| 摘要 |
Receiver comprising a resonance amplifier for selectively amplifying a modulated carrier signal being coupled to signal demodulation means for narrow band demodulation. Said resonance amplifier comprising a cascade of first and second transconductance amplifiers (TC1, TC2) being included in a loop, outputs thereof being coupled via first and second parallel RC filters (R1C1; R2C2) to inputs of the second and first transconductance amplifiers (TC1, TC2), respectively, said loop also includes means for signal inversion (INV). Inputs and outputs of third and fourth transconductance amplifiers (TC3, TC4) are coupled to outputs of said first and second transconductance amplifiers (TC1, TC2), respectively, to effectuate a negative resistance value across said first and second parallel RC filters (R1C1, R2C2), respectively, varying with the gain of said third and fourth transconductance amplifiers (TC3, TC4), fifth and sixth transconductance amplifiers (TC5, TC6) are coupled between inputs and outputs of said resonance amplifier. In order to reduce the overall noise figure of the receiver, said AGC signal generating means derive first and second control signals (Iq, Id) from said first DC signal (A), said control signals (Iq, Id) being supplied to gain control inputs of said third to sixth transconductance amplifiers (TC3, TC4, TC5, TC6).
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