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International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
Design and Simulation of
3.5 GHz MMIC Power Amplifier Using GaAs Technology
Sharath Babu Kamsali, Student, R V College Of Engineering, Bangalore, and
P. Shanthi, Asst. Professor, R V College Of Engineering, Bangalore
Abstract— Design of MMIC power amplifier for wireless application by using 0.3 μm GaAs technology with a gate width
of 250 μm and ten fingers at 3.5 GHz. For 3.5GHz power amplifier has achieved 17.69 dB small-signal gain, input and
output return loss of -13.41 dB and -9.41 dB, with the concerns power-added efficiency (PAE). The 3.5 GHz power
amplifiers used for WiMax base station.
Index terms — FET, stability factor, matching network and power amplifier.
I. INTRODUCTION
the objective of an amplifier is to increment the input power. Amplifiers detect application in all
G enerally
kinds of electronic contrivances designed to perform number of functions. Types of amplifiers have each
with a categorical reason. For example, a radio transmitter makes utilization of an RF Amplifier such an
amplifier is designed to amplify the given signal in radio frequency range.
Modern microwave and RF engineering is an exciting and dynamic field, as a result of recent advances
in fashionable device technology and also the current explosion in demand for voice, data, and video
communication capability. Prior to this revolution in communications, microwave technology was the nearly
exclusive domain of the defense trade and dramatic increase in demand for communication systems for such
applications as wireless paging, mobile telecom, broadcast video, and confined in addition as personal
communication networks is revolutionizing the trade. Microwave technology is of course suited to these
emerging applications in communications and sensing, since the high operational frequencies allow each
massive numbers of freelance channels for the big variety of uses unreal in addition as vital accessible
information measure per channel for prime speed communication.
Power Amplifiers are present in the transmitting chain of a wireless system. They are the final
amplification stage before the signal is transmitted, and therefore must produce enough output power to
overcome channel losses between the transmitter and the receiver. The design of RF and microwave amplifiers
has various facets affecting their performance. The most important factors include the selection of
semiconductor technology, device models, circuit architecture and design methodology, matching networks,
packaging, and thermal management.
Fig.1. Block diagram of an amplifier circuit
An amplifier circuit consists primarily of a gain device or devices, and input and output matching or coupling
networks as shown in Fig.1. The amplifier ought to create weak signals larger while not adding an excessive
amount of noise or distortion. Ideally, the amplifier would add no noise and wouldn't distort the signal in any
manner.
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International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
The amplifier objective is to attenuate the extra noise and therefore the distortion created whereas
increasing the amplitude of the signal.
II. DESIGN AND IMPLEMENTATION
The design methodology for power amplifier design can be broken down into three main sections: biasing
network, stability considerations, and matching network for optimization.
A .Biasing Network:
The GaAs FET is what's typically brought up as a “normally ON” sort device. Its basic distinction from the
MOSFET is that the use of a Schottky barrier at the gate rather than associate oxide layer. This is often a
particularly necessary purpose. In other words, virtually no GaAs FET gates isolated from the channels in terms
of DC. Thus, even if GaAs FETs referred to as “normally ON” sort devices, the utmost gate voltage should be
zero. It doesn't use dielectric just like the MOSFET, therefore if a positive voltage is applied at the gate,
electricity flows through it. Since the gate may be a very little piece of metal (0.5, µ-1.0µ-2.0µ), the gate
electrodes can fuse fully in most cases.
B. Stability Considerations:
Two port networks may be stable or potentially unstable. It is imperative that the amplifier does not oscillate in
the product environment, since such behavior leads to product malfunction. If the two-port is potentially
unstable, there are conditions where oscillations can occur. Certain source or load terminations that produce the
oscillations provide the conditions necessary for the unstable behavior. This type of design is called a
conditionally stable design. If the conditionally stable design method is utilized, extreme care must be observed
to guarantee that a source or load termination that produces an oscillation is never presented to the amplifier.
