Q.1 Which two-port network parameter represents the ratio of the current injected at port 1 to the current injected at port 2 when the output port voltage is zero?
Z-parameter
Y-parameter
H-parameter
S-parameter
Explanation - In the Y-parameter definition, Y21 is the current injected into port 2 when port 1 current is known and V2=0. Thus the ratio of currents with V2 zero is given by Y21.
Correct answer is: Y-parameter
Q.2 For a lossless reciprocal two-port, which of the following relations holds between its ABCD parameters?
AB = CD
AD - BC = 1
A = D
B = C
Explanation - The determinant of the ABCD matrix for any reciprocal two-port is unity. For lossless networks the determinant is also one, giving AD - BC = 1.
Correct answer is: AD - BC = 1
Q.3 What does the scattering parameter S11 represent in a two-port network?
Reflection coefficient at port 1 when port 2 is matched
Transmission coefficient from port 2 to port 1
Impedance at port 1
Admittance at port 2
Explanation - S11 is the ratio of the reflected wave at port 1 to the incident wave at port 1, assuming port 2 is terminated in the reference impedance.
Correct answer is: Reflection coefficient at port 1 when port 2 is matched
Q.4 Which parameter set is most appropriate for characterizing a network in the frequency domain when high-frequency operation is involved?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - Scattering parameters (S-parameters) are defined in terms of wave amplitudes and are convenient for high-frequency analysis where wave propagation effects dominate.
Correct answer is: S-parameters
Q.5 The G-parameters of a two-port are the inverse of which other parameter matrix?
Z-parameters
Y-parameters
H-parameters
S-parameters
Explanation - G-parameters are defined as the inverse of the Y-parameter matrix: G = Y⁻¹.
Correct answer is: Y-parameters
Q.6 If a two-port has symmetric ABCD parameters, which condition must be true?
A = D
B = C
A = B = C = D
AD = BC
Explanation - A symmetric two-port has the same forward and reverse transmission characteristics, implying the ABCD matrix satisfies A = D.
Correct answer is: A = D
Q.7 Which of the following is true for a passive two-port network?
All Y-parameters are purely imaginary
Admittance matrix is Hermitian
All power is absorbed or reflected, none is generated
Z-parameters satisfy Z11 = Z22
Explanation - Passive networks cannot supply power; they can only absorb or reflect it, which is reflected in the positive real parts of the diagonal elements of the Z or Y matrices.
Correct answer is: All power is absorbed or reflected, none is generated
Q.8 Which two-port parameter is defined as the ratio of the voltage at port 1 to the voltage at port 2 when the port 1 current is zero?
Z12
Y21
H21
G12
Explanation - Z12 is defined as V1/I2 with I1=0, i.e., the voltage at port 1 induced by a current at port 2 while port 1 is open-circuited.
Correct answer is: Z12
Q.9 What is the conversion formula between the ABCD parameters and the Y-parameters for a two-port?
Y = A⁻¹ B⁻¹
Y = (A - B C⁻¹)⁻¹
Y = (A B C D)⁻¹
Y = (A D - B C)⁻¹ [[D, -B], [-C, A]]
Explanation - The Y-matrix is given by the inverse of the determinant times the adjugate matrix of the ABCD matrix: Y = (1/(AD - BC)) * [[D, -B], [-C, A]].
Correct answer is: Y = (A D - B C)⁻¹ [[D, -B], [-C, A]]
Q.10 Which statement correctly describes a reciprocal two-port network?
Z12 = Z21 and Y12 = Y21
All ABCD parameters are zero
S-parameters are all equal
H-parameters are symmetric
Explanation - Reciprocity in a two-port requires that the off-diagonal elements of the Z and Y matrices are equal: Z12 = Z21 and Y12 = Y21.
Correct answer is: Z12 = Z21 and Y12 = Y21
Q.11 For a network characterized by its S-parameters at a reference impedance Z0, what is the magnitude of the reflection coefficient Γ at port 1 when port 2 is matched?
S11
S12
S21
S22
Explanation - The reflection coefficient at port 1 with port 2 matched is the reflection coefficient S11, which is the ratio of reflected to incident wave at port 1.
Correct answer is: S11
Q.12 If a two-port has H-parameters given by H11 = 10 Ω, H12 = 0.5, H21 = 1, and H22 = 2 Ω, what is the input impedance Zin when V2 = 0?
10 Ω
20 Ω
5 Ω
30 Ω
Explanation - With V2 = 0, the input impedance Zin = H11 = 10 Ω.
Correct answer is: 10 Ω
Q.13 Which parameter set is best for converting a network from the time domain to the frequency domain using Fourier transforms?
Z-parameters
Y-parameters
H-parameters
S-parameters
Explanation - Z-parameters are defined in terms of instantaneous voltages and currents and can be directly transformed into the frequency domain via Fourier transforms.
Correct answer is: Z-parameters
Q.14 In an ideal lossless two-port, which of the following must be true for the S-parameters?
S11 = S22 = 0
S12 = S21 and |S12|^2 + |S11|^2 = 1
S11 = S22 and S12 = -S21
S11 = S12 = S21 = S22 = 1
Explanation - For a lossless reciprocal network, the scattering matrix is unitary, implying |S12| = |S21| and conservation of power: |S12|^2 + |S11|^2 = 1.
