MICRF219 datasheet(13/24 Pages) MICREL

13 / 24 page

Micrel

MICRF219

M9999-011509

(408) 944-0800

January 2009

n for best

hing point,

s to know

shows the

ggested

or t

encies.

These sugge

d value

ay be

nt if the layout

exactly

same

he on

here.

(MHz)

C3 (pF)

Z device (Ω)

can see the impedance moving directio

values of C8 and L1 toward to central matc

like WinSmith by Noble Publishing.

To calculate the matching values, one need

the input impedance of the device. Table 3

input impedance of the MICRF219 and su

matching alues f

he mos often used frequ

ste

s m

differe

not

the

as t

e made

Freq

(nH)

315

1.8

33 - j235

390

1.5

23 – j199

418

1.5

21 – j186

433.92

1.5

19 – j174

Table 3. Matching values for the most used frequ

ency of 43

input impe

the matching compo

nt parallel = B = 1/Z = 0.606 +

Im (B)

Xp = 17

+ 1)

etwork

Lc = Xp / (2×Pi×f);

Lp = Xm / (2×Pi×f)

L2 = (Lc×Lp) / (Lc + Lp);

C3 = 1 / (2×Pi×f×Xm)

L2 = 39.8nH

C3 = 1.3pF

Doing the same calculation example with the Smith

Chart, would appear as follows,

First, one plots the input impedance of the device,

(Z = 18.6 – j174.2)Ω @ 433.92MHz.(Figure 5).

encies

dance

nents

j5.6

For the frequ

3.92MHz, the

is Z = 18.6 – j174.2Ω, then

are calculated by,

Equivale

msiemens

Rp = 1 / Re (B);

Xp = 1 /

Rp = 1.65kΩ;

6.2Ω

Q = SQRT (Rp/50

Q = 5.831

Xm = Rp / Q

Xm = 282.98Ω

Resonance Method For L-shape Matching N

Figure 5. Device’s input impedance, Z = 19 – j174Ω

Second, one plots the shunt inductor (39nH) and the

series capacitor (1.5pF) for the desired input

impedance (Figure 6). One can then see the matching

leading to the center of the Smith Chart or close to

50Ω.

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