MICRF102BM TR Micrel Inc, MICRF102BM TR Datasheet - Page 9

• Manufacturer Part Number: MICRF102BM TR
• Manufacturer: Micrel Inc

Specifications of MICRF102BM TR

• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.94mm
• Product Height (mm): 1.48mm
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / Rohs Status: Not Compliant

Design Examples
Complete reference designs including gerber fi les can be
downloaded from Micrel’s website at: www.micrel.com/prod-
uct-info/qwikradio.shtml.
Antenna Characteristics
In this design, the desired loop inductance value is determined
according to the table below.
The reference design, shown in Figure 7, has an antenna
meeting this requirement.
Loop antennas are often considered highly directional. In
fact small loop antennas can achieve transmit patterns close
in performance to a Dipole antenna. The radiation pattern
below is the theoretical radiation pattern for the antenna, as
shown in Figure 8.
The 0 degree plot is the radiation pattern in the plane of the
transmitter PCB, the 90 degree plot represents the plane
perpendicular to the PCB. Micrel’s evaluation of the perfor-
mance of the board in Figure 8 indicates an even more uniform
radiation pattern that the theoretical plot shown here.
December 2006
(MHz)
Freq.
300
315
390
434
(180-phi) direction
Figure 8. Polar Elevation Pattern at 315MHz.
2.34
(Ω)
1.7
3.2
2.1
R
120.0
Figure 7. Demo Board PCB.
60.0
E-total, phi = 90¡
E-total, phi = 0¡
150.0
84.5
89.3
161
136
30.0
(Ω)
XL
180.0
0.0
(nH)
44.8
45.1
47.4
50.0
Ind
30.0
150.0
(XL/R)
39.72
39.65
52.00
78.33
Q
120.0
60.0
phi direction
0.83
0.85
0.90
0.96
K
9
Supply Bypassing
Supply bypassing consists of three capacitors; C3 = 4.7µF,
C4 = 0.1µFand C5 = 100pF
Example to Calculate C
Calculation
Where Length and d are in mm and L is in H;
Where k is a constant dependent on PCB material, copper
thickness, etc.
MICRF102 Series Capacitor Calculation:
MICRF102 Series Capacitor Calculation:
C4
0.1µF
16V
+5VTX
Length_mils = 2815
dmils = 70
k = 0.85
f = 315 × 10
L = 46 × 10
C
C
f = 433.92 × 10
L = 52 × 10
C
C
Length
L
L
VAR
P
C
C
C
C
VAR
P
C
C
Length 71.501
T
T
SERIES
SERIES
T
T
=
=
= 12 × 10
= 2.7 × 10
=
=
=
=
0.2 Length ln
44 10
= 5 × 10
= 5 × 10
2 587 10
2 587 10
4
4
×
.
.
C5
100pF
50V
×
×
×
Figure 9. Supply Bypassing
=
=
=
=
π π
π π
(
-9
-9
8 2 10
Length_mils 25.4
6
2
C
2
−
-12
×
.
×
1
1
1
9
×
-12
×
T
-12
-12
×
6
f
f
−
2
2
1
−
−
×
×
×
C
12
12
C3
4.7µF
16V
1000
L
L
S
−
V AR
1
12
and C
⎛
⎜
⎝
Length
×
d
P
Antenna Inductance
−
)
1.6
1
2
3
4
d
d
⎞
⎟ ×
⎠
PC
VDD
V
REFOSC
=
=
SS
1 778
(
dmils
.
10
MICRF102
−
1000
9
MICRF102
×
×
ANTM
ANTP
k
25 4
ASK
SB
.
)
8
7
6
5