Guide to Connectors

Document History

Created 2005-2-17: John Danson

Document Outline

Connector Overview
Connector Care
Links

Connector Overview

There are several types of connectors used in the load pull setup:
- SMA
- 3.5mm
- K (2.92mm)
- 7mm (APC-7)
- N
- BNC
Incorrectly mating these connectors can cause PERMANENT DAMAGE.

Different types of connectors used in the Carleton Load Pull system
Connector Name	Matable With:	Male	Female	Max. Operating Frequency (GHz)	Tightening Torque (inch-lbs)
BNC	N/A			2	N/A
N	N/A			18	12 (finger tight also acceptable)
7mm (APC-7)	N/A	(sexless)		18	12 (finger tight also acceptable)
SMA	3.5mm, K (2.92mm)			18 (sometimes 24)	5 (when connecting SMA to 3.5mm use torque for male connector)
3.5mm	SMA, K (2.92mm)			34	8 (when connecting SMA to 3.5mm use torque for male connector)
K (2.92mm)	SMA, 3.5mm			40	8
3.5mm Test Port Adapter (for the VNA)	N/A			???	???

Connector Care

An excellent guide to connector care can be found here: Microwaves101: Connector Care

Mating
- Care must be taken when mating SMA, 3.5mm and K (2.92mm) connectors as well as 7mm connectors.
- SMA connectors are a lower quality connector that uses a dielectric spacer between the ground sleeve and the center pin. The SMA connector is designed for infrequent connections and support a limited number of connections. There are quite a few of them around, mainly because they are much cheaper than precision connectors.
- 3.5mm and K (2.92mm) are precision connectors that use an air spacer between the ground sleeve and center pin. These precision connectors are designed to support thousands of connections. K (2.92mm) connectors are found on the probes because they operate up to 40GHz. Most other connections of this size in the system are 3.5mm or SMA.
- The depth of the pin in SMA connectors is different than 3.5mm and K (2.92mm) precision connectors. The precision connectors have been designed to avoid breaking the male pin or female socket when the two connectors are being mated and are not perfectly aligned.
- To avoid breaking the precision connectors when mating with an SMA connector, the interfaces must be very carefully aligned prior to being pushed together.
- The 7mm connectors should be mated such that only one of the knurled sleeves is tightened. See below for more information.
- When mating any of these connectors, do not spin the conductor. Only the sleeve on the connector should turn.
- Finally, a torque wrench should be used to avoid overtightening and to guarantee a repeatable connection.

7mm Connectors
- These connectors form the main interface of several parts of the load pull system. They have several advantages in that they offer repeatable connections into the thousands of connections, and they are sexless connectors.
- The compressible center pin is the key feature that allows these connectors to be sexless. When not connected, this pin protrudes as shown below. When mated with another connector, this pin presses against the opposing pin to make the electrical connection.
- The center pin may be split into 4 or 6 fingers. The Maury field service rep. indicated that the 6 finger connectors are higher quality.
- Since this center pin protrudes past the ground, it is critical that 7mm connectors be left with the outer threaded sleeve extended when not attached to another connector. This prevents damage to the center pin.
- When mating 7mm connectors, one of the sleeves should be fully extended while the other is fully retracted. Turn the knurled sleeve (or nut) of the retracted connector onto the extended connector. Only one sleeve should be tightened - the other should be loose.

Cleaning
- Dirty connectors can degrade or even damage the cables they are connected to. They can also be the source of calibration and measurement errors. If you are having difficulty obtaining a calibration on the VNA, make sure the connectors are clean.
- Connectors can be cleaned with cotton swabs and alcohol (see the Connector Care link above).

Links