Microstrip Antennas Part 14 pptx

Microstrip Antenna Arrays 379 Fig. 27 presents S11 results of the folded antenna results for different position relative to the human body. Explanation of Fig. 26 is given in Table 6. From results shown in Fig. 13 we can see that the folded antenna has V.S.W.R better than 2.0:1 for air spacing up to 5mm between the antennas and patient body. If the air spacing between the sensors and the human body is increased from 0mm to 5mm the antenna resonant frequency is shifted by 5%. Plot colureSensor position Red Shirt thickness 0.5mm Blue Shirt thickness 1mm Pink Air spacing 2mm Green Air spacing 4mm Sky Air spacing 1mm Purple Air spacing 5mm Table 6. Explanation of Fig. 26 ColureSensor position Red Shirt thickness 0.5mm Blue Air spacing body to shirt 1mm Pink Belt thickness 4mm Sky Air spacing shirt to belt 1mm Green Air spacing shirt to belt 4mm Table 7. Explanation of Fig. 27 410 420 430 440 450 460 470 480 490400 500 -18 -16 -14 -12 -10 -8 -6 -20 -4 freq, MHz dB(S(1,1)) m1 m2 m3 dB(loop46033b_mom S(1,1)) dB(loop46033c_mom S(1,1)) dB(loop46033d1_mom S(1,1)) dB(loop46033B2_mom S(1,1)) m1 freq= dB(S(1,1))=-10.447 400.0MHz m2 freq= dB(S(1,1))=-14.809 430.0MHz m3 freq= dB(S(1,1))=-9.962 450.0MHz Shirt 0.5mm Air 1m m Air 2mm Air 4mm 1mm air between body and shirt Belt 4mm Fig. 27. S11 results for different belt thickness S11results in Fig. 27 presents the folded antenna matching when the belt thickness has been changed from 2 to 4mm. Explanation of Fig. 27 is given in Table 7. S11results are better than -10dB for belt thickness ranging from to 2 to 4mm. Computed S11 and S22 results was better Microstrip Antennas 380 than-10dB for different body tissues with dielectric constant ranging from 40 to 50. Computed S11 and S22 results were better than -10dB for different shirts and belts with dielectric constant ranging from 2 to 4. 4.4 Medical applications An application of the proposed antenna is shown in Fig. 28. Three to four folded dipole antennas may be assembled in a belt and attached to the patient stomach. The cable from each antenna is connected to a recorder. The received signal is routed to a switching matrix. The signal with the highest level is selected during the medical test. The antennas receive a signal that is transmitted from various positions in the human body. Folded antenna may be also attached on the patient back in order to improve the level of the received signal from different locations in the human body. Fig. 29 and Fig. 30 show various antenna locations on the back and front of the human body for different medical applications. In several applications the distance separating the transmitting and receiving antennas is less than 2D²/λ, where D is the largest dimension of the source of the radiation. In these applications the amplitude of the electromagnetic field close to the antenna may be quite powerful, but because of rapid fall-off with distance, they do not radiate energy to infinite distances, but instead their energies remain trapped in the region near the antenna, not drawing power from the transmitter unless they excite a receiver in the area close to the antenna. Thus, the near-fields only transfer energy to close distances from the receivers, and when they do, the result is felt as an extra power-draw in the transmitter. The receiving and transmitting antennas are magnetically coupled. Change in current flow through one wire induces a voltage across the ends of the other wire through electromagnetic induction. The amount of inductive coupling between two conductors is measured by their mutual inductance. In these applications we have to refer to the near field and not to the far field radiation pattern. Wearable Diversity antennas Data recorder Belt Fig. 28. Wearable antenna Microstrip Antenna Arrays 381 Antenna location Fig. 29. Printed Antenna locations on the back for medical applications Antennas Antennas Fig. 30. Printed Patch Antenna locations for medical applications Microstrip Antennas 382 In Fig. 31and 32 several microstrip antennas for medical applications at 434MHz are shown. Fig. 31. Microstrip Antennas for medical applications Fig. 32. Microstrip Antennas for medical applications Microstrip Antenna Arrays 383 In Fig. 31 and in Fig. 32 one can see different designs of dual polarized microstrip antennas with 10% bandwidth around 434MHz. The loop antenna is with a ground plane on the antenna back. The loop antenna diameter is around 50mm. 5. Conclusion A 64 microstrip antenna array with efficiency of 67.6% and a 256 microstrip antenna array with efficiency of 50.47% have been presented in this Chapter. Methods to reduce losses in mm-wave microstrip antenna arrays have been described in this Chapter. The results presented in this chapter point out that radiation losses need to be taken into account for accurate microstrip antenna array design at mm