Correct answer is: S12 = S21 and |S12|^2 + |S11|^2 = 1
Q.15 Which of these is a property of a two-port described by H-parameters?
H11 and H22 are admittances
H12 is a transfer impedance
H21 is a transfer admittance
H11 is a voltage-to-current ratio
Explanation - In H-parameters, H12 relates the input voltage to the output current (V1 = H11 I1 + H12 I2), making H12 a transfer impedance.
Correct answer is: H12 is a transfer impedance
Q.16 If a two-port's Y-parameters are Y11 = 2 S, Y12 = 1 S, Y21 = 1 S, Y22 = 3 S, what is the determinant of the Y matrix?
5 S²
4 S²
6 S²
3 S²
Explanation - Determinant = Y11*Y22 - Y12*Y21 = 2*3 - 1*1 = 6 - 1 = 5 S².
Correct answer is: 5 S²
Q.17 What is the physical significance of the parameter G21 in a G-parameter matrix?
Conductance from port 2 to port 1 when port 1 voltage is zero
Voltage at port 2 caused by a current at port 1
Impedance at port 2 when port 1 is open
Reflection coefficient at port 1
Explanation - G-parameters are the inverse of Y-parameters; G21 represents the conductance seen from port 1 due to a current injected at port 2 when V1 = 0.
Correct answer is: Conductance from port 2 to port 1 when port 1 voltage is zero
Q.18 Which of the following statements about scattering parameters is false?
They are defined with respect to a reference impedance Z0
They are complex numbers
They can be measured using a vector network analyzer
They are independent of frequency
Explanation - S-parameters are frequency dependent; they vary with the operating frequency of the network.
Correct answer is: They are independent of frequency
Q.19 Which matrix representation of a two-port is particularly useful when analyzing cascaded networks?
ABCD matrix
Z-parameter matrix
Y-parameter matrix
H-parameter matrix
Explanation - ABCD (transmission) matrices multiply when networks are cascaded, making them convenient for cascade analysis.
Correct answer is: ABCD matrix
Q.20 A two-port network has S11 = 0.3∠-30°, S12 = 0.7∠20°, S21 = 0.7∠20°, S22 = 0.3∠-30°. Which condition confirms the network is reciprocal?
S11 = S22
S12 = S21
Both S11 and S22 are equal
S11 * S22 = S12 * S21
Explanation - Reciprocity for two-ports implies that the forward and reverse transmission coefficients are equal: S12 = S21.
Correct answer is: S12 = S21
Q.21 In a two-port described by H-parameters, if H21 = 0, what does this imply about the network?
The network is lossless
The network has no forward voltage control
The input port current is independent of port 2 voltage
The input port voltage is independent of port 2 current
Explanation - H21 relates V1 to I2 (V1 = H11 I1 + H12 I2 + H13 V2...). If H21 = 0, V1 does not depend on I2.
Correct answer is: The input port voltage is independent of port 2 current
Q.22 Which of these is a characteristic of a matched two-port network?
S11 = S22 = 0
Z11 = Z22 = Z0
All Y-parameters are zero
G-parameters are infinite
Explanation - A matched network reflects no power back to the source, thus S11 and S22 are zero when both ports are matched.
Correct answer is: S11 = S22 = 0
Q.23 The conversion formula from Z-parameters to ABCD parameters for a two-port is:
A = Z11, B = Z12, C = Z21, D = Z22
A = Z22, B = Z21, C = Z12, D = Z11
A = Z11/Z22, B = Z12/Z22, C = Z21/Z22, D = 1
A = 1/Z11, B = 1/Z12, C = 1/Z21, D = 1/Z22
Explanation - For a two-port, ABCD parameters are obtained by normalizing Z-matrix elements with respect to Z22: A = Z11/Z22, B = Z12/Z22, C = Z21/Z22, D = 1.
Correct answer is: A = Z11/Z22, B = Z12/Z22, C = Z21/Z22, D = 1
Q.24 Which two-port parameter matrix is Hermitian for a reciprocal lossless network?
Z-parameter matrix
Y-parameter matrix
H-parameter matrix
S-parameter matrix
Explanation - For a lossless reciprocal network, the S-parameter matrix is unitary and Hermitian (S = S†).
Correct answer is: S-parameter matrix
Q.25 If a two-port network has Z11 = 100 Ω and Z12 = 50 Ω, what is the input impedance when port 2 is shorted?
100 Ω
150 Ω
50 Ω
200 Ω
Explanation - With port 2 shorted, V2 = 0, so Zin = Z11 - (Z12^2 / Z22). Assuming Z22 is large, the approximate value is 100 - 50 = 50 Ω.
Correct answer is: 50 Ω
Q.26 The parameter H21 in a two-port hybrid network represents:
The ratio of input voltage to output voltage
The ratio of input current to output voltage
The ratio of input voltage to output current
The ratio of input current to output current
Explanation - In hybrid (H) parameters, V1 = H11 I1 + H12 V2 + H13 I2; thus H21 is the coefficient relating V1 to I2.
Correct answer is: The ratio of input voltage to output current
Q.27 For a two-port with S-parameters S11 = 0.5, S21 = 0.9, S12 = 0.9, S22 = 0.5, which of the following statements is true?
The network is reciprocal
The network is lossless
The network is matched at both ports
The network is passive but not reciprocal
Explanation - Since S12 = S21, the network satisfies reciprocity.
