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Proceedings ArticleDOI

A 3 rd - and 5 th -order intermodulation products generator for predistortion of base-station HPAs

20 Dec 2010-pp 217-220
TL;DR: The simulation and measured results show that the circuit can generate the IM3 and IM5 products effectively and suitable for use in predistortion of base-station HPAs.
Abstract: This paper presents the design of a circuit to generate 3rd- and 5th-order intermodulation (IM3 and IM5) products used for predistortion of base-station high power amplifiers (HPAs). The circuit employs a mixer constructed using two Schottky diodes as a nonlinear device to generate the IM3 products and another mixer of the same configuration to generate the IM5 products using the IM3 products generated. The circuit has been studied using a two-tone signal at a center frequency of 2.2GHz. The simulation and measured results show that the circuit can generate the IM3 and IM5 products effectively and suitable for use in predistortion of base-station HPAs.

Summary (2 min read)

INTRODUCTION

  • In the rapid development of High-data-rate wireless communication systems, there are increasing demands for high-linearity high power amplifiers (HPAs) to minimize signal distortion and hence data errors.
  • HPAs can be operated at low output powers to avoid nonlinearities, but the price to pay is very low efficiency, i.e. a waste of the output power of HPAs.
  • Among these technologies, analog predistortion, which feeds the inband intermodulation (IM) signals [5] [6] , the difference-frequency signals [7] or the harmonic-frequency signals [8] of the fundamental signals to the HPAs to improve the linearity, is relatively low cost with reasonable linearity improvement.
  • The injection of the difference-frequency or harmonic-frequency signals of the fundamental signals, known as the difference-frequency technique and harmonic-injection technique, respectively, generates some IM signals to suppress the unwanted IMDPs at the outputs of HPAs.
  • The mixers employ two Schottky diodes as the nonlinear device and can be tuned to generate the IM3 or IM5 products with other unwanted signal suppressed.

2.1 IM3 generation:

  • The signal at port #3 undergoes a phase shift of 90 o introduced by the λ/4-length transmission at the tone frequency before reaching the anti-parallel Schottky diodes, D1 and D2, which, according to (2), generates a mixing product of the IM3 products (3 rd -order term) and the twotone signal.
  • At port #4, the two-tone signal reflected from port #2 and the mixing products reflected from port #3 are summed together.
  • Since the two-tone signals reflected from port #2 and port #3 have a phase difference of 180 o and the variable resistor R can be used to make their amplitudes equal, the two-tone signals in port #4 can be canceled off.
  • The antiparallel Schottky diode circuit will have certain capacitive effects, causing a phase shift to the mixing product.
  • The effects can be canceled off by tuning the bias voltage V c at the varactors D3 and D4 to adjust the phase of the two-tone signal reflected from port #2.

2.2 IM5 generation:

  • Which are generated across the anti-parallel Schottky diode circuit.
  • Here, the authors choose these settings to suppress the IM3 products.
  • To remove the original twotone signal in port #3, the authors can simply use the two-tone signal with the same amplitude and 180 o phase and add it to the mixing products, as described later.
  • Thus the resultant signal mainly has the IM5 products.
  • The IM3 products generated are fed to a linear amplifier to obtain a proper power level and then to the power splitter.

III. SIMULATION AND MEASUREMENT RESULTS

  • Computer simulation tests using the Advanced Design Systems 2009 (ADS2009) has been used to assess the performance of the proposed IM5 and IM3 generator circuit shown in Fig. 2 .
  • The circuit has also been implemented on a PCB, Roger's RO4005C.
  • A two-tone signal with 2 MHz spacing at the center frequency of 2.2 GHz has been used in their studies.
  • The IM5 product at Output #2 is more than 10 dB higher than the two-tone signal and the other intermodulation products.
  • The design of a IM3 and IM5 order product generation circuit for predistortion of base station HPAs has been proposed, studied and implemented.

