An ultra wide band double-balanced mixer with integrated LO buffer amplifier was developed for use between 18-45 GHz. The mixer employs a unique broadside-coupled balun for superior bandwidth over 18-45 GHz. It utilizes GaAs HEMT S-D diode mixing and integrates an LO power amplifier to reduce typical high drive requirements. The LO amplifier and balun allow the mixer to achieve approximately -10 dB conversion gain for up or down mixing across many frequency bands between 18-45 GHz using only 0 dBm of LO power.

1. A 18-45 GHz Double-BalancedMixer with Integrated LO
Amplifier and Unique Suspended Broadside-Coupled Balun
Henrik Morkner, Sushi1 Kumar, Michael Vice
Agilent Technologies Wireless Semiconductor Division, R&D
350 West Trimble Road, San Jose, Califomia, 95131, USA
Abstract - An ultra wide band double-balanced
mixer with integrated LO buffer amplifier has been
developed using 0.1511 depletion mode PHEMT
technology. The mixer employs a unique broadside-
coupled balun for superior 18-45 GHz bandwidth and
overcomes many of the disadvantages of edge coupled
transmission lines in microstrip or stripline. The mixer
utilizes GaAs HEMT S-D diode mixing and integrates
LO power amplifier to ease the drive requirements
typically associated with this type of mixing. The LO
amplifier has a. distributed input stage and sequential
traditional common source FETs for eficient power
amplification. The LO can also be sub-harmonically
pumped for 2x frequency multiplication as well as
fundamentally driven. The result is a mixer capable of
-10 dB conversion gain for up or down mixing across
many commercial frequency bands for 18-45 GHz. LO
power requires only 0 dBm.
I. Introduction
Commercial radios operating in the 20-43 GHz bands (1 8,
23, 26, 24.1, 32, 33, 38, and 42 GHz) for Point-to-Point,
LMDS, and satellite communication applications utilize
mixers for. primary frequency conversion. While narrow
band mixers can be built, the usage of a broadband mixer
simplifies inventory. System design can be further
simplified by integrating a broadband LO amplifier that
can be used for either primary or sub-harmonic LO drive.
This paper describes a single MMIC that provides such a
solution. It was developed to provide a low cost product
for many systems and frequencies.
Figure 1 shows the complete implementation of the
monolithic double-balanced mixer with integrated LO
amplifier. Double-balanced mixing is obtained using a
traditional diode ring quad. LO amplification is done with
a 4 stage single ended amplifier for optimum current
efficiency. To combine the single ended RF and LO
signals, a unique planar balun is employed. All these
elements work together to create a system friendly and
volume manufacture product. This MMlC is available from
Agilent as part number AMMC-3040 [I] and as a
mixeribalun alone version as the AMMC-3041 [2].
Figure 1. 18-45 GHz mixer with LO amplifier. Die size is
2.52 mm X 0.76 mm (Agilent AMMC-3040)
11. Balun Design
A traditional balun over a 20-40 GHz band would utilize
edge coupled balanced transmission lines in microstrip or
stripline to convert a single ended RF signal source into a
ground centered balanced LO source. There are several
uniplanar mixers that contain CPW and slotline transitions,
which serve as a I80 hybrid [3,4]. These are often limited
in operating bandwidth and size due to their quarter-
wavelength CPW lines. These result in physically large and
consequentially lossy baluns. Even when implemented by
adapting a lumped-element CPW-to-slotline transition [5]
to reduce size, the bandwidth is still lacking.
Our unique design does not depend on the edge-coupled
techniques but instead suspends a metal 2 layer over a
contacted metal 1 layer to make a broadside-coupled balun.
A photograph of the suspended system is shown in Figure
2 (Patent pending).
Figure 2. Planar balun metal-over-metal system
0-7803-7833-4/03/$17.0002003 IEEE 267 2003 IEEE GaAs Digest
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2. 111. Fabrication
A two metal layer planar balun as described lends itself to
a semiconductor integrated process. While any process that
utilizes airbridge could be used, a 0 . 1 5 ~ gate
pseudomorphic high electron mobility transistor (PHEMT)
is selected. This is due primarily to the ability to integrate
the LO amplifier rather than diode or balun capabilities.
The foundry used is a modem facility capable of high
volume, high yield, and 6-inch wafer production. With
typical gate sizes of 0 . 1 5 ~and FTof 70 GHz this process is
well capable for this application. Typical process
guaranteed specifications are shown in Table 1 .
