Distributed Amplifier Variable Termination for Gain Flatness
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Solution Overview
Problem
Conventional distributed amplifiers face issues with gain flatness due to constant terminal resistance that does not match the varying output resistance of the signal amplification unit as DC bias voltage changes, affecting the amplification performance.
Innovation Solution
A distributed amplifier with a variable terminal resistance is introduced, allowing for resistance matching with the output resistance of the signal amplification unit by adjusting the resistance using a resistance adjusting transistor and bypass inductor, thereby improving gain flatness and increasing the gain-adjustable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant terminal resistance is used in the distributed amplifier, then the circuit structure is simple, but the resistance does not match the varying output resistance of the signal amplification unit when DC bias voltage changes, resulting in poor gain flatness
Solution Approach 1:
The patent applies the dynamics principle by replacing the constant terminal resistance with a variable terminal resistance that can be adjusted according to different DC bias voltages. The terminal resistance is controlled by a bias voltage applied to a control electrode (gate or base) of the active device, allowing the resistance to dynamically adapt to different operating conditions. This enables the amplifier to maintain optimal resistance matching and gain flatness across different gain settings while preserving circuit simplicity.
2Adaptability or versatility
If the DC bias voltage of the signal amplification unit is changed to achieve different gains, then the gain is adjustable, but the output resistance varies, causing mismatch with the constant terminal resistance and degrading gain flatness
Solution Approach 1:
The patent implements a feedback mechanism where the same DC bias voltage that controls the gain of the signal amplification unit is also used to control the terminal resistance. This creates a coupled control system where the terminal resistance automatically adjusts in response to bias voltage changes, maintaining resistance matching across different gain settings. The feedback ensures that gain adjustability is achieved without compromising gain flatness.
Solution Approach 2:
The patent applies parameter changes by varying the terminal resistance parameter in response to changes in DC bias voltage. Instead of keeping the terminal resistance constant, the system dynamically adjusts this parameter to match the varying output resistance of the amplification unit. This parameter adaptation enables the amplifier to maintain optimal performance across different operating conditions while preserving gain adjustability.
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
The variable terminal resistance ensures improved gain flatness and a wider gain-adjustable range by compensating for load mismatch and varying bias voltages, enhancing the amplification performance across different frequencies.
Implementation Method 1
a variable terminal resistance having a first end and a second end and providing a variable resistance to match with an output resistance of the signal amplification unit
Data Source
AI summary
A distributed amplifier is disclosed herein, which includes a signal amplification unit amplifying a RF input signal fed into the RF signal, a first biasing circuit providing a direct current (DC) bias signal, a second biasing circuit providing a DC bias signal, the variable terminal resistance providing an adjustable resistance, a RF signal input terminal provided for input of the RF input signal and a RF signal output terminal for output of a RF output signal. The output RF signal from the distributed amplifier is obtained from a gained version of the input RF signal. Since a load mismatch issue is compensated, a gain flatness issue is considerably improved and thus a gain-adjustable range is increased with respect to the distributed amplifier.