Questions tagged [noise-spectral-density]

Anything related to the noise spectral density, i.e. the function representing how the power of the noise signal is distributed among its frequency components.

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26 views

Simulation of the injected noise to oscillator in Virtuoso

I have a differential LNA that injects current to an oscillator. I want to see the thermal noise injected to the oscillator. This noise is composed of the noise of oscillator + noise of the LNA. Now ...
261 views

What are the calculations to do in practice to estimate beforehand the noise seen on the output of this op amp circuit?

I would like help with understanding something better, but am not trained in electronics so please bear with me! I am trying to make a simple circuit to take a {-10V ... +10V} signal from a function ...
32 views

Total thermal noise of a photodetector connected to a spectrum analyzer

I connected a photodetector to a spectrum analyzer (SA) and observed the signal (i.e. noise) on the SA when there is no light hitting the detector. I noticed that when I set a low spectral resolution ...
50 views

Power spectral density on the output of frequency modulator?

Is there a formula with which we would be able to calculate the power spectral density on the output of a frequency modulator? The information we know is that we have a receiver working in 180MHz ...
71 views

Can we use both FFT and PSD to obtain a random signal's frequency domain representation?

I always encounter random noise frequency domain representation as PSD(not FFT), something like in the below plot: Without diving into math too much, practically speaking can we always use FFT ...
43 views

Phase noise of a digital PLL

I assume the reader is aware of how a DPLL works. The DPLL oscillates with a frequency of $F_{out}$. The DCO free running frequency is $F_{free}$. In the model of our DPLL we've only considered ...
27 views

How does spectral density of a power signal change when it is multiplied by $cos(2\pi f_ct)$?

Suppose we have a power signal $n(t)$ whose power- auto-correlation function is: $R_{n}(\tau)$ . Now we multiply the signal by a cosine as: $cos(2\pi f_ct) \cdot n(t)$, whose auto-correlation is ...
52 views

How does one calculate output voltage noise of a current output DAC?

I am using a current output DAC connected to a voltage reference and a transimpedance amplifier. I know the noise characteristics of the voltage reference and the amplifier. The DAC simply lists "13 ...
42 views

Does the profile of phase-noise power spectrum density (PSD) vary with time?

I will promptly provide any detail or revise my question aimed at any feedback. Does the profile of phase-noise power spectrum density (PSD) vary with time? The conclusion may be that it won’t ...
101 views

Johnson-Nyquist noise for a lossy inductor?

In searching the internet for thermal noise on an inductor and I'm not finding much on the basics for a real lossy inductor. I'm interested in thermal noise for a fixed inductor in a surface mount ...
62 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?
52 views

Noises of switching power supply

I made a switching power supply (input: 24VDC, output: +-15Vdc) for LEM (current sensor). Noises of the power supply caused the output of LEM to become a bad waveform, but I don't know how to ...
79 views

Maximum Allowable Noise of ADC Input Signal

I have a question about calculating the maximum allowable noise for an ADC signal conditioning stage. I have an existing signal conditioning stage as well as an ADC on a microcontroller. I would ...
53 views

Noise Spectral Density Standard

Is there an IEEE or other standard for how Noise Spectral Density is calculated? In particular, when they give a single figure (like $12.4\,\text{nV }/\sqrt{\text{Hz}}$) is that averaged over the ...
69 views

noise of high speed serial link

I have an ADC module. The board contains sensitive (10-100MHz) analogue parts and a high speed serial link (Aurora). The link uses scrambling algorithm, and I can choose the bit-rate. (I have much ...
168 views

$pV/\sqrt {Hz}$ in Power Spectral Density

I am trying to plot a Noise Spectral Density from 10 kHz to 1 MHz. The Graph shows a cure which at 1 MHz the noise is 76 pV/rootHz. I am unable to understand that unit definition here. Becuase the ...
66 views

Sampled Noise Amplitude

I am trying to understand how an arbitrary noise spectrum is sampled by an ADC. Let the broadband noise floor be, for example, $e_n$ = 5nV/√Hz @ 1kHz and the 1/f noise be $E_{1/f}$ = 2 μV peak-...
68 views

Conversion of Additive Noise to Phase Noise

RF Microelectronics by Razavi contains the following snippet in section 8.7.3 concerning the analysis of phase noise in oscillators: We write $x(t)=A\cos(\omega_0t)+n(t)$ where $n(t)$ denotes ...
626 views

How do I measure very low frequency noise?

I'd like to measure low-level noise in the 1 Hz to 100 kHz range, for example at the output of a LDO. For higher frequencies a spectrum analyzer would do the job, but most only go down to the MHz ...
68 views

Noise in Analog communication

A signal with PSD $S_x(\omega)$ is passed through a channel with frequency response $H_1(\omega)$ and at the receiver, it is passed through an equalizer with frequency response $H_2(\omega)$. ...
184 views

How may noise voltage and noise figure be compared?

For instance, comparing the MIC920 and the BGA2818, it's expected that since the latter is intended for application as an RF LNA and the former is general-purpose, the BGA2818 would out-perform the ...
292 views

Filtering capacitor only adds noise in a rail-splitter

Say I need to make a very low-noise signal inverting schematic. For that I came up with the schematic below - the U2 is a low-noise opamp in an inverting configuration, and the schematic around U1 is ...
92 views

Can I measure the voltage noise with True RMS function

I have a measurement setup with which I want to measure high voltages. Now I want to evaluate the noise this setup produces (preferably in V/sqrt(Hz)). I short circuited the input and I am now ...
411 views

1/f noise, is it limited?

