WLAN Clock Signal Selection for RF Sensitivity
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Solution Overview
Problem
Wireless Local Area Network (WLAN) radio modules experience noise and interference due to clock signals generated by clock sources and carried on PCI buses, which reduce receive sensitivity and affect RF signal processing.
Innovation Solution
A radio frequency device with a WLAN radio module, a bus, a lookup table (LUT), and a processor that selects between two clock signals to drive the bus, based on the operating WLAN channel, to minimize interference by choosing a clock signal that does not harmonically interfere with the channel in use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single clock source is used to drive the PCI bus, then the device complexity is reduced, but noise and interference occur at the WLAN radio module when operating on certain channels
Solution Approach 1:
The system dynamically selects between different clock sources based on the operating WLAN channel. The processor monitors which channel the WLAN radio module is using and switches the clock source accordingly, making the clock configuration adaptive rather than static. This resolves the contradiction by allowing the system to maintain low complexity overall while dynamically adjusting to avoid interference on specific channels.
Solution Approach 2:
The invention changes the clock frequency parameter based on the WLAN channel in use. Different clock frequencies are selected depending on which WLAN channel is active, ensuring that clock harmonics do not coincide with the operating channel frequency. This parameter adjustment eliminates interference while maintaining system simplicity through automated selection.
2Ease of operation
If the clock source is placed close to the WLAN radio module, then the ease of operation is improved, but the clock signal causes noise and interference
Solution Approach 1:
By changing the clock frequency parameter based on the operating channel, the system maintains the close physical placement of the clock source while avoiding harmonic interference. The frequency adjustment ensures that even though the clock signal is strong and close to the radio module, its harmonics do not coincide with the WLAN operating frequencies, thus eliminating interference while preserving signal strength benefits.
3Adaptability or versatility
If channel switching is implemented, then the adaptability is improved, but the receive sensitivity is reduced due to clock interference on certain channels
Solution Approach 1:
The system implements dynamic clock source selection that automatically adapts to the current WLAN channel. When the WLAN radio module switches channels, the processor detects this and switches to an appropriate clock source that will not interfere with the new channel frequency. This dynamic adaptation maintains high receive sensitivity across all channels by ensuring clock harmonics never coincide with operating frequencies.
Solution Approach 2:
The system uses feedback from the WLAN channel selection to control clock source switching. The processor monitors which channel is currently active and uses this information to select the appropriate clock source, creating a closed-loop system that maintains optimal receive sensitivity regardless of which channel is in use.
Data Source
AI summary
Techniques are provided for selecting one of a plurality of clock signals used to drive a bus of a WLAN-enabled device having a WLAN radio module coupled to the bus and designed to operate over a plurality of WLAN channels. A network infrastructure device, such as an access point or port, is provided that comprises a WLAN radio module, a PCI bus coupled to the WLAN radio module, a look up table (LUT) and a processor. The WLAN radio module designed to operate over a plurality of WLAN channels in a first frequency band. The LUT comprises a plurality of entries. Each entry comprises: a particular one of the WLAN channels and a corresponding one of a first clock signal having a first clock frequency and a second clock signal having a second clock frequency that is to be selected. The first clock signal causes interference at the WLAN radio module when operating over a first subset of the WLAN channels, and the second clock signal causes interference at the WLAN radio module when operating over a second subset of the WLAN channels. The processor selects, from the LUT based on the one of the WLAN channels that has been selected for the WLAN radio module to communicate over, either the first clock signal or the second clock signal that is to be used to drive the bus.