ratio, even as low as 1.1. This makes the phase shifter ideal in

applications involving FET whose capacitance ratio is normally

small. However, such an implementation requires that the maxi-

mum and minimum capacitances of the varactor of each load

are known accurately. Also, because there is no restriction on

the type of the switch in a load, it can be a PIN diode, a FET,

or a MEMS provided that proper integration with the rest of the

phase shifter circuit is observed.

By using a varactor diode and a PIN diode for each load, an

experimental phase shifter operating at 2.5 GHz was developed.

By considering the parasitics of the diodes and peripheral cir-

cuits, the need for inductors in the resonant circuits of the phase

shifter was eliminated. The measurement confirmed the accuracy

of the theoretical design in general. Any disagreements between

the measured and predicted values of the insertion and return

losses at some bias voltages were believed to be due to the finite

resistances of the diodes and lack of accurate manufacturer’s

specification of the diodes at the desired operating frequency. It

was found that the phase shifter has a bandwidth of �7%. The

performance of the new phase shifter can be improved signifi-

cantly using MMIC technology, where losses and parasitics due

to the connections, and varactor devices can be controlled and

reduced drastically, and where the PIN diodes can be replaced

with FET switches easily for higher efficiency.

REFERENCES

1. R.N. Hardin, E.J. Downey, and J. Munushian, Electronically vari-

able phase shifter utilizing variable capacitance diodes, Proc IRE

48 (1960), 944–945.

2. R.M. Searing, Variable capacitance diodes used as phase-shift

devices, Proc IRE 49 (1961), 640–641.

3. R.V. Garver, 360� varactor linear phase modulator, IEEE Trans

Microwave Theory Tech 17 (1969), 137–147.

4. B.T. Henoch and P. Tamm, A 360� reflection-type diode phase

modulator, IEEE Trans Microwave Theory Tech 19 (1971),

103–105.

5. M.A. Armistead, E.G. Spencer, and R.D. Hatcher, Microwave

semi-conductor switch, Proc IRE 44 (1956), 1875.

6. R.V. Garver, Broadband binary 180� diode phase modulators,

IEEE Trans Microwave Theory Tech 13 (1965), 32–38.

7. F. Ellinger, R. Vogt, and W. Bachtold, Compact reflective-type

phase shifter MMIC for C-band using a lumped-element coupler,

IEEE Trans Microwave Theory Tech 49 (2001), 913–917.

8. J.I. Upsur and B.D. Geller, Low loss 360� X-band phase shifter,

IEEE Int Microwave Symp, Dallas, TX (1990), 487–490.

9. F. Ellinger, R. Vogt, and W. Bachtold, Ultracompact reflective-

type phase shifter MMIC at C-band with 360� phase-control range

for smart antenna combining, IEEE J Solid State Circ 37 (2002),

481–486.

10. S. Bulja and D. Mirshekar, A new structure for reflection-type

phase shifter with 360� phase control range, In: Proceedings of

35th European Microwave Conference, on CD, Paris, France,

2005.

11. E.H. Fooks and R.A. Zakarevicius, Microwave engineering using

microstrip circuits, Englewood, NJ, Prentice Hall, 1990.

VC 2010 Wiley Periodicals, Inc.

PHOTONIC GENERATION OFMICROWAVE SIGNALS BY EXPLOITINGFIBER BIREFRINGENCE EFFECT INSINGLE-LONGITUDINAL-MODEDISTRIBUTED BRAGG REFLECTORFIBER LAZER

Hao Zhang,1 Bo Liu,1 Jing Sun,2 Jianhua Luo,3

Shuangxia Wang,3 Chenglai Jia,3 and Xiurong Ma21 Key Laboratory of Opto-Electronic Information and Technology,Ministry of Education, Institute of Modern Optics, NankaiUniversity, Tianjin 300071, China; Corresponding author:haozhang@nankai.edu.cn2 School of Electronics Information Engineering, Tianjin University ofTechnology, Tianjin 300191, China3College of Information Technical Science, Nankai University,Tianjin 300071, China

Received 30 May 2009

ABSTRACT: A novel all-optical microwave generation technique basedon fiber birefringence effect in single-longitudinal-mode (SLM)

distributed Bragg reflector (DBR) fiber lazer is presented. Owing to thebirefringence-induced mode splitting, the proposed lazer could provide amicrowave signal at �1.72 GHz with a 3 dB bandwidth of �30 kHz.

