Microwave Solid State Power Amplifier Technology
Miroslav Kasal
Dept. of Radio Electronics
Brno University of Technology
Purkyňova 118, 612 00 Brno, Czech Republic
kasal@feec.vutbr.cz
Abstract—This paper is focused on our current research in the
field of power amplifier technology for microwaves, especially the
X-band. For this purpose we considered different active devices.
Unfortunately, we did not manage to obtain super modern GaN
transistors (chips) for these frequencies such as TGA2023-05
from TriQuint or module such as TGA-2554-GSG from the same
producer. Instead we used internally matched GaAs FETs from
Eudyna as well as GaAs module XP-1006A from Mimix.
Subsequently we have designed, built and tested three power
amplifiers with different active devices and output power of 4, 8
and 20 Watts on 10 GHz. In the paper we would like to introduce
design and completion of the amplifiers as well as test results.
The highest power we achieved by double stage with 90 degrees
3 dB hybrid couplers at the input and output. The microstrip
technique on PTFE substrate has been used. Critical parts of
layouts were optimized by using ANSYS modeling software. The
dc circuitry needs to be designed according to the proper time Figure. 1. TGF2023-05 linear model.
sequence and high dc currents. Corresponding cooling system
was taken into account.
Keywords—microwave amplifier; solid state power amplifier;
linear power amplifier;
I. INTRODUCTION
There are several application where high power on
microwaves frequencies is needed, for example radars or space
communication. An achievement of high power on these
Figure 2. Calculated s-parameters.
frequencies is neither simple nor cheap. In this paper we
considered narrow band linear power amplifiers. At present,
modern GaN chips are introduced [5] but are difficult to obtain,
especially in small quantities. For this purpose the standard
internally matched GaAsFETs are applicable. A problem there
is a low effectiveness of the power amplifier. In order to
achieve 6 – 7 dB small signal transistor gain, the power
amplifier should operate in class A [1][2]. That means a big
idle current. For this reason low efficiency and strong heat
dissipation occurs. The standard push-pull double acting
amplifier (in AB class) is critical from the balancing point of
view. The Doherty amplifier concept needs a peaking amplifier
in class C (low gain on the X-band) [3][7]. For this reason,
quadrature dual-acting stage is better for higher power
achievement but both halves are acting near to A class again.
II. LINEAR MODEL
Figure 3. TGF2023-05 input matching to 50 Ohms on frequency
Sets of expected parameters at recommended operating 10.37 GHz.
conditions including linear model are available for several
microwave devices. 1.25 mm Unit GaN Cell TGF2023-05 can
be shown as example [5], fig. 1.
Scattering parameters can be calculated from the model as
shown in fig. 2. Then matching to the 50 Ohms at the input can
be designed according to the linear model, fig. 3., as well as the
output. Model which includes microstrips matching circuitry is
shown in fig. 4. Calculated parameters of whole linear
amplifier can be seen in fig. 5. The small signal parameters of
linear power amplifier are as expected. The imitation stability Figure 6. Linear model of the single stage power amplifier with
criterion is fulfilled too. Large signal parameters like output FLM0910-4F
power and efficiency should be 43 dBm and 0.5 respectively.
Figure 4. Model of whole linear power amplifier with the chip TGF2023-05. Figure 7. Good matching at the both ends of the power amplifier achieved by
calculated stubs.
Figure 5. Small signal parameters of whole linear power amplifier based on
chip TGF2023-05.
III. SINGLE STAGE POWER AMPLIFIER Figure 8. Detail of matching stubs.
Internally matched microwave GaAsFETs allow to provide
relatively simple design of a single stage power amplifier, dissipated power is about 10 W. Proper dc circuitry design is
because operating class A tolerates to start the design with very important. The negative gate voltage has to come first
small signal analysis method [4]. This way we designed P1dB = before the drain positive voltage.
36 dBm amplifier for frequency 10.37 GHz. At idle current
about 0.65 IDSS expected efficiency was η = 0.3 and IM3 < 40
dB. Model of the linear amplifier with FLM0910-4F is shown IV. THREE STAGE POWER AMPLIFIER WITH MIMIX MODULE
in fig. 6. 50 Ohms input and output microstrips are equipped
with open end stubs. These stubs allow to find optimized Several producers have developed more stages MMIO
matching on both ends as can be seen in fig. 7. Finally the right power amplifiers usually for specific applications. Radars with
positions of the stubs were found experimentally, fig. 8. These adaptive antenna arrays are such an application. Each antenna
metrics were very close to the calculated ones. Heat sink with element has own power module and high radiated power is
small cooling fan was applied because the corresponding obtained as a sum of primary power contributions.
