Category: Microwave Engineering Objective Questions

250+ TOP MCQs on Impedance Matching Using Slotted Lines and Answers

Microwave Engineering Interview Questions and Answers for freshers on “Impedance Matching Using Slotted Lines”.

1. Slotted line is a transmission line configuration that allows the sampling of:
A. electric field amplitude of a standing wave on a terminated line
B. magnetic field amplitude of a standing wave on a terminated line
C. voltage used for excitation
D. current that is generated by the source
Answer: A
Clarification: Slotted line allows the sampling of the electric field amplitude of a standing wave on a terminated line. With this device, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.

2. A slotted line can be used to measure _____ and the distance of _____________ from the load.
A. SWR, first voltage minimum
B. SWR, first voltage maximum
C. characteristic impedance, first voltage minimum
D. characteristic impedance, first voltage maximum
Answer: A
Clarification: With a slotted line, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.

3. A modern device that replaces a slotted line is:
A. Digital CRO
B. generators
C. network analyzers
D. computers
Answer: C
Clarification: Although slotted lines used to be the principal way of measuring unknown impedance at microwave frequencies, they have largely been superseded by the modern network analyzer in terms of accuracy, versatility and convenience.

4. If the standing wave ratio for a transmission line is 1.4, then the reflection coefficient for the line is:
A. 0.16667
B. 1.6667
C. 0.01667
D. 0.96
Answer: A
Clarification: ┌= (SWR-1)/ (SWR+1). Substituting for SWR in the above equation for reflection co-efficient, given SWR is 1.4, reflection co-efficient is 0.16667.

5. If the reflection coefficient of a transmission line is 0.4, then the standing wave ratio is:
A. 1.3333
B. 2.3333
C. 0.4
D. 0.6
Answer: B
Clarification: SWR= (1+┌)/ (1-┌). Where ┌ is the reflection co-efficient. Substituting for the reflection co-efficient in the equation, SWR is 2.3333.

6. Expression for ϴ means phase angle of the reflection co efficient r=|r|-e^jθ, the phase of the reflection co-efficient is:
A. θ=2π+2βLmin
B. θ=π+2βLmin
C. θ=π/2+2βLmin
D. θ=π+βLmin
Answer: B
Clarification: here, θ is the phase of the reflection co-efficient. Lmin is the distance from the load to the first minimum. Since voltage minima repeat every λ/2, any multiple of λ/2 can be added to Lmin .

7. In the expression for phase of the reflection coefficient, Lmin stands for :
A. distance between load and first voltage minimum
B. distance between load and first voltage maximum
C. distance between consecutive minimas
D. distance between a minima and immediate maxima
Answer: A
Clarification: Lmin is defined as the distance between the terminating load of a transmission line and the first voltage minimum that occurs in the transmission line due to reflection of waves from the load end due to mismatched termination.

8. If SWR=1.5 with a wavelength of 4 cm and the distance between load and first minima is 1.48cm, then the reflection coefficient is:
A. 0.0126+j0.1996
B. 0.0128
C. 0.26+j0.16
D. none of the mentioned
Answer: A
Clarification: ┌= (SWR-1)/ (SWR+1). Substituting for SWR in the above equation for reflection co-efficient, magnitude of the reflection co-efficient is 0.2. To find θ, θ=π+2βLmin, substituting Lmin as 1.48cm, θ=86.4⁰. Hence converting the polar form of the reflection co-efficient into rectangular co-ordinates, reflection co-efficient is 0.0126+j0.1996.

9. If the characteristic impedance of a transmission line 50 Ω and reflection coefficient is 0.0126+j0.1996, then load impedance is:
A. 47.3+j19.7Ω
B. 4.7+j1.97Ω
C. 0.26+j0.16
D. data insufficient
Answer: a
Clarification: ZL=Z0 (1+┌)/ (1-┌). Substituting the given values of reflection co-efficient and characteristic impedance, ZL is 47.3+j19.7Ω .

10. If the normalized load impedance of a transmission line is 2, then the reflection co-efficient is:
A. 0.33334
B. 1.33334
C. 0
D. 1
Answer: A
Clarification: ZL=Z0 (1+┌)/ (1-┌), this is the expression for load impedance. Normalized load impedance is the ratio of load impedance to the characteristic impedance, taking ZLL/Z0 as 2, the reflection co-efficient is equal to 0.33334.


