Table Of Content~IEEE TRAN SACTI 0 NS ON
MICROWAVE THEORY
AND TECHNIQUES
A PUBLICATION OF THE IEEE MICROWAVE THEORY AND TECHNIQUES SOCIETY
MARCH 1995 VOLUME 43 NUMBER 3 IETMAB (ISSN 0018-9480)
PAPERS
Broadband Single- and Double-Balanced Resistive HEMT Monolithic Mixers ........................................... .
. . . . . . . . . . . . . . . . . , ................... T. H. Chen, K. W. Chang, S. B. T. Bui, L. C. T. Liu, G. S. Dow, and S. Pak 477
Small-Sized MMIC Amplifiers Using Thin Dielectric Layers .................................... S. Banba and H. Ogawa 485
Analytical Parameter Extraction of the HBT Equivalent Circuit with T-Like Topology from Measured S-Parameters
.................. ............ ..... ................................ ....... ... ... U. Schaper and B. Holzapfl 493
An Approach to Determining an Equivalent Circuit for HEMT's ......................................................... .
. . . . . . . . . . . . . . . . . . . . . . . . . . K. Shirakawa, H. Oikawa, T. Shimura, Y. Kawasaki, Y. Ohashi, T. Saito, and Y. Daido 499
A New Method to Determine the Source Resistance of FET from Measured S-Parameters Under Active-Bias €onditions
......................... ...... .. ......... .... ................................................. V. Sommer 504
Negative Photoresponse in Modulation Doped Field Effect Transistors (MODFET's): Theory and Experiment ........... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. A. Romero and P. R. Herczfeld 511
MMIC Compatible Lightwave-Microwave Mixing Technique ............................................................. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Paolella, S. Malone, T. Berceli, and P. R. Herczfeld 518
Optimum Design of Coplanar Waveguide for LiNb0 Optical Modulator ...................... X. Zhang and T. Miyoshi 523
3
A Quasi-Optical Mode Converter with a Bifocal Mirror ...................................................... C. T. latrou 529
High Performance Microshield Line Components ....................... T. M. Weller, L. P. B. Katehi, and G. M. Rebei;:; 534
Microwave Measurement of Surface Resistance by the Parallel-Plate Dielectric Resonator Method ..................... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. P. Mourachkine and A. R. F. Bare! 544
Nonlinear Mixed Analysis/Optimization Algorithm for Microwave Power Amplifier Design ........................... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F. Giannini, G. Leuzzi, E. Limiti, J. S. Mroz. and L. Scucchia 552
Scattering Optimization Method for the Design of Compact Mode Converters for Waveguides ......................... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T. ul Haq, K. J. Webb, and N. C. Gallagher 559
A Hybrid Phase Shifter Circuit Based on TICaBaCuO Superconducting Thin Films ..................................... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Subramanyam, V. J. Kapoor, and K. B. Bhasin 566
Synthesis of Octave-Band Quarter-Wave Coupled Semi-Tracking Stripline Junction Circulators ............. J. Helszajn 573
Mode Coupling in Coaxial Waveguides with Varying-Radius Center and Outer Conductors ............................ .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J. Shafii and R. J. Vernon 582
(Continued on back cover)
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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 43, NO. 3, MARCH 1995 477
Broadband Single- and Double-Balanced
Resistive HEMT Monolithic Mixers
T. H. Chen, Member, IEEE, K. W. Chang, S. B. T. Bui,
L. C. T. Liu, Member, IEEE, G. S. Dow, Member, IEEE, and S. Pak
Abstract- A double-balanced (DB) 3-18 GHz and a single MESFET mixer because it has a steeper variation characteristic
balanced (SB) 2-16 GHz resistive HEMT monolithic mixer have for the channel resistance between the off and on states and
been successfully developed. The DB mixer consists of a AI
a smaller re product value of the on-resistance and gate
GaAs/InGaAs HEMT quad, an active LO balun, and two passive
capacitance. This paper describes a single-balanced resistive
baluns for RF and IF. At 16 dBm LO power, this mixer achieves
the conversion losses of 7.5-9 dB for 4-13 GHz RF and 7.5-11 HEMT mixer which downconverts a 2 to 16 GHz RF to a
dB for 3-18 GHz RF. The SB mixer consists of a pair of 0.75 to 1.25 GHz IF and a double-balanced resistive HEMT
AIGaAs/InGaAs HEMT's, an active LO balun, a passive IF balun mixer which downconverts a 3 to 18 GHz RF to a 0.75 to
