Return Loss Channel Detection in Set Top Boxes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing digital set-top box systems face challenges in automatically determining the channel tuned by an analog TV or VCR, leading to issues with recording digital video programs, as they require manual intervention or infrared transducers that are prone to errors and are unsightly.
Innovation Solution
The system uses return loss channel detection to determine the channel by measuring the passband frequency of the tunable bandpass filter in the TV or VCR tuner, generating probe signals and measuring reflected power to identify the channel, and learning the unique return loss signature of each channel to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If infrared transducers are used to control set top box channel tuning, then channel switching can be automated, but the system becomes unreliable due to transducer dislodgement or malfunction
Solution Approach 1:
The VCR performs self-service by automatically detecting the channel it is tuned to through return loss measurement, eliminating the need for external infrared transducers. The VCR's tuner inherently provides the channel information through its RF characteristics, making the system self-sufficient and reliable.
Solution Approach 2:
The invention uses return loss measurement as an intermediary mechanism to communicate channel information. Instead of using infrared transducers as intermediaries between VCR and STB, the system uses the RF signal characteristics themselves as the mediator, creating a direct and reliable connection.
2Extent of automation
If infrared transducers are used for channel control, then automation is achieved, but the device complexity increases and the appearance is degraded
Solution Approach 1:
The invention extracts the channel detection capability from external infrared transducers and integrates it directly into the VCR's tuner circuitry. By taking out the unnecessary infrared components and using the VCR's inherent RF characteristics, the system becomes simpler and more elegant.
3Measurement precision
If return loss channel detection is implemented, then measurement precision of channel tuning is improved, but device complexity increases due to additional detection circuitry
Solution Approach 1:
The VCR's tuner circuitry serves dual purposes: both for signal reception and for channel detection through return loss measurement. The same RF components that receive television signals are used to detect the channel frequency, eliminating the need for separate detection circuitry and maintaining simplicity while achieving high precision.
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 method allows for reliable and automatic channel detection, reducing errors and the need for external transducers, enabling seamless recording of digital video programs and improving user experience.
Implementation Method 1
frequency division multiplexed
Implementation Method 2
tunable bandpass filter
Implementation Method 3
measuring the return loss
Implementation Method 4
measuring reflected power
Data Source
AI summary
Method and apparatus to determine the channel to which a TV tuner is tuned from a return loss ratio measurement circuit in a set top decoder. The method comprises generating a plurality of probe signals having frequencies spread throughput the TV channel band, preferably using harmonics of a zero order hold D/A converter. The return loss ratio of the reflected probe signals is then determined and stored as a signature for the TV channel and the signatures can subsequently be used along with new return loss ratio measurements to determine the TV channel to which a TV or VCR tuner is tuned.