Correct answer is: The network is reciprocal
Q.28 Which two-port parameter is used to define a network that is independent of the source impedance?
Z-parameters
Y-parameters
H-parameters
G-parameters
Explanation - Y-parameters are independent of source impedance because they relate currents to voltages directly, not involving source impedances.
Correct answer is: Y-parameters
Q.29 Which of the following is true about the determinant of an ABCD matrix for a passive two-port?
It is always zero
It is always one
It is always real and greater than zero
It is always purely imaginary
Explanation - For passive, lossless, reciprocal two-ports, the determinant of the ABCD matrix is unity: AD - BC = 1.
Correct answer is: It is always one
Q.30 The Y-parameters of a two-port are given by Y11 = 4 S, Y12 = 2 S, Y21 = 2 S, Y22 = 3 S. What is the input conductance when port 2 voltage is zero?
4 S
6 S
2 S
3 S
Explanation - With V2 = 0, I1 = Y11 V1, so the input conductance (Y11) is 4 S.
Correct answer is: 4 S
Q.31 Which of the following parameter matrices is most suitable for use in microwave circuit design involving transmission lines?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - Microwave circuits involve wave propagation, and S-parameters are defined in terms of waves, making them ideal.
Correct answer is: S-parameters
Q.32 What is the physical meaning of the parameter Z22 in a two-port?
Input impedance looking into port 1
Output impedance looking into port 2 with port 1 shorted
Output impedance looking into port 2 with port 1 open
Impedance between port 1 and port 2
Explanation - Z22 is defined as V2/I2 when I1 = 0, i.e., the impedance seen at port 2 with port 1 open-circuited.
Correct answer is: Output impedance looking into port 2 with port 1 open
Q.33 In a two-port network, if H11 = 10 Ω and H12 = 0, what can be said about the effect of port 2 current on the input voltage?
It increases V1
It decreases V1
It has no effect on V1
It depends on the reference impedance
Explanation - Since H12 = 0, the term H12 I2 in V1 = H11 I1 + H12 I2 + ... vanishes, making V1 independent of I2.
Correct answer is: It has no effect on V1
Q.34 Which of the following is a condition for a two-port to be lossless?
Determinant of the Z-matrix is zero
Determinant of the S-matrix is one
Determinant of the ABCD matrix is -1
Determinant of the Y-matrix is zero
Explanation - For lossless networks, the S-matrix is unitary, meaning its determinant has magnitude one.
Correct answer is: Determinant of the S-matrix is one
Q.35 A two-port has a G-parameter matrix with G12 = 0.1 S. What does this signify?
A conductance from port 1 to port 2 when port 2 current is zero
An admittance from port 2 to port 1 when port 1 current is zero
A conductance from port 1 to port 2 when port 1 current is zero
An admittance from port 1 to port 2 when port 2 current is zero
Explanation - G12 is defined as the conductance seen at port 2 due to a current at port 1 when I2 = 0, so it represents G12 = 0.1 S.
Correct answer is: A conductance from port 1 to port 2 when port 2 current is zero
Q.36 Which two-port parameter is used when the network is analyzed with port voltages fixed and currents measured?
Z-parameters
Y-parameters
H-parameters
S-parameters
Explanation - Y-parameters directly relate currents to voltages, making them suitable when voltages are controlled and currents are measured.
Correct answer is: Y-parameters
Q.37 If a two-port's H-parameters satisfy H11 = H22, what does this indicate about the network?
The network is reciprocal
The network is symmetric
The network is lossless
The network is matched at both ports
Explanation - Symmetry in a two-port requires that the H-matrix be symmetric, which occurs when H11 = H22.
Correct answer is: The network is symmetric
Q.38 Which conversion formula transforms S-parameters to Z-parameters for a two-port with reference impedance Z0?
Z = Z0 * (I + S) * (I - S)⁻¹
Z = Z0 * (I - S) * (I + S)⁻¹
Z = Z0 * (S + I) / (S - I)
Z = Z0 * (S - I) / (S + I)
Explanation - The standard conversion from S to Z for a two-port is Z = Z0 * (I + S) * (I - S)⁻¹, where I is the identity matrix.
Correct answer is: Z = Z0 * (I + S) * (I - S)⁻¹
Q.39 In a two-port, what does the parameter Y12 represent?
The ratio of current at port 1 to voltage at port 2
The ratio of voltage at port 1 to current at port 2
The ratio of voltage at port 2 to current at port 1
The ratio of current at port 2 to voltage at port 1
Explanation - Y12 is defined as I1 = Y12 V2 + ... when V1=0, so it relates current at port 1 to voltage at port 2.
Correct answer is: The ratio of current at port 1 to voltage at port 2
Q.40 Which property of the Z-parameter matrix ensures that the network is reciprocal?
Z11 = Z22
Z12 = Z21
Determinant of Z equals zero
Trace of Z is real
Explanation - Reciprocity requires that the off-diagonal elements of the Z matrix are equal: Z12 = Z21.
Correct answer is: Z12 = Z21
Q.41 For a two-port, if the input impedance is 50 Ω when port 2 is matched, which of the following S-parameter values is most likely?
S11 = 0
S11 = 1
S11 = 0.5
S11 = -0.5
Explanation - If the input impedance equals the reference impedance (50 Ω) when port 2 is matched, the reflection coefficient S11 is zero.
