U2741B Datasheet, PDF (5/9 Pages) ATMEL Corporation – UHF ASK/FSK TRANSMITTER

Output Power
Measurement
U2741B
The output network [as shown in Figure 4] can be used for output power evaluation, the
exact values of L₁₀ and C₁₀ depend on the layout.
L₁₀ and C₁₀ form the transformation network to adopt the output impedance of the IC to
50 W. Table 1 shows the values for an output power of 2 mW and an R_PWRSET = 1.2 kW.
Table 1. Transformation Network
f/MHz
315
433.92
C10/pF
2.7
1.8
L10/nH
56
33
Z_{Load_opt}/W
260 + j330
185 + j268
Figure 4. Measurement Output Network
V_S
PWRVCC
L₁₀
ANT
C₁₀
50 W
Z_Load-opt
Figure 5. Application Circuit
+V_S = 2.0 ... 5.5 V
ASK
FSK
C₇
CLK
3.39 MHz
C₆
R₄
ASK
1
FSK
2
VCC
3
CLK
4
GND
5
LFVCC
6
LFGND
7
C_{1 LF}
8
OR
Power
up
VCO
f
64
f
n
U2741B
PA
XTO
C₂
DIVC
16
PWRSET
15
PWRVCC
14
ANT
13
R_PWRSET
C₅
PWRGND1
12
C_Loop2
L_Feed
C_Loop1
PWRGND2
11
XTO1
13.56 MHz
10
XTO2
C₄
9
C₃
Antenna
5
4733A–RKE–11/03