Diplex circuit forming bandstop filter

• US 6,737,935 B1
• Filed: 12/03/2002
• Issued: 05/18/2004
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: PPC Broadband Incorporated (Belden Inc.)
• Original Assignee: John Mezzalingua Associates Incorporated
• Inventors: Shafer, Steven
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US10/309,376
• Publication Number:
  US 20040104786A1
• Time in Patent Office: 532 Days
• Field of Search: 333/132, 333/167, 333/175, 333/176, 333/185, 725/128
• US Class Current: 333/132
• CPC Class Codes: H01P 1/20 Frequency-selective devices, e.g. filters
• CPC Class Codes: H03H 1/0007 of radio frequency interference filters
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/166 Passage/non-passage of the television signal, e.g. jamming, band suppression scrambling and descrambling H04N7/167

Abstract

A bandstop filter for use in CATV applications is formed by a pair of diplexers, a lowpass filter and a highpass filter. Signals having a frequency range of, e.g., 0-3 GHz enter at a first node connected to the inputs of both the lowpass and highpass filters. Signals having frequencies below a first, predetermined value pass through the lowpass filter, and signals having frequencies above a second, predetermined value pass through the highpass filter with signals having frequencies between the first and second values being blocked, i.e., “stopped.” The outputs of both the lowpass and highpass filters are connected to the second diplexer at a second node which is connected to the single output.

Claims

1. A bandstop filter for CATV applications having an input for receiving signals having frequencies in a predetermined range and an output carrying signals having frequencies below a first value within said range and above a second value, higher than said first value, within said range with signals having frequencies between said first and second values being blocked from reaching said output, said filter comprising:

a) a first diplexer to which said input is connected at a first node;

b) a lowpass filter having a first input end connected to said first node and a first output end, said lowpass filter having components between said first input and output ends which pass signals having frequencies below said first value and block signals having frequencies above said first value;

c) a highpass filter having a second input end connected to said first node and a second output end, said highpass filter having components between said second input and output ends which pass signals having frequencies above said second value and block signals having frequencies below said second value; and

d) a second diplexer having a second node to which said first output end of said lowpass filter, said second output end of said highpass filter and said output are all connected.

2. The bandstop filter of claim 1 wherein said components of each of said lowpass and highpass filters comprise a plurality of inductors and capacitors.

3. The bandstop filter of claim 2 wherein said components are all of the surface mount type and are mounted on a single printed circuit board.

4. The bandstop filter of claim 3 wherein said circuit board has opposite, major surfaces and said components of said lowpass filter are mounted upon one surface and said components of said highpass filter are mounted upon the opposite surface of said printed circuit board.

5. The bandstop filter of claim 3 and further including a housing and means for mounting said circuit board within said housing.

6. The bandstop filter of claim 5 and further including a secure grounding connection between said components and said housing.

7. The bandstop filter of claim 6 wherein said housing has a diameter of no greater than 0.820 inches.

8. The bandstop filter of claim 6 wherein said grounding connection comprises at least one elongated grounding bus on said circuit board which is in electrical communication with said housing over substantially the full length of said grounding bus.

9. The bandstop filter of claim 5 wherein said housing includes two portions which are mutually joined by a force fit of one of said portions into the other.

10. The bandstop filter of claim 9 wherein said two portions form a hollow, substantially cylindrical structure.

11. The bandstop filter of claim 10 wherein said force fit compresses one of said two portions into electrical communication with each of said lowpass and highpass filters.

12. The bandstop filter of claim 11 wherein said circuit board has opposite, major surfaces, said components of said lowpass filter are mounted upon one surface and said components of said highpass filter are mounted upon the opposite surface of said printed circuit board, and further including a first grounding bus mounted upon said one surface and electrically communicating with said lowpass filter and with said housing, and a second grounding bus mounted upon said opposite surface and electrically communicating with said highpass filter and with said housing.

13. The bandstop filter of claim 11 wherein said circuit board includes first and second, parallel, elongated edges, and said first and second grounding buses extend along said first and second edges, respectively.

14. A bandstop filter for CATV applications comprising:

a) a signal input terminal for receiving RF signals having frequencies in a predetermined range;

b) first filter means for receiving signals from said input terminal and passing to a first filter output signals having frequencies below a first value within said predetermined range and blocking signals having frequencies above said first value;

c) second filter means for receiving signals from said input terminal and passing to a second filter output signals having frequencies above a second value, higher than said first value, within said predetermined range and blocking signals having frequencies below said second value, whereby said RF signals from said input terminal are separated by said first and second filter means into different frequency bands; and

d) a signal output terminal connected to both said first and second outputs, whereby said RF signals which pass said first and second filter means are combined at said output terminal.

15. The bandstop filter of claim 14 wherein said first filter means comprise a lowpass filter.

16. The bandstop filter of claim 15 wherein said second filter means comprise a highpass filter.

17. The bandstop filter of claim 16 wherein said first and second filter means each comprise a plurality of inductors and capacitors.

18. The bandstop filter of claim 17 wherein all of said inductors and capacitors are surface mounted upon a single printed circuit board.

19. The bandstop filter of claim 18 wherein said inductors and capacitors of said first filter means are mounted on one surface of said board and said inductors and capacitors of said second filter means are mounted on the opposite surface of said board.

20. The method of communicating RF signals having frequencies below a first value and above a second value while blocking signals having frequencies between said first and second values, said method comprising:

a) connecting a first plurality of electronic components to form a first filter circuit having a first input and a first output, said first filter circuit being operative to pass RF signals applied to said first input which have frequencies below a first value and to block signals having frequencies above said first value;

b) connecting a second plurality of electronic components to form a second filter circuit having a second input and a second output, said second filter circuit being operative to pass RF signals applied to said second input which have frequencies above a second value, higher than said first value, and to block signals having frequencies below said second value;

c) connecting said first and second inputs and a single input line carrying RF signals together at a first node to form a first diplexer; and

d) connecting said first and second outputs and a single output line together at a second node to form a second diplexer, whereby said first and second filter circuits are connected in parallel and said first and second diplexers are in series.

21. The method of claim 20 wherein said diplexers are frequency selective.

22. The method of claim 20 wherein said first and second pluralities of electronic components are surface mounted upon first and second, opposite surfaces, respectively, of a single printed circuit board.