Basically my question is: I doubt noise density goes to infinity because we can reach the limit f→0 in any DC circuit in contrast to the limit f→∞ (which is an idealization because all circuit ...
77 views

Unit in the exponent for phase modulation

How does the "unit" per Hertz in behave in the exponent? My specific question is about the calculation of the modulation index $\eta$ from a measured spectral density of a phase modulation on a ...
2k views

Converting Power Spectral Density to Power

I have a vector signal analyzer which is measuring an OFDM signal with a bandwidth of 20MHz. The spectrum shows "Power Spectral Density [dBm/RBW per 100kHz]" on the Y-axis. The RBW is set for 100kHz. ...
133 views

Allan std deviation : why do we need to read the values at specific sample times?

I am from the computer vision community, so I apologize if this sounds trivial. I'm trying to deduce the white noise and rate random walk for an IMU. Some sources recommend deducing those values by ...
38 views

Sinusoidal signal as density

I produce a magnetic field with a current source and a long cylindrical coil. A current of $\hat{x}$ (peak value) with frequency $f_{x}$ produces a magnetic field of $B$ (RMS value in Tesla) ...
128 views

Phase-modulated Noise

If you replace the carrier signal in a phase modulated circuit with noise then presumably the noise will be modulated. What must be considered if we wish to detect this noise modulation? I’ve ...
135 views

Ιnput referred noise of an amplifier

I have a problem with a low noise amplifier because I can't find in ADS(Advance design system) software how to integrating under the are of a measured curve in a specific frequency range.Can someone ...
2k views

Antiresonance of multiple parallel decoupling capacitors: use same value or multiple values?

My quesiton: Is it better practice to put same-valued capacitors in parallel of capacitors of different values to decouple the high-frequency noise caused by digital ICs? Background Digital IC need ...
2k views

Noise Model for Zener Diodes

I am trying to design a noise source using discrete transistors and a Zener diode in the avalanche breakdown region. Therefore, I have several questions relating to the use of the diode... How does ...
448 views

Current noise as spectral density from given RMS noise

I want to know the current spectral density of a Keithley 6221 current source. The datasheet above provides values in RMS for a given Bandwidth from $10~\text{Hz} - \text{BW}$, not clearly ...
791 views

Determining noise spectral density

I am working with a digital sensor (magnetometer) that can operate at multiple frequencies. The application note (http://www.st.com/resource/en/application_note/dm00136626.pdf) gives RMS noise values ...
2k views

Gyroscope Noise Density

I am trying to understand how to use the "Rate noise density" spec on a gyro IC. It is quoted at 0.25 degrees/second/root(Hertz). I plan on sampling it at about 100Hz. Is the noise going to be root(...
557 views

Why are there two sets of ENBW correction factors?

For calculating the equivalent noise bandwidth of a non-brickwall filter, I can find two different sets of numbers, both of which claim they are similar things: ...
379 views

Practical consequence of the noise spectral density

For a particular current transducer, http://www.digikey.com/catalog/en/partgroup/ho-p-sp33-series/49533, it states an "Output rms voltage noise (spectral density)" of 6.13 uV / sqrt{Hz}. If the ...
2k views

What is the noise level as read on my oscilloscope?

The above is what I'm seeing on my oscilloscope. It's zener diode noise. Scope's set for 0.5V/div vertically, and 1ms/div horizontally. The oscilloscope has a 20MHz bandwidth, but the noise doesn't ...
170 views

Noise Coupling methods to communication cables

I want to know how can I couple noise(practically) into a communication cable in order to analyze the data error rate of the communication. I hope by using transformer I can couple it, but I don't ...
1k views

Why the noise from cascode transistors are negligible at low frequencies?

I am reading about noise of cascode amplifier in Razavi book, Design of Analog CMOS Integrated Circuits. However, I couldn't understand the yellow highlighted sentence below. Could anyone explain it? ...
282 views

Noise in cascode opamp

Could anyone tell me how the noise current component in the red circle is calculated here? I believe the superposition method is used here but I can't figure out how to get the second component like ...
174 views

Why the mean squared value of a random noise signal at a single precise frequency is zero?

I am reading about noise from this lecture (page 9/31). However, I don't understand this point. Could anyone explain why mean squared value is zero? The mean squared value of a random noise signal ...
2k views

How to avoid Johnson noise in high input impedance amplifier

I don't have a circuit I'm working on, this is more of a theoretical question - I am trying to remedy a flaw in my understanding. Imagine I want to build a high input impedance amplifier to work in ...
418 views

Calculate noise spectral density

I want to analytically calculate the power spectral density (PSD) for noise at the input of the given circuit as a function of frequency. Both resistors cause noise, as well as the opamp itself, with ...
958 views

Explanation of sensor sensitivity in unit/hertz

i found an overview of different magnetic field sensors sensitivity in a paper. I was wondering why the sensitivity is given in units of T/Hertz^-1/2. Is it possible to determine the minimum ...
379 views

Amplitude of PSD on spectrum analyzer varies strongly with RBW

I have a question about the amplitude of my spectrum analyzer. I'm producing upconverted white noise over some bandwidth (say 150 MHz), in the 7 GHz range. In this sense everything is as expected; ...
90 views

Dropoff in white noise produced by AWG

I have a question regarding white noise generated by an arbitrary waveform generator (AWG). I'm working with one (AWG5014C) that has a sampling rate of 1.2 GSamples, with which I want to produce white ...
118 views

Power spectral density generated by AWG

I'm having trouble interpreting the results of my spectrum analyzer, concerning noise generated with an AWG. So, step 1. The AWG generates gaussian noise with mean 0 and variance A at a sampling rate ...