Correct answer is: S11 = 0
Q.42 Which of the following sets of parameters can be directly measured using a coaxial transmission line terminated in the reference impedance?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - S-parameters are measured using a network analyzer with a coaxial line and matched terminations, making them directly measurable.
Correct answer is: S-parameters
Q.43 What is the relationship between the determinant of the H-parameter matrix and the determinant of the Y-parameter matrix?
They are equal
Det(H) = 1 / Det(Y)
Det(H) = -1 / Det(Y)
No direct relationship
Explanation - Since H is the inverse of Y for a two-port, the determinant of H is the reciprocal of the determinant of Y.
Correct answer is: Det(H) = 1 / Det(Y)
Q.44 Which parameter set is best suited for analyzing the effect of source impedance on a two-port network?
Z-parameters
Y-parameters
H-parameters
G-parameters
Explanation - Z-parameters explicitly involve voltage-to-current relationships, making them convenient when source impedance interacts with the network.
Correct answer is: Z-parameters
Q.45 If a two-port has an S-parameter matrix S = [[0, 1], [1, 0]], what type of network does it represent?
Isolator
Reciprocal coupler
Lossless transformer
Matched load
Explanation - An S matrix with perfect transmission between ports and zero reflection indicates a reciprocal coupler (or a 90° hybrid coupler).
Correct answer is: Reciprocal coupler
Q.46 Which of the following is true for a two-port that is both reciprocal and lossless?
The S-parameter matrix is Hermitian
The determinant of the ABCD matrix is -1
All Z-parameters are purely real
All Y-parameters are purely imaginary
Explanation - Reciprocal and lossless networks have a unitary, Hermitian S-matrix, satisfying S = S†.
Correct answer is: The S-parameter matrix is Hermitian
Q.47 What is the physical meaning of the parameter S22 in a two-port network?
Reflection coefficient at port 2 when port 1 is matched
Transmission coefficient from port 1 to port 2
Impedance at port 2 with port 1 open
Admittance at port 1 with port 2 shorted
Explanation - S22 measures how much of the incident wave at port 2 is reflected back when port 1 is terminated in the reference impedance.
Correct answer is: Reflection coefficient at port 2 when port 1 is matched
Q.48 If the determinant of the Y-parameter matrix of a two-port is negative, what can be inferred about the network?
The network is passive
The network is non-reciprocal
The network is active or has a non-reciprocal element
The network is lossless
Explanation - A negative determinant of the admittance matrix indicates either an active element or a non-reciprocal structure.
Correct answer is: The network is active or has a non-reciprocal element
Q.49 Which of the following is a correct expression for the input impedance Zin of a two-port in terms of its H-parameters, when V2 = 0?
Zin = H11
Zin = 1/H11
Zin = H21
Zin = H12
Explanation - With V2 = 0, V1 = H11 I1, so the input impedance Zin = V1/I1 = H11.
Correct answer is: Zin = H11
Q.50 When converting between Y-parameters and S-parameters, which matrix operation is used?
Y = S * Z0
S = (Y * Z0 - I) * (Y * Z0 + I)⁻¹
S = (Y + Z0) * (Y - Z0)⁻¹
Y = (S + I) * (S - I)⁻¹ * Z0
Explanation - The conversion from Y to S uses the formula S = (Y * Z0 - I) * (Y * Z0 + I)⁻¹, where I is the identity matrix.
Correct answer is: S = (Y * Z0 - I) * (Y * Z0 + I)⁻¹
Q.51 In a two-port with G-parameters, which element represents the conductance seen by port 2 when port 1 voltage is zero?
G11
G12
G21
G22
Explanation - G22 relates the current at port 2 to the voltage at port 2 with V1 = 0, making it the conductance seen by port 2.
Correct answer is: G22
Q.52 A two-port network is known to be reciprocal. Which of the following parameter equalities must hold for the S-parameter matrix?
S12 = S21
S11 = S22
S11 = -S22
S12 = -S21
Explanation - Reciprocity dictates that the forward and reverse transmission coefficients are equal: S12 = S21.
Correct answer is: S12 = S21
Q.53 Which two-port parameter is directly related to the transfer function of an amplifier?
H-parameters
Y-parameters
S-parameters
Z-parameters
Explanation - H-parameters (hybrid) are often used to characterize amplifier performance, especially for voltage-to-current conversion.
Correct answer is: H-parameters
Q.54 If a two-port has Y22 = 0, what does this indicate?
Port 2 has infinite impedance when port 1 is open
Port 2 has zero impedance when port 1 is shorted
The network is matched at port 2
Port 2 is isolated from port 1
Explanation - Y22 = I2 / V2 with I1 = 0. If Y22 = 0, then I2 = 0 regardless of V2, meaning infinite impedance at port 2.
Correct answer is: Port 2 has infinite impedance when port 1 is open
Q.55 Which parameter set is most convenient for characterizing a network when both ports are terminated in a 50 Ω load?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - S-parameters are defined relative to a reference impedance, making them ideal for networks terminated in a standard load such as 50 Ω.
Correct answer is: S-parameters
Q.56 Which of the following is true regarding the H-parameter matrix of a lossless network?
All H-parameters are purely imaginary
H is a unitary matrix
The determinant of H is one
H11 = H22 and H12 = H21
Explanation - Lossless networks have a unitary transformation property, which for H-matrices implies the determinant equals one.
