MULTISIM DESIGN AND SIMULATION OF 2.2GHz LNA FOR WIRELESS COMMUNICATION

International Journal of VLSI design & Communication Systems (VLSICS) Vol.5, No.4, August 2014
DOI : 10.5121/vlsic.2014.5405 65
MULTISIM DESIGN AND SIMULATION OF
2.2GHz LNA FOR WIRELESS COMMUNICATION
Oluwajobi F. I, Lawalwasiu
Department of Electrical/Electronic Engineering,
RUFUS GIWA Polytechnic, OWO, P.M.B 1019, Nigeria
ABSRACT
This paper presents the work done on the design and simulation of a high frequency low noise amplifier for
wireless communication. The purpose of the amplifier is to amplify the received RF path of a wireless
network. With high gain, high sensitivity and low noise using Bipolar Junction transistor (BJT). The design
methodology requires analysis of the transistor for stability, proper matching, network selection and
fabrication. The BJT transistor was chosen for the design of the LNA due to its low noise and good gain at
high frequency. These properties were confirmed using some measurement techniques including Network
Analyzer, frequency analyzer Probe and Oscilloscope for the simulation and practical testing of the
amplifier to verify the performance of the designed High frequency Low noise amplifier. The design goals
of noise figure of 0.52dB-0.7dB and bias conditions are Vcc = 3.5 V and Icc= 55 mA to produce 16.8 dB
gain across the 0.4–2.2GHz band.
KEYWORDS
Amplifier, Bipolar Junction Transistor, Stability, LNA, Fabrication, Multism
1. INTRODUCTION
The function of low noise amplifier (LNA) is to amplify low-level signals so that very low noise
could be achieved. Additionally, for large signal levels, the low noise amplifier will amplify the
received signal without any noise or distortion hence eliminating channel interference. A low
noise amplifier plays an important role in the receiver and it is the major reason LNA is located
next to detection device, which made it to have major effect on the noise performance of the
general system. It amplifies extremely low signals without adding noise, therefore, protecting the
Signal-to-Noise Ratio (SNR) of the entire system. In LNA design, the major factor to put into
considerations are its simultaneous requirements for stability, low noise figure, high gain, good
input and output matching.[1]
The LNA should not add much noise to the analog signal thereby reducing the bit error rate when
the signal is decoded. After the LNA, the signal is typically filtered and down converted to an
intermediate frequency using a down converter mixer.

66
Fig.1 RF front-end architecture for generic infrastructure transceiver
Low Noise Amplifier (LNA) in any communication system provides the first level of
amplification of the signal received at the system’s antenna. The sensitivity of the receiver is
majorly determined by smallest possible signal that can be received by the receiver. The largest
signal that can be received by the receiver establishes an upper power level limit that can be
handled by the system while preserving voice or data quality [2]. The dynamic range of the
receiver, which defines the quality of the receiver’s chain is the difference between the highest
possible received signal level and the lowest possible received signal level. Additionally, for high
signal levels, the LNA amplifies the received signal without introducing any distortions, thus
eliminating channel interference [3,4]. It is equally important to consider additional design
parameters because of the complexity of the signals in today’s digital communications.[5]
Wireless communications signals are very noisy such that signals travelling from far away
normally suffer from a lot of degradation. Hence, the LNA is located next to the antenna.[9]. An
LNA is the combination of low noise, stability and high gain across the entire range of operating
frequency.
2. BIASING OF THE DEVICE
DC biasing network is essential to provide stable operating point for the device. Biasing circuit
must be protected from the high frequency effects.

67
Fig. 2: Typical LNA Biasing Circuit.
3. METHODOLOGY
For low noise system, the input (front-end) stages are very important. For small source
resistances, the BJTs are the preferred devices for these stages, and typically they have about 10
times lower level of equivalent input noise voltage than JFETs[7].For this design BJT(transistor)
was used because of the above stated reason. The circuit was actualized in Multism 11.0 and
simulated to confirm the performance of the circuit by measuring the stability factor, S-
parameter, gain and operating frequency using network analyzer ,frequency analyzer and
oscilloscope .After the simulations and mathematical calculations has been compared and
analyzed, the design was proceed for fabrication using the ultiboard simulator to place all the
designs component on a board and a schematic diagram was derived on how the board size will
be.
Thereafter, the layout of the design circuit schematic was developed using ultiboard layout
software where the size of the design was adjusted and the placement of the components were
arranged.
4. STABILITY
The stability of a circuit is characterized by Rowlett’s stability factor (K), Circuit is stable when
K>1
in addition ∆ <1.
(1)
(2)