250+ TOP MCQs on Wilkinson Power Dividers and Answers

Microwave Engineering Multiple Choice Questions on “Wilkinson Power Dividers”.

1. A major disadvantage of the lossless T-junction power divider is:
A. Not matched at all the ports
B. Low power output
C. Complex construction
D. None of the mentioned
Answer: A
Clarification: A T-junction hybrid cannot be matched at all the ports if the power divider is lossless. It can be matched only at 2 ports. This is one of the major disadvantages when they are to be used along with other microwave devices.

2. The Wilkinson power divider is a:
A. 2 port network
B. 3 port network
C. 4 port network
D. None of the mentioned
Answer: B
Clarification: Wilkinson power divider is a 3 port network; if it is used as a divider it has one input port and 2 output ports. If it is used as coupler, it has two input port and one output port.

3. Wilkinson power divider is an equal split power divider.
A. True
B. False
Answer: B
Clarification: Wilkinson power divider can be used to divide power in any ratio, but the most commonly used configuration is the equal split power divider.

4. If 10 watt is applied to the input port of a standard Wilkinson divider, then the sum of the power measured at the two output ports of the Wilkinson coupler is
A. 5 watt
B. 10 watt
C. 7.07 watt
D. 8 watt
Answer: C
Clarification: For a standard Wilkinson coupler, the output power is 3 dB less than the total input power in decibels. That is, 70.7% of the total input power is delivered to the output port.

5. The analysis of Wilkinson coupler is done using:
A. Even-odd mode analysis
B. Symmetry
C. S matrix approach
D. None of the mentioned
Answer: A
Clarification: Even-odd mode analysis is one of the simplest methods of analysis for Wilkinson coupler. This involves normalizing all impedances with the characteristic impedance of the transmission line used and carrying out some analysis.

6. A Wilkinson coupler designed can be operated at any frequency.
A. True
B. False
Answer: B
Clarification: The length of the branches of a Wilkinson coupler is all wavelengths dependent and hence Wilkinson coupler designed to operate at one frequency cannot be used to operate at another frequency.

7. For an equal-split Wilkinson power divider of 50Ω system impedance, the characteristic impedance of quarter wave transmission line used is:
A. 70.7 Ω
B. 50 Ω
C. 100 Ω
D. None of the mentioned
Answer: A
Clarification: The characteristic impedance of a Z Ω system is given by √2*Z. hence, the characteristic impedance of 50Ω system is 70.7 Ω.

8. The plot of frequency v/s S11 parameter of a Wilkinson coupler has a dip at the frequency at which it is designed to operate.
A. True
B. False
Answer: A
Clarification: S11 parameter signifies the fraction of the power reflected back to port 1 when power is applied to port 1 of the coupler. Since the ports are matched at the frequency of design S11 is minimum and the curve has a dip.

9. The plot of S23 v/s frequency has the same curve as that of S11 v/s frequency.
A. True
B. False
Answer: A
Clarification: When input is applied to port 1, output is measured at port 2 and port 3. S23 signifies the output at port 3 due to port 2 when input is applied at port 1. This parameter is minimum at the designed frequency.

10. S12 curve of a Wilkinson coupler when plotted versus frequency is a line passing through origin.
A. True
B. False
Answer: B
Clarification: S12 gives the ratio of power at input port P1 to the power measured at port 2. Since the output power remains constant over a wide range of frequencies for a given input applied. Hence S11 is a curve parallel to X axis.


Microwave Engineering,

250+ TOP MCQs on IMPATT and BARITT Diodes and Answers

Microwave Engineering Multiple Choice Questions on “IMPATT and BARITT Diodes”.

1. The material used to fabricate IMPATT diodes is GaAs since they have the highest efficiency in all aspects.
A. true
B. false
Answer: B
Clarification: IMPATT diodes can be fabricated using silicon, germanium, GaAs or indium phosphide. Out of these materials, GaAs have highest efficiency, low noise and high operating frequencies. But GaAs has a major disadvantage of complex fabrication process and higher cost. So, GaAs are not preferred over silicon and germanium.

2. When a reverse bias voltage exceeding the breakdown voltage is applied to an IMPATT diode, it results in:
A. avalanche multiplication
B. break down of depletion region
C. high reverse saturation current
D. none of the mentioned
Answer: A
Clarification: A reverse bias voltage exceeding the breakdown voltage is applied to an IMPATT diode, a high electric field appears across the n+ p junction. This high field imparts sufficient energy to the holes and also to valence electrons to raise themselves to the conduction band. This results in avalanche multiplication of electron hole pair.