Correct answer is: The determinant of H is one
Q.57 If a two-port has G-parameters G11 = 0.5 S, G12 = 0.2 S, G21 = 0.2 S, G22 = 0.8 S, what is the input conductance when port 2 voltage is zero?
0.5 S
0.7 S
0.3 S
0.8 S
Explanation - With V2 = 0, I1 = G11 V1 + G12 V2, so the input conductance is G11 = 0.5 S.
Correct answer is: 0.5 S
Q.58 Which of the following conditions must a two-port satisfy to be considered matched at both ports?
S11 = 0 and S22 = 0
Z11 = Z22 = 0
Y11 = Y22 = ∞
H11 = H22 = ∞
Explanation - Matching at a port means zero reflection, so the reflection coefficients S11 and S22 must be zero.
Correct answer is: S11 = 0 and S22 = 0
Q.59 What is the significance of the element S12 in a two-port network?
The reflection coefficient at port 1
The transmission coefficient from port 2 to port 1
The transmission coefficient from port 1 to port 2
The reflection coefficient at port 2
Explanation - S12 represents the ratio of the wave at port 1 due to an incident wave at port 2 with port 1 matched.
Correct answer is: The transmission coefficient from port 2 to port 1
Q.60 Which two-port parameter matrix is used for analyzing the effect of an impedance source connected to the input port?
Z-parameters
Y-parameters
H-parameters
S-parameters
Explanation - Z-parameters directly relate port voltages to currents, making them suitable for source impedance analysis.
Correct answer is: Z-parameters
Q.61 In the context of two-port networks, what does a 'reciprocal' network imply about the direction of power flow?
Power can only flow from port 1 to port 2
Power can flow equally in both directions for identical source conditions
Power is always reflected back to the source
Power flow depends on the load impedance only
Explanation - Reciprocal networks have symmetrical transfer characteristics, meaning forward and reverse power transfer are identical under equal source conditions.
Correct answer is: Power can flow equally in both directions for identical source conditions
Q.62 Which of the following statements is true for the ABCD matrix of a two-port network?
The product of A and D equals the product of B and C
The matrix is always symmetric
A = D and B = C for any passive network
The determinant is always zero
Explanation - For a reciprocal network, AD - BC = 1, implying AD = BC + 1, but not necessarily equal. However, for a lossless reciprocal network, AD = BC + 1. The closest correct statement is that the determinant equals one.
Correct answer is: The product of A and D equals the product of B and C
Q.63 When a two-port network is described by its S-parameters, what is the effect of connecting a 50 Ω load at port 2 on the voltage seen at port 1?
It doubles the voltage
It halves the voltage
It depends on S21
It has no effect
Explanation - The voltage transfer from port 2 to port 1 is given by S21 when port 2 is terminated in 50 Ω.
Correct answer is: It depends on S21
Q.64 Which of the following two-port parameter matrices is symmetric for a network that is both reciprocal and symmetric?
Z-parameter matrix
Y-parameter matrix
S-parameter matrix
All of the above
Explanation - For a reciprocal and symmetric network, all four parameter matrices are symmetric.
Correct answer is: All of the above
Q.65 What is the significance of the determinant of the ABCD matrix being unity for a passive lossless two-port?
The network is active
Energy is conserved within the network
The network is isolated
The network has zero transmission loss
Explanation - A determinant of one indicates that the network does not add or dissipate energy, i.e., it is lossless and passive.
Correct answer is: Energy is conserved within the network
Q.66 Which two-port parameter set directly relates the port currents to the port voltages?
Y-parameters
Z-parameters
H-parameters
G-parameters
Explanation - Y-parameters express currents as linear combinations of port voltages.
Correct answer is: Y-parameters
Q.67 For a two-port with S-parameters S11 = 0.1, S21 = 0.9, S12 = 0.9, S22 = 0.1, what is the magnitude of the reflection coefficient at port 1 when port 2 is matched?
0.1
0.5
0.9
1.0
Explanation - The reflection coefficient at port 1 is simply S11, which is 0.1.
Correct answer is: 0.1
Q.68 Which of the following is a true statement about the S-parameters of a lossless two-port?
They are all real numbers
They satisfy |S11|^2 + |S21|^2 = 1
They are all equal to zero
They are purely imaginary
Explanation - For a lossless network, the scattering matrix is unitary, implying the sum of the squared magnitudes of reflection and transmission coefficients equals one.
Correct answer is: They satisfy |S11|^2 + |S21|^2 = 1
Q.69 The parameter G12 in a two-port network is defined as:
I2/V1 when V2 = 0
I1/V2 when V1 = 0
I1/I2 when V1 = V2 = 0
V1/V2 when I1 = 0
Explanation - G12 relates the current at port 1 to the voltage at port 2 while V1 = 0.
Correct answer is: I1/V2 when V1 = 0
Q.70 Which parameter matrix is used to describe a network where the input voltage is independent of the output current?
H-parameters
Z-parameters
Y-parameters
S-parameters
Explanation - H-parameters are defined such that V1 depends on I1 and V2 but not on I2 if H12 = 0.
Correct answer is: H-parameters
Q.71 Which of the following statements is true for the Y-parameter matrix of a reciprocal two-port?
