# Tag Info

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My first inclination is to say this is a meaningless question. The concept of "instantaneous" frequency really only pertains to a single pure tone with a slightly varying frequency. In this light, one may construct a definition saying "The instantaneous frequency at time $t$ is the same as that of a pure tone which matches the function (sum) in the ...

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Eventhough Laurent has given a broader sense of the answer, let me put here the communications theory sense ot it. The concept of instantaneous freqency emerges when you consider Frequency Modulation or Phase Modulation systems, where the message is embedded into the change of the frequency or phase of a carrier signal. This carrier is typically a single ...

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The notion of instantaneous frequency is (hopefully) consistent with the monochromatic wave model: $$x(t)=a \cos 2\pi \nu t\,,$$ where $a$ is the amplitude and $\nu$ the frequency. It would be tempting to compute a similar formula for evolving amplitude and frequency cases, something like: $$x(t)=a(t) \cos \left(\phi(t)\right)\,.$$ However, this is not ...

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Assuming that the relevant portion of a continuous-time signal $x(t)$ is inside (or has been shifted to) the interval $[0,T]$, the DFT of a sampled version of the signal approximates the continuous-time Fourier transform (CTFT) in the following way: \begin{align}X(f)&=\int_{-\infty}^{\infty}x(t)e^{-j2\pi ft}dt\\&\stackrel{\textrm{truncation}}{\... 2 Not sure to understand what you are asking, Microwaves wavelengths range between 300 MHz (1 m) and 300 GHz (1 mm) which is indeed of the same order of magnitude as the probe. 1GHz corresponds to a wavelengths of about 30 cm and is also in the Microwave range. Are you saying that it is possible to measure a frequency of 1GHz with a probe while it is ... 1 As a simple example, consider the discrete-time signalx[n]=a^nu[n],\qquad |a|<1\tag{1}$$where u[n] is the unit step function. The discrete-time Fourier transform (DTFT) of x[n] is given by$$X(e^{j\omega})=\frac{1}{1-ae^{-j\omega t}}\tag{2}$$Note that \omega is a normalized angular frequency:$$\omega=2\pi f/f_s\tag{3}$$where f_s is ... 1 I think you consider that pulse in the spectrum as the noise. Then you should remove it by a lowpass filter of cutoff frequency$$ f_c = 5 ~\text{kHz.} Slightly less than this should be used for guarding against the transition width of the lowpass filter. So you better select something like $4.8$ kHz for the lowpass filter cutoff frequency. Note that ...

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Carry the units and it becomes understandable. T = 0.03125 seconds per sample Thus your sampling rate is 1/T = 32 samples per second Each bin corresponds to the cycles per frame. Your frame has four samples. Suppose the bin index is k. k (cycles per frame) * 32 (samples per second) / 4 (samples per frame) = 8k cycles per second = 8k Hz So the ...

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