A 77 GHz mHEMT MMIC Chip Set for
Automotive Radar Systems
Dong Min Kang, Ju Yean Hong, Jae Yeco Shim, Jin-Hee Lee,
Hyung-Sup Yoon, and Kyung Ho Lee
Amonoltduc microwave integrated circuit (MMIC) chip
set constsdng of a power amplifier, a driver amplifier, and a
frequency doubler has been developed for automotive
radar systems at 77 GHz. The chip set was fabricated using
a 0.15 J.IIIl gate-length fuGaAsJ1nAlAs/GaAs metemorpbtc
high electron mobility transistor (mHEM'I) process based
III a 4-indt substrate. The power amplifier demonstrated a
measured small signal gain of over 20 dB n-om 76 to 77
GHz with 15.5 dBm output power. The chip size is 2 nnn x
2 mrn. The driver amplifier exhibited a gain of23 dB over
a 7600 77 GHz band with au output power of13 dBm. The
chip size is 2.1 nnn x 2 llllIL The frequency doubler
achieved an output power of --6 dBm at 76.5 GHz with a
conversion gain of -16 dB for an input power of 10 dBm
and a 38.25 GHz input frequency. The chip size is 1.2 nnn
x 1.2 llllIL This :MNllC chip set is suitable foc the 77 GHz
automotive radar systems and related apphcattons in a W-
baud.
Keywords: Automotive radar, :M],!llC, :NllIE1.IT, 77
GHz, amplifier, doubler.
M,"-"aipt rec6ved s ept.30;revi' edNov 17,2004
Dct1g Min Kang !phme + 82 42 860 1592, errro kdm1597@etrireh-j Ju Yean Hm g
(errro jyhong@etri.reh-j J", Yeah :1lim (email jyshm@t1ri .rehj Jin-Hre Lre (ffll"J
jintdee@ttri.reh-j Hymg-Sup Yom (email h'Yoon@t1rireh-j ,.-,j Kyung Ho Lee (fflloi1
khl259@etri.reh-) ""withBasicRe'e----ir----.:,---".--'t'
[ Frequency
L_:_~~:~~ _vco
Fig. 1. A generalized block diagram of the RF front-end of an
automotive radar system.
Fig . 3. Cross-sectional SEM of the passivated 0.15 /-till gate-
length mHEMI with a wide head I-shaped gate.
134 Dong Min Kangetal. ETRI Journal, Volume 27, Number 2, April 2005
• h21
e MSG/MAG
10010
Frequency (GHz)
•
•
•
•.. -.
• •
••
•
30
10
m
u
~ 20
iii(')
Fig. 6. Typical current gain, Ihz]l, as a function of frequency for
the 0.15 urn gate-length mHEMT device.
40,,-- - - - - - .--- - - - - - .--- ..----,
III. Circuit Design and Experimental Results2.01.51.0
v: (V)
0.5
10
Figure 4 shows drain-to-source current Om) as a function of
drain-to-source voltage (Vds) for the 0.15 urn GaAs mHEMT
devices. As shown in Fig. 3, the devices exhibit a good pinch-
off characteristic at a drain voltage of 2 V The drain saturation
current Oms) measured at Vds = 2 V and Vgs = 0 V is 38 rnA.
The threshold voltage (VtiJ is defmed by a linear extrapolation
of the square root of drain current versus gate voltage to zero
current. Vth was measured as -0.9 V
40 r----------------------,
30
;;:
E. 20
0.25 ,----~-_,__~---,--~--r----,--~__, 800
1.Power Amplifierand DriverAmplifier
A 4-stage MMIC power amplifier (PA) anddriver (DA) were
designed by using mHEMT devices of2-fmger 100 urn (2flOO)
and 4-finger 200 urn (4:1200). In order to increase the stability of
the mHEMT device, negative feedback was employed by a
resistor network. In the case of employing parallel feedback, the
gainwas decreased to some extent. There are some advantages
such as a broadband and a remarkably increased stability. In
addition, the effect of the feedback is to make the input and
output impedance more convenient for matching. The MMIC
amplifiers were designed as single-ended 4-stage types. The first
two stages used mHEMTs with a 100 urn gate width and
operated as class A amplifiers for gain consideration, while the
last two stages employed 200 urn devices for power and
efficiency requirements and operated at class A. All input/output
matching, interstage matching, and biasing networks were
included in the MMIC design In each stage of the MMIC, a
microstrip line, an open stub, and a capacitor are connected
between the HEMT and an input/output node to achieve both a
good return loss and a good rejection characteristic of the
undesired frequency bandwidth All grounded parts of the PA
were processed by via-holes. The front- and back-side
dimensions of the via-holes were 60 fim and 120 urn,
respectively. A microstrip thin film capacitor provided by ETRI
librarywas applied to DC-block circuits for isolationbetween the
stages and the combination of RF signals. The bias networks
consisted of high impedancetransmission lines, with decoupling
capacitors, serving as RF short circuits. Also, the gate bias
circuits were designed using a 580 Q NiCr resistor to obtain low-
gainflatness for the operating frequency. The circuit simulation
was accomplished by the use of the harmonic balance simulator
700 E
E600 ()j
E.500 Q)
o
c;
400 -tl
::J
U
300 6
o
(/)
200 ~
f-
100
0.5o-0.5
:". ~
/ e,
e ,
I •
e •f 0 . ---.
