A Miniature GPS Planar Chip Antenna Integrated with Low Noise Amplifier

Transcription

1 A Miniature GPS Planar Chip Antenna Integrated with Low Noise Amplifier 1 Chao-Wei Wang*, Yen-Ming Chen, Chang-Fa Yang Department of Electrical Engineering, National Taiwan University of Science and Technology 43, Keelung Road, Sec. 4, Taipei, Taiwan, ROC M @mail.ntust.edu.tw*, M @mail.ntust.edu.tw, [email protected] Shun-Tian Lin Department of Mechanical Engineering, National Taiwan University of Science and Technology [email protected] Chang-Lun Liao, Chuan-Ling Hu, Chant Sincere CO., Ltd. (COXOC) M @mail.ntust.edu.tw, [email protected] Introduction A planar chip antenna integrated with a low noise amplifier (LNA) for GPS applications at 1.575GHz is presented in this summary. Software packages, XFDTD [1] and HFSS [2] have been applied to design the chip antenna having dimensions of 10mm(L) 8mm(W) 0.8mm (H), as shown in Fig. 1. An insert molding approach is applied to manufacture the antenna, where meandered metal strips are enclosed with liquid crystal polyester (LCP) to form the chip antenna [3]-[5]. Thus, this chip antenna comprises a radiating structure of multiple meandered conducting strips packed with an LCP dielectric composite material to achieve size, performance characteristics and cost effectiveness superior to conventional GPS ceramic patch antennas. The mm 3 compact surface-mount chip antenna is fully compatible with hand- and reflowattachment processes. Also, no additional impedance-matching circuit is required so that the occupied length of the antenna built in a GPS receiver operating at 1.575GHz is just 10mm. For the GPS LNA, an RF transistor (NEC µpc8211tk) is employed, together with input/output matching circuits using a band-pass topology to achieve low noise figure and impedance matching [6]. This LNA is a high gain cascade amplifier, and a negative feed-back topology is used to increase the stability. A software package, ADS [7] has been applied to design the LNA having dimensions of 25mm(L) 25mm(W) 3mm(H). The GPS chip antenna can be integrated with the LNA to form a remote active GPS antenna with dimensions of 25mm(L) 25mm(W) 5mm(H), or built in the GPS receiver together with the LNA. A 100mmx80mm test board has been employed to 1 This work was supported in parts by Chant Sincere Company, Ltd. (COXOC) and the National Science Council of ROC under Grant NSC E /07/$ IEEE 1241

2 simulate the effects of the GPS receiver for evaluating the performance of the build-in active GPS chip antenna. Results Figure 2 shows the return loss of the GPS planar chip antenna mounted on the 100mm 80mm test board, obtained from both simulations and measurements. The simulations were performed by applying the XFDTD and HFSS software packages. A vector network analyzer (Agilent E8362B PNA) was used to measure the return loss of the chip antenna on the test board. The bandwidth of the chip antenna for -10dB return loss is about 100MHz with a central frequency of 1.575GHz. Figure 3 demonstrates the simulated and measured radiation patterns at 1.575GHz for the GPS planar chip antenna mounted on the 100mm 80mm test board. The XFDTD and HFSS software packages are again employed to obtain the simulations. As for the measurements, a far-field anechoic chamber (NSI 800F-10/WavePro FFC-700S) for GHz antenna tests together with the PNA has been used to perform the antenna pattern measurements in three major cuts, as shown in Fig. 3. Good agreements between simulations and measurements have been obtained. A list of the antenna properties for this design is given in Table I, which shows good performance in bandwidths and antenna patterns for GPS applications, requiring omni-directional receptions. Also, a right-hand circular polarization (RHCP) with an axial ratio of 2.4 in broadside is obtained due to the coupling of the antenna with the ground plane of the test board. Figure 4 shows the measured result of the S-parameters and noise figure for the LNA. The vector network analyzer (Agilent E8362B PNA) and spectrum analyzer (Agilent E4445A PSA) were used to measure the S- parameters and noise figure, respectively. The gain and noise figure of the LNA are about 23.7dB and 1.99dB at 1.575GHz. A list of the LNA properties for this design is given in Table II. Figure 5 compares the GPS planar chip antenna mounted on the test board with a conventional GPS ceramic patch antenna by using the same LNA and GPS receiver. It demonstrates that the number of the positioning satellites received and the ratios of the received signals versus noises (C/N) by applying the proposed active GPS chip antenna are good. (the largest C/N is 51 for this GPS receiver module.) The new active GPS chip antenna is particularly suitable for handheld positioning devices, which prefer a build-in and omni-directional antenna. References [1] XFDTD, User s manual, REMCOM Corp., USA. [2] HFSS, User s manual, Ansoft Corp., USA. 1242

3 [3] C.-L. Hu, M.-C. Pan, S.-T. Lin, C.-F. Yang, K.-C. Cheng, S.-F. Wang, L.-S. Jang, C.-L. Liao, A fabrication method of small chip antennas, Taiwan patent # I241052, Oct. 1, 2005 Dec. 28, [4] Warren L. Stutzman, Gary A. Thiele, Antenna Theory and Design, 2nd Edition, John Wiley & Sons, Inc., [5] T. J. Warnagiris and T. J. Minardo, Performance of meandered line as an electrically small antenna, IEEE Trans. Antennas and Propagation, vol. 46, pp , December [6] George D. Vendelin, Anthony M. Pavio, and Ulrich L. Rohde, Microwave Circuit Design Using Liner and Nonlinear Techniques, 2 nd Edition, Wiley, [7] ADS, User s manual, Agilent Corp., USA. Table I Performance of the GPS chip antenna on a 100mm 80mm test board. Dimension (mm 3 ) Central Frequency (GHz) Bandwidth (MHz) 100 Polarizaion RHCP Axial Ratio 2.4 Gain (dbc) 0.9 Efficience(%) 72 VSWR 2.0 (max) Return Loss (db) -10 (max) Pattern Omni-Directional Impedance (Ω) 50 Operating Temperature ( ) -25 ~ +85 Manufacture LCP Insert Molding Technology Figure 1 Dimensions of the GPS chip antenna. Figure 2 The return loss of the GPS chip antenna mounted on a 100mm 80mm test board. θ=90º ψ=0º ψ=90º Figure 3 Simulations and measurements of the antenna patterns for the GPS chip antenna mounted on a 100mm 80mm test board at 1.575GHz. 1243

4 Table II Performance of the GPS Low Noise Amplifier. Frequency Range (GHz) 1.552~1.591 Power Consumption 30mW(3V,10mA) Input Return Loss(dB) -5.9 Output Return Loss(dB) Isolation(dB) Gain(dB) 23.7 Noise Figure(dB) 1.99 Stability >3 Impedance (Ω) 50 Figure 4 Measurements of the S-parameters and noise figure for the GPS LNA. (a) (b) Figure 5 The number of the positioning satellites received and the ratios of the received signals versus noises (C/N) by using: (a) Conventional GPS ceramic patch antenna, (b) GPS planar chip antenna. 1244

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