# Questions tagged [spectrum]

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### Two details about phase noise have been confusing me for a long time. Hope to be resolved

Just like FLOYD M. GARDNER said in the PhaseLock Techniques, 3rd Edition: "In light of that success in spectrum analyzers, a practitioner’s answer to the question above is: The spectrum of phase noise ...
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1 vote
88 views

### Power Spectral Density units

I am trying to compare power spectral density values (obtained from dsp.SpectrumAnalyzer) with PSD values obtained from hardware which has a VSA. MATLAB's documentation says that " The power spectral ...
• 11
1 vote
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### Noise Floor of ADC using PWELCH

While using MATLAB's Pwelch function, I am not able to match the noise floor of the "Modelled" ADC to (Delta)^2/6 {1 sided Spectrum}. ...
1 vote
140 views

### Speaker designed for ultrasound operation

I've created a transmission protocol in order to transmit information bits between a PC speaker and a smartphone, or between 2 smartphones using ultrasounds. I've implemented a QFSK system which uses ...
• 361
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### Power (dBm) of a non return to zero modulated signal

How to calculate the power (dBm) of this signal which is fed into a receiver with an input impedance of 50 ohms? The power in dBm formula is 10log(Vrms^2/R)/1mW and R equals 50 ohms. In this case how ...
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### When multiple cognitive radios transmit simultaneously

Cognitive radio nodes sense the spectrum and start their transmission opportunistically when the spectrum is found to be vacant. The question arises what if two or more nodes find the spectrum to be ...
• 111
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### Windowing FFT: spectral leakage vs ENOB

I am using Cadence to perform full speed testing of a 4-bit SAR ADC using the FFT and non-coherent sampling. I've obtained the ENOB and the spectra of the output signal using first the rectangular ...
• 1,117
42 views

### Linearly or logarithmically spaced frequency vector?

I am trying to compute the impedance of a circuit over a wide frequency range using the finite element method (fem). To do this, I apply an fft to the input voltage. Its spectrum starts at f_start = ...
• 309
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### Multi carrier frequency conversion and phase noise

I have a oscillator with a phase noise mask that was represented in dBc at specific offsets from a carrier. Two options with a multicarrier signal going into a converter, apply the phase noise mask (...
39 views

### Spectrum Sensing

I am trying to find the maximum range of a directional antenna whose beamwidth can be varied. The goal is to understand if a particular (x,y) user lies within the antenna. The distance between the ...
50 views

### Why the frequency spectrum of my OFDM output signal has a series of spike?

I'm trying to understand OFDM modulation using Matlab Simulink and I've built the following system I sent to the input of the OFDM block a frame of 15 samples that comes from the 16-QAM modulator. ...
• 211
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### N Fractional PLL spectrum

I'm studying the different types of N-fractional PLLs based on switching between two or more frequencies to get the desired frequency. However, I'm facing difficulties to understand how the output ...
16 views

### Does ITU govern both spectrum, and applied power?

I'm really not sure whether EE Stackexchange is the right place to ask. At the same time I'm sure it is the right place to expect a coherent reply. I am aware of the various bands (C, S, K, X...) that ...
• 2,911
140 views

### Spectrum of FM signal?

If a carrier ($f_c$) is FM modulated by a single sine wave ($f_m$), its spectrum is composed of frequencies at $f_c + kf_m$ ($k \in \mathbb{Z}$) whose amplitudes are weighted by $J_n(\beta)$,...
341 views

### DAC "aliasing" of harmonics

While reading articles and application notes regarding DACs and their output spectrum, I stumbled across aliasing of higher harmonics to the first Nyquist band. For example, when generating a single ...
• 55
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### Doppler spectral power density

In layman terms, why doppler spectral power density has U shape? Does this mean that frequency components with maximum doppler shift have maximum power? I am confused with the interpretation of the ...
• 257
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### non-negative FFT spectrum, subtlety

definations $x(t)$ is a function of time. Physically, it can be voltage, displacement, magnetization and so on. It can be real, complex, vectors or more fancy numbers. $C(t)$ is the auto ...
• 101
96 views

### Analog Led Audio Spectrum Analyzer Simulation

I am having a bit of trouble trying to simulate a variation(different frequency ranges/gain for the BP filters) of this project: https://makezine.com/projects/audio-spectrum-analyzer/ I am not too ...
Consider we need the magnitude spectrum of the signal. Signal is recorded in $N$ trials to a certain stimuli. Signal varies from each trial because of noise. So, to estimate the actual magnitude ...