Hartley Notch Canceller for High-Power Broadband Interferers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active cancellation schemes in RF and microwave receivers face limitations due to the incorporation of low-noise amplifiers in the primary signal path, which restricts power handling capabilities and are primarily effective for continuous wave or slow interferers, lacking high-linearity and power handling for broadband interferers.
Innovation Solution
The proposed interfering signal canceller employs a voltage sensor, coupler, Hartley image-reject down-converting and up-converting elements, phase slope compensator, and bandpass filters in the auxiliary path to generate and align an error signal for effective cancellation, reducing noise figure and enhancing power handling by minimizing components in the primary path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-noise amplifier is incorporated in the primary signal path to achieve active cancellation, then the cancellation performance for continuous wave or slow interferers is improved, but the power handling capability is limited
Solution Approach 1:
The signal path is divided into a primary path and an auxiliary path. The primary path processes the full signal with minimal components, while the auxiliary path extracts and processes only the interfering signal component. This segmentation allows the auxiliary path to handle high-power interferers separately without limiting the power handling of the primary LNA.
Solution Approach 2:
The interfering signal is extracted from the primary signal path using a coupler and voltage sensor, then processed separately in the auxiliary path through down-conversion, filtering, and up-conversion. This extraction removes the harmful high-power interferer from the primary path, enabling the LNA to operate at full power handling capability.
2Measurement precision
If traditional feed-forward active cancellation is used with down-conversion and up-conversion, then cancellation of known frequency interferers is achieved, but the system complexity increases with multiple mixers and filters
Solution Approach 1:
The Hartley image-reject architecture combines the down-conversion and up-conversion operations into a unified structure that shares common components between the primary and auxiliary paths. The polyphase filter and image-reject mixers are configured to simultaneously perform frequency conversion and phase alignment, reducing the total number of discrete components.
Solution Approach 2:
The auxiliary path components serve multiple functions: the down-converting element performs both frequency translation and phase extraction, the bandpass filter simultaneously rejects images and passes the interferer, and the up-converting element performs both frequency restoration and phase alignment. This multi-functionality reduces overall system complexity.
3Measurement precision
If the auxiliary path processes the full spectrum signal through down-conversion and filtering, then the interfering signal is isolated, but noise and desired signal leakage increase
Solution Approach 1:
The bandpass filter in the auxiliary path is tuned specifically to the interfering signal frequency, providing selective isolation. The Hartley image-reject architecture ensures that the filter only needs to pass the interferer while rejecting images and the desired signal, concentrating the filtering effort where it is most needed rather than requiring broad-spectrum filtering.
Solution Approach 2:
The image-reject mixing architecture converts the potential harm of image frequencies and desired signal leakage into beneficial phase relationships. By carefully controlling the phase shifts through the Hartley architecture, the desired signal and image frequencies are transformed into orthogonal components that can be selectively filtered, turning what would be harmful interference into a structured signal that aids in isolating the interferer.
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
This approach enables efficient cancellation of interfering signals with high phase accuracy and reduced noise figure, effectively handling high-power and broadband interferers, while maintaining high spurious-free dynamic range.
Implementation Method 1
The desired signal and the interfering signal in the auxiliary path are down-converted in frequency with in-phase (I) and quadrature (Q) local oscillator signals (LOI, LOQ) and a pair of mixers, as shown; with the interfering signal being converted to a known intermediate frequency (IF) or baseband frequency
Implementation Method 2
The signal is also sent through a bandpass or lowpass filter, which is tuned to the known IF or baseband frequency, to filter out all other signals (i.e. the desired signal) leaving only the interferer/error signal in the auxiliary path. This remaining interfering signal is then up-converted in frequency by in-phase (I) and quadrature (Q) local oscillator signals (LOI, LOQ) and a pair of mixers, as shown, back to the RF/microwave frequency of interest
Implementation Method 3
The signal is also sent through a bandpass or lowpass filter, which is tuned to the known IF or baseband frequency, to filter out all other signals (i.e. the desired signal) leaving only the interferer/error signal in the auxiliary path
Data Source
AI summary
An interfering signal canceller for cancelling an interfering signal component of an input signal includes a voltage sensor element disposed in a primary path and fed by the input signal, a coupler disposed in the primary path and fed by the voltage sensor element, a Hartley image-reject element disposed in an auxiliary path and fed by the input signal for converting the input signal to an intermediate or baseband frequency signal, a phase slope compensator disposed in the auxiliary path after the Hartley image-reject element to allow broadband phase adjustment of the interfering signal component of a converted input signal, and an inverse Hartley image-reject element disposed in the auxiliary path after the phase phase slope compensator to convert the passed the interfering signal component to the predetermined band of frequencies and having an output fed to the coupler.