3. To prevent an IMPATT diode from burning, a constant bias source is used to maintain _______ at safe limit.
A. average current
B. average voltage
C. average bias voltage
D. average resistance
Answer: A
Clarification: Avalanche multiplication is a cumulative process resulting in rapid increase of carrier density. To prevent the diode from burning due to this increased carrier density, a constant bias source is used to maintain average current at safe limit.

4. The number of semiconductor layers in IMPATT diode is:
A. two
B. three
C. four
D. none of the mentioned
Answer: C
Clarification: IMPATT diode consists of 4 layers according to the construction. It consists of a p+ region and n+ layers at the two ends. In between these layers, a p type layer and an intrinsic region is sandwiched.

5. The resonant frequency of an IMPATT diode is given by:
A. Vd/2l
B. Vd/l
C. Vd/2πl
D. Vdd/4πl
Answer: A
Clarification: The resonant frequency of an IMPATT diode is given by the expression Vd/2l. Here VD is the carrier drift velocity; L is the length of the intrinsic region in the IMPATT diode.

6. If the length of the intrinsic region in IMPATT diode is 2 µm and the carrier drift velocity are 107 cm/s, then the drift time of the carrier is:
A. 10-11 seconds
B. 2×10-11 seconds
C. 2.5×10-11 seconds
D. none of the mentioned
Answer: B
Clarification: The drift time of the carrier is defined as the ratio of length of the intrinsic region to the carrier drift velocity. Substituting the given values in this relation, the drift time of the carrier is 2×10-11 seconds.

7. If the length of the intrinsic region in IMPATT diode is 2 µm and the carrier drift velocity are 107 cm/s, then the nominal frequency of the diode is:
A. 12 GHz
B. 25 GHz
C. 30 GHz
D. 24 GHz
Answer: B
Clarification: Nominal frequency is defined as the ratio of the carrier drift velocity to twice the length of the intrinsic region. Substituting the given values in the above equation, the nominal frequency is 25 GHz.

8. IMPATT diodes employ impact ionization technique which is a noisy mechanism of generating charge carriers.
A. true
B. false
Answer: A
Clarification: IMPATT devices employ impact ionization techniques which is too noisy. Hence in order to achieve low noise figure, impact ionization is avoided in BARITT diodes. The minority injection is provided by punch through of the intermediate region.

9. An essential requirement for the BARITT diode is that the intermediate drift region be completely filled to cause the punch through to occur.
A. true
B. false
Answer: B
Clarification: An essential requirement for the BARITT diode is that the intermediate drift region be completely filled to cause the punch through to the emitter-base junction without causing avalanche breakdown of the base collector junction.

10. If the RMS peak current in an IMPATT diode is 700 mA and if DC input power is 6 watt, with the load resistance being equal to 2.5 Ω, the efficiency of the diode is:
A. 10.1 %
B. 10.21 %
C. 12 %
D. 15.2 %
Answer: B
Clarification: Efficiency of IMPATT diode is defined as the ratio of output RMS power to the input DC power. Calculating the RMS output power from the given RMS current and substituting in the equation of efficiency, the efficiency is 10.21%.

11. If the critical field in a Gunn diode oscillator is 3.2 KV/cm and effective length is 20 microns, then the critical voltage is:
A. 3.2 V
B. 6.4 V
C. 2.4 V
D. 6.5 V
Answer: B
Clarification: Critical voltage of a Gunn diode oscillator is given by the expression lEc where l is the effective length and Ec is the critical field. Substituting the given values in the above equation, critical voltage is 6.4 volts.


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250+ TOP MCQs on Microwave Oscillators and Answers

Microwave Engineering Multiple Choice Questions on “Microwave Oscillators”.

1. In microwave oscillators, negative resistance transistors and diodes are used in order to generate oscillations in the circuit.
A. True
B. False
Answer: A
Clarification: In microwave oscillator, for a current to flow in the circuit the negative impedance of the device must be matched with positive impedance. This results in current being non-zero and generates oscillation.

