IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 31, NO. 10, OCTOBER 1996
1419
Low Phase Noise Millimeter-Wave Frequency
Sources Using InP-Based HBT MMIC Technology
Huei Wang, Senior Member, IEEE, Kwo Wei Chang, Liem T. Tran, Member, IEEE, John C. Cowles, Member, IEEE,
Thomas R. Block, Eric W. Lin, Member, IEEE, G. Samuel Dow, Member, IEEE, Aaron K. Oki, Member, IEEE,
Dwight C. Streit, Senior Member, IEEE, and Barry R. Allen, Member, IEEE
Abstract— A family of millimeter-wave sources based
on InP heterojunction bipolar transistor (HBT) monolithic
microwave/millimeter-wave
integrated
circuit
(MMIC)
technology has been developed. These sources include 40GHz, 46-GHz, 62-GHz MMIC fundamental mode oscillators,
and a 95-GHz frequency source module using a 23.8-GHz InP
HBT MMIC dielectric resonator oscillator (DRO) in conjunction
with a GaAs-based high electron mobility transistor (HEMT)
MMIC frequency quadrupler and W-band output amplifiers.
Good phase noise performance was achieved due to the low
1/f noise of the InP-based HBT devices. To our knowledge,
this is the first demonstration of millimeter-wave sources using
InP-based HBT MMIC’s.
I. INTRODUCTION
H
IGH frequency and low phase noise oscillators are
key components in millimeter-wave (MMW) systems.
Although several monolithic oscillators operating at MMW
frequencies have been reported using high electron mobility
transistor (HEMT) technology [1]–[3], their phase noise performance has been limited by the high intrinsic
noise
associated with HEMT devices. On the other hand, GaAsbased heterojunction bipolar transistors (HBT’s) have shown
lower
noise, making them suitable for high frequency
oscillators with reduced phase noise, as demonstrated by the
reported 46-GHz HBT dielectric resonator oscillator (DRO)
[4].
InP-based HBT’s have demonstrated promising high frequency performance for both discrete devices and circuits
[5]–[6] because of the superior transport properties of InPbased materials when compared with GaAs-based HBT’s.
Furthermore, they exhibit lower
noise than GaAs HBT’s
because of the lower surface recombination velocity in InPbased materials and the absence of DX centers in the emitter
[7]–[8]. A comparison of phase noise performance between
GaAs- and InP-based HBT monolithic microwave/millimeterwave integrated circuit (MMIC) oscillators using the same
circuit topology at 19.5 GHz has shown that InP-based HBT
VCO’s demonstrate a 10-dB phase noise improvement over
conventional Al Ga As/GaAs HBT VCO’s at 1 MHz offset
[9]. The motivation of this work is to develop low phase noise
Manuscript received January 22, 1996; revised April 15, 1996. This work
is supported by MIMIC Phase 2 Program (Contract No. DAAL01-91-C-0156)
from ARPA and Army Research Laboratory.
The authors are with TRW, Electronic Systems and Technology Division,
Redondo Beach, CA 90278 USA.
Publisher Item Identifier S 0018-9200(96)06989-2.
sources at millimeter-wave frequencies up to W-band using
InP HBT MMIC technology for future system applications.
This paper presents several fundamental mode MMW InPbased MMIC oscillators including a 40-GHz, a 46-GHz, and
a 62-GHz oscillator. A 95-GHz frequency source module
has also been developed using a 23.8-GHz InP HBT MMIC
DRO with an external DR in conjunction with a GaAs-based
HEMT MMIC frequency quadrupler [10] and W-band output
amplifiers. To our knowledge, this is the first demonstration
of frequency sources with good phase noise performance at
MMW frequency ranges using InP HBT MMIC technology. In
Section II, we will discuss the InP HBT device characteristics.
The MMW source design will be presented in Section III.
Section IV illustrates the measured performance and is followed by a brief summary in Section V.
II. DEVICE CHARACTERISTICS
The InP-based HBT MMIC’s are fabricated on a 2″ diameter
InP substrate grown by MBE and utilizes a 1- m fully selfaligned process using nonalloyed refractory ohmic contacts
and conventional wet etching to define the device active areas.
