Active Passive (electrical)

Track 2: ELECTRONICS & TELECOMMUNICATIONS

HIGHLY MINIATURIZED PASSIVE COMPONENTS EMPLOYING NOVEL π-TYPE MULTIPLE COUPLED MICROSTRIP LINES Young Bae Park, Han Nah Joh*, Se Ho Kim, Young Yun and In Ho Kang Department of Radio and Science Engineering, Korea Maritime University, Busan 606-791, Korea

ABSTRACT

In this work, using a novel π-type multiple coupled microstrip line structure (MCMLS), we fabricated highly miniaturized Wilkinson power divider and branch-line coupler. The line length of the Wilkinson power divider and branch-line coupler was reduced to about λ/44 and λ/38, respectively, and their size were 11.2 % and 14.6 % of conventional ones, respectively. The miniaturized Wilkinson power divider and branch-line coupler showed good RF performances in C band.

is

1. INTRODUCTION

shortened

by

shunt

capacitors,

which

facilitated the fabrication of the miniaturized RF In RFIC device such as PA and Mixer[4],

passive components.

combiner/divider is required for its operation. Wilkinson power divider is one of the passive

2.

components

EMPLOYING Π-TYPE MCML

widely

splitting/combining.

used

for

However,

power

NOVEL

MICROSTRIP

LINE

conventional

Wilkinson power divider employs quarter-

Fig 1-(a) and (b) show a quarter-wavelength

wavelength line, which highly increases the

line and conventional π-type single microstrip

circuit size and manufacturing cost.

line structure (SMLS) equivalent to the quarter-

In this work, in order to realize miniaturized

wavelength line, respectively.

Wilkinson power divider, we propose π-type multiple

coupled

microstrip

line

structure

(MCMLS). In this work, we present the method

λ/4

to reduce the length of quarter-wavelength line,

Z0

and concretely, Wilkinson power divider was highly miniaturized by substituting quarterwavelength line for π-type MCMLS. In the π-

Fig. 1-(a) A quarter-wavelength line

type MCMLS, the characteristic impedance of the line doesn't increase rapidly, though the line International Symposium on Electrical & Electronics Engineering 2007 - Oct 24, 25 2007 - HCM City, Vietnam -135-

Track 2: ELECTRONICS & TELECOMMUNICATIONS

the way, the Eq. (3) indicates that a reduction of shunt capacitor C results in a decrease of the

θ

characteristic impedance Z . Therefore, to solve

Z C

the above problem for the conventional π-type

C

SMLS, a novel structure with reduced shunt capacitor should be employed. For this reason, Fig. 1-(b) Conventional π-type single microstrip line structure

we propose π-type MCMLS in this work, which is shown in Fig. 2.

The following Eqs. (1) - (3) should be

θ1

satisfied in order that the conventional π-type

Coupling

SMLS may be equivalent with the quarter-

capacitance

wavelength line [3].

C1 cos θ Z

ω C1 =

Z =

Z =

(1)

C1

Z0 sin θ

(2)

Z1

Fig. 2 A π-type multiple coupled microstrip line structure The advantage of π-type MCMLS is as

Z0

(3)

2

1 − (ω cZ 0 )

follows. As shown in Fig. 2, for the π-type MCMLS,

coupling

capacitance

C P exists

between lines unlike conventional π-type SMLS, From the Eq. (1), (2), we can see that, as the

and a part of coupling capacitance C P serves as

line length of the π-type SMLS becomes shorter,

the shunt capacitor like C of the π-type SMLS,

C and

characteristic

because it is connected to ground line with via

impedance Z become larger, which makes it

holes. Therefore, a part of coupling capacitance

impossible to fabricate miniaturized passive

C P contributes to a reduction of line length like

components employing the π-type SMLS. For

shunt capacitor C of the π-type SMLS shown

example, if the line length of the π-type SMLS

in Fig. 1 (b), and the total shunt capacitor

becomes less than λ/8, the characteristic

contributing to a reduction of line length for π-

impedance Z becomes higher than 100 Ω.

type MCMLS is a summation of real shunt

However,

whose

capacitor C1 and a part of coupling capacitance

characteristic impedance is higher than 100 Ω

C P . In other words, the total shunt capacitor

can’t be realized on semiconducting or dielectric

contributing to a reduction of line length for π-

substrate due to its very thin line width[2][3]. By

type MCMLS can be expressed as C1 + C P ,

a

shunt

capacitor

the

microstrip

line

International Symposium on Electrical & Electronics Engineering 2007 - Oct 24, 25 2007 - HCM City, Vietnam -136-

Track 2: ELECTRONICS & TELECOMMUNICATIONS

where is an experimentally obtained constant, indicating a portion serving as the shunt

Figure 3 shows a photograph of the highly

capacitor. For this reason, real shunt capacitor

miniaturized

Wilkinson

C1 is reduced in comparison with C of the π-

employing

type SMLS, because C P

serves as shunt

fabricated on Teflon substrate. The line width

capacitor. Therefore, from Eq. (3), we can see

and spacing between .lines are a 0.4 mm,

that, the characteristic impedance Z1 becomes

respectively, and the resistance and shunt

lower than that of π-type SMLS due to its

capacitor are 3.04 Ω and 1.83 pF, respectively.