Moreover, another microwave signal at 10.96 GHz could also begenerated as transverse pressure was applied onto the proposed lazer.

Similar phenomenon was observed when another DBR lazer constructedwith Er/Yb co-doped fiber was used, and a microwave signal at 11.47GHz with �33 kHz linewidth have also been achieved. VC 2010 Wiley

Periodicals, Inc. Microwave Opt Technol Lett 52: 535–540, 2010;

Published online in Wiley InterScience (www.interscience.wiley.com).

DOI 10.1002/mop.24961

Key words: photonic generation of microwave signal; single-longitudinal-mode (SLM); distributed Bragg reflector (DBR); fiberlazer; fiber birefringence

1. INTRODUCTION

Because of its low cost, compactness, and immunity to electro-

magnetic interference, photonic generation of microwave signal

has attracted considerable interests and has been extensively stud-

ied in the past few years [1–5]. Generally, photonic generation of

microwave signals could be achieved via external modulation [6]

and optical heterodyning. In the first category, continuous wave is

directly modulated by an intensity or phase modulator. A series of

optical sidebands would be accordingly generated and by appro-

priately selecting two sidebands to be heterodyned at a photode-

tector (PD), the desired microwave signal could be acquired.

Since microwave reference is normally required in the aforemen-

tioned method, optical heterodyning through beating two lazer

beams with desired wavelength separation at a PD is considered

one of the most promising approaches for photonic generation of

microwave signals. In the optical heterodyning scheme, the main

obstacle to generate stable microwave signals with narrow line-

width and low phase noise is to maintain sufficient phase coher-

ence between the two lazer beams. Several techniques to solve the

coherence issue have been investigated, including optical injec-

tion locking [7], phase locking [8], and dual-longitudinal modes

[9] or single-longitudinal-mode (SLM) fiber lazers [10], etc. In

the fiber-lazer–based schemes, as both of the longitudinal modes

oscillate in the same resonator cavity, no additional phase locking

technique is required. In 2005, Shen et al. presented a microwave

generation based on a linear cavity Brillouin finer lazer [11]. By

appropriately designing the lazer parameters, stokes waves with

Brillouin shift relative to the pump light could be generated and

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 535

then be heterodyned at a PD with the pump light to produce the

required microwave signal. In 2008, Geng et al. proposed another

similar microwave generation technique based on a linear cavity

photonic crystal fiber Brillouin lazer [12]. However, higher pump

power is required to excite higher order stokes waves and more-

over, since the Brillouin shift is determined by the material prop-

erty of the fiber lazer, the frequency of generated microwave sig-

nal is relatively fixed. In 2006, Chen et al. reported a microwave

generation technique based on dual-wavelength SLM fiber ring

lazer [13]. However, to ensure SLM operation, equivalent phase

shift (EPS) technique was involved to fabricate the dual-wave-

length ultranarrow transmission-band fiber Bragg grating (FBG).

And to avoid the lazer instability induced by the homogeneous

broadening effect in erbium-doped fiber (EDF), a semiconductor

optical amplifier (SOA) was used in the ring cavity, which inevita-

bly increases the system cost and complexity.

In this article, an all-optical microwave generation technique

exploiting fiber birefringence effect in the SLM DBR fiber lazer

is proposed and experimentally demonstrated. Owing to the

mode splitting induced by intrinsic fiber birefringence, the pro-

posed fiber lazer could provide a microwave signal at �1.72

GHz. The temperature characteristics of this fiber lazer have

been experimentally investigated. Furthermore, by applying

transverse pressure onto the fiber lazer, a microwave signal at

10.96 GHz was obtained due to the pressure-induced fiber bire-

fringence of the FBG. Moreover, another microwave signal at

11.74 GHz was achieved when another SLM DBR lazer with

different active fiber was used under transverse pressure.