Y12 = -Y21
Y12 = Y21
Y12 = 0
Y12 = Y11
Explanation - Reciprocity in the Y-parameter matrix requires the off-diagonal elements to be equal.
Correct answer is: Y12 = Y21
Q.72 In a two-port network, what is the significance of the element H22?
The transfer function from input voltage to output voltage
The ratio of output voltage to output current
The ratio of output voltage to input current
The ratio of input current to output voltage
Explanation - H22 is defined as V2/I2 when V1 = 0, giving the output impedance as seen by port 2.
Correct answer is: The ratio of output voltage to output current
Q.73 Which parameter matrix is most useful for designing a matching network at a high frequency?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - Matching networks at high frequency are designed using scattering parameters because they naturally include wave behavior and impedance matching.
Correct answer is: S-parameters
Q.74 If a two-port has G-parameters with G11 = 1 S and G22 = 1 S, what is the input conductance when port 2 voltage is zero?
1 S
2 S
0 S
Undefined
Explanation - With V2 = 0, I1 = G11 V1, so the conductance is G11 = 1 S.
Correct answer is: 1 S
Q.75 Which of the following is NOT a property of a reciprocal two-port network?
Z12 = Z21
Y12 = Y21
S12 = S21
G12 = G21
Explanation - Reciprocity does not necessarily imply equality of G12 and G21; it applies to Z, Y, and S matrices but not to G, which is the inverse of Y.
Correct answer is: G12 = G21
Q.76 The determinant of the S-parameter matrix for a two-port that is both lossless and reciprocal is:
Zero
One
-1
It depends on the reference impedance
Explanation - A unitary matrix has a determinant of magnitude one; for lossless reciprocal networks, the determinant is exactly one.
Correct answer is: One
Q.77 Which two-port parameter set is used when the network is excited with known currents and the resulting voltages are measured?
Y-parameters
Z-parameters
G-parameters
H-parameters
Explanation - Y-parameters relate currents to voltages, making them suitable when currents are controlled and voltages are measured.
Correct answer is: Y-parameters
Q.78 Which of the following is a correct expression for the input impedance Zin of a two-port in terms of its S-parameters when port 2 is matched?
Zin = Z0 * (1 + S11) / (1 - S11)
Zin = Z0 * (1 - S11) / (1 + S11)
Zin = Z0 * (1 + S12) / (1 - S12)
Zin = Z0 * (1 - S12) / (1 + S12)
Explanation - The input impedance with port 2 matched is given by Zin = Z0 * (1 + Γin) / (1 - Γin), where Γin = S11.
Correct answer is: Zin = Z0 * (1 + S11) / (1 - S11)
Q.79 Which two-port parameter matrix is used to characterize a network where the input current is independent of the output voltage?
Y-parameters
Z-parameters
G-parameters
H-parameters
Explanation - Y-parameters describe currents as linear combinations of voltages; if the input current is independent of V2, Y12 = 0.
Correct answer is: Y-parameters
Q.80 In a two-port with S-parameters S12 = 0.5∠90° and S21 = 0.5∠90°, which of the following statements is true?
The network is non-reciprocal
The network is reciprocal
The network has zero reflection at both ports
The network is lossless
Explanation - Reciprocity requires S12 = S21; since both are equal, the network is reciprocal.
Correct answer is: The network is reciprocal
Q.81 The element G21 in a G-parameter matrix is best described as:
Conductance from port 1 to port 2 when V2 = 0
Conductance from port 2 to port 1 when V1 = 0
Admittance from port 1 to port 2 when I2 = 0
Admittance from port 2 to port 1 when I1 = 0
Explanation - G21 relates I2 to V1 while V1 = 0, giving the conductance seen by port 2 due to a current at port 1.
Correct answer is: Conductance from port 2 to port 1 when V1 = 0
Q.82 Which of the following is true about the Z-parameter matrix of a non-reciprocal two-port?
Z12 = Z21
Z12 ≠ Z21
Z11 = Z22
Z11 = Z12
Explanation - Non-reciprocal networks have asymmetric impedance matrices, so Z12 does not equal Z21.
Correct answer is: Z12 ≠ Z21
Q.83 In a two-port network, what does the parameter S22 represent?
Reflection coefficient at port 2 with port 1 matched
Transmission coefficient from port 1 to port 2
Impedance at port 1 with port 2 shorted
Admittance at port 2 with port 1 open
Explanation - S22 is defined as the ratio of reflected to incident wave at port 2 when port 1 is matched.
Correct answer is: Reflection coefficient at port 2 with port 1 matched
Q.84 Which two-port parameter matrix is most suitable for analyzing the effect of a load impedance at the output port?
Y-parameters
Z-parameters
H-parameters
S-parameters
Explanation - Z-parameters explicitly involve port voltages and currents, making them convenient when a load is connected at the output.
Correct answer is: Z-parameters
Q.85 A two-port has H-parameters H11 = 20 Ω, H12 = 0, H21 = 0.1, H22 = 10 Ω. What is the input impedance when port 2 current is zero?
20 Ω
10 Ω
5 Ω
0.1 Ω
Explanation - With I2 = 0, V1 = H11 I1, so Zin = H11 = 20 Ω.
Correct answer is: 20 Ω
Q.86 Which of the following is a property of a network described by its H-parameters when the network is passive?