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A 3
rd
- and 5
th
-Order Intermodulation Products
Generator for Predistortion of Base-Station HPAs
X.L. Sun, S.W. Cheung and T.I. Yuk
Department of Electrical and Electronic Engineering, the University of Hong Kong
Hong Kong, China
Abstract—This paper presents the design of a circuit to
generate 3
rd
- and 5
th
-order intermodulation (IM3 and IM5)
products used for predistortion of base-station high power
amplifiers (HPAs). The circuit employs a mixer constructed
using two Schottky diodes as a nonlinear device to generate the
IM3 products and another mixer of the same configuration to
generate the IM5 products using the IM3 products generated.
The circuit has been studied using a two-tone signal at a center
frequency of 2.2GHz. The simulation and measured results
show that the circuit can generate the IM3 and IM5 products
effectively and suitable for use in predistortion of base-station
HPAs.
I. INTRODUCTION
In the rapid development of High-data-rate wireless
communication systems, there are increasing demands for
high-linearity high power amplifiers (HPAs) to minimize
signal distortion and hence data errors. Unfortunately, the
amplification processes of HPAs are highly nonlinear when
the HPAs are operated at high output powers. HPAs can be
operated at low output powers to avoid nonlinearities, but the
price to pay is very low efficiency, i.e. a waste of the output
power of HPAs. Therefore, linearity technologies such as
predistortion, feed-forward or feed-back [1-4], have been
developed to reduce the intermodulation distortion products
(IMDPs) at the outputs of HPAs. Among these technologies,
analog predistortion, which feeds the inband intermodulation
(IM) signals [5-6], the difference-frequency signals [7] or the
harmonic-frequency signals [8] of the fundamental signals to
the HPAs to improve the linearity, is relatively low cost with
reasonable linearity improvement. The injection of the
difference-frequency or harmonic-frequency signals of the
fundamental signals, known as the difference-frequency
technique and harmonic-injection technique, respectively,
generates some IM signals to suppress the unwanted IMDPs
at the outputs of HPAs. However, these techniques cannot be
used for narrowband HPAs which will block the injected
signal. Therefore, the method of feeding the inband
intermodulation (IM) signals is more practical [9]. When the
HPA is operating in a more nonlinear region in order to
obtain a higher output power, higher orders of the IM signals
are needed to suppress the IMDPs at the output in order to
maintain or obtain a better performance. Thus in using the
inband-signal-injection method, a circuit to generate the
higher order IM signals effectively is absolutely necessary.
The circuit to generate the high order IM signals is
complicated and very often also generates many unwanted
spurious which will degrade the predistortion performance.
In this paper, we propose a simple circuit to generate the
3
rd
- and 5
th
-order intermodulation (IM3 and IM5) products
using two identical mixers. The mixers employ two Schottky
diodes as the nonlinear device and can be tuned to generate
the IM3 or IM5 products with other unwanted signal
suppressed. The Agilent’s Advanced Design System 2009
(ADS2009) has been used to perform the design of the
mixers circuit and assess the performances in a two-tone test
at a center frequency of 2.2 GHz. For experimental
verification, the circuit has been implemented and tested. The
results show that the IM3 and IM5 products can be generated
effectively using the two mixers.
II. M
IXER CIRCUIT DESIGN
Fig. 1 shows the block diagram of our proposed mixer
circuit which consists of a 3-dB 90
o
hybrid coupler, a pair of
anti-parallel Schottky diodes (D1 and D2), two varactors (D3
and D4), an RF chock inductor L, a variable resistor R and a
λ/4-length transmission line.
14
λ
90
°
0
°
in
R
F
out
RF
Fig. 1 Block diagram of proposed mixer
The nonlinear characteristics of the anti-parallel Schottky
diodes, D1 and D2, are used to generate the required IM
products. The current flowing through D1 and D2 can be
represented as (1):
321
( ) {exp[ ( )] 1} {exp[ ( )] 1}
[()] [()]
{2 ( ) ... ...}
6(21)!
ss
n
s
It I kVt I kVt
kV t kV t
IkVt
n
+
=−
=+++ +
+
(1)
where V(t) is the signal across the anti-parallel Schottky
diodes, k is a constant and I
s
is the saturation current of the
diodes.
The 2010 International Conference on Advanced Technologies for Communications
978-1-4244-8876-6/10/$26.00 ©2010 IEEE
217

