Q.1 What is the definition of a two‑port network?
A network with two voltage sources
A network with two independent current sources
A network that can be fully described by two input and two output ports
A network with only two resistors
Explanation - A two‑port network has two pairs of terminals (ports) where power can enter or leave; its behavior is fully captured by its port parameters.
Correct answer is: A network that can be fully described by two input and two output ports
Q.2 Which of the following represents the impedance parameters of a two‑port?
Z11, Z12, Z21, Z22
Y11, Y12, Y21, Y22
S11, S12, S21, S22
H11, H12, H21, H22
Explanation - Impedance parameters (Z‑parameters) are denoted Z11, Z12, Z21, Z22 and relate port voltages to currents via V = Z·I.
Correct answer is: Z11, Z12, Z21, Z22
Q.3 Which relationship correctly expresses V1 in terms of Z‑parameters?
V1 = Z11·I1 + Z12·I2
V1 = Z11·I2 + Z12·I1
V1 = Z21·I1 + Z22·I2
V1 = Z22·I1 + Z21·I2
Explanation - Z‑parameters relate port voltages to currents: V1 = Z11 I1 + Z12 I2, V2 = Z21 I1 + Z22 I2.
Correct answer is: V1 = Z11·I1 + Z12·I2
Q.4 The admittance parameters of a two‑port are called:
Z‑parameters
Y‑parameters
S‑parameters
A‑parameters
Explanation - Admittance parameters, or Y‑parameters, relate port currents to voltages: I = Y·V.
Correct answer is: Y‑parameters
Q.5 Which equation expresses the relationship between Y‑parameters and Z‑parameters?
Y = Z
Y = Z⁻¹
Y = Zᵀ
Y = Z²
Explanation - The admittance matrix is the inverse of the impedance matrix: Y = Z⁻¹.
Correct answer is: Y = Z⁻¹
Q.6 For a reciprocal two‑port, which condition holds true?
Z12 = Z21
Z11 = Z22
Y12 = -Y21
Y11 = Y22
Explanation - Reciprocity means the transmission characteristics are symmetric: Z12 = Z21 or equivalently Y12 = Y21.
Correct answer is: Z12 = Z21
Q.7 A two‑port with Z12 = 0 is called:
Isolated
Matched
Symmetric
Linear
Explanation - If Z12 = 0 the ports are electrically isolated; no current flows from port 1 to port 2 when port 2 is open.
Correct answer is: Isolated
Q.8 The determinant of the ABCD matrix of a cascade network is equal to:
1
0
Det(A) = Det(B)
Det(C) = Det(D)
Explanation - For lossless, reciprocal two‑port networks, the ABCD determinant equals 1.
Correct answer is: 1
Q.9 Which two‑port parameter is commonly used at RF frequencies?
Z‑parameters
S‑parameters
Y‑parameters
H‑parameters
Explanation - At high frequencies, scattering (S) parameters are preferred because they use matched ports and are easier to measure with a VNA.
Correct answer is: S‑parameters
Q.10 The input reflection coefficient Γin for a two‑port with input impedance Zin is:
(Zin - Z0)/(Zin + Z0)
(Z0 - Zin)/(Z0 + Zin)
(Zin + Z0)/(Zin - Z0)
(Z0 + Zin)/(Z0 - Zin)
Explanation - Reflection coefficient is defined as (Zin - Z0)/(Zin + Z0) with Z0 the characteristic impedance of the source line.
Correct answer is: (Zin - Z0)/(Zin + Z0)
Q.11 If a two‑port has symmetric ABCD parameters, which condition is true?
A = D
B = C
A = B
C = D
Explanation - For a reciprocal symmetric network, the ABCD matrix satisfies A = D and B = C.
Correct answer is: A = D
Q.12 The H‑parameters of a two‑port are defined by which equations?
V1 = H11 I1 + H12 V2, I2 = H21 I1 + H22 V2
I1 = H11 V1 + H12 V2, V2 = H21 I1 + H22 I2
V1 = H11 I1 + H12 I2, V2 = H21 I1 + H22 I2
I1 = H11 V1 + H12 I2, I2 = H21 V1 + H22 I2
Explanation - H‑parameters relate port voltage and current on one side to those on the other: V1 = H11 I1 + H12 V2, I2 = H21 I1 + H22 V2.
Correct answer is: V1 = H11 I1 + H12 V2, I2 = H21 I1 + H22 V2
Q.13 Which two‑port parameter set is most suitable for cascade analysis of amplifiers?
Z‑parameters
Y‑parameters
ABCD parameters
S‑parameters
Explanation - ABCD parameters can be cascaded by simple matrix multiplication, making them ideal for series connection of two‑ports.
Correct answer is: ABCD parameters
Q.14 In a two‑port described by Y‑parameters, the input admittance when the output port is shorted is:
Y11
Y21
Y12
Y22
Explanation - Shorting port 2 forces I2 = 0, so Y11 = I1/V1 under that condition.
Correct answer is: Y11
Q.15 The conversion from Z to H parameters involves which intermediate matrix?
The identity matrix
The Y‑parameter matrix
The S‑parameter matrix
The ABCD matrix
Explanation - To convert Z to H parameters, first compute Y = Z⁻¹, then use the H‑parameter equations.
Correct answer is: The Y‑parameter matrix
Q.16 A two‑port with A = 1, B = 0, C = 0, D = 1 is called a:
Short circuit
Open circuit
Identity network
Load network
Explanation - This ABCD matrix is the identity matrix, meaning the two ports are electrically identical and uncoupled.
Correct answer is: Identity network
Q.17 Which two‑port parameter pair is directly related to power gain?
Z‑parameters
S‑parameters
ABCD parameters
Y‑parameters
Explanation - Power gain of a two‑port is often expressed using the forward transmission coefficient S21.
Correct answer is: S‑parameters
Q.18 The condition G12 = G21 for a two‑port is known as:
Reciprocity
Symmetry
Impedance matching
Linearity
Explanation - Reciprocity requires that the admittance matrix is symmetric: G12 = G21.
Correct answer is: Reciprocity
Q.19 Which matrix element of the S‑parameter matrix represents the reverse isolation?
S12
S21
S11
S22
Explanation - S12 describes the signal that travels from port 2 to port 1 when port 1 is excited – the reverse isolation coefficient.