This applies to all frequencies in-band and out of band. This can be a difficult task at best in most applications.
The unconditionally stable design approach allows any source or load terminations, which have reflection
coefficient magnitudes between „0‟ and „1‟, inclusive, presented to the amplifier without the possibility of an
oscillation. It is highly recommended that the two ports are made unconditionally stable at all frequencies. An
unconditionally stable design guards against unexpected oscillations, which cause product malfunction.
K = (1-|S11|2-|S22|2+|Δ|2)/ (2*|S21.S12|) > 1
Where |Δ|= |S11.S22-S12.S21| > 1
(1)
C. Matching Network:
For linear systems, the condition for maximum power transfer is obtained when the impedance of the circuit
receiving a signal has an equal resistance and an opposite reactance of the circuit sending the signal. In the
mathematics of complex variables, this relationship is known as the complex conjugate. The complex conjugate
of a complex number is obtained by simply reversing the sign of the imaginary part. Here Z* denotes the
complex conjugate of Z; thus, for linear systems the condition for maximum power transfer is when
ZL = ZS*.
The location of the load becomes crucial in the choice of circuit configuration for the purpose of matching. The
load can have three distinct possibilities.
Case I: The load is located inside the (1+jx) circle i.e., resistance unity circle
Solution 1: shunt L and series C
Solution 2: shunt C and series L
Case II: The load is located inside the (1+jb) circle i.e., conductance unity circle
Solution 1: series L and shunt C
Solution 2: series C and shunt L
Case III: The load is located outside the (1+jx) and (1+jb) circle.
In this case, there are four solutions possible, as shown in Fig.3.
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International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
Fig.3. Smith chart solution for case III
Solution 1: series C and shunt C
Solution 2: series C and shunt L
Solution 3: shunt C and series C
Solution 4: shunt C and series L
Considering all three cases, case III has the highest flexibility because it has highest number of design choices to
suite the designer‟s needs.
III. SIMULATION AND MEASUREMENTS RESULTS
The supply voltage, VDD for this simulation is 3.0 V and drain current, Idd is 29.47 mA. Supply input power is
„0 dBm‟. After amplification the resultant power around 4 dBm achieved. The circuit diagram as shown in
Fig.4.
Fig.4. Circuit schematic of power amplifier
m3
freq=3.500GHz
StabFact1=1.298
1.34
1.32
m3
StabFact1
1.30
1.28
1.26
1.24
1.22
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
freq, GHz
Fig.5. Stability factor calculation
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International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
m2
freq=3.500GHz
S(2,2)=0.036 / 47.758
impedance = 52.423 + j2.820
m1
freq=3.500GHz
S(1,1)=0.010 / -19.650
impedance = 50.995 - j0.359
S(2,2)
S(1,1)
m2
m1
freq (500.0MHz to 4.000GHz)
Fig.6. Input and output matching coefficients
The stability factor (K) of the transistor is 1.298, so the transistor in unconditionally stable as shown in Fig.5.
After designing the input and output matching the coefficients are S (1, 1) and S (2, 2) respectively as shown in
Fig.6.
