Wideband RF Amplifier Circuit With Variable λ/4 Impedance Paths
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Solution Overview
Problem
Electronic devices face limitations in wideband operation due to the quality factor and bandwidth characteristics of transmission lines, particularly when handling wideband RF signals.
Innovation Solution
Incorporation of a MEMS switch into a λ/4 impedance transmission line of an amplifier circuit with a Doherty amplifier structure to efficiently handle RF signals of various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed λ/4 transmission line is used for impedance transformation, then the amplifier circuit can operate at a specific frequency, but the bandwidth and quality factor are limited
Solution Approach 1:
The patent applies dynamics by making the transmission line electrical length adjustable rather than fixed. A varactor diode is integrated into the λ/4 transmission line to dynamically change its electrical length based on the operating frequency. This allows the same physical transmission line to adapt to different frequency bands by varying the capacitance of the varactor diode, thereby resolving the contradiction between frequency adaptability and structural complexity.
2Adaptability or versatility
If the transmission line electrical length is fixed, then the circuit is simple, but it cannot efficiently handle wideband RF signals of various frequencies
Solution Approach 1:
The patent applies parameter changes by modifying the electrical length parameter of the transmission line through voltage-controlled varactor diodes. By changing the bias voltage applied to the varactor diodes, the capacitance value changes, which in turn changes the electrical length of the transmission line. This enables the impedance transformation circuit to adapt to different frequency bands without requiring multiple fixed transmission lines, thus achieving wideband operation while maintaining circuit simplicity.
3Adaptability or versatility
If multiple fixed transmission lines are used for different frequencies, then frequency coverage is improved, but the device complexity and size increase
Solution Approach 1:
The patent applies universality by designing a single λ/4 transmission line structure that can serve multiple frequency bands through the integration of varactor diodes. Instead of using separate fixed transmission lines for different frequency ranges, this universal transmission line can be dynamically reconfigured to match different impedance requirements across various frequency bands, thereby achieving broad frequency coverage with a single compact structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the ability of electronic devices to efficiently communicate using wideband RF signals by optimizing impedance and electrical length based on frequency and power mode.
Implementation Method 1
Incorporation of a MEMS switch into a λ/4 impedance transmission line of an amplifier circuit
Implementation Method 2
The electronic device may implement a transmission line connected with an amplifier by a λ/4 length to convert impedance of a load terminal
Data Source
AI summary
Disclosed is an electronic device comprising: a wireless communication circuit for generating an RF signal, an amplifier circuit electrically connected to the wireless communication circuit and configured to amplify the RF signal, and an antenna connected to the amplifier circuit. The amplifier circuit may comprise: a first amplifier; a second amplifier; a first transmission path connected to an output terminal of the first amplifier and the antenna; a second transmission path connected to an output terminal of the second amplifier and the first transmission path; a first variable impedance circuit located on the first transmission path and configured to change an electrical length of the first transmission path based on the frequency of the RF signal; and a second variable impedance circuit located on the second transmission path and configured to change the electrical length based on a power mode.