2. EXPERIMENTAL SETUP AND OPERATION PRINCIPLE

Figure 1 shows the schematic diagram of the proposed SLM

DBR fiber lazer for microwave generation. This fiber lazer has a

fundamental Fabry-Perot linear cavity configuration, which is

constituted by a segment of active fiber with two FBGs as the

cavity reflectors. To ensure SLM operation, only active fiber is

utilized as the gain medium. To effectively establish lasing os-

cillation in such a short cavity DBR lazer, two FBGs with

reflectivities of more than 99% are directly inscribed in the gain

fiber with 193 nm excimer and phase mask method [14]. The

proposed DBR lazer is sandwiched between two perspex plates

along the central axis with three supporting fibers on either side

to ensure that transverse pressure could be evenly applied. To

avoid the possible influence of residual forward 980 nm pump

light on the beat signal, backward monitoring scheme is

adopted. And to eliminate any possible reflection, an optical iso-

lator is placed at the signal port of a 980 nm/1550 nm wave-

length division multiplexer (WDM). The backward lazer light is

separated by a 3 dB coupler. One portion of the backward lazer

light is converted into the electric signal via a high-speed PD

and then measured by an electric spectrum analyzer (ESA),

while the other portion is transmitted directly to an optical spec-

trum analyzer (OSA) for real-time lazer wavelength monitoring.

The microwave generation principle of the proposed SLM

DBR fiber lazer could be described as follows. According to the

lazer principle, the lazer frequency of a certain longitudinal

mode m is determined by:

m ¼ cq

2nl(1)

where c is the light velocity in vacuum, n is the effective refrac-

tive index of the fiber core, l represents the cavity length, and qrefers to the order number. Because of intrinsic fiber birefrin-

gence, the two orthogonal longitudinal modes would experience

slight mode splitting, and the frequency corresponding to x and

y polarization modes could be described as:

mx ¼ c

2nxl; my ¼ c

2nyl(2)

where nx and ny represent the refractive indices corresponding to

x and y polarization modes, respectively. Therefore, the beat fre-

quency Dmq between the two orthogonal polarization modes

induced by the intrinsic fiber birefringence could be expressed

as:

Dmq ¼ mx � my ¼ ðny � nxÞcq2nxnyl

(3)

Considering |n�nx| � n, |n�ny| � n, the aforementioned

expression could be approximated as:

Dmq ¼ Bmn

(4)

where B is the intrinsic fiber birefringence (B ¼ ny � nx).Therefore, frequency of the microwave signal generated from

mode splitting induced by intrinsic fiber birefringence could be

expressed by formula (4).

Another factor that may contribute to the generation of

microwave signal is the beat signal between different longitudi-

nal modes. As the DBR fiber lazer has a cavity length of �cm,

in most cases, the proposed lazer operates in SLM and the mode

splitting induced by intrinsic fiber birefringence plays a major

role in the generation of microwave signal. However, when

transverse pressure is applied onto the two FBGs, owing to the

pressure-induced birefringence originating from photoelastic

effect, effective refractive index corresponding to different ori-

entations will change accordingly. For convenience, assume y is

the direction along with the transverse pressure is applied, x rep-

resents the direction vertical to y, and z refers to the fiber axis.

The change of refractive index at a certain point P(x,y,z) in the

FBG can be described as [15]:

ðDneffÞx ¼ � 1

2ðneff;0Þ3½p11ex þ p12ðey þ ezÞ� (5)

ðDneffÞy ¼ � 1

2ðneff;0Þ3½p11ey þ p12ðex þ ezÞ� (6)

Figure 1 Schematic diagram of the proposed single-longitudinal-mode

distributed Bragg reflector fiber lazer for microwave generation. LD,

lazer diode; WDM, wavelength division multiplexer; FBG, fiber Bragg

grating; ISO, isolator; OSA, optical spectrum analyzer; PD, photodetec-

tor; ESA, electrical spectrum analyzer

536 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 DOI 10.1002/mop

where (Dneff)x and (Dneff)y represent the change of effective

index for x and y polarization modes, respectively; P11 and P12

are photoelastic coefficients of the fiber; ex, ey, and ez refer to

the strain along x, y, and z axis at point P(x,y,z), respectively.By differentiating the Bragg condition k ¼ 2neffK, we have

Dkk

¼ Dneffneff

þ DKK

(7)

where k is the reflection peak wavelength of the FBG, neff is theeffective refractive index of the fiber core, and K represents the

grating period.

