MC138512400QSG
1
RF Engineering Bulletin
Freescale Semiconductor
MC13851 Evaluation Board Quick Start —
2400 MHz
INTRODUCTION
This evaluation board design demonstrates one possible
design at 2.75 V that satisfies competing requirements for NF,
IP3, gain, return losses and current consumption. By
changing any of the requirements, the performance for a
particular parameter can be improved to meet a particular
spec requirement.
This circuit was designed to provide NF of 1.5 dB, S21 gain
> 15 dB using R1 = 1.2 k
Ω
and 1.5 k
Ω
.
Bias resistor R1 is used to adjust for the desired current
drain and IP3 performance.
Gain or NF can be improved with matching changes to meet
specific requirements.
Resistor R3 is used to de--Q output inductor L2 and adjust
gain and return losses. Lowering R3 lowers gain and improves
return losses.
The LNA is bias stabilized for variations in device and
temperature.
NOTE: Tables 1 and 2 list measured parameters on three
typical evaluation boards and are meant as a guide to the RF
performance possible for this application circuit. Variations in
matching component performance may result in variation in
evaluation board performance results.
Table 1. Evaluation Board Measurements
(2400 MHz, V
CC
= 2.75 V, Frequency Spacing = 200 kHz, Non--Linear Measurements
at P
in
= --30 dBm)
Serial #
R1
Mode
Input
Power
(dBm)
Output
Power
(dBm)
Power
Gain
(dB)
Output
IP3
(dBm)
Input
IP3
(dBm)
Output Ref
P
1dB
(dBm)
Input Ref
P
1dB
(dBm)
NF
(dB)
I
CC
(mA)
1
1.2k
Active
--30.00
--13.91
16.09
17.59
1.5
8.29
--7.8
1.51
5.1
1
1.2k
Bypass
--30.00
--34.91
--4.91
20.29
25.2
—
—
5.21
1.56n A
2
1.2k
Active
--30.00
--13.76
16.24
16.99
0.75
8.04
--8.2
1.5
4.47
2
1.2k
Bypass
--30.00
--35.09
--5.09
20.31
25.4
—
—
5.47
3.6 nA
3
1.2k
Active
--30.00
--13.90
16.10
17.80
1.7
8.20
--7.9
1.51
4.54
3
1.2k
Bypass
--30.00
--34.82
--4.82
20.48
25.3
—
—
5.08
7.6 nA
1
1.5k
Active
--30.00
--14.09
15.91
19.01
3.1
8.01
--7.9
1.5
4.02
1
1.5k
Bypass
--30.00
--34.88
--4.88
20.82
25.7
—
—
5
1.56 nA
2
1.5k
Active
--30.00
--14.17
15.83
17.33
1.5
7.83
--8.0
1.52
3.55
2
1.5k
Bypass
--30.00
--35.08
--5.08
20.22
25.3
—
—
5.29
3.6 nA
3
1.5k
Active
--30.00
--14.18
15.82
17.92
2.1
8.12
--7.7
1.52
3.63
3
1.5k
Bypass
--30.00
--34.85
--4.85
20.15
25
—
—
5.09
7.6 nA
Table 2. S--Parameters
(2400 MHz, V
CC
= 2.75 V)
Serial #
R1
Mode
S11 (dB)
S21 (dB)
S12 (dB)
S22 (dB)
1
1.2k
Active
--11.96
15.76
--23.6
--13.4
1
1.2k
Bypass
--15.05
--5.03
--5.3
--22.8
2
1.2k
Active
--12.27
15.75
--23.8
--11.63
2
1.2k
Bypass
--14.27
--5.09
--5.4
--23.5
3
1.2k
Active
--13.12
15.68
--23.5
--11.47
3
1.2k
Bypass
--14.83
--4.96
--5.19
--21.7
1
1.5k
Active
--10.7
15.57
--23.7
--12.38
1
1.5k
Bypass
--14.7
--5.06
--5.4
--21.40
2
1.5k
Active
--10.4
15.43
--23.2
--10.91
2
1.5k
Bypass
--14.3
--5.14
--5.44
--23.20
3
1.5k
Active
--11.14
15.32
--23.1
--10.8
3
1.5k
Bypass
--14.77
--5.02
--5.26
--21.17
MC138512400QSG
Rev. 0, 11/2010
Freescale Semiconductor
Quick Start Guide
Document Number:
©
Freescale Semiconductor, Inc., 2010. All rights reserved.