Correct answer is: S12
Q.20 If a two‑port has a reflection coefficient of zero at its input, it is said to be:
Matched
Open
Shorted
Unmatched
Explanation - Zero reflection coefficient indicates the input impedance equals the source impedance – a matched condition.
Correct answer is: Matched
Q.21 The input impedance of a two‑port described by ABCD parameters and terminated with load ZL is:
(A·ZL + B)/(C·ZL + D)
(A + B·ZL)/(C + D·ZL)
(A·ZL - B)/(C·ZL - D)
(A - B·ZL)/(C - D·ZL)
Explanation - The ABCD equations give Zin = (A·ZL + B)/(C·ZL + D).
Correct answer is: (A·ZL + B)/(C·ZL + D)
Q.22 Which parameter set is used to design a quarter‑wave transformer?
S‑parameters
ABCD parameters
Z‑parameters
Y‑parameters
Explanation - ABCD parameters conveniently express the quarter‑wave transformer’s behavior for cascaded sections.
Correct answer is: ABCD parameters
Q.23 The impedance of a shorted transmission line of length L at frequency f is:
0 Ω
∞ Ω
Z0·j tan(βL)
Z0/j tan(βL)
Explanation - A short at the load makes the input impedance zero regardless of line length.
Correct answer is: 0 Ω
Q.24 Which condition must hold for a two‑port to be lossless?
Determinant of Y‑matrix is zero
Determinant of S‑matrix is unity
All parameters are real numbers
Z12 = 0
Explanation - For a lossless two‑port, |S| = 1, meaning the S‑matrix is unitary.
Correct answer is: Determinant of S‑matrix is unity
Q.25 The noise figure of a two‑port amplifier is primarily affected by which parameter?
Z11
S21
S12
S22
Explanation - The gain (S21) and its associated noise factor determine the overall noise figure of the amplifier.
Correct answer is: S21
Q.26 Which equation gives the output impedance of a two‑port with ABCD parameters when the source is shorted?
(D·Zin + C)/(B·Zin + A)
(A·Zin + B)/(C·Zin + D)
(A + B·Zin)/(C + D·Zin)
(A·Zin - B)/(C·Zin - D)
Explanation - When the input is shorted, Zin = 0, leading to Zout = (C)/(A).
Correct answer is: (D·Zin + C)/(B·Zin + A)
Q.27 The parameter H22 of a two‑port represents:
Output resistance with input open
Input resistance with output short
Input conductance with output short
Output conductance with input short
Explanation - H22 is the input resistance seen at port 1 when port 2 is shorted (V2 = 0).
Correct answer is: Input resistance with output short
Q.28 Which transformation is needed to convert S‑parameters to Z‑parameters when the ports are matched to 50 Ω?
Z = Z0 (1+S)/(1-S)
Z = Z0 (1-S)/(1+S)
Z = Z0 (1+S)/(1+S*)
Z = Z0 (1-S*)/(1+S*)
Explanation - The conversion formula for matched ports is Z = Z0 (1+S)/(1−S).
Correct answer is: Z = Z0 (1+S)/(1-S)
Q.29 For a two‑port network with S11 = S22 = 0 and S12 = S21 = 1, the network is:
A lossless matched two‑port
An isolated network
A perfect combiner
A voltage divider
Explanation - Zero reflection (S11=S22=0) and full transmission (S12=S21=1) indicate a perfect isolation and matching.
Correct answer is: An isolated network
Q.30 What does the parameter A in the ABCD matrix represent physically?
Voltage ratio
Current ratio
Voltage gain
Current gain
Explanation - In the ABCD representation, A relates the input voltage to the output voltage: V2 = A·V1 − B·I2.
Correct answer is: Voltage ratio
Q.31 Which two‑port parameter set is best for analyzing the impedance seen at the input of a cascade of amplifiers?
Z‑parameters
Y‑parameters
ABCD parameters
S‑parameters
Explanation - ABCD parameters can be multiplied for cascaded sections, making it easy to compute input impedance of cascades.
Correct answer is: ABCD parameters
Q.32 The reflection coefficient at port 2 when port 1 is terminated in a matched load is:
S22
S12
S21
S11
Explanation - S22 is the return loss at port 2 when port 1 is matched.
Correct answer is: S22
Q.33 For a lossless reciprocal two‑port, the magnitude of the determinant of the S‑matrix is:
0
1
Infinity
Depends on frequency
Explanation - Lossless reciprocal two‑ports have unitary S‑matrices, so |det(S)| = 1.
Correct answer is: 1
Q.34 Which parameter is most suitable for characterizing a filter with high input and output impedances?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - S‑parameters are measured with matched terminations, so they are ideal for high‑impedance networks.
Correct answer is: S‑parameters
Q.35 The input impedance of a two‑port described by Y‑parameters when port 2 is open is:
1/Y11
1/Y12
Y11
Y12
Explanation - With port 2 open (I2=0), the input admittance is Y11, so input impedance is 1/Y11.
Correct answer is: 1/Y11
Q.36 If a two‑port has A = D, B = C, and all parameters are real, the network is:
Reciprocal
Non‑reciprocal
Symmetric
Asymmetric
Explanation - Symmetry requires A = D and B = C (reciprocal networks also satisfy these if they are lossless).
Correct answer is: Symmetric
Q.37 A two‑port with S11 = S22 = 1 and S12 = S21 = 0 is a:
Short circuit
Open circuit
Isolator
Amplifier
Explanation - Reflection coefficient of 1 indicates an open circuit at both ports.
Correct answer is: Open circuit
Q.38 Which formula calculates the return loss (RL) from the reflection coefficient Γ?
RL = 20 log10|Γ|
RL = -20 log10|Γ|
RL = 10 log10|Γ|
RL = -10 log10|Γ|
Explanation - Return loss is defined as RL = −20 log10(|Γ|) dB.
Correct answer is: RL = -20 log10|Γ|
Q.39 In an RF amplifier, the maximum power gain occurs when the input source impedance matches:
The conjugate of the input impedance
The real part of the input impedance
The input impedance itself
Zero ohms
Explanation - Maximum power transfer requires source impedance to be the complex conjugate of the input impedance.
Correct answer is: The conjugate of the input impedance
Q.40 Which element of the Y‑parameter matrix represents the conductance from port 1 to port 2?
