GATE Electronics|Electrical

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Define a memoryless system. Ans. A system is memoryless if the output at any time instant depends only on the input at that particular instant, it is also called as static system. @GateElectronics

What are even signals and odd signals? Give their expressions. Ans. Odd signals are symmetric in the first and third quadrant. Given as              f(-t) = -f(t) Even signals are symmetric in first and second quadrant. Given as              f(-t) = f(t) @GateElectronics

What are the methods to generate SSB? Ans. (i) Filter method: double side band signal is passed through filter to get single side band signal.  (ii) Phase shift method: phase shift using Hilbert transform is done to generate SSB signal. @GateElectronics

Why direct sequence spread spectrum secure? Ans. Direct Sequence Spread Spectrum (DSSS) is a spread spectrum technique whereby the original data signal is multiplied with a pseudo random noise spreading code. This spreading code has a higher chip rate (this the bitrate of the code), which results in a wideband time continuous scrambled signal. The steam of information in DSSS is divided into small pieces, each associated with a frequency channel across spectrum. Data to be transmitted is combined data based on spreading ratio. The chipping code is a redundant bit pattern associated with each bit transmitted. This makes the communication safe and secure. @GateElectronics

Tunnel Diode: A normal p-n junction diode exhibits doping concentration of about 1 part in 10⁸ (1 dopant atom in 10⁸ Si or Ge atoms). If the doping level is further increased, say about 1 part in 10³, we see the change in characteristics of diode. As a result, the depletion layer gets very narrow. In comparison with the conventional diode, the depletion layer of tunnel diode is 100 times narrower. Read more about tunnel diode here: https://electricalvoice.com/tunnel-diode-symbol-working-applications

Explain the difference between sensitivity and selectivity? Ans. The sensitivity of an electronic device, such as a communications system receiver, or detection device, such as a PIN diode, is the minimum magnitude of input signal required to produce a specified output signal having a specified signal-to-noise ratio, or other specified criteria. Selectivity is a measure of the performance of a radio receiver to respond only to the radio signal it is tuned to (such as a radio station) and reject other signals nearby in frequency, such as another broadcast on an adjacent channel. In communication, the sensitivity of a communication receiver is the ability of communication receiver to satisfactorily work on weak signals while selectivity of a receiver is the characteristic that determines the extent to which it is capable of distinguishing between the desired and undesired signals. @GateElectronics

How microprocessor functions without internal memory? Ans. Microprocessor consist of address, data and control buses with some internal registers to process the task through external memory by using certain commands to access memory locations of the external memory. @GateElectronics

How to convert Analog signal into digital? Ans. Analog Signal(input) → Sample & Hold circuit → Quantization → Encoding → Digital Signal (output) Sampler takes samples i.e. records value of the analog signal at a specified time and this random values of sampled signal is quantized to defined levels and these levels are encoded by defined number of bits and thus digital signal is obtained. @GateElectronics