Lec17Hybrids - 1 ECE 488 RF Circuits and Systems Spring...

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Unformatted text preview: 1 ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 1 Impedance Inverters Transmit/Receive Switches Hybrids ECE 488 RF Circuits and Systems Spring 2009 Lecture 17 2009/2/27 ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 3 Inverters obey the relation: Examples: Opens transform to shorts: Shorts transform to opens: Real impedances are transformed to real impedances: 100 to 25 : 100 to 50 : Also visa-versa Impedance Inverters Simple Theory = = in Load Z Z 100 50 25 2 = 100 7 . 70 50 2 = Load in Z Z Z 2 = = = in Load Z Z Very useful! ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 4 RF impedance transformations: Power splitters/combiners RF switches: Transmit/Receive switches Phasing switches Hybrids Power splitters/combiners Balanced amplifiers Coupled resonator band-pass filter design Conversion of series resonators to parallel resonators Conversion of parallel resonators to series resonators Impedance Inverter Uses Load in Z Z Z 2 = ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 5 Impedance Inverters Construction Quarter-wave sections of transmission line: Quarter-Wave Transformers Discrete components: T or configurations of capacitors and inductors depending on characteristic impedance, : Values: , Load in Z Z Z / 2 = L Z = ) /( 1 C Z = Z ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 7 Transforming parallel components to series components Impedance Inverters Load in Z Z Z / 2 = L P C P R P P S R Z R / 2 = L S C S 2 / Z L C P S = C P R P 2 Z C L P S = R P C S Transmission line used here, but inverters could be made of discrete components. ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 8 L L L L in Z Z jZ Z Z Z jZ Z jZ Z Z jZ jZ Z Z jZ Z 2 2 2 2 2 2 = = = Impedance Inversion Proof L Z = 2 jZ Z Z jZ Z jZ Z L L L + = ) /( 1 Z C = 1 jZ Z Z jZ Z L L = in Z 1 Z 2 Z L 2 jZ Z Z jZ jZ Z L L = 2 jZ Z Z L = QED! / Z L = 2 ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17: 9 Power Spliting/Combining 100 Antennas. 100 in parallel with 100 matches 50 . 70.7 inverters transform from 50 to 100 , and connecting the two 100 inputs puts it back to 50 . ECE 488 RF Circuits and Systems Spring 2009 Swartz 06/3/27 Lecture 17:10 Transmit/Receive (TR) Switch Quarter-wave impedance inverters Sections (2, 4, 5, 7) Diode switches Using PIN diodes RFC pass DC bias for diodes but block RF Can be spark gaps Auto switching (firing) Sections 4, 5, 6, and 7...
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Lec17Hybrids - 1 ECE 488 RF Circuits and Systems Spring...

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