2. Any device with negative impedance as its characteristic property can be called:
A. Energy source
B. Energy sink
C. Oscillator
D. None of the mentioned
Answer: A
Clarification: A positive resistance implies energy dissipation while a negative resistance implies an energy source. The negative resistance device used in the microwave oscillator, thus acts as a source. The condition Xin+ XL=0 controls the frequency of oscillation. Xin is the impedance of the negative resistance device.

3. In a microwave oscillator, a load of 50+50j is connected across a negative resistance device of impedance -50-50j. Steady state oscillation is not achieved in the oscillator.
A. True
B. False
Answer: B
Clarification: The condition for steady state oscillation in a microwave oscillator is Zin=-ZL. Since this condition is satisfied in the above case, steady state oscillation is achieved.

4. For achieving steady state oscillation, the condition to be satisfied in terms of reflection coefficients is:
A. Гin=ГL
B. Гin=-ГL
C. Гin=1/ГL
D. None of the mentioned
Answer: C
Clarification: The condition for steady state oscillation to be achieved in terms of reflection coefficient is Гin=1/ГL. Here Гin is the reflection coefficient towards the reflection coefficient device and ГL is the reflection coefficient towards the load.

5. A one port oscillator uses a negative resistance diode having Гin=0.9575+j0.8034 (Z0=50Ω) at its desired frequency point. Then the input impedance of the diode is:
A. -44+j123
B. 50+j100
C. -44+j145
D. None of the mentioned
Answer: A
Clarification: The input impedance of the diode given reflection coefficient and characteristic impedance is Z0 (1+Гin)/ (1-Гin). Substituting in the given equation, the input impedance is -44 +j123 Ω.

6. If the input impedance of a diode used in the microwave oscillator is 45-j23 Ω, then the load impedance is to achieve stable oscillation is:
A. 45-j23 Ω
B. -45+j23 Ω
C. 50 Ω
D. 23-j45 Ω
Answer: B
Clarification: The condition for stabilized oscillation is Zin=-ZL. According to this equation, the load impedance required for stabilized oscillation is – (45-j23) Ω. The load impedance is thus -45+j23 Ω.

7. To achieve stable oscillation, Zin + ZL=0 is the only necessary and sufficient condition to be satisfied by the microwave oscillator.
A. True
B. False
Answer: B
Clarification: The condition Zin + ZL=0 is only a necessary condition for stable oscillation and not sufficient. Stability requires that any perturbation in current or frequency is damped out, allowing the oscillator to return to its original state.

8. In transistor oscillators, the requirement of a negative resistance device is satisfied using a varactor diode.
A. True
B. False
Answer: B
Clarification: In a transistor oscillator, a negative resistance one port network is created by terminating a potentially unstable transistor with impedance designed to drive the device in an unstable region.

9. In transistor oscillators, FET and BJT are used. Instability is achieved by:
A. Giving a negative feedback
B. Giving a positive feedback
C. Using a tank circuit
D. None of the mentioned
Answer: B
Clarification: Oscillators require a device that has high instability. To achieve this condition, transistors are used with a positive feedback to increase instability.

10. In a transistor amplifier, if the input impedance is -84-j1.9 Ω, then the terminating impedance required to create enough instability is:
A. -84-j1.9 Ω
B. 28+j1.9 Ω
C. – (28+j1.9) Ω
D. None of the mentioned
Answer: B
Clarification: Relation between terminating impedance and input impedance is Zs=-Rin/3. Zs is the terminating impedance. Substituting in the given equation, the terminated impedance is 28+j1.9 Ω.


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250+ TOP MCQs on Quarter Wave Transformer and Answers

Microwave Engineering Multiple Choice Questions on “Quarter Wave Transformer”.

1. If a transmission line of characteristic impedance 50 Ω is to be matched to a load of 100Ω, then the characteristic impedance of the ƛ/4 transmission line to be used is:
A. 70.71 Ω
B. 50 Ω
C. 100 Ω
D. 75 Ω
Answer: A
Clarification: When a transmission line is not terminated with a matched load, it leads to losses and reflections. In order to avoid this, a λ/4 transmission line can be used for matching purpose. The characteristic impedance of the λ/4 transmission line is given by Z1=√(ZₒR)L. substituting the given values, we get Z1=70.71 Ω.