Y12
Y21
Y11
Y22
Explanation - Y12 is the admittance seen at port 1 due to a voltage at port 2.
Correct answer is: Y12
Q.41 The condition Z12 = -Z21 is characteristic of:
Symmetric networks
Reciprocal networks
Non‑reciprocal networks
Lossless networks
Explanation - In non‑reciprocal networks, the off‑diagonal impedance elements are negative of each other.
Correct answer is: Non‑reciprocal networks
Q.42 A two‑port with H11 = 0 and H12 = 1 is an example of:
A voltage source
An ideal transformer
An ideal current source
A short circuit
Explanation - H11 = 0 indicates no input voltage drop, H12 = 1 implies perfect voltage coupling.
Correct answer is: An ideal transformer
Q.43 Which parameter set is directly measured by a vector network analyzer?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - A VNA measures scattering parameters because they are defined with matched ports.
Correct answer is: S‑parameters
Q.44 The input voltage gain of a two‑port with ABCD parameters is:
A + B/ZL
A + B·ZL
A + B
A + B/Zin
Explanation - Voltage gain V2/V1 = A + B/ZL when port 2 is terminated with load ZL.
Correct answer is: A + B/ZL
Q.45 The parameter G21 in an H‑parameter matrix is defined as:
Input conductance with output short
Output conductance with input short
Input conductance with output open
Output conductance with input open
Explanation - G21 is the current at port 2 when port 1 is shorted, thus output conductance under shorted input.
Correct answer is: Output conductance with input short
Q.46 For a two‑port, if the input admittance is purely resistive at a given frequency, the network is:
Lossless
Lossy
Non‑reciprocal
Reactive
Explanation - A purely resistive admittance indicates no reactive power and thus a lossless network.
Correct answer is: Lossless
Q.47 The condition S21 = 1 and S12 = 0 describes a:
Lossless isolator
Ideal amplifier
Matched load
Short‑circuit
Explanation - Full forward transmission with zero reverse transmission indicates an isolator.
Correct answer is: Lossless isolator
Q.48 The output impedance of a two‑port with H‑parameters when the input is shorted is:
G22
G12
H22
H12
Explanation - G22 is the output admittance (inverse of impedance) when the input is shorted.
Correct answer is: G22
Q.49 Which transformation is used to convert ABCD parameters to S‑parameters?
Matrix inversion
Complex conjugate
Linear transformation using Z0
Differentiation
Explanation - The conversion uses a standard formula involving the characteristic impedance Z0 and the ABCD matrix.
Correct answer is: Linear transformation using Z0
Q.50 For a two‑port, if A = D = 1 and B = C = 0, the network is:
A perfect transmission line
An open circuit
A short circuit
An identity network
Explanation - The ABCD matrix equals the identity matrix, meaning input equals output without transformation.
Correct answer is: An identity network
Q.51 The input reflection coefficient of a two‑port with Y‑parameters is calculated using:
(Y11 - Y0)/(Y11 + Y0)
(Y0 - Y11)/(Y0 + Y11)
(Y11 + Y0)/(Y11 - Y0)
(Y0 + Y11)/(Y0 - Y11)
Explanation - Reflection coefficient Γin = (Yin - Y0)/(Yin + Y0) where Yin = Y11.
Correct answer is: (Y11 - Y0)/(Y11 + Y0)
Q.52 A two‑port that has a zero input impedance when the output is open is:
Reciprocal
Non‑reciprocal
Symmetric
Shorted network
Explanation - Zero input impedance with output open indicates port 1 is shorted by the two‑port.
Correct answer is: Shorted network
Q.53 In a matched two‑port amplifier, the maximum power gain is:
S21·S12
S21 / S12
S12 / S21
S21 · S11
Explanation - Maximum power gain in matched conditions is the product of forward and reverse gains, S21·S12.
Correct answer is: S21·S12
Q.54 The element G11 in a two‑port's H‑parameter matrix corresponds to:
Input resistance with output open
Output resistance with input short
Input conductance with output open
Output conductance with input short
Explanation - G11 = I1/V1 when port 2 is open, i.e., input conductance.
Correct answer is: Input conductance with output open
Q.55 A two‑port with S11 = 0, S22 = 0, and S12 = 0 is:
A perfect isolator
A perfect matched load
An ideal amplifier
A short‑circuit
Explanation - Zero reflection at both ports with no cross‑coupling indicates matched termination.
Correct answer is: A perfect matched load
Q.56 The impedance seen at port 1 of a two‑port when port 2 is open is:
Z11
Z12
Z21
Z22
Explanation - When port 2 is open (I2=0), V1 = Z11·I1, so the impedance is Z11.
Correct answer is: Z11
Q.57 In an ideal lossless reciprocal two‑port, which S‑parameter is always real?
S11
S12
S21
S22
Explanation - For a lossless reciprocal network, the reflection coefficients S11 and S22 are real numbers.
Correct answer is: S11
Q.58 The condition S12 = S21 in a two‑port indicates:
Reciprocity
Non‑reciprocity
Matching
Losslessness
Explanation - Reciprocity requires symmetric transmission coefficients: S12 = S21.
Correct answer is: Reciprocity
Q.59 Which of the following is NOT a valid two‑port parameter set?
Z‑parameters
Y‑parameters
H‑parameters
P‑parameters
Explanation - P‑parameters are not standard; the accepted sets are Z, Y, H, G, A, S, T, etc.
Correct answer is: P‑parameters
Q.60 The input resistance of a two‑port with Y‑parameters when the output is shorted is:
1/Y11
1/Y12
Y11
Y12
Explanation - Shorting port 2 forces I2=0, so input admittance is Y11 and resistance is 1/Y11.
Correct answer is: 1/Y11
Q.61 Which condition defines a matched two‑port amplifier for maximum gain?
S11 = S22 = 1
S11 = S22 = 0
S11 = S22 = 0 and S12 = S21 = 1
S11 = S22 = 0 and S12 = 0
Explanation - Zero reflections and zero reverse transmission give the best matching for maximum power transfer.
Correct answer is: S11 = S22 = 0 and S12 = 0
Q.62 The parameter B in the ABCD matrix corresponds to:
Voltage gain
Current gain
Voltage ratio with port 2 shorted
Current ratio with port 2 open
Explanation - B relates port 2 current to port 1 voltage: V2 = A V1 - B I2; when port 2 is shorted, B contributes to V2.
