Array-Reader Magnetic Recording With Quadrature Amplitude Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic recording systems face challenges in efficiently multiplexing signals from an array-reader, particularly in reducing inter-track interference and increasing throughput, while also minimizing the number of flex cables and analog circuitry required.
Innovation Solution
The implementation of quadrature amplitude modulation (QAM) in an array-reader based magnetic storage system, which combines two channels of signals into one with double the bandwidth, allowing for signal processing using fewer flex cables and analog circuits, and includes a joint equalizer to improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple separate channels are used to read data from multiple tracks, then data throughput and noise compensation are improved, but the number of flex cables and analog circuitry increases
Solution Approach 1:
The patent combines multiple reader channel outputs into a single multiplexed signal using frequency division multiplexing. Each reader channel is modulated onto a different carrier frequency, and all channels are summed into one output signal that travels through a single flex cable to the analog front end, reducing the number of cables and analog circuits while maintaining multiple data streams
Solution Approach 2:
The patent transitions from spatial multiplexing (separate physical channels) to frequency domain multiplexing. By assigning different frequency bands to different reader channels, the system maintains multiple independent data paths without requiring separate physical cables, effectively adding a frequency dimension to the signal transmission
2Reliability
If array-reader with multiple read heads is used, then inter-track interference is reduced through noise compensation, but signal processing complexity increases
Solution Approach 1:
The patent uses multiple read heads that simultaneously read the same data track at different lateral positions. These redundant readings are processed through the multiplexing system and combined at the digital signal processor, which can then optimally combine the signals to reduce inter-track interference and noise while maintaining the same data output
3Productivity
If more analog front end circuits are used to process signals from multiple channels, then signal processing capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces multiple analog signal processing paths with a single analog front end that handles a multiplexed signal. The separation and processing of individual channels is moved to the digital domain, where a digital signal processor can efficiently handle multiple channels without requiring proportional increases in analog circuit complexity
Solution Approach 2:
The single analog front end circuit is designed to process the multiplexed signal containing multiple frequency-modulated channels. This universal analog stage performs initial amplification and filtering for all channels simultaneously, replacing the need for multiple dedicated analog circuits while maintaining full signal processing capability
Data Source
AI summary
A magnetic recording system includes an array of analog inputs operable to receive analog signals retrieved from a magnetic storage medium, a quadrature amplitude modulator operable to combine the analog signals to yield a quadrature amplitude modulated signal, a quadrature amplitude demodulator operable to yield a plurality of demodulated signals from the quadrature amplitude modulated signal corresponding to each channel of the array, and a joint equalizer operable to filter the plurality of demodulated signals to yield an equalized output.