidal signals using GNU radio. My flowchart looks like this: As can be seen on the chart, one of ...
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2answers
66 views

Help find the bug in my SPLL code

In an attempt to get myself up to speed with PLLs I'm trying to implement Example 1 from this tutorial, in Python: https://wirelesspi.com/phase-locked-loop-pll-in-a-software-defined-radio-sdr/ (search ...
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162 views

realtime software 90 degree phase shift a sinusoidal signal

I would post this to stack overflow but it seems to me more like a signals and systems problem, which EE's thrive on. I need a realtime system implemented in software that can generate a sinusoid ...
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1answer
36 views

Non-coherent discriminator

I'm reading a paper about designing a non coherent discriminator for GNSS receiver. I came to the equation I'm not sure about that symbol < how would I write this in a small pseudocode ? for ...
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59 views

PLL in Tracking for GNSS behaviour

I'm doing work on SDR for GNSS and I'm tracking the signals I/Q using PLL. The calculations for the PLL is done like the following for error estimation: ...
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1answer
43 views

Relation between frequency and phase in PLL?

Apparently both frequency and phase are independent properties but what is the relation between frequency and phase in PLL?so that when one is locked ,other is also locked
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2answers
82 views

Digital PLL loses lock every time mesage crosses zero

I think my digital PLL is almost ready, but I've encountered this problem and I don't know what might be causing it, so I'd appreciate if you could help. I'm using the DPLL in a Costas loop. It seems ...
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77 views

How to correct phase using arctangent as Phase Detector

I have a DPLL that's trying to lock to a DSB-SC input signal with a carrier whose phase is $\theta$. So after some mixing and filtering (Costas Loop), I have these two signals ($\hat{\theta}$ is the ...
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Problem with 1st order PLL update equation

The output of a communication channel is given by: $x(t) = \sum_n{a_n}h(t-nT)$, where $\{a_n\}$ are BPSK symbols, $h(t)$ is the channel response, and $T$ is the symbol period. If there is an ...
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103 views

NCO loses lock after a while for certain values of alpha

EDIT: So the transfer function for my system is $$ F_{nco}(z)=\beta E(z)/(z-1)$$ $$ z\Theta_{nco} (z)=\Theta_{nco} (z)+\alpha E(z)+\beta E(z)/(z-1)$$ So I would like to obtain $\Theta_{nco} (z) / \...
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Worst-case error bounds for PLL

I am working on a project that involves time synchronization and we want to derive worst case bounds for the accuracy of the current time given measurements with known error as input. Unfortunately ...
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187 views

SRF-PLL discretization problem

So I've been working on how to digitally implement a static reference frame PLL (SRF-PLL), which is a quite popular PLL used for extracting three-phase grid angle. This PLL works by using the DQ0 ...
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27 views

The mean value of phase noise as a stochastic process

What is the mean value of phase noise as a stochastic process? Where can I get a theoretical analysis of this topic? PS: PLL produces cos(2*πfct+φ(t)). The phase noise refers to φ(t). The mean value ...
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PLL carrier recovery: intermediate versus baseband

When looking at carrier recovery, a PLL is often applied to correct the frequency offset between the local oscillator and the transmitter after down conversion. I'm wondering what happens to the PLL ...
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168 views

How does a Costas Loop lock to one of multiple BPSK signals

I've been looking into how GPS receivers work in terms of signal processing. When a GPS receiver tracks the received signal, it often uses a Costas loop to synchronize the carrier. How that works ...
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1answer
644 views

Residual carrier tracking with PLL

Residual carrier systems such as PCM/PM/NRZ and PCM/PM/Bi-phase are common in space applications. Compared to suppressed-carrier systems such as BPSK, the literature sources on residual-carrier ...
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475 views

GNU Radio loop bandwidth normalization

From GNU Radio documentation, the control_loop block proposes loop bandwidth values in the range $[\frac{2\pi}{200}, \frac{2\pi}{100}]$ in radians per sample. Some blocks, like the new timing symbol ...
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1answer
117 views

upconverting a kHz/MHz signal to GHz

I want to know how in practice we can take a kHz/MHz signal to a GHz band? Suppose we have an FSK modulated signal at around 300 kHz (or 20 MHz). I want to take it to 3.5 GHz, so about 3499700 kHz ...
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1answer
253 views

Basic PLL theory: voltage-controlled oscillator confusion

I am trying to write my first PLL in Python, and I've been making use of this excellent tutorial: http://www.pythonpowerelectronics.com/contents/tutorials/tutorial1/pll_tutorial.pdf Reading through ...
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Dynamic loop bandwidth for a Costas loop

I'm using a Costas loop for carrier recovery. The BER vs SNR (from GNU Radio Simulation) curve for different loop bandwidths (0.03,0.05 and 0.07) is shown in the graph below. It can be seen that the ...
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2answers
418 views

