Multi-Frequency RF Transmitter for Interference-Resistant Security Sensors
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Solution Overview
Problem
Current security system sensors face challenges with single frequency RF transmitters due to susceptibility to interference from background noise, while frequency hopping solutions are complex and costly, and none are cost-effective and simple yet FCC Part 15 compliant.
Innovation Solution
A multi-frequency wireless transmitter that generates a plurality of carrier frequencies, selects and transmits signals over these frequencies using calculated parameters, and switches between them to ensure reliable communication within FCC Part 15 regulations, implemented as an integrated circuit package with adjustable power output levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single frequency transmission is used, then device complexity is reduced, but reliability deteriorates due to susceptibility to interference from background noise
Solution Approach 1:
The transmission signal is segmented across multiple frequency carriers instead of using a single frequency. The message is divided into multiple signals, each transmitted on a different carrier frequency within the 260-470 MHz band, which reduces susceptibility to interference from background noise at any single frequency while maintaining relatively simple transmitter design.
Solution Approach 2:
The system changes the frequency parameter of the carrier waves to improve reliability. By transmitting the same message on multiple carrier frequencies rather than a single frequency, the system achieves better resistance to interference while keeping the transmitter design simple and cost-effective.
2Reliability
If frequency hopping is used, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
Instead of implementing complex frequency hopping with rapid switching and synchronization requirements, the patent segments the message into multiple signals transmitted simultaneously or sequentially on different fixed carrier frequencies. This achieves diversity against interference without requiring the complex clock synchronization and pseudo-random number generators needed for frequency hopping.
Solution Approach 2:
The patent uses multiple simple carrier frequency transmissions instead of one complex frequency-hopping system. Each carrier frequency transmission is a simple, inexpensive signal that can be easily generated and transmitted, replacing the need for expensive and complex frequency hopping implementation while achieving similar reliability benefits.
3Reliability
If multiple frequencies are used to transmit signal, then reliability is improved, but power consumption increases
Solution Approach 1:
The system transmits the message multiple times across different carrier frequencies, which could be seen as excessive action. However, by reusing the same message content across multiple carriers rather than transmitting entirely new information each time, the system achieves reliability improvement while keeping power consumption manageable through efficient signal reuse.
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 solution provides reliable wireless communication with improved resistance to interference, meeting FCC Part 15 requirements while being inexpensive and simpler in design compared to frequency hopping systems.
Implementation Method 1
RF frequencies generally extend from about 9 KHz to well over 100 GHz in the electromagnetic spectrum... The RF band of particular interest for communication between sensors and a monitoring system are in the 260 MHz to 470 MHz range
Implementation Method 2
a power amplifier having multiple voltage output levels... The multiple voltage output levels of the power amplifier are selectable, and the controller means is configured for selecting a first frequency of the plurality of carrier frequencies
Data Source
AI summary
A multi-frequency wireless transmitter is provided for use in automated security systems. The multi-frequency wireless transmitter transmits a message over a plurality of frequencies, thus diminishing the effects of noise interference. The transmitter includes a frequency generator capable of selectably generating a plurality of frequencies lying within the 260 to 470 MHz frequency band. An RF power amplifier having multiple power output values selectable to match with the selected generated frequency regulates the transmit power.