3/5/2018
Coupled line coupler
MICROWAVE COUPLERS
AND POWER DIVIDERS
Hakan P. Partal, Ph.D.
(Pozar)
Planar Microwave Couplers Edge Coupled Line Coupler Design
Coupled Microstrip line Design
Edge Coupled Strip line Design on a substrate with Er=10.
• Hybrid couplers – 3dB equal split, 90deg
• Directional couplers – Sampling power and
usually monitoring the main signal,
-10, -20, -30dB couplers, etc.
– Coupled line couplers –
– Branch line couplers
– Lange couplers
- Microstrip, stripline, multilayer…
- Couplers are designed based on ¼ wavelength (λ/4)
long resonators.
Couplers
Microstrip line calculations
Isolation (dB) =Coupling+Directivity (Pozar)
1
3/5/2018
Couple Line Coupler Design Example
Homework: Design the following coupler in AWR
and simulate S parameters
Design a 15dB Microstrip directional
coupler for 7.5GHz, using a substrate of
Dk=10 and thickness of 0.508mm.
l @ 7.5GHz=4.45mm
We can also use Transmission line calculation tool in Ansoft, AWR, etc.
Couple Line Coupler Design Examle
Isolation (dB) =Coupling+Directivity
Lumped Quadrature (90deg) Coupler Branchline Coupler – Quadrature
– Easy to fabricate
– Easy to integrate to other circuits
– Symmetry (any port as input)
– Can fold for miniaturization
– Narrow band
2
3/5/2018
Recent Studies on
Branchline couplers
Lange Coupler (Quadrature)
• Tighter coupling with wider bandwidth
The finger widths and spacings can be read from the graph plotting
coupled micro-strip line data against even and odd mode line
impedances.
Lange Coupler Design Example
Design a lange coupler for use at 7.5GHz,
3dB split into 50 ohms. Coupler made from
a 0.508mm thick, Dielectric substrate of
Dk=10. Determine S and W of fingers.
3
3/5/2018
Simulation setup Unequal Power Division
for Lange coupler example
Pozar
Simulation results N-way Wilkinson combiners
for Lange coupler example • Radial combiners are called that because they have radial symmetry. Above
N=2, the splitter cannot be laid out in two dimensions.
• For N=3 split, there are two ways to realize the isolation resistors, the "star" and
"delta" configurations.
• A three-way Wilkinson is shown below, with "star-resistor" configuration. The
arms have impedance SQRT(3)xZ0, and the resistors have impedance Z0.
•
N-way divider:
( Not production friendly)
Wilkinson Power Dividers PLANAR 3-way Wilkinson splitters
Equal Split dividers • The splitter type below is imperfect, missing an isolation resistor between
the two outer ports, however, this is what makes it easy to lay out.
• The wilkinson power splitter provides a 3-dB split with no phase shift. In • The three arms each employ a single quarter-wave impedance transformer. If
microstrip form the two arms are usually made from quarter wavelength you were to impedance match port 1 at center frequency, the transformers
lines with an impedance of 70.7 ohms in a 50-ohm system. would all be 86.6 ohms (transforms each 50 ohm leg to 150 ohms, and three
150 ohms in parallel is 50 ohms).
• With optimizations, Z1 can be found to be 91.4 ohms and R1 was 83.6 ohms,
resulting in -15 dB bandwidth of 39%.
The bandwidth of the lumped
Wilkinson is approximately ½ of the
micro-strip version
4
3/5/2018
5 WAY 16-18.5 GHz POWER SPLITTER
A 4-Way Divider Schematic Measured Results
N-way divider-
production friendly
Pozar
3-way Wideband Divider Example Pictures of dividers
5-way Divider Example Pictures of dividers
