Mk2420552059

M.A. Othman, M.M. Ismail, H.A. Sulaiman, M.H. Misran, M.A. Meor Said / International
Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622
www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2055-2059
LC Matching Circuit Technique For 2.4 Ghz LNA Using AVAGO
ATF-54143

M.A. Othman, M.M. Ismail, H.A. Sulaiman, M.H. Misran, M.A. Meor Said
Centre for Telecommunication Research and Innovation (CeTRi)
Fakulti Kej. Elektronik dan Kej. Komputer
Universiti Teknikal Malaysia Melaka
76100 Durian Tunggal, Melaka, Malaysia

ABSTRACT
This paper presents the design, design and transistor. It can amplify small signal at operating
simulates a single stage LNA circuit with high frequency around 2 GHz. Thus, it meets our
gain and low noise using NPN Epitaxial for requirement to design a LNA at 2.4 GHz. Besides
frequency range of 2.4GHz. The design simulation that, ATF 54143 can perform with low voltage
process is using Advance Design Simulation supplied.
(ADS) and performance of each microwave Before start designing, the design
receiver there is Low Noise Amplifier (LNA) requirement is set in order to ensure our LNA
circuit. This amplifier exhibits a quality factor of designed can achieve the target.
the receiver. When this amplifier is biased for low i. Operating range = 2.0 to 3.0 Ghz
noise figure, requires the trade-off many ii. Gain > 12 dB
importance characteristics such as gain, Noise iii. Noise Figure < 2.5 dB
Figure (NF), stability, power consumption and iv. Return loss for source > 10 dB
complexity. Besides its excellent noise v. Return loss for load > 10 dB
performance, this is the highest frequency vi. Power supply = 5V
amplifier ever reported using three terminal
devices.

Keywords - Low Noise Amplifier, Lumped
Elements Matching, Power gain, Noise Figure,
Unilateral

I. INTRODUCTION
The function of low noise amplifier (LNA)
is to amplify low-level signals with maintain a very
low noise. Additionally, for large signal levels, the
low noise amplifier will amplified the received Figure 1: Equivalent circuit of ATF 54143 from
signal without introducing any noise, hence AVAGO
eliminating channel interference. A low noise
amplifier function plays an undisputed importance in II. LNA DESIGN
the receiver. Transistor must be biased at appropriate
Low Noise Amplifier (LNA) plays a crucial operating point before used. So that, transistor can
role in the receiver designs. LNA is located at the work under values required and achieve less power
first stage of microwave receiver and it has dominant consumption. In this project, passive biasing method
effect on the noise performance of the overall is adopted. The component readings are determined
system. It amplifies extremely low signals without with reference from datasheet.
adding noise, thus the Signal-to-Noise Ratio (SNR) By referring datasheet, data of Vds = 3V and Ids
of the system is preserved. In LNA design, it is = 60mA had be chosen because it is believed can
necessary to compromise its simultaneous give optimum values in gain and noise figure
requirements for high gain, low noise figure, With Vgs = 0.52, IBB=2m, Vds = 3V and Ids =
stability, good input and output matching . The LNA 60mA,
design in this report is carried out with a systematic
procedure and simulated by Advanced Design
System (ADS2008).Microwave Amplifier Design.
In this project, ATF 54143 transistor is
chosen in designing low pass amplifier. It is because
AT-54143 is a high dynamic range, low noise
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= 56.43 = 17.52 dB

Transducer gain, GT

Stability Consideration
The stability of an amplifier or its
resistance to oscillate is an important consideration
in a design. It can be determined from the S
parameters. Oscillation occurs when > 1 or
> 1.This is due to the dependence of and on
the source and load matching networks. An amplifier
Figure 2: DC biasing Circuit is said to be unconditionally stable if the auxiliary
condition along with Rollet’s condition, defined as in
The R1, R4 and R3 in circuit are slightly adjusted equations below, are simultaneously satisfied.
from calculation readings in order to obtain better
Vds and Ids reading in the simulation.
Given
From the data sheet, S parameter at 2.5 GHz is: (8)
K = 1.11478 > 1 = 0.3427 < 1
Noise Figure
Besides the stability and gain requirement,
noise figure is another important consideration for a
microwave amplifier. In receiver applications, it
often required preamplifier with as low noise figure
The reflection coefficient to source, ГS and as possible as it has dominant effect on the noise
reflection coefficient to load, ГL. The equation is performance of the system. From the ATF-54143
shown in (1) and (2). datasheet, Fmin = 0.52, = 0.26 and RN/Zo = 0.04
at 2.4 GHz at 2.4 GHz (There are not reference for
2.5 GHz)
Figure. 3: The General Transistor Amplifier
.
Circuit.
= 0.52
Reflection coefficient at the load:
NF = 2.769 dB
Matching Network
The impedance matching basic idea is
presented in Fig. 2, which ensembles that an
impedance matching network placed between the
Since given ZL = ZS = Zo = 50Ω, the ГL and ГS load impedance and transmission line.Matching
calculated as zero. Reflection coefficient at the input network is made to ideally avoid the unnecessary
and output: loss power. There are variety of factors that needed
to be considered in the matching network selection
e.g. complexity, implementation and adjustability. In
this paper, the LNA is designed by using lumped
elements matching and quarter-wave transformer
matching techniques.