The refractory TiPtAu contacts to highly doped InGaAs yield
10
cm
a reliable low contact resistance (less than 5
while not alloying and diffusing into the semiconductor material. The InAlAs/InGaAs HBT epitaxial layer structure shown
in Fig. 1 features InGaAs collector and base regions with a
smoothly graded emitter-base junction. This process has the
capability to integrate HBT, p-i-n, and Schottky diodes on
the same InP substrate using the base-collector HBT material
for the active areas. It is noted that the Schottky diode has a
vertical cathode and anode junction as well as a low turn-on
noise and low
voltage ( 0.2 V) which results in low
required LO power for mixer applications [9]. A 1 10 m
quad emitter HBT has a typical common emitter current gain
of 30 and a collector breakdown voltage
of 11 V.
10 A/cm and
V,
At a current density of 5
of
the device exhibits a unity current gain frequency
of
60 GHz and a maximum frequency of oscillation
120 GHz. The small signal equivalent circuit model and model
10 m quad emitter HBT are shown
parameters of the 1
in Fig. 2.
The measured low frequency collector noise spectra of
both GaAs- and InP-based HBT devices shows that the InP
HBT possesses a noise spectral density which is lower and
which does not contain the burst noise signature present in the
0018–9200/96$05.00  1996 IEEE
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IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 31, NO. 10, OCTOBER 1996
Fig. 1. The InP-based HBT device profile. The process integrated HBT, p-i-n, and Schottky diodes on the same InP substrate.
Fig. 2. The linear small signal model and parameters of the 1
quad emitter HBT device.
2 10 m2
GaAs HBT’s (Al Ga As) [16]. For equal collector current
densities, the InP HBT had a shorted-base collector noise
spectral density of 3
10 pA /Hz at 1 kHz compared to
the GaAs HBT, which exhibited a spectral density of 2 10
pA /Hz at 1 kHz. These
noise levels are consistent with
the previous comparison of 19 GHz MMIC VCO’s, which
indicated that an InP HBT VCO had superior phase noise to
a GaAs HBT VCO of the same topology (10 dB better phase
noise performance at 1 MHz offset) [9].
III. MMW SOURCE DESIGN
A. Fundamental Frequency Oscillator Design
The 40-, 46-, and 62-GHz MMIC oscillators are implemented in similar common base topologies using 1 10 m
quad emitter HBT’s as the active devices. Fig. 3(a) shows the
circuit schematic diagram of the 62-GHz monolithic oscillator.
The 40- and 46-GHz oscillators utilize a similar topology and
follow the same design procedure, and therefore we simply use
the 62-GHz oscillator to describe the design. The resonator of
the oscillator is formed by the on-chip microstrip lines. The
oscillation frequency is adjusted by tuning the base current.
The output power is coupled out of the collector through
microstrip edge coupled lines. Radial stubs provide RF bypass
for the bias lines, while thin-film resistors and metal-insulatormetal (MIM) capacitors are used for the bias networks. The
substrate is thinned and polished to a thickness of 100 m and
via holes are wet-etched to provide low inductance ground
connections.
The design procedure follows the example illustrated in
[11]. A short stub RF ground provided by the quarter wavelength radial stub from the base of the HBT is used as a
series feedback element to bring the device to an unstable
region. As observed in Fig. 3(b), the reflection coefficient
looking into the collector from 59.5 to 60.5 GHz was plotted
in the expanded Smith chart with a magnitude of about 2.7.
The linear small signal device model was used to ensure the
correct start-up conditions at the oscillation frequency of 60
GHz, which are
(1)
and
(2)
where
is the impedance looking into the device collector
and
is the impedance looking into the coupled line
and output port as shown in Fig. 3(a). Since the quarter-wave
coupled lines can be treated as a real impedance transformer
and transfer the 50 output load to a low real impedance at
60 GHz, the phase of
was designed near to the real axis
in order to meet the oscillation condition (2) at 60 GHz as
shown in Fig. 3(b). To achieve a good output power of the
oscillator, the negative resistance looking into the collector is
designed to be near three times that of the resistance looking
into the output load, i.e.,
(3)
WANG et al.: LOW PHASE NOISE MILLIMETER-WAVE FREQUENCY SOURCES
(a)
1421
(a)
(b)
Fig. 3. (a) The schematic diagram of the 62-GHz MMIC oscillator. (b) The
simulated reflection coefficient 0in looking into the collector from 59.5 to
60.5 GHz plotted in the expanded Smith chart.
(b)
Models for passive elements were obtained from full-wave
EM analysis [12] to overcome the inaccuracies of quasistatic models at MMW frequencies. The simulated
is
at 60 GHz.