Mimix offers three stage 8.5-11.0 GHz GaAs MMIC power
amplifier giving large signal gain of 21 dB with a 40 dBm
saturated output power [6]. It also includes on-chip gate bias
circuitry. This MMIC uses 0.5 µm GaAs PHEMT device
model technology and is based upon optical gate lithography to
ensure high repeatability and uniformity. The low duty cycle is
recommended while this device is well suited for radar
application. We obtained the packaged device P1006-FA,
which comes in a 10 pin, high frequency, LCC flange package.
The built power amplifier is shown in fig. 9. Unfortunately, we
achieved only P1dB = 38 dBm and large signal gain about
17 dB. The efficiency was about η = 0.3.
Figure 11. Calculated parameters of the optimized 3 dB hybrid coupler.
Figure 9. Power amplifier with MMIO P1006-FA by Mimix.
Figure 12. High power linear power amplifier schematic.
V. HIGH POWER MICROWAVE AMPLIFIER
The aim of this project was to develop a power amplifier
with P1dB = 43 dBm and large signal gain about of 20 dB on
frequency 10.37 GHz. Selected concept of this amplifier is
three stage amplifier with last stage operating in quadrature
mode. Precisely designed 3 dB microstrip hybrid coupler is
essential for this mode. This configuration ensures a high
degree of isolation between the two output ports and the two
input ports at the input as well as at the output of the quadrature
stage.
Figure 13. Linear power amplifier with 43 dBm output power.
Active device of the first stage is EPA240B-100P from
Excelics Semiconductors. Next stage is set up with FLM0910-
4F and the last stage operates with two GaAsFETs FLM0910-
12. For good linearity and gain achievement all stages work in
class A.
Power amplifier schematic is shown in fig. 12 as well as its
final performance in fig. 13. P1dB output power has been
Figure 10. Optimized layout of 3 dB hybrid coupler for quadrature stage. achieved 43.2 dBm at IM3 < 40 dB and gain 19 dB. Total dc
current from 12 V power source is 8.2 A. The efficiency of the [2] S. C. Cripps, Advanced Techniques in RF Power Amplifier Design.
whole amplifier (all three stages) is about η = 0.2 and ARTECH HOUSE, INC., Norwood, MA, 2002
dissipation heating power about 80 W. For this reason the [3] A. Grebenikov, RF and Microwave Power Amplifier Design.
amplifier is mounted on a proper massive heat sink and cooled McGraw-Hill, London, 2005
by two 80 mm fans. The temperature is then up to 70o C at CW [4] J. C. Pedro, S. A. Maas, A Comparative Overview of Microwave and
operation. Microwave power amplifier test-bed in our Wireless Power-Amplifier Behavioral Modeling Approaches. IEEE
laboratory is shown in fig. 14. Transactions on Microwave Theory and Techniques, Vol. 53, No. 4,
April, 2005, pp. 1150-1163
[5] TriQuint: TGF2023-05 25 Watt Discrete Power GaN on SiC HEMT
(Datasheet). 9 pages. [Online], Cited 2012-10-10. Available at:
http://www.triquint.com/products/p/TGF2023-05
[6] Mimix: XP1006-FA 8.5-11.0 GHz GaAs Power Amplifier, Flange, 10
pin (Datasheet). 6 pages. [Online], Cited 2012-04-11. Available at:
http://www.hi-tesion.com/XP1006-FA.pdf
[7] A. Jayaraman, P. F. Chen, G. Hanington, L. Larson, and P. Asbeck,
Linear High-Efficiency Microwave Amplifiers Using Bandpass Delta-
Sigma Modulators. IEEE Microwave and Guided Wave Letters, Vol.
8, No. 3, March, 1998, pp. 121-123
Figure 14. Power amplifier test-bed measurement
VI. CONCLUSIONS
In this paper we introduced design and implementation of
several power amplifiers on microwave frequencies. Standard
GaAsFETs allow to carry out power amplifiers up to tens Watt
on 10 GHz. Operating class A of all stages makes it possible
to obtain suitable large signal gain but at low efficiency. On
the other hand a linear model can be applied for such power
amplifier design. We are excited to see a production of new
GaN devices which promise higher gain as well as higher
efficiency of the microwave power amplifiers at excellent
thermal stability.
ACKNOWLEDGMENT
This work was supported by Czech Grant Agency under
Grant P102/10/1853 “Advanced Microwave Components for
Satellite Communication Systems”. This research was
financially supported by the project CZ.1.07/2.3.00/20.0007
WICOMT in frame of the operational program Education for
competitiveness. The described research was performed in
laboratories supported by the SIX project, registration number
CZ.1.05/2.1.00/03.0072, operational program Research and
Development for Innovation.
REFERENCES
[1] F. H. Raab, P. Asbeck, S. Cripps, P. B. Kenington, Z. B. Popovic, N.
Pothecary, J. F. Sevic, and N. O. Sokal, Power Amplifiers and
Transmitters for RF and Microwave. IEEE Transactions on
Microwave Theory and Techniques, Vol. 50, No. 3, March, 2002, pp.
814-826
