| 摘要 |
Receiver comprising a resonance amplifier for selectively amplifying a modulated carrier signal being coupled to signal demodulator for narrow band demodulation. The resonance amplifier comprising a cascade of first and second transconductance amplifiers (TC 1 , TC 2 ) being included in a loop, outputs thereof being coupled via first and second parallel RC filters (R 1 C 1 ; R 2 C 2 ) to inputs of the second and first transconductance amplifiers (TC 1 , TC 2 ), respectively, the loop also includes a signal inverter (INV) for signal inversion. Inputs and outputs of third and fourth transconductance amplifiers (TC 3 , TC 4 ) are coupled to outputs of the first and second transconductance amplifiers (TC 1 , TC 2 ), respectively, to effectuate a negative resistance value across the first and second parallel RC filters (R 1 C 1 , R 2 C 2 ), respectively, varying with the gain of the third and fourth transconductance amplifiers (TC 3 , TC 4 ), fifth and sixth transconductance amplifiers (TC 5 , TC 6 ) are coupled between inputs and outputs of the resonance amplifier. In order to reduce the overall noise figure of the receiver, the AGC signal generator derives first and second control signals (Iq, Id) from the first DC signal (A), the control signals (Iq, Id) being supplied to gain control inputs of the third to sixth transconductance amplifiers (TC 3 , TC 4 , TC 5 , TC 6 ).
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