Fig. 4(a)–(c) shows the photographs of the 40-, 46-, and 62GHz monolithic oscillators. The oscillators have a common
size of 2.0
1.5 mm As can be observed in the chip
photographs, the 46- and 62-GHz oscillators have an identical
circuit topology and the 40-GHz oscillator uses MIM capacitor
for RF ground instead of radial stub because of physical size
constraints. Also, an open stub at the HBT collector is added
to the 40-GHz oscillator chip for more design flexibility. The
length of the stub can be adjusted to determine the oscillation
frequency during the circuit design.
B. 95-GHz Source Module Design
The block diagram of the -band source module is shown
in Fig. 5. It consists of a 23.8 GHz InP-based HBT DRO,
driving a 23.5 to 94 GHz HEMT frequency quadrupler, a band three-stage HEMT output amplifier, and another -band
single-stage HEMT output amplifier.
The 23.8-GHz DRO is comprised of an InP HBT MMIC
oscillator chip and an off-chip DR. The MMIC oscillator chip
(c)
Fig. 4. Photographs of the (a) 40-GHz MMIC oscillator, (b) 46-GHz MMIC
oscillator, and (c) 62-GHz MMIC oscillator.
with a chip size of 1.2
1.1 mm is shown in Fig. 6. The
oscillator chip is a common base design using a 1 10 m
quad emitter HBT device. The two conditions (1) and (2) at the
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IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 31, NO. 10, OCTOBER 1996
Fig. 5. The block diagram of the 95-GHz source module.
Fig. 7. The photograph the 95-GHz source module.
Fig. 6. The photograph the 23.8-GHz oscillator MMIC chip.
oscillation frequency of 23.8 GHz need to be simultaneously
met again, where now
is the impedance looking into the
input port of the HBT MMIC oscillator chip and
is the
impedance looking into the microstrip line coupled to the offchip DR. The DR, which is placed on a 5-mil thick Al O
substrate and coupled through a terminated 50- microstrip
line has a diameter of 104 mil, a height of 54 mil, and a
relative dielectric constant
of 37. The unloaded -value
of the DR provided by the data sheet from the vendor is about
2000.
The frequency quadrupler and output amplifier MMIC chips
are identical to those components used in the previously reported -band source [13]. Fig. 7 shows the photograph of the
complete module with the top cover open. The complete source
module was assembled in a hermetically sealed package.
Ribbon bonds and 50- microstrip lines were used to connect
the MMIC chip interfaces. A specially designed -band lowloss hermetic glass-bead feed-through probe transition was
used to couple the signal from microstrip line of the output
amplifier to the output waveguide. The measured loss of this
transition is about 1 dB.
IV. MEASUREMENT RESULTS
A. Fundamental Frequency Oscillators
The fundamental frequency oscillators were diced and
mounted in test-fixtures for testing. For the 46- and 62GHz oscillators, antipodal finline transitions on 125- m
thick fused silica substrate were used to couple the signal
from the oscillator output microstrip lines to the waveguides,
while coaxial -connector was utilized for the 40-GHz. The
insertion loss of the -band finline-to-microstrip back-to-back
transitions is 1.2 dB.
The spectrum analyzer and power meter were used to test
output power and oscillation frequencies first. The spectrum
analyzer LO phase noise appeared to be too high for accurate
oscillator phase noise measurement; to improve the measurement accuracy, the phase noise performance was evaluated via
a single-oscillator phase-noise measurement technique using a
delay line as an FM discriminator [14]–[15].