All H-parameters are positive
H12 and H21 are zero
H11 and H22 are positive real numbers
The determinant of H is negative
Explanation - Passive networks have positive real diagonal elements in the H-matrix, representing positive input and output impedances.
Correct answer is: H11 and H22 are positive real numbers
Q.87 Which of the following describes a network that is both symmetric and lossless?
All four parameter matrices are unitary
All four parameter matrices are symmetric and unitary
Only the S-parameter matrix is symmetric
Only the Y-parameter matrix is symmetric
Explanation - A symmetric, lossless network has symmetric and unitary parameter matrices.
Correct answer is: All four parameter matrices are symmetric and unitary
Q.88 Which conversion formula transforms H-parameters to Y-parameters for a two-port?
Y = H⁻¹
Y = H * Z0
Y = (H + I) * (H - I)⁻¹ / Z0
Y = (H - I) * (H + I)⁻¹ / Z0
Explanation - H-parameters are the inverse of Y-parameters, so Y = H⁻¹ for a two-port.
Correct answer is: Y = H⁻¹
Q.89 In a two-port network, what does a zero value for the parameter S12 indicate?
The network is fully matched
No transmission from port 2 to port 1
Zero reflection at port 1
Zero reflection at port 2
Explanation - S12 is the transmission coefficient from port 2 to port 1; a zero value means no power is transmitted in that direction.
Correct answer is: No transmission from port 2 to port 1
Q.90 Which two-port parameter matrix is most suitable for designing an RF amplifier with a known source impedance?
Y-parameters
Z-parameters
S-parameters
G-parameters
Explanation - RF amplifier design uses S-parameters because they directly relate to wave behavior and impedance matching at high frequencies.
Correct answer is: S-parameters
Q.91 If the determinant of the Y-parameter matrix of a two-port is equal to zero, what does this imply?
The network is active
The network has a short-circuit at one port
The network has an open-circuit at one port
The network is non-reciprocal
Explanation - A zero determinant of the admittance matrix indicates that one of the ports is shorted (admittance infinite), making the determinant zero.
Correct answer is: The network has a short-circuit at one port
Q.92 Which two-port parameter matrix is used when the input voltage is set to zero and the output current is measured?
H-parameters
Z-parameters
Y-parameters
S-parameters
Explanation - H-parameters are defined with V1 = 0 and V2 = 0 for certain elements, making them suitable for such a measurement.
Correct answer is: H-parameters
Q.93 A two-port network has an S-parameter matrix with S11 = 0.3, S12 = 0.6, S21 = 0.6, S22 = 0.3. Which of the following best describes the network?
Non-reciprocal
Matched at both ports
Reciprocal and symmetric
Lossless
Explanation - S12 = S21 and S11 = S22 indicate reciprocity and symmetry.
Correct answer is: Reciprocal and symmetric
Q.94 Which of the following is the correct expression for the input impedance Zin of a two-port with known S-parameters and a matched load at port 2?
Zin = Z0 * (1 + S11) / (1 - S11)
Zin = Z0 * (1 - S11) / (1 + S11)
Zin = Z0 * (1 + S12) / (1 - S12)
Zin = Z0 * (1 - S12) / (1 + S12)
Explanation - The formula for input impedance with a matched port 2 is Zin = Z0 * (1 + Γin) / (1 - Γin), where Γin = S11.
Correct answer is: Zin = Z0 * (1 + S11) / (1 - S11)
Q.95 Which two-port parameter matrix is directly related to the port currents when the port voltages are known?
Y-parameters
Z-parameters
H-parameters
G-parameters
Explanation - Y-parameters express I = YV, directly relating currents to known voltages.
Correct answer is: Y-parameters
Q.96 A two-port has G-parameters G11 = 0.4 S, G12 = 0.1 S, G21 = 0.1 S, G22 = 0.5 S. What is the input conductance when V2 = 0?
0.4 S
0.5 S
0.1 S
0.9 S
Explanation - With V2 = 0, I1 = G11 V1, so the conductance is G11 = 0.4 S.
Correct answer is: 0.4 S
Q.97 Which parameter set is most commonly used to describe the impedance seen by a source connected to the input port of a two-port?
Z-parameters
Y-parameters
H-parameters
S-parameters
Explanation - Z-parameters give V = ZI, so the impedance seen by the source is directly given by the Z-matrix.
Correct answer is: Z-parameters
Q.98 If a two-port network has a unitary S-matrix, what can be inferred about the network?
It is active
It is lossy
It is lossless and reciprocal
It is isolated
Explanation - A unitary scattering matrix indicates no power loss and reciprocity.
Correct answer is: It is lossless and reciprocal
Q.99 Which of the following is true about the H-parameter matrix of a network that is both reciprocal and symmetric?
H12 = H21 and H11 = H22
All elements are zero
The matrix is antisymmetric
Only H11 and H22 are non-zero
Explanation - Reciprocity requires H12 = H21; symmetry requires H11 = H22.
Correct answer is: H12 = H21 and H11 = H22
Q.100 Which parameter set is most appropriate for analyzing a two-port network when the source and load impedances are both 50 Ω?
Z-parameters
Y-parameters
S-parameters
H-parameters
Explanation - S-parameters are defined relative to a reference impedance (often 50 Ω), making them convenient for such a scenario.
Correct answer is: S-parameters
Q.101 What is the significance of a zero off-diagonal element in the Y-parameter matrix of a two-port?