and a passive RF power divider. At 16 dBm LO power, this
1.25 GHz IF.
mixer achieves the conversion losses of 8-10 dB for 4-15 GHz RF
and 8-11 dB for 2-16 GHz RF. The simulated conversion losses
of both mixers are very much in agreement with the measured
results. Also, the DB mixer achieves a third-order input intercept
(IP3) of +19.5 to +27.5 dBm for a 7-18 GHz RF and 1 GHz IF at II. DEVICE MODELING
a LO drive of 16 dBm while the SB mixer achieves an input IP3 In a HEMT amplifier, the HEMT operates in its saturation
of +20 to +28.5 dBm for 2 to 16 GHz RF and 1 GHz IF at a 16
region and is used to transform the signal voltage applied
dBm LO power. The bandwidth of the RF and LO frequencies
are approximately 6:1 for the DB mixer and 8:1 for the SB mixer. to the gate into the drain current. The drain current, or the
The DB mixer of this work is believed to be the first reported DB drain voltage if a load impedance were present at the drain, is
resistive HEMT MMIC mixer covering such a broad bandwidth. varied by changing the gate voltage. However, in a resistive
(passive) HEMT mixer, the HEMT operates in its ohmic
(linear) region and is used as a variable resistor. The unbiased
channel resistance is varied by changing the gate voltage.
I. INTRODUCTION
Ideally, the HEMT is treated as a switch controlled by the LO
A T THE PRESENT time, Schottky diode mixers are signal applied to the gate. The RF signal is then sampled at a
the most commonly used mixers in microwave sys rate determined by the LO frequency to achieve the frequency
tems. However, they have relatively poor intermodulation and conversion.
spurious response properties due to their strongly nonlinear Fig. l shows the nonlinear equivalent circuit of the HEMT
characteristics. Although various circuit schemes have been device. Because of the large voltage swing of the LO signal
proposed to improve the intermodulation performance of the applied to the gate, the gate-to-source and gate-to-drain char
diode mixers [l]-[4], they either are not practical for wide
acteristics are modeled by two diodes, allowing the effects
frequency band application or require a massive LO power. of the gate current and the nonlinear gate capacitances to be
Three-terminal devices, such as MESFET's and HEMT's, taken into account. The gate diode models are constructed
when used as mixing elements can achieve better performance from the measured s-parameters and gate current-voltage
and require less LO power than diode mixers [5]-[7]. Both
characteristics. The drain-to-source current is modeled by a
MESFET's and HEMT's can be used as mixing elements in voltage-controlled current source. Most nonlinear device mod
either an active or a resistive mode. The resistive mixer has els available in commercial nonlinear simulators are mainly
the advantages of low noise figure, high two-tone third-order designed for active-mode operation [ 10]-[ 12] and cannot
intermodulation intercept point, and low de power consump accurately describe the device behavior in the linear region
tion when compared with a corresponding active mixer [8]. In
where the resistive HEMT mixer operates. To overcome this
addition, a resistive HEMT mixer requires lower LO power problem, an user-defined model is developed and implemented
and can operate over a wider frequency range than a resistive
in Libra of EEsof for this application. Fig. 2 shows the user
defined model of the voltage-controlled current source, Ids·
The current source's parameters are extracted by curve-fitting
Manuscript received January 20, 1993; revised June 6, 1994.
to measured I-V curves as shown in Fig. 3. This model
T. H. Chen was with TRW/ESG, ETD, M511065, Redondo Beach, CA
90278 USA. He is now with Hexawave Photonic Systems, Inc., Hsin Chu, accurately describes device characteristics in both linear and
Taiwan, ROC. saturation regions. Other circuit element values are determined
K. W. Chang, S. B. T. Bui, L. C. T. Liu, G. S. Dow, and S. Pak are with
by curve-fittting to measured s-parameters of the HEMT
TRW/ESG, ETD, M5/1065, Redondo Beach, CA 90278 USA.
