Hybrid Zero and Non-Zero IF Signal Processing Architecture
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Solution Overview
Problem
Existing RF systems face challenges in effectively filtering out interference signals, particularly those from adjacent channels, due to issues like image frequency interference, DC offset, and 1/f noise, especially when using methods like zero IF or non-zero IF approaches, which can introduce additional interference or fail to remove adjacent channel blockers.
Innovation Solution
A signal processing method that combines the zero IF method for separating interference in the translational path and the non-zero IF method for demodulating the desired signal, involving down-conversion, interference separation, up-conversion, and subtraction, with phase shifting to improve signal isolation and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If zero IF method is used to down-convert the signal, then image frequency interference is eliminated, but DC offset and 1/f noise problems are introduced
Solution Approach 1:
The patent divides the signal processing into two separate paths: a translational path using zero IF down-conversion to eliminate image frequency interference, and a main signal path using non-zero IF down-conversion to avoid DC offset and 1/f noise. This segmentation allows each path to be optimized for its specific function without suffering from the drawbacks of the other approach.
Solution Approach 2:
The patent introduces an intermediate frequency (IF) signal as a mediator between the RF input and baseband output. By using a non-zero IF in the main signal path, the system avoids the DC offset and 1/f noise problems that would occur with direct zero IF down-conversion, while still achieving the goal of eliminating image frequency interference through the translational path.
2Object-generated harmful factors
If non-zero IF method is used for down-conversion, then DC offset and 1/f noise are avoided, but image frequency interference occurs
Solution Approach 1:
The patent segments the signal processing into two paths with different down-conversion strategies. The translational path uses zero IF to handle image frequency rejection, while the main signal path uses non-zero IF to avoid DC offset and 1/f noise, allowing both requirements to be satisfied simultaneously.
Solution Approach 2:
The patent merges the advantages of both zero IF and non-zero IF methods by combining them in a hybrid architecture. The translational path provides image frequency rejection characteristic of zero IF, while the main signal path provides clean baseband signals characteristic of non-zero IF, creating a system that benefits from both approaches.
3Productivity
If high Q filter is used to filter out desired channel directly at high frequency, then channel selection is achieved, but circuit complexity and power consumption increase
Solution Approach 1:
The patent replaces the mechanical/high-Q filter approach with an electronic signal processing approach. Instead of using complex high-Q filters at high frequencies, the system uses frequency translation through mixing with local oscillators to convert the desired channel to a lower intermediate frequency where simple filtering can be performed, thereby reducing circuit complexity.
Solution Approach 2:
The patent changes the frequency parameter of the signal from high RF frequency to a lower intermediate frequency through down-conversion. This parameter change allows the use of simpler, lower-Q filters while maintaining effective channel selection, thereby reducing circuit complexity and power consumption.
4Object-affected harmful factors
If blocker signal is separated and up-converted in the translational path, then blocker filtering is achieved, but signal leakage and interference remain
Solution Approach 1:
The patent extracts the blocker signal from the mixed signal in the translational path by separating it based on frequency characteristics. The blocker signal is identified and removed through the translational processing path, preventing it from contaminating the main signal path and causing signal leakage or interference.
Solution Approach 2:
The patent performs preliminary blocker signal separation and removal in the translational path before the signal reaches the main signal path. This preliminary action prevents blocker signals from causing interference later in the processing chain, improving overall system reliability and reducing signal leakage.
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 effectively removes interference signals from adjacent channels, enhancing signal-to-noise ratio and improving receiver performance by utilizing a hybrid method that avoids the limitations of previous techniques, such as Hooman Darabi's SAW-less method.
Implementation Method 1
down-converting the input signal to a second frequency range, which is lower than the first frequency range, using an offset local oscillator signal
Data Source
AI summary
A signal processing method and system are provided. The method includes receiving an input signal within a first frequency range, the input signal including a desired signal and an interference signal. The method includes down-converting the input signal to a second frequency range, which is lower than the first frequency range, using an offset local oscillator signal having a frequency substantially equal to the central frequency of the desired signal. The method includes separating the interference signal from the down-converted input signal. The method includes up-converting the separated interference signal to the first frequency range. The method includes subtracting the up-converted interference signal from the input signal at the first frequency range to obtain an interference removed signal. The method includes down-converting the interference removed signal to a third frequency range, which is lower than the first frequency range, using a local oscillator signal, for demodulating. The frequency of the offset local oscillator signal is different from the frequency of the local oscillator signal.