2. If a λ/4 transmission line is 100Ω is used to match a transmission line to a load of 100Ω, then the characteristic impedance of the transmission line is:
A. 100 Ω
B. 50 Ω
C. 70.71 Ω
D. 200 Ω
Answer: A
Clarification: When a transmission line is not terminated with a matched load, it leads to losses and reflections. In order to avoid this, a λ/4 transmission line can be used for matching purpose. The characteristic impedance of the λ/4 transmission line is given by Z1=√(ZₒR)L. substituting the given values,
Z0=100 Ω.

3. Expression for the characteristic impedance of a transmission line(λ/4) used for impedance matching is:
A. Z1=√(ZₒR)L
B. Z1=√(Zₒ/R)L
C. Z1=√(Zₒ+R)L
D. None of the mentioned
Answer: A
Clarification: When a transmission line is not terminated with a matched load, it leads to losses and reflections. In order to avoid this, a λ/4 transmission line can be used for matching purpose. Hence the expression used to find the characteristic impedance of the λ/4 transmission line is Z1=√(ZₒR)L.

4. If there is no standing wave on a transmission line, then the value of SWR is:
A. 1
B. 0
C. Infinity
D. Insufficient data
Answer: A
Clarification: When there are no standing waves in the transmission line, the reflection co-efficient is zero and hence input impedance of the transmission line is equal to the characteristic impedance of the line. Hence the relation between SWR and reflection co-efficient yields SWR as 1.

5. When a λ/4 transmission line is used for impedance matching, then which of the following is valid?
A. Standing waves are present on the λ/4 transmission line
B. No standing waves on the λ/4 transmission line
C. Standing waves are not present both on the feed line and the matching λ/4 line
D. Standing waves are present on both the feed line and the matching λ/4 line
Answer: A
Clarification: λ/4 transmission line is used to match the load impedance to the characteristic impedance of the transmission line. Hence, standing waves are present on the λ/4 transmission line, but not on the transmission line since it is matched

6. For a transmission line , if the input impedance of the transmission line is 100Ω with a characteristic impedance of 150Ω, then the magnitude of the reflection co efficient:
A. 0.5
B. 1
C. 0.2
D. 0
Answer: C
Clarification: The expression for reflection co-efficient of a transmission line in terms input and characteristic impedance is (Zin-Zₒ)/(Zin+ Zₒ). Substituting the given values in the above expression, reflection co-efficient is 0.2.

7. If the reflection co-efficient of a transmission line is 0.334 with a characteristic impedance of 50Ω then the input impedance of the transmission line is:
A. 100 Ω
B. 50 Ω
C. 150 Ω
D. None of the mentioned
Answer: A
Clarification: Substituting the given voltage reflection co-efficient and the characteristic impedance of the transmission line in ┌= (Zin-Zₒ)/(Zin+ Zₒ). The input impedance of the transmission line is 100Ω

8. When a transmission line of characteristic impedance(50Ω) zₒ is matched to a load by a λ/4 transmission line of characteristic impedance 100Ω, then the transmission co efficient is:
A. 1.5
B. 0.5
C. 1.333
D. 2
Answer: C
Clarification: When a transmission line is matched to a load by using a λ/4 transmission line, the transmission co-efficient T1 of the line is obtained using the expression 2Z1/ (Z1+Z0). Here Z1 is the characteristic impedance of the λ/4 transmission line and Z1 is the characteristic impedance of the transmission line. Substituting the given values, we get T1=1.3333.

9. If a transmission line of zₒ=50Ω is matched using λ/4 transmission line of z₁=100Ω, then the transmission co efficient T₂ is:
A. 1
B. 0.6667
C. 1.3333
D. 2
Answer: B
Clarification: When a transmission line is matched to a load by using a λ/4 transmission line, the transmission co-efficient T2 of the line is obtained using the expression 2Z0/ (Z1+Z0). Here Z1 is the characteristic impedance of the λ/4 transmission line and Z0 is the characteristic impedance of the transmission line. Substituting the given values, we get T2=0.6667.

10. If the transmission co-efficient T₁ of a transmission line is 1.333 and the characteristic impedance of the λ/4 transmission line used is 100Ω, then the characteristic impedance of the transmission line is:
A. 50Ω
B. 100Ω
C. 70.71Ω
D. None of the mentioned
Answer: A
Clarification: Expression for transmission co-efficient of a transmission line matched using a λ/4 transmission line is 2Z1/ (Z1+Z0). Substituting the known values, the characteristic impedance of the transmission line is 50Ω.


