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Articles by M.F.L. Abdullah
Total Records ( 2 ) for M.F.L. Abdullah
  M.F.L. Abdullah and R.J Green
  An understanding of the noise is required for a receiver’s performance to be precisely characterized. The amount of noise present in a receiver will be the primary factor that determines the receiver’s sensitivity. In this study, the definition of noise in infrared communication is discussed to demonstrate the effects of receiver noise on performance for adjustable bootstrap transimpedance and voltage feedback receiver amplifier. The noise sources that are commonly found in an optical wireless receiver are then discussed, including noises that are of optical as well as of electrical origin. The equivalent circuit model that will describe the noise performance of the bootstrap transimpedance and voltage feedback amplifier circuit shows, that the input noise current density is flat 380 pV/ from 1 Hz to 10 GHz and starts to increase. The output noise density, shows a flatness of 1.1nV/ from 1 Hz to 80 MHZ when it starts descending according to the capacitor value which adjust the bandwidth. Results also showed that the output noise density remains constant during the bandwidth adjustment process.
  M.F.L. Abdullah and Mayada Faris Ghanim
  According to the classification based on the modulation method used to obtain the spread spectrum signal, a study of the CDMA (Code Division Multiple Access) for all current techniques is presented in this study. The first technique is DS-CDMA (Direct Sequence-Code Division Multiple Access) which is used for many commercial communication systems (almost all 3G mobile cellular systems as prime multiple access air-link architecture) and measurement instruments. This type is illustrated from the both transmitter and receiver, DS-CDMA is then compared with the two types of multiple access (time and frequency division) because it is the 1st type of code division multiple access. Next, the 2nd type of CDMA techniques: FH-CDMA (Frequency Hopping-Code Division Multiple Access) all the basic concepts of the modulator and the receiver are clarified then a comparison with DS-CDMA is done with an expectations for FH-CDMA in the future according to the advancement in micro-electronics technologies. TH-CDMA (Time Hopping-Code Division Multiple Access) represents the 3rd technique of code division multiple access, it is transmitter and receiver are analyzed and shown that TH-CDMA uses the whole wideband spectrum for short periods instead of parts of the spectrum all of the time. All currently researchers are exploiting new modulation, diversity and coding techniques to overcome the limited natural wireless resources: frequency and power where this represents the hybrid CDMA (forth technique) which is discussed with all necessary equations.
 
 
 
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