Design of Two Two-Way Out-of-Phase Slotline Power Divider in C-Band

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303

Design of Two Two-Way Out-of-Phase Slotline Power Divider in C-Band S.Sindhu mathy1 1

Dr.Mahalingam College of Engineering and technology, Department of ECE sindhumathy91@gmail.com

D.Venkatesh2 2

Dr.Mahalingam College of Engineering and technology, Department of ECE mailz4venki@gmail.com

Abstract— Power divider is one of the major components of radio frequency circuits. In this paper two two-way out-of-phase slotline power dividers designed was presented in a microstrip platform. The power dividing circuit, low profile is designed at compact size structure. To provide better isolation at the two output ports microstripline is bent and a slotline is provided. The design is simulated using ADS, results substantiate low insertion loss, better isolation and amplitude balancing at the output ports.

Index terms—Amplitude balance, ADS, compact, isolation, out-of-phase power divider.

I. INTRODUCTION Power dividers/power combiners are passive devices.

In power dividers the input signal at port-1 splits equally between output ports -2 and 3. It is used in the field of communication. Power dividers and directional couplers are essentially the same class of device. Two port equal power divider will provide half the input power at each of its output ports – a 3 dB divider.

It is also possible to use other forms of transmission line (e.g. coaxial cable) or lumped circuit elements (inductors and capacitors).

Out of different types of power dividers, slotline power dividers provide wide bandwidth, low insertion loss, good amplitude balance at the output ports and reasonable isolation among the output ports (for the power divider with isolation improvement) [12].

This paper is organized as follows. Chapter 2 deals with system model. In chapter 3 design and simulation of fourway out-of-phase slotline power dividers. Results and discussions are dealt in Chapter 4. Conclusions are given in Chapter 5.

II. TWO TWO-WAY OUT-OF-PHASE SLOTLINE POWER DIVIDER Fig. 1. Power dividers Power dividers are widely used in wireless/wired communication systems such as Array Antennas ,mixers, phase shifters, modulators, phased array radar antenna systems, monitoring, feedback, combining feeds to and from antenna, antenna beam forming, providing taps for cable distributed systems such as cable TV, separating transmitted and received signals on telephone lines. The Wilkinson power divider is a class of power divider circuit that can achieve better isolation between the output ports while maintaining a matched condition on all ports. The Wilkinson design can also be used as a power combiner because it is made up of passive components and hence reciprocal.

It uses quarter wavelength transformers, which can be easily fabricated as quarter wave lines on printed circuit boards.

IJTET©2015

A Two two-way out-of-phase slotline power divider consists of a λ/2 slotline. The equivalent circuit four-way outof-phase slotline power divider is shown in Fig. 2.

Fig. 2. Equivalent circuit of the four-way slotline Power divider

123

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303 Where Z0 and ZS are the microstrip line and slotline characteristic impedances, respectively. Where θm = 2πlm/λm, θs = 2πlS/λs and θd = 2πd/λs denote the microstrip line electrical length of the extended portion, the slotline electrical length of the extended portion and the slotline electrical length between two adjacent microstrip lines at the coupling point, respectively. The microstrip-slotline transition can be expressed as an equivalent transformer.

The input microstrip feedline (port-1) is placed at the middle of the power divider, which is an open-circuited microstripfeed line with a length lm ≈ λm/4 where λm is the guided wavelength of the microstrip line at the central frequency from the slot to the open end, while the four output ports with identical sizes are arranged symmetrically on the either sides of the input microstrip-feedline.

The transformer turn ratio ‗n’ represents the coupling magnitude between the microstrip line and slotline. After making a number of approximations in the analysis, a closed form expression for the transformer turn ratio ‗n’ is given as, n = Jo (kesWm/2) Jo (kemWs/2)* [(k2em k2εr/ k2 εr cos k1h−k1 sin k1h) + (k2esk1/ k1cos k1h+k2 sin k1h)]

(1)

Where J0(.) is the zeroth-order Bessel function and K1= mod (ko2 εr k2es k2em)

(2)

Fig. 3. Structure of the Four-Way Slotline Power Divider

K1 = K0 mod (εr

εres

εrem)

(3)

K2=K0 mod (εres

εrem

)

(4)

The half wavelength slotline resonator is etched on the bottom layer of the substrate and crossed with the input and output microstrip feedlines near the centre of the slotline.