Fig. 8(a) presents the oscillation spectrum of the 62-GHz
MMIC oscillator, which represents the highest frequency
fundamental-mode oscillator ever implemented using HBT
devices. The effects of the bias tuning on the oscillation
frequency and output power are shown in Fig. 8(b) and (c) for
the 40- and 62-GHz oscillators. In Fig. 8(b), a tuning range
of 300 MHz centered around 62.4 GHz was observed for
the 62-GHz oscillator. Compared with the simulated 60-GHz
oscillation frequency, there is a 2.4-GHz frequency shift. This
could be due to the HBT device model accuracy limitation
from the frequency extrapolation, since we only took the Sparameters up to 40 GHz for the InP HBT device modeling.
The 40-GHz oscillator has a tuning range of 200 MHz with
center frequencies of 39.9 GHz as shown in Fig. 8(c), while
the 46-GHz oscillator has 300 MHz with center frequencies
of 46.2 GHz.
The maximum output power of 4, 4, and 5 dBm were
V for the
obtained at 62.2, 46.0, 40.2 GHz under
is around
three oscillators. The nominal collector current
16 mA for the 1 10 m quad emitter HBT, and therefore
the dc power consumption is around 40 mW for all three
oscillator chips. The phase noise performance of 40- and 62GHz oscillators as functions of the offset frequencies away
from center frequencies is plotted in Fig. 9. The 62-GHz
oscillator exhibits 78 dBc/Hz at 100 kHz offset and 104
dBc/Hz at 1 MHz offset, while the 40-GHz oscillator has 84
dBc/Hz at 100 kHz offset and 111 dBc/Hz at 1 MHz offset.
B. 95-GHz Source Module
The 23.8-GHz MMIC HBT oscillator chip using a quad
emitter InP HBT device was first tested on wafer. A measured
input return gain of 3–5 dB from 23.5 to 24.5 GHz was
WANG et al.: LOW PHASE NOISE MILLIMETER-WAVE FREQUENCY SOURCES
1423
(a)
(a)
(b)
Fig. 9. The phase noise versus offset frequency for the (a) 40- and (b)
62-GHz oscillator.
(b)
(c)
Fig. 8. (a) The oscillation spectrum of the 62-GHz MMIC InP-based oscillator chip. (b) The oscillation frequency and output power versus base current
at 2.5-V collector voltage for the 62-GHz, and (c) 40-GHz oscillator.
Fig. 10. The measured return gain of the 23.8-GHz MMIC oscillator chip
from 15 to 30 GHz.
obtained as shown in Fig. 10 at the bias condition of
V
and
mA. This ensures the potential of oscillation with
an off-chip DR. A 23.8-GHz cylindrical DR and the MMIC
HBT oscillator chips were assembled in a -band test fixture
to form the DRO with an SMA output connector. The DRO
demonstrated an output power of 5 dBm at 23.8 GHz with a
phase noise of 94 dBc/Hz at 100 kHz.
The complete 95-GHz source module as shown in Fig. 8
was directly measured via the waveguide output port. The
source module shows an output power more than 10 dBm at
95.2 GHz with a phase noise of 82 dBc/Hz at 100 kHz offset
and 113 dBc/Hz at 1 MHz offset. The phase noise versus
offset frequency from 1 kHz to 1 MHz is plotted in Fig. 11.
The phase noise performance is more than 20-dB phase noise
improvement at 1 MHz offset compared to the 94-GHz source
module using GaAs based HBT VCO [13]. The total dc power
consumption of this module is about 400 mW.
Table I summarizes the performance of these MMW frequency sources. It is noted that the 62-GHz oscillator is the
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IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 31, NO. 10, OCTOBER 1996
ACKNOWLEDGMENT
The authors would like to thank M. Yu, N. Hudson, and
S. Esparza for the module and chip testing help, S. Chan,
W. Brunner, and D. I. Stones for the W-band waveguide to
microstrip line transition development effort, D. C. W. Lo for
his coordination of the mask layout, and M. Biedenbender
for the GaAs HEMT MMIC chip processing. Thanks also go
to the members of the RF Product Center of TRW for their
technical support. Special thanks go to Dr. S. W. Chen for his
discussions for the design of the 23.8-GHz MMIC oscillator
chip.
Fig. 11. The phase noise versus offset frequency for the 95-GHz source
module.