In (1), when the power level of V(t) is low, the 1
st
- and
3
rd
-order terms are dominant and other higher-order terms
can be neglected, so the current can be approximated as:
3
[()]
() {2 () }
6
s
kV t
It I kVt≈+ (2)
2.1 IM3 generation:
Assume the input signal, RF
in
, fed to the input port, port
#1, of the 3-dB 90
o
-hybrid coupler in Fig. 1 is a two-tone
signal with equal amplitude and a small frequency separation.
The 3-dB 90
o
-hybrid coupler divides the two-tone signal
equally but with a 90
o
-phase difference at ports #2 and #3.
The signal at port #3 undergoes a phase shift of 90
o
introduced by the
λ/4-length transmission at the tone
frequency before reaching the anti-parallel Schottky diodes,
D1 and D2, which, according to (2), generates a mixing
product of the IM3 products (3
rd
-order term) and the two-
tone signal. The mixing product is reflected back to port #3,
with the two-tone signal undergoing a further phase shift of
90
o
. At port #4, the two-tone signal reflected from port #2
and the mixing products reflected from port #3 are summed
together. Since the two-tone signals reflected from port #2
and port #3 have a phase difference of 180
o
and the variable
resistor R can be used to make their amplitudes equal, the
two-tone signals in port #4 can be canceled off. The anti-
parallel Schottky diode circuit will have certain capacitive
effects, causing a phase shift to the mixing product. The
effects can be canceled off by tuning the bias voltage V
c
at
the varactors D3 and D4 to adjust the phase of the two-tone
signal reflected from port #2.
2.2 IM5 generation:
We can generate the IM5 products using the same mixer
circuit of Fig. 1. Here, we first combine the original two-tone
signal and the IM3 products (with the generation described
previously) to form the fundamental signal:
[]
12
12 21
1
() (cos cos )
cos(2 ) cos(2 )
Vt a t t
bt t
ωω
ωω ωω
=+
+−+
(3)
where a and b are the amplitudes of the two-tone signal and
the IM3 products, respectively. Thus, the signal applied to
D1 and D2, which has a half power of (3), can be represented
as:
()
[]
12
2
12 21
cos cos
()
cos(2 ) cos(2 )
at t
Vt c
bt t
ωω
ωω ωω
⎧⎫
+
⎪⎪
=
⎨⎬
+−+
⎪⎪
⎩⎭
(4)
Substituting (4) into (2) and expanding the 3
rd
-order term
produce the two-tone signal, IM3, IM5, IM7 and IM9
products, respectively, as:
()
3
33 2 3 23
12
2
99 9 12
cos cos
64 4 2
sIk
ac abc abc ac t t
k
ωω
⎛⎞
+++ +
⎜⎟
⎝⎠
(5)
()()
33 33
3
12 21
23
2
93
44
cos 2 cos 2
912
6
2
s
bc ac
Ik
tt
abc bc
k
ωω ωω
⎛⎞
+
⎜⎟
⎜⎟
−+
⎜⎟
++
⎜⎟
⎝⎠
(6)
{}
33
22
12 21
9
( ) cos[(3 2 ) ] cos[(3 2 ) ]
64
sIk c
ab ab t t
ωω ωω
⋅⋅
⎡⎤
+−+
⎢⎥
⎣⎦
(7)
{}
33
2
12 21
9
cos[(4 3 ) ] cos[(4 3 ) ]
64
sIk c
ab t t
ωω ω ω
⋅⋅
⎛⎞
−+
⎜⎟
⎝⎠
(8)
{}
33
3
12 21
3
cos[(5 4 ) ] cos[(5 4 ) ]
64
sIk c
btt
ωω ω ω
⋅⋅
⎛⎞
−+
⎜⎟
⎝⎠
(9)
which are generated across the anti-parallel Schottky diode
circuit. In (7)-(9), it can be seen that if a (the amplitude of the
two-tone signal) is larger than b (the amplitude of the IM3
product), say, by 5 dB, then the IM5 product will have a
much a higher power level than both the IM7 and IM9
products in (8) and (9), respectively, which therefore can be
neglected. As a result, the mixing product then mainly
consists of the two-tone signal, IM3 and IM5 products given
by (5), (6) and (7), respectively, and is reflected to port #4 of
the coupler. The
λ/4-length transmission, bias voltage V
c
and
variable resistor R could be used to cancel either the two-
tone signal or the IM3 products, as explained previously, but
not both together, in port #3. Here, we choose these settings
to suppress the IM3 products. To remove the original two-
tone signal in port #3, we can simply use the two-tone signal
with the same amplitude and 180
o
phase and add it to the
mixing products, as described later. Thus the resultant signal
mainly has the IM5 products.
in
R
F
Fig. 2 Proposed IM5 and IM3 generation. A: attenuator; PS: phase shifter
Figure 2 shows the overall block diagram of the proposed
circuit for generating the IM3 and IM5 products. The input
two-tone signal is divided into three paths, Paths #1, #2 and
#3, via a 3-way power splitter. Path #1 directs the signal to
the input of Mixer #1 (with circuit shown in Fig. 1) to
generate the IM3 products. The IM3 products generated are
fed to a linear amplifier to obtain a proper power level and
then to the power splitter. In Path #2, the amplitude and
phase of the two-tone signal from the 3-way power splitter
are adjusted by an attenuator and a phase shifter, and then
combined with the IM3 products (from the splitter in Path #1)
in combiner #1 to produce the fundamental signal given by
(3). The fundamental signal is fed to Mixer #2 (which the
same structure as Mixer #1) to generate the IM5 products.
The values of a and b are adjusted so that a is large than b by
218