Table 1. Typical PHEMT performance
Gain dB 19
11(k
Figure 3. Mixer schematic
Figures 4a & 4b. 18-45 GHz Mixer MMIC. Die size
0.96mm~0.76" (Agilent AMMC-3041)
- I I I I I I I I I I ~O I ! ! > , , , / , / , , ~
18 20 22 24 26 28 30 32 34 36 30 40 42 44
RF Freq. [GHz]
6 7 0 9 10 11 12 13 14 15 16 17 18
LO Input Power Idem]
Figures Sa & 5b. 18-45 GHz Mixer performances
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3. lV.LO Amplifier Design
The LO amplifier is a 4 stage design. The first stage is
semi-distributed to maintain a broadband match while the
2"' through 4" stages are basic common source amplifiers.
Interstage matching and DC bias structures are carefully
designed to maintain gain and power over the 20-40 GHz
band. The LO amplifier is very similar to a stand-alone
product from Agilent as the AMMC-5040 [6]except the
bias is optimized for mixer drive at 3.5V and 250mA. The
schematic for the amplifier is shown in Figure 6. One
unique attribute of this topology is that the combination of
a broad bandwidth 1" stage and harmonic amplification of
the subsequent stages allows sub-harmonic mixing as well
as functional up or down conversion pumping. Table 2 and
Figure 7 detail the performance.
Parameter Unit 1 Min
Band Width GHz I
Gain dB I 2 0
V. Application and Usage
The Mixer with LO amplifier is designed to be used in a
hybrid system with user placed bond wires and substrates.
Die attach can be eutectic or epoxy, but precautions were
made for proper thermal conduction. Since the MMIC
incorporates all tuned elements and presents 50 Ohms to
the outside port, it lends itself very well to automated
assemble and usage. Figure 8 shows a Single drain and single
gate supply assembly for standard LO amplifier and Up/Down
Mixer applications. Figure 9 shows a separate first-stage gate
bias supply for use of a LO as an amplifier or multiplier
application for simple mixing or sub-harmonicpumped mixing.
These are typical configurations for test and usage All
graphed results reported were measured using these
configurations.
Typ I Max
21-43 I
25 I 26
Figure 6.LO amplifier Schematic
Output Retum Loss
-Isolation
Isolation
-8 -14
dB 55
dB 55
Gain Flatness 1 dB I I +/- 1.5 I
OuIputPowerP-l dBm I 19.5 1 21 I 23
Outpt Power Psat 1 dBm I 21 I 22 I 2 4
I Innut Retum Loss 1 dB I -15 1 -17 I I
25
45
n 15 ~,
20 25 30 35 40
Frequency [GHz]
Figure 7. Typical LO Amplifier Gain & Power
To Vw DC Drain
2100 DF
Cb TU~ SupplyTo VccFeedDC Gate
Figure 8. Configuration for standard LO amplifier and
UplDown Mixer applications.
To Voo DC Drain
Figure 9. Configuration of LO for multiplier application for
simple Mixer or sub-harmonicpumped Mixer.
269
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4. V. Complete Mixer w/LO Results
The complete 18-45 GHz mixer with integrated LO
amplifier was fabricated and tested as shown in figure I .
Die size is relatively small at 2.5mm x. 76". and tested
100% on wafer. Typical results based on 6 lots and over
20,000 units measured is shown below in Figure IO.
Typical up conversion loss, down conversion loss, LO
drive power is shown.
Table 3. Mixer w L 0 performance (AMMC-3040)
IF :
Conversion Loss
LO Drive Level
Parameter I Unit I Min I Typ 1 Max
Band Width I GHz I I I
DC DC-3 5
dB IO 12
DBm
RF : 20 20-43 43
LO : I I20 120-43 43 I
With LO amp
Isolation LO=RF
Output Power P-1
-6 0 +4
dB 30
dBm
Down-conversion
LO Return Loss
Without LO am -10
12
F
= 11
8 10
In
2
0
E 9
C 8
m
: 6
._
z 7
- 6 - 5 - 4 - 3 - 2 - 1 0 1 2 3 4 5 6
LO Input Power [dBm]
Figure 10. Up Conversion Loss vs. LO Power
14.0
12.0
go.0
i8.0
6.0
4.0
2.0
0.0
. . . . . .
18 20 22 24 26 28R~fm23GH~f 36 38 40 42 44
Figure 11. Conversion Loss vs. Frequency
VI. Conclusion
An IS-45 GHz double balance mixer with integrated LO
amplifier has been built and demonstrated. The mixer has a
broader bandwidth and lower LO drive requirements that
any other know product on the market. The design utilizes
a unique balun system (2 patents pending) to achieve
smooth performance in a small size. Final results show an
about IO dB conversion loss over the entire bandwidth
with only a 0 dBm LO drive requirement. The final product
bas high yield and viable for commercial applications and
will be release for general sale by Agilent in late 2003.
Acknowledgments
The authors wish to thank Jim Gong, Kai Chia, Hue Tran,
Kohei Fujii, Bob Myers, Monique Bruner, Gary Carr, Irene
Armenta, Frank Ha, Ro Buted for their bard work and WIN
Semiconductor of Taiwan for their professional MMIC
foundry service.
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