TABLE I
SUMMARY OF MEASURED PERFORMANCE FOR
THE InP-BASED MMW FREQUENCY SOURCES
highest frequency fundamental mode oscillator ever reported
using bipolar transistor with a phase noise performance 18-dB
better than reported 55-GHz HEMT free-running VCO [3] and
4-dB higher than the reported 55-GHz HEMT DRO at 1 MHz
offset [3]. Also, the 95-GHz source module shows a 23-dB
phase noise improvement at 1 MHz offset compared to the
GaAs based 94-GHz source module [13].
V. SUMMARY
We have reported the recent development of MMW frequency sources, including 40-, 46-, 62-GHz fundamental-mode
oscillators and a 95-GHz source module, all based on InP HBT
technology with low phase noise performance due to the low
noise of the HBT device.
intrinsic
The 62.4-GHz MMIC reported in this paper represents the
highest frequency fundamental-mode oscillator implemented
using HBT devices. We have also reported the recent development of the 95-GHz source module using a -band
InP HBT MMIC DRO. This module is packaged in a hermetically sealed housing and demonstrates low phase noise
performance. The encouraging low phase noise results of
the 95-GHz source module are also attributed to the DRO
DR. To our knowledge, this is the
design using a high
first report of MMW-sources using InP-based HBT MMIC
technology.
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1425
Huei Wang (S’83–M’87–SM’95) was born in
Tainan, Taiwan, R.O.C. on March 9, 1958. He
received the B.S. degree in electrical engineering
from National Taiwan University, Taipei, Taiwan,
R.O.C. in 1980, and the M.S. and Ph.D. degrees
in electrical engineering from Michigan State
University, East Lansing, in 1984 and 1987,
respectively.
During his graduate study, he was engaged
in the research on theoretical and numerical
analysis of electromagnetic radiation and scattering
problems. He was also involved in the development of microwave remote
detecting/sensing systems. He joined the Electronic Systems and Technology
Division of TRW Inc., Redondo Beach, CA, in 1987. He has been responsible
for MMIC modeling of CAD tools, MMIC testing evaluation and design. He
visited the Institute of Electronics, National Chiao-Tung University, Hsin-Chu,
Taiwan, in 1993 to teach MMIC related topics and returned to TRW in 1994.
He is currently in charge of the development for monolithic millimeter-wave
integrated circuits and subsystems in MAFET Program (APPA funded).
Dr. Wang is a member of Tau Beta Pi and Phi Kappa Phi.
Eric W. Lin (M’90) was born in Seattle, WA on
June 23, 1967. He received the B.S. degree in electrical engineering and computer science from the
University of California, Berkeley in 1988, and the
M.S. and Ph.D. degrees in electrical and computer
engineering from the University of California, San
Diego in 1989 and 1994, respectively. His doctoral
research was on GaAs- and InP-based modulationdoped field-effect transistors for microwave and
millimeter-wave mixing applications.
In 1994, he joined TRW in Redondo Beach, CA
as a Member of the Technical Staff in the Design and Technology Development Department. He has been involved in the design and development
of various MMIC components from X- through W-band, and his interests
also include compound semiconductor device fabrication and nonlinear device
modeling.
Kwo Wei Chang received the B.S. degree in electrophysics from the National
Chaio Tung University, Hsinchu, Taiwan, and the M.S. and Ph.D. degrees in
electrical engineering from the State University of New York, Stony Brook,
in 1977, 1981, and 1985, respectively.
From 1985 to 1989, he was a member of Technical Staff in the Microwave
Receiver Group of David Sarnoff Research Center, Princeton, NJ, where he
was responsible for the design and development of receiver components and
systems. In 1989, he joined TRW, Redondo Beach, CA, to work on the
development of high performance mixers and millimeter-wave MMIC’s. He
was the responsible engineer for the design and development of the TRW
first automotive radar. His present assignment is the Section Manager for
millimeter-wave sensors. He is currently interested in the areas of low cost
MMIC packaging and wireless communication systems.
Liem T. Tran (M’86) received the B.S. degree in applied physics from the
California Institute of Technology Pasadena, CA, and the M.S. degree in
electrical engineering from the University of California at Berkeley.