e J' 'i J' e~
f p ..
• 0 •I cl e
• p •D •
c ••
-1.0
000 i1IL-~--'----~---'----~~"'!'!!!!-..---.Jo
-1.5 1.0
0.05
0.20
- 0.10
"" 0.15
~
Fig. 5. The extrinsic transconductance and drain-to-source current
(Ids) as a function ofgate-to-source voltage (Vgs) .
v; (V)
Fig. 4 . Drain-to-source current (Ids) as a function of drain-to-
source voltage (Vds) for the 0.15 urn gate-length mHEMT
device.
The extrinsic transconductance (&n) and drain-to-source
current Om) as a function of gate-to-source voltage (Vgs) at 2 V
ofdrain voltage were measured and are shown in Fig. 5.
The maximumg.,was measuredas 700 mS/mmat Vg; = - 0.5 V
and VcI;=2 V The typical current gain (Ihzl!) as a function of
frequency for 0.15 x 100 f.ilIlz mHEMT devices is shown in Fig.
6. The cut-off frequency (fT) was obtained from the
extrapolation of the Ihzll to unity using a -6 dB/octave slope,
and the maximum frequency of oscillation (frnax) was extracted
from small signal parameters. The fT and frnax of the devices
were 130 and 230 GHz, respectively.
ETRI Journal, Volume 27, Number 2, April 2005 Dong Min Kang et al. 135
(a) Small signal gain (S21), input return loss (S11), and output return
loss (S22) as a function of frequency (50 to 100 GHz) for the
fabricated MMIC PA
100908070
Frequency (GHz)
60
30
S21
20
iii"
~ 10
N
N
(/)
""0 0C
'"
(/)
-10
N
(/)
-20
with the HP root model for the active device. The external DC
biasing conditions of Ve and Vg were 1.5 V and - 0.3 V,
respectively, and the total current consumption ofthe MMIC PA
was 180mA. In the case of the DA, the external DC biasing
conditionsofVd and Vg were 1.5V and - 0.4 V,respectively, and
the total current consmnption was 150 rnA.
The on-wafer measurement was performed using an HP
PNA N5250A 1l0GHz network analyzer. The circuit
schematics and photographs of the fabricated MMIC PA and
DA are presented in Figs. 7 and 8, respectively.
The PA demonstrated a measured small signal gain of over
20 dB from 76 to 77 GHz with a 15.5 dBm output power. The
chip size was 2 mm x 2 mm. The DA exhibited a gain of23 dB
over a 76 to 77 GHz band with an output power of 13 dBm.
The chip size was 2.1 mm x 2 mm. The measurement results
of the fabricated MMIC PA and DA are presented in Figs. 9
and 10, respectively.
(b) Photograph of the MMIC PA
(a) Circuit schematic of the MMIC PA
(a) Circuit schematic of the MMIC DA
Fig. 7. The circuit schematic and photograph of the MMIC power
amplifier.
(b) Photograph of the MMIC DA
25...-----------------------,
15t------------=:*3~~....
-+- Pout(dBm) at 76GHz
__ Power gain (dB) at76GHz
5I-_---::Ir-s;j~----___.,-.- Pout (dBm) at76.5 GHz
-+- Power gain (dB) at76.5 GHz
__ Pout (dBm) at77GHz
-+- Power gain (dB) at77GHz
-17 -15 -13 -11 -9 -7 -5 -3 -1
Pin (dBm)
(b) Output power and power gain as a function of input power at 76 to
77 GHz 1 tone for the fabricated MMIC PA
Fig. 8. The circuit schematic and photograph of the MMIC driver
amplifier. Fig. 9. Measured results of the MMIC power amplifier.