Correct answer is: Voltage ratio with port 2 shorted
Q.63 In a two‑port, the condition H21 = 0 indicates:
Input is isolated from output
Output is isolated from input
Both ports are matched
The network is lossless
Explanation - H21 = 0 means no current flows into port 2 when port 1 is driven; output is isolated.
Correct answer is: Output is isolated from input
Q.64 The noise figure of a two‑port amplifier is minimized when:
S11 is maximum
S21 is maximum
Input source impedance equals conjugate of input impedance
All S‑parameters are zero
Explanation - Matching the source to the conjugate of the input impedance reduces mismatch loss and noise figure.
Correct answer is: Input source impedance equals conjugate of input impedance
Q.65 Which equation gives the output power in a two‑port amplifier with S21 and source power Pin?
Pout = |S21|²·Pin
Pout = |S12|²·Pin
Pout = |S11|²·Pin
Pout = |S22|²·Pin
Explanation - The output power is the forward transmission gain squared times the input power.
Correct answer is: Pout = |S21|²·Pin
Q.66 Which two‑port parameter set is best for analyzing a circuit with a known source impedance and load impedance?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - Z‑parameters directly relate voltages to currents, which is useful when dealing with source and load impedances.
Correct answer is: Z‑parameters
Q.67 The determinant of the Y‑parameter matrix for a passive network must be:
Zero
Positive
Negative
Any real number
Explanation - For passive, reciprocal networks the determinant of the Y‑matrix is positive, ensuring stability.
Correct answer is: Positive
Q.68 In an ideal transformer modeled as a two‑port, the relationship between the turns ratio n and the impedance ratio is:
Z2/Z1 = n
Z2/Z1 = n²
Z2/Z1 = 1/n²
Z2/Z1 = 1/n
Explanation - The impedance seen on the secondary side is multiplied by the square of the turns ratio.
Correct answer is: Z2/Z1 = n²
Q.69 A two‑port with S21 = 0.5 and S12 = 0.1 is an example of a:
Low‑loss filter
Isolator
Amplifier
Matched load
Explanation - Forward gain less than unity indicates attenuation; reverse gain also small, typical of a filter.
Correct answer is: Low‑loss filter
Q.70 Which parameter is directly related to the input voltage gain of a two‑port amplifier?
S21
S12
S11
S22
Explanation - S21 represents the forward transmission coefficient, i.e., voltage gain from input to output.
Correct answer is: S21
Q.71 The input admittance of a two‑port described by Y‑parameters when port 2 is shorted is:
Y11
Y12
1/Y11
1/Y12
Explanation - Shorting port 2 sets I2 = 0, so input admittance equals Y11.
Correct answer is: Y11
Q.72 Which condition ensures that a two‑port is power‑conserving?
Determinant of S‑matrix = 0
Determinant of S‑matrix = 1
Determinant of ABCD matrix = 0
Determinant of ABCD matrix = 1
Explanation - Power conservation requires the S‑matrix to be unitary, i.e., |det(S)| = 1.
Correct answer is: Determinant of S‑matrix = 1
Q.73 The parameter G22 in a two‑port H‑parameter matrix is:
Output conductance with input shorted
Input conductance with output shorted
Output resistance with input shorted
Input resistance with output shorted
Explanation - G22 is the current at port 2 when port 1 is shorted, representing output conductance.
Correct answer is: Output conductance with input shorted
Q.74 In a matched two‑port, the maximum output power is obtained when:
The load impedance equals the conjugate of the output impedance
The load impedance equals the input impedance
The load impedance equals the characteristic impedance
All S‑parameters are zero
Explanation - Maximum power transfer requires matching the load to the output impedance (conjugate match).
Correct answer is: The load impedance equals the conjugate of the output impedance
Q.75 The condition A = 1, B = 0, C = 0, D = 1 for an ABCD matrix indicates that the two‑port:
Is a perfect match
Is a lossless network
Is a voltage divider
Is an identity network
Explanation - This is the identity matrix, meaning the network does not alter signals between ports.
Correct answer is: Is an identity network
Q.76 Which parameter set is commonly used for representing a transmission line segment?
Z‑parameters
S‑parameters
ABCD parameters
H‑parameters
Explanation - Transmission lines are naturally described by ABCD parameters (also called transmission or chain parameters).
Correct answer is: ABCD parameters
Q.77 For a two‑port network, the input reflection coefficient Γin is zero when the input impedance equals:
Zero ohms
Infinity ohms
The source impedance Zs
The load impedance ZL
Explanation - Zero reflection occurs when the load seen by the source matches the source impedance.
Correct answer is: The source impedance Zs
Q.78 The S‑parameter S22 is measured by:
Exciting port 2 and measuring port 2
Exciting port 1 and measuring port 1
Exciting port 1 and measuring port 2
Exciting port 2 and measuring port 1
Explanation - S22 is the reflection coefficient at port 2 when it is excited.
Correct answer is: Exciting port 2 and measuring port 2
Q.79 The condition H11 = H22 for a two‑port indicates:
Symmetry
Reciprocity
Losslessness
Matching
Explanation - Symmetry requires H11 = H22 and H12 = H21.
Correct answer is: Symmetry
Q.80 The input impedance of a two‑port with Z‑parameters when port 2 is open is:
Z11
Z12
Z21
Z22
Explanation - With port 2 open (I2=0), V1 = Z11 I1, so the input impedance is Z11.
Correct answer is: Z11
Q.81 Which condition indicates that a two‑port network is non‑reciprocal?
S12 = S21
S11 = S22
S12 ≠ S21
S11 = 0
Explanation - Non‑reciprocal networks have asymmetric transmission coefficients.
Correct answer is: S12 ≠ S21
Q.82 The reflection coefficient at port 1 when the two‑port is terminated in its characteristic impedance Z0 is:
S11
S12
S21
S22
Explanation - S11 is defined as the reflection coefficient at port 1 with matched terminations.
Correct answer is: S11
Q.83 The Y‑parameter Y11 of a two‑port with port 2 open is:
I1/V1
V1/I1
I2/V2
V2/I2
Explanation - Y11 is the admittance seen at port 1 with port 2 open, i.e., I1/V1.
Correct answer is: I1/V1
Q.84 Which transformation is required to obtain S‑parameters from Z‑parameters when Z0 ≠ 50 Ω?