wave frequencies. By minimizing the number of bend discontinuities the gain of the 256 microstrip antenna array has been increased by 1dB. Several applications of mm wave microstrip antenna arrays have been presented. Losses in the microstrip feed network form a significant limit on the possible applications of microstrip antenna arrays in mm wave frequencies. MM wave microstrip antenna arrays may be employed in communication links, seekers and detection arrays. The array may consist around 256 elements to 1024 elements. Design considerations of the antenna and the feed network are given in this chapter. Optimization of the antenna structure and feed network allows us to design and fabricate microstrip antenna arrays with high efficiency. This chapter presents wideband microstrip antennas with high efficiency for medical applications. The antenna bandwidth is around 10% for VSWR better than 2:1. The antenna beam width is around 100º. The antenna gain is around 2dBi. The antenna S11 results for different belt thickness, shirt thickness and air spacing between the antennas and human body are given in this chapter. The effect of the antenna location on the human body should be considered in the antenna design process. If the air spacing between the sensors and the human body is increased from 0mm to 5mm the antenna resonant frequency is shifted by 5%.The proposed antenna may be employed in Medicare RF systems. 6. References J.R. James, P.S Hall & C. Wood, (1981). Microstrip Antenna Theory and Design,1981. A. Sabban & K.C. Gupta, (1991). Characterization of Radiation Loss from Microstrip Discontinuities Using a Multiport Network Modeling Approach, I.E.E.E Trans. on M.T.T, Vol. 39,No. 4, April 1991,pp. 705-712. A. Sabban, (1991). PhD Thesis, Multiport Network Model for Evaluating Radiation Loss and Coupling Among Discontinuities in Microstrip Circuits, University of Colorado at Boulder, January 1991. P.B. Kathei & N.G. Alexopoulos, (1985). Frequency-dependent characteristic of microstrip, MTT-33, discontinuities in millimeter-wave integrated circuits, IEEE Trans. Microwave Theory Tech, vol. pp. 1029-1035, Oct. 1985. A. Sabban, (1983). A New Wideband Stacked Microstrip Antenna, I.E.E.E Antenna and Propagation Symposium, Houston, Texas, U.S.A, June 1983. A. Sabban & E. Navon (1983). A MM-Waves Microstrip Antenna Array, I.E.E.E Symposium, Tel-Aviv, March 1983. A. Sabban, (1981). Wideband Microstrip Antenna Arrays, I.E.E.E Antenna and Propagation Symposium MELCOM, Tel-Aviv,1981. Microstrip Antennas 384 M. M. Milkov, (2000). Millimeter-Wave Imaging System Based on Antenna-Coupled Bolometer, MSc. Thesis, UCLA UCLA (2000). G. de Lange et. al., (1999). A 3*3 mm-wave micro machined imaging array with sis mixers, Appl. Phys. Lett. 75 (6), pp. 868-870 (1999). A. Rahman et. al., (1996). Micromachined room temperature microbolometers for mm-wave detection, Appl. Phys. Lett. 68 (14), pp. 2020-2022 (1996). A. Luukanen et. al., US Patent 6242740 (2001). M. D. Jack et. al., (2001). US Patent 6329655 (2001). G. N. Sinclair et. al., (2000). Passive millimeter wave imaging in security scanning, Proc. SPIE Vol. 4032, pp. 40-45, (2000). G. Kompa & R. Mehran, (1975). Planar waveguide model for computing microstrip components, Electron Lett., vol. 11, no. 9, pp. 459-460, 1975. Lawrence C. Chirwa; Paul A. Hammond; Scott Roy & David R. S. Cumming , (2003). Electromagnetic Radiation from Ingested Sources in the Human Intestine between 150 MHz and 1.2 GHz, IEEE Transaction on Biomedical eng., VOL. 50, NO. 4, pp. 484-492, April 2003. D.Werber; A. Schwentner & E. M. Biebl, (2006). Investigation of RF transmission properties of human tissues, Adv. Radio Sci., 4, pp. 357–360, 2006. 16 Microstrip Antennas for Indoor Wireless Dynamic Environments Mohamed Elhefnawy and Widad Ismail Universiti Sains Malaysia (USM), Malaysia 1. Introduction This chapter is organized in two parts. The first part deals with the design and implementation of a microstrip antenna array with Butler matrix. The planar microstrip antenna array has four beams at four different directions, circular polarization diversity, good axial ratio, high gain, and wide bandwidth by implementing the 4×4 Butler matrix as a feeding network to the 2×2 planar microstrip antenna array. The circular polarization diversity is generated by rotating the linearly polarized identical elements of the planar microstrip antenna array so that the E-field in the x-direction is equal to the E-field in the y- direction. Then, by feeding the planar array with Butler matrix, phase delay of /2 π ± between those two E-fields is provided. In the second part of this chapter, the analysis, design and implementation of an Aperture Coupled Micro-Strip Antenna (ACMSA) are introduced. A quadrature hybrid is used as a feeder for providing simultaneous circular polarization diversity with a microstrip antenna; but the