m7
freq= 3.500GHz
dB(var("S"))=-13.415
(1,1)
m8
freq= 3.500GHz
dB(var("S"))=-15.243
(1,2)
m9
freq= 3.500GHz
dB(var("S"))=-9.419
(2,2)
m10
freq= 3.500GHz
dB(var("S"))=7.607
(2,1)
m10
10
dB(var("S"))
0
m9
m7
m8
-10
-20
-30
-40
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
freq, GHz
Fig.7. S-Parameters of an amplifier
20
0
dBm(Pout)
-20
-40
-60
-80
-100
-120
-140
-180
-160
-140
-120
-100
-80
-60
-40
-20
0
dBm(Pin)
Fig.8. Output power Vs Input power of amplifier
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International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
m1
RF_pwr= -5.000
hb_comp..dbm_out=1.457
optIter=197
m2
RF_pwr= -5.000
dB_gain=6.457
optIter=197
m2
m1
10
PAE1
dB_gain
hb_comp..dbm_out
0
-10
-20
-30
-40
-50
-50
-45
-40 -35
-30
-25 -20
-15 -10
-5
0
5
RF_pwr
Fig.9. Results of gain and PAE of the amplifier
Eqn dB_gain=hb_comp..dbm_out-hb_comp..RF_pwr
m3
RF_pwr= -5.000
hb_comp..dbm_out=1.457
optIter=197
20
10
line
hb_comp..dbm_out
m3
0
-10
-20
-30
-40
-50
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
RF_pwr
Fig.10. Power calculation at 1dB compression point
Eqn line=hb_comp..RF_pwr+dB_gain[0]
The small signal gain is calculated by using S(2,1), input and output return losses are calculated by S(1,1) and
S(2,2) respectively. The all S-Parameter values are taken from the Fig.7. The final result of an amplifier is
shown in Fig.8. i.e., output power is increasing as input power increases.
The gain compression results are obtained by using the XDB compression technique. The resultant outputs are
6.457 gain and 1dB compression output power is 1.457, which are shown in Fig.9 and Fig.10.
IV. CONCLUSION
The 3.5 GHz power amplifier were designed for wireless application by using 0.30 μm GaAs technology with a
gate width of 250 μm and 10 fingers has been presented. Software ADS was used in the designing process. It
has been demonstrated that at a 3.0 V drain voltage, the amplifier has achieved 17.69 dB small-signal gain S21,
input and output return loss of -13.41 dB and -9.41dB, with power-added efficiency (PAE) for 3.5GHz power
amplifier. The designed PA are in unconditionally stable condition due to the stability factor for the PA are
higher than 1 at the whole range of frequency. In order to improve the performance of the system and achieve a
higher output power, the matching system should be designed in a specific way.
R S. Publication (rspublication.com), [email protected]
Page 147
International Journal of Computer Application
Issue 4, Volume 2 (March - April 2014)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
REFERENCES
[1] Gholamreza Nikandish, “A Design Procedure for High-Efficiency and Compact-Size 5–10-W MMIC Power
Amplifiers in GaAs pHEMT Technology”, IEEE Transactions on Microwave Theory and Techniques, vol. 61,
no. 8, August 2013.
[2] Chen Li, “Design and Simulation of a Ku-Band MMIC Power Amplifier”, Sixth International Conference on
Genetic and Evolutionary Computing, 2012.
[3] Kevin W. Kobayashi, “An 8-W 250-MHz to 3-GHz Decade-Bandwidth Low-Noise GaN MMIC Feedback
Amplifier With > +51-dBm OIP3”, IEEE Journal of solid-state circuits, vol. 47, no. 10, October 2012.
[4] D. Schwantusche, “A 56-65 GHz High-power Amplifier MMIC using 100 nm AlGaN / GaN Dual-gate
HEMTs”, 6th European Microwave Integrated Circuits Conference, 2011.
[5] Rasidah S., “3-Stage 15 GHz p-HEMT Power Amplifier Design for MMIC Applications”, IEEE
International Conference of Electron Devices and Solid-State Circuits, 2010.
[6] Renato Negra, “Study and Design Optimization of Multiharmonic Transmission-Line Load Networks for
Class-E and Class-F K-Band MMIC Power Amplifiers”, IEEE Transactions on Microwave Theory and
Techniques, vol. 55, no. 6, June 2007.
Author Biographies
Mr. Sharath Babu Kamsali is pursuing his M. Tech 4thsem in Digital communication Eng.,
Telecommunication Dept., R.V. College of Engineering, Bangalore and his areas of interests are
wireless communications, RF and microwave engineering.
Mrs. P.Shanthi has 13 years of teaching experience at UG levels and 2 years of research experience.
She had co-authored 6 research papers in journals and conferences. Her research interests are in the
areas of RF and MMIC Design, VLSI Design.
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