Miniature Power Splitter

Miniature Power Splitter
(AN-10-002)
Wei Ping Zheng, Radha Setty
1.0 Introduction:
Power Splitters below 1 GHz are traditionally made using ferrite transformers. These splitters provide
multi-decade bandwidth and are compact. Splitters presently available on the market are 0.25• x
0.31• in size. Further reduction in size has been possible using external resistors and capacitors1.
Mini-Circuits now has developed a wide band miniature splitter in a small package, 0.15•x 0.15• x
0.15•, which does not need any external components. This reduced size is made possible by a
technique that integrates all the elements into the package. The resulting splitters should enable
customers to conserve PCB space on the mother board and allow them to build multiple output-port
splitters such as 4-way, 8-way by cascading the splitters. These splitters are available in tape and reel
for high speed automated pick and place manufacturing.
2.0 What Constitutes a Power Splitter:
Fig1. Simplified Schematic of a 2-way Power Splitter
M ATCH IN G
T R A N S FO R M E R
D I V ID ER
Figure 1 shows a block diagram of a power splitter. It consists of an input 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 to 50 ohms at the RF input to provide a
good match. 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 out put ports.
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
Page 1 of 8
3.0 Construction:
As seen in Figure 1, the unit consists of four components. Traditional construction of the splitter
requires a large PCB area (of the order of 0.25• x 0.31•). In the new design, the base of the unit is
constructed using Blue Cell TechnologyTM. This technology enables embedding the resistor and
capacitor in its body. A ferrite transformer is used to perform the power splitting and matching
function. All connections are accomplished by the Mini-Circuits proprietary welding process.
Connections are brought to the bottom of the board by reliable via connections. The resulting unit is
very compact and measures 0.15•x0.15•x0.15•. Figure 2 is a photograph of the splitter.
4.0 Electrical Performance & Repeatability:
Repeatability of components is a prime concern for system designers. The compact nature of the
design results in very repeatable performance. Figures 3 and 4 show the S-1 and S-2 insertion loss of
the splitter. Each graph has three curves. The first curve shows the mean, the second mean plus 4.5
sigma, and the third mean minus 4.5 sigma. As can be seen, the design results in a very small
standard deviation (0.02 dB, typical) so that the variation is trivial from unit-to-unit. Figure 5 shows
the amplitude unbalance, which is the difference of output power between ports 1 and 2. Unbalance is
typically 0.1 dB with a standard deviation of 0.04 dB. Figure 6 shows the phase unbalance of the
splitter. Again, the variation is very small (standard deviation is 0.10 typically). Figure 7 shows the
isolation between the two RF output ports. It is typically 20 dB to 1000 MHz. This parameter is
normally very sensitive to assembly parasitics in other designs and varies from unit to unit. In this
design, the standard deviation for isolation is typically 0.5 dB, which signifies very low variation.
Figures 8 to 10 show the VSWR of the unit. Match is excellent, and VSWR is typically 1.15:1. This
unit is specified to operate over 5-1000MHz and is usable over 1 to 1200 MHz. The unit can handle
0.5W as a splitter and 0.125 W as a combiner. Table I lists the specifications of the splitter.
Conclusions:
A low cost, miniature, high performance splitter has been developed to cover the frequency range of
5-1000 MHz. This splitter, besides being small, has performance equal to or better than similar
splitters built in bigger size.
Reference
1. “ Do-it Yourself Low-Cost Power Splitter”, Microwave product Digest, May 2000.
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
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Fig 2. Photograph of the Miniature Power Splitter
Table I.
MODEL
NO.
SBTC-2-10
FREQ.
RANGE
(MHz)
5-1000
L = low range [fL to 10 fL]
Electrical Specifications
L
Typ. Min.
29
20
M
Typ. Min.
25
18
PHASE
UNBALANCE
(Deg.)
INSERTION LOSS (dB)
ABOVE 3.0 dB
ISOLATION
(dB)
U
Typ. Min.
L
Typ. Min.
M
Typ. Min.
U
Typ. Min.
21
0.3 0.7
0.3 0.8
0.5
M = mid range [10 fL to fU/2]
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
16
1.4
AMPLITUDE
UNBALANCE
(dB)
L
Max
M
Max
U
Max
L
Max
M
Max
U
Max
3
3
5
0.6
0.5
0.5
U = upper range [fU/2 to fU]
Page 3 of 8
INSERTION LOSS (S-1)
4.2
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
INSERTION LOSS (dB)
4.0
3.8
3.6
3.4
3.2
3.0
1
10
100
1000
10000
FREQUENCY (MHz)
Fig. 3
INSERTION LOSS (S-2)
4.4
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
INSERTION LOSS(dB)
4.2
4.0
3.8
3.6
3.4
3.2
3.0
1
10
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
100
FREQUENCY (MHz)
Fig. 4
1000
10000
Page 4 of 8
AMPLITUDE UNBALANCE
0.7
AMPLITUDE UNBALANCE (dB)
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
0.6
0.5
0.4
0.3
0.2
0.1
0.0
1
10
100
FREQUENCY (MHz)
Fig. 5
1000
10000
PHASE UNBALANCE
4.0
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
PHASE UNBALANCE (deg.)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1
10
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
100
FREQUENCY (MHz)
Fig. 6
1000
10000
Page 5 of 8
ISOLATION (1-2)
35
27
23
19
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
15
1
10
100
1000
10000
FREQUENCY (MHz)
Fig. 7
VSWR (PORT-S)
1.25
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
1.20
VSWR
ISOLATION (dB)
31
1.15
1.10
1.05
1.00
1
10
100
1000
10000
FREQUENCY (MHz)
Fig. 8
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
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Page 6 of 8
VSWR (PORT-1)
1.60
avg (dB)
avg - 4.5 sig
avg + 4.5 sig
1.50
VSWR
1.40
1.30
1.20
1.10
1.00
1
10
100
1000
10000
FREQUENCY (MHz)
Fig. 9
VSWR (PORT-2)
1.50
avg (dB)
avg -4.5 sig
avg + 4.5 sig
VSWR
1.40
1.30
1.20
1.10
1.00
1
10
100
1000
10000
FREQUENCY (MHz)
Fig. 10
AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
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AN-10-002 Rev.: A (04/14/15) M150261 File: AN10002.doc
This document and its contents are the property of Mini-Circuits.
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