File:Superheterodyne image problem.svg
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Summary
DescriptionSuperheterodyne image problem.svg |
English: Diagram of the radio signals at different points in a superheterodyne radio receiver showing the problem of image response and why the receiver needs an RF image filter on the input. The horizontal axis is frequency while the vertical axis is voltage. The diagrams show what would happen in a superheterodyne without an RF filter.
In the superheterodyne the signal of the desired radio station (S1, blue) at frequency is mixed with a sinusoidal signal from a local oscillator (LO) at frequency , producing a heterodyne or "beat" frequency at the difference between the two frequencies, called the intermediate frequency (IF) at . After being shifted to the intermediate frequency, the signal S1 passes through the IF filter which removes signals at all other frequencies, and is demodulated. However there is a second frequency on the other side of the LO frequency which also produces a heterodyne at the IF frequency when mixed with the LO. This is called the image frequency . Thus the superheterodyne receives on two frequencies: Русский: Графики радиосигналов в разных точках супергетеродинного радиоприемника иллюстрирующие возникновение и прохождение по тракту помехи с зеркальной частотой и поясняющая почему приемнику обычно необходим входной радиочастотный фильтр. По горизонтальной осотложена частота сигналов, а вертикальная ось — напряжение, или на красном графике коэффициент передачи фильтра в зависимости от частоты. На диаграммах показано влияние помехи по зеркальному каналу в супергетеродине без входного фильтра. В супергетеродине сигнал нужной радиостанции (S1, синий) на частоте смешанный с синусоидальным сигналом от гетеродина на частоте , образуя биения с частотой равной разности частот сигнала и гетеродина, эта частота называется промежуточной частотой (ПЧ) в . После смешения в смесителе сигнал S1 проходит через фильтр ПЧ, который блокирует сигналы всех других частот и далее демодулируется. |
Date | |
Source | Own work |
Author | Chetvorno |
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SVG genesis InfoField | This diagram was created with Inkscape, or with something else. This diagram uses translateable embedded text. |
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8 May 2017
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current | 03:19, 8 April 2019 | 957 × 724 (32 KB) | wikimediacommons>Chetvorno | Tweaked font size and placement of objects |
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Height | 204.35121mm |