IEEE Log Number 9407458. device.
0018-9480/95$04.00 © 1995 IEEE
478 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 43, NO. 3, MARCH I995
lgd
Lg Rg Cgd Rd
L11
rds
lgs
Cgp
Fig. 1. Nonlinear equivalent circuit of the HEMT device.
0.25-µm gate length are connected in a ring as the mixing
devices. The HEMT acts as an variable resistor whose value
is modulated by the LO signal voltage applied to the gate.
The frequency conversion is achieved when a pair of balanced
LO signals are used to switch ON and OFF in tum between
two pairs of HEMT's of the quad while another pair of
balanced RF signals are applied to two opposite nodes among
the four of the quad. At the same time, two 180° out of
phase IF signals appear at another two opposite nodes and
are combined by the IF balun. Fig. 4(b) shows the circuit
schematic of the single-balanced mixer. The mixer circuit
consists of a pair of 320-µm AIGaAs/InGaAs HEMT's, an
active LO balun, a passive IF balun and a passive RF power
divider. Its principle of operation is similar to DB mixer's
i - 0, 1.2. 3, 4
except that only two devices are used here and the IF signals
Fig. 2. User-defined model. appear at the same nodes as the ones RF signals are applied
to.
Due to its capability of insertion gain and very broad
III. BALANCED MIXER DESIGN bandwidth, an active LO balun is used for both DB and
For a mixer to achieve broadband operation, the frequency SB mixers. The active LO balun is composed of two four
ranges of one or more pairs of its signals (RF, LO, and IF) section distributed amplifiers with one in common gate and
often overlap each other. Under the circumstances, a double the other in common source configuration. The total device
balanced (DB) or single-balanced (SB) mixer topology is periphery is 504 µm and the balun consumes about JOO
required to provide isolation between the pair of signals hav mA current at 4-V drain voltage. To minimize the mixer's
ing overlapped frequencies and spurious rejection over wide noise figure, passive baluns are used at the RF and IF ports
frequency range [9]. Although the DB mixer configuration for the DB mixer whereas a passive power divider and a
outperforms the SB one in terms of port-to-port isolation and passive balun are used at the RF and IF ports, respectively,
undesired signal rejection, the SB mixer configuration can op for the SB mixer. The RF balun for the DB mixer is com
erate over wider frequency band than its DB counterpart. This prised of a two-section Wilkinson power divider and a pair
is because one of the bandwidth limiting baluns in a DB mixer of Lange couplers. One of the Lange couplers is loaded
is replaced by a power divider, which generally has wider with the open circuits while the other is loaded with the
bandwidth than a balun, in a SB mixer. Consequently, both short circuits. This balun can operate over a 4: 1 bandwidth.
mixer configurations are used in the broadband monolithic For low IF frequencies, a compact lumped element balun
mixer designs. is preferable to a distributed one for the IF port. In this
Fig. 4(a) shows the circuit schematic of the double-balanced design, a lumped-element ratrace hybrid is chosen for the
mixer. The mixer circuit consists of an AlGaAs/lnGaAs IF balun due to its small size and up to 50% bandwidth.
HEMT quad, an active LO balun and two passive baluns, The IF balun is implemented with planar spiral inductors
RF and IF. Four 160-µm AlGaAs/InGaAs HEMT's with and MIM capacitors. For the SB mixer, the same two-section
CHEN et al.: BROADBAND SINGLE- AND DOUBLE-BALANCED RESISTIVE HEMT MONOLITHIC MIXERS 479
I-U
Plot~
300.0
275.0
250.0
225.0
200.0
I
d 175.0 ·············-·. ············· ...
3
150.0
n
m 125.0
A
100.0
75.0
50.0
25.0
0.0
0.0 0.5 1.0 1.5 2.0 2.5 J.0 J.5
Ud3 ln Uo \l3
wafer c2925 mea!)urcd-pu l~c
4x80/t_r4cJ mode I ed
Fig. 3. Measured and modeled l-V curves of a 320-~im HEMT.
RF
LO
J~+m r !
f'.
..,,..r ..
IF
Vd Vg ~r IF Vg
(a) (b)
Fig. 4. (a) Circuit schematic of SB resistive HEMT mixer and (b) circuit schematic of DB resistive HEMT mixer.
