Patent ID: 8022785

Claim:
A step attenuator having a reduced insertion loss at high frequencies, comprising: a printed circuit board having first and second mounting surfaces; a highpass filter network, including a high frequency circuit path mounted on the first surface of said printed circuit board and passing high frequency signals; a lowpass filter network, including an attenuator network mounted on the second surface of said printed circuit board and having input and output nodes, said lowpass filter network having a frequency response and presenting a high inductive reactance to high frequency signals at the input and the output nodes of the attenuator network; a parasitic capacitance through the printed circuit board, between the high frequency circuit path of said highpass filter network and the input and output nodes of the attenuator network, causing high frequency signals from the high frequency path to leak to the attenuator network; and a capacitive circuit, connected across the attenuator network between either the input or the output node and ground, consisting essentially of one or more capacitors and having a low reactance to the leaked high frequency signals, said capacitive circuit having a capacitance value that does not substantially affect the frequency response of said lowpass filter network, said capacitive circuit being coupled to said parasitic capacitance to draw at least some of the leaked signals away from the attenuator network and to substantially prevent their energy from being absorbed in the attenuator network, whereby a reduction of the insertion loss of said step attenuator at high frequencies is achieved.