According to Eqs. (5) and (6), and considering ez ¼ DLL ¼ DK

K ,

Eq. (7) could be modified as:

For x polarization;

Dkx ¼ ez � 1

2ðneff;0Þ2½p11ex þ p12ðey þ ezÞ�

� �k

(8)

For y polarization;

Dky ¼ ez � 1

2ðneff;0Þ2½p11ey þ p12ðex þ ezÞ�

� �k

(9)

Hence, the wavelength separation D between the two reflec-

tion peaks can be described as:

D ¼ Dky � Dkx ¼ 1

2ðneff;0Þ2ðp12 � p11Þðey � exÞk (10)

As the pressure applied onto the FBG is large enough, the

reflection spectrum of each FBG will split into two reflection

peaks, and dual-wavelength lasing oscillation will occur in the

proposed short cavity fiber lazer. In this case, the wavelength

separation is large enough so that two different longitudinal

modes may oscillate simultaneously to produce the desired

microwave signal. According to Eq. (10), frequency of the

microwave signal generated from pressure-induced birefringence

Dm could be expressed as:

Dm ¼ D

k2c (11)

In the aforementioned equation, as the wavelength separation

is small enough, the initial reflection peak wavelength k of the

FBG without applied pressure is used to approximate the two

reflection peak wavelengths of the FBG under transverse

pressure.

Therefore, microwave generation based on the proposed

SLM DBR fiber lazer could be achieved through two possible

ways. When no pressure is applied onto the fiber lazer, due to

presence of intrinsic fiber birefringence, microwave signal is

generated from the mode splitting of the same longitudinal

mode. And owing to the pressure-induced birefringence when

the fiber lazer is under transverse pressure, microwave signal

could be also acquired through beating between different longi-

tudinal modes.

3. EXPERIMENTAL RESULTS AND DISCUSSION

We have respectively achieved microwave generation with two

short cavity DBR fiber lazers consisting of different active

fibers. In the No.1 DBR lazer, a segment of erbium-doped fiber

(EDF) is utilized as the gain medium. As the fiber lazer has a

cavity length of �cm, it is necessary to ensure sufficient gain

and low cavity loss for effective lasing output. Two FBGs with

reflectivities of more than 99% and matched reflection peaks are

directly inscribed in the EDF. As shown in Figure 2, when the

pump power increases to 125 mW, a single wavelength lazer

around 1554.088 nm with a 3 dB bandwidth of 0.056 nm is

experimentally obtained, and its side mode suppression ratio

(SMSR) reaches �55 dB. The short cavity length of the pro-

posed DBR lazer is short enough to ensure SLM operation,

however, the presence of intrinsic fiber birefringence contributes

to a slight mode splitting, leading to the generation of micro-

wave signal. From Figure 3, it could be seen that as no trans-

verse pressure is applied, the DBR lazer could provide a micro-

wave signal at 1.7203 GHz. The inlet shows that the generated

microwave signal has a narrow 3 dB bandwidth of less than 30

kHz, and 99% of the signal power is concentrated within an

occupied bandwidth of less than 70 kHz, indicating a good pu-

rity of the microwave signal.

To characterize its temperature feature, the proposed DBR

fiber lazer was placed in a temperature controller. From Figure

4, it is clear that as temperature increases from 30.1�C to

110.3�C, the microwave frequency linearly increases from

1.72028 GHz to 1.75357 GHz, and the coefficient of determina-

tion reaches 0.99956. Therefore, the generated microwave

Figure 2 Lazer spectrum of the No. 1 DBR lazer

Figure 3 Electrical spectrum of the microwave signal observed at the

output of photodiode for No. 1 DBR lazer as no transverse pressure is

applied. The inlet shows 3dB bandwidth spectrum of the generated

microwave signal

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 537

frequency is tunable through temperature control. We have also

investigated the temperature-dependent spectral response of the

No. 1 DBR lazer, as shown in Figure 5. It is obvious that the

lazer peak wavelength increases with the increase of temperature

as well, and the coefficient of determination reaches 0.99958.

As temperature increases, reflection peak of each FBG will

increase accordingly. Owing to the direct inscription of two

FBGs in the gain fiber, the two FBG reflectors have nearly the

same temperature response, which maintains wavelength match-

ing of the two FBGs as temperature changes to promise single

wavelength lasing oscillation. It should be noted that according

to Eq. (4), frequency of the microwave signal generated from

mode splitting is determined by intrinsic fiber birefringence,

lazer operation frequency, and refractive index of the fiber core.

From the aforementioned experimental results, we can see that

the lazer frequency decreases with the increase of temperature.

