IM electrical nd electronics engg by grad having 24 months IT exp. here are the questions asked in various interviews.
but those books are really confusing and deviated from the actual CAT questions.i dont have a pc too. so i cant refer any online materials. i spend 4 hours daily for preparing CAT. my friend advised me that 4 hours of such preparations=1 hour of preparation by using standard materials like TIME,IMS. i went to TIME and ask them whether i can get the materials alone for a cheaper price. they said they will provide material only along with a course. and that course costs 20000! i was heart broken! i desperately need some standard books. i would be greatly thankful if someone is will to donate extra materials or old materials! PG is my only hope. so please help me! thank you all
guys, muje IMI-D k interview me puche gaye kuch acads ques: (i m an ece final yr student.)
Why not use hexavalent or divalent impurity while doping semiconductors?
i.e. Frequency modulation Frequency modulation is the process by which frequency of the carrier signal c(t) changes with respect to the modulating signal m(t). FM modulated signal s(t) is a nonlinear function of the modulating signal m(t), thus it is known as nonlinear modulation process. More difficult than amplitude modulation (AM).
Depending to this modulation index FM can ne classified into two types –
Narrowband FM : modulation index is smaller than one radian
Narrowband FM Modulation index is less than 1 Maximum modulating frequency is usually 3kHz & maximum frequency deviation is =75 kHz. A narrowband FM wave consist of a carrier, an upper side-frequency component & a lower side component.
Wideband FM : modulation index is larger than 1 radian
Wideband FM Modulation index normally exceeds unity. Modulation frequencies extend from 30 Hz to 15 kHz. Maximum permissible deviation is=75 kHz. Wideband FM system need large bandwidth, typically 15 times that of narrowband FM system . Wideband FM systems are used in entertainment broadcasting.
Transmission Bandwidth of FM Waves :
Transmission Bandwidth of FM Waves In practice, FM wave is limited to finite number of significant side-frequencies compatible with a specified amount of distortion. Thus an effective bandwidth is required for the transmission of an FM wave. Approximate rule for transmission bandwidth of an FM wave generated by a single-tone modulating wave of frequency f m is This relation is known as Carson's rule .
Transmission Bandwidth of FM Waves According to international regulations of FM broadcast – Maximum frequency deviation, f d =±75 kHz Allowable bandwidth per channel=200 kHz Frequency stability of carrier =±2 kHz
Advantages of FM:
Amplitude of the frequency modulated wave remains unaffected.
Large decrease in noise, hence increase in S/N ratio.
Noise may reduce by increasing deviation Frequency allocation allows for a guard band which reduces adjacent channel interference.
FM permits several independent transmitters on the same frequency with negligible interference.
Disadvantages of FM:
FM has too much advantages besides it also has some disadvantages - FM wave can't cover large area.
Transmitting & receiving equipments for FM are complex & costly.
Reception using conventional method is limited to line of side.
A much wider channel, typically 200 kHz, is needed for FM.
Applications of FM:
Applications of FM FM has so many applications such as –
Magnetic tape storage: FM is used at intermediate frequencies by analog VCR systems (including VHS) to record both the luminance(black and white) portions of the video signal. Sound : FM is also used at audio frequencies to synthesize sound, which is known as FM synthesis.
Radio : FM is used in many radio stations (FM Radio Stations) all over the world. Normally the frequency range of FM channels are between 88.0 MHz - 108.0 MHz.