Or Q= does not have result power / power of have rendered great service, or those who call character impedance and loop resistor than.

 

Q cost is higher, loss is smaller, efficiency is taller;

 

Q cost is higher, the frequency stability of resonator is taller, accordingly, can more accurate.

 

How to understand Q value and ESR value to evaluate high frequency the index of a main function that sticks a capacitor is quality factor Q, perhaps establish ties with the equivalent related its resistor (ESR) .

 

Theoretic, the capacitor of perfect ” of a “ should behave what be sex of 0 ohm, pure capacitive reactance for ESR not to have impedance component. Why to plant no matter frequency, as it happens can shift to an earlier date than voltage when electric current passes capacitance 90 degrees phasic. Actually, capacitance is faulty, can put in the ESR of fair value more or less. The ESR of a specific capacitance changes as the change of frequency, and be equality concerns.

 

Because the origin of ESR is the structural character of the character of electric electrode structure and insulation medium,this is. Change an analysis for the model, regard ESR as individual series connection parasitism yuan. In the past, all capacitance parameter are measure below the standard frequency of 1MHz, but current it is a more high frequency world, the condition of 1MHz is far insufficient. The model that the high frequency capacitance with one can outstanding individual character gives out joins numerical value to should be: 200MHz, ESR ＝ 0.04Ω ; 900MHz, ESR ＝ 0.10Ω ; 2000MHz, ESR ＝ 0.13Ω . Q value is number of key link of a boundless, the reactance that capacitance is equal to on numerical value is divided with parasitism resistor (ESR) . Q value changes along with frequency and have very big change, because reactance and resistor change as frequency,this is. Frequency or the change of the capacity can make reactance is having very big change, because this Q is worth,also meet the change with very big ensue.

 

Define the quality factor of capacitance, namely Q value, namely of capacitance store of power and loss power than:

 

Qc=(1/ωC)/ESR

 

 

Q value is more important parameter to high frequency capacitance.

 

From syntonic frequency (Self-Resonance Frequency)

 

As a result of the existence of ESL, made a syntonic circuit together with C, its resonance frequency is capacitance from syntonic frequency. Be in from syntonic frequency before, the impedance of capacitance increases as frequency and decrescent; Be in after syntonic frequency, the impedance of capacitance increases as frequency and decrescent, present sensibility; Following plan institute show:

 

 

Lift as frequency, of capacitance not theoretical model will be more complex:

 

 

(C: ? Elaborate?nbsp; Rp: ? Ferociousing?Rs: of be an official of scull of apprentice of  archives Qian sheathing or bow case? Resistor of  ? electrode L: ? Inductance of  ? electrode)

 

If circuit of typical equivalent of capacitance parts of an apparatus pursues 1 is shown. In this equivalent circuit, the C that hold a cost is the mainest part, stringing resistor Rs and inductance L is the parasitism parameter that arises as a result of down-lead of pin of parts of an apparatus or electrode. Shunt-wound capacitance Rp is report capacitance is put between two pin.

 

 

After considering above parasitism parameter entirely, face of impedance formula as above is formulary.

 

As a result of the existence of these parasitism parameter, the total impedance of the capacitance parts of an apparatus in ideal of the and rather than in reality by below the real department in expression and empty ministry comprise twice partly:

 

If the leak between negligible electrode, namely the impedance infinity of Rp (or far big  Ls(ESL)  Rs (ESR)  The impedance that C is worth C at opposite Yu Rong) , so the equivalent circuit above can simplify further for 3 yuan of models below (what if pursue,show) . Among them ESL is Ls of inductance of equivalent series connection, ESR is Rs of resistor of equivalent series connection.

 

 

According to this simplifying circuit model, can get total impedance of capacitance parts of an apparatus follows the concern that frequency changes, if plan institute is shown. As a result of the existence of LS of inductance of equivalent series connection, as the addition of signal frequency F, the capacitive reactance XC of capacitance C is reduced, and the inductance XL that the equivalent with contrary polarity strings inductance Ls increases, f0 is nodded in certain frequency, XC=-XL. Right now the total impedance of capacitance parts of an apparatus | Z | =Rs, we say this frequency nods F0 to be from syntonic frequency (SRF) , when be less than SRF frequency, this parts of an apparatus becomes capacitance character, be more than SRF frequency conversely, polarity of happening of parts of an apparatus is changed, into inductance character (if pursue,place laying a plan is shown, gules and phasic curve from – 90° jumps change + 90° ) .

 

 

Q is worth the reciprocal that is equivalent to D value. Loss horn namely D value: Electroanalysis commonly capacitor because older friend D is worth internal resistance taller, its norms inspects capacitance to be worth decision of on any account, for 0.1-0.24 the following. Plastic film capacitor criterion D value is inferior, inspect its material to decide to be 0.001-0.01 character the following. Capacitor of pottery and porcelain inspects its material to decide character, hi-K Type and S/C Type are 0.025 the following. T/C Type its norms expresses to need prep above 400-1000 with Q value.

 

Note: XC=-j/(2πfC) ; XL=j(2πfL)

 

According to the definition of loss factor D: D=1/Q=R/ | X | > 0 take the place of the formula in front, get:

 

 

If the leak between negligible electrode, namely the impedance infinity of Rp (or the impedance that is more than opposite Yu Rong to be worth C far) , the computational formula of loss factor D simplifies greatly for:

 

 

If signal frequency is less than SRF syntonic frequency far, criterion X C >>X L, namely X L is negligible, formulary simplify further

 

 

Namely above mention:

 

 

See by the graph, the down-lead inductance of capacitor the lift and reduces capacitor character as frequency. If the capacitance of down-lead inductance and actual capacitor is syntonic, this will produce resonance of a series connection, make total reactance incline to is 0W. Because resonance of this series connection produces a very small series connection impedance, suit to be mixed in the coupling of radio frequency circuit very much so go applying in Ou circuit. However, when the frequency of resonance of series connection of working frequency prep above when circuit, this capacitor is expression inductance sex and not be capacitance sex.