Besides, several studies indicate that refractive index of silica-

based fiber increases with the increase of temperature [16, 17].

Therefore, the relationship between microwave frequency and

temperature, as shown in Figure 4, should be attributed to the

temperature dependence of intrinsic fiber birefringence. From

Eq. (4), we could calculate the intrinsic fiber birefringence as a

function of temperature. The refractive index of the fiber core

could be calculated according to the definition of numerical

aperture (NA) of the fiber:

NA ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffin21 � n22

q(12)

where n1 and n2 represent the refractive index of the fiber core

and cladding, respectively. According to the Sellmeier equation

[16], we can calculate the refractive index dispersion of silica-

based fiber cladding for a wavelength range of 1554.194 nm to

1555.102 nm at 20�C, corresponding to that in Figure 5. Consid-

ering NA of the EDF used in our experiment is 0.22, the refrac-

tive indices of the EDF core could be obtained for different

wavelengths. Thus, based on the assumption that the refractive

index dispersion of the fiber cladding at 20�C is characterized

by the aforementioned Sellmeier equation with a typical temper-

ature coefficient of 1 � 10�5/�C [17], we could calculate the

temperature dependence of intrinsic fiber birefringence, as

shown in Figure 6. It can be seen that as temperature increases,

intrinsic fiber birefringence increases as well, and the coefficient

of determination reaches 0.99958.

Figure 4 Microwave frequency as a function of temperature for the

No. 1 DBR lazer as no transverse pressure is applied

Figure 5 Lazer peak wavelength as a function of temperature for the

No. 1 DBR lazer as no transverse pressure is applied

Figure 6 Calculated intrinsic fiber birefringence as a function of

temperature

Figure 7 Electrical spectrum of the microwave signal observed at the

output of photodiode for No. 1 DBR lazer as transverse pressure is

applied

538 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 DOI 10.1002/mop

By applying transverse pressure onto the No.1 DBR lazer,

pressure-induced birefringence in the FBG reflectors cause the

original single lazer peak splits into two wavelengths to produce

a microwave signal with higher frequency. As shown in Figure

7, a microwave signal at 10.96 GHz was experimentally

observed and no beat signal between multiple longitudinal

modes exists within a span of 13.96 GHz, which indicates that

the lazer is operating in SLM. Considering the �cm cavity

length of the DBR lazer, the mode spacing between adjacent

longitudinal modes should be �10.27 GHz, which generally

agrees with our experimental result. This proves that the micro-

wave signal is generated from the beating between two adjacent

longitudinal modes when transverse pressure is applied. The

inaccurate value of cavity length adopted in our calculation is

the main factor resulting in the deviation of experimentally

acquired microwave frequency from the calculated value.

To further verify our theoretical analysis of the microwave

generation principle, another DBR lazer with a piece of �cm

highly concentrated Er/Yb co-doped fiber as the gain medium

was used for microwave generation. When pump power

increases to 158.5 mW, from Figure 8, it can be seen that as the

No. 2 DBR lazer is not under transverse pressure, the lazer pos-

sesses a single peak around 1547.358 nm. When transverse pres-

sure is applied by using the sandwiching device, due to the pres-

ence of pressure-induced birefringence, the lazer peak splits into

two peaks with a wavelength separation of 0.096 nm. It should

be noted that owing to the polarization hole burning (PHB)

effect, the mode competition induced by the homogeneous

broadening of the gain fiber could be suppressed to a large

extend [18, 19]. Hence, the proposed lazer is able to promise

stable lazer output with two orthogonal polarization modes,

which is essential to ensure a good quality of the generated

microwave signal. Figure 9 shows the electric spectra observed

at the output of PD. As no transverse pressure is applied, due to

the mode-splitting induced by intrinsic fiber birefringence, the

No.2 DBR lazer could provide a microwave signal at 216.533

MHz. Since the intrinsic fiber birefringence of the No.2 DBR

lazer is a little bit lower than that of the No.1 DBR lazer, it pro-

vides a microwave signal with lower frequency compared with

the No.2 lazer as no transverse pressure is applied. As shown in

Figure 9(b), when the No.2 lazer is under transverse pressure

through the sandwiching device, a microwave signal at 11.47

GHz is acquired, which is generated from the beating between

two adjacent longitudinal modes corresponding the two lazer

wavelengths in Figure 8(b). From the inlet of Figure 9(b), it

could be seen that the generated microwave signal has a 3 dB

bandwidth of less than 33 kHz, and 99% of signal power is con-

centrated within an occupied bandwidth of �84 kHz.

