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Ex 1

The document outlines a lab exercise focused on designing passive two-element LC impedance matching circuits using both software and Smith Chart techniques. It explains the use of LC networks to match impedances between a source and load, detailing configurations for high-pass and low-pass circuits, and the limitations of these networks. The procedure includes tasks for matching specific loads at different operational frequencies and analyzing the results using Smith Charts.

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Bruno Matias
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18 views2 pages

Ex 1

The document outlines a lab exercise focused on designing passive two-element LC impedance matching circuits using both software and Smith Chart techniques. It explains the use of LC networks to match impedances between a source and load, detailing configurations for high-pass and low-pass circuits, and the limitations of these networks. The procedure includes tasks for matching specific loads at different operational frequencies and analyzing the results using Smith Charts.

Uploaded by

Bruno Matias
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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ELEC 412 2-Element Matching Lab 1

Passive Two Element Element Impedance Matching Circuits

I. OBJECTIVE

Design using software and by hand (Smith Chart) RF impedance matching circuits using passive
elements L and C.

II. INTRODUCTION

IMPEDANCE MATCHING USING DISCRETE L'S AND C'S

Passive LC networks are used to match impedances between the source (generator) and a load.
These matching networks are designed using combinations of inductors and capacitors. Two
simple LC impedance matching networks are shown: two element LC high-pass and LC low-
pass networks can be used. Smith charts can be used as a tool to design of these networks.

On a Smith Chart, transmission lines are depicted using a constant SWR circle with its arc equal
to the fractional wavelength corresponding to the operational frequency of the circuit. Series
resistors and shunt resistors are shown on a Smith Chart as following constant resistance or
conductance circles. Constant reactance X or susceptance B lines of the Smith Chart are
followed for capacitors and inductors.

Unfortunately, simple two element LC impedance matching networks cannot be used for all
possible load impedances, ZL . The limitation of the two element LC impedance matching
networks are shown as forbidden regions. Impedances that lie in the forbidden area cannot be
matched to the source impedance, ZO, using the simple two element LC impedance matching
networks discussed in this handout.

Two Element LC Low-Pass Impedance Matching Network

Two-element LC impedance matching networks are shown in Figure 1. In all four


configurations shown in Figure 1, source is to the left of the LC circuit. LC impedance matching
circuits can either be high pass or low pass circuits. Clockwise from the top left of Figure 1, the
circuits configurations are low pass, low pass, high pass, and high pass. The Smith chart is used
to determine the component values for L and C. As is customary, the impedances of L and C are
normalized to the source impedance of ZO.
ELEC 412 2-Element Matching Lab 2

Figure 1. Two Element LC Impedance Matching Circuits and Their Forbidden Regions.

III. PROCEDURE

A. Various Impedance Matching Circuits for Zsource = 50 Ω


Use the Smith Chart (Berner Smith V2.01) to determine C and L to match a 50 Ω generator to
the following loads: 25 + j 100 Ω and 25 - j 25 100 Ω.
(1) Determine the appropriate configurations that can be used for matching the specified
loads.
(2) For an operational frequency of 1 GHz, determine the values of L and C for each
circuit
(3) Perform two of these designs using both hand analysis with Z-Y Smith Charts
confirmed with Berner Smith Software.

B. Impedance Matching Circuits Off Design Frequency


For the two designs in Part (a), alter the operational frequency to 1.5 GHz. Use either the Berner
Smith Chart of by hand analysis (Z-Y Smith Chart) to determine the Zin of the matching circuit.
What is the resulting SWR when connected to Zsource = 50 Ω?

C. Comment On Your Results

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