136 Dong Min Kang et al. ETRI Journal, Volume 27, Number 2, April 2005
25,- ---,
Vd
OUT
1---+---1 f-O
(a) Circuit schematic of the MMIC frequency doubler
IN
o----t
Recently reported 77 GHz PA results of other studies are
compared with this work in Table 1. Our PA results
demonstrated the highest output power and gain among all the
reported 77 GHz MMIC PAs for automotive radar systems
using 0.15 J-Lm GaAs HEMTs .
2. Frequency Doubler
Figure 11 shows the circuit schematic and photograph of the
frequency doubler. We designed an input circuit and output
circuit to match at 38.25 GHz and 76.5 GHz, respectively. The
input matching circuit fulfills the requirements of stabilization
in the whole frequency range, matching the fundamental at
38.25 GHz and the optimum load at 76.5 GHz. The parallel
combination of resistor and capacitor to stabilize the mHEMT
was used for the input match at 38.25 GHz. In the output
matching circuit, a radial stub was necessary to achieve a high
suppression of the fundamental in the output signal of more
than 30 dEc. The output was matched at 76.5 GHz with the
long open stub, which was also used for the suppression of
100908070
Frequency (GHz)
60
Fig . 10. Measured results ofMMIC driver amplifier.
(a) Small signal gain (S21), input return loss (S11), and output return
loss (S22) as a function of frequency (50 to 100 GHz) for the
fabricated MMIC DA
(b) Output power and power gain as a function of input power at 76 to
77 GHz 1 tone for the fabricated MMIC DA
30
m
:s
N
N
(f)
-o
c;
'"
(f)
N
(f)
-20
-30
50
m 20
:s
c;
'iii
Ol
Q; 15
'"0D-
oll
E 10
rn ..... Pout (dBm) at 76 GHz
:s ...... Powergain(dB) at 76 GHz
'S 5 ..... Pout (dBm) at 76.5 GHz0
D- -.- Powergain (dB) at76.5 GHz
__ Pout (dBm) at 77 GHz
..... Powergain (dB) at77 GHz
Table I. Comparison of the data of previously published W-band
PAs with this work.
Frequency Process Pout Gain Chip size
Ref(GHz) (All GaAs based) (dBrn) (dB) (rnrn')
71-80 0.15 flrnpHEMT 12 13.5 1.5 x 1.2 1
77 0.15 flrnpHEMT 14.5 8.5 0.5 x 0.6 6
76.5 0.15 flrnpHEMT 14 13 1.5 x 1.2 7
76.5 0.13 flrn pHEMT 15 10 2xl 8
76 0.12 flrn pHEMT 13 11 2xl 9
77-78 0.1 flIll pHEMT 21.5 12 3x2 10
This76-77 0.15 flrnpHEMT 15.5 20 2x2
work
(b) Photograph of the MMIC frequency doubler
Fig . II . The circuit schematic and photograph of the MMIC
frequency doubler.
ETRI Journal, Volume 27, Number 2, April 2005 Dong Min Kang et at, 137
~,
~ e
....... Pln v s Pmf ,
""
~ e --0- Pin v 5 G:
""
~W
'"
0 ~"
0 ~ "m
"~ ~"
~ , ~ , e
0
0
" ~"
-z
~"
c , , e a to
Pin (dBm)@38.25 8Hz
Fig. 12. Measured output power and conversion gain of the
frequency doubler as a function of the input power
level at 38.25 GHz.
Table 2. Comparison of the data of previously published frequency
doublers with this work,
Fun dam ental
Fre quency Process Gc Chip size
sorcresoon (mm'') RefCGHz) (All GaAs based) (dB) (dBc)
38.2Sn6. 5
0.2 flffi X 320 um
-11.3 l Ox 1 25 2pH EMT
38.Sn 7 0 12 pm x 100 um ~ n n
:MESFET
0 15 pm x 100 um This
38.2Sn6.S ~" 37 1.2x 1.2mHEMT work
the fimdamental. The operating conditions were near the pinch-
off region so that high, even harmonic power levels were
generated. The external DC biasing conditions er v , and Ve
were 1.5 and -0.7 V, respectively, and the total current
consumption was 8 mA..
Figure 12 shows the measured output power and «nversicn
gain of the frequency dcubler as a function of the input power
level at 38.25 GHz The frequency doubler achieved an cutput
power of- 6 dBm at 76.5 GHzwith a «nversicn gain of-16 dB
fer an input power of 10 dBm and a 38.25 GHz input frequency.