68
Absolute stability is then determined when the input reflection coefficient is <1 and output
reflection coefficient out <1. This must be considered important in the design of LNA and can be
determined from the S-parameters, matching networks and terminations [8] .Unconditional
stability means that with an arbitrary, passive load connected to the output of the device, the
circuit will not become unstable, that is will not oscillate. Two stability parameters K and |∆| can
be calculated to determine as to whether a device is likely to oscillate or whether it is
unconditionally or conditionally stable. Where
|∆| = |S11S22 - S12S21|< 1 (3)
and
K = 1 - |S11|2
-|S22|2
+ |∆|2
< 1 (4)
2|S12 --- S21|
The parameters K must satisfy K>1, | ∆ |<1 and the parameter b must be greater >0for a
transistor to be unconditionally stable.
Where:
(5)
The S-parameter matrix of common 2-port network is shown in figure 3
below;
Fig 3: Sketch of a 2-Port Network
Here is the matrix algebraic representation of 2-port S-parameters:
(6)
Where:
S11 is the input port voltage reflection coefficient, and S11= b1/a1.
S12 is the reverse voltage gain, and S12= b1/a2.
S21 is the forward voltage gain, and S21= b2/a1.
S22 is the output port voltage reflection coefficient, and S22= b2/a2 [2]

69
5. NOISE FIGURE CONSIDERATIONS
In wireless communications, lower noise figure shows the efficiency of the LNA which means
less noise is added by the LNA. In telecommunications, noise factor is determined by measuring
the degradation of signal to noise ratio. [9]
Besides stability and gain, another major factor to consider in the design of LNA is bringing to
minimal its noise figure.
5.1 The BJT Noise Model
From equation (7) below noise specifications for BJT's are commonly measured as Vn,
ܸ௡ଵ = ඨ4݇ܶ‫ݎ‬௫∆݂ + 2݇ܶ
்ܸ
‫ܫ‬஼
∆݂
= ඨ4 × 1.38 × 10ିଶଷ × 300 × 620.29 × 2.2 × 10ଽ + 2 × 1.38 × 10ିଶଷ × 300 ×
0.0259
4.998 × 10ିଷ
× 2.2 × 10ଽ
= ඥ2.27 × 10ି଼ = 1.5 × 10ିସ
ܸ
ܸ௡ଶ = ඨ4݇ܶ‫ݎ‬௫∆݂ + 2݇ܶ
்ܸ
‫ܫ‬஼
∆݂
= ඨ4 × 1.38 × 10ିଶଷ × 300 × 31.45 × 2.2 × 10ଽ + 2 × 1.38 × 10ିଶଷ × 300 ×
0.0259
8.13 × 10ିଷ
× 2.2 × 10ଽ
= ඥ1.2 × 10ିଽ = 3.464 × 10ିହ
ܸ
6. CIRCUIT DESIGN OF A HIGH FREQUENCY LOW NOISE AMPLIFIER
Fig 4. Designed LNA Circuit

70
7. SIMULATIONS RESULTS
In this section, simulation results from MULTISIM 11.0 are presented. Shown in figure 5 to 9
The simulation result of stability, which determines the effectiveness of the circuit. As stated
earlier, for an LNA circuit to be stable and effective, Delta must be lesser than one while
Rowlett’s stability factor (K) must be greater than one. Other simulations are presented alongside.
Fig5. Stability at 2.0GHz
Fig.6: Stability Simulation at 2.2GH

