Two-Stage LNA With Mutual Coupling for Wide-Band Matching
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Solution Overview
Problem
Modern RF receivers require multiple narrow-band, single-stage LNAs to cover various frequency bands, leading to significant die area consumption and challenges in achieving low noise, gain flatness, linearity, input matching, and output matching across a wide band.
Innovation Solution
A mutually coupled inductor circuit-based, wide-band, two-stage LNA configuration that uses electromagnetically coupled inductors to increase output bandwidth without increasing physical size, providing a shared effective inductance and feedback path for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple narrow-band, single-stage LNAs are used to cover various frequency bands, then frequency coverage is improved, but die area consumption increases significantly
Solution Approach 1:
The patent combines multiple narrow-band LNA functions into a single wide-band LNA by using a two-stage amplifier architecture with electromagnetic coupling. The first amplifier stage handles lower frequencies while the second stage handles higher frequencies, and they are coupled through mutually coupled inductors to achieve seamless wide-band coverage in a single device, thereby reducing die area consumption.
Solution Approach 2:
The wide-band LNA is designed to perform multiple frequency band coverage functions that previously required separate narrow-band LNAs. By implementing a two-stage architecture with adjustable coupling, a single LNA device can universally cover multiple frequency bands, eliminating the need for multiple dedicated amplifiers and reducing overall die area.
2Reliability
If multiple narrow-band, single-stage LNAs are spaced apart to avoid cross-coupling, then signal interference is reduced, but die area increases
Solution Approach 1:
The patent converts the traditionally harmful electromagnetic coupling between inductors into a beneficial feedback mechanism. By deliberately designing mutually coupled inductors with controlled coupling coefficients, the circuit uses the coupling effect to provide feedback that improves gain flatness and bandwidth, thereby eliminating the need to space components apart while actually improving performance.
Solution Approach 2:
The electromagnetic coupling between inductors in the two-stage LNA creates an inherent feedback path. The coupled inductors allow signal energy to be fed back from the second stage to the first stage, improving overall stability, gain flatness, and bandwidth. This controlled feedback mechanism enhances signal quality without requiring increased spacing between components.
3Area of stationary object
If a single wide-band LNA is used instead of multiple narrow-band LNAs, then die area is reduced, but achieving low noise and gain flatness across wide band becomes difficult
Solution Approach 1:
The wide-band LNA is segmented into two distinct amplifier stages, each optimized for specific frequency ranges. The first stage is optimized for lower frequencies with appropriate inductance values, while the second stage handles higher frequencies. This segmentation allows each stage to maintain optimal noise figures and gain characteristics for its frequency range, achieving overall wide-band performance with improved flatness.
Solution Approach 2:
The patent introduces dynamic control through adjustable coupling between the two stages. By varying the coupling coefficient between the mutually coupled inductors, the system can dynamically adapt its frequency response and gain distribution across the bandwidth. This dynamic adjustment capability enables precise control over gain flatness and noise performance across the entire wide frequency range.
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 solution achieves wide-band coverage with minimal performance degradation compared to multiple narrow-band LNAs, reducing die area and enabling smaller ICs while maintaining necessary matching characteristics.
Implementation Method 1
A mutually coupled inductor circuit-based, wide-band, two-stage LNA configuration that uses electromagnetically coupled inductors to increase output bandwidth without increasing physical size
Data Source
AI summary
Compact low noise amplifiers that have wide-band coverage while meeting necessary input matching and output matching characteristics. Embodiments include a wide-band, two-stage LNA with minimum degradation in performance compared to multiple narrow-band, single-stage LNAs. A generalized embodiment includes a first amplifier stage having a terminal coupled to a mutually coupled inductor circuit and to a second amplifier stage. The second amplifier stage includes a terminal coupled to the mutually coupled inductor circuit. The mutually coupled inductor circuit comprises electromagnetically coupled inductors L1, L2. Second terminals of the first and second amplifier stages are coupled to respective degeneration inductors. The electromagnetically coupled inductors L1, L2 of the inductor circuit substantially increase the output bandwidth of the LNA with minimum degradation in performance.