Wilkinson power divider and IF balun as those in the DB IF signal. The diplexer consists of a high-pass and a low
mixer are used at the RF and IF ports, respectively. The pass filter implemented with planar spiral inductors and MIM
power divider can achieve a nearly decade bandwidth. In capacitors.
addition, a pair of diplexers are used for the RF power divider The major degradation factors for the mixer using nonideal
and IF balun to separate the LO and RF signals from the switches are the finite ON- and OFF-state resistances and finite
480 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 43, NO. 3, MARCH 1995
(a)
(b)
Fig. 5. (a) Photograph of SB resistive HEMT mixer chip (3.4 mm x 7.7 mm) and (b) photograph of DB resistive HEMT mixer chip (3.4 mm x 7.7 mm).
transition time between the ON and OFF states. Therefore, best
performance of a resistive HEMT mixer is obtained when the 10. 00 50. 00
devices are biased slightly below its pinch-off voltage and iii'
driven with a sufficient LO power to ensure hard and fast ~~'b PLse I - /7
"'- 0 unbalance
gtuamte--oton- saonudrc etu, mga-otef-ft.o -Odtrhaeinr adnedg rdardaaitnio-tno -fsaocutrocres , caspuacchi taasn ctehse, .0((.//..)) . 0.<<..§t.:. uAnmbpalliatundcee ---L..-f-'<(V\ -1..~.....- I / " <L0<Ut :
the gate, drain and source series resistances, and parasitic 0< § 0. 000 I~f .... ---y "" \ 0. 000 -.J
inductances can be minimized by the matching techniques in jc:c: laU ._J_ ~ ......_ Ji5"'-. ~
most instances. In these two mixer designs, the HEMT devices L(/U) :2::; Inse~rtion loss ~ "-...... ~ l(U/)
used to mix RF and LO signals are biased at -1.3-V gate ~ a.. ~
:::;: a..
voltage while the HEMT devices inf the active LO balun are <t:
biased at -0.8-V gate voltage. -10. 00 dl -50. 00
The mixer circuits were fabricated using a specially devel 0. 000 10. 00 20. 00
oped HEMT process (13] on an MEE-grown wafer with an . FREQUENCY (GHz)
Fig. 6. Measured active LO balun performance (spiral inductors are con
AIGaAs/InGaAs heterostructure. Fig. 5 shows the photographs
structed with landed metal lines).
of the completed DB and SB monolithic mixer chips. Both
mixer chips measure 3.4 x 7.7 mm2.
ports up to 20 GHz. The difference in performance above 15.5
GHz is believed to be caused by the self resonance of the 6-
IV. RF PERFORMANCE 1/2-tums spiral inductor, which was not taken into account in
Three baluns, one power divider, one diplexer, and the the simulation. The measured insertion loss including the 3-dB
monolithic DB and SB mixers were tested on-wafer with power splitting loss is between 1.5 and 3 dB from 1.5-15.5
cascade RF probes. Fig. 6 shows the measured performance GHz. Fig. 7 shows the simulated performance of the RF power
of an active LO balun. Over the 1.5-15.5 GHz frequency divider. The insertion loss including the 3-dB power splitting
band, the amplitude and phase unbalances between the two loss is between 3.5 and 4 dB from 1-20 GHz. Over the 2 to
balanced ports are less than 1.5 dB and 10°, respectively. 20 GHz frequency band, the input and output return losses
Although, the simulated performance of the LO balun shows are better than 13 and 20 dB, respectively. Fig. 8 shows the
good amplitude and phase trackings between two balanced measured performance of the RF balun. The insertion loss
CHEN er al.: BROADBAND SINGLE- AND DOUBLE-BALANCED RESISTIVE HEMT MONOLITHIC MIXERS 481
0. 000 5 000 50. 00
iii
co >---: 1s21 ~
l!J
No~~..M..C.. ..!" -20. 00 I • I, -I~/ II'/- ,_ I/ J'~,I, S-lll -" ' \ I I / :(Q<«.<:..:)'::Jji 0. 000 I'--... ~ uAn..m.b. pa-ll-iatun-dc1ee1 uPnhbaaslea nce --
;~M::: ;- I ~ I'-1s221 \ la2!J " il l___ ---
~ f ::::;
Q """ -
-40. 00 :«:;;;:; ~
I 000 10 50 20. 00 Output R.L.
