This project involves the design of proposed divider to operate at dual band frequencies and the performance is analyzed. The paper "Modified Gysel Power Divider for Dual-Band Applications" was published in January 2011 by authors Zhengyu Sun, Lijun Zhang, Yuzhe Liu, Xiaodong Tong in IEEE Microwave and Wireless Components Letters.

1. RF AND MICROWAVE
CIRCUITS
-Fall 2018
Final Design project
Vignesh Ganesan
VXG170004

2. EERF 6311 – Final Design Project, Vignesh Ganesan
Modified Gysel Power Divider for Dual-Band Applications
Authors: Zhengyu Sun, Lijun Zhang, Yuzhe Liu, Xiaodong Tong
Review paper summary: The objective of the paper “Modified Gysel
Power Divider for Dual-Band Applications” is to design an improved
version of Wilkinson power divider that has open and short stubs attached
to the conventional Gysel structure to achieve high power handling
capabilities. The power divider has good matching, isolation and power
transmission can be achieved at two operating frequency bands. The
proposed structure operates at dual frequencies of 1 and 2 GHz. It uses
microstrip lines and Taconic TLX-8 dielectric substrate with relative
permittivity of 2.55 and thickness of 0.787mm. The reflection and
transmission coefficients of the network are expressed using the S-
parameters of the even-odd mode equivalent half circuits. The measured
results are collected from Angilent N5230A network analyzer. This paper
was published in January 2011 by authors Zhengyu Sun, Lijun Zhang,
Yuzhe Liu, Xiaodong Tong in IEEE Microwave and Wireless Components
Letters. The similar component that they were trying to improve is
Wilkinson power divider which is found in David M Pozar’s version.
Design Details: The proposed power divider model was simulated using
different methods using AWR Microwave Office at mentioned frequency
levels.
a) Design 1 involves the simulation of the proposed model using Wilkinson
Power divider using TLIN to verify the dual band operation of the model.
b) Design 2 involves the simulation of the exact model using given MLIN
at the given center frequency f0. Since thickness of the conductor was not
given, we assumed thickness of the conductor(copper) as 17 micrometers.
The impedance of the lines is given. Also, the impedance of Open and
Short stubs is mentioned. Substituting these values and designing the
proposed model.
c) Design 3 is like Design 2, where the center frequency f0 is assumed to
be 3f0 and then the design was simulated.
Simulation: The above-mentioned designs were simulated in the AWR
MWO software and the results were studied. Design 1 shown in Fig 1., was
simulated using TLIN in two Wilkinson power dividers since it involves two
frequency bands (dual bands). One power divider was made to operate at
1Ghz frequency and the other was made to operate at 2Ghz frequency.
The simulation results for both the bands were obtained as shown in Fig
2., Design 2 was simulated using MLIN as proposed in the model is shown
in Fig 3., The center frequency used here is f0=1.5Ghz. The simulated
results were obtained as shown in Fig 4., Design 3 was simulated using
MLIN like Design 2, but the center frequency was changed as 3f0 instead
of f0 as shown in Fig 5., The simulated results of Design 3 was obtained
as shown in Fig 6., Design 2 and Design 3 has a 20-degree feed (MLIN) at
the location of each port. The dielectric substrate used here was silicon
since the Taconic TLX-8 dielectric substrate was not available in the
software. The relative permittivity was kept at 2.55 and thickness at
0.787mm as mentioned in the paper. Table 1 shows the electrical and
physical dimensions for the design. These values were obtained in TxLine.
Using these values, the schematics were designed.
Table 1: Impedance, line width, electrical length and physical length
at normal frequency and three times the center frequency
Results and Discussion: The simulation results of Design 1, Design
2, Design 3 are included in page 2. Design1 is the implementation of
the conventional design from Pozar. The design is similar to that of
the proposed model. But it involves two Wilkinson power dividers to
achieve the same. The number of components used were large
compared to the proposed model. The results obtained for Design 1
are shown in Fig2., stating the use of more components than the
actual model. Moreover, in Wilkinson divider, the internal isolation
resistor is at balance condition connected to internal straps, which is
difficult for heat dissipation and imbalance monitoring. For the
proposed structure, resistors R can be connected from the Ports 4
and 5 to the external ground with a direct path for heat sinking.
Resistors can be easily mounted on cooling systems with good
thermal conductivity and thermal performance. Design 3 discusses
about the use of the proposed model at higher frequencies with the
use of minimal components only. Here, the center frequency
becomes 3f0. i.e: 4.5Ghz. Hence the dual band for the model is from
3Ghz to 6Ghz as shown in Fig 6.,
Conclusion: The proposed model eliminates the need for Wilkinson
power divider because Wilkinson power divider is mainly used for
lower power applications. To achieve large power applications
numerous Wilkinson power dividers are needed to design the model.
The proposed Gysel model achieves good matching, isolation and
power transmission for large power applications with the use of
minimal components. This method has proposed many new smaller
circuitry designs for large power applications.
References:
[1] Z. Sun, L. Zhang, Y. Liu, and X. Tong, "Modified Gysel power
divider for dual-band applications," IEEE Microw. Wireless Compon.
Lett., vol. 21, no. 1, pp. 16-18, Jan. 2011.
[2] David M. Pozar, Microwave Engineering, 4th
Ed., Wiley, 2011.
Design
frequency
(GHz)
Impedance
(ohm)
Width
(mm)
Electrical
length
(degrees)
Physical
length
(mm)
f0 = 1.5Ghz Z1=43.2 2.71627 90 34.0385
Z2=30.9 4.30954 90 33.482
Z3=45.4 2.52557 90 34.1268
Zv=108 0.489668 90 35.8222
Zp=68.1 1.30933 90 34.8974
f0 = 4.5Ghz Z1=43.2 2.71642 90 11.317
Z2=30.9 4.31331 90 11.1249
Z3=45.4 2.52549 90 11.3476
Zv=108 0.488761 90 11.935
Zp=68.1 1.30844 90 11.6141

3. Figure 1: Schematic of the proposed model implemented using Wilkinson Power divider Figure 2: Simulated S-parameter performance of the proposed prototype using Wilkinson
power divider for 1 GHz/2 GHz dual-band operation with R=51Ω.
Figure 3: Schematic of the proposed Gysel power divider model at center frequency f0=1.5Ghz Figure 4: Simulated S-parameter performance of the proposed prototype for 1 GHz/2 GHz
dual-band operation with R=51Ω.
Figure 5: Schematic of the proposed Gysel power divider model at center frequency 3f0=
4.5Ghz
Figure 6: Simulated S-parameter performance of the proposed prototype at 3f0=4.5Ghz with
R=51 Ω.