Power gain, G

Figure 4: Impedance Matching Network
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III. RESULTS AND DISCUSSIONS
A. Before Matching

Figure 5: Circuit before matching
Figure 6: Output load matching
The parameters of noise figure, stability
factor, return loss and gain values are calculated by The components reading designed by ADS
using equations (1 to 9). While simulation results software are not exist in market. Thus, to fabricate, it
before the matching are listed as in Table 1. must change to actual values.
Parameters Calculated Simulation
0
0

1.1478 0.97
17.52 dB 17.25 dB
15.65 dB 15.31 dB
15.58 dB 15.76 dB
15.58 dB 15.63 dB
NF 2.769 dB 0.375 dB LC
Table 1: Results differences in calculated and matching
simulation before applying matching network. circuit

B. After Matching
To match both impedance of input and
output. Lumped elements matching is added into
LNA circuit with assistance of smith chart utility in Figure 5: Circuit after matching
AdS software. After matching from smitch chart, the
Lumped elements circuit will automatical generated.
m2 m3
freq=2.400GHz freq=2.400GHz
dB(S12)=-23.066 dB(S21)=17.333
Forward and Reverse Trans., dB
19 -22.5

18 m2
m3 -23.0
dB(S12)
dB(S21)

17
-23.5
16
-24.0
15

14 -24.5
2.0 2.2 2.4 2.6 2.8 3.0

freq, GHz

Figure 6: S12 (isolation) and S21 (gain)
Figure 5: Input source matching

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0 m4 The gain is also an important factor in
freq=2.400GHz designing LNA for use in amplifier design.
-5 dB(S(1,1))=-10.077
m4 Maximum available gain is a figure of merit for the
dB(S(1,1))

-10 LNA, which indicates the maximum theoretical
-15 power gain when it is conjugate matched to its
-20
source and load impedances. The calculated gain is
17.52 dB compared to the simulated gain which is
-25
2.0 2.2 2.4 2.6 2.8 3.0
17.25, the calculated and simulated power gain show
freq, GHz almost the same result. The matching network of
Figure 7: S11freq
(dB) dB(S(1,1))
amplifier design is measured by the tranducer power
2.000 GHz -14.042 gain where it can be defined as separate effective
2.100 GHz -20.441
2.200 GHz
m5 -17.531 gain for input (source) matching network, transistor
2.300 GHz -12.876 and the output matching network.
-5 2.400 freq= 2.400GHz
GHz -10.077
2.500 dB(S(2,2))=-10.442
GHz -8.269 An LNA is a design that minimizes the
2.600 GHz
m5 -7.017
-10 2.700
2.800
GHz
GHz
-6.106
-5.420
noise figure of the system by matching the device to
dB(S(2,2))

2.900
3.000
GHz
GHz
-4.887
-4.465
its noise matching impedance, or Gamma optimum.
-15
Gamma optimum occurs at impedance where the
-20
noise of the device is terminated. All devices exhibit
noise energy. To minimize the noise as seen from
-25 the output port, we need to match the input load to
2.0 2.2 2.4 2.6 2.8 3.0
the conjugate noise impedance of the device.
freq, GHz Otherwise, the noise will be reflected back from the
Figure 8: S22 (dB)
freq dB(S(2,2)) load to the device and amplified. The noise figure
2.000 GHz -5.472 passes the requirements. It can be observed that the
2.100 GHz -6.497
0.70 2.200 GHz -7.699 calculated noise figure and the simulated noise
2.300 GHz -9.027
0.65 2.400 GHz -10.442 figure is not the same. This is because the input and
2.500 GHz -11.918 output port of the network is not matched.
0.60 2.600 m8
GHz -13.445
0.55
2.700
2.800
GHz 2.400GHz
freq=
GHz
-15.022
-16.658
For the result obtained from the simulation, the
nf(2)=0.478
NFmin

power gain is 17.25dB and the noise figure is
nf(2)

2.900 GHz m8 -18.367
0.50 3.000 GHz -20.166
0.382dB, while the return loss for source and return
0.45
m7 loss for load is -10.077dB and -10.442dB
0.40 m7 respectively. The results obtained from the LNA
0.35 freq= 2.400GHz
NFmin=0.382 simulation have achieved the requirements that have
0.30
been set.
2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0
Filter matching can be included into the
freq, GHz designed circuit which is used at the output of
Figure: Minimum Noise Figure (NFmin), Noise transistor method. This is used to eliminate gain at
Figure (nf2) high frequencies and increase the band of operation.
On the other hand, resistive loading is recommended
Parameters Before Matching After Matching to have at the input as the stability of circuit can be
-3.078 -10.077 dB improved. The matching procedures for input and
-28.530 -10.442 dB output have to be carried out simultaneously to
-25.438 -23.066dB ensure prefect matching is achieved.
14.960 17.333 dB
NFmin 0.382 0.382 IV. CONCLUSION
NF 0.375 0.478 A Low Noise Amplifier with given desired
K 1.004 1.004 characteristics was able to design. From the
Table 1: Results differences in calculated and comparison of the calculated and simulated result it
simulation after applying matching network. can be seen that there is a slight difference in values.
From the simulation result above, it is difficult to
The stability of this transistor is design a low noise amplifier that has both low noise
unconditionally stable at 2.5 GHz since its K figure and high gain together. So, it is very
constant is more than 1, which is 1.004 from the important to tolerate between the input and output
simulation. Therefore, no stability circle has to be matching in order to get the perfect match.
drawn. Stability and maximum available gain are
two of the more important considerations in ACKNOWLEDGEMENTS
choosing a two-port network LNA for use in Authors would like to thank Universiti
amplifier design. As used here, stability measures Teknikal Malaysia Melaka for their support in term
the tendency of an LNA to oscillate. of financing to this project and also to this journal.

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REFERENCES
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[10] Agilent Technologies (2000).”Agilent
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