Divide by Z0
Multiply by Z0
Apply the standard Z↔S formula with Z0
No transformation needed
Explanation - The conversion formula uses the characteristic impedance Z0 in the calculation.
Correct answer is: Apply the standard Z↔S formula with Z0
Q.85 The output admittance of a two‑port with H‑parameters when port 1 is shorted is:
G22
G12
H22
H12
Explanation - G22 is the output admittance (inverse of impedance) when the input is shorted.
Correct answer is: G22
Q.86 Which condition defines a matched two‑port in terms of its S‑parameters?
S11 = S22 = 1
S11 = S22 = 0
S12 = S21 = 0
S11 = S22 = 0 and S12 = 0
Explanation - All reflections are zero and no reverse transmission – perfect matching.
Correct answer is: S11 = S22 = 0 and S12 = 0
Q.87 The parameter C in the ABCD matrix represents:
Voltage gain
Current gain
Voltage ratio with port 1 open
Current ratio with port 1 shorted
Explanation - C relates port 2 voltage to port 1 current: V2 = C V1 + D I2; when port 1 is open, C contributes to V2.
Correct answer is: Voltage ratio with port 1 open
Q.88 For a two‑port amplifier, the noise figure is minimized when the input source impedance equals:
The real part of the input impedance
Zero ohms
The characteristic impedance of the line
The conjugate of the input impedance
Explanation - Conjugate matching minimizes mismatch loss and reduces noise figure.
Correct answer is: The conjugate of the input impedance
Q.89 A two‑port with S21 = 2 and S12 = 0 is an example of a:
Non‑reciprocal amplifier
Lossless filter
Isolator
Matched load
Explanation - Forward gain >1 and no reverse gain indicates a non‑reciprocal amplifier.
Correct answer is: Non‑reciprocal amplifier
Q.90 The determinant of the Y‑parameter matrix for a two‑port with passive elements must be:
Negative
Zero
Positive
Any real number
Explanation - The determinant of a passive reciprocal Y‑matrix is always positive.
Correct answer is: Positive
Q.91 The input admittance of a two‑port described by Y‑parameters when port 2 is shorted is:
Y11
Y12
1/Y11
1/Y12
Explanation - Shorting port 2 sets I2=0, so the input admittance equals Y11.
Correct answer is: Y11
Q.92 In a lossless reciprocal two‑port, the following holds:
S11 = S12
S12 = S21
S11 = 0
S22 = 0
Explanation - Reciprocity imposes equality between forward and reverse transmission coefficients.
Correct answer is: S12 = S21
Q.93 The input impedance of a two‑port described by ABCD parameters when port 2 is terminated with a load ZL is:
(A·ZL + B)/(C·ZL + D)
(A + B·ZL)/(C + D·ZL)
(A·ZL - B)/(C·ZL - D)
(A - B·ZL)/(C - D·ZL)
Explanation - The standard ABCD-to‑impedance relationship gives this formula.
Correct answer is: (A·ZL + B)/(C·ZL + D)
Q.94 The parameter G11 in a two‑port's H‑parameter matrix corresponds to:
Input conductance with output short
Input conductance with output open
Output conductance with input short
Output conductance with input open
Explanation - G11 is I1/V1 when port 2 is open, i.e., input conductance.
Correct answer is: Input conductance with output open
Q.95 A two‑port network with S11 = 0, S22 = 0, S12 = 0 and S21 = 1 is a:
Lossless matched load
Ideal transmission line
Perfect isolator
Lossy filter
Explanation - Zero reflections and unit forward transmission represent a lossless matched transmission line.
Correct answer is: Ideal transmission line
Q.96 The input reflection coefficient at port 1 when the two‑port is terminated with its characteristic impedance Z0 is:
S11
S12
S21
S22
Explanation - S11 is defined as the reflection coefficient at port 1 with matched terminations.
Correct answer is: S11
Q.97 The condition A = 1, B = 0, C = 0, D = 1 in an ABCD matrix represents:
A short circuit
An open circuit
An identity network
A lossless network
Explanation - This is the identity matrix; input equals output with no transformation.
Correct answer is: An identity network
Q.98 The element G12 in an H‑parameter matrix is:
Output conductance with input shorted
Input conductance with output shorted
Output resistance with input shorted
Input resistance with output shorted
Explanation - G12 represents the input current generated by a voltage at port 2 when port 1 is shorted.
Correct answer is: Input conductance with output shorted
Q.99 The input impedance of a two‑port network described by Y‑parameters when port 2 is terminated in a short is:
1/Y11
1/Y12
Y11
Y12
Explanation - With port 2 shorted (V2=0), the input admittance is Y11, so the impedance is 1/Y11.
Correct answer is: 1/Y11
Q.100 For a lossless two‑port, the product of the forward and reverse transmission coefficients is:
1
0
Infinity
Depends on frequency
Explanation - Lossless reciprocity gives |S21·S12| = 1 for a two‑port.
Correct answer is: 1
Q.101 The condition S11 = S22 = 0 and S12 = S21 = 0 indicates that the two‑port network is:
An isolated network
A matched load
An ideal amplifier
A short circuit
Explanation - Zero reflections and zero transmission mean the two ports are isolated from each other.
Correct answer is: An isolated network
Q.102 Which parameter set is most appropriate for representing a network that is connected to matched source and load?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - S‑parameters are defined with matched terminations and are ideal for such a configuration.
Correct answer is: S‑parameters
Q.103 The output resistance of a two‑port with H‑parameters when the input is shorted is:
1/H22
1/H12
H22
H12
Explanation - When input is shorted, the output resistance is the reciprocal of the output conductance H22.
Correct answer is: 1/H22
Q.104 In an ideal transformer modeled as a two‑port, the transfer ratio between input and output currents is the inverse of the turns ratio.
True
False
Only for lossless transformers
Only for lossy transformers
Explanation - Current ratio is the inverse of the voltage (turns) ratio in an ideal transformer.
Correct answer is: True
Q.105 The reflection coefficient at port 2 when port 1 is terminated in a matched load is:
S12
S22
S21
S11
Explanation - S22 is measured at port 2 under matched conditions at port 1.
Correct answer is: S22
Q.106 Which two‑port parameter set is used for describing a transmission line section with characteristic impedance Z0 and propagation constant γ?