I
FREQUENCY (GHz) -5. 000 -50. 00
0. 700 1. 000 1. 300
Fig. 7. Simulated passive power divider performance.
FREQUENCY (GHz)
Fig. 9. Measured passive IF balun performance.
10. 00 50. 00
iii
inductor in the LO balun which was not taken into account
~
~l!J f hase in the simulation. Fig. 12 shows the comparison between
.00CC<'.-.JJ: J))- (Q<<:«..:.):':::Jji 0. 000 \\ \ h'"---" - uAnmbpalliatundceef- -\) / ru n~ba~la nf..!...cv. e"" 0. 000 l(«<~!J):: ImreFes iafsrsteuivqreeu den macinyxd e ors fia msI uGala Htfeuzdn cactnoiodnn vL eoOrsf i odthnrie v leoR soFsef sf 1roe6q f udteBhnemc yS .wB eAHr eE fiaMxlesTdo
fc:c: la!J I~ ~ -- ~ used. The measured conversion losses are between 8 and 9
li
lC!JJ) ~ H'"\ . - . A lC!JJ) dB for 4-11 GHz RF and 8 and 11 dB for 2-16 GHz RF .
~ Q...J / ~ ""' :f The agreement between the measured and simulated is within
:«:;;;:; 1/1 InIs ertioIn lossI Q 2 dB from 2-16 GHz. Again, the larger deviation between
I 'j
-10. 00 -50. 00 them at higher frequencies is due to the self resonance of
0. 000 10. 00 20. 00
the spiral inductors in the LO balun and diplexer. Fig. 13
FREQUENCY (GHz) compares three different measured conversion losses of the
Fig. 8. Measured passive RF balun performance.
SB mixer to illustrate the effect of the self resonance of
the spiral inductor on the mixer performance. The high end
of the frequency band of the SB mixer is increased from
including the 3-dB power splitting loss is between 4 and 6 dB 13.5-16 GHz by reducing parasitic capacitances associated
from 4-20 GHz. The amplitude and phase unbalances between with spiral inductors. Spiral inductors constructed with metal
two balanced ports are less than 1.5 dB and 8°, respectively, lines deposited directly on the substrate surface (landed metal
over the 4-20 GHz frequency band. The measured IF balun lines) were replaced by metal lines suspended in air, which
performance is in good agreement with the simulated result. were constructed with the airbridge process. For the mixer
Fig. 9 shows the measured amplitude and phase unbalances using spiral inductors with airbridged lines, the conversion
and return losses of the two balanced ports. The amplitude losses of both upper and lower sidebands are shown in
unbalance is less than 0.5 dB while the phase unbalance Fig. 13, while for the mixer using spiral inductors with metal
is less than 3° from 0.75-1.3 GHz. The return loss of the lines deposited on the substrate, only the upper sideband
balanced ports is better than 22 dB for the same frequency conversion loss is shown. In addition, the third-order input
band. The measured and simulated insertion losses and return intercept (IP3) of the DB and SB mixers are determined
losses of the diplexer are shown in Fig. 10 for the purpose from an on-wafer two-tone intermodulation distortion mea
of comparison. The agreement between them is very good surement. A fixed 1-GHz IF and 16-dBm LO power were
for frequency up to 14.5 GHz. The differences above 14.5 used. Figs. 14 and 15 show the measured input IP of the
3
GHz is also caused by the self resonance of the 6-1/2-turns DB mixer and SB mixer, respectively, as a function of the
spiral inductor, which was not taken into account in the RF frequency. The input IP of the DB mixer varies from
3
simulation. 19.5-27.5 dBm for a RF of 7-18 GHz, while the input IP
3
Fig. 11 shows the comparison between measured and sim of the SB mixer is between 20 and 28.5 dBm for a RF of
ulated conversion losses of the DB HEMT resistive mixer 2-16 GHz.
