Filter Connectors

Advantages of Filter Connectors
The integration of the filter elements into the connector, rather than a board level solution, results in many advantages to the user:
• reduction in space and weight
• reduction in inspection and assembly labour
• improved high frequency EMI performance by elimination of parasitic effects associated with board level filters
• superior shielding effectiveness
Filter Connector Design Filter connectors have been used for over thirty years to provide cost and space effective solutions to EMI problems in a wide range of military and commercial applications including avionics systems, satellites, missiles, communications, control systems and tempest equipment. A low pass filter connector incorporates capacitors and ferrite inductors into the connector body. The two capacitor types commonly used in filter connectors for military or avionics applications are planar arrays and tubular capacitors. Each of these capacitor types is an efficient filter at high frequencies (> 1 GHz) and has been proven to be extremely reliable when suitably assembled into a connector. Both planar and tubular designs feature Amphenol’s unique solderless construction which reduces stress on the ceramic elements and results in superior physical and thermal shock capabilities.
Planar Array Amphenol Canada’s planar design consists of planar ceramic capacitor arrays and discrete ferrite inductors assembled concentrically over the contacts and into the connector shell. The planars are compressed between rubber gaskets and have contact springs in each position which form a stress isolated connection with the contact body. The planars are grounded to the shell via a ground spring. Tubular Capacitor Amphenol Canada’s tubular design consists of a ferrite bead and ceramic tubular capacitor assembled onto a machined contact. The filter tube is connected to the contact with conductive rubber washers to provide a stress-isolated contact assembly. Grounding is achieved via a ground plate. These are typically used when the filter elements within the connection require more than a single dielectric material ie. NPO and X7R.
Filter Connector Selection Selection of a particular filter circuit will depend on the required insertion loss characteristics and the system source and load impedances. By arranging the capacitive and inductive elements in a variety of combinations a number of equivalent circuits may be attained. The ferrite elements always face the low impedance side of the filter. These filter types are available in a wide range of capacitance and voltage values and may be selected in virtually any combination within the connector insert. In addition to filter contacts, insulated contacts, ground contacts and sealing plugs are available.
The following factors may affect the filter performance, and should be considered when selecting a filter connector and Amphenol takes these into account when designing your filter solution.
Operating Voltage
As a DC voltage is applied across a capacitor, the dielectric constant decreases, resulting in a capacitance decrease and a reduction in filter performance. The magnitude of the change is dependent upon the type of ceramic material used, the dielectric thickness and the magnitude of the voltage applied.
Operating Currents
Operating currents cause magnetic saturation of inductive elements (ferrites). Therefore filters with ferrite inductors (Pi, CLR, LRC and T) will perform much like C filters as the ferrite approaches saturation. The satura- tion point can vary by ferrite characteristics and size but typically occurs above 0.1 mA.
Operating Temperature
Range Capacitance and insertion loss performance are shown at 25˚C. Depending on the type of ceramic material being used, capacitance can drop based on dielectric being used at  temperature extremes. However, commonly used dielectrics have temperature coefficients of +/- 15% from -55˚C to +125˚C. Transient Voltage Requirements
Some transient voltage requirements may necessitate the addition of diodes or MOV’s to the PCB or in the connector.

EMI Filter Protection Connectors

Amphenol now offers a quick 2-week turnaround on their most popular  filtered receptacle connectors - jam nut and wall mount 38999 Series III in the double density -35P (pin) Mil-spec insert arrangement. These filter receptacles are ideal for quick prototypes and support of  MIL-STD-461 system level EMI protection requirements.
Amphenol® EMI/EMP Protection Connectors have been designed in and manufactured for over 45 years.  Our EMI/EMP protection  connectors offer the versatility of our standard connectors with  EMI/EMP protection to suit the demands of your application.