Dalam satu sistem perhubungan yang tipikal merangkumi sistem penghantaran dan sistem penerimaan. Informasi dari punca mugkin dalam bentuk analog atau dalam bentuk digit akan disalurkan dari pemancar ke penerima melalui saluran. Penerima menukar balik informasi yang dapat daripada pemancar dengan menggunakan proses penyahmodulatan. Penukar analog digit merupakan elektronik litar bersepadu yang menukar isyarat daripada bentuk analog ke bentuk digit. Penukar analog digit merupakan penyambung antara isyarat analog dan digit pada masa pemprosesan isyarat dan pengelolaan data. Dalam proses penukaran analog digit melibatkan process sampel dan pegang dan process pengkuntuman dan pengekodan. Dalam proses sampel dan pegang, isyarat analog diukur pada masa yang uniform dipanggil sebagai masa pensampelan. Pada masa kini, litar bersepadu penukar analog digit mudah didapati dalam pasaran. Manakala proses penukaran analog digit menjadi mudah dengan menggunakan litar bersepadu. Konsep dan operasi dalam penukaran analog digit telah diabaikan. Objektif untuk projek ini ialah menghasilkan penerima sampel dan pegang dengan menggunakan kedua-dua perisian dan perkakasan. Tatarajah sampel dan pegang telah dipelajari. Jenis dan nilai komponen untuk litar sampel dan pegang dikira dengan formula. Reka litar dilukis dengan menggunakan litar pensimulasi Multisim@13.0 dan menilai prestasi litar sebelum pelaksanaan perkakasan. Perisian EAGLE PCB Design digunnkan untuk menghasilkan bentangan pembikinan papan litar tercetak. Perisian MATLAB digunakan untuk membina modal sampel dan pegang. Pelbagai jenis masukan disaluran dan membuat pembandingan prestasi dengan prestasi simulasi. Dalam gambar rajah 4-10 merupakan keluran bagi papan litar tercetak daripada pemerhatian osiloskop. Dalam gambar rajah 4-10, bentuk grah merupakan gelombang segi empat sama atau dipanggil sebagai “grah sampel dan pegang”.
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A typical digital communication system comprises transmit and receive system. The information from the source may be either analog signal or digital signal transmitted from the transmitter to the receiver through a channel. The signal will undergoes modulation process before transmitted to the receiver. The receiver attempts to translate the received signal back into the original information sent by the source. This process called demodulation. Analog digital converter (ADC) is an electronic integrated circuit which converts a signal from analog (continuous) to digital (discrete) form. The ADC provides a link between the analog world of transducers and the digital world of signal processing and data handling. In ADC conversion process involved sampling and holding process and quantization and encoding. In sample and hold process, it measuring analog signals at uniform time interval which is called sampling time. In the market, an ADC IC can be obtained easily. The conversion process has become more easier by just connected the ADC IC with the design circuit. The basic principle and operation of converting the analog signal to digital signal is neglected. The objectives of this project is to develop a sample and hold receiver using both software and hardware implementation. First of all, the configuration of the sample and hold receiver is studied. The type of components and value of each components are calculated using formulae. The designed circuit is constructed using circuit simulator Multisim@13.0 software to evaluate its performance before converted into hardware implementation. The EAGLE PCB Design software is used to generate the layout for printed circuit board fabrication. The MATLAB is used to construct the sample and hold model. Different inputs are inserted and the performance of these model is compared with the performance of the simulation. In Figure 4-10 shows the output result of printed circuit board observed from the oscilloscope. From Figure 4-10, it shows the output signal is in “sample and hold” mode (square wave).
Development of sample and hold receiver for baseband digital communication system / Yow Li Chen