Bandwidth enhancement of microstrip antennas by staggering effect

Abstract

dimensions: length L ¼ 35.9 mm, width W ¼ 32 mm. Inserted microstrip feed line section provides 50 X input element impedance. Two-bit phase shifters are implemented on the base of switched-line concept, which uses electronically controlled switches and lines of different lengths to obtain a set of phase steps. Outputs of the antenna array elements are connected with 50 X inputs of feed line that has 50 X output impedance and combines all signals into one output. AOA measurement setup is shown in Figure 8b. Linear array mounted on turn table can change azimuth position relative to RF incoming source angle.Photograph of the fabricated array prototype is shown in Figure 8c. Designed array is fabricated on an h ¼ 1.6 mm FR-4 substrate with an element separation equal 7.5 cm which is 0.5 of the free space wave length. Switch system consists of commercially available SPDT switches RF2436 from RF Micro Devices. Array is built according to the block diagram shown in Figure 8a. Integrated amplifier ERA-6 (measured gain is about 9 dB) is used for amplification in reference channel. Power supplier and control circuits are placed on the back side of the FR-4 board.Two series of experiments were conducted with four antenna array elements: first one refers to the RF wave coming from the angle h ¼ 20 to the array normal and the other one-to h ¼ 40 . Tables 2 and 3 show power measurements results P k (h,r) (dB scale normalized to the value P k (h,0)) due to the differential phase shifts 0 (r ¼ 0), 90 (r ¼ 1), 180 (r ¼ 2), and 270 (r ¼ 3) realized by k-th element phase shifter.Using power measurement results and formulas (1)-(4) we estimated arrival angle h est : h est (h ¼ 20 ) ¼ 22 and h est (h ¼ 40 ) ¼ 34 . Simulations based on an amplifier gain equal 10 dB in reference channel show h est0 (h ¼ 20 ) ¼ 21 and h est0 (h ¼ 40 ) ¼ 36 . We see good agreement between measurements and simulation. The error 4 between simulation and original AOA for original arrival angle equal 40 can be reduced up to 1 by increasing the amplifier gain to the value 20 dB. Table 4 demonstrates the effect of instrumental errors in power measurements. We used power measurement data from Table 3, added random errors (imitating measurement errors) and performed AOA algorithm. Table 4 shows 10 AOA estimations for uniformly randomly distributed instrumental errors: column 1 corresponds to the interval 60.5 dB; column 2 -to the interval 61 dB; and column 3-to the interval 62 dB.It is seen that random errors in power measurements 62 dB or less do not effect on AOA errors more than 10 . CONCLUSIONWe investigate car angle position system proposed for automotive applications particular for determination of the car location in large parking lot. Key of the system is small phased antenna array. Array consists of small number of elements with two-bit phase shifters and one reference element with an amplifier. Computer modeling is presented for four and eight array elements. Simulation results are shown as functions of the algorithm processing errors, phase shifters e...

Compact Modified Ground Plane (MGP) Microstrip Antenna with Narrowband and Wideband Resonance Characteristics

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