TINIEST 2-WAY SPLITTERS CHANNEL SIGNALS

®
TECHNICAL SECTION
INSERTION LOSS (S-2)
AMPLITUDE UNBALANCE
4.4
0.7
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
avg (dB)
AMPLITUDE UNBALANCE (dB)
Figure 1 The SBTC
power splitter/combiners
make use of a highly
integrated manufacturing
approach to achieve
broad bandwidths in a
tiny package.
INSERTION LOSS(dB)
4.2
4.0
3.8
3.6
3.4
3.2
10
100
FREQUENCY (MHz)
Fig. 3
1000
10000
Figure 3 The "lot" insertion loss performance of one of the SBTC-2-10’s
output ports is shown in terms of statistical parameters.
These tiny power splitters use LTCC technology to deliver
full-sized performance for signal processing applications
where PCB area is at a premium.
P
ower splitters/combiners are the invaluable passive
components that allow transmitters and receivers to add
and subtract signals as necessary. Traditionally, broadband power splitters/combiners operating below 2.5GHz
have been based on ferrite transformers in order to convert
an internal point of low input impedance to the 50 ohm
characteristic impedance of an RF system. Due to the
inclusion of the transformer, broadband splitters have
required relatively large package sizes. But the SBTC
model power splitters from Mini-Circuits provide a
breakthrough by squeezing full-scale, broadband
performance into a compact package measuring only
0.15" (0.38cm) on a side including height.
These SBTC models (Figure 1) are 2-way power splitters
that also serve as power combiners. They compare in
performance to currently available multi-decade-bandwidth
splitters from Mini-Circuits measuring 0.25"x0.31"
(0.64x0.79 cm) and larger. Reductions in size of power
splitters has been possible by using external resistors
and capacitors1, but at a sacrifice in parts count and lost
printed-circuit-board (PCB) space due to the use of the
external components. The SBTC models require no
external components, making use of high-level integration
techniques to pack all necessary components within a
tiny surface mount package. Since the SBTC splitters are
so small, multiple output splitters (such as 4-way and
8-way) can be formed by cascading several units while
saving valuable PCB space.
Basically, a power splitter is formed of an input
impedance-matching section, a divider section, a capacitor,
and a resistor. In a 50 ohm system, the impedance at the
input of the divider is close to 25 ohms. The matching
transformer converts this low input impedance to the
characteristic 50 ohm of most RF systems at the RF
input to provide good impedance match for minimal signal
power loss. Normally, a capacitor (C) is required to match
the reactive part of the impedance. The resistor (R) plays
a critical role in providing isolation between the two RF
output ports. Figure 2 shows the relationship of these
four components.
avg + 4.5 sig
0.5
0.4
0.3
0.2
0.1
0.0
3.0
1
TINIEST 2-WAY SPLITTERS CHANNEL
SIGNALS WITHIN 5 TO 2500MHz
avg - 4.5 sig
0.6
As mentioned before, traditional construction of a splitter
requires a large PCB area. In contrast, size reduction is
achieved in the SBTC units by constructing the base with
Blue CellTM technology, which is based on low temperature
cofired ceramic (LTCC) fabrication techniques. The LTCC
technology is mature; it is also employed in the fabrication
of active multichip modules (MCMs) for applications such
as cellular base stations and Bluetooth transceiver modules.
In the power splitter, the Blue CellTM technology makes it
possible to embed the resistor and the
capacitor within the splitter circuitry,
while a ferrite transformer is used to
perform both the power splitting and
matching functions. Connections
RF Input
between components and to the package
are formed through the company’s
proprietary welding process. Electrical
contacts are brought to the bottom of
the splitter circuit board through
via-hole connections. The result is
power splitter/combiners capable of broad-bandwidth
operation within 5 to 2500MHz with low insertion loss,
high isolation, and very repeatable performance from
unit to unit.
Power splitter performance can be specified in terms
of several key parameters such as insertion loss, isolation,
power handling capability, amplitude imbalance, phase
imbalance, and voltage standing-wave ratio (VSWR). In a
power splitter, the measure of insertion loss is the difference
between the amplitude of the input signal and each output
signal, but also taking into account the theoretical loss
associated with splitting a signal. In a two-way power
splitter, for example, each output signal is ideally 3dB less
in amplitude than the input signal. In a four-way splitter, the
power splitting difference is 6dB.