It can also be seen that the presented power divider only has five parameters, which will greatly simplify the analysis and optimization of the presented power divider.

Kes=K0 εres

(5)

Kem=k0 εrem

(6)

Where, εrem and εres are the effective dielectric constants of the microstrip line and the slotline, respectively.

The reflection and transmission coefficients of the four-way slotline out-of-phase power divider can be calculated according to its equivalent circuit. Therefore, its frequency response can also be analyzed and optimized. Finally, the optimized dimensions of the four-way slotline out-of-phase power divider can be obtained under the desired frequency response. A two two-way out-of-phase slotline power divider is simulated by using an advanced design system (ADS) simulator.

A. Design of Two Two-Way Power Dividers Fig. 3 shows a two two-way out-of-phase power divider consist of an input/output microstrip feedlines and a half wavelength slotline (λs/2) resonator (namely, d + ls ≈ λs/4), where λs is the guided wavelength of the slotline at the central frequency. Fig. 4 shows the slotline resonator is bent to reduce the size of the presented power divider.

IJTET©2015

Fig. 4. Structure of the Four-Way when Slotline is not bent When the RF signal is excited at the input microstrip feedline, the RF power will transmit to the centre of the slotline through the microstrip–slotline transition and then it is simultaneously divided into two equal RF signals, where each transmits to the slotline–microstrip transition of the output microstrip lines through the slotline.

124

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303 Finally, the RF power at the slotline–microstrip transition is equally divided into the two output ports located at the two ends of the same microstrip line. The electric field and current distributions are drawn in the slotline and microstrip line in Fig. 4, the slotline is not bent in order to reduce the size of the structure respectively, which enables to have a conceptual understanding of the in-phase and out-ofphase coupling behavior. It can be seen from Fig. 4 that ports 1, 2 and 5 are in-phase because their current directions are the same. Similarly, ports -3 and 4 are also in-phase. However, ports -2 and 3 are out-of-phase because of their opposite current directions. Obviously, ports -4 and 5 have a phase difference of 180◦. That is to say, the two output ports located at the two ends of the same microstrip line are out of phase when the RF power is transmitted through the slotlinemicrostrip transition from the slotline to the microstrip line.

Then, the total four-way out-of-phase power divider can be viewed as the combination of a two-way microstrip/slotline inphase power divider and two two-way slotline/microstrip outof-phase power dividers. It can be seen that the four output signals are of equal power levels.

TABLE 1 DESIGN PARAMETER VALUES FOR TWO TWO-WAY OUT-OFPHASE SLOTLINE POWER DIVIDER Dimensions

Values

lm

6.5 mm

ls

9 mm

d

1.36 mm

Wm

0.96 mm

Ws

0.2 mm

The layout is shown in Fig. 5, 6 and 7 the simulation is done using Advanced Design System (ADS) 2011.

Apparently, the two ports located at the same microstrip line are out of phase, while the two ports which are located at the same side of the slotline and also symmetric with respect to the input microstrip feedline are in phase.

B. Design of Two Two-Way Power Dividers with an improved isolation A two two-way out-of-phase power divider suffers from poor isolation performance between the output ports since they are located at the same microstrip line. To improve the isolation performance, at the output ports, the output microstrip line is bent in a ring shape, and a slotline is placed at the two ends of the microstripline and it is etched on the bottom layer of the substrate, as shown in Fig. 7.

Fig. 5. Layout of Four-Way Power Dividers

III. DESIGN AND SIMULATION OF FOUR-WAY OUT-OF-PHASE SLOTLINE POWER DIVIDERS A. Design Specifications for Arlon_CLTE Substrate Frequency range : 4 to 8GHz Substrate Thickness, H : 0.38 mm Thickness of the conductor, T: 30 µm Conductivity, ζ : 5.8*10e7 Siemens Dielectric constant, εr : 2.95 Tangent loss, Tan δ : 0.0012

Fig. 6. Layout of Slotline is not Bend

The dimension of the two two-way out-of-phase slotline power divider are calculated by using the equations (16).The calculated values are given in Table I.

IJTET©2015

125

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303

Fig. 7. Layout of power divider with improved isolation B.