The frequency dcubler also achieved a fi.ndamental suppression
of37 dBc in a 76.5 GHz cutput frequency. The chip size was
1.2 nun x 1.2 mm Table 2 shows a comparison of the data of
previously published frequency doublers with this work,
IV. Conclusion
This paper describes the successful development of an
138 Dong Min Kang et al
11NIIC chip set for automotive radar systems using EIRI's
0.15 urn InGaAslInAlAs/GaAs mHEMT technology on a 4-
inch 100 urn thick GaAs substrate. The chip set consists of a
power amplifier, a driver amplifier, and a frequency doubler.
This 11NIIC chip set is suitable for 77 GHz autanctive radar
systems and related applications in a W-band
References
[1] K. Kamozaki et al., "A 770Hz TiR MJv.IIC Cbip Set fer
Automotive Radar Systems," GaAs IC flfmp. Digest, 1997, pp.
275-278.
[2] J. Udonoto et al.,"A38!T7 0Hz MJv.IICTransmitter Cbip SEt fer
Automotive Appliceticns," IEEE M'T]:.S Digest, 2003, W. 1229-
1232.
[3] H. S. Yoon et 31., "0.15 J..lIll Gate Length InAlAslInGaAs Power
Metamcphic HEMT 00 Oak Substrate with Extremely Low
Noise Characteristics," Int l Con! IPRM; M ay 2oo3 , pp. 114-117.
[4] K Shinohara et al., "Extremely High-Speed Lattice-Matched
InGaAs!InAlAs High Electron Mobility Transistors with 472
0Hz CutalIFrecpency," Jpn. J.Appl. Phye., yd. 41 , Apr. 2002,
W. L437-L439.
[5] Y C. C1Iouet 31., "High Reliabilityof0.1 J..lIll InGaAs'InAlAs1nP
HEMTMJv.IICs 00 3-inch JnP Substrate," Intl Con! IPRM, May
2001,pp.618-621.
[6] A. 'Iessmann et 31., "A 770Hz GaAspHEMTTransceiverMJv.IIC
for Automotive Sensor Applications," Ga4s r flfmp. Digest,
1999,pp. 207-210.
[7] H Kondoh et 31., "77 GHz Fuily-MJv.IIC Automotive FOIWard-
Locking Rader;" Ga4s IC flfmp. Digest, 1999,pp. 211-214.
[8] H. J . Siweris et 31., "A Mixed Si and GaAs Cbip SEt for
Millimeter-Wave Automotive Radar Front-Ends;" RFIC Symp.
D gest ,2000, pp. 191-194.
[9] H. J. Siweris et al., 'Low-Cost Oak pHEMT MMIC's for
Millimeter-Wave Sensor Appliceticns," IEEE Trans.MIT, yd. 46,
1998,pp.2560-2567.
[10] H. Y Chang et 31., "A 77-0Hz MJv.IIC Power Amplifier fer
Automotive Radar Applications," IEEE Mi crowave and Wire!e:z
Components Letters, vd.13, 2003, W. 143-145.
[11] D. C. Caruth et al., "Low-Cost 38 and 77 GHz Cl'W MJv.IICs
DoingIon-ImplentedGa/ts MESFETs," IEEE MIT-S Digest, yd.
2,2000, pp. 995-998.
ETRI Joornal, Volume 27, Number 2, April 2005
Hyung-Sup Yoon received the BE degree in
electronic materials engineering from Kwang
Woon University, Korea , in 1980, and the ME
and PhD degrees in 1984 and 1991 in applied
physics from Inha University, Korea. He joined
ETRl in 1984. From 1984 to 1992, he was
involved in developing silicon processes and
devices. Since 1993, he has been a principal researcher in the
Department of Compound Semiconductors in ETRl. His current
research interests include the process development, fabrication, and
characterization of low noise GaAs and InP-based HEMT devices for
millimeter wave MMlC applications.
Jin-Hee Lee received the BS degree in physics
from Youngnam University,Korea, in 1980, and
the MS and PhD degrees from the same
University in 1982 and 1987. He joined ETRl in
1984. From 1984 to 1992, was involved in
developing fme-line lithography, multi-level
interconnection, and a fabrication process of
GaAs MESFETs. In 1993, he was dispatched to University ofTokyo in
Japan for one year to do internationalresearch activities. After returning
to ETRl, he has been involved in the development of high speed devices
and their integrated circuits. He is now a principal member of the
Research Staff in the Department of Compound Semiconductors in
ETRl. His current research interests inc
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