A Novel Compact Planar Phase Shifter with a Microstrip Radial Stub

Transcription

1 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp Sensrs & Transducers 214 by IFSA Publishing, S. L. A Nvel Cmpact Planar Phase Shifter with a Micrstrip Radial Stub 1, 2 Weimin WANG, 1, 2 Yuanan LIU, 1, 2, 3 Yngle WU 1 Schl f Electrnic Engineering, Beijing University f Psts and Telecmmunicatins, Beijing, 1876, China 2 Beijing Key Labratry f Wrk Safety Intelligent Mnitring, Beijing University f Psts and Telecmmunicatins, 1876, China 3 The State Key Labratry f Millimeter Waves, Sutheast University, Nanjing, China 1 Tel.: , fax: wangwm@bupt.edu.cn Received: 13 June 214 /Accepted: 29 August 214 /Published: 3 September 214 Abstract: This paper presents a nvel cmpact phase shifter with simple planar structure. The cnfiguratin cnsists f a micrstrip line and a micrstrip radial stub t implement wide-band phase shifting functins. Changing the length f the micrstrip line and the angle f the radial stub, arbitrary phase differences can be btained. Fr demnstratin purpse, a 45 and 9 phase shifter are designed, fabricated and measured. The gd agreements verify ur prpsed structure and design methd. Cpyright 214 IFSA Publishing, S. L. Keywrds: Cmpact, Planar, Phase shifter, Micrstrip, Radial stub. 1. Intrductin Phase shifters are widely used in many micrwave circuits. They are mst imprtant cmpnents in phase-array antenna systems in which they are used t cntrl phases. With the develpment f wireless cmmunicatins, mre and mre cmpact and simple phase shifters are needed. Phase shifters can be made f cupled lines [1] and micrstrip lines [2] fr simple structures. T get larger bandwidth fr cupled-line structure, tighter cuplers are needed which increases the difficulty f fabricatin [3]. T avid using t clsed cupled lines, [4] prpsed a structure f tw layers f micrstrip substrate t get tight cupling perfrmance thrugh lcating an elliptical slt in the mid layer. But the multilayer substrate leads t high cmplexity and cst. Cmpared t [1, 5-7] presented the mdified Schiffman phase shifters with a patterned grund structure, which has the drawback f bringing serius radiatin in this structure. Transmissin-line phase shifters have planar structures. They always use pen r shrted stubs laded nt a lng transmissin line t realize phase shifters [8, 9]. But these structures ften need a large grund and high impedance stubs which lead t a big size circuit bard. Other methds have been presented t realize phase shifters [1-13]. But using reactive cmpnents in [1-12] and a vertically installed cupling structure in [13] are nt suitable fr mass prductin. In this paper, a nvel cmpact planar phase shifter is presented. The structure f the phase shifter is very simple which is cmpsed f a micrstrip line and a micrstrip radial stub. As an alternative t the cnventinal straight stub, the radial stub has the advantages f a very lw characteristic impedance and an accurate lcalizatin f the impedance reference plane [14, 15]. The phase shifter can realize 21

2 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp any phase shift degrees flexibly with the transmissin line f different electrical length. Thrugh adjusting the radius and the sectr angle f the radial stub, phase shifters with gd perfrmance can be achieved. The available design parameters f typical examples are presented. Tw phase shifters f 9 and 45 phase degree are designed, fabricated, and measured. The calculated and measured results verify ur prpsed idea. 2. The Prpsed Circuit and Design Apprach The circuit cnfiguratin f the prpsed phase shifter is shwn in Fig. 1. The structure cnsists f a micrstrip line which characteristic impedance is 5 Ω and a shunt micrstrip radial stub which characteristic impedance is defined by its gemetry parameters. The gemetries and the parameters f the shunt radial stub are shwn in Fig. 2. Parameters ϕ (sectr angle f the radial stub) and are t be determined. The input impedance f the radial stub is [16] Z 2 2 6πh [ln( βr / 2) + γ] β r + 4 = j ( ) β, (1) 2 1 ωμ 1 j h ( + ) ϕ ( r r ) β (1 ε ) ωε i in 2 2 ϕ ε r e ri i e where β = 2π εe / λ, ε e is the equivalent relative permittivity f the micrstrip with the width f w= ( ri + r)sin( ϕ /2), and γ is the Euler-Mascherni cnstant (.5772). Fig. 1. The circuit cnfiguratin f the prpsed phase shifter with a micrstrip radial stub. e Frm equatin (1), it can be bserved that the input impedance f the radial stub is decided by and ϕ if r i is a cnstant value. T simplify the calculatin prcess, a simulatin ADS tl is used t calculate the impedances f the radial stub. Fig. 3 shws the calculated input impedances f the radial stub with different and different ϕ. Since the input impedance f the shunt radial stub is reactance, the mdulus f the input impedance values is shwn in Fig. 3. Frm Fig. 3, we can see that the values f and ϕ affect the input impedances f the radial stub, thereby they can affect the frequency band f the phase shifter. By selecting suitable values f r and ϕ, phase shifters with gd perfrmance can be achieved. Input Impedances(Mdulus,Ohm) Input Impedances((Mdulus,Ohm) =3 mm =35 mm =39.6 mm =45 mm =5 mm Sectr angle=1 deg Sectr angle=15 deg Sectr angle=2 deg Sectr angle=3 deg Sectr angle=4 deg (a) Z in Wi r i (b) Fig. 3. The calculated input impedances(mdulus) f the radial stub with (a) different and (b) different ϕ. ϕ Fig. 2. Gemetries and parameters f the micrstrip radial stub. As illustrated in Fig. 4, the radial stub with different ϕ causes different frequency band f the phase shifter. The smaller value f ϕ is, the brader band f the phase shifter can be achieved. T equalize larger bandwidth and fabricatin technique, the value f ϕ is always nt smaller than 1. 22

