Two Kind of Conical Conformal GPS Antenna Arrays on Projectile

Zhang Xiangjun School of Information and Electrical Engineering,

China University of Mining and Technology,

Xuzhou, China, 221116

Email: zhangxj@cumt.edu.cn

Ma Xiaoping, Lai Qifeng School of Information and Electrical Engineering,

China University of Mining and Technology,

Xuzhou, China, 221116

Abstract Two kind of GPS (Global Position System)

omnidirectional antenna array which is conical conformal

with revolving projectile is researched. One is quadrifilar

helix antenna on rotary table and the other microtrip

antenna conformal to the same rotary table. The basic

theory and design method of antenna arrays are described.

The radiation characteristic of the antenna arrays is

presented and they are simulated by the software Ansoft

HFSS. The theory and simulation results are given to

illustrate that the two kind antenna arrays can radiate an

omnidirectional pattern normal to the axis of the cylinder

approximately, and the comparisons between them are

made.

Keywords- GPS omnidirectional antenna array; conical

conformal, quadrifilar helix antenna; microtrip antenna INTRODUCTION

In recent years, people have put forward a higher request to the conformal antennas. For the high-speed whirling carrier as the guided missile, its request for antenna is neither influences the dynamics characteristic of the carrier nor damage the mechanical intensity of the projectile [1].

A circularly polarized (CP) GPS antenna can be obtained using a planar antenna, such as a spiral or amicrostrip patch. When installation space is limited, a rod type CP antenna, such as a helix, is preferable. The paper is focus on the antenna installed on the head of projectile which is conical shape. The antenna on it should be conical conformal. The quadrifilar conical helix antenna and microstrip conical conformal antenna are designed and optimized to satisfy requirements of antenna on revolving projectile. Advances and disadvantages of the two kind of antenna are concluded.

DESIGN OF ANTENNA ARRAYS A Quadrifilar Helix Antenna on Projectile

Quadrifular helix antenna is able to radiate a circularly polarized over a hemispherical region, while the antenna maintaining a broadband input-impedance response [2]. The antenna are installed on the rotary table as shown in Fig. 2, to obtain an axial beam, the four arms are excited with a phase relationship of (0,-90,180,90).

Figure 1. Dimensions of the rotary table

Firstly, the soft subtract material was chosen which dielectric constant is 2.65, the width and length of helix is determinate according to the formula in [3] , then the optimal values of length of helix was obtained by full-wave simulator, Ansoft HFSS. The feed network is shown in Fig. 3, which is composed three one-two power divider, the main object is provided the phase relation. The simulation of the antenna is shown in Fig.4-Fig. 6.

As shown in Fig. 4-Fig. 6, the antenna has wideband characteristics for the input impedance and the radiation pattern. The only disadvantage is that the

___________________________________ 978-1-4244-4076-4/09/$25.00 2009 IEEE

feed network is complicated.

Figure 2. The configuration of the GPS antenna on rotary table

Figure 3. The feed network of the antenna

Figure 4. S-parameter of the antenna

Figure 5. Radiation of the antenna

Figure 6. Axial ration of the antenna

B Conical Conformal Microstrip Antenna Arrays

Array element design Conical conformal microstrip antenna can be

designed to be used in GPS system [4], for limited installation area, the high dielectric constant material is needed to chosen. The dielectric material which dielectric constant is 10.2 is chosen to design the antenna. If the feed line uses microstrip line which characteristic impedance are 50 , the line width of divider only 0.2mm, which is fragile for revolving projectile. The microstip antenna is designed which impedance is 20 . Then the impedance of microstrip line of the divider is 44.7 , the width of the microsrip line is 0.7mm, which is strong enough for the revolving projectile. Using the conventional formula of microstrip antenna design, the dimensions of circular polarization antenna element is obtained, as shown in Fig. 7, a=29.7mm s=2.4mm l1=10.2mm l2=22mm d=2.4mm.

Figure 7. The element of the antenna arrays

Antenna Array

For 4 of central frequency of the antenna is

smaller than the radius of the assemble platform, the performance of conical conformal antenna is similar to

the planner antenna, we can fine tuning the conical conformal antenna by simulating the planner antenna. The configuration of the planner antenna is shown in Fig. 8, for the limited installation area, two elements are used to design the antenna which one power divider. The simulation result of VSWR and axial ration of the planner antenna is shown in Fig. 9, VSAR is less than 2 and axial ration is less than 3dB in the passband. The conical conformal microstrip antenna is shown in Figure 10, which is composed by two elements.

Figure 8. Configuration of planner antenna

(a)

(b)

Figure 9. Simulation results of planner antenna

(a) VSWR, (b) Axial ration

Figure 10. The conical conformal microstrip antenna

(a)

(b)

Figure 11. Simulated radiation patterns of the proposed antenna for

RHCP at 1575 MHz. (a) o0= ; (b) o90= .

Radiation pattern is simulated in the cone structure, as shown in Figure 11. From the simulation results, we can conclude that the antenna satisfies the requirements of the GPS system.

CONCLUSIONS Two kind of conical conformal antennas are

presented in this paper; these antennas are all suitable for GPS application. AS comprised to the conical conformal microstrip antenna, the quadrifilar helix conical conformal Antenna has wideband characteristics for the input impedance and the radiation pattern, but it is a little more fragile and its feed network is more

complicated.

REFERENCES

[1] Zhong Lingling; Qiu Jinghui; Sun Bo, Design of GPS Antenna

Array on Revolving Cylinder, Asia-Pacific Microwave

Conference, 2007. APMC 2007. pp.1-4, Dec., 20007

[2] Sharaiha, A.; Terret, C.; Blot, J.P., Printed quadrifilar resonant

helix antenna with integrated feeding network, Electronics

Letters, vol. 33, no. 4, pp. 256-257, Feb. 1997

[3] Shumaker, P.K.; Ho, C.H.; Smith, K.B., Printed

half-wavelength quadrifilar helix antenna for GPS marine

applications, Electronics Letters, vol. 32, no. 3, pp.153-154,

Feb. 1996

[4] Chen, H.-M.; Wang, Y.-K.; etal. Microstrip-Fed Circularly

Polarized Square-Ring Patch Antenna for GPS Applications,

IEEE Trans Antennas and Propagation, vol. 57, no. 4,

pp.1264-1267, Apr. 2009