1
10
100
FREQUENCY (MHz)
1000
10000
Fig. 4
Figure 4 The measured amplitude unbalance is considerably less than the
specified maximum value of 0.6dB from 0.5 to 1000MHz.
So, specifications presented for power splitter insertion
loss generally assume the splitting loss, showing only the
insertion loss above whatever signal losses occur due to
power division.
Isolation in a power splitter is a measure of the signal
cross talk that occurs between ports or channels. It is
defined as the attenuation between a signal at any output
port and the level of the signal at another output port, with
the input port terminated in 50 ohms. Unwanted signal
RF Output 1
MATCHING
TRANSFORMER
DIVIDER
R
C
RF Output 2
Figure 2
The SBTC-2-10 consists of four basic components; an input
impedance matching section, a divider section, a capacitor, and a resistor.
All are integrated within the package.
feedthrough or cross talk can result in undesirable spurious
signal products further along the signal-processing chain
in a system. The highest values of isolation are preferred,
with values of 20dB or better generally acceptable for
most applications.
The power-handling capability of a splitter/combiner
depends upon the use of the component. As a divider,
the component can handle higher input power levels than
as a combiner, where the resulting output power level will
be some combination of the total input-power levels minus
the insertion loss. Since a splitter/combiner must dissipate
continued on 26
® P.O. Box 350166, Brooklyn, New York 11235-0003 (718) 934-4500 Fax (718) 332-4661
For quick access to product information see MINI-CIRCUITS CATALOG & WEB SITE
TM
The Design Engineers Search Engine Provides ACTUAL Data Instantly From MINI-CIRCUITS At: www.minicircuits.com
24
ISO 9001 ISO 14001
CERTIFIED
see us on the web
www.minicircuits.com
25
®
TECHNICAL SECTION
TINIEST 2-WAY SPLITTERS CHANNEL
SIGNALS WITHIN 5 TO 2500MHz continued from 25
at RF level -10 dBm
35
31
ISOLATION (dB)
3.0
2.5
2.0
1.5
27
S-2
4.0
INSERTION LOSS (dB)
avg + 4.5 sig
3.5
4.2
4.0
3.8
3.6
3.4
23
3.8
3.6
3.4
3.2
3.2
S-1
1.0
3.0
19
0.5
avg (dB)
avg - 4.5 sig
S-2
3.0
50
150
250
350
avg + 4.5 sig
450
550
650
750
850
950
1050
0
100
200
300
FREQUENCY (M H z)
400
500
600
700
800
900
1000
FREQUENCY (M H z)
15
0.0
1000
10000
1
10
100
1000
10000
at RF level -10 dBm
Fig. 6
power as heat internally, the input-power specification
for the combiner function is lower compared to the
specification for use as a power splitter.
Component repeatability is of prime concern for system
designers. The compact nature of the SBTC design
results in very repeatable performance. For example,
Figure 3 shows the insertion loss performance of the
SBTC-2-10 through three curves. One curve identifies
the mean performance of multiple units, while the two
other curves show the mean minus 4.5 sigma value
and the mean plus 4.5 sigma value. The insertion loss
above the nominal 3dB splitting loss is rated as typically
0.3dB at lower frequencies and in midband, and
typically 0.5dB at the upper frequencies. The maximum
insertion loss across the operating band is 1.4dB.
The compact design of the SBTC-2-10 results in a
very small standard deviation (typically 0.02dB), indicating
that variations from unit to unit are almost negligible.
The manufacture of the unit provides very consistent
insertion loss between individual ports. Figure 4 shows
the amplitude imbalance-the difference in amplitude
between the splitter’s two output ports. The amplitude
imbalance is rated at a maximum of 0.6dB across the
full operating band. Measurements indicate typical
amplitude imbalance of only 0.1dB, with a standard
deviation of 0.04dB.
The phase imbalance is similarly impressive. Rated at a
maximum of 5 degrees across the full operating band,
and as low as 3 degrees from midband to the lowerfrequency limit, measurements show the phase
imbalance to be considerably less than the specified
level (Figure 5), with variations between units being
extremely small (a standard deviation of typically 0.1
degree). The SBTC-2-10 is rated at isolation of
typically 29dB at the lower frequencies, 25dB at
midband, and typically 21dB at the upper-frequency
limit, with worst-case isolation of 16dB across the
full operating band. Actual measurements show the
isolation between ports to be typically 20dB through
1000MHz (Figure 6). This parameter is normally very
sensitive to assembly parasitics in other designs and
varies from unit to unit. In the SBTC-2-10, the standard
deviation for isolation is typically 0.5dB, which signifies
very low unit-to-unit variation. The input/output matching
of the power splitter is well controlled, with VSWR
performance typically 1.15:1.