3 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp ),(Degree)=9deg Sectr angle=1deg Sectr angle=2deg Sectr angle=3deg Sectr angle=4deg Fig. 4. The phase differences f the prpsed phase shifter with different ϕ. Fig. 5 presents the ideal scattering parameters and phase differences f fur typical phase shifters with a radial stub f r = 39.7 mm, ϕ = 2 at the frequency f 2.6 GHz. Frm Fig. 5, we can see that whenever the phase differences are 3, 45, 6 and 9, the values f S are all belw 2 db in the 11 whle frequency band. The center frequency f phase shifters happens at 2.8 GHz (phase-shift degrees are 3, 45, 6 ) and 3.2 GHz (phase-shift degree is 9 ) respectively shwn in Fig. 5(c). Since the phase shift degree f 9 ± 1 is btained acrss the frequency range f 2.23 GHz GHz (including 2.8 GHz GHz ), the perfrmance f the phase shifter is acceptable S 11 (phasediff=9deg) S 11 (phasediff=6deg) S 11 (phasediff=45deg) S 11 (phasediff=3deg) S 33 (phasediff=9deg) S 33 (phasediff=6deg) S 33 (phasediff=45deg) S 33 (phasediff=3deg) (a) (b) ),(Degree) phasediff=9deg phasediff=6deg phasediff=45deg phasediff=3deg (c) Fig. 5. The calculated results f fur typical phase shifters (phase shift degree is 3, 45, 6, 9 respectively) with a radial stub f r = 39.7 mm, ϕ = 2 : (a) scattering parametef S 11, (b) scattering parameters f S 33, (c) phase differences. 3. Examples T verify the prpsed idea experimentally, tw typical examples are designed, fabricated, and measured. The first phase shifter (A) is fr 9 phase shift. The secnd phase shifter (B) is fr 45 phase shift. F4B with a dielectric cnstant f 2.65 and a thickness f 1 mm is used as the substrate. The 23

4 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp crrespnding micrstrip layut with defined physical parameters is determined as demnstrated in Fig. 6. l 2 ϕ l 1 Fig. 6. The layut f the designed phase shifter. Fig. 7 shws the phtgraphs f the fabricated phase shifters. T demnstrate the relatinship between the frequency band f the phase shifter and the angle ϕ f the radial stub, the value f ϕ is selected 2 and 1 respectively. The parameters f phase shifter A are l 1 = 4 mm, l 2 = 2 mm, r = 39.6 mm, ϕ = 2. The parameters f phase shifter B are l 1 = 3 mm, l 2 = 2 mm, r = 39.6 mm, ϕ = 1. Fig. 8 presents the simulated and measured results f the fabricated phase shifters. Frm Fig. 8(b), we can get that phase shift degree f 9 ± 1 is btained acrss the frequency range f GHz (simulated) and GHz (measured). Frm Fig. 8(c), we can btain that phase shift degree f 45 ± 5 is btained acrss the frequency range f GHz (simulated) and GHz (measured). The results shw that the frequency band f the fabricated phase shifter has sme deviatin frm the simulated. Since all the values f S 11 with phase shifter A are all belw 13dB, and the values f S 11 with phase shifter B are all belw 15 db, the influences are acceptable in practical applicatin. The simulated and measured results verify the availability f the prpsed structure Simulated S 11 Measured S 11 Simulated S 33 Measured S Fig. 8 (a). The simulated and measured results f the fabricated phase shifters S parameters f A. (a) -1 ),(Degree) Simulated Measured (b) Fig. 7. The phtgraphs f the fabricated phase shifters (a) A and (b) B Fig. 8 (b). The simulated and measured results f the fabricated phase shifters phase difference f A. 24