5 dB, for the reason described previously. (Simulation
studies have shown that the difference of 2 to 8 dB is
acceptable.) In Path #3, the amplitude and phase of the
original two-tone signal are adjusted by another set of
attenuator and phase shifter so that the adjusted two-tone
signal can be used to remove the two-tone signal at the
output of Mixer #2 using combiner #2. The required IM3 and
IM5 products used for predistortion are therefore obtained at
Output #1 and Output #2, respectively. Output #3 is a test
port used to study the mixing product from Mixer #2 without
removing the two-tone signal.
III.
SIMULATION AND MEASUREMENT RESULTS
Computer simulation tests using the Advanced Design
Systems 2009 (ADS2009) has been used to assess the
performance of the proposed IM5 and IM3 generator circuit
shown in Fig. 2. The circuit has also been implemented on a
PCB, Roger’s RO4005C. A two-tone signal with 2 MHz
spacing at the center frequency of 2.2 GHz has been used in
our studies.
Fig. 3 Simulated signal spectrum at Output #1 in two-tone test
Fig. 4 Measured signal spectrum at Output #1 in two-tone test
Figures 3 and 4 show the simulation and measured
spectra, respectively, at Output #1 of Fig. 2. For comparison,
the power levels of different tones in the spectra are shown in
Table I. The power level of the IM3 signal is more than 20
dB higher than that of the original two-tone signal and other
intermodulation products of high orders.
TABLE I. SIMULATED AND MEASURED IM3 SIGNAL
POWERS AT OUTPUT #1
Frequency (GHz)
Simulated power
(dBm)
Measured power
(dBm)
m1, 2.199 -39.7 -39.4
m2, 2.197 -13.1 -14.3
m3, 2.195 -37.2 -40.5
m4, 2.193 -33.5 -36.0
m5, 2,191 -40.9 -46.5
The simulated and measured spectra at test port Output
#3 of Fig. 2 are shown in Figs. 5 and 6, respectively. The
power levels of tones in these spectra are shown in Table II.
The IM5 products are more than 10 dB higher than the other
intermodulation products. However, the two-tone signal has
even a higher power level, about 5 dB higher than that of the
IM5 products and so must be suppressed.
Fig. 5 Simulated signal spectrum at test port Output #3 in two-tone test
Fig. 6 Measured signal spectrum at test port Output #3 in two-tone test
219

