The aperture effect rolls off high message frequencies in flat-top PAM. Here’s how pulse duration limits that distortion to under 0.5% and when an equalizer helps.
The aperture effect rolls off high message frequencies in flat-top PAM. Here’s how pulse duration limits that distortion to under 0.5% and when an equalizer helps.
Flat-top PAM holds each sample’s amplitude for the pulse duration, weighting the spectrum with a sinc function.…
Flat-top PAM holds each sample’s amplitude for the pulse duration, weighting the spectrum with a sinc function. Here’s how that weighting leads to the aperture effect.
Multiplying a message by a pulse train replicates its spectrum at every harmonic. See why a 1/3 duty cycle and 4x…
Multiplying a message by a pulse train replicates its spectrum at every harmonic. See why a 1/3 duty cycle and 4x oversampling stretch the bandwidth roughly 12-fold.
Interference in FM grows stronger with frequency offset, until pre-emphasis flattens the curve. See why a signal just…
Interference in FM grows stronger with frequency offset, until pre-emphasis flattens the curve. See why a signal just twice as strong as a rival broadcast can completely capture the channel.
Pre-emphasis and de-emphasis boost noise performance in FM, but only up to a point—push the gain too far and you risk…
Pre-emphasis and de-emphasis boost noise performance in FM, but only up to a point—push the gain too far and you risk overmodulation.
Simple first-order pre-emphasis and de-emphasis filters can boost FM receiver SNR by more than 13 dB by exploiting the…
Simple first-order pre-emphasis and de-emphasis filters can boost FM receiver SNR by more than 13 dB by exploiting the spectral differences between signal and noise.
Worked examples quantify just how much the FMFB loop shrinks noise bandwidth. We also show how the PLL demodulator offers…
Worked examples quantify just how much the FMFB loop shrinks noise bandwidth. We also show how the PLL demodulator offers a simpler alternative for reducing threshold.
While feedback lowers the FM detection threshold, it offers no noise advantage over conventional receivers when the…
While feedback lowers the FM detection threshold, it offers no noise advantage over conventional receivers when the carrier power is strong. Discover why in this discussion and mathematical analysis.
By closing a feedback loop around the demodulator, the FMFB architecture narrows the noise bandwidth and lowers the FM…
By closing a feedback loop around the demodulator, the FMFB architecture narrows the noise bandwidth and lowers the FM threshold, without improving SNR at high CNR.
Discover how the LT1079 quad op-amp minimizes sensor loading in battery-powered designs. Active cancellation and an…
Discover how the LT1079 quad op-amp minimizes sensor loading in battery-powered designs. Active cancellation and an onboard bridge network ensure maximum precision for resistive sensors.
Working through examples shows how the threshold effect reshapes FM design choices. See how ignoring it can undershoot…
Working through examples shows how the threshold effect reshapes FM design choices. See how ignoring it can undershoot the required carrier power by over 5x for the same target SNR.
This project brief describes how to build and use an Arduino-compatible board that reads a linear Hall-effect sensor and…
This project brief describes how to build and use an Arduino-compatible board that reads a linear Hall-effect sensor and reports the measurement over an RS-485 bus.
The standard FM SNR equation breaks down once the carrier-to-noise ratio drops below a critical threshold, revealing a…
The standard FM SNR equation breaks down once the carrier-to-noise ratio drops below a critical threshold, revealing a hard limit on trading bandwidth for noise performance.
Deriving a general signal-to-noise expression for frequency modulation with any message signal reveals a core trade-off:…
Deriving a general signal-to-noise expression for frequency modulation with any message signal reveals a core trade-off: more deviation buys better noise performance, but only by using more bandwidth.
This article explores how combining signal and noise power reveals how the FM system’s output SNR scales with carrier…
This article explores how combining signal and noise power reveals how the FM system’s output SNR scales with carrier amplitude and modulation index.
Explore how frequency-modulated waves resist interference. We break down the demodulator architecture and derive the…
Explore how frequency-modulated waves resist interference. We break down the demodulator architecture and derive the exact output signal power for a sinusoidal message.
Envelope detection is simple, but that simplicity has a noise-performance cost. Here’s how much SNR conventional AM…
Envelope detection is simple, but that simplicity has a noise-performance cost. Here’s how much SNR conventional AM gives up compared to its coherent counterparts.
Using a graphical approach, we show that coherent SSB demodulation leaves the input and output SNR unchanged, then…
Using a graphical approach, we show that coherent SSB demodulation leaves the input and output SNR unchanged, then compare its noise performance to DSB-SC and baseband systems.
This project brief describes how to build and use a four-channel differential line receiver module for balanced RS-422…
This project brief describes how to build and use a four-channel differential line receiver module for balanced RS-422 and RS-485 data links.
Visualizing how correlated and uncorrelated signals combine offers an intuitive look at power transformation. See how…
Visualizing how correlated and uncorrelated signals combine offers an intuitive look at power transformation. See how this difference boosts baseband power to double the output SNR.
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