Electromagnetic interference is a primary cause for a device's failure to communicate. When high data rate differential graphics signals are transferred through a connector, the contacts radiate electromagnetic fields like an antenna. As the speed of the data rates continues to increase, then the radiating frequency of the noise from the graphics connector also increases.
Enhanced shielding designs of the graphics connectors like the I-PEX CABLINE-CA II Micro-Coaxial Cable Connector (accepts co-axial wire sizes up to AWG36 with controlled impedance of 45 ohms) and the I-PEX NOVASTACK 35-HDP Shielded Board-to-Board FPC Connector (accepts FPC [flexible printed circuit] on the plug connector and rigid PCB on the receptacle connector) have added shielding that eliminates the unwanted, radiated noise.
The noise from the unshielded graphics connector effects wireless communications called Long Term Evolution (LTE) that are enabling the Internet of Things (IoT) marketplace. LTE is controlled by the 3rd Generation Partnership Project (3GPP) which united seven telecommunications standards. For example, it covers all GSM (including GPRS and EDGE), W-CDMA (including HSPA) and all LTE specifications.
Two types of LTE are available: the paired LTE-FDD uses Frequency Division Duplex paired spectrum techniques. For example, the uplink band 10 MHz wide at 2.6 GHz and a paired 10 MHz wide band at 2.72 GHz require two 10 MHz wide frequency bands. The unpaired LTE-TDD uses Time Division Duplexing and requires only one frequency band that switches up and down taking turns like when playing tennis and is allowed to vary the up/down ratio.
Some spectrum (frequencies) are licensed (paid) where the operator has exclusive rights for a certain frequency range which is used by LTE and other cellular systems since the operator can control the interference of that frequency range.
Unlicensed spectrum is free, but open to all and crowded causing unpredictable interference. To expand coverage the operator may use a combination of both licensed and unlicensed spectrum.
An example of possible predicted interference: the paired LTE-FDD example uses two frequency bands: Uplink Band - 2.6 GHz, Downlink Band - 2.72 GHz.
Now consider that the new device designs use 4K2K resolution displays driven by 4-Lanes of eDP differential lanes at 5.4 Gbps. The primary radiated emissions expected from the 5.4Gbps graphics data differential lanes is at their Nyquist frequency of 2.7 GHz which is the same as the LTE-FDD Downlink frequency of 2.72GHz. We can expect that they will interfere with each other if they are not isolated from each other.Examples of protocols and Nyquist frequencies are as follows:
LTE has many carrier frequencies and bandwidths so as to serve a multitude of applications (IoT). The LTE carrier frequencies closest to the graphics connector Nyquist frequencies have the highest chance for interference. Some popular LTE carrier frequencies around ~700~800 MHz and 2.4 GHz are disrupted by a USB 3.0 embedded graphics connector that "leak" electromagnetic noise fields. The LTE carrier does not have the option to look for a better, cleaner frequency channel like WiFi that can hop from frequency channel to frequency channel until an acceptable clear channel with adequate signal strength is found.
Wireless WiFi Carrier Frequencies are defined by IEEE 802.11b and 802.11g standards use the unprotected 2.4 GHz frequency band. The 802.11a standard uses the 5 GHz frequency band. Because they operate in unregulated frequency bands, 802.11b and 802.11g equipment suffers interference from microwave ovens, cordless phones, and other appliances using the same 2.4 GHz ISM band.
The 2.4 GHz band is the most widely used spectrum of the bands available for WiFi. Used by 802.11b, g, & n., it can carry a maximum of three non-overlapping channels. The 5 GHz band or 5.8 GHz band provides additional bandwidth, and being at a higher frequency, although usage is not as popular, therefore interference is less. It can be used by 802.11a & n. and it can carry up to 23 non-overlapping channels, but the shorter wavelength provides a shorter range than 2.4 GHz.
The extra shielding of the connectors enables the device designers the flexibility to locate the graphics connector and radio components near each other as smaller device space requirements become even more critical.
I-PEX CABLINE-CA II and I-PEX NOVASTACK 35-HDP