Software PLL tracking of carrier frequency in bandlimited transmission

My understanding is that a PLL(either in hardware or software) can recover the carrier frequency(or be used to correct the frequency offset) of a system. My question is how does this work when the ...
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1answer
737 views

Timing recovery in GNU Radio : Variable rate vs Fixed rate operation

I have been wondering about the implementation of timing recovery blocks in gnuradio. In literature, for asynchronous sampling, all that is needed are error detector (MM, ML, Gardner etc), a loop ...
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708 views

Carrier recovery with the Costas loop : PLL pull-in range

I have created a channel model in GNU Radio (a modified version of the default GNU Radio Channel Block). Its performance under AWGN (without timing, phase or frequency offsets) aligns properly with ...
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1answer
965 views

PLL phase and frequency characteristics

I'm currently working with BPSK carrier phase and frequency recovery in GNU Radio. I have been able to use Costas loop and Frequency locked loop (four carrier acquisition) which are based on the ...
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2answers
306 views

Phase ambiguity in QAM modulation

I'm currently studying a decision directed carrier recovery scheme. Basically a PLL try to estimate the phase error in the current received symbol, the phase detector compensate the incoming symbol's ...
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1answer
304 views

Is Phase Locked Loop is essential for BPSK signal reception?

I'm noob in DSP studying BPSK communication between speaker and microphone using acoustic signal. I read article of this BPSK communication which says it needs Phase Locked Loop(PLL) sequence to match ...
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1answer
248 views

Transfer function of a PLL Loop Filter that can support a linearly increasing (chirping) frequency

What is a transfer function for a the loop filter of a PLL that can track a sinusoid of the form: \begin{equation} x(t)=\cos\left(2\pi\left(\frac{1}{2}c_0t^2 + f_0t + \phi_0\right)\right) \end{...
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Unable to stabilize 8-PSK signal with self designed costas loop

I am trying to make a signal processing block which implements the costas loop to stabilize an 8-PSK signal. Here is the flowgraph with "costas_loop" being my block. My workflow is the following - <...
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1answer
4k views

How to correct the phase offset for QPSK I-Q data

I have an I-Q data of QPSK modulation, the data is is smeared and I have to correct the phase offset that causes the smearing problem, how can I apply the Phased-locked loop or the Costas loop on this ...
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365 views

Symbol timing recovery design

I am trying to design the Symbol timing recovery(#STR) block of #DVBS Receiver. These are the specifications Symbol rate ($f_s$) = $2\textrm{ MHz}$ Acquisition range = $10\%$ of Symbol rate ...
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2answers
1k views

How to remove 50 Hz frequency noise from a PCM file?

Are you kind to tell me the odds or the means by which should I grab a clean signal with the $~50 \mathrm{Hz}$ hum removed using just programming? I managed to make a program in Visual-C that ...
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265 views

Amplitude/phase recovery on noisy signal

I have a noisy signal that has an ac component of fixed frequency but variable amplitude and phase. I'd like to recover the ac component. The signal (blue trace) is mostly smooth, but has a few ...
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107 views

phase locked loop

I have seen that to get the phase angle of a signal, we have to use PLLs. this PLL is modeling in order to get the phase angle about one frequency, which is the free running frequency of the VCO. If ...
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280 views

FM demodulation amplifier with saturation

I'm trying to understand how FM demodulation works. I read a lot on the internet and as far as I understand, the main process is to extract the phase difference (that is also the output) between a ...
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1k views

PLL and zero crossing detection

Is there an algorithm which can give the frequency and phase of a three phase signal (three phase voltages) without using zero crossing detection. I mean an algorithm which is done in open loop.
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205 views

Software implemented PLLs for signal synchronization, why use them?

In short I'm recreating a program that reads 3 sinusoidal signals through an ADC performs some manipulations and then reproduces these signals through a DAC. In order to reproduce these signals I need ...
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1answer
268 views

Why do most digital pll's only use the positive zero crossing?

I've been trying to get my head around digital plls from knowing nothing and seen that most examples only use the positive zero crossing, not the negative. I've tried to find the answer but the best i ...
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2answers
2k views

High modulation index PSK - carrier recovery

How to recover the carrier of a PSK signal that has high modulation index (eg. 750 symbols per second at carrier frequency 1500 Hz)? I guess that a PLL will not be able to lock onto it with such ...
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560 views

Doppler shift using PLL

I am trying to apply phase lock loop to calculate phase shift due to doppler effect and finally calculate the doppler frequency($\Delta f$). I am assuming that the received wave is of the form, $r(t) =...
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2answers
275 views

Melodic or tonal pitch contour tracking?

What algorithms or methods can be used for the tracking of audio pitch contours? (Such as in musical vibrato and glissando, or for tonal vowels in languages such as Chinese?). Will a PLL work even ...
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Phase Locked Loop Basics

I am trying to better understand discrete-time PLLs. I drew a picture of a simple feedback system here: I want to be able to describe and understand the system at v(t) and y(t). I found a fairly good ...