TABLE II. SIMULATED AND MEASURED IM3 SIGNAL
POWERS AT TEST PORT OUTPUT#3
Frequency (GHz)
Simulated power
(dBm)
Measured power
(dBm)
m1, 2.199 -25.2 -25.6
m2, 2.197 -39.0 -40.9
m3, 2.195 -28.6 -30.6
m4, 2.193 -39.9 -41.3
m5, 2,191 -38.6 -42.1
Figures 7 and 8 show the simulated and measured spectra,
respectively, of the IM5 products at Output #2 of Fig. 2. The
power levels of the output tones are shown in Table III.
Comparing the result in Fig. 6 with that in Fig. 8 shows that
the two-tone signal is suppressed by nearly 18 dBm using
Path #3 in Fig. 2. The IM5 product at Output #2 is more than
10 dB higher than the two-tone signal and the other
intermodulation products.
The proposed IM5 and IM3 generator circuits have been
tested for predistortion of a practical 10-W base-station HPA
using a two-tone signal. Results have that the predistorter can
reduce the IMDP3 and IMDP5 from 6.5 dBm and -8.5 dBm
to -10.67 dBm and -19.5 dBm, respectively.
Fig. 7 Simulated signal spectrum at Output #2 in two-tone test
Fig. 8 Measured signal spectrum at Output #2 in two-tone test
TABLE III. SIMULATED
AND MEASURED IM3 SIGNAL
POWERS AT OUTPUT#2
Frequency
(GHz)
Simulated power
(dBm)
Measured power
(dBm)
m1, 2.199 -44.6 -43.5
m2, 2.197 -41.0 -43.0
m3, 2.195 -30.6 -32.3
m4, 2.193 -41.9 -42.9
m5, 2,191 -40.4 -43.6
IV.
CONCLUTIONS
The design of a IM3 and IM5 order product generation
circuit for predistortion of base station HPAs has been
proposed, studied and implemented. Simulation and
measured results have shown that the IM3 and IM5 products
generated are 20 dB and 10 dB higher than other unwanted
spurious. Tests have also shown that the design can suppress
the IMDP3 and IMDP5 effectively in a practical base station
HPA.
R
EFERENCES
[1] K. J. Cho, et al, “Multi-order predistortion of power amplifiers using a
second harmonic based technique,” IEEE Microwave and Wireless
Components Letters, vol. 13, pp. 452-454, Oct. 2003.
[2] Sung Won Chung, Jack W. Holloway, and Joel L. Dawson, “Energy-
Efficient Digital Predistortion With Lookup Table Training Using
Analog Cartesian Feedback,” IEEE Trans. MTT., vol. 56, no. 10, pp.
2248-2258, 2008.
[3] S. Bounmaiza, and F. M. G.ahnnouchi, “Realistic Power Amplifiers
Characterization with Application to Baseband Digital Predistortion
for 3G Base Stations,” IEEE Trans. Microw. Theory Tech. vol. 50, no.
12, pp. 3016-3021, Dec. 2002.
[4] S. C. Cripps, “RF Power Amplifiers for Wireless Communications,”
Norwood, MA: Artech House, 2006.
[5] Yong-Sub Lee, Mun-Woo Lee, Sang-Ho Kam, and Yoon-Ha Jeong,
“A Transistor Based Analog Predistorter With Unequal Delays for
Memory Compensation,” IEEE Microwave and Wireless Components
Letters, vol. 19, pp. 743-745, Nov. 2009.
[6] M. X. Xiao, S. W. Cheung, and T. I. YUK,A Simple Mixer for
generating the 3
rd
-Order Intermodulation Products Used for HPA
Predistortion,” ICCS 2009, Romania, pp. 1-4.
[7] Modeste, M., Budimir, D., Moazzam, M.R. and Aitchison, C.S.,
“Analysis and practical performance of a difference frequency
technique for improving the multicarrier IMD performance of RF
amplifiers,” Technolofies for Wireless Applications, 1999. Digest.
1999 IEEE MTT-S Symposium, pp. 53-56
[8] Matsubara, H., Ishihara, K., Miyadai, N. and Nojima, T., “Anovel 3
rd
-
and 5
th
-order predistortion circuit for 2 GHz band WCDMA
amplifier,” APMC 2007, pp. 1-4.
[9] M. X. Xiao, S. W. Cheung and T. I. Yuk, ‘An RF predistorter for base
station HPAs of NADC system,” PIMRC 2009, Toky, pp.1587-1591.
220
Citations
More filters
Journal ArticleDOI
TL;DR: A design of dual-port IM generator that can generate dynamic IM reference for high-accuracy passive intermodulation measurement and a trimming strategy by using a compact terminal matching resistor is adopted to smartly regulate the IM tunable interval is presented.
Abstract: The high-accuracy passive intermodulation (PIM) measurement shows great significance in PIM quality checking and related researches. As the key point to guarantee the test accuracy, the IM reference is essential in realizing precise PIM calibration. This paper presents a design of dual-port IM generator that can generate dynamic IM reference for this demand. The proposed generator employs a cascaded coupling network consists of two couplers, while a reverse biased Schottky diode is working as a tunable reflection IM source. The bias voltage and coupling coefficient are introduced to regulate the quiescent operation points of diode and the IM signal excitation strength respectively, they work together to put the IM reference signal on a desired level. Specially, a trimming strategy by using a compact terminal matching resistor is adopted to smartly regulate the IM tunable interval. These configurations can promote the utilization of this proposed IM generator to be flexible not only for design engineers but also for commercial users. The test results demonstrate that this generator can provide the tunable IM3 whose dynamic range can reach about 30 dB@2x43 dBm, 50 dB@2 × 31 dBm. Meanwhile, the significance of bidirectional dynamic IM reference signals is demonstrated.

