What is tangential loss, is its significance, while selecting any dielectrica materia

Dear Sir,
Please let me, what is tangential loss of any dielectric material. What is its significance,while selecting any dielectric material. What is the exact meaning of tangential loss. If it is more tangential loss of any dielectric material, what does it mean ?. If it is less tangential,what does it mean ?
Can you make it clear anybody.

if a material acts somewhat like a dielectric material, then you can approximate its response to microwaves as having a dielectric constant and a loss component. The dielectric determines what the physical wavelength at a single frequency will be. The loss tangent tells you how quickly the RF wave will attenuate itself as it moves along the material. It is useful, for instance, if you want to run a coaxial cable from a transmitter to an outdoor antenna 1000 feet away....the loss tangent of the material in the cable (along with resistive loss in the metal) will tell you how much of the transmit power will arrive at the antenna. The rest of the power just heats up the cable.

Another use is if you want to make a resonator filter....the sharpness of the filter's roll off, and the insertion loss at mid frequency, may be primarily determined by the dielectric loss tangent

[QUOTE=biff44;1317948]The loss tangent tells you how quickly the RF wave will attenuate itself as it moves along the material.

Dear Sir,
Why it is called "tangential" loss. Simply it may be called as attenuation loss. Why it is specifically called as a "tangential" loss.
For some material you can take as a example
For RT/ Duroid dielectric Tangential loss is 0.0009, For FR4 dielectric Tangential loss is 0.023. Some dielectric materials are having more tangential loss, some dielectric materials are having less tangential loss . What does it mean.If it is more tangential loss, what we have to understand. If it is less tangential loss, what we have to understand.

if you view the propagation constant as a vector quantity, the angle of the vector describes the propagation and the loss. Hence the "tangent" reference



check this out:
http://en.wikipedia.org/wiki/Propagation_constant

There might be some confusion. tand = loss factor= 0.0009 (or for example 0.023 for FR4 at a certain frequency). tand = (dielectric) loss factor, but is not tangential loss.

Dielectric loss of a material is mostly expressed as tand (or e' with e'', where tand = e''/e'). When you make a microstrip, both copper and dielectric loss adds to the microstrip attenuation. tand is tan(delta), where delta is the loss angle.

When you make a capacitor (all field lines go through the dielectric) of a material that has tand = 0.023, then the capacitor will have a loss resistor in series with

Rs.loss = 0.023*Xc,

Or in a parallel equivalent circuit

Rp.loss = Xc/0.023

Xc = 1/(2*pi*f*C).

In real world frequently part of the E-field is outside the dielectric and then the effective relative epsilon and effective loss tangent (tand) is less. This is also valid for microstrips as part of the E-field is above the PCB material.

Transmission line loss is proportional with rt(epsilon.relative)*freq*tand (assuming tand<<1).