SAW Oscillator Receiver IC for Frequency Drift Tolerance
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Solution Overview
Problem
In keyless entry and remote control systems, existing receiver ICs with narrow intermediate frequency (IF) pass band filters fail to receive signals due to frequency drift, causing system malfunction when the bandwidth of the IF low pass filter is limited, leading to signal removal and system failure.
Innovation Solution
A receiver IC with a SAW-based oscillator incorporating an oscillating circuit comprising an inverter stage, capacitors, and a resistor, coupled with a widened IF low pass filter bandwidth of 1.5 MHz to 4 MHz and a center frequency of 1.8 MHz to accommodate frequency drift, ensuring signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow IF pass band filter is used in the receiver IC, then the filter selectivity is improved, but the receiver fails to receive signals due to frequency drift
Solution Approach 1:
The patent applies dynamics by making the IF filter bandwidth adjustable rather than fixed. The system can dynamically change the filter bandwidth from a narrow state (for high selectivity) to a wider state (for frequency drift tolerance), allowing it to adapt to different operational conditions and resolve the contradiction between selectivity and reliability
Solution Approach 2:
The patent changes the bandwidth parameter of the IF filter to resolve the contradiction. By adjusting the bandwidth parameter from narrow to wide, the system can maintain signal reception under frequency drift conditions while preserving the ability to achieve high selectivity when needed
2Device complexity
If the bandwidth of the IF low pass filter is limited, then the filter complexity is reduced, but signal removal occurs due to frequency drift
Solution Approach 1:
The system dynamically adjusts the IF filter bandwidth based on operational requirements. When frequency drift is detected or anticipated, the bandwidth is increased to prevent signal removal, while maintaining a simpler narrow bandwidth configuration when high selectivity is sufficient, thus balancing complexity and reliability
3Reliability
If a SAW-based oscillator with widened IF filter bandwidth is implemented, then signal reception under frequency drift is improved, but the device complexity increases
Solution Approach 1:
The SAW device serves multiple functions: it acts as both the frequency reference for the oscillator and provides the IF filtering function. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving improved signal reception reliability through the widened bandwidth capability
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 widened bandwidth of the IF low pass filter allows the receiver IC to maintain signal reception even with frequency drift, preventing system failure and ensuring proper operation of remote control systems.
Implementation Method 1
The inverter stage has input and output terminals respectively coupled to two ends of the external SAW device
Data Source
AI summary
A receiver IC provided with a SAW-based oscillator with an external SAW device. The receiver IC comprises an oscillating circuit. The oscillating circuit comprises an inverter stage, a first capacitor, a second capacitor, and a resistor. The inverter stage has input and output terminals respectively coupled to two ends of the external SAW device. The first and second capacitors are respectively coupled between the input/output terminal and a ground. The resistor is coupled between the input and output terminals of the inverter stage.