Zero-Peaking Envelope Tracking Modulator for Wide Bandwidth
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Solution Overview
Problem
Traditional fixed supply voltage in power amplifiers for wireless communication devices leads to significant power loss as heat due to inefficiency, and wide-bandwidth envelope tracking designs are power-hungry, requiring increased quiescent current.
Innovation Solution
An envelope tracking supply modulator with a zero peaking circuit that adjusts the frequency and gain to increase bandwidth without additional current consumption, using an amplifier circuit and an adjustable zero peaking circuit to insert a zero at a specific frequency, allowing for efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transconductance (bias current) of a linear amplifier is increased to enhance bandwidth and linearity, then the bandwidth and linearity are improved, but the power consumption increases significantly
Solution Approach 1:
The patent changes the frequency parameter by inserting a zero at a specific frequency (ωz = 1/RC) to push the dominant pole to a higher frequency. This allows the amplifier to achieve wide bandwidth without increasing the bias current, as the frequency compensation modifies the transfer function rather than relying on higher transconductance
Solution Approach 2:
The patent introduces an intermediary zero (through the RC network) that mediates between the amplifier stages. This zero compensates for the dominant pole's effect, allowing the system to achieve higher bandwidth without directly increasing the bias current that would otherwise be needed
2Device complexity
If a fixed supply voltage is used in a power amplifier, then the circuit is simple, but significant power is dissipated as heat when operating below peak RF output power
Solution Approach 1:
The patent implements dynamic supply voltage modulation that tracks the envelope of the RF input signal. Instead of a fixed supply voltage, the PA supply voltage is dynamically adjusted to match the signal envelope, allowing the amplifier to operate efficiently across varying power levels and minimize power dissipation as heat
3Speed
If an envelope tracking supply modulator is designed for wide bandwidth, then the bandwidth is improved, but the quiescent current of the linear amplifier increases dramatically
Solution Approach 1:
The patent achieves wide envelope tracking bandwidth by changing the frequency parameter through zero insertion. The zero is placed at a frequency that pushes the dominant pole higher, extending the bandwidth without requiring increased bias current. The transfer function modification achieves bandwidth expansion through frequency compensation rather than transconductance increase
Data Source
AI summary
An envelope tracking supply modulator includes an amplifier circuit and a zero peaking circuit. The amplifier circuit receives an envelope input, generates a modulated supply voltage according to the envelope input, and provides the modulated supply voltage to a power amplifier. The zero peaking circuit is coupled to the amplifier circuit, and applies zero peaking to the amplifier circuit, where the zero peaking inserts a zero at a frequency.