ABCD parameters
S‑parameters
Y‑parameters
H‑parameters
Explanation - The ABCD matrix of a transmission line depends on Z0 and γ: A=D=cosh(γl), B=Z0 sinh(γl), C= sinh(γl)/Z0.
Correct answer is: ABCD parameters
Q.107 In a matched two‑port amplifier, the input source impedance that maximizes the power delivered to the amplifier is:
The real part of the amplifier's input impedance
Zero ohms
The conjugate of the amplifier's input impedance
The characteristic impedance of the line
Explanation - Maximum power transfer theorem requires the source impedance to be the conjugate of the load impedance.
Correct answer is: The conjugate of the amplifier's input impedance
Q.108 The condition A = D for a two‑port indicates:
Reciprocity
Symmetry
Losslessness
Matching
Explanation - A = D is one of the symmetry conditions in a reciprocal two‑port.
Correct answer is: Symmetry
Q.109 Which element of the S‑parameter matrix represents the transmission coefficient from port 1 to port 2?
S11
S12
S21
S22
Explanation - S21 is the forward transmission coefficient from port 1 to port 2.
Correct answer is: S21
Q.110 The input admittance of a two‑port described by Y‑parameters when port 2 is terminated in a short is:
Y11
Y12
1/Y11
1/Y12
Explanation - Shorting port 2 sets V2=0, so the input admittance is Y11.
Correct answer is: Y11
Q.111 For a two‑port network, the condition S21 = 0.5 and S12 = 0.2 indicates:
A non‑reciprocal amplifier
A lossless filter
An isolator
A matched load
Explanation - Forward and reverse gains are unequal, indicating non‑reciprocal behavior.
Correct answer is: A non‑reciprocal amplifier
Q.112 The output impedance of a two‑port described by ABCD parameters when the input is shorted is:
C/A
A/C
B/D
D/B
Explanation - When the input is shorted (V1=0), the output impedance is Zout = C/A.
Correct answer is: C/A
Q.113 Which parameter set is used for representing a two‑port network that is purely reactive?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - Z‑parameters naturally include reactive elements (imaginary parts).
Correct answer is: Z‑parameters
Q.114 The reflection coefficient Γ at a port is zero when the port is terminated in:
Short circuit
Open circuit
Characteristic impedance of the line
Zero ohms
Explanation - Zero reflection occurs when the load impedance matches the line's characteristic impedance.
Correct answer is: Characteristic impedance of the line
Q.115 The Y‑parameter matrix of a two‑port with Y12 = Y21 and Y11 = Y22 is:
Reciprocal
Non‑reciprocal
Symmetric
Lossless
Explanation - Reciprocal networks have symmetric admittance matrices.
Correct answer is: Reciprocal
Q.116 Which two‑port parameter set is most convenient for calculating the power transfer between ports?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - S‑parameters directly relate to power transfer via |S21|².
Correct answer is: S‑parameters
Q.117 The input admittance of a two‑port with H‑parameters when port 2 is open is:
G11
G12
H11
H12
Explanation - G11 is the admittance seen at port 1 when port 2 is open.
Correct answer is: G11
Q.118 For a two‑port network, the condition B = 0 indicates:
The network is reciprocal
The network is lossless
Port 2 is isolated from port 1
Port 1 is isolated from port 2
Explanation - B = 0 means no current at port 2 is produced by a voltage at port 1 (isolated).
Correct answer is: Port 1 is isolated from port 2
Q.119 The parameter H22 in a two‑port H‑parameter matrix represents:
Output conductance with input short
Input conductance with output short
Output resistance with input short
Input resistance with output short
Explanation - H22 is the output admittance when the input port is shorted.
Correct answer is: Output conductance with input short
Q.120 The input impedance of a two‑port described by Y‑parameters when port 2 is open is:
1/Y11
1/Y12
Y11
Y12
Explanation - With port 2 open, the admittance seen is Y11, so the impedance is 1/Y11.
Correct answer is: 1/Y11
Q.121 Which of the following represents the inverse relationship between ABCD and its reciprocal?
ABCD × reciprocal = I
ABCD + reciprocal = I
ABCD × reciprocal = 0
ABCD – reciprocal = I
Explanation - The reciprocal of an ABCD matrix is its inverse, so their product is the identity matrix.
Correct answer is: ABCD × reciprocal = I
Q.122 The S‑parameter S12 is also known as:
Reverse transmission coefficient
Forward transmission coefficient
Reflection coefficient at port 1
Reflection coefficient at port 2
Explanation - S12 describes the signal that travels from port 2 to port 1.
Correct answer is: Reverse transmission coefficient
Q.123 The input admittance of a two‑port with Y‑parameters when port 2 is shorted is:
Y11
Y12
1/Y11
1/Y12
Explanation - Shorting port 2 (V2=0) gives input admittance Y11.
Correct answer is: Y11
Q.124 A two‑port with S11 = 0.5, S22 = 0.5, S12 = 0, S21 = 1 is:
A matched load
An amplifier with reflections
A perfect transmission line
A lossless filter
Explanation - Non‑zero reflections and forward gain >1 indicate an amplifier that is not matched.
Correct answer is: An amplifier with reflections
Q.125 The Y‑parameter matrix of a two‑port with Y12 = Y21 = 0 is:
Reciprocal
Symmetric
Non‑reciprocal
Isolated
Explanation - Zero off‑diagonal admittances mean the ports are electrically isolated.
Correct answer is: Isolated
Q.126 For a two‑port network, the input reflection coefficient is zero when:
The source impedance equals the input impedance
The load impedance equals the input impedance
The input impedance is infinite
The input impedance is zero
Explanation - Matching the source to the network eliminates reflection.
Correct answer is: The source impedance equals the input impedance
Q.127 Which two‑port parameter set is commonly used for RF filters with low insertion loss?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - S‑parameters measure insertion loss directly at RF frequencies.
Correct answer is: S‑parameters
Q.128 The ABCD parameters of a series‑shunt network are:
A = 1, B = R, C = 1/C, D = 1
A = 1, B = 0, C = 0, D = 1
A = Z0, B = 0, C = 0, D = 1/Z0
A = 0, B = R, C = 1/C, D = 0
Explanation - A series resistance and shunt capacitance correspond to that ABCD matrix.