He has been at TRW, Redondo Beach, CA, since 1988 working on GaAs
and InP-based HBT’s.
John C. Cowles (S’86–M’95) was born in São
Paulo, Brazil, in 1965. He graduated summa cum
laude with a B.S. degree in electrical engineering
from the University of Pennsylvania, Philadelphia,
in 1987. He received the M.S. and Ph.D. degrees
in 1989 and 1994, respectively, in electrical engineering from the University of Michigan, Ann
Arbor.
In 1994, he joined the TRW RF Product Center,
Redondo Beach, CA, were he is working currently
on the fabrication and characterization of advanced
GaAs and InP HBT technologies for MMIC’s, analog, and high speed digital
circuits.
Thomas R. Block was born in St. Louis, MO in 1962. He received the B.S.
in electrical engineering from The University of Texas at Austin in May 1984.
He continued his studies at the graduate level in the Electrical Engineering
Department of The University of Texas at Austin under the supervision of Dr.
B. G. Streetman. He received the M.S. in engineering in 1986 and the Ph.D.
in engineering in 1991 from The University of Texas at Austin.
In 1991 he joined TRW, Redondo Beach, CA, as a Senior Member of
Technical Staff engaged in molecular beam epitaxy growth of compound
semiconductors for both research and production. He is involved in the growth
of GaAs-based HBT’s, HEMT’s, and MESFET’s and InP-based HBT’s and
HEMT’s. In 1995 he became the manager of the Advanced Materials Section
at TRW.
G. Samuel Dow (S’78–M’82) was born in Tainan, Taiwan on April 12, 1954.
He received the diploma in electrical engineering from Taipei Institute of
Technology, Taipei, Taiwan in 1974 and the MSEE degree from University
of Colorado, Boulder, in 1981.
From 1981 to 1983 he was with Microwave Semiconductor Corporation
where he was responsible for the first demonstration of 0.5 W output power
at 20 GHz with the GaAs MESFET technology. From 1984 to 1987 he
was a staff engineer with Hughes Aircraft Company, Microwave Products
Division, where he engaged in the modeling and characterization of MESFET
power devices, design of wideband and high efficiency power amplifiers, and
millimeter-wave receiver components. He joined TRW in 1987. From 1987
to 1995, he was the Section Head of the EHF/RF MMIC section responsible
for the design of microwave and millimeter-wave IC’s. He is currently a
Senior Staff Engineer engaged in the development of advanced millimeterwave sensor products employing millimeter-wave HEMT and HBT MMIC
devices.
Aaron K. Oki (M’85), for a photograph and biography, see this issue, p. 1418.
Dwight C. Streit (S’81–M’86–SM’92), for a photograph and biography, see
this issue, p. 1418.
Barry R. Allen (M’84) was born in Cadiz, KY,
on November 5, 1947. He received the B.S. degree
in physics and the M.S. and Sc.D. degrees in electrical engineering from the Massachusetts Institute
of Technology, Cambridge, MA in 1976, 1979, and
1984, respectively.
He joined TRW, Redondo Beach, CA, in 1983
as a Senior Staff member and has held a number
of positions since then. Since 1983 he has been
involved in all aspects of microwave and millimeterwave circuit and device development. His main
interests are low noise receiving systems, millimeter wave systems, and
accurate circuit modeling. From 1975 to 1983, he was a member of the
Research Laboratory of Electronics at MIT, both as an undergraduate and
as a graduate Research Assistant in radio astronomy. While at MIT, he was
responsible for the development of room temperature and cryogenic low noise
receiving systems for 300 MHz to 43 GHz. From 1991 until 1995 he was
assistant program manager for design and advanced technology on the ARPA
funded MIMIC Phase 2 program. He is currently a Senior Scientist in the
Electronic Systems and Technology Division.
In 1991, Dr. Allen became a TRW Technical Fellow in the Space and
Defense Sector. For contributions to the application and manufacturing of
GaAs MMIC’s, he was awarded TRW’s Chairman’s Awards for Innovation
in 1992 and 1993. He has published several papers on circuit applications of
heterostructure devices and MMIC’s.