AN ANALOG PREDISTORTION LINEARIZER DESIGN

posed predistortion circuit for the case
of CW two-tone signals, where the
output power is 37.7 dBm/tone. The
test frequencies are 1.854 and 1.855
GHz. The improvements of IMD 3 and
IMD 5 are 42.87 and 23.95 dB, respectively.
Figure 10 shows the CDMA
1FA adjacent power ratio (ACPR) of
the HPA with and without the proposed
predistortion circuit. The output
power is 37 dBm and the test frequency
is 1.855 GHz. Figure 11 compares
the CDMA 4FA ACPR of the
HPA with and without the proposed
predistortion circuit, where the output
power is 30 dBm/FA and the carrier
frequencies are 1.8525, 1.85375,
1.85625 and 1.8575 GHz, respectively.
The improvements in ACPR are
10.25, 8.6 and 9.37 dB at f 0 ±885 kHz,
f 0 ±1.25 MHz and f 0 ±2.25 MHz, respectively.
The test signal generator is
ESG4433B from Agilent Technologies.
A signal similar to a carrier leakage
was observed at the center frequency
with this equipment.
CONCLUSION
In this article, a new type of analog
predistortion linearizer for controlling
individual intermodulation distortion
signals is proposed. The signal generators
generate and control predistorted
third and higher IM component signals
separately. The high order IM signals
are generated by using the main and
third-order IM signals at the input of
the generator. The proposed predistorter
structure offers the advantage of
little signal interference in small size
circuits and easy implementation. Using
the predistorted signals, the HPA’s
intermodulation distortion signals are
suppressed effectively. The test results
show that IMD 3 and IMD 5 are reduced
by more than 40 and 23 dB for
CW two-tone signals, respectively. The
predistorter improves the ACPR by
more than 10 dB for CDMA
(IS-95) 4FA signals. ■
ACKNOWLEDGMENT
This work was supported by the Research
Fund, Kumoh National Institute
of Technology, Gyungbuk, Korea.
References
1. P.B. Kenington, High Linearity RF Amplifier
Design, Artech House Inc., Norwood,
MA, 2000, pp. 341–420.
2. Y.C. Jeong, “A Design of Predistortion Linearizer
by Individual Order Control of Intermodulation
Distortion Signals,” PhD
Dissertation, Sogang University, 1996.
3. T. Nojima and T. Konno, “Cuber Predistortion
Linearizer for Relay Equipment in
800 MHz Band Land Mobile Telephone
System,” IEEE Transactions on Vehicular
Technology, Vol. 34, No. 4, Nov.1985.
4. S.A. Maas, Nonlinear Microwave Circuits,
Artech House Inc., Norwood, MA, 1988.
5. T.T. Ha, Solid-state Microwave Amplifier
Design, John Wiley & Sons Inc., Somerset,
NJ, 1981.
6. S.C. Cripps, RF Power Amplifiers for
Wireless Communications, Artech House
Inc., Norwood, MA, 1999.
TECHNICAL FEATURE
Young Kim received
his BSEE, MSEE and
PhD degrees in
electronics engineering
from Sogang
University, Seoul,
Korea, in 1986, 1988
and 2002, respectively.
In 2003, he joined the
school of electronics
engineering, Kumoh
National Institute of
Technology, Gumi, Korea. His interests include
the design of high power amplifiers and
linearization techniques, and RF and
microwave circuit analysis and design. He can
be reached via e-mail at youngk@kumoh.ac.kr.
Ik-Soo Chang
received his PhD
degree from Seoul
National University,
Seoul, Korea, in 1982.
He is currently a
professor at Sogang
University. He has
more than 20 years of
experience in RF and
microwave circuit
design.
Yong-Chae Jeong
received his BSEE,
MSEE and PhD degrees
in electronics
engineering from
Sogang University,
Seoul, Korea, in 1989,
1991 and 1996,
respectively. In 1998, he
joined the division of
electronics and
information engineering
at the Institute of Information and
Communication at Chonbuk National University,
Chonju, Korea. He is currently an associate
professor and chair of the Chonbuk University
IC Design Education Center (IDEC) WG, where
he teaches and conducts research in the areas of
microwave devices, base station amplifiers,
nonlinear devices and system linearizing
technology, and RFIC design.