Variable attenuator for a wave signal receiver

Claim 2

A variable attenuator for a wave signal receiver for attenuating a received carrier in response to an AGC signal and in an amount directly proportional to the carrier''s signal strength, comprising: a pi network having at least one current-controlled variableresistance diode in its series arm and also having a currentcontrolled variable-resistance diode in each of its input and output shunt arms, the resistance of each diode being inversely proportional to the magnitude of any forward bias current translated therethrough; three different DC paths from a fixed bias source to a ground plane of reference potential each of which paths includes a respective one of the three arms of said network; bias means, controlled by said AGC signal and including said DC paths, for translating through each of the diodes in said shunt arms forward bias current that varies directly with received signal strength variations and for translating through each diode in said series arm forward bias current that changes inversely with received signal strength variations; and means for applying said carrier across said input shunt arm and means for deriving it in attenuated form across said output shunt arm.

Claim 3

A variable attenuator according to claim 1 in which said series arm includes a plurality of variable-resistance diodes series-connected in aiding polarity to minimize the capacitance in said series arm thereby to maximize the attenuation obtainable with said attenuator.

Claim 4

A variable attenuator according to claim 1 in which said bias means includes a variable-resistance device connected in series in one of said DC paths, and in which said AGC signal controls said variable-resistance device to simultaneously vary the direct current in all three of said DC paths.

Claim 5

A variable attenuator for a wave signal receiver for attenuating a received carrier in response to an AGC signal and in an amount directly proportional to the carrier''s signal strength, comprising: a pi network having at least one current-controlled variable-resistance diode in its series arm and also having a current-controlled variable-resistance diode in each of its input and output shunt arms, the resistance of each diode being inversely proportional to the magnitude of any forward bias current translated therethrough; means including a voltage divider for applying a forward bias voltage to each of the diodes in said shunt arms to translate forward bias current therethrough; a series arrangement, including a variable-resistance device and said series arm, connected across a portion of said voltage divider for translating forward bias current through each diode in said series arm; means for applying said AGC signal to said variables resistance device to vary the bias current in the diodes in said shunt arms directly with received signal-strength variations and to vary the bias current in each diode in said series arm inversely with received signal strength variations; and and means for applying said carrier across said input shunt arm and means for deriving it in attenuated form across said output shunt arm.

Claim 6

A variable attenuator for a wave signal receiver for attenuating a received carrier in response to an AGC signal and in an amount directly proportional to the carrier''s signal strength, comprising: a pi network having at least one current-controlled variable-resistance diode in its series arm and also having a current-controlled variable-resistance diode in each of its input and output shunt arms, the resistance of each diode being inversely proportional to the magnitude of any forward bias current translated therethrough; means including a voltage divider for applying a forward bias voltage to each of the diodes in said shunt arms to translate forward bias current therethrough; a series arrangement, including a variable-resistance device and said series arm, connected across a portion of said voltage divider for translating forward bias current through each diode in said series arm; means for applying said AGC signal to said variables resistance device to vary the bias current in the diodes in said shunt arms directly with received signal-strength variations and to vary the bias current in each diode in said series arm inversely with received signal strength variations; and and means for applying said carrier across said input shunt arm and means for deriving it in attenuated form across said output shunt arm.

Claim 7

A variable attenuator according to claim 4 in which said shunt arms, as to DC are connected in parallel, and in which that parallel combination is connected across part of said portion of said voltage divider.

Claim 8

A variable attenuator according to claim 4 in which said variable-resistance device is a transistor having a base, an emitter and a collector, and in which the emitter-collector conduction path of said transistor is connected in series with said series arm.

Claim 9

A variable attenuator according to claim 4, in which said series arm includes two current-controlled variable-resistance diodes connected in series with aiding polarity.

Claim 10

A variable attenuator according to claim 4, in which said bias means includes transistor with base, emitter and collector electrodes, said AGC signal is applied to said base electrode, and the variable-resistance diodes in said shunt arms are connected to one of the remaining electrodes of said transistor while the diodes or diodes in said series arm are connected to the other of such remaining electrodes.

Claim 11

A variable attenuator according to claim 4, which further comprises means for minimizing leakage reactance in said series arm to maximize the attenuation obtainable with said attenuator.