| 摘要 |
An FM receiver includes an RF section, a first mixer stage for converting a desired RF reception signal into a first IF signal having a carrier frequency located on average at a first intermediate frequency, a first IF section for selecting the first IF signal, and a second mixer stage for converting the first IF signal into a second IF signal having a carrier frequency located on average at a second intermediate frequency. The second intermediate frequency is below the first intermediate frequency. A second IF section selects the second IF signal and is coupled to an FM demodulator for demodulating the baseband modulation signal of the desired RF reception signal, followed by a low-pass filter for selecting the baseband modulation signal. In order to enhance the signal processing of the FM receiver and to realize a receiver in a largely integrated form, to provide a substantially fully integrable IF stage which is easily exchangeable with the IF section of substantially all existing FM receivers of the superheterodyne type, and to realize a selectivity considerably greater than that of known IF filters, a third mixer stage is coupled between the second IF section and the FM demodulator for converting the second IF signal to a third IF signal having a carrier frequency located on average at a third intermediate frequency which is above the second intermediate frequency.
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