Step attenuator circuit with improved insertion loss

In a step attenuator circuit, mounted on a printed circuit board, of the type in which a highpass filter network passes high frequency signals, and a lowpass filter network passes low frequency signals and presents a high shunt reactance to the high frequency signals, the lowpass filter network including an attenuator network, having input and output nodes, which attenuates the low frequency signals by a specified amount, and in which there is a parasitic capacitance between the highpass filter network and the attenuator network, causing an amount of electrical energy from the high frequency signals to be absorbed by the attenuator network, wherein the improvement comprises:

• a first capacitive circuit connected across the attenuator network between the input node and ground;
• and
• a second capacitive circuit connected across the attenuator network between the output node and ground, said first and said second compensation circuits being coupled to the parasitic capacitance, whereby the amount of electrical energy from the high frequency signals that is absorbed by the attenuator network is reduced.

In a step attenuator circuit, mounted on a printed circuit board, of the type in which a highpass filter network passes high frequency signals, and a lowpass filter network passes low frequency signals and presents a high shunt reactance to the high frequency signals, the lowpass filter network including an attenuator network, having input and output nodes, which attenuates the low frequency signals by a specified amount, and in which there is a parasitic capacitance between the highpass filter network and the attenuator network, causing an amount of electrical energy from the high frequency signals to be absorbed by the attenuator network, wherein the improvement comprises:

• a first capacitive circuit, connected across the attenuator network between either the input or the output node and ground, and coupled to the parasitic capacitance to form a voltage divider with the parasitic capacitance, said first capacitive circuit having a capacitance value in the range of about 0.5 pF to about 11 pF, whereby the amount of electrical energy from the high frequency signals absorbed by the attenuator network is reduced.

In a step attenuator circuit, mounted on a printed circuit board, of the type in which a highpass filter network passes high frequency signals, and a lowpass filter network passes low frequency signals and presents a high shunt reactance to the high frequency signals, the lowpass filter network including an attenuator network, having first and second signal nodes, which attenuates the low frequency signals by a specified amount, and in which there is a parasitic capacitance between the highpass filter network and the attenuator network, causing an amount of electrical energy from the high frequency signals to be absorbed by the attenuator network, the parasitic capacitance having a first capacitance value between the highpass filter and the first signal node of the attenuator network, wherein the improvement comprises:

• a first capacitive circuit connected across the attenuator network, between the first signal node and ground, and coupled to the parasitic capacitance to form a voltage divider with the parasitic capacitance, said first capacitive circuit having a capacitance value of at least the first capacitance value of the parasitic capacitance, whereby the amount of electrical energy from the high frequency signals absorbed by the attenuator network is reduced.