Line equalizer circuit employing active gyrator

Claim 2

An equalizer circuit comprising: input means for receiving signals from a transmission line; an operational amplifier having an inverting input terminal, a non-inverting input terminal, an output terminal and feedback means connected between said output terminal and said inverting input terminal; a first frequency-insensitive signal path connected between said input means and said inverting input terminal; and a second frequency-sensitive signal path connected between said input means and said non-inverting input terminal, said second signal path including a bandpass filter comprising capacitor means and an inductorless gyrator circuit.

Claim 3

The circuit according to claim 1 wherein said gyrator circuit is an active circuit connected in parallel with said capacitor means, said gyrator circuit comprising: first and second operational amplifiers, each having inverting and non-inverting input terminals and an output terminal; means connecting the non-inverting input terminals of both of said first and second operational amplifiers to one sidE of said capacitor means; first resistive means connected between the inverting input terminal of said first operational amplifier and the other side of said capacitor means; second resistive means connected between the output terminal and inverting input terminal of said first operational amplifier; third resistive means connected between the output terminal of said first operational amplifier and the inverting input terminal of said second operational amplifier; fourth resistive means connected between the output terminal and non-inverting input terminal of said second operational amplifier; and further capacitive means connected between the output terminal and inverting input terminal of said second operational amplifier.

Claim 4

The circuit according to claim 2 wherein said first signal path and said feedback means are resistive and have the same resistance.

Claim 5

The circuit according to claim 2 wherein said third resistive means is adjustable to permit variation of the center frequency of said bandpass filter.

Claim 6

The circuit according to claim 2 further comprising adjustable resistive means connected in series between said input means and said bandpass filter to permit variation of the delay experienced by a signal passing through said circuit.

Claim 7

The circuit according to claim 2 wherein said second signal path further comprises gain adjustment means for selectively varying the gain of said circuit.

Claim 8

The circuit according to claim 2 wherein said other side of said capacitor means is connected to ground.

Claim 9

The circuit according to claim 2 further comprising variable resistive means connected in series with said bandpass filter between said input means and ground, said variable resistive means comprising: a potentiometer; a fixed resistor; and a switch connected in parallel with said fixed resistor and selectively actuable to short out said fixed resistor.

Claim 10

An equalizer circuit for use in conjunction with a signal transmission line, said circuit comprising: a differential operational amplifier having first and second input terminals and an output terminal which provides an output voltage which is proportional to the difference between the voltage appearing across said input terminals; resistive coupling means for applying signal from said transmission line to said first input terminal; a bandpass filter circuit having input and output terminals and comprising a capacitor and an active inductorless gyrator circuit connected in parallel; coupling means for applying signal from said transmission line to said bandpass filter input terminal; and actuable switching means connected between said bandpass filter output terminals and said second input terminal to permit selective connection of said bandpass filter to said second input terminal.

Claim 11

An equalizer circuit for use in conjunction with a signal transmission line, said circuit comprising: a differential operational amplifier having first and second input terminals and an output terminal which provides an output voltage which is proportional to the difference between the voltage appearing across said input terminals; resistive coupling means for applying signal from said transmission line to said first input terminal; a bandpass filter circuit having input and output terminals and comprising a capacitor and an active inductorless gyrator circuit connected in parallel; coupling means for applying signal from said transmission line to said bandpass filter input terminal; and actuable switching means connected between said bandpass filter output terminals and said second input terminal to permit selective connection of said bandpass filter to said second input terminal.