Design Project 2: Coupled-Line Couplers - Analysis and Comparison - Prof. James Stiles, Study Guides, Projects, Research of Electrical and Electronics Engineering

Download Design Project 2: Coupled-Line Couplers - Analysis and Comparison - Prof. James Stiles and more Study Guides, Projects, Research Electrical and Electronics Engineering in PDF only on Docsity! 4/23/2009 723 Design Project_2 s09.doc 1/4 Jim Stiles The University of Kansas Dept. of EECS Design Project #2: Coupled Line Couplers PROJECT SCOPE Design a coupled-line coupler with the following specifications: Number of sections 5 Center frequency 3 GHz Coupling 12 dB Port impedance 50 Ω Frequency response Maximally Flat PROJECT TASKS: 1) Determine the odd and even mode impedances for each of the 5 sections. Implement this design in ADS. 2) Plot |S11|2, |S21|2, |S31|2 and |S41|2 (in decibels) from 0 to 6 GHz, using a vertical scale from -50 dB to 0 dB. Q1: Do these results indicate that your design is correct? Explain why you think so. Give specific numerical examples from each plot. 3) Use the markers to determine the bandwidth of your design, given that the coupling must be numerically less than 15 dB to satisfy specifications(i.e., a 3 dB bandwidth). 4/23/2009 723 Design Project_2 s09.doc 2/4 Jim Stiles The University of Kansas Dept. of EECS 4) Draw an exact signal flow graph of this (4-port) directional coupler. In other words, a signal flow graph of the form below, where c is the specific coupling coefficient of this coupler at the design frequency. 5) Reduce this signal flow graph for the case where ports 2, 3, and 4 are terminated in matched loads ( 2 3 4 0L L LΓ =Γ =Γ = ), and determine in decibels the numeric values of |S11|2, |S21|2, |S31|2 and |S41|2, at the design frequency. Q2: Do these values precisely match those provided by the ADS analysis? Why or why not? 6) Now “attach” a short circuit ( 4 1LΓ = − ) to port 4 of the coupler signal flow graph (with ports 2 and 3 again terminated in matched loads). Reduce this graph and determine in decibels the numeric values of |S11|2, |S21|2, |S31|2, at the design frequency. 7) Likewise place a short circuit on port 4 of your ADS design—you now have a 3-port device! Replot |S11|2, |S21|2, |S31|2 (in dB) from 0 to 6 GHz, using the same vertical scale as before. Note you should not plot |S41|2! 1a 1b 2a 4a 3a 2b 3b 4b c c c c 21j c− − 21j c− − 21j c− − 21j c− −