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RF AMPLIFIER DESIGN AND MATCHING NETWORKS
1)What is meant by fractional bandwidth?
The fractional bandwidth is given by
2) Write the function of matching networks?
Matching networks can help stabilize the amplifier by keeping the source and load impedances in the appropriate range. Impedance matching (or tuning) is an important issue for - Maximum power is delivered when load is matched to line (assuming the generator is matched) - Power loss is minimized. S/N- ratio of receiver components is increased. - Amplitude and phase errors are reduced.
3) What is function of input and output matching networks?
Input and output matching networks are needed to reduce undesired reflections and improve the power flow capabilities.
4) What are the parameters used to evaluate the performance of an amplifier?
Key parameters of amplifier, to evaluate the performance are
i. Gain and gain flatness(in dB)
ii. Operating frequency and bandwidth (in Hz)
iii.Output power (in dB)
iv. Power supply requirements (in V and A)
v.Input and output reflection coefficients (VSWR)
vi. Noise figure (in dB)
5)Define transducer power gain.
Transducer power gain is nothing but the gain of the amplifier when placed between source and load.
6) Define Unilateral Power gain.
It is the amplifier power gain, when feedback effect of amplifier is neglected i.e.S12=0.
7) What is available Power Gain (GA) at Load?
The available power gain for load side matching (TL = T*Out) is given as,
8) Define Operating Power Gain.
The operating power gain is defined as “the ratio of power delivered to the load to the power supplied to the amplifier”.
9) Write a short note on feedback of RF circuit.
i. If |T|>1, then the magnitude of the return voltage wave increases called positive feedback, which causes instability (oscillator).
ii.If |T|<1, then the return voltage wave is totally avoided (amplifier). It‟s called as negative feedback.
9)Define Stability factor ( Rolette Factor)
10)Draw the block diagram of a Single Stage Amplifier
11.Give the expression that relates nodal quality factor (Qn) with loaded quality factor (QL)
Nodal quality factor (Qn) is defined as ratio of the absolute value of the reactance Xs to the corresponding Resistance Rs
12.What are the need of Impedance Matching Network
ü Minimal power loss in feed line
ü Maximum power delivary
ü Improving the S/N ratio of the system for sensitive receiver components
ü Reducing amplitude & phase errors in a power distribution networks
ü Minimum reflection in transmission line
ü Optimal efficiency
13.Define power gain of amplifier in terms of S- parameter and reflection coefficient
Transducer Power Gain
Transducer Power Gain is nothing but the gain of the amplifier when placed between source and load
The Operating power gain is defined as the ratio of power delivered to the load to the power supplied to the amplifier
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