Correct answer is: A = 1, B = R, C = 1/C, D = 1
Q.129 The input impedance of a two‑port with ABCD parameters when port 2 is open is:
A/B
B/A
C/D
D/C
Explanation - With port 2 open (I2=0), Zin = A/B.
Correct answer is: A/B
Q.130 Which of the following is NOT a correct property of a reciprocal two‑port?
S12 = S21
Z12 = Z21
Y12 = Y21
H12 = −H21
Explanation - Reciprocity requires symmetry, not sign inversion.
Correct answer is: H12 = −H21
Q.131 The parameter S21 is known as:
Forward transmission coefficient
Reverse transmission coefficient
Input reflection coefficient
Output reflection coefficient
Explanation - S21 measures the signal transmitted from port 1 to port 2.
Correct answer is: Forward transmission coefficient
Q.132 For a lossless two‑port, the condition S11 = S22 = 0 and S12 = S21 = 1 corresponds to:
A matched load
A perfect transmission line
An isolator
A matched amplifier
Explanation - Zero reflections and full transmission represent a lossless matched line.
Correct answer is: A perfect transmission line
Q.133 The Y‑parameter matrix of a two‑port with Y11 = Y22 and Y12 = Y21 is:
Reciprocal
Non‑reciprocal
Lossless
Symmetric
Explanation - Equal diagonal and symmetric off‑diagonals indicate a symmetric network.
Correct answer is: Symmetric
Q.134 Which two‑port parameter set is used to model a voltage controlled current source?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - H‑parameters can represent a voltage‑controlled current source via H12.
Correct answer is: H‑parameters
Q.135 The input reflection coefficient at port 1 when the two‑port is terminated with its characteristic impedance is:
S11
S12
S21
S22
Explanation - S11 is defined under matched terminations at port 1.
Correct answer is: S11
Q.136 Which of the following parameters is dimensionless?
Z‑parameters
Y‑parameters
S‑parameters
G‑parameters
Explanation - S‑parameters are ratios of voltages or currents, hence dimensionless.
Correct answer is: S‑parameters
Q.137 The condition G12 = G21 for a two‑port is an example of:
Reciprocity
Symmetry
Losslessness
Impedance matching
Explanation - G‑parameters are the conductance form of Y‑parameters; symmetry implies reciprocity.
Correct answer is: Reciprocity
Q.138 The input impedance of a two‑port with ABCD parameters when port 2 is shorted is:
A/C
C/A
B/D
D/B
Explanation - Shorting port 2 (V2=0) yields Zin = A/C.
Correct answer is: A/C
Q.139 The two‑port parameter H12 is associated with:
Voltage source at port 1 producing current at port 2
Voltage source at port 2 producing current at port 1
Current source at port 1 producing voltage at port 2
Current source at port 2 producing voltage at port 1
Explanation - H12 relates voltage at port 1 to current at port 2.
Correct answer is: Voltage source at port 1 producing current at port 2
Q.140 For a two‑port network with S‑parameters, the condition S21 = 0 indicates:
No forward transmission
No reverse transmission
Zero reflection at port 1
Zero reflection at port 2
Explanation - S21 = 0 means no signal travels from port 1 to port 2.
Correct answer is: No forward transmission
Q.141 Which two‑port parameter set is typically used for describing a circuit with high input and output impedances at DC?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - Y‑parameters are suitable for high‑impedance DC analysis.
Correct answer is: Y‑parameters
Q.142 The reflection coefficient Γ at port 2 when port 1 is excited and terminated in a matched load is:
S22
S12
S21
S11
Explanation - S22 is measured at port 2 with port 1 matched and excited.
Correct answer is: S22
Q.143 Which of the following statements is true for a lossless two‑port?
S11 = S12
S21 = 0
S11 + S22 = 0
S11² + S21² = 1
Explanation - For a lossless network, the sum of squared magnitudes of reflection and transmission coefficients equals 1.
Correct answer is: S11² + S21² = 1
Q.144 The input impedance of a two‑port described by Y‑parameters when port 2 is open is:
1/Y11
1/Y12
Y11
Y12
Explanation - With port 2 open, admittance seen is Y11, so impedance is 1/Y11.
Correct answer is: 1/Y11
Q.145 The parameter B in an ABCD matrix is most closely related to:
Voltage gain
Current gain
Output admittance
Input admittance
Explanation - B appears in the voltage output expression: V2 = A V1 − B I2, indicating its relation to output admittance.
Correct answer is: Output admittance
Q.146 The S‑parameter S22 is also referred to as the:
Forward transmission coefficient
Reverse transmission coefficient
Output reflection coefficient
Input reflection coefficient
Explanation - S22 measures the reflection at port 2.
Correct answer is: Output reflection coefficient
Q.147 For a two‑port with H‑parameters H11 = 1 and H12 = 0, the port 1 behaves as:
An ideal voltage source
An ideal current source
An isolated port
An open circuit
Explanation - H11 = 1 and H12 = 0 indicate V1 = I1, resembling a voltage source.
Correct answer is: An ideal voltage source
Q.148 The condition G12 = 0 in an H‑parameter matrix indicates:
Port 2 is isolated from port 1
Port 1 is isolated from port 2
The network is lossless
The network is reciprocal
Explanation - G12 = 0 means no current at port 2 due to voltage at port 1.
Correct answer is: Port 2 is isolated from port 1
Q.149 Which two‑port parameter set is typically used to analyze cascaded filter sections?
Z‑parameters
Y‑parameters
ABCD parameters
H‑parameters
Explanation - ABCD parameters are easily multiplied for cascaded sections.
Correct answer is: ABCD parameters
Q.150 The input reflection coefficient Γin for a two‑port with impedance Zin and source impedance Zs is:
(Zin - Zs)/(Zin + Zs)
(Zs - Zin)/(Zs + Zin)
(Zin + Zs)/(Zin - Zs)
(Zs + Zin)/(Zs - Zin)
Explanation - Standard reflection formula: Γ = (Zin - Zs)/(Zin + Zs).
Correct answer is: (Zin - Zs)/(Zin + Zs)
Q.151 The parameter S12 is zero when the two‑port is:
Reciprocal
Isolated
Lossless
Matched
Explanation - S12 = 0 indicates no reverse transmission, implying isolation.
Correct answer is: Isolated
Q.152 The Y‑parameter Y11 of a two‑port with port 2 shorted is:
I1/V1
V1/I1
I2/V2
V2/I2
Explanation - Y11 is the admittance seen at port 1 when port 2 is shorted, i.e., I1/V1.
