Signal Properties

Envelope

The smooth curve outlining the amplitude extremes of a modulated RF signal, representing the instantaneous magnitude of the complex baseband signal over time

Category: Signal Properties

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Understanding Envelope

The signal envelope contains the amplitude modulation information and determines the instantaneous power level. In modern digital communications using QAM or OFDM, the envelope varies rapidly with high peak-to-average power ratios (PAPR).

Envelope tracking and envelope elimination and restoration (EER) are power amplifier techniques that modulate the supply voltage to follow the signal envelope, improving efficiency for signals with high PAPR compared to fixed-bias operation.

Common Questions

Frequently Asked Questions

What is envelope tracking?

Envelope tracking dynamically adjusts the power amplifier supply voltage to follow the signal envelope, keeping the PA operating near saturation for improved efficiency.

Why does the envelope matter for PA design?

High envelope variations (high PAPR) require the PA to operate with significant back-off from saturation, reducing average efficiency.

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