utilization of the quadrature hybrid as a feeder results in large antenna size. In order to minimize the antenna size, the microstrip antenna is fed by a quadrature hybrid through two orthogonal apertures whose position is determined based on a cavity model theory. The size of the proposed ACMSA is small due to the use of the aperture coupled structure. The cavity model theory is started with Maxwell's equations, followed by the solution of the homogeneous wave equations. Finally, the eigenfunction expansion for the calculation of the input impedance is presented. This chapter is organized as follows. The first part deals with design and implementation of a microstrip antenna array with Butler matrix, which describe the design details of a rectangular microstrip patch antenna and a 4×4 Butler matrix. Further, analysis of planar microstrip antenna array with Butler matrix and the development of the radiation pattern for the planar microstrip antenna array are presented. In the second part, the design and implementation of an aperture coupled microstrip antenna, the analysis of ACMSA using cavity model, the circular polarization diversity with ACMSA and the geometry of the ACMSA are described. 2. Design and implementation of the microstrip antenna array with Butler matrix A planar microstrip antenna array with a Butler matrix is implemented to form a microstrip antenna array that has narrow beamwidth, circular polarization and polarization diversity. Microstrip Antennas 386 This microstrip antenna array improves the system performance in indoor wireless dynamic environments. A circularly polarized microstrip antenna array is designed such that it consists of four identical linearly polarized patches. A 2×2 planar microstrip antenna array and a 4×4 Butler matrix are designed and simulated using advanced design system and Matlab software. The measured results show that a combination of a planar microstrip antenna array and a 4×4 Butler matrix creates four beams two of which have RHCP and the other two have LHCP. 2.1 Design of the rectangular microstrip patch antenna A rectangular microstrip patch antenna is designed based on the Transmission Line Model (TLM) in which the rectangular microstrip patch antenna is considered as a very wide transmission line terminated by radiation impedance. Figure 1 shows a rectangular microstrip patch antenna of length L and width W. M s is the magnetic current of each radiating slot of the microstrip patch antenna and s is the width of each radiating slot. Fig. 1. Inset fed rectangular microstrip patch antenna Figure 2 shows the transmission line model of the antenna where G R and C F represent the radiation losses and fringing effects respectively. The input impedance of an inset fed rectangular microstrip patch antenna is given by the equation (1) [1]. () 2 12 1 cos 2 o in R x Z GG L π ⎛⎞ = ⎜⎟ + ⎝⎠ (1) where X o is the distance into the patch, G 12 is the coupled conductance between the radiating slots of the antenna [2]. W Feed M s M s y Slot 2 s s x o x Patch Slot 1 L Microstrip Antennas for Indoor Wireless Dynamic Environments 387 Fig. 2. Transmission line model of the rectangular microstrip patch antenna The inset fed rectangular microstrip patch antenna is designed using Matlab software based on the expression for the input impedance which is given by equation (1). The input impedance depends on the microstrip line feed position as shown in Figure 3. Fig. 3. Dependence of the input impedance on the distance into the patch G R L< λ/2 Slot 2 Slot 1 G R C F C F Microstrip Antennas 388 2.2 Design of the 4×4 Butler matrix The Butler matrix is used as a feeding network to the microstrip antenna array and it works equally well in receive and transmit modes. The 4×4 Butler matrix as shown in Figure 4 consists of 4 inputs, 4 outputs, 4 hybrids, 1 crossover to isolate the cross-lines in the planar layout and some phase shifters [3]. Each input of the 44 × Butler matrix inputs produces a different set of 4 orthogonal phases; each set used as an input for the four element antenna array creates a beam with a different direction. The switching between the four Butler inputs changes the direction of the microstrip antenna array beam. Advanced design system (ADS) has been used for simulating the 4×4 Butler matrix as shown in Figure 5. Table 1 shows a summary of the simulated and the measured phases that are associated with the selected port of the 4×4 Butler matrix. Fig. 4. 4×4 Butler matrix geometry Phase A Antenna 1 Phase B Antenna 2 Phase C Antenna 3 Phase D Antenna 4 Theoretical 0 -90 -45 -135 Simulated 0 -89.813 -45.04 -135.04 Port 1 (set 1) Measured 0 -98 -50 -142.8 Theoretical 0 -90 135 45 Simulated 0 -90.273 134.142 44.773 Port 2 (set 2) Measured 0 -80.5 140.5 48.5 Theoretical 0 90 -135 -45 Simulated 0 89.369 -135.046 -44.773 Port 3 (set 3) Measured 0 86.7 -126 -43 Theoretical 0 90 45 135 Simulated 0 90 45.227 135.04 Port 4 (set 4) Measured 0 89 48 143 Table 1. Phases associated with the selected port of the 4×4 Butler matrix 90 ° Hybrid 45 ° θ − Crossover Port 1 Port 2 A Port 4 B C D 35 Ω Port 3 90 ° 50 Ω θ [...]