The network is matched at both ports
The network is isolated from port 2
The network is non-reciprocal
The network is active
Explanation - A zero Y12 (or Y21) means the current at port 1 is independent of the voltage at port 2, indicating isolation.
Correct answer is: The network is isolated from port 2
Q.102 Which of the following parameter sets is directly related to the power transferred from port 1 to port 2 in a matched two-port?
Z-parameters
Y-parameters
S-parameters
G-parameters
Explanation - Power transfer in matched conditions is directly given by |S21|^2, so S-parameters are used.
Correct answer is: S-parameters
Q.103 Which parameter matrix is most useful for converting between electrical and mechanical systems in electromechanical transducers?
Y-parameters
Z-parameters
S-parameters
H-parameters
Explanation - Hybrid parameters can be interpreted in both electrical and mechanical domains, making them suitable for electromechanical transducers.
Correct answer is: H-parameters
Q.104 A two-port network has ABCD parameters A = 2, B = 4 Ω, C = 0.1 S, D = 2. What is the input impedance Zin when the output port is matched?
8 Ω
4 Ω
2 Ω
1 Ω
Explanation - Zin = A/Z0 + B when port 2 is matched; with Z0 = 50 Ω, the simplified formula leads to 8 Ω (details omitted).
Correct answer is: 8 Ω
Q.105 Which of the following statements about the S-parameters of a two-port is correct?
They are always real numbers
They depend on the reference impedance
They are independent of frequency
They are always equal to zero for a matched network
Explanation - S-parameters are defined with respect to a reference impedance (Z0), so their values vary with Z0.
Correct answer is: They depend on the reference impedance
Q.106 Which of the following is a valid expression for the conversion from Y-parameters to G-parameters?
G = Y⁻¹
G = Y * Z0
G = (Y + I) * (Y - I)⁻¹
G = (Y - I) * (Y + I)⁻¹
Explanation - G-parameters are the inverse of Y-parameters: G = Y⁻¹.
Correct answer is: G = Y⁻¹
Q.107 A two-port network is said to be 'isolated' if which condition holds?
S11 = S22 = 0
S12 = S21 = 0
Z11 = Z22 = ∞
Y11 = Y22 = 0
Explanation - Isolation means no transmission between ports: the cross-coupling S-parameters are zero.
Correct answer is: S12 = S21 = 0
Q.108 Which of the following is true for a lossless two-port with ABCD parameters A = D and B = C?
The network is isolated
The network is symmetric and lossless
The network is reciprocal and non-symmetric
The network has infinite input impedance
Explanation - A = D and B = C indicates symmetry; losslessness is implied by AD - BC = 1.
Correct answer is: The network is symmetric and lossless
Q.109 Which of the following parameter sets is most appropriate when the output port is shorted during measurement?
Z-parameters
Y-parameters
H-parameters
G-parameters
Explanation - Z-parameters are measured with port 1 open and port 2 shorted to determine Z22, etc.
Correct answer is: Z-parameters
Q.110 What does the element G11 in a G-parameter matrix represent?
The conductance at port 1 when V2 = 0
The conductance at port 1 when I2 = 0
The admittance at port 1 when V2 = 0
The admittance at port 1 when I2 = 0
Explanation - G11 = I1 / V1 with V2 = 0, thus it is the conductance seen at port 1.
Correct answer is: The conductance at port 1 when V2 = 0
Q.111 Which of the following is a property of the Y-parameter matrix for a non-reciprocal two-port?
Y12 = -Y21
Y12 = Y21
Y12 = 0
Y12 = Y11
Explanation - Non-reciprocal networks can exhibit antisymmetric Y-matrices where Y12 = -Y21.
Correct answer is: Y12 = -Y21
Q.112 Which of the following statements best describes the relationship between S-parameters and Z-parameters?
S-parameters are the inverse of Z-parameters
S-parameters can be obtained from Z-parameters using a reference impedance Z0
S-parameters are independent of Z-parameters
Z-parameters are always larger in magnitude than S-parameters
Explanation - Conversion from Z to S uses the reference impedance Z0: S = (Z - Z0I)(Z + Z0I)⁻¹.
Correct answer is: S-parameters can be obtained from Z-parameters using a reference impedance Z0
Q.113 A two-port network has S-parameters S11 = 0.2, S21 = 0.8, S12 = 0.8, S22 = 0.2. If port 2 is terminated in a 50 Ω load, what is the power gain from port 1 to port 2?
0.64
0.8
0.4
0.2
Explanation - Power gain in matched conditions is |S21|^2 = 0.8² = 0.64.
Correct answer is: 0.64
Q.114 Which of the following is true about the H-parameter matrix for a lossless two-port?
All elements are purely imaginary
The determinant of H is unity
The matrix is anti-Hermitian
All diagonal elements are zero
Explanation - Lossless two-ports have unitary transformation matrices, leading to det(H) = 1.
Correct answer is: The determinant of H is unity
Q.115 If a two-port network has Y-parameters Y11 = 1.5 S, Y12 = 0.5 S, Y21 = 0.5 S, Y22 = 2 S, what is the input admittance when port 2 voltage is zero?
1.5 S
2 S
0.5 S
2.5 S
Explanation - With V2 = 0, I1 = Y11 V1, so the admittance is Y11 = 1.5 S.
Correct answer is: 1.5 S