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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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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-...
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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 ...
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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 ...
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1answer
59 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)\$. ...
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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 ...
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123 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 ...
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45 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 ...
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56 views

Noise Power Spectral Density

So, I'm a physics student who threw himself into an electronics class with very little experience with circuits, amplifiers, and the like. So, please forgive me if my question is trivial or is totally ...
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261 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 ...
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1answer
66 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 ...
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3answers
641 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. ...
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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 ...
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1answer
36 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) ...
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56 views

Equivalent input noise temperature of LNA and passive attenuator

Just wanted to make sure I am doing it correctly. If I have an amplifier with equivalent noise temperature of 140K and gain of 30db connected to a 3dB attenuator at the amplifiers output. I need to ...
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1answer
98 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 ...
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1answer
106 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 ...
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4answers
1k 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 ...
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1answer
1k 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 ...
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2answers
231 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 ...
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1answer
505 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 ...
2
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1answer
878 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(...
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1answer
363 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: ...
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2answers
301 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 ...
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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 ...
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1answer
127 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 ...
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1answer
875 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? ...
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1answer
214 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 ...
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2answers
114 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 ...
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2answers
1k 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 ...
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0answers
288 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 ...
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1answer
632 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 ...
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0answers
275 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; ...
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1answer
70 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 ...
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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 ...
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1answer
263 views

Quantifying white noise with a spectrum analyzer

The setup of my problem is as follows. I have an experiment in which I want to apply a noisy voltage with a white (flat) spectral density over a large frequency range, say 0 to 7 GHz for example. Not ...
3
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1answer
176 views

How can any spectral analysis show that Sigma-Delta ADC reduces quantization noise?

Quantization noise refers to the modeling of the difference between an analog signal and its quantized version as an additive noise process. The power of the quantization noise can be calculated by ...
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1answer
293 views

Phase noise measurement with IQ mixer

I have a question regarding a measurement scheme of phase noise that I'm trying to implement. The idea is that I have two identical signal generators (I actually do) that generate a sinusoidal voltage ...
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1answer
83 views

Noise figure of a passive network at a temperature different from room temperature

Given a passive network at room temperature, the noise figure is the ratio between the output noise power density pw and and the output noise power density due to the source pwS F = pw/pwS = 0.5*k*T/...
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1answer
324 views

Definition of Phase Noise

I'm confused with the definition of phase noise. I'm referring to this IEEE document. A noisy oscillator output is \$v(t) = A\sin(\omega t + \phi)\$, where phi is random phase deviation. I assumed no ...
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1answer
184 views

Johnson noise with amplifier circuit

I need help with this problem. Some numerical answers would also be very helpful.
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1answer
342 views

Derive the Power Spectral Density of output process

Derive the Power Spectral Density of output process. This question is from undergraduate physics course. Please help! I do not even know where to begin!
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1answer
63 views

Noise when Charger Connected [closed]

I have a handheld rechargeable Measuring Instrument. When I use it normally, without charger connected, readings on screen are stable. But when I connect the charger into it (It's a 5V USB charger) ...
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1answer
75 views

Noise vs Signal

All, I have created a photo-diode amplifier(2 stage) which allows me to set a gain from 2 to 551 (v/v) [4.6 to ~55dB] in 64 steps. The gain is achieved using pre-calculated resistance to provide non-...
3
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1answer
1k views

How do I find spectral purity?

How is spectral purity measured? or evaluated? I have this signal coming from a 10 MHz crystal oscillator. I know how to calculate the SNR, but how do I calculate the spectral purity? Is it also a ...
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3answers
519 views

How to convert noise to noise density in mic pre amps

I am trying to compare two low noise mic pres for the lowest noise, and I am looking at the TI1012 and MAX9814 MAX9814: ♦ Low Input-Referred Noise Density of 30nV/√Hz TI1012: Output Voltage Noise (...
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3answers
89 views

Op amp noise specifications at DC

One thing I've never quite understood about noise specifications is what happens if your circuit uses DC only -- yet all specifications for noise make reference to a bandwidth. I have an ...
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1answer
798 views

Is this a true pink noise generator?

I found this neat circuit (page 18/62) but I don't understand it. This doesn't seem to be your usual white noise generator plus pink -3db/octave filter. Is this a true pink noise generator?
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2answers
2k views

AD620 voltage noise and ADC SNR calculation

I want to calculate theoretically my effective resolution from C8051F350 in-built sigma delta ADC with different interface options like ISL28134, ADA4528, ADA4898, OPA211, mcp6v07. I want to know ...
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0answers
903 views

I need to calculate the average power spectral density after passing packets through a butterworth filter using MATLAB

I am trying to generate 100 packets(row vectors each of size 8192) of random bits(1,-1),filter them using butterworth filter and then plot their average power spectral density. I have to do this using ...
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1answer
3k views

Accurately measure relative intensity noise (RIN) using RF spectral analyzer?

I'm trying to measure the relative intensity noise (RIN) of a laser using an RF spectrum analyser. It's a fairly common method (outline: How to measure relative intensity noise in lasers) although I ...