π-type

power

MCMLS,

divider

which

was

comparatively lower shunt capacitance C1 , which

facilitate

miniaturized

passive

components on semiconducting or dielectric

Table. 1 The size of the novel and conventional Wilkinson power divider are summarized Line Length (mm) 11.3

Size (mm2) 45

substrate. For example, in case that the quarter-

Shunt C (pF)

wave line of Fig. 1-(a) is reduced to λ/44 by

QWL

using the π-type circuit, the characteristic

SMLS

32

8.2

1

impedance Z of the π-type SMLS is increased

MCMLS

17

1

0.5

to 200 Ω, while the characteristic impedance Z1 of the π-type MCMLS becomes 60 Ω, which can

The size of the novel and conventional

be realized on semiconducting or dielectric

Wilkinson power divider are summarized in

substrate. In this work, we developed highly

Table 1.

miniaturized Wilkinson power divider by using

The size of the power divider employing πtype MCMLS are 37 and 53 % of the

the π-type MCMLS.

conventional one employing quarter-wave line 3.

A

HIGHLY

WILKINSON

MINIATURIZED

POWER

DIVIDER

EMPLOYING Π-TYPE MCMLS

and π-type SMLS, respectively. Figure 4 and 5 exhibit power and phase division characteristics for the miniaturized Wilkinson power divider employing π-type MCMLS.

0

power division (dB) -5 -10 -15

S21[dB] S31[dB] S32[dB]

-20 -25 2

3

Isolation (dB)

4

5

6

Freq. [GHz]

Fig. 3 A photograph of the highly miniaturized Wilkinson power divider employing π-type

Fig. 4 Power division and isolation

MCMLS

characteristics for the miniaturized Wilkinson

International Symposium on Electrical & Electronics Engineering 2007 - Oct 24, 25 2007 - HCM City, Vietnam -137-

Track 2: ELECTRONICS & TELECOMMUNICATIONS

power divider employing π-type MCMLS

ACKNOWLEDGEMENT

This work was supported by the Post Brain 100

Korea 21 Project, and IT R&D Project funded by Phase division (deg.)

Korean

50

Ministry

of

Information

and

Communications. 0

REFERENCES

-50

1. D. M. POZAR, Microwave engineering, 2nd -100 2

3

4 Freq. [GHz]

5

ed., Addison-Wesley, 1990, Chapter 8,

6

2.

M.

CHONHCHEAWCHAMNAM,

N.

SIRIPON and I. D. ROBERTSON, Design Fig. 5 Phase division characteristics for in-phase

and performance of improved lumped-

and out-of-phase ports of the miniaturized

distributed

Wilkinson power divider employing π-type

Electron. Lett., Vol. 37, pp. 501-503, 2001

MCMLS

3. T. Hirota, A. Minakawa and M. Muraguchi,

Wilkinson

divider

topology,

Reduced-Size Branch-Line and Rat-Race From 3 to 5.5 GHz, we can observe equal

Hybrids for Uniplanar MMIC's, IEEE MTT

power and phase characteristics. Concretely, we

Trans., Vol. 38, No. 3, pp. 270-275, March,

can observe power division higher than –5.5 dB,

1991

and isolation better than -8 dB.

4. D. R. Webster, G. Ataei and D. G. Haigh, LowDistortion MMIC Power Amplifier Using a

4. CONCLUSION

New Form of Derivative Superposition, IEEE MTT Trans., Vol. 49, No. 2, pp. 328-

In this work, we proposed π-type MCMLS,

332, 2001.

which facilitated the passive components on dielectric substrate. Using the π-type MCMLS, we fabricated highly miniaturized Wilkinson power divider on Teflon substrate, and its size was 37 and 53 % of the conventional one employing quarter-wave line and -type SMLS, respectively. The Wilkinson power divider exhibited good RF performances in the S/C band.

International Symposium on Electrical & Electronics Engineering 2007 - Oct 24, 25 2007 - HCM City, Vietnam -138-