Compact-Size and High-Q Meanderline Resonator for ITS Application

Compact-Size and High-Q Meanderline Resonator for ITS Application

1Kwang-Chul Son, 2Bhanu Shrestha

1Graduate School of Information and Contents,

2Dept. of Electronic Engineering, Kwangwoon Univ.

20 Kwangwoon-Ro, Nowon-Gu,

Seoul, 139-701 Korea

1Soon Chul Kwon, 3Ki-Cheol Yoon

3RFIC Research Center, Kwangwoon University 20 Kwangwoon-Ro, Nowon-Gu,

Seoul, 139-701 Korea line,

AbstractA compact and high quality factor (QL) meanderline resonator for intelligent transport system (ITS) application on low dielectric substrate is presented. In order to get high QL and frequency responses, the resonator is connected directly to feeding line which is designed to operate at 5.8 GHz. The simulation result of the designed bandstop type resonator shows the QL value of 201. The dimension of the resonator is 1.85 x 1.59 mm2.

Keywords Resonator, compact size; high quality factor; meander-F type;

1. INTRODUCTION

   By the rapid growth of communication systems, intelligent transport system (ITS) service and local area network (LAN) are highly demanded in the recent years. High loaded quality factor (QL) plays a significant role in an ITS mobile communication system, there have been increasing researches on it with sharp-skirt, high selectivity characteristics, and small size for the resonator. For position detection in vehicle mobile communication, high-QL resonator is very important that decides the entire performance of the related devices. Since, the promising elements, the cavity and dielectric resonator have high-QL characteristic, the sizes of those resonators are very big [1]. Therefore, we can reduce the size of the resonator by using high dielectric (r) substrate, but the cost is high [2].

   In addition, a resonator is a system that displays necessary resonance frequency and it occurs in the form of standing waves owing to superposition of the traveling waves. The resonator is used to design high performance filters, oscillators, duplexers, mixers, and so on [3-4]. The characteristics of resonator can mainly determinate the required performance of filters and other resonator based components. There are many classical resonators include half- and one-wavelength uniform, ring, open-loop, and stepped-impedance ones (SIR)[5-6]. The design of the patch resonators requires complicated parameters tuning for achieving desired filtering performance. Most recently proposed stub-loaded resonators originated from the conventional stepped impedance transmission line ones.

   Therefore, we designed the compact-size meanderline resonator with folded structure for ITS application which has

   important in high performance resonators. In the next section, the analysis of the compact resonator, simulation results and conclusion will be discussed.

2. DESIGN ANALYSIS OF RESONATOR

   Basically a hair-pin resonator is composed of g/2 open- circuited line with folded structure. The input port and output port is terminated into 50 [7]. However, in our design, we modified as shown in Figure 1 in which the meaderlines are folded in F-shaped to have very compact size. The spiral is meandered so that we can have high Q-factor. In the Fig. 1, Z0 is the characteristic impedance of the single transmission line with input and output port and Z1 is the characteristic impedance of the folded spiral meandered resonator section [8-9] obtained by the ABCD matrix, which expresses a transmission line and a capacitor [8-11].

   The characteristic impedance of feeding line Z0 is 50 and the characteristic impedance of resonator Z1 is 120 . Also, the w and s are the width of microstrip line in the resonator and a gap between microstrip lines respectively. In the same way, l1 and l2 are lengths of the resonator. Then, the wavelength of a resonator is g/2. In this characteristic, the proposed resonator is coupled to directly connection with feeding line. In this way, the meander-F type is built by folding to make the size small.

   The equivalent circuit is shown in Fig. 2 in which RLC networks are arranged in parallel manner and these are connected to the main transmission line with input and output port. As shown in the Fig. 2, the L is inductance corresponding to the length of the resonator and the C is capacitance corresponding to the gap size in resonator. R is conductance in microstrip line. In the process of designing the compact and high-QL resonator, length, l is optimized to

   1.85 mm and l1 is optimized to 1.59 mm and while width, w is set to 0.2 mm and the spiral structure is meandered so that it can be coupled much more than before, i. e. before meandering. Eventually, this pattern gives high-QL and good resonance performance.

   The loaded quality factor can be found from the equivalent circuit shown in Fig. 2 as follows [6],

   R 2Zo

   bandstop characteristics. Due to close coupling effect, this structure is succeeded to achieve of high-QL which is very

   QL o

   C

   R 2Zo

   (2)

   The loaded quality factor corresponds to the 3 dB bandwidth of S11 given by

   Q o . (3)

   L

   where 0 is the angular center frequency and is a half power bandwidth, i. e. the bandwidth over which the power vibration is greater than half the power at the resonance frequency, =2f .

   mm

   mm

   l1

   1.59

3. SIMULATION RESULTS

   The folded meander line resonator is simulated using IE3D simulator tool and we achieved high-QL of the designed resonator as 201 at the resonance frequency of 5.8 GHz as shown in Fig. 2. In the result, S-parameter responses are shown that includes transmission and reflection coefficients which are very essential in the resonator and these parameters determine the performance of the filter, oscillator, duplexer, etc. when they are implemented. And we can have good input reflection coefficient characteristics too. The entire size of the proposed resonator is 1.85 x 1.59 mm2.

   Input-port

   l

   1. mm Z1

      w

      s

      Z0

      Output-port

4. CONCLUSION

A compact size with high-QL meanderline resonator with folded structure is suggested in this work. The resonator is connected to the main transmission line directly as the feeding line. The size was reduced due to folded structure and designed to the low dielectric material with dielectric constant of 0.54 and a thickness of 2.54 mm. The resonator is designed and simulated at 5.8 GHz for ITS application. The quality factor QL is found to be 201 in the simulation result.

Fig. 1. Layout of the designed resonator

C

Fig. 2. Equivalent circuit of the designed resonator

Input-port output-port

Fig. 3. Simulation result of the proposed resonator

The size of the resonator is 1.85 X 1.59 mm2. The further integration is possible using MMIC technology or IPD technology too due to its compact size.

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