Active Input Matching in HEMT LNAs for Wideband Low Noise
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Solution Overview
Problem
Conventional low noise wide band amplifiers require large reactive elements like inductors and capacitors, leading to increased layout size and limited bandwidth, as well as input losses and noise degradation due to resistive components.
Innovation Solution
The use of an active load input matching network with a field effect transistor (FET) or high electron mobility transistor (HEMT) in a common gate configuration, which reduces noise and layout size by eliminating the need for reactive matching elements and minimizing thermal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reactive matching elements (inductors and capacitors) are used for input matching, then impedance matching is achieved, but the layout area increases and bandwidth is limited
Solution Approach 1:
The patent extracts and removes the reactive matching elements (inductors and capacitors) from the amplifier circuit, replacing them with an active input matching network composed of transistors and resistors. This elimination of discrete reactive components directly reduces the layout area while maintaining impedance matching functionality through the active network.
Solution Approach 2:
The patent substitutes the traditional passive reactive matching system (mechanical/electrical components like inductors and capacitors) with an active electronic matching system using transistors and resistors. This substitution enables impedance matching through active circuitry rather than passive elements, achieving both area reduction and bandwidth improvement.
2Ease of operation
If reactive matching elements (inductors and capacitors) are used for input matching, then impedance matching is achieved, but the bandwidth is limited to 10%-20%
Solution Approach 1:
The patent implements a dynamic active input matching network where the matching characteristics can adapt across a wide frequency range. The active components (transistors Q1 and Q2) provide frequency-dependent impedance transformation that maintains matching performance from DC to 18 GHz, unlike fixed reactive elements that are optimized for specific frequency points.
Solution Approach 2:
The patent changes the matching approach from fixed reactive impedance transformation to active impedance control through transistor biasing and circuit configuration. The active network dynamically adjusts impedance parameters across the frequency spectrum, enabling broadband matching from DC to 18 GHz rather than being limited to narrow bandwidth around a center frequency.
3Ease of operation
If reactive matching elements are used, then input matching is achieved, but input losses increase and noise performance degrades
Solution Approach 1:
The patent converts the inherently lossy nature of reactive components into a benefit by using active components that can provide gain while performing impedance matching. The active input matching network not only matches impedance but can also compensate for losses and reduce noise figure by using the transistor's amplification capability in the matching network itself.
Data Source
AI summary
A relatively wide bandwidth low noise amplifier with an active input matching network. The active load maybe formed from a field effect transistor (FET) or high electron mobility transistor (HEMT) in a common gate configuration. The active load input matching network has a lower overall noise component to only transistor channel noise than reactive matching components, such as inductors and capacitors. By utilizing the active mode input matching network in accordance with the present invention, the circuit layout such amplifiers can be reduces significantly, for example, 23 mils×47 mils.