MICROWAVE-10 ANCI

Waveguides

are hollow metal conducting pipes designed to carry and constrain the electromagnetic waves of a microwave signal.

- Most microwave energy transmission above 6 GHz is handled by

Probes and loops

can be used to extract a signal from a waveguide.

waveguide cutoff frequency.

This dimension is usually made equal to one-

half wavelength, a bit below the lowest

frequency of operation. This frequency is known as the

operating mode.

The pattern of the electromagnetic

fields within a waveguide takes many

forms. Each form is called an

Signal Propagation

When a microwave signal is launched

into a waveguide by a probe or loop,

electric and magnetic fields are

created in various patterns depending

upon the method of energy coupling,

frequency of operation, and size of

waveguide.

high frequencies

the angle is large and the

path between the opposite walls is relatively

long.

Signal Injection and Extraction

When the signal strikes a

probe or a loop, a signal is

induced which can then be

fed to other circuitry

through a short coaxial

cable.

transverse electric (TE) field.

In a waveguide, when the electric

field is at a right angle to the

direction of wave propagation, it is

called a

transverse magnetic (TM) field.

When the magnetic field is

transverse to the direction of

propagation, it is called a

choke joint

used to connect two sections of waveguide. It consists of two flanges connected to the waveguide at the center.

- permits sections of waveguide to be interconnected with minimum loss and radiation.

T section or T junction

used to split or combine

two or more sources of microwave power.

Conductance

is the amount of leakage through the dielectric

Coaxial transmission lines

A transmission line in which one

conductor completely surrounds the

other, the two being coaxial and

separated by a continuous solid

dielectric or by dielectric spacers.

center conductor

can be either a solid wire or a

series of wires in a stranded configuration.

outer conductor

serves two functions. It is a

ground reference for the signal on the center

conductor and also is used as a shield.

braid construction

may be single, double, or

triaxial (two braids separated by an insulator). The

single-braid construction consists of bare, tinned, or

silverplated copper wires. The double braid consists

of two single braids with no insulation between

them. The triaxial consists of two single braids with a

layer of insulation between them.

outer coating

provides protection for the cable.

Such protection is mainly environmental. It plays no

part in the electrical performance of the cable.

BNC CONNECTOR

For low power RF signal below 3 MHz; 50 TO 75 ohms

impedance

TNC CONNECTOR

It has a 50 Ω impedance and operates best in the 0–11 GHz

SMA- Sub Miniature Version

From DC to 18 GHz; 50 ohms impedance

N CONNECTOR

 Carries RF signals up to 18 GHz; 50 to 75 ohms impedance

 50 ohms (bottom)

 75 ohms (top)

SEMI-RIGID CABLE

cost considerably more than flexible cables

Strip transmission line

(stripline)

 It evolved from the circular coaxial

device and still has all the original

sections (center conductor, dielectric,

outside shield, and electric fields) but

now is in a form that will operate at

much higher frequencies and be more

efficient for RF and microwave

applications.

Ground-Plane Spacing (GPS)

is the spacing

between the ground planes, or copper on the

circuit boards.

Microstrip

transmission line does

away with the problem of

inaccessibility that stripline poses.

Microstrip transmission line, is

similar to stripline transmission line,

except that there is no top on the

transmission line. There is nothing

but air on top of the circuitry and

a dielectric material underneath

Coplanar waveguide

there is still a

circuit trace on the top of the board that

is a certain width and thickness, but there

are also ground planes on both sides of

the circuit trace and there is no ground

plane on the bottom of the circuit board.

A conductor surrounded by ground

“guides” the electromagnetic wave

down the transmission line.

 It is a modification of the microstrip

circuitry