7 citations

References
More filters
Book
31 Mar 1999
TL;DR: In this paper, the authors present a power amplifier design for GHz frequency bands at GHz GHz frequency band with overdrive and overdrive-only overdrive modes, as well as a switch-mode Amplifier for RF applications.
Abstract: Linear PA Design. Conventional High-Efficiency Amplifier Modes. Class AB PAs at GHz Frequencies. Practical Design of Class AB PAs. Overdrive and the Class F Mode. Switching Mode Amplifiers for RF Applications. Switching PA Modes at GHz Frequencies. Signals, Modulation Systems, and PA Nonlinearities. Efficiency Enhancement Techniques. Power Amplifier Bias Circuit Design. Power Amplifier Architecture. PA Linearization Techniques.

2,060 citations


"A 3 rd - and 5 th -order intermodul..." refers background in this paper

  • ...Therefore, linearity technologies such as predistortion, feed-forward or feed-back [1-4], have been developed to reduce the intermodulation distortion products (IMDPs) at the outputs of HPAs....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a baseband digital predistorter lookup table was synthesized using the measured AM/AM and AM/PM curves without any need to perform additional analytical derivations and/or numerical optimizations.
Abstract: In this paper, a realistic, accurate, versatile, and thermal-free complex behavior test bed suitable for third-generation power-amplifiers characterization is proposed. Using this approach, a 90-W peak power amplifier based on Motorola-LDMOS class-AB transistors was measured under several signal excitations such as W-CDMA, cdma2000, and eight-tone signals. The results obtained show noticeable discrepancies compared to those measured using a vector network analyzer (HP-8510C) for both AM/AM and AM/PM curves. This test bed was also used for the investigation of the memory effect in RF power amplifiers. In the second part of this paper, the characterization results obtained by the test bed were used to design a digital predistorter for an LDMOS amplifier. A baseband predistortion accurate synthesis algorithm is presented. Indeed, a memoryless baseband digital predistorter lookup table was directly synthesized using the measured AM/AM and AM/PM curves without any need to perform additional analytical derivations and/or numerical optimizations. The predistorter synthesis procedure requires only one iteration, contrary to previous works, which need several iterations to obtain similar performances.

85 citations


"A 3 rd - and 5 th -order intermodul..." refers background in this paper

  • ...Therefore, linearity technologies such as predistortion, feed-forward or feed-back [1-4], have been developed to reduce the intermodulation distortion products (IMDPs) at the outputs of HPAs....