71
Fig.7: Simulation of S-parameters
Fig.8: Simulation at 2.2GHz on network analyzer for Gains (Re/Im)

72
Fig.9: Simulation with an Oscilloscope
8. DISCUSSIONS
The design of an LNA for a wireless mode of operation at a high frequency range of 1.9 GHz -
2.2 GHz with a good gain is determined majorly by the quality of RF transistor used in the
design. The results derived after simulation using multism 11.0 were shown in fig5-9.
Fig 5 and 6 are the simulated results on Network analyzer for Rowlett’s stability (K), the results
obtained for Rowlett’s stability (K) over range of frequencies 1.9GHz- 2.2GHz are >1 and
delta(∆) are <1 this shows that the transistors used for this design is said to be unconditionally
stable which is good for the design.
Figures7 and 8 are the simulation results for the s-parameters of the design when the mode was
on the measurement while the graph parameter was smith and the trace are s11 and s22. Fig 8 of
the simulation result shows the mode was RF character and the graph parameter is in
real/imaginary and the trace is for voltage gain (V.G) of the design, which was done between
frequency ranges of 425MHz to 2.034GHz. The gains on simulation results vary within the
ranges of 10.15dB and 16.8dB, which is actually good for this design.
Table 1: Simulated results for Delta and Stability factor at 1.9GHz-2.2GHz
FREQUENCY DELTA(∆∆∆∆) STABILITY FACTOR(K)
1.9GHz 0.423 3.476
2.0GHz 0.237 1.205
2.2GHz 0.14 17.465

73
Table 2: SIMULATION PARAMETERS ACCROSS 0.4-2.2GHz
AT FREQUENCY 2.2GHz SIMULATION
Gain(S21) 16.8dB
ICC 55mA
VCC 3.5V
This design was based on 50 Ω input and output impedance considering the fact that most RF
designs are designed to be 50Ω. The gain and the noise generated which are very essential in
LNA designs are analyzed carefully so that adequate signal propagated can be received with
minimal signal to noise ratio.
9. CONCLUSION
The designed LNA with matching network at 2.2GHz GHz is obtained. In LNA design, the
research goal is to achieve the unconditional stability over the complete range of frequencies
along with substantial gain and low noise figure, which was achieved for both stages in the
simulation results. Transistor is added for unconditional stability. Therefore, NF and gain are
sacrificed. For two stages, mismatch at the output of the first-stage can then be optimized to
improve input return loss without adversely effecting noise figure.
This device yields excellent bandwidth, linearity and super low noise figure with high efficiency.
The system was simulated using ADS (MULTISIM 11.0), an RF circuit simulator. The design
went through a series of tests and measurements for verification. The data from these
measurements was recorded, documented, and compared to the simulated predictions.
REFERENCES
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26,2006
[2] A.O. Fadamiro1 and E.O. Ogunti Design of a High Frequency and High Sensitive Low Noise
Amplifier Asian Journal of Engineering and Technology (ISSN: 2321 – 2462) Volume 01– Issue 02,
June 2013
[3] Yu Lin Wei and Jun De Jin, “A low power low noise amplifier for K-band applications,” IEEE
Microwave and Wireless Components Letters, vol. 19, no. 2, pp. 116-118, Feb. 2009
[4] Bonghyuk Park, Sangsungs Choi, and Songcheol Hong, “A low noise amplifier with tunable
interference rejection for 3.1 to 10.6 GHz UWB systems,” IEEE Microwave and Wireless
Components Letters, vol. 20, no. 1, pp. 40-42, Jan 2010.
[5] Mercer, S.: An Introduction to Low-Noise Amplifier Design, RF Design, Pp.4 2008

74
[6] Viranjay M. Srivastava, K. S. Yadav, and G. Singh, “Design and performance analysis of cylindrical
surrounding double-gate MOSFET for RF switch,” Microelectronics Journal, vol. 42, no. 10, pp.
1124-1135, Oct. 2011
[7] Shouxian, M.: Dival Band Low Noise Amplifier Design For Bluetooth And Hiper Law Application.
PhD Dissertation In Electrical and Electronics Engineering, Nanyang Technological University.2006
[8] H. W. Chiu, “A 2.17 dB NF 5 GHz band monolithic CMOS LNA with 10 mW DC power
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[9] Aniket, P.J., Mahaya, S.P., Joshi, B.C.s, Design and Development of Low Noise Amplifier for
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MULTISIM DESIGN AND SIMULATION OF 2.2GHz LNA FOR WIRELESS COMMUNICATION

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MULTISIM DESIGN AND SIMULATION OF 2.2GHz LNA FOR WIRELESS COMMUNICATION