5 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp ),(Degree) Simulated S 11 Measured S 11 Simulated S 33 Measured S 33 Fig. 8 (c). The simulated and measured results f the fabricated phase shifters S parameters f B Simulated Measured Fig. 8 (d). The simulated and measured results f the fabricated phase shifters phase difference f B. 4. Cnclusins A nvel cmpact phase shifter with a radial stub is prpsed. The prpsed structure is planar and simple. The parameters which influence the input impedances f the radial stub and the frequency band f the phase shifter are analyzed. The design parameters f typical examples fr phase shifters are illustrated. Tw phase shifters are designed, fabricated and measured. The simulated and measured results verify the designed structure and the analysis. It is believed that the prpsed structure ffers an alternative where simple and planar phase shifters are required. Acknwledgements This wrk was supprted in part by Natinal Natural Science Fundatin f China fr the Majr Equipment Develpment (N ), Natinal Natural Science Fundatin f China (N ), and Natinal Science & Technlgy Majr Prject (N. 212ZX311-2, 212ZX331-4). References [1]. B. M. Schiffman, A new class f brad-band micrwave 9-degree phase shifters, IEEE Transactins n Micrwave Thery and Techniques, Vl. MTT-6, Issue 4, April 1958, pp [2]. S. Y. Zheng, W. S. Chan, and K. F. Man, Bradband phase shifter using laded transmissin line, IEEE Micrwave and Wireless Cmpnents Letters, Vl. 2, Issue 9, 21, pp [3]. J. Taylr, and D. Prigel, Wiggly phase shifters and directinal cuplers fr radi-frequency hybridmicrcircuit applicatins, IEEE Transactins n Parts, Hybrids, and Packaging, Vl. PHP-12, Issue 4, December 1976, pp [4]. A. M. Abbsh, Ultra-wideband phase shifters, IEEE Transactins n Micrwave Thery and Technlgy, Vl. 55, Issue 9, September 27, pp [5]. Z. Zhang, Y. C. Jia, S. F. Ca, X. M. Wang, and F. S. Zhang, Mdified bradband Schiffman phase shifter using dentate micrstrip and patterned grund plane, Prg. Electrmagn. Res. Lett., Vl. 24, 211, pp [6]. Y. X. Gu, Z. Y. Zhang, and L. C. Ong, Imprved wide-band Schiffman phase shifter, IEEE Transactins n Micrwave Thery and Technlgy, Vl. 54, Issue 3, March 26, pp [7]. M. A. Hnarvar, F. Jlani, A. Dadgarpur, and B. S. Virdee, Cmpact wideband phase shifter, Internatinal Jurnal f RF and Micrwave Cmputer-Aided Engineering, Vl. 23, Issue 1, January 213, pp [8]. J. Dittlff, F. Arndt, and D. Grauerhlz, Optimum design f waveguide E-plane stub-laded phase shifters, IEEE Transactins n Micrwave Thery and Techniques, Vl. 36, Issue 3, March 1988, pp [9]. X. Tang, and K. Muthaan, Design f a UWB phase shifter using shunt λ/4 stubs, in IEEE MTT-S Internatinal Micrwave Sympsium Digest, June 29, pp [1]. D. W. Kang, H. Lee, K. H. Lee, S. I. Jen, and S. Hng, Design f a phase shifter with imprved bandwidth using embedded series-shunt switches, in Prceedings f the Eurpean Micrwave Cnference, Vl. 3, 25, ( articledetails.jsp?arnumber=161369). [11]. X. Tang, A bradband 18 phase shifter with a small phase errr using lumped elements, in Prceedings f the Asia Pacific Micrwave cnference, 29, pp [12]. Y. Chung, B. C. Deckman, and M. P. Delisi, Bradband phase shifters using cmplementary frequency-dependent Δphase f lw-/high- pass filters, Micrwave and Optical Technlgy Letters, Vl. 55, N. 3, March 213, pp [13]. S. Y. Zheng and W. S. Chan, Bradband differential phase shifter using vertically installed cupled structure, in Prceedings f the Asia-Pacific Micrwave Cnference, 211, pp [14]. F. Giannini, R. Srrentin, and J. Vrba, Planar circuit analysis f micrstrip radial stub, IEEE Transactins n Micrwave Thery and Techniques, Vl. MTT-32, Issue 12, December 1984, pp

6 Sensrs & Transducers, Vl. 179, Issue 9, September 214, pp [15]. F. Giannini, M. Ruggieri, and J. Vrba, Shuntcnnected Micrstrip radial stub, IEEE Transactins dual-band micrwave cmpnents, Beijing University [16]. X. Liu, The study and design f the size-reduced and n Micrwave Thery and Techniques, Vl. MTT-34, f Psts and Telecmmunicatins, Beijing, Chapter 3, Issue 3, March 1986, pp , pp Cpyright, Internatinal Frequency Sensr Assciatin (IFSA) Publishing, S. L. All rights reserved. ( 26