Band of Frequency

Fig. 7. Magnitude Response of Insertion Loss at Output Ports

The frequency band used is 4 GHz to 8 GHz. The application of this frequency band is Satellite, Television, and radio band.

IV.

RESULTS AND DISCUSSIONS

The simulated results for the two two-way out-ofphase slotline power divider with and without isolation improvement are discussed in this section.

Fig. 8. Magnitude Response of Return Loss at Output Ports Fig. 6. Magnitude Response of Return Loss S11

IJTET©2015

126

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303

Fig. 11. Phase Difference at the Output Ports, P4 and P5 Fig. 9. Magnitude Response of Isolation at Output Ports The Fig. 10, 11 is obtained by using the equation of scattering parameters, r=phase(S (2, 1))-phase(S (3, 1)) (7) m=phase(S (4, 1))-phase(S (5, 1))

(8)

Fig. 12. Magnitude response of improved isolation at the Output Ports

Fig. 10. Phase Difference at the Output Ports, P2 and P3

IJTET©2015

127

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY

VOLUME 3 ISSUE 1 –JANUARY 2015 - ISSN: 2349 - 9303 Further, the isolation performance of the power dividers can be improved by employing isolating circuits in the output ports located at the same microstrip line. This will be carried out in future. Also the design can be fabricated and tested using network analyser.

REFERENCES [1]

Song K. and Xue Q.,‖UWB ring-cavity multiple-way parallel power divider,‖ IEEE Transaction Industrial Electronics, vol. 60, no. 10,pp. 4737–4745,Oct. 2013.

[2]

Zhang X.Y. and Hu B.J.,―RF tunable BSF with constant bandwidth based on a doublet configuration,‖ IEEE Transaction Industrial Electronics vol. 59, no. 2, pp. 1257– 1265,2012.

[3]

Abbosh A.M., ―Design of UWB three-way arbitrary power dividers,‖ IEEE Transaction Microwave Theory Technology., vol. 56, no. 1, pp. 194–201,Dec. 2008.

[4]

Eom D.S. and Lee H.Y., ―Multilayer substrate integrated waveguide four-way out-of-phase power divider,‖ IEEE Transaction Microwave Theory Technology, vol. 57, no.

12, pp. 3469–3476,Dec. 2009.

[5]

Song K. and Xue Q., ―Planar probe coaxial-waveguide power combiner/ divider,‖ IEEE Transaction Microwave Theory Technology, vol. 57, no. 11, pp. 2761–2767, Nov. 2009.

[6]

He Z., ―Broadband radial waveguide spatial combiner,‖ IEEE Microwave Wireless Components Letters, vol. 18, no. 2, pp. 73–75,Mar.2005.

[7]

K. Song and Q. Xue, ―Novel ultra-wideband (UWB) multilayer slotline power divider with band pass response,‖ IEEE Microwave Wireless Components Letters, vol. 20, no. 1, pp. 13–15, Jan. 2010.

Fig. 13. Phase Analysis at Input and Output Ports The simulated and measured S parameters are shown in Figs. 6–13. It can be seen that the simulated ones closely cover the entire design frequency range. The measured insertion losses S21, S31, S41, and S51 are within 6.5 ± 0.5 dB in a wide frequency range from 4 to 8 GHz. Obviously, the return loss of the output ports, cannot simultaneously obtain good impedance matching at all ports and good isolation among the output ports since the four-way out-of-phase slotline power divider is a lossless structure [22], [24]. The isolation (S32 and S54) between the output ports located at the same microstrip line is less than 4 dB, while the other isolation (S42, S52, S43, and S53) between the output ports located at the different output microstrip lines is greater than 10 dB from 4 to 9 GHz, as shown in Fig. 9.The better isolation performance is improved at the output ports by bending the slotline in ring shape as shown in Fig.12.

V.

CONCLUSION

In this paper a wideband four-way out-of-phase slotline power dividers have been presented. The simulated results of two two-way out-of-phase slotline power dividers without an isolation resistor show acceptable input impedance matching, low insertion loss, and good amplitude balance. It can be seen that the presented slotline power dividers have the advantages of compact size, wide operating bandwidth, good input/output impedance matching, low insertion loss and good amplitude balance at output ports, which make them very competitive in practical applications. Since the power divider suffers from poor isolation performance between the output ports located at the same microstrip line.

IJTET©2015

128