Low-Pass Step Attenuator
First Claim
1. A filter circuit having a frequency response, said frequency response comprising:
- a low-pass portion at a frequency range less than a first frequency;
a flat loss portion at a frequency range between a second frequency and a third frequency; and
a high-pass portion at a frequency range higher than a fourth frequency;
the flat loss portion providing greater attenuation that the low-pass and the high-pass portions;
wherein the fourth frequency is higher than the third frequency, which is higher than the second frequency, which is higher than the first frequency.
3 Assignments
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Accused Products
Abstract
A filter circuit is constructed as a triplex filter having a high-pass filter, a low-pass filter with attenuation in the passband, and a second low-pass filter without attenuation in the passband. The filter circuit has a frequency response with a high-pass portion, a flat loss portion, and a low-pass portion. Attenuation in the flat loss portion is uniform and is predetermined via selection of filter components. The filter circuit is useful in a bidirectional CATV system in which performance is improved by selectable attenuation of a first source of return path signals but without attenuation of a second source of return path signals.
55 Citations
28 Claims
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1. A filter circuit having a frequency response, said frequency response comprising:
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a low-pass portion at a frequency range less than a first frequency; a flat loss portion at a frequency range between a second frequency and a third frequency; and a high-pass portion at a frequency range higher than a fourth frequency; the flat loss portion providing greater attenuation that the low-pass and the high-pass portions; wherein the fourth frequency is higher than the third frequency, which is higher than the second frequency, which is higher than the first frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A bidirectional communications system having a forward path to a subscriber and a return path from a subscriber, forward path signals being transmitted along the forward path and return path signals being transmitted along the return path, further comprising:
a filter circuit comprising a branch that passes forward path signals with relatively little or no attenuation, an attenuating branch that uniformly attenuates return path signals in a first frequency range, and a branch that passes return path signals in a second frequency range with relatively little or no attenuation. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A modified triplex filter comprising:
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means for passing signals below a first frequency without attenuation; means for applying uniform attenuation to frequencies between a second frequency and a third frequency; and means for passing signals above a fourth frequency without attenuation.
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- 19. A step attenuator for use in CATV applications with bidirectional communications having a forward path to a CATV subscriber and a return path from the CATV subscriber, the step attenuator including a circuit that applies flat loss to frequencies below a first frequency on said return path and passes frequencies above a second frequency higher than said first frequency on said forward path, the step attenuator further comprising a branch allowing signals from a CATV subscriber to pass without attenuation.
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22. A circuit comprising a first branch, a second branch, and a third branch, said first branch providing a no-attenuation path for signals lower than a first frequency;
- said second branch providing attenuation between a second frequency and a third frequency; and
said third branch providing a no-attenuation path for signals higher than a fourth frequency. - View Dependent Claims (23, 24, 25, 26, 27)
- said second branch providing attenuation between a second frequency and a third frequency; and
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28. A circuit for use in a two way communication system, comprising:
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an input terminal; an output terminal; a first capacitor connected between the input terminal and a first node; a first branch that passes forward path signals between the first node and a second node; a blocking capacitor connected between the second node and the output terminal; a second branch that passes return path signals with no attenuation connected between the first node and the second node; and a third branch providing attenuation for return path signals connected between the first node and the second node; wherein the third branch includes a resistive network.
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Specification