... planar microstrip antenna with 4×4 Butler matrix Microstrip Antennas for Indoor Wireless Dynamic Environments 405 Figure 25 shows the ADS layout of the planar mirostrip antenna array with 4×4 Butler matrix The Fabricated planar microstrip antenna array with 4 × 4 Butler matrix is shown in Figure 26 Fig 25 ADS layout of the planar microstrip antenna array with 4×4 Butler matrix Fig 26 Fabricated planar microstrip. .. pattern of a single microstrip patch antenna ( Hθ ) [11]; Hθ = KoW sin θ ) 2 cosθ KoW sin θ 2 sin( (12) where W is the width of the microstrip patch antenna 2.5 Simulation and measured results To design the planar microstrip antenna array, the spacing distance between the patches in x-direction (dx) is determined based on the simulation of equations (7), (8) and (9) using 401 Microstrip Antennas for Indoor... of the Rogers's substrate Figure 23 shows the ADS Momentum for the planar microstrip antenna array Fig 23 ADS Momentum for the planar microstrip antenna array 403 404 Microstrip Antennas The planar array is simulated by using ADS Momentum and then the Momentum dataset file is imported to the ADS schematic to simulate the planar microstrip antenna with Butler matrix as shown in Figure 24 MSub MSUB MSub1... freq, GHz Fig 17 ADS simulated results for phases of path 2 and reference path 3.0 399 Microstrip Antennas for Indoor Wireless Dynamic Environments 2.3 Analysis of planar microstrip antenna array with Butler matrix A planar microstrip antenna array consists of four orthogonally oriented inset-fed rectangular patch antennas as shown in Figure 18 The circular polarization can be generated with linearly... implemented by adding a bit of length to a microstrip transmission line The ADS is used to determine the length of red sections microstrip transmission lines which introduces phase shift ( θ shift − 45°) in the signal that passes through the crossover θ shift is the phase shift of the signal passing through the black section microstrip transmission line as shown in Figure 14 θ shift is determined by finding... planar microstrip antenna array with 4 × 4 Butler matrix 406 Microstrip Antennas The measured and the simulated values of the reflection coefficient at each port of the planar microstrip antenna array with 4 × 4 Butler matrix versus the frequency band of 1.4–3 GHz are shown in Figure 27 Fig 27 Reflection coefficients versus frequency for the planar microstrip antenna array with 4 × 4 Butler matrix The phases... compared with a single microstrip patch antenna that achieves 0.7% impedance bandwidth as shown in Figure 28 [14] The implementation of the Butler matrix gives a wide band due to the absorption of the reflected power in the matched loads connected to the non-selected ports of the butler matrix Moreover, the mutual coupling between the patches enhances the bandwidth [13] Microstrip Antennas for Indoor... radiation pattern of the planar microstrip array is obtained by the following equation [9]: ET _ θ = Eθ AFT _ E (7) where AFT _ E is the normalized E-plane array factor for the planar microstrip array and can be obtained from equation (8) [10]: ( AFT _ E = 1 + e j ( Ko dx sin θ +φx ) ) (1 + e ) jφy (8) Eθ is the total normalized E-plane radiation pattern of a single microstrip patch antenna and is... Subst="MSub1" W1=W_tb mm W1=W_tb mm W=W_tb mm W1=W_50 mm W2=W_50 mm W2=W_tb mm L=l_tb mm W2=W_tb mm W3=W_lr mm W3=W_mdl mm W3=W_lr mm Fig 11 ADS schematic for the real microstrip crossover Port P2 Num=2 Port P3 Num=3 395 Microstrip Antennas for Indoor Wireless Dynamic Environments The dimensions of the real crossover are modified and optimised by using the higher level ADS schematic shown in Figure... Elevation angle 50 100 Fig 20 Simulated normalized H-plane radiation pattern of the planar microstrip antenna array versus an elevation angle (― feed at port 1, −· feed at port 2, … feed at port 3, - feed at port 4) Fig 21 Parameters setup in ADS Momentum for substrate layers of the Rogers's substrate Microstrip Antennas for Indoor Wireless Dynamic Environments Fig 22 Parameters setup in ADS Momentum . applications Antennas Antennas Fig. 30. Printed Patch Antenna locations for medical applications Microstrip Antennas 382 In Fig. 31and 32 several microstrip antennas for medical applications. applications at 434MHz are shown. Fig. 31. Microstrip Antennas for medical applications Fig. 32. Microstrip Antennas for medical applications Microstrip Antenna Arrays 383 In Fig. 31. This chapter is organized in two parts. The first part deals with the design and implementation of a microstrip antenna array with Butler matrix. The planar microstrip antenna array has four