# Microwave Engineering Questions and Answers – Non – Linear Distortion – 2

This set of Microwave Engineering Interview Questions and Answers for freshers focuses on “Non-Linear Distortion-2”.

1. If the third order input intercept point of a mixer is 13 dBm and if the mixer has a conversion loss of 6 dBm, then the third order intercept point at the output is:
a) 3 dBm
b) 7 dBm
c) 4 dBm
d) 2 dBm

Explanation: Third order output intercept point is given by the relation OIP3=IIP3 (G). G is the conversion loss in the device. In dBm scale they have to be subtracted. Subtracting the given values, the output third order intercept point is 7 dBm.

2. In a coherent cascade network, if the third order intercept point of an amplifier is 158 mW and the third order intercept point of a mixer is 5 mW, with an insertion loss of 6 dB, then the third order intercept point of the coherent cascade is:
a) 2 mW
b) 4 mW
c) 4.4 mW
d) 5 mW

Explanation: The third order intercept point of the cascade is given by the expression ((G2 (OIP3’)-1+ (OIP3’’)-1)-1. Substituting the values in the above expression for respective terms, the third order intercept point of the cascade is 4.4 mW.

3. In a non coherent cascade network, if the third order intercept point of an amplifier is 158 mW and the third order intercept point of a mixer is 5 mW, with an insertion loss of 6 dB, then the third order intercept point of the coherent cascade is:
a) 3 mW
b) 4.9 mW
c) 5.2 mW
d) 2 mW

Explanation: The third order intercept point for a non coherent cascade network is given by ((G22 (OIP3’)-2+ (OIP3’’)-2)-2. Substituting the values in the above expression for respective terms, the third order intercept point of the cascade is 4.9 mW.

4. Inter modulation distortion occurs only in active non linear devices and they are the only source of inter modulation distortion.
a) True
b) False

Explanation: It is also possible for inter modulation products to be generated by passive non linear effects in connectors, cables and antennas or almost every element where there is metal to metal contact. This effect is called passive inter modulation.

5. ________ is defined as the operating range for which a component or system has desirable characteristics.
a) Static range
b) Dynamic range
c) Characteristic gain
d) None of the mentioned

Explanation: Dynamic range is defined as the operating range for which a component or system has desirable characteristics. For a power amplifier, this may be the power range that is limited at the low end by noise and at the high end by the compression point.
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6. The expression for linear dynamic range is given by:
a) OP1 dB- No
b) OP1 dB/ No
c) OP1 dB+No
d) None of the mentioned

Explanation: Linear dynamic range is defined as the ratio of 1 dB compression point to the noise level of the component. In dB scale, it is the difference of 1 dB compression point and the noise level of the component.

7. Passive intermodulation is significant only when:
a) The input signal levels are low
b) Input signal levels are high
c) Input signal is sinusoidal
d) Input signal is exponential

Explanation: Because of the dependence of the third order intermodulation products with input power, passive intermodulation is usually only significant when input signal powers are relatively large.

8. A receiver has a noise figure of 7 dB, gain of 40 dB, noise temperature is 290 K. then the noise power at the receiver is:
a) 47. 4 dBm
b) -47.4 dBm
c) 23 dBm
d) -23 dBm

Explanation: Noise power at the receiver is given by the expression GkB [TA + (F-1) T0]. G is the gain of the amplifier, TA is the noise temperature. F is the noise figure. Substituting the given values in the above equation, the power output at the receiver in dBm scale is -47.4 dBm.

9. For a receiver, 1 dB compression point is 25 dBm and the noise power at the receiver output is -47.4 dBm, the linear dynamic range is:
a) 70 dB
b) 72.4 dB
c) 68 dB
d) 85 dB

Explanation: Linear dynamic range of the system is the difference of 1 dB compression point and the noise in the system. Substituting in the given equation, the linear dynamic range is 72.4 dB.

10. If the third order intercept point of a receiver is 35 dBm and the total noise in the receiver is -47.4 dBm signals to noise ratio is 10, then the spurious free dynamic range is:
a) 50.9 dB
b) 44.9 dB
c) 34.9 dB
d) 67 dB

Explanation: The spurious free dynamic range of a receiver is given by the relation 0.6667 (OIP3_ No)-SNR. Substituting in the above equation, the spurious free dynamic range is 44.9 dB.

Sanfoundry Global Education & Learning Series – Microwave Engineering.
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