Technology: Interferers

Wireless LANs based on the IEEE 802.11 standards function in the unlicensed 2.4 and 5 GHz frequency bands.  Other devices emitting radio-frequency energy in these bands can interfere with WLAN transmissions.  Below is a list of some common RF interferers and their RF characteristics.

Bluetooth Device

Bluetooth is a frequency hopping wireless communications technology.  As shown below in the scrolling spectrogram display, the Bluetooth device (the red/yellow energy squares) hops across the full 2.4 GHz Wi-Fi frequency band.  This is easily seen in the scrolling spectrogram display, but more difficult to see in spectrum analyzer displays (top chart) which show only frequency and amplitude information but limited time-domain information.

Radio Frequency Characteristics:
Frequency Range: 2402-2480 MHz
Transmit Power: 2.2dBm
Modulation: GFSK, FHSS
Number of Communication Channels Supported: 79
Width of Communication Channel:  1 MHz
Features: Pulsed, low-power

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Analog Cordless Phone

Analog cordless phones are wireless devices that use narrowband frequency modulation for transmission. These are easily seen in both the spectrum analyzer display and the scrolling spectrogram display (see below).

Radio Frequency Characteristics:
Frequency Range: 2402-2480 MHz
Transmit Power: 0 dBm
Modulation: Narrowband Frequency Modulation (FM)
Number of Communication Channels Supported: 40
Width of Communication Channel: ~300kHz
Features: Narrowband Frequency Modulation (FM)

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DSSS Digital Cordless Phone (DSSS = Direct Sequence Spread Spectrum)

DSSS Digital cordless phones are pseudo continuous wave devices.  These are easily seen in both the spectrum analyzer display and the scrolling spectrogram display (see below).

Radio Frequency Characteristics:
Frequency Range: 2407.5-2472MHz
Transmit Power: 20 dBm
Modulation: DSSS
Number of Communication Channels Supported: 40
Width of Communication Channel:  1.5 MHz
Features: High power and duty factor

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FHSS Digital Cordless Phone (FHSS = Frequency Hopping Spread Spectrum)

FHSS Digital Cordless phones are frequency hopping devices.  As shown below in the scrolling spectrogram display, the FHSS phone (the red and yellow energy squares) hops across the full 2.4 GHz Wi-Fi frequency band.  This is easily seen in the scrolling spectrogram display, but more difficult to see in spectrum analyzer displays (top chart) which show only frequency and amplitude information but limited time-domain information.

Radio Frequency Characteristics:
Frequency Range: 2407.5-2472 MHz
Transmit Power: 21 dBm
Modulation: FHSS
Number of Communication Channels Supported: 90
Width of Communication Channel:  892 kHz
Features: Pulsed, high-power

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Conventional Microwave Oven

Conventional microwave ovens unintentionally radiate RF energy and interference in the 2.4 GHz Wi-Fi band, as shown below.

Radio Frequency Characteristics:
Frequency Range: 2.4 GHz
Transmit Power: 800W
Modulation: N/A
Number of Communication Channels Supported: N/A
Width of Communication Channel:  N/A
Features: Pulsed, broadband

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Inverter Microwave

Inverter microwave ovens unintentionally radiate RF energy and interference in the 2.4 GHz Wi-Fi band, as shown below.

Radio Frequency Characteristics:
Frequency Range: 2.4 GHz
Transmit Power: 1300W
Modulation: N/A
Number of Communication Channels Supported: N/A
Width of Communication Channel:  N/A
Features: Pulsed, broadband

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Wireless Video Camera

Wireless video cameras operating in the 2.4 GHz band are high-power, frequency modulated devices that are visible on both the spectrum analyzer display and the scrolling spectrogram display.

Radio Frequency Characteristics:
Frequency Range: 2414 - 2468 MHz
Transmit Power: 10 dBm
Modulation: Frequency Modulation (FM)
Number of Communication Channels Supported: 4
Width of Communication Channel:  N/A
Features: Broadband, high-power

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Digital Video Monitor

Digital Video Monitors operating in the 2.4 GHz band are high-power, frequency hopping devices that are visible on both the spectrum analyzer display and the scrolling spectrogram display.

Radio Frequency Characteristics:
Frequency Range: 2402 – 2483 MHz
Transmit Power: 20 dBm
Modulation: Frequency Hopping Spread Spectrum (FHSS)
Number of Communication Channels Supported: 27
Width of Communication Channel:  2 MHz
Features: High power, frequency hopping

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Game controller

Game controllers operating in the 2.4 GHz band are low-power, frequency hopping devices that are visible on both the spectrum analyzer display and the scrolling spectrogram display.

Radio Frequency Characteristics:
Frequency Range:   2402 – 2482 MHz
Transmit Power:   0 dBm
Modulation: Frequency Hopping Spread Spectrum (FHSS)
Number of Communication Channels Supported:  40
Width of Communication Channel:   500 kHz
Features: Pulsed, low-power, frequency hopping

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