Bias-Controlled RF Amplifier for Wide Power Range Gain Control
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Solution Overview
Problem
Existing RF amplifiers require multiple power amplifier modules and separate RF output pins for different power modes, making them cumbersome and difficult to maintain precise power gain control across a range of output powers.
Innovation Solution
An amplifier with amplifying elements that switch between non-switching and switching modes of operation in response to a bias control signal, allowing for efficient operation across a larger power range using a single RF output pin and reducing the need for multiple external amplifiers, with a reactive load network to manage transient responses and a cascode arrangement for granular gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple power amplifier modules are used to achieve different output powers, then the power range is extended, but the device complexity increases and precise power gain control becomes difficult
Solution Approach 1:
The patent applies dynamics by enabling the amplifying element to dynamically switch between non-switching mode (Class AB) and switching mode (Class E) based on the desired output power level. The biasing circuit adjusts the bias voltage in response to a bias control signal, allowing the amplifying element to transition between operating modes. This dynamic operation enables a single amplifier module to achieve multiple output power levels (2.5 dBm, 10 dBm, 18 dBm) without requiring multiple separate amplifier modules, thereby reducing device complexity while maintaining adaptability across different power ranges.
2Adaptability or versatility
If multiple power amplifier modules are used to achieve different output powers, then the power range is extended, but precise power gain control becomes difficult
Solution Approach 1:
The patent applies parameter changes by modifying the bias voltage parameter to control the operating mode of the amplifying element. The biasing circuit responds to a bias control signal by adjusting the bias voltage, which in turn changes the operating characteristics of the amplifying element between Class AB and Class E modes. This parameter-based control mechanism enables precise power gain control across different output power levels, as the bias voltage can be finely adjusted to achieve the desired gain characteristics for each power level, avoiding the imprecision associated with multiple discrete amplifier modules.
3Loss of energy
If switching mode operation is used for higher efficiency, then power efficiency improves, but transient response control becomes critical
Solution Approach 1:
The patent applies the intermediary principle by introducing a reactive load network as a mediator between the amplifying element and the load. The reactive load network, comprising inductors and capacitors, is configured to yield a transient response that avoids simultaneous imposition of substantial voltage across and substantial current through the amplifying element during switching transitions. This intermediary network shapes the transient response to be compatible with switching mode operation, enabling the amplifying element to operate efficiently in Class E mode while controlling the transient behavior to prevent excessive stress and energy loss during mode transitions.
Data Source
AI summary
An amplifier comprising at least one amplifying element (20a, 25a) and a biasing circuit (32a, 32b) for biasing the or each amplifying element with a bias voltage is disclosed. The biasing circuit (32a, 32b) is adapted to vary the bias voltage such that the or each amplifying element switches between non-switching and switching modes of operation in response to a bias control signal (4) passing through a threshold value.