FULLY ELECTRONICALLY PROGRAMMABLE COMPLEX FILTER

摘要

The fully electronically programmable complex filter employs a network of current amplifiers (CAs), each CA having differential pairs biased with different tail currents, the outputs being programmed by adjusting these tail currents. Each CA has an RC circuit at its input including a resistor R and a capacitor C, and a feedback path connecting one of its outputs to the RC circuit, thereby offering independent programmability of center frequency, pole frequency, and programmable gain. Optimal gain parameters set the electronically programmable pole frequency, gain and center frequency to accommodate Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) and Terrestrial Digital Multimedia Broadcasting (T-DMB).

主权项

1. A fully electronically programmable complex filter, comprising:
a first network of current amplifiers (CAs), each of the current amplifiers respectively having an RC circuit connected to its input and a feedback path connecting a respective output to the RC circuit, the first network of current amplifiers forming a first filter having a transfer function characterized by the relation,Hp(s)=Kg/(C2R2)(s-jKc/CR)2+(s-jKc/CR)Kq/(CR)+Ko2/(C2R2), wherein ωc=Kc/CR is the center frequency, ωo=Ko/CR is the pole frequency, Q0=1/Kq is the pole quality factor, and Kg/Ko is the gain of the filter, and wherein each current amplifier has differential outputs characterized by the relations,
iz=ix izP1=izN1≈(IT2/IT1)1/2ix,where ix is input current and iz is a current source output, izP1 being a positive current mirror output, and izN1 being a negative current mirror output, thereby providing electronic programmability of the center frequency, pole frequency, quality, and CA gains, Kc, Ko, Kq and Kg via adjustment of the current source and current mirror tail currents, IT1, and IT2, respectively.