superheterodyne

superheterodyne - is the image frequency for 2 C f = 157...

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Intermediate frequency filter and amplifiers Broadband radio frequency bandpass filter Detector r (t) m ~ (t) Local Oscillator ) 2 cos( t f LO π Fig. 3-1 Suppose someone has designed a superheterodyne receiver (Fig.3-1) to receive radio stations that use the frequency band [ 2 , 1 C C f f ] = [108 MHz, 157 MHz]. This superheterodyne receiver is designed to use low-side injection down conversion (i.e. the local oscillator frequency is less than the carrier frequency it is down converting; C LO f f < ) to the intermediate frequency IF f . (a) The initial design of the superheterodyne receiver used an intermediate frequency of 12 = IF f MHz. Find the image frequency band (i.e. find [ f image1 , f image2 ], where f image1 is the image frequency for 1 C f = 108 MHz and f image2
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Unformatted text preview: is the image frequency for 2 C f = 157 MHz). (b) The choice of using 12 = IF f MHz in Part a. is poor because the image frequency band overlaps the radio frequency band. This prevents the possibility of using the broadband radio frequency bandpass filter to eliminate the effects of the image frequencies. Assuming 0 &lt; IF f &lt; 100 MHz, find the range for IF f such that the image frequency band [ f image1 , f image2 ] does not overlap the radio frequency band [108 MHz, 157 MHz]. Your design will be superior as the image frequencies can easily be eliminated by the broadband filter! Still assume low-side injection down conversion (i.e. C LO f f &lt; ) to the intermediate frequency IF f ....
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This note was uploaded on 07/16/2009 for the course SYSC 3501 taught by Professor Osama during the Summer '09 term at Carleton CA.

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superheterodyne - is the image frequency for 2 C f = 157...

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