    [...]

Journal ArticleDOI
TL;DR: Energy-efficient low-complexity adaptive linearization for wideband handset power amplifiers (PAs) and energy-efficient lookup table training strategy resulting in a training energy of 1.83 nJ/entry for a 5-MHz bandwidth WiMAX orthogonal frequency division multiple access (OFDMA) transmission.
Abstract: We demonstrate energy-efficient low-complexity adaptive linearization for wideband handset power amplifiers (PAs). Due to power overhead and complexity, traditional wideband linearization techniques such as adaptive digital predistortion (DPD) thus far have not been used for wideband handset transmitters. Our energy-efficient lookup table training strategy resulted in a training energy of 1.83 nJ/entry for a 5-MHz bandwidth WiMAX orthogonal frequency division multiple access (OFDMA) transmission, which represents more than 40times improvement over state-of-the-art DPD implementations. Our experimental prototype transmitter achieves a maximum of 9.9-dB improvement of adjacent channel leakage power at 5.15-MHz offset with 22.0-dBm channel power in the 5-MHz bandwidth WiMAX-OFDMA transmission. This linearity improvement offers 26.5% savings in PA power consumption by reducing power backoff.

30 citations


"A 3 rd - and 5 th -order intermodul..." refers background in this paper

  • ...Therefore, linearity technologies such as predistortion, feed-forward or feed-back [1-4], have been developed to reduce the intermodulation distortion products (IMDPs) at the outputs of HPAs....

    [...]

Proceedings ArticleDOI
01 Jan 1999
TL;DR: In this paper, the authors present a difference frequency technique for IMD improvement in power amplifiers based on feeding the original two tone signals and a signal which frequency is the difference frequency of the fundamental signals in to the amplifier.
Abstract: This paper presents a difference frequency technique for IMD improvement in power amplifiers. The technique is based on feeding the original two tone signals and a signal which frequency is the difference frequency of the fundamental signals in to the amplifier. Theory, simulation and practical measurement are presented. The result of the related experiment which gave a two tones measurement of more than 40 dB reduction in the level of the third order IMD is reported.

24 citations


"A 3 rd - and 5 th -order intermodul..." refers background in this paper

  • ...Among these technologies, analog predistortion, which feeds the inband intermodulation (IM) signals [5-6], the difference-frequency signals [7] or the harmonic-frequency signals [8] of the fundamental signals to the HPAs to improve the linearity, is relatively low cost with reasonable linearity improvement....

    [...]

Journal ArticleDOI
TL;DR: In this article, a transistor-based analog predistorter with memory effect compensation is presented, where the nonlinearity of a gain amplifier generated by low supply voltage is used as an error generator.
Abstract: A transistor-based analog predistorter (APD) with memory effect compensation is represented. The nonlinearity of a gain amplifier generated by a low supply voltage is used as an error generator. The predistorted signal by the unequal-delayed nonlinear paths improves the linearity by compensating for memory effects of the power amplifier (PA). For verification, the proposed APD with three-branch nonlinear paths is implemented with a 30-W class-AB PA and tested using two-tone and various wideband code division multiple access (WCDMA) signals at 2.14 GHz. From the measured results, the proposed APD significantly improves the linearity of the PA with memory effects.

14 citations


"A 3 rd - and 5 th -order intermodul..." refers background in this paper

  • ...Among these technologies, analog predistortion, which feeds the inband intermodulation (IM) signals [5-6], the difference-frequency signals [7] or the harmonic-frequency signals [8] of the fundamental signals to the HPAs to improve the linearity, is relatively low cost with reasonable linearity improvement....

    [...]

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Q1. What are the contributions in "A 3- and 5-order intermodulation products generator for predistortion of base-station hpas" ?

This paper presents the design of a circuit to generate 3and 5-order intermodulation ( IM3 and IM5 ) products used for predistortion of base-station high power amplifiers ( HPAs ). The circuit has been studied using a two-tone signal at a center frequency of 2. 2GHz.