The SBTC family contains 7 patent pending 2-way 0°
splitters including two 75 ohm and two impedance
matching models. The SBTC-2-10-5075 impedance
matching splitter is for converting 50 ohm input to 75
ohm output in the 50 to 1000MHz band, and the
SBTC-2-10-7550 is for 75 ohm input to 50 ohm output
within 5 to 1000MHz. Performance curves for these
models are shown in Figure 7. All SBTC splitter/
combiners are capable of handling input power levels
as high as 0.5W (as splitter) with the SBTC-2-25
capable of handling up to 1W.
SBTC power splitter/combiners are available in
tape-and-reel packaging for use on high volume,
automated assembly production lines. They are rated
for operating temperatures ranging from -40°C to
+85°C and are available for immediate shipment.
Detailed electrical performance for each model
plus outline drawings and dimensions are available in
this handbook, on the internet at
http://www.minicircuits.com/psc1.html, or
by contacting Mini-Circuits.
1. Engineering Staff, Mini-Circuits, "Do-It-Yourself
Low-Cost Power Splitter",
Microwave Product Digest, May 2000.
at RF level -10 (dBm)
1.50
Figure 6 Measurements show the isolation between ports
to be typically 20dB through 1000MHz.
Figure 5 The measured phase imbalance
compares well with the specified performance.
SBTC-2-10-7550
VSWR
SBTC-2-10-5075
VSWR
FREQUENCY (MHz)
Fig. 5
1.50
#S-VSWR
1.45
#1-VSWR
#2-VSWR
1.45
1.40
1.40
1.35
1.35
1.30
1.30
VSWR
100
FREQUENCY (MHz)
1.25
1.25
1.20
1.20
1.15
1.15
1.10
1.10
1.05
1.05
1.00
#S-VSWR
150
250
350
450
550
650
750
850
950
1050
0
100
200
300
FREQUENCY (MHz)
#2-VSWR
400
500
600
700
800
900
1000
FREQUENCY (MHz)
SBTC-2-10-7550
ISOLATION
SBTC-2-10-5075
ISOLATION
30
#1-VSWR
1.00
50
at RF level -10 dBm
34
at RF level -10 (dBm)
32
28
30
26
ISOLATION (dB)
10
VSWR
1
ISOLATION (dB)
PHASE UNBALANCE (deg.)
INSERTION LOSS (dB)
avg - 4.5 sig
S-1
4.4
4.0
avg (dB)
at RF level -10 (dBm)
4.2
4.6
ISOLATION (1-2)
PHASE UNBALANCE
SBTC-2-10-7550
INSERTION LOSS
SBTC-2-10-5075
INSERTION LOSS
24
22
28
26
24
20
22
20
18
50
150
250
350
450
550
650
750
850
950
1050
0
100
200
300
400
500
600
700
800
900
1000
FREQUENCY (M H z)
FREQUENCY (M H z)
Figure 7 Performance curves for SBTC impedance matching splitters.
ELECTRICAL SPECIFICATIONS
Model
Freq.
Isol.
(MHz)
Typ. (dB)
SBTC-2-10
SBTC-2-20
SBTC-2-25
SBTC-2-10-75
SBTC-2-15-75
SBTC-2-10-5075
SBTC-2-10-7550
5-1000
200-2000
1000-2500
10-1000
500-1500
50-1000
5-1000
25
20
20
28
28
20
24
Ins. Loss*
Typ. (dB)
Phase
Unbal. (Deg)
(Max)
Ampl.
Unbal. (dB)
(Max)
Price $ea.
Qty. 25
0.5
0.8
1.4
0.7
0.8
1.0
0.6
5
10
14
5
5
5
5
0.5
0.8
1.2
0.7
0.9
0.6
0.6
2.49
3.49
3.49
2.99
2.99
2.99
2.99
* Above 3.0dB
® P.O. Box 350166, Brooklyn, New York 11235-0003 (718) 934-4500 Fax (718) 332-4661
For quick access to product information see MINI-CIRCUITS CATALOG & WEB SITE
TM
The Design Engineers Search Engine Provides ACTUAL Data Instantly From MINI-CIRCUITS At: www.minicircuits.com
26
ISO 9001 ISO 14001
CERTIFIED
see us on the web
www.minicircuits.com
27