4. CONCLUSION

In summary, an all-optical microwave generation technique by

exploiting the fiber birefringence effect in SLM DBR fiber lazer

is presented and experimentally demonstrated. By directly

Figure 8 Lazer spectra of the No. 2 DBR lazer: (a) no transverse pressure is applied (b) transverse pressure is applied

Figure 9 Electric spectra observed at the output of photodiode for the

No. 2 DBR lazer: (a) no transverse pressure is applied (b) transverse

pressure is applied

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 539

inscribing two FBGs with high reflectivties in a piece of �cm

EDF, the proposed DBR fiber lazer could operate in SLM.

Because of mode-splitting induced by intrinsic fiber birefrin-

gence, this lazer could produce a microwave signal at 1.7203

GHz with a 3 dB bandwidth of less than 30 kHz. Furthermore,

by applying appropriate transverse pressure onto the fiber lazer,

owing to the pressure-induced birefringence, another microwave

signal at 10.96 GHz generated from the beating between two

adjacent longitudinal modes has also been experimentally

acquired. The microwave generation principle has been analyzed

in detail. Similar experimental results of another DBR lazer con-

structed with Er/Yb co-doped fiber as the gain medium validates

our theoretical analysis on the microwave generation principle.

As no transverse pressure is applied, due to the presence of

intrinsic fiber birefringence, the proposed lazer could provide a

microwave signal at 216.533 MHz. And when the DBR lazer is

under transverse pressure, owing to the pressure-induced bire-

fringence, stable two wavelength oscillation occurs, and accord-

ingly another microwave signal at 11.47 GHz with a 3 dB band-

width of less than 33 kHz is achieved. The proposed scheme

has presented a simple but cost-effective solution for optical

generation of high-quality microwave signals. Because of its

simple configuration, low cost, high integration, and SLM opera-

tion, the proposed fiber lazer would have various potential appli-

cations in radio-over-fiber systems, high-resolution spectroscopy,

and fiber-optic sensor networks, etc.

ACKNOWLEDGMENTS

This work was jointly supported by the National Key Natural Sci-

ence Foundation of China under Grant No. 60736039, the Tianjin

Key Project of Applied and Basic Research Programs under Grant

No. 07JCZDJC06000, the Key Project of Ministry of Education

under Grant No. 206006, the ‘‘100 Projects’’ of Creative Research

for the Undergraduates of Nankai University under Grant No.

BX6-215, and the National Undergraduate Innovation Experiment

Project under Grant No. 081005511.

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VC 2010 Wiley Periodicals, Inc.

COMPACT QUINTPLEXER MODULE WITHPASSIVE TRIPLEXER FOR US-CDMAHANDSET APPLICATIONS

Seong J. Cheon and Jae Y. ParkDepartment of Electronic Engineering, Kwangwoon University,447-1, Wolgye-Dong, Nowon-Gu, Seoul 139-701, Korea;Corresponding author: jaepark@kw.ac.kr

Received 30 May 2009

ABSTRACT: In this article, compact quintplexer modules with apassive triplexer circuit were newly designed, implemented, compared

for US-CDMA handset applications. The proposed passive triplexercircuit was comprised of a single diplexer, parallel resonant circuit,

bandpass filter for GPS, and its impedance matching circuit. Althoughthe number of passive components to comprise the proposed triplexerand its size were dramatically reduced, its performance characteristics

were much better than the previously reported modules. Moreover, forrealization of compact quintplexer module with small size and volume,

FBAR filter bare chips and system in package technology were utilizedinstead of an US-PCS packaged duplexer. Its excellent performanceswere good enough to directly apply for currently used handsets.

Simulated and measured performance characteristics of fabricatedtriplexer and quintplexer module were well agreed. The fabricated

quintplexer module had a 7.0 � 5.0 � 1.4 mm3 volume. VC 2010 Wiley

Periodicals, Inc. Microwave Opt Technol Lett 52: 540–543, 2010;

Published online in Wiley InterScience (www.interscience.wiley.com).

DOI 10.1002/mop.24959

540 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 3, March 2010 DOI 10.1002/mop