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Preliminary investigation on effective grounding measurement of Preliminary investigation on effective grounding measurement of Document Transcript

  • International Journal of Electronics and Communication Engineering & Technology (IJECET), INTERNATIONAL JOURNAL OF ELECTRONICS AND ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Special Issue (November, 2013), pp. 45-48 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com IJECET ©IAEME Preliminary Investigation on Effective Grounding Measurement of Microstrip Line Satya Sai Srikant Assistant Professor, SRM University, Modinagar Campus, 201204, India satya.srikant@gmail.com ABSTRACT: This paper is to find the RF measurement when microstrip is effectively grounded. The manufacturing method is used for grounding measurement for VIA hole inductance measurement. The available structure for the present investigation was fabricated on GaAs substrate. In this paper, wafer probing measurement and mean value of VIA hole inductance is measured with vector network analyzer (VNA) with proper calibration, when the package is effectively grounded. Further studies are in progress. KEYWORDS: Microstrip, VNA, Groundings, VIA Hole, RF probe, Calibration I. INTRODUCTION The high frequency performance of monolithic microwave integrated circuits (MMIC) is highly affected by the way in which package is grounded. Microstrip has not any topside ground plane, so some means of achieving a low inductance ground must require. The manufacturing method grounding is used; requires a topside metallization pattern near the periphery of the wafer which can be connected to the chip ground. If the field effect transistor (FET) is located at the edge of the chip in MMIC, the source grounding can be affected by multiple wire bounds to the surrounding chip carrier. Practically, FET does not locate near the chip edge as grounding consideration and its calculations due to continuous variations will be very cumbersome task [1]. II. MATERIAL AND METHODS A. Raw Materials Holes are chemically milled through the GaAs substrate (εr = 10.8) until the topside metallization is reached. Such a hole is called as VIA hole groundings. Fig. 1 shows a simplified cross section of substrate with VIA holes in which it contains one VIA hole; that pad out to two terminals. The signal / ground structure approximates to a 50 Ω microstrip to the VIA hole and is intended for wafer probing measurement. The layout minimizes the interconnecting parasitic because the 50 Ω microstrip is maintained up to the edges of the VIA hole. Fig. 2 International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 45
  • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME shows the equivalent circuit of Signal / Ground RF probe. The parameters of 50 Ω microstrip line segments are: Zo(εr ) = 50 Ω, l = 2771µm, h = 200 µm, εr = 12.8, ϴ = 9 º / GHz, w = 100 µm 100 Ω Signal / Ground Signal Plane One Via Hole Ground Plane Fig. 1: Cross sectional view of microstrip with effective grounding Fig. 2: Equivalent circuit of RF probe B. Experimental Set up and Methods The VIA grounding directly connect the signal conducting plane and ground plane of microstrip that is to be measured for low valued inductance from vector network analyzer (VNA) with manufacturing method [2]. Fig. 3 is the set up for measuring the VIA inductance. It is desired to measure the mean value of VIA hole inductance by the manufacturing approach in the range of 1- 5 GHz. This helps in studying the effective dielectric constant and characteristic impedance for microstrip with dispersion effect when the package is grounded. Fig. 3: Set up for measuring the VIA inductance, Microstrip with VIA holes & Equivalent circuit International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 46
  • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME III. ANALYTICAL METHOD The S parameter S11 of a 50 Ω microstrip line segment terminated by VIA hole and subsequent de-embedding the line segment results in VIA inductance [1,3,4]. The S parameter (S11) is measured with the help of vector network analyzer (VNA). With the help of S11, the input impedance Zin can be found out by pressing Smith Chart menu in VNA. The load impedance Zl for measured input impedance Zin can be evaluated by using Transmission line concept. + + = = + = = = + + ) ⁄[ ( ( = ( = ) + ) + ( + − ) ] + ⁄[ ( ) + ( + ) ] ⁄2 = The calibration of RF probe and VNA must be needed before the measurement of VIA inductance. The measurement of VIA inductance requires a one port calibration, so LRM (Line – Reflect – Match) is the most convenient calibration. It means that in LRM technique, the short calibration is not used. IV. RESULT AND DISCUSSION The measurement of VIA inductance in preliminary investigation on considering the effective groundings of 50 Ω microstrip line is shown in Table 1. This grounding includes the effect of pad inductance. The investigation satisfies the estimated inductance of a VIA Hole is approximation 25 – 100 pH /mm of substrate thickness. However in practical case, the value of the mean VIA hole inductance is approximation 40 – 55 pH for 200 µm substrate thickness. Frequency (GHz) 1 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5 Measured Re(Zin) in Ω 0.679 0.661 0.739 0.890 1.122 1.388 1.558 1.606 1.631 1.894 2.116 2.303 Measured Im(Zin) in Ω 8.818 10.616 14.166 18.028 21.830 25.675 29.726 33.965 38.659 43.743 49.295 52.312 LVIA (pH) 54.510 54.270 52.961 51.880 49.528 46.278 43.640 39.810 36.360 32.897 29.498 27.847 Table 1: Calculation of VIA Inductance (LVIA) {Mean LVIA = 43.29 pH} International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 47
  • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME V. CONCLUSION The preliminary studies of effective grounding of microstrip are investigated with vector network analyzer which shows the presence of impedance (VIA inductance) even though the microstrip is effectively grounded. The value of VIA resistance measured from VNA shows that it is almost zero. This shows that the high frequency performance of monolithic microwave integrated circuits (MMIC) like microstrip with grounded is highly affected with VIA inductance. This study is very useful in designing the filters, amplifiers, oscillators, antennas, resonators, feeder, planner loads. ACKNOWLEDGEMENT I am thankful to Prof. Manoj Kumar Pandey, Director of SRM University, Modinagar for encouraging me to perform the research work in the field of RF and Microwave electronics. Thanks are also due to some of the scientists and research faculites of various laboratories for their invaluable suggestions on this subject. REFERENCES [1] Snow, Philip and Wilson Terry "Two techniques for characterizing MMIC VIA holes" Microwaves and RF Jr, vol. 27, Sept. 1988, pp 98-101. [2] R Pucel “Design consideration for MMIC” IEEE Transactions on Microwave Theory and Techniques, June 1991,vol 29 (6), pp 513 – 534. [3] R Faraji Dana and Y L Chow, “The ac resistance of a microstripline and its ground plane,” in IEEE MTT-S Int. Microwave Symposium Digest, June 1989, Long Beach, CA. [4] M Goldfarb and R Pucel, “Modeling VIA hole grounds in microstrip,” IEEE Microwave Guided Wave Letter, vol. 1 (6) , June 1991, pp 135-137. BIOGRAPHY Satya Sai Srikant was born 1974 at Dhanbad, Jharkhand, India. He received his M.Tech degree in Microwave Electronics from University of Delhi, India in 2002. From 2002-2009, he worked as research area with different position in various R & D Organizations, India in the field of RF and applications of microwaves in Minerals and Materials Technology. From 2009 onwards, he is working as Assistant Professor, in Department of Electronics and Communication Engineering, SRM University, Modinagar, India. The author has recently submitted his PhD thesis in Microwave area at ITER Bhubaneswar, Odisha, India. His current research interests focus on Microwave circuits, antennas, application of Microwave energy in Minerals and Materials Technology and system interfacing with Microwaves. International Conference on Communication Systems (ICCS-2013) B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India October 18-20, 2013 Page 48