Adjacent-Channel Interference Reject Filter Using Short-Pulse Inversion
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Solution Overview
Problem
Conventional FM demodulation systems face challenges in effectively rejecting interference signals due to the limitations of analog and digital IF filters, which affect performance, increase circuit size, and consume high power.
Innovation Solution
An adjacent-channel interference reject filter is introduced, comprising a short-pulse inverter and an inversion controller that detects and inverts short pulses in IF signals, allowing for efficient rejection of interference while preserving desired signals, thereby reducing circuit complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an analog IF filter is used to reject interference signals, then the filtering function is provided, but the circuit size increases and the filtering properties are affected by temperature and element variations
Solution Approach 1:
The patent replaces the mechanical/analog IF filter system with a digital signal processing system. A digital IF filter implemented through software or firmware in a microcontroller substitutes the physical analog filter components, eliminating temperature and element variation effects while reducing circuit size. The digital processing approach allows for precise filtering characteristics that are not susceptible to environmental factors.
Solution Approach 2:
The patent changes the operating parameters by transitioning from analog domain filtering to digital domain filtering. The filtering is performed on digitized IF signals using digital signal processing algorithms, allowing for dynamic adjustment of filtering parameters without changing physical components. This enables precise control of filtering characteristics while maintaining compact circuit design.
2Object-affected harmful factors
If a digital IF filter is used with an ADC, then the intended filtering properties are obtained, but the consumption of electric current increases
Solution Approach 1:
The patent applies preliminary analog filtering before ADC conversion to reduce the burden on the digital filter. By performing initial interference rejection in the analog domain using a simple analog filter, the digital filter can operate with lower complexity and lower sampling rates, thereby reducing ADC and digital processing power consumption while still achieving the required filtering performance.
Solution Approach 2:
The patent implements a hybrid filtering approach where partial filtering is done in the analog domain and partial filtering is done in the digital domain. This division of labor allows the system to achieve complete interference rejection without requiring full digital filtering capability, thus reducing ADC specification requirements and overall power consumption while maintaining effective interference signal rejection.
3Object-affected harmful factors
If an analog IF filter with complex internal structure is used, then the performance in rejecting interference signals is increased, but the size of the circuit increases
Solution Approach 1:
The patent replaces complex analog filter structures with a simplified analog filter combined with digital signal processing. Instead of using multiple cascaded analog filter stages that would increase circuit size, the system uses a single or minimal analog filter stage followed by digital filtering algorithms that provide the same or better interference rejection performance in a more compact form factor.
Data Source
AI summary
According to one embodiment, an adjacent-channel interference reject filter comprises a short-pulse inverter which includes a short-pulse sensor configured to detect a pulse in an intermediate frequency signal supplied to the device. The short-pulse sensor detects pulses having a pulse width less than or equal to some predetermined width. The short-pulse inverter also includes a pulse inverter configured to invert the pulse detected by the short-pulse sensor. The adjacent-channel interference reject filter may also include an inversion controller to control the inverting of detected short pulses. An adjacent-channel interference reject filter may be included in various devices such as wireless communication devices.