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Technical Presentation |
RF Coaxial Connectors
An RF Connector is that part
of a transmission system which allows for the coupling or uncoupling of system components,
usually through the use of coaxial connectors.
A simple
way to understand how a coaxial system works is to compare it to a fluid system. In this
system, water must be moved from Point B to Point A. A piece of tubing can be used to
direct the flow of water.
NOTE: There is nothing to impede the flow
of water along the smooth inner surface of the tube, thus, the quantity of water going
into Point A is equal to the quantity of water coming out of Point B.
If, at the
point of connection, the couplings are not
smooth transitions, obstructions can be created;
By offsetting the coupling, the water can flow readily.
There will
still be some resistance to the flow, but it has
been reduced by the offset.
Return to the Coaxial System
Replace
the water with an RF signal or travelling
wave.
Replace the tubing with a Coaxial
Cable.
Replace the coupling with an RF
Connector.
The obstruction in a connector is called a capacitive discontinuity and the offset is what is referred to as compensation.
A CONNECTOR - is a device used to couple
energy into or out of a system. The specific type of
connector we will be addressing is a COAXIAL
CONNECTOR.
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A
Coaxial Connector is comprised of two concentric
conductors which is where the name is derived:
CO-AXIAL. Separated by a dielectric (insulator) and is
most commonly used as an extension of a transmission
line to facilitate interconnection.
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A transmission line is used to guide the propagation of
an electromagnetic wave in one direction and confine
it to prevent the loss of energy.
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The most commonly used transmission line is:
Coaxial Cable
Which is
comprised of an inner conductor, dielectric,
outer conductor and a jacket. There are two common
types of coaxial cable.
Coaxial Cable
A. Flexible, which has a braided outer conductor.
B. Semi-rigid, which has a solid
outer conductor.
Notice how a coaxial cable guides the propagation of an
electromagnetic wave:
What then is this technology?
Return to the fluid system, and replace the tubing with a coaxial cable and replace the water with a signal.
The signal
will have to move down the center conductor
from B to A and is contained by the dielectric.
To move the signal along the path a force "voltage" must be exerted by a signal generator or power source. The signal forms a "Sine Wave". The distance covered in 1 Cycle is called the "Wavelength".
The number of cycles per second is called the "frequency" of the wave. The unit of one cycle per second is called a "Hertz" (Hz). Some commonly used abbreviations follow:
1 Cycle Per Second = 1 Hz
1,000 Cycle
Per Second = 1 KHz (Kilohertz)
1,000,000 Cycle Per Second = 1 MHz (Megahertz)
1,000,000,000 Cycle Per Second = 1 GHz (Gigahertz)
Where a system is terminated with other than it's natural impedance. Within a connector the change in line size, which for physical reasons creates an impedance mismatch which must be compensated.
Notice dimensional differences between cable dielectric and connector insulator.
Notice dimensional differences between cable center conductor and connector center contact.
RF Leakage - A measure of the RF energy loss due to gaps in the mechanical containment of the electromagnetic field. This energy is radiated out.
Coaxial Cable and Connectors always have the same basic components:
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1. Center contact is affixed to the center conductor as an
extension of the signal path. 2. The connector insulator butts against the cable dielectric as an extension of the insulator. 3. The connector body is affixed to the braid or strength member of the cable as an extension of the ground path. 4. Outer jacket is a protective covering against environmental conditions. |
Connectorization of coaxial
cable always has the
same basic affixment procedures.