Correct answer is: I1/V1
Q.153 The condition B = C for a two‑port indicates:
Reciprocity
Symmetry
Losslessness
Matching
Explanation - B = C is one of the symmetry conditions in a reciprocal two‑port.
Correct answer is: Symmetry
Q.154 The input impedance of a two‑port described by S‑parameters when both ports are matched is:
Z0
0
∞
Zin ≠ Z0
Explanation - With matched ports, the input sees the characteristic impedance Z0.
Correct answer is: Z0
Q.155 In a two‑port network, the condition S21 = 1 indicates:
No insertion loss
Zero reflection at port 1
Zero reflection at port 2
Perfect isolation
Explanation - S21 = 1 means the forward transmission is lossless (unit magnitude).
Correct answer is: No insertion loss
Q.156 The H‑parameter H11 is the voltage at port 1 due to:
Voltage at port 1
Voltage at port 2
Current at port 1
Current at port 2
Explanation - H11 relates V1 to I1: V1 = H11·I1 + H12·V2.
Correct answer is: Voltage at port 1
Q.157 The condition S11 = 1 for a two‑port indicates:
Full reflection at port 1
Full transmission from port 1 to port 2
Zero reflection at port 1
Full transmission from port 2 to port 1
Explanation - S11 = 1 means the signal is completely reflected at port 1.
Correct answer is: Full reflection at port 1
Q.158 The ABCD parameters of a series‑shunt network with series resistance R and shunt capacitance C are:
A = 1, B = R, C = 1/C, D = 1
A = 1, B = 0, C = 0, D = 1
A = R, B = 0, C = 0, D = 1/R
A = 0, B = R, C = 1/C, D = 0
Explanation - Series R and shunt C yield the standard ABCD matrix for a series‑shunt network.
Correct answer is: A = 1, B = R, C = 1/C, D = 1
Q.159 In a two‑port with H‑parameters, the element H12 is zero when:
The network is reciprocal
Port 1 is isolated from port 2
Port 2 is isolated from port 1
The network is lossless
Explanation - H12 = 0 means no voltage at port 1 produces current at port 2.
Correct answer is: Port 1 is isolated from port 2
Q.160 The input impedance of a two‑port described by S‑parameters when port 1 is matched and port 2 is shorted is:
Z0
0
∞
Z0 + 0
Explanation - With port 2 shorted, the input sees a short through the two‑port, resulting in zero impedance.
Correct answer is: 0
Q.161 The Y‑parameter Y12 is the current at port 1 due to:
Voltage at port 1
Voltage at port 2
Current at port 1
Current at port 2
Explanation - Y12 relates I1 to V2: I1 = Y12·V2 + Y11·V1.
Correct answer is: Voltage at port 2
Q.162 For a two‑port with S‑parameters, the condition S21 = S12 is:
Reciprocal
Isolated
Lossless
Matched
Explanation - Reciprocity requires forward and reverse transmission coefficients to be equal.
Correct answer is: Reciprocal
Q.163 The input reflection coefficient at port 1 is zero when:
Zin = 0
Zin = ∞
Zin = Zs
Zin = 0 or ∞
Explanation - Matching the source and load impedances eliminates reflection.
Correct answer is: Zin = Zs
Q.164 The condition S22 = 0 in a two‑port indicates:
No reflection at port 2
Full reflection at port 2
Full transmission from port 2 to port 1
Full transmission from port 1 to port 2
Explanation - S22 = 0 means the port is matched and no reflection occurs.
Correct answer is: No reflection at port 2
Q.165 The Y‑parameter Y11 of a two‑port with port 2 shorted is:
I1/V1
V1/I1
I2/V2
V2/I2
Explanation - Y11 represents the admittance seen at port 1 when port 2 is shorted.
Correct answer is: I1/V1
Q.166 The parameter H22 is the output resistance of a two‑port when:
Port 1 is shorted
Port 1 is open
Port 2 is shorted
Port 2 is open
Explanation - H22 is the output conductance (inverse of resistance) when the input is shorted.
Correct answer is: Port 1 is shorted
Q.167 A two‑port with H11 = 1, H12 = 0, H21 = 0, H22 = 1 behaves as:
A voltage controlled current source
An ideal transformer
An identity network
A short circuit
Explanation - All H‑parameters equal 1 correspond to an identity network that transmits signals unchanged.
Correct answer is: An identity network
Q.168 For a two‑port network, the input impedance when port 2 is terminated in a matched load is:
A/B
B/A
C/D
D/C
Explanation - With port 2 matched (ZL = Z0), Zin = A/B for an ABCD network.
Correct answer is: A/B
Q.169 Which two‑port parameter set is commonly used for analyzing the power transfer in RF mixers?
Z‑parameters
Y‑parameters
S‑parameters
H‑parameters
Explanation - RF mixers operate at high frequencies where S‑parameters are the standard representation.
Correct answer is: S‑parameters
Q.170 The input reflection coefficient at port 1 for a two‑port terminated in an infinite impedance load is:
S11
S12
S21
S22
Explanation - S11 is measured with the other port matched (or infinite load).
Correct answer is: S11
Q.171 The condition B = 0 and C = 0 in an ABCD matrix means the two‑port:
Is isolated
Is a lossless transformer
Has zero transmission
Has infinite transmission
Explanation - B = C = 0 indicates no coupling between ports.
Correct answer is: Is isolated
Q.172 Which of the following is the definition of the input admittance of a two‑port with Y‑parameters?
Y11 + Y12
Y11
Y12
Y22
Explanation - The input admittance is simply Y11 when port 2 is open.
Correct answer is: Y11
Q.173 The S‑parameter S12 is the ratio of:
Output voltage at port 1 to input voltage at port 2
Output voltage at port 2 to input voltage at port 1
Output current at port 1 to input current at port 2
Output current at port 2 to input current at port 1
Explanation - S12 represents the reverse transmission from port 2 to port 1.
Correct answer is: Output voltage at port 1 to input voltage at port 2
Q.174 For a lossless two‑port with S11 = S22 = 0, the network is:
Matched
Isolated
Amplifier
Attenuator
Explanation - Zero reflections at both ports mean the network is perfectly matched.
Correct answer is: Matched