Microwave Engineering,

250+ TOP MCQs on Single Stub Matching and Answers

Microwave Engineering Multiple Choice Questions on “Single Stub Matching”.

1. The major advantage of single stub tuning over other impedance matching techniques is:
A. Lumped elements are avoided
B. It can be fabricated as a part of transmission line media
C. It involves two adjustable parameters
D. All of the mentioned

Answer: D
Clarification: Single stub matching does not involve any lumped elements, it can be fabricated as a part of transmission media and it also involves to adjustable parameters namely length and distance from load giving more flexibility.

2. Shunt stubs are preferred for:
A. Strip and microstrip lines
B. Coplanar waveguides
C. Circular waveguide
D. Circulators

Answer: A
Clarification: Since microstrip and strip lines are simple structures, impedance matching using shunt stubs do not increase the complexity and structure of the transmission line. Hence, shunt stubs are preferred for strip and microstrip lines.

3. The two adjustable parameters in single stub matching are distance‘d’ from the load to the stub position, and _________
A. Susceptance or reactance provided by the stub
B. Length of the stub
C. Distance of the stub from the generator
D. None of the mentioned

Answer: A
Clarification: Reactance or susceptance of the matching stub must be known before it used for matching, since it is the most important parameter for impedance matching between the load and the source.

4. In shunt stub matching, the key parameter used for matching is:
A. Admittance of the line at a point
B. Admittance of the load
C. Impedance of the stub
D. Impedance of the load

Answer: A
Clarification: In shunt stub tuning, the idea is to select d so that the admittance Y, seen looking into the line at distance d from the load is of the form Yₒ+jB. Then the stub susceptance is chosen as –jB, resulting in a matched condition.

5. For series stub matching, the parameter used for matching is:
A. Impedance of the transmission line at a point
B. Voltage at a point on the transmission line
C. Admittance at a point on the transmission line
D. Admittance of the load

Answer: A
Clarification: In series sub matching, the distance‘d’ is selected so that the impedance, Z seen looking into the line at a distance‘d’ from the load is of the form Zₒ+jX. Then the stub reactance is chosen as –jX resulting in a matched condition.

6. For co-axial lines and waveguides, ________ is more preferred.
A. Open circuited stub
B. Short circuited stub
C. Slotted section
D. Co-axial lines cannot be impedance matched

Answer: B
Clarification: For co-axial cables and waveguides, short-circuited stub is usually preferred because the cross-sectional area of such an open-circuited line may be large enough to radiate, in which case the stub is no longer purely reactive.

7. For a load impedance of ZL=60-j80. Design of 2 single-stub shunt tuning networks to match this load to a 50Ω line is to be done. What is the normalized admittance obtained so as to plot it on smith chart?
A. 1+j
B. 0.3+j0.4
C. 0.4+j0.3
D. 0.3-j0.4

Answer: B
Clarification: To impedance match a load to a characteristic impedance of the transmission line, first the load has to be normalized. That is, zL=ZL/Z0. For impedance matching using shunt stubs, admittance is used. Taking the reciprocal of impedance, normalized load admittance is 0.3+j0.4.

8. If the normalized admittance at a point on a transmission line to be matched is 1+j1.47. Then the normalized susceptance of the stub used for shunt stub matching is:
A. 1Ω
B. 1.47 Ω
C. -1.47 Ω
D. -1 Ω

Answer: C
Clarification: When shunt stubs are used for impedance matching between a load and transmission line, the susceptance of the shunt stub must be negative of the line’s susceptance at that point for impedance matching.

9. After impedance matching, if a graph is plot with frequency v/s reflection co-efficient of the transmission line is done, then at the frequency point for which the design is done, which of the following is true?
A. There is a peak at this point of the curve
B. There is a dip at this point of the curve
C. The curve is a straight line
D. Such a plot cannot be obtained

Answer: B
Clarification: Since the plot is frequency v/s reflection co-efficient, after impedance matching the reflection co-efficient will be zero or minimum. Hence, there is a dip at that point of the curve.

10. In series stub matching, if the normalized impedance at a point on the transmission line to be matched is 1+j1.33. Then the reactance of the series stub used for matching is:
A. 1 Ω
B. -1.33 Ω
C. -1 Ω
D. 1.33 Ω

Answer: B
Clarification: The reactance of the series stub is negative of the reactance of the line at the point at which it has to be matched. That is, if the line reactance is inductive, the series stub’s reactance is capacitive.