Updated December 22,
here to go to our main page on resistive splitters
here to go to our page on L-pads
here to go to our main page on unequal splitters
here to check out Adams' unequal resistive splitter, it offers
less loss that the Owen splitter but lower isolation between arms
(and it doesn't offer 3-way or higher splits)
Update December 2011: Kevin helped us out with some equations for the equal-split case. Bravo!
This idea for this content was
contributed by Chris Owen, who designed this cool splitter. No where
else in the universe but Microwaves101 will learn about this, thanks
to Chris who chose to "publish" it here!
Update October 2010: Looks
like MiniCircuits now markets an Owen splitter. Someone there must
have read about it on this Microwaves101 web page! Look for part
number ZFRSC-123 on this
Here's an example
of an Owen splitter.
The Owen splitter provides multiport
capability (2-way to N-way), with unequal splits possible to any
of the ports. Like all resistive splitters it offers wideband performance.
What sets this splitter apart from others (wye, delta, and the
Adams splitter) is that the Owen splitter achieves maximum output
to output isolation because none of the resistors are in the common
path. In this respect there is no better resistive splitter!
Why would you want to consider
this power splitter? Everything in engineering is a tradeoff. Here's
the pros and cons:
- Like all resistive splitters,
the only limitation on bandwidth is due to parasitic elements,
there is nothing intrinsic to the design that would limit bandwidth.
- It is simple to expand the
design from 2-way to 3-way to 4-way to N-way. But with increasing
N, the efficiency is reduced.
- Like all resistive splitters,
you will incur "real" loss when you use it. It is actually
lossier than classic wye and delta resistive splitters described
- It provides better isolation
between split ports than classic wye and delta splitters.
- It provides a means to vary
the voltages of the signals of split ports, so it can be used
as an unequal splitter.
We envision this design as a
wideband equal splitter on a thin-film or thick-film chip, with
2-way, 3-way and 4-way versions. Anyone interested, give us a shout!
Here's the description Chris
sent us in January 1007:
In a semiserious fashion
I wish to lay claim to the Owen Resistive Splitter (similar to
the Wilkinson splitter!) if it hasn't already been claimed, I
have never seen it elsewhere.
This particular resistive splitter design provides 10 dB power
loss from the input to both outputs, maintains 50 ohms match on
all ports, AND provides 19 dB of isolation between each of the
This splitter design may be useful for wideband applications (dc
to 18 GHz!) where attenuation is not an issue and where a little
isolation is useful and where simplicity and low cost and low
space are also important.
Chris's splitter is based on L-pad attenuators.
two-way Owen splitter
Below is a schematic
for a 2-way Owen splitter with the ports defined. Port 1 is the
common port, as a divider this is where the incident signal enters.
We'll use this resistor nomenclature (R1, R2, R3 and R4) in the
Let's review what
is meant by coupling factor and isolation. We (Microwaves101) define
coupling factor as the ratio of the output voltage at a coupled
port to the voltage incident on the common port, which we will call
Most often the coupling factor
is expressed in dB, which is 20xlog(CF).
The power factor is the square
of the coupling factor:
PF in dB is 10xlog(PF),
at which point the coupling factor and power factor are identical.
Isolation is the
ratio of voltage incident to a coupled port to another coupled port.
For a two-way splitter the isolation from port 2 to port 3 is:
The isolation from
port 2 to port 3 is merely the sum of the coupling factors of these
two ports (you can prove that for a homework!) This is why the Owen
splitter offers the maximum isolation of any resistive splitter.
The efficiency factor
is a measure of the efficiency of the device. It is the power output
at all of the coupled ports divided by the power input at the common
port. Expressed in terms of the coupling factors the efficiency
Now it's time to
solve some equation equations for resistor values. The two-way,
unequal Owen splitter resistor values can be solved by choosing
one resistor and solving for the rest, noting that all ports need
to be matched to 50 ohms. We'll skip the painful algebraic steps
that get you to the solution, for this you'll need a large pad of
paper, two cups of coffee and a #2 Pokemon pencil if you're anything
like the rest of us... R2 can be expressed in terms of
the coupling factor of its arm:
We solved the equations
for R1, R2, R3 in terms of R2:
And last, we present
equations for the two coupling factors in terms of resistors that
make up their arms:
All of this stuff is great material
for a spreadsheet, we've been there and done that. If anyone is
interested, ask us nicely and we'll share it with you. Here's a
plot of the four resistor values for unequal splits and Z0=50
ohms, versus the ratio of the two coupling factors (in dB):
Below is a table
of coupling factors, isolation and resistor values for 2-way Owen
splitter (Z0=50 ohms). Looks like you can never get less
than 19 dB isolation with the Owen splitter! You can't say the same
thing about the Wilkinson splitter. The efficiency ()
is theoretically equal to 100% when all of the power is coupled
to one of the arms (which would not be a useful coupler.) Efficiency
bottoms out at about 22% for intermediate coupling values.
2007: previously the data in R1 and R2 columns was inadvertently
reversed, it's fixed now. Thanks to Robert!
Two-way Owen splitter layout
Here's an excellent layout for
a "wideband" two-way Owen splitter, this image was contributed
by Chris Owen himself. Note that the four resistors are all located
as close to each other as possible, and as close to the common node
as possible. Any significant track length between the resistors
acts as distributed transmission line which will cause a phase shift;
at higher frequencies the increasing phase shift will eventually
skew the response (coupling factors will shift and port VSWRs will increase). At some frequency any transmission line will become 1/4 wave and then all bets are off!
The grey/black circles represent
vias that tie the backside ground to the topside grounds.
N-way, equal coupling factor
Here the arms would all have
the same resistor values, R1 and R2. After
some math, the formulas for R1 and R2 (R1 is series resistor, R2 is shunt resistor) such that all
ports are matched to Z0 are:
(solve this resistor first!)
New for December 2011: Kevin solved the equal-split case for coupling factor and output-to-output isolation:
Coupling factor (dB)=
Output-output isolation (dB)=
Here's the values for R1 and R2 for N-way splitters in 50 ohm system. We also
show the "coupling factor", which is the ratio of arm
output to splitter input power (we'll post that equation later).
For N=2, R1=66.7,
R2=100, CF=-9.54 dB
For N=3, R1=120,
R2=75, CF=-13.98 dB
For N=4, R1=171.4,
R2=66.6, CF=-16.08 dB
For N=5, R1=222.2,
R2=62.5, CF=-19.08 dB
For N=6, R1=272.7,
R2=60, CF=-20.82 dB
Yes, it is possible to create
an N-way Owen
splitter with output arms set to different coupling values. Rather
than trying to solve for the resistor values algebraically, we recommend
you use an optimizer to do this job