Cascode Amplifier Notch Filter for Low-Cost Jammer Rejection
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Solution Overview
Problem
Existing wireless communication devices face challenges in effectively rejecting jammers, which interfere with signal reception, leading to reduced receiver sensitivity and increased costs due to the use of large and costly off-chip filters or instability issues with frequency-selective feedback networks.
Innovation Solution
An amplifier with an integrated notch filter is designed, utilizing a cascode amplifier structure and a notch filter that reuses the inductance from the bypass path to provide jammer rejection, eliminating the need for separate off-chip inductors and reducing costs while maintaining effective jammer attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive filters with SMD inductors are provided in the receive signal path, then jammer rejection is improved, but circuit area and product cost increase
Solution Approach 1:
The patent combines the bypass inductor (already present in the amplifier circuit) with the notch filter inductor to create a shared inductive component. This merging eliminates the need for a separate off-chip inductor, reducing circuit area while maintaining effective jammer rejection through the integrated notch filter structure
Solution Approach 2:
The bypass inductor is given dual functionality: it continues to provide signal bypassing while also serving as the inductive element for the notch filter. This multi-functionality reduces the total component count and circuit area without compromising jammer rejection performance
2Object-affected harmful factors
If passive filters with SMD inductors are provided in the receive signal path, then jammer rejection is improved, but product cost increases
Solution Approach 1:
The patent merges the bypass inductor and notch filter inductor into a single shared component, eliminating the need for expensive off-chip SMD inductors. This integration reduces component count and assembly complexity, thereby lowering product cost while maintaining effective jammer rejection
Solution Approach 2:
The amplifier's existing bypass inductor is repurposed to serve the notch filter function as well. This self-service approach eliminates the need for additional external components, reducing both bill of materials cost and manufacturing complexity
3Object-affected harmful factors
If frequency-selective properties are designed into the LNA feedback network, then jammer rejection is improved, but receiver stability and performance deteriorate
Solution Approach 1:
The patent extracts the frequency-selective filtering function from the feedback network and relocates it to a dedicated notch filter stage. This separation allows the feedback network to maintain stability while the notch filter provides the necessary jammer rejection, eliminating the instability issues associated with frequency-selective feedback
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 integrated notch filter effectively attenuates jammer signals, improving receiver sensitivity and reducing costs by integrating the notch filter within the amplifier circuit, thereby enhancing the device's ability to handle multiple radio frequency transmissions without the drawbacks of prior art techniques.
Implementation Method 1
a capacitor and an inductor forming an LC circuit
Data Source
AI summary
Techniques for providing low-cost and effective jammer rejection for an amplifier is disclosed. The amplifier includes an input node and an output node, a first transistor and a second transistor, a load circuitry, an inductor, and a capacitor. A first terminal of the first transistor is coupled to a ground. A second terminal of the first transistor is coupled to a first terminal of the second transistor. A second terminal of the second transistor is coupled to the output node. The load circuitry is coupled between a power supply and the second terminal of the second transistor. A first terminal of the inductor is coupled to the ground through a first switch. A first terminal of the capacitor is coupled to the first terminal of the second transistor and a second terminal of the capacitor is coupled to a second terminal of the inductor.