
Micrel
MICRF009
Additional Applications Information
In addition to the basic operation of the MICRF009, the
following enhancements can be made. In particular, it is
strongly recommended that the antenna impedance is
matched to the input of the IC.
Antenna Impedance Matching
As shown in Figure 7, and Table 4, the antenna pin input
impedance is frequency dependent.
The ANT pin can be matched to 50 ? with an L-type circuit
as shown in Figure 3. That is, a shunt inductor from the
antenna input to ground and another in series from the
antenna input to the ANT pin.
Inductor values may be different from Table 4, depending
on PCB material, PCB thickness, ground configuration, and
how long the traces are in the layout. Values shown were
characterized for a 0.031” thickness, FR4 board, solid
ground plane on bottom layer, and very short traces.
MuRata and Coilcraft wire-wound 0603 or 0805 surface
mount inductors were tested, however, any wire-wound
inductor with high SRF (self-resonance frequency) should
do the job.
Shutdown Function
Duty-cycled operation of the MICRF009 (often referred to
as polling) is achieved by turning the MICRF009 on and off
via the SHUT pin. The shutdown function is controlled by a
logic state applied to the SHUT pin. When VSHUT is high,
the device goes into low-power standby mode. This pin is
pulled high internally, and it must be externally pulled low
to enable the receiver.
Frequency
(Mhz)
300
305
310
315
320
325
330
335
340
345
350
355
360
365
370
375
380
385
390
395
400
405
410
415
420
425
430
435
S11
Mag, angle
0.944,-36.65
0.940,-37.499
0.942,-37.579
0.945, -37.66
0.943,-38.237
0.942, -38.814
0.94, -39.39
0.938, -39.967
0.937, -40.544
0.935, -41.12
0.933, -41.697
0.931, -42.274
0.93, 42.85
0.928, -43.427
0.926, -44.004
0.925, -44.581
0.923, -45.157
0.921, -45.734
0.92, -46.311
0.917, -46.729
0.914, -47.148
0.912, -47.566
0.909, -47.985
0.907, -48.403
0.906, -48.797
0.909, -49.152
0.911, -49.507
0.911, -49.925
Z11, ohms
14.45-j150
14.84-j145
14.28-j145
13.48-j145
13.58-j143
13.43-j140
13.5-j138
13.59-j136
13.44-j134
13.51-j132
13.57-j130
13.62-j123
13.48-j126
13.52-j124
13.57-j122
13.42-j120
13.46-j118
13.49-j117
13.35-j115
13.6-j114
13.89-j113
14.00-j112
14.25-j110
14.34-j109
14.28-j108
13.63-j107
13.15-j107
12.94-j106
C3, pF
2.2
2.2
2.2
2.2
2
1.8
1.8
1.8
1.8
1.8
2
2.2
2.2
2
1.8
2.2
2
1.8
1.8
1.8
2
1.8
1.8
2.2
2
2
1.8
1.8
L2, nH
47
47
47
47
47
47
47
43
43
43
39
36
36
36
36
33
33
33
33
33
30
30
30
27
27
27
27
27
j25
j100
440
0.904, -50.571
13.66-j104
1.8
27
Table 4
0
–j25
50
Figure 7
–j100
∞
January 18, 2005
12
M9999-011805
(408) 955-1690