Outline The Simplest AM . . . Superheterodyne . . . Downconverting or . . . Superhet With Dual . . . OFDM Fundamentals Home Page Page 1 of 17 Go Back Full Screen Close Quit Fundamentals of Communications (XE37ZKT), Part I Superheterodyne, OFDM Josef Dobeˇ s 8th
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JJ II Communications (XE37ZKT), Part I …radio.feld.cvut.cz/personal/dobes2/(8)SuperhetOFDM.pp4.pdfOutline The Simplest AM... Superheterodyne... Downconverting or... Superhet With
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Example: A terrestrial TV tuning receiver is designed to cover theRF frequency range of 45 to 860 MHz, with channel spacings of 8 MHzand an IF of 40 MHz. Assess the downconverting or upconvertingreceiver solutions relating to potential problems with the image fre-quency band.
Example: A terrestrial TV tuning receiver is designed to cover theRF frequency range of 45 to 860 MHz, with channel spacings of 8 MHzand an IF of 40 MHz. Assess the downconverting or upconvertingreceiver solutions relating to potential problems with the image fre-quency band.
Downconverting: The local oscillator minimum and maximumfrequencies are given by the range and specified IF, i.e.
Example: A terrestrial TV tuning receiver is designed to cover theRF frequency range of 45 to 860 MHz, with channel spacings of 8 MHzand an IF of 40 MHz. Assess the downconverting or upconvertingreceiver solutions relating to potential problems with the image fre-quency band.
Downconverting: The local oscillator minimum and maximumfrequencies are given by the range and specified IF, i.e.
Upconverting: A better way consists in choosing a greater IF.Lets pick an IF frequency of say 1.5 GHz. The required LO will nowbe (the LO is below the IF now):3
Upconverting: A better way consists in choosing a greater IF.Lets pick an IF frequency of say 1.5 GHz. The required LO will nowbe (the LO is below the IF now):3
Upconverting: A better way consists in choosing a greater IF.Lets pick an IF frequency of say 1.5 GHz. The required LO will nowbe (the LO is below the IF now):3
which is not problematic now because the image band does not inter-sect the signal band – see the diagram again.
As shown, the greater IF causes the suppression of the images. How-ever, the most selective filters can only be realized for lower frequen-cies. As a result, a superheterodyne with dual conversion can beconsidered an optimal solution – see the superhet with the dual con-version.