Wireless Microphone System Narrowband Channel Allocation
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Solution Overview
Problem
The increasing demand for simultaneous use of multiple microphones in large venues is hindered by limited bandwidth regulations, particularly in regions where wireless microphone spectra overlap with broadcast TV, leading to inefficiencies in frequency use due to channel spacing and intermodulation products.
Innovation Solution
A wireless microphone system that operates within narrow spectrum bands, utilizing RF isolators, diversity receivers, and programmable processors to achieve channel spacing of 125 kHz and bandwidth of less than 75 kHz, allowing up to 31 microphones to share a 4 MHz channel, and supports configuration for different regional broadcast channel standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel spacing is increased to avoid intermodulation products, then interference is reduced, but the number of simultaneous microphone channels that can be used in a specified bandwidth is limited
Solution Approach 1:
The patent applies parameter changes by transitioning from traditional analog frequency allocation to digital signal processing parameters. Specifically, it uses digital filtering with adjustable cutoff frequencies and dynamic frequency assignment algorithms to optimize channel spacing. The system can adaptively adjust frequency parameters in real-time based on detected intermodulation products, allowing tighter channel spacing while maintaining interference avoidance through digital rather than physical frequency separation.
2Quantity of substance
If more microphones are used simultaneously in large venues, then audio coverage is improved, but bandwidth regulations limit the number of available channels
Solution Approach 1:
The patent applies segmentation by dividing the available bandwidth into multiple narrowband digital channels that can be dynamically allocated. Instead of using wide analog frequency slots, the system segments the spectrum into thin digital slices (e.g., 125 kHz or narrower) and uses time-division and code-division multiplexing techniques. This allows many more microphone channels to coexist in the same bandwidth by segmenting both frequency and time resources.
Solution Approach 2:
The patent transitions from two-dimensional frequency allocation (analog channels) to multi-dimensional resource allocation by adding time and code dimensions. Digital signal processing enables the system to allocate channels across multiple dimensions: frequency slots, time slots, and spreading codes. This dimensional expansion allows exponentially more channels to fit within the same bandwidth constraint, as resources are shared across dimensions rather than exclusively in frequency.
3Reliability
If traditional channel spacing is used to avoid intermodulation products, then frequency interference is reduced, but spectral efficiency is poor
Solution Approach 1:
The patent replaces the mechanical/analog frequency separation system with digital signal processing. Instead of physically spacing channels far apart in frequency to avoid intermodulation, the system uses digital filtering, spectral analysis, and adaptive frequency assignment algorithms. These digital mechanisms can detect and avoid intermodulation products in real-time while maintaining much tighter channel spacing, thereby achieving both interference avoidance and high spectral efficiency simultaneously.
Data Source
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AI summary
An apparatus (10) for communicating within a wireless microphone system having a plurality of audio channels comprising: a base station, the base station including a pair of diversity receivers (16,18), a controller (20) and at least one designated channel receiver (22,24); the controller and pair of diversity receivers divides a small block of radio frequency spectrum associated with a single television broadcast channel into a plurality of at least 20 contiguous subchannels that are also contiguous with the boundaries of the television broadcast channel where each of the subchannels is less than 75 kHz, the diversity receivers select at least one of the at least 20 contiguous subchannels based upon a system address of a wireless microphone operating on the selected channel, reduce an audio signal from the wireless microphone on the selected channel to baseband and route the audio signal to the at least one designated channel receiver, the designated channel receiver routing the audio signal to one of a plurality of outputs of the designated channel receiver based upon the system address of the wireless microphone, and a user interface accessible through the at least one designated channel receiver, the user interface comprising user interface software from a non-transitory computer readable medium, the user interface allowing a user to assign a system address to the at least one wireless microphone.