Network interface connectors are components of networking active equipment such as routers, switches, controllers and network interface cards. Only the mateable interface geometry proper of these connectors is covered by the modular connector standards.
The transmission properties of these connectors usually vary depending upon the printed circuit board (PCB) impedance and other components utilized in the active networking equipment printed wiring boards. For these reasons the transmission properties, while being critical for the equipment functionality, are not covered by U.S. or international standards, but are defined by each equipment manufacturer based on its own system experimental evaluation.
Network interface connectors require designers to address and solve a combination of unique transmission parameters as well as other limitations common to modular connectors. These include:                Low profile,        Variable transmission parameters to be tuned from one application to another. The major transmission parameters are:                    Near End Cross Talk (NEXT),            Return Loss, and            Common Mode Noise,                        Completely self-contained compensation for e.g., NEXT, return loss, and common mode noise and        Multiport or single port, shielded or unshielded with condition - indicating light emitting diodes (LEDs).        
Network equipment providers market a large variety of appliances for 10/100 MbE, 1 GbE and 10 GbE. Network interface connectors are integral parts of these appliances. The application market requires both single port and multiport connectors. The connectors are soldered to multi-layer motherboards together with other components such as PHY, resistors, magnetics, capacitors, etc.
Moreover, network applications require smaller and denser designs because, in part, the motherboard PCBs are multilayer and expensive.
Conventional techniques for enhancing the transmission performance of connectors on a motherboard PCB can be very costly. An RJ45 standard connector is often the tallest component on the PCB—so its height over the PCB needs to be reduced without sacrificing the standard dimensions.
While the outline and dimensions of modular connectors are subject to U.S. and international standards such as IEC 600603-7 and TIA 568 series, the internal designs of connectors differ widely.
The desired transmission properties of these connectors usually vary depending upon the Physical Layer (PHY) input impedance and other components utilized in the active networking equipment printed wiring boards.
Typical transmission requirements commonly referred to as categories (category 5e is characterized up to 100 MHz, category 6 up to 250 MHz and category 6a up to 500 MHz) are used as guidelines only.
The networking companies must have connectors of the same physical dimensions but be able to accommodate any one of a variety of options in transmission response. Moreover, the electrical response should differentiate for various transmission speeds. It is desirable for connectors, of identical appearance and footprint, provide matched electrical response for 10/100 Mbe, 1 GbE or 10 GbE chipsets. Presently, connectors are designed for specific issues such as a given common mode noise at a given frequency for a specific PHY.
The performance of a connector is judged by either direct measurement of the transmitted signals or by controlling the major transmission parameters such as NEXT, Return loss and Common mode noise and Common to Differential mode conversion. These parameters are specified in the US in TIA 568-10 and internationally in the IEC 60603-7 standard series.
Low profile RJ45 connectors are known and are used as network interface connectors. Their interface geometry is still governed by the TIA 568 and IEC/ISO 60603-7 series of standards. However network interface connectors are not parts of the channel as defined by the standards.
Since the location of the PHY and/or other components in the channel, such as magnetics (filters and isolation transformers) and discharge capacitors, distorts the NEXT and Return Loss (RL), the requirements for NEXT and RL compensation differ from application to application. In order to meet such requirements connector manufacturers supply different connectors to work with specific PHYs.
The transmission performance of RJ45 type network interface connectors is enhanced by internal compensation such as by providing compensation circuitry on an internal PCB or on flexible circuits. The connector contacts are soldered to the internal PCBs.
Presently, it is not feasible to enhance or modify the transmission characteristics of such connectors after they are soldered to the motherboard.
Tests of connectors are conducted using the exact network equipment and PHY specific to the application. In order to tune the performance for a particular application, connectors have to be de-soldered and removed from the motherboards, re-assembled or discarded and new connectors used. If a problem is found in the field, often the complete network installation has to be re-placed or scrapped.
It would be advantageous to be able to modify, upgrade or change the transmission characteristics and performance of a network interface connector after it has been soldered to a motherboard.