Radio Frequency (RF) & Wireless Design

The N-Type Coaxial (Coax) connector has been popular for many years and is well known :https://en.wikipedia.org/wiki/N_connector

This connector should almost always be used in place of the common UHF connector, unless the frequency is under 10 MHz. The N-type connector is the middle choice between the BNC (rated at 4 GHz) and the SMA (rated at 18 GHz +). It is a competitor to the Threaded BNC called the TNC connector that is rated up to 11 GHz.

The N-Type connector comes in many frequency ranges starting at 2 GHz and typically is rated to 11 GHz, however there are a few select varieties that will go up to 18 GHz. Its important to check the frequency bandwidth that is on all the documentation to make sure that the connector you choose has the lowest loss.

Typically the higher the frequency range the lower loss on frequencies below the rating. All rated frequencies are at the -3 dB power point which is at a 50% loss of power, so you really don't want to go up to the limit ! Leave plenty of frequency margin and you will get lower losses and better power transmitted.

There are also many varieties of this common connector that most people are not aware of. The most basic types are based upon the coax impedance of either 50 ohms or 75 ohms.

Beyond that there are the many mounting options as :

• Cable Mount (typically to connect cables)
• Panel Mount (may or may not have flanges)
• Bulkhead Mount (is screwed into metal - no flanges)
• Flange Mount (uses screws to mount)
• PCB Mount (typically vertical or right angle)
• PCB Edge Mount (mounts to various PCB thicknesses)

With the Panel, Bulkhead, or Flange mounts there are waveguide extended insulation options with various center pin diameters as well as the insulation diameters. Then follows the insulation length and the center pin length. These are useful for very high frequencies up to the 18 GHz range.

There are (5) basic center pin termination types :

• Crimp (usually for braided shield of coax cable types, sometimes with the pin soldered)
• Solder (usually just a round pin typically to an antenna, includes extended insulation)
• Solder Cup (this is for long pins or bridging to a PCB)
• Solder Tab (this is for direct attachment to a PCB)
• Gap (this is to attach a sheet metal patch)

The other thing to watch out for with Flange Mounts is that although they may seem to be the same at first glance, there are two different flange types : those that are 25.4mm (1.0") wide flanges with 18.2mm hole spacing, and those with 17.5mm wide flanges with 12.7mm (0.5") hole spacing.

Typically the material is cut to the diameter of the waveguide insulation diameter and then the insulation length is cut to just inside the waveguide cavity. The center pin is usually cut to the 1/4 wavelength of the center frequency of the waveguide.

There are also both external and internal sealing arrangement options for outdoor weather and moisture sealing. flange mounts have an O-ring seal and others may have a seal on the face of the connector.

Plating options are typically silver as the best conductor, but gold, nickel, stainless steel, and other passivates are also available.

One of the most important options is making sure that the connector matches the coax that you will be using ! Many of the N-type connectors support about 30 options for cables and the mechanical details, although subtle, are critical for getting the correct impedance match. So after choosing the correct impedance, its probably a good idea to match the cable type before choosing any other options.

After that, its important that *both* plug and socket are from the same manufacturer to ensure the tightest degree of tolerance which also reduces EMI emissions.