Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

1
vote
0answers
44 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 ...
1
vote
1answer
62 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 ...
2
votes
2answers
45 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 ...
0
votes
1answer
64 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 ...
0
votes
2answers
98 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 ...
4
votes
2answers
58 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-...
2
votes
1answer
64 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 ...
0
votes
4answers
408 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 ...
2
votes
1answer
65 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)\$. ...
0
votes
2answers
83 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 ...
3
votes
2answers
218 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 ...
0
votes
0answers
64 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 ...
11
votes
4answers
281 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 ...
0
votes
1answer
70 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 ...
1
vote
3answers
1k 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. ...
1
vote
0answers
89 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 ...
1
vote
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) ...
0
votes
1answer
108 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 ...
1
vote
1answer
124 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 ...
4
votes
4answers
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 ...
7
votes
1answer
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 ...
0
votes
2answers
351 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 ...
3
votes
1answer
698 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
votes
1answer
1k 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(...
6
votes
1answer
470 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: ...
2
votes
2answers
360 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 ...
6
votes
4answers
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 ...
0
votes
1answer
153 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 ...
6
votes
1answer
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? ...
0
votes
1answer
251 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 ...
3
votes
2answers
141 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 ...
8
votes
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 ...
1
vote
0answers
378 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 ...
1
vote
1answer
808 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 ...
0
votes
0answers
336 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; ...
0
votes
1answer
81 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 ...
1
vote
0answers
105 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 ...
0
votes
1answer
319 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
votes
1answer
209 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 ...
4
votes
1answer
332 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 ...
0
votes
1answer
90 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/...
2
votes
1answer
397 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 ...
0
votes
1answer
207 views

Johnson noise with amplifier circuit

I need help with this problem. Some numerical answers would also be very helpful.
-1
votes
1answer
390 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!
-3
votes
1answer
64 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) ...
1
vote
1answer
86 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
votes
1answer
2k 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 ...
1
vote
3answers
595 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 (...
1
vote
3answers
94 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 ...
-2
votes
1answer
937 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?