as function of the RF frequency. A fixed IF frequency of Spurious rejections of the DB mixer were measured for a
I GHz and LO drive of 16 dBm were used. The measured RF frequency between 10 and 11 GHz with an LO drive of
conversion losses are between 7.5 and 9 dB for 4-13 GHz 16 dBm and fixed IF frequency of I GHz. Fig. 16 summarizes
RF and 7.5 and l l dB for 3-18 GHz RF. The agreement the measured spurious rejections in a tabular form. Under the
between the measured and simulated performances is within same operating condition, port-to-port isolations of the DB
1 dB from 2-14 GHz. The larger deviation between them at mixer were measured to be better than 30 dB from LO port
higher frequencies is due to the self resonance of the spiral to RF port, better than 38 dB from LO port to IF port, and
482 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 43, NO. 3, MARCH I995
-
0 000 - - .
"" I/
I'-.
~ o Measured o Simulated
~ S2l_dB S2l_dB -10
CC//""JJ x Measured + Simulated II//))
.0.... l f .\ S3l_dB S3l_dB ..0.J -o-- Simulated
z f H
0 -26. 00 f \~ I " I'-. >c: -20 ---+--- Measured
f::: I\ \ " 0 IF=L0-RF=1 GHz
u~.J \ '\ "' )" ~ \ (.) LO Power=16dBm
C/"J II \
2S \ "
fl/ 11-'> , J 0 1 0 20
I'\ /
\ ~ RF freq (GHz)
-50. 00 /
0. 500 9 250 1B . 00 Fig. 11. Measured and simulated performance of DB resistive HEMT mixer
(spiral inductors are constructed with airbridged metal lines).
FREQUENCY (GHz)
(a)
0 000 0
---- I-+--[.....--- r"-. - .C....l. .
,,-" _.+ - 1--ie--- ~ ---" "~IC/) -10
- I/ ~,...... ---'3 \ Ii 0I/ )
[[\\ I I/~ ..J -0-- Simulated
'~; ' r/' + Measured o Simulated I :c>: -20 ---+--- Measured
I \ // SI !_dB SI !_dB 0 IF=L0-RF=1 GHz
\fl (.)
LO Power=16d8m
-30
0 1 0 20
I
v RF freq (GHz)
-25. 00
0 500 9 250 FREQ-GHZ 18 00 Fig. 12. Measured and simulated performance of SB resistive HEMT mixer
(spiral inductors are constructed with airbridged metal lines).
FREQUENCY (GHz)
(b)
0. 000 ""'
0
----.~..... ~ 17 "cCo Airbridged IND
~
-" ---'--"" -- _L.-L..- I/)
_1,,- _e-H- I\ 0I/ ) -10
I/ L--1--,_..,~ \ ...J
l\ IJ' I/ II/ c:
0
-11 00 I \\ [717 o Measured o Simulated .I../.). -20
S22_dB S22_dB
I \I/ Q)
x Measured + Simulated >c:
S33_dB S33_dB 0 RF-L0=1 GHz
(.)
I I I I I -30
0 1 0 20
RF freq (GHz)
-25. 00
0. 500 9 250 FREQ-GHZ 1B . 00 Fig. 13. Measured upper sideband conversion loss of SB mixer using spiral
FREQUENCY (GHz) inductors with landed lines and measured upper and lower sideband conversion
loss of SB mixer using spiral inductors with airbridged lines.
(c)
Fig. 10. Measured and simulated diplexer performance: (a) insertion loss,
(b) input return loss, and (c) output return losses.
the conversion losses are less than O. l dB over the measured
15°C to 60°C temperature range for all mixers except the fifth
one. These variations are within the measurement accuracy and
about 34 dB from RF port to IF p011. Finally, temperature
consistent with what one can expect based on the theoretical
variations of the conversion loss and 2 x 3 as well as 3 x
prediction. The conversion loss of a resistive HEMT mixer is
2 spurious rejections of the DB mixers were also measured.
