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1. SINGLE STUB MATCHING
Design a single stub shunt tuning network to match a 50 transmission line to
a load impedance 60-j80 (resistor and capacitor in series) at 2GHz. The
substrate given is FR4 with the following specifications: dielectric constant
(r= 4.5), height of the substrate (H=1.6mm), thickness of the conductor
(copper, T=.035mm), Loss tangent of the dielectric material
(Tand = 0.002). Compare the results of return loss using circuit simulation
(Microwave office).
THEORY:
Single stub tuning circuit is convenient because the stubs can be fabricated as
a part of transmission line media of the circuit, and lumped elements are
avoided. Shunt stubs are preferred for microstrip line or stripline. For lines
like coax or waveguide, short-circuited stubs are preferred because the cross-
sectional area of open-circuited line may be large enough (electrically) to
radiate, in which case the stub is no longer purely reactive.
13BEC0850 [L29+L30]

PROCEDURE:
1. Using smith chart find the value of l and d with the given Zl, Z0 and
frequency. Open AWR.
2. File ->New Project.
3. Project -> Project Options -> Edit.
4. Select the start frequency, stop frequency and the step size.
5. Click Apply. Change the default metric unit to mm. Click Ok.
6. Circuit Schematics -> New Schematic.
7. Place the substrate (MSUB), transmission line (MLIN), resistor
(RES), capacitor (CAP), port and ground from the element menu.
8. Set the values of the substrate as given in the question.
9. Go to Tools -> TXLine. Calculate the Physical length and width of the
transmission line.
10. Save the project.
11. Graphs-> New Graph.
12. Right Click -> Add New Measurement. Choose the ports (1,1).
Click Apply -> Click Ok. Save the project.
13. Simulate -> Analyze.
ADVANTAGE:
It can match complex loads, easy to implement.
DISADVANTAGE:
It cannot match variable load impedances.

2. DOUBLE STUB MATCHING
Design a double stub shunt tuner to match a load impedance 60-j80 to a 50
line. The stubs are to be open-circuited stubs and are spaced /8 apart.
Assuming that this load consists of a resistor and capacitor and that the match
frequency is 2 GHz. The substrate given is FR4 with the following
specifications: dielectric constant (r= 4.5), height of the substrate
(H=1.6mm), thickness of the conductor (copper, T=.035mm), Loss
tangent of the dielectric material (Tand = 0.002). Compare the results of
return loss using circuit simulation (Microwave office).
THEORY:
The single-stub tuner is able to match any load impedance (having a positive
real part) to a transmission line, but suffers from the disadvantage of
requiring a variable length of line between the load and the stub. This may not
be a problem for a fixed matching circuit, but would probably pose some
difficulty if an adjustable tuner was desired. In this case, the double-stub tuner,
which uses two tuning stubs in fixed positions, can be used. Such tuners are
often fabricated in coaxial line with adjustable stubs connected in shunt to the
main coaxial line.

PROCEDURE:
1. Using smith chart find the value of l1 and l2 with the given Zl, Z0 and
frequency. Open AWR.
(RES), capacitor (CAP), port and ground from the element menu.
9. Go to Tools -> TXLine. Calculate the Physical length and width of the
transmission line.
ADVANTAGE:
It can match complex as well as variable load impedances.
DISADVANTAGE:
Load values lying in forbidden region cannot be matched.
NOTE: The load admittance values which lie within the forbidden circle ( )
cannot intersect the rotated circle, thereby giving a null solution.
2G
Bj1

3. L-SECTION MATCHING
Design an L-section matching network to match a series RC load with an
impedance ZL = 200-j100 to a 100 at 500MHz. The substrate given is FR4
with the following specifications: dielectric constant (r= 4.5), height of the
substrate (H=1.6mm), thickness of the conductor (copper, T=.035mm),
Loss tangent of the dielectric material (Tand = 0.002). Compare the
results of return loss using circuit simulation (Microwave office).
THEORY:
Simplest type of matching network is the L-section, which uses two reactive
elements to match an arbitrary load impedance to a transmission line. If the
frequency is low enough and/or the circuit size is small enough, actual
lumped-element capacitors and inductors can be used. This may be feasible
for frequencies up to about 1 GHz or so, although modern microwave
integrated circuits may be small enough such that lumped elements can be
used at higher frequencies as well. There is, however, a large range of
frequencies and circuit sizes where lumped elements may not be realizable.
This is a limitation of the L-section matching technique.
L-section matching networks. (a) Network for ZL inside the 1 + j x circle. (b) Network
for ZL outside the 1 + j x circle.

PROCEDURE:
1. Using smith chart find the value of b and x with the given Zl, Z0 and
frequency.
2. Calculate C and L from b and x respectively. Open AWR.
(RES), capacitor (CAP), inductor (IND) port and ground from the
element menu.
10. Go to Tools -> TXLine. Calculate the Physical length and width of
the transmission line.
ADVANTAGE:
It is easy to implement and reliable at low frequencies ( 1 GHz)
DISADVANTAGE:
It cannot be used at higher frequencies. Also it is narrow band tuner.

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