| 摘要 |
A COUPLING CIRCUIT (22) FOR A RADIOFREQUENCY (RF) RECEIVER (10) HAS AN ATTENUATOR (38) AND A RESONATOR (40). THREE RESISTORS (42,44,46) OF ATTENUATOR (38) PROVIDE A LOSSY RESISTIVE ISOLATION BETWEEN A FIRST MIXER (20) AND A CRYSTAL FILTER (24) OF RF RECEIVER (10) FOR UNDESIRED SIGNALS SUCH AS NOISE AND HARMONICS. THUS, SIGNAL REFLECTIONS BETWEEN FIRST MIXER (20) AND CRYSTAL FILTER (24) ARE ABSORBED FOR THESE UNDESIRED SIGNALS. HOWEVER, FOR DESIRED SIGNALS AT AN INTERMEDIATE FREQUENCY (IF), RESONATOR (40) HAS AN INDUCTOR (54) AND A CAPACITOR (56) TO RESONATE WITH SUCH DESIRED SIGNALS AT THE IF. AS A RESULT OF RESONANCE, RESISTORS (42,46) ARE ISOLATED TO ALLEVIATE ATTENUATION OF THE DESIRED SIGNALS. (FIGURE 2)
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