Circuit arrangement for reducing spurious signals picked up by transmission line

Claim 2

A circuit arrangement for reducing spurious signals picked up by a coaxial transmission line having an inner conductor and an outer screen connected directly to a following signal transmission path, the circuit arrangement including resistive means connected from ground to the outer screen, adjacent the connection to the following signal transmission path, an inverting amplifier connected to the resistive means to derive therefrom a voltage proportional to the current flowing in the outer screen due to the spurious signals and to produce a compensating current, the amplifier including an amplifying element with a single output connection, the connection being from the output electrode to the inner conductor for the derivation of the supply current for the electrode therefrom and the application of the compensating current to the inner conductor where it is connected to the following signal transmission path so as to reduce the spurious signal current in the following signal transmission path.

Claim 3

A circuit arrangement for reducing spurious signals picked up by a coaxial transmission line having an inner conductor and an outer screen connected directly to a following signal transmission path, the circuit arrangement including resistive means connected from ground to the outer screen, adjacent the connection to the following signal transmission path, an inverting amplifier connected to the resistive means to derive therefrom a voltage proportional to the current flowing in the outer screen due to the spurious signals and to produce a compensating current, the amplifier including an amplifying element with a single output connection, the connection being from the output electrode to the inner conductor for the derivation of the supply current for the electrode therefrom and the application of the compensating current to the inner conductor where it is connected to the following signal transmission path so as to reduce the spurious signal current in the following signal transmission path.

Claim 4

A circuit arrangement for reducing spurious signals picked up by a coaxial transmission line having an inner conductor and an outer screen connected directly to a following signal transmission path, the circuit arrangement including resistive means connected from ground to the outer screen, adjacent the connection to the following signal transmission path, an inverting amplifier connected to the resistive means to derive therefrom a voltage proportional to the current flowing in the outer screen due to the spurious signals and to produce a compensating current, the amplifier including an amplifying element with a single output connection, the connection being from the output electrode to the inner conductor for the derivation of the supply current for the electrode therefrom and the application of the compensating current to the inner conductor where it is connected to the following signal transmission path so as to reduce the spurious signal current in the following signal transmission path.

Claim 5

''''A circuit arrangement for reducing spurious signals picked up by a coaxial transmission line having an inner conductor and an outer screen the inner conductor being connected directly to a following signal transmission path, the circuit arrangement including resistive means connected between the outer screen and ground, an inverting amplifier connected to the resistive means to derive therefrom a voltage proportional to the current flowing in the outer screen due to the spurious signals and to produce a compensating current, and means for feeding the compensating current to the inner conductor at a position adjacent to the connection of the resistive means to the outer screen so as to reduce the spurious signal currents in the following signal transmission path, in which the resistive means comprises a potentiometer having a resistive track and wiper of which the track is connected from the outer screen to ground and the wiper is connected to the input of the inverting amplifier, whereby the compensating current can be adjusted by adjustment of the position of the wiper.

Claim 6

''''A circuit arrangement for reducing spurious signals picked up by a coaxial transmission line having an inner conductor and an outer screen the inner conductor being connected directly to a following signal transmission path, the circuit arrangement including resistive means connected between the outer screen and ground, an inverting amplifier connected to the resistive means to derive therefrom a voltage proportional to the current flowing in the outer screen due to the spurious signals and to produce a compensating current, and means for feeding the compensating current to the inner conductor at a position adjacent to the connection of the resistive means to the outer screen so as to reduce the spurious signal currents in the following signal transmission path, in which the resistive means comprises a potentiometer having a resistive track and wiper of which the track is connected from the outer screen to ground and the wiper is connected to the input of the inverting amplifier, whereby the compensating current can be adjusted by adjustment of the position of the wiper.

Claim 7

An arrangement according to claim 2, in which the amplifier includes a transistor of which the collector is connected to the center conductor, the emitter is connected to a d.c. supply and the base is coupled to the wiper of the potentiometer.

Claim 8

An arrangement according to claim 3, in which the base electrode of the transistor is coupled to the wiper of the potentiometer through an a.c. coupling circuit having a time constant greater than one second.

Claim 9

An arrangement according to claim 4, in which the a.c. coupling circuit has a time constant of greater than ten seconds.

Claim 10

An arrangement according to claim 5, in which the amplifier includes a field effect transistor input stage and the a.c. coupling circuit is connected from the wiper of the potentiometer to the gate electrode of the field effect transistor.

Claim 11

An arrangement according to claim 6, in which the amplifier includes a negative feedback circuit thereby to increase the input impedance of the field effect transistor.

Claim 12

An arrangement according to claim 2, in which the amplifier includes one or more frequency dependent networks for compensating for variation in the ratio of spurious signal currents induced in the inner and outer conductors of the line with frequency.

Claim 13

An arrangement according to claim 2, including means for attenuating signals of relatively high frequency which would otherwise be fed by the amplifier to the central conductor and cause distortion of the signals to be transmitted by the line.