Dynamic Bias LNA Circuit for Blocking Signal Cancellation
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Solution Overview
Problem
In crowded frequency bands, such as the Personal Communications Service (PCS) and ISM bands, receiver performance is severely affected by high-power blocking signals, leading to challenges in designing receivers that meet blocking tolerance standards without introducing noise and insertion loss.
Innovation Solution
A blocking signal-canceling low-noise amplifier system is developed, comprising a first low-noise amplifier with dynamic input matching and two operating modes, a blocking signal extraction and bias generation circuit, a bias switching circuit, and a bias switching signal generation circuit, which dynamically adjusts bias voltages to cancel blocking signals without using filters or mixers, thereby reducing noise and insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional filtering or mixing methods are used to handle blocking signals, then blocking signal rejection is improved, but noise figure and insertion loss increase
Solution Approach 1:
The patent converts the harmful blocking signal into a useful component by extracting its envelope to generate a bias voltage that dynamically adjusts the LNA's operating point. The blocking signal, previously causing saturation and performance degradation, now serves to automatically regulate the amplifier's gain and impedance matching, turning the harmful interference into a beneficial feedback mechanism that improves both blocking rejection and maintains low noise figure.
Solution Approach 2:
The patent implements a feedback mechanism where the envelope detector continuously monitors the output signal's blocking component and generates a corresponding bias voltage that feeds back to the LNA's gate. This closed-loop feedback dynamically adjusts the amplifier's operating conditions in real-time, automatically compensating for blocking signals and maintaining optimal performance without requiring external filtering components that would introduce noise and insertion loss.
2Object-affected harmful factors
If dynamic bias adjustment is implemented to cancel blocking signals, then blocking rejection is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the envelope detector and bias generation circuit to simultaneously perform blocking signal detection, envelope extraction, and dynamic bias adjustment. The same circuit components that detect the blocking signal also generate the corrective bias voltage, eliminating the need for separate filtering and control circuits. This universal approach reduces overall device complexity while achieving effective blocking cancellation.
Solution Approach 2:
The patent merges the blocking signal detection function and the bias control function into a single integrated circuit block. The envelope detector directly generates the bias voltage without requiring intermediate processing stages or separate control circuits. By combining these functions into one unified structure, the patent reduces the number of discrete components and interconnections, thereby simplifying the overall device architecture while maintaining effective blocking signal cancellation.
Data Source
AI summary
A blocking signal cancellation low noise amplifier system includes a first low noise amplifier, a second low noise amplifier, a blocking signal extraction and bias generation circuit, a bias switching circuit, and a bias switching signal generating circuit. The first low noise amplifier is used for dynamic input matching, and the first low noise amplifier receives an input signal and outputs it after amplifying. The blocking signal extraction and bias generation circuit is used to extract a blocking signal from the output signal of the first low noise amplifier, and output a DC voltage signal. The bias switching circuit is used to switch the first low noise amplifier between a blocking mode and a small signal mode. The bias switching signal generating circuit is used to compare the DC bias voltage signal VB2 with a preset reference voltage signal Vref.