The measured results are shown in Fig. 17 for the conversion mainly determined by the LO power and the "on" state channel
loss and Fig. 18 for the spurious rejections. The variations of resistance of the HEMT devices at the maximum available LO
CHEN er al.: BROADBAND SINGLE- AND DOUBLE-BALANCED RESISTIVE HEMT MONOLITHIC MIXERS 483
40
Spur Rject ion
LO > RF LO < RF
E 30
CD RF x LO Rejection,dBc RF x LO Rejection,dBc
"~O 2 x I n I x 2 20
aM. 20 2 x 2 l6 2 x 1 51
..... IF=L0-RF=1 GHz 3 x I 61 2 x 2 60
:a:I. 10 LO Power=16d Bm 3 x 2 68 2 x 3 63
c
3 x 3 59 2 x l 65
0 l x 2 80 3 x 2 >70
6 8 1 0 1 2 14 1 6 18 20
5 x 3 97 3 x 3 >70
RF Freq. (GHz)
6 x l 100 3 x l >70
Fig. 14. Measured input lP3 of DB resistive HEMT mixer as a function of
the RF frequency. Fig. 16. Measured spurious rejections of the DB mixer.
MX2SB18X, 177-181, R2C3
11.00
40 I 10.50
10.00
E 30
m 0 9.50
~ ~ 9.00
a(-".) 20 :~i; 8.50
IF=L0-RF=1 GHz
8.00
::I 10 LO Power=16dBm
a. 7 .50
c
0 10 20 30 50 60
0 1 0 20
Temperature, ·c
RF Freq. (GHz)
Fig. 17. Measured conversion loss as a function of the temperature for the
Fig. 15. Measured input IP3 of SB resistive HEMT mixer as a function of DB mixers.
the RF frequency.
demonstrated a conversion loss of 7 .5-9 dB for 4-13 GHz RF
drive. In the saturation region of the conversion loss versus
and a conversion loss of 7.5-11 dB for 3-18 GHz RF. The
LO power curve, the conversion loss is only a weak function
simulated conversion losses of both mixers are very much
of the LO power and the "on" state channel resistance. The
in agreement with the measured results. Furthermore, the DB
fifth mixer shows a 1/4-dB increase in conversion loss with
mixer achieves a third-order input intercept of 19.5-27 .5 dBm
decreased operating temperature and has the lowest conversion
for 7-18 GHz RF and the SB mixer achieves an input IP of
loss among five measured mixers. This may be due to the 3
20-28.5 dBm for 2-16 GHz RF. Finally, the major bandwidth .
insertion gain of the active LO balun is higher so that the
limiting factor, the self resonance of the 6-1/2-turns spiral
mixer is driven into deep saturation region. As a result, a
inductor, of the original designs have been eliminated by using
further LO power increase due to lower operating temperature
inductors constructed with air-bridged metal lines instead of
may degrade the mixer performance.
metal lines deposited directly on the substrate. According to
the measured data, the high end of the frequency band has
been increased by about 12% for the DB mixer and 18% for
V. CONCLUSION
the SB mixer, respectively.
A multioctave SB-resistive HEMT monolithic mixer oper
ating over a 2-16 GHz range and a multioctave DB-resistive
HEMT monolithic mixer operating over a 3-18 GHz range
have been successfully designed, fabricated, and tested. The
ACKNOWLEDGMENT
SB mixer comprises a pair of AlGaAs/InGaAs HEMT's, an
active LO balun, a passive RF power divider and a passive IF The authors would like to thank Dr. D. Streit for the material
balun. The DB mixer consists of an AlGaAs/InGaAs HEMT growth, Dr. P. H. Liu, A. K. Oki, Dr. T. S. Lin, and E. Nattews
quad, an active LO balun, and two passive baluns for RF for their help in the circuit fabrication, J. Coakley for his layout
and IF. The SB mixer chip has demonstrated a conversion support and J. Roth, A. Lawerence IV, Prof. S. Mass, M. Tan,
loss of 8-10 dB for 4-l 5 GHz RF and a conversion loss of Dr. L. Wiedersphan, D. Yang, and S. Chen for their helpful
8-11 dB for 2-16 GHz RF. As to the DB mixer chip, it has discussions.
484 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 43, NO. 3, MARCH 1995
80. 00
70. 00
60 .00
U>
":O; 50 .00
0..
g> 40. 00
30. 00
20. 00
10. 00
0. 00
20 30 40 50 60
Temperature, ·c
Fig. 18. Measured 2 x 3 and 3 x 2 spurious rejections versus temperature for the DB mixers.
T. H. Chen (M'93), photograph and biography not available at the time of
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