1. A tank having:
a filter which divides the tank into upper and lower portions;
a fluid inlet in the lower portion for admitting into the tank a fluid with entrained solids; and
a fluid outlet in the upper portion through which filtered fluid can leave the tank,
characterized in that the filter comprises:
filter media supported on a permeable wall, the wall including a filter media outlet which is normally closed; and
opening means for opening the filter media outlet to allow the filter media to discharge into the lower portion of the tank.
2. A tank as claimed in claim 1, in which the wall of the filter is substantially conical, tapering downwardly to the filter media outlet.
3. A tank as claimed in claim 1, in which the opening means for opening the filter media outlet comprises a valve in the said filter media outlet.
4. A tank as claimed in claim 1, in which means is provided for operating the opening means remotely.
5. A tank as claimed in claim 1, in which a baffle is provided adjacent the fluid inlet to direct the flow of fluid and entrained solids away from the filter.
6. A tank as claimed in claim 5, in which the baffle is annular and induces a cyclonic flow in the fluid and entrained solids entering the tank.
7. A tank as claimed in claim 1, in which the permeability of the wall is provided by perforations in the wall.
8. A tank as claimed in claim 7, in which the wall comprises a mesh sheet.
9. A tank as claimed in claim 1, in which the wall is formed from a plurality of individual screens.
10. A tank as claimed in claim 1, in which a filter media inlet is provided in the tank above the filter.
11. A tank as claimed in claim 1, in which a second filter media outlet is provided in the tank below the filter.
12. A tank as claimed in claim 1, in which a fluidising unit is provided in the lower portion of the tank.
13. A tank as claimed in claim 12, in which the fluidising unit discharges fluidised solids from the tank through a solids discharge duct.
14. A tank as claimed in claim 12, in which the filter media discharged from the filter into the lower portion of the tank is removed from the tank by the fluidising unit.
15. A tank as claimed in claim 12, in which the fluidising unit is fed with fluid from a second tank.
16. A tank as claimed in claim 1, in which back flushing means are provided for back flushing the filter media.
17. A method as claimed in claim 16, in which the back flushing means comprises a flow distribution device which distributes a flushing fluid over an upper surface of the filter media.
18. A method as claimed in claim 16, in which the back flushing means is fed with fluid from the second tank.
19. A tank as claimed in claim 18, in which the flushing fluid is water.
20. A method of refilling a filter in a tank with filter media, the method comprising the steps of:
(a) discharging the used filter media into a lower portion of the tank;
(b) fluidising the used filter media and transporting it out of the tank using a fluidising unit; and
(c) refilling the filter with filter media.
21. A method as claimed in claim 20, in which between steps (a) and (b) there is a further step of back flushing the filter to wash out the used filter media.
22. A method as claimed in claim 20, in which between the steps (b) and (c) there is a further step of cleansing the filter media in a cleanser, such as a cyclone, and in the step (c), the filter is refilled with the cleansed filter media.
23-24. (canceled)
25. A tank having:
a filter which divides the tank into upper and lower portions;
a fluid inlet in the lower portion for admitting into the tank a fluid with entrained solids; and
a fluid outlet in the upper portion through which filtered fluid can leave the tank,
characterized in that the filter comprises:
filter media supported on a permeable wall, the wall including a filter media outlet which is normally closed, where the wall is substantially conical, tapering downwardly to the filter media outlet, and where the wall comprises a feature selected from the group consisting of perforations in the wall, a mesh sheet, a plurality of individual screens and combinations thereof; and
opening means for opening the filter media outlet to allow the filter media to discharge into the lower portion of the tank.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1-17. (canceled)
18. A bandpass filter, comprising:
a plurality of resonators that are electromagnetically coupled to each other, each resonator having a terminal coupled to a ground;
a bypass line in parallel with said plurality of resonators, said bypass line having a bypass line input coupled to a first resonator of said plurality of resonators and a bypass line output coupled to a second resonator of said plurality of resonators;
an input, coupled to said first resonator; and
an output, coupled to said second resonator;
said bypass line electromagnetically coupled to said first resonator and said second resonator, and electromagnetically isolated from at least one of said plurality of resonators between said first and second resonators.
19. The bandpass filter of claim 18, wherein said plurality of resonators are spiral resonators.
20. The bandpass filter of claim 18, wherein said resonators are quarter wavelength transmission lines.
21. The bandpass filter of claim 20, wherein said quarter wavelength transmission lines are microstrip transmission lines.
22. The bandpass filter of claim 18, further comprising:
an input capacitor coupled between said input and said first resonator; and
an output capacitor coupled between said output and said second resonator.
23. The bandpass filter of claim 22, wherein said input capacitor and said output capacitor are printed finger capacitors.
24. The bandpass filter of claim 22, further comprising:
a bypass line input coupler, coupled between said bypass line and said first resonator; and
a bypass line output coupler, coupled between said bypass line and said second resonator.
25. The bandpass filter of claim 24, wherein said plurality of resonators includes a third resonator coupled between said first resonator and said second resonator.
26. The bandpass filter of claim 25, further comprising:
a first intercoupler that weakly couples said first resonator to said third resonator; and
a second intercoupler that weakly couples said third resonator to said second resonator.
27. The bandpass filter of claim 25, further comprising:
a substrate, wherein said plurality of resonators, said bypass line, said input capacitor, said output capacitor, said bypass line input coupler, and said bypass line output coupler are printed on said substrate.
28. The bandpass filter of claim 27, further comprising:
a plurality of ground vias that couple said terminals of said plurality of resonators to said ground,
wherein said ground is located on the opposite side of said substrate as said plurality of resonators, said bypass line, said input capacitor, said output capacitor, said bypass line input coupler, and said bypass line output coupler.
29. The bandpass filter of claim 28, further comprising:
a first land pattern;
a second land pattern;
a first land pattern via that couples said input to said first land pattern; and
a second land pattern via that couples said output to said second land pattern,
wherein said first and second land patterns are located on the opposite side of said substrate as said plurality of resonators, said bypass line, said input capacitor, said output capacitor, said bypass line input coupler, and said bypass line output coupler.
30. The bandpass filter of claim 29, wherein said first and second land patterns are on the same side of said substrate as said ground and separate from said ground where necessary to couple a first signal carrying element from said input to said first land pattern and to couple a second signal carrying element from said output to said second land pattern.
31. The bandpass filter of claim 30, wherein said first and second land patterns are coupled to said ground where necessary to connect said ground to a printed circuit board on which said first and second land patterns are landed.
32. The bandpass filter of claim 18, wherein said bypass line has a substantially constant trace width.
33. A bandpass filter comprising:
an input coupled to an input capacitor;
an output coupled to an output capacitor;
a first resonator coupled to a ground, said input capacitor, a first intercoupler and a bypass line input coupler;
a second resonator coupled to said ground, a second intercoupler, a bypass line output coupler, and said output capacitor;
a third resonator coupled to said ground, said first intercoupler, and said second intercoupler, wherein said first resonator, said second resonator and said third resonator are electromagnetically coupled; and
a bypass line coupled between said bypass line input coupler and said bypass line output coupler, wherein said bypass line has a length configured to produce a signal that attenuates an image channel at said output and therefore causes improved image channel rejection at said output, and wherein said bypass line is electromagnetically isolated from said third resonator.
34. The bandpass filter of claim 33, wherein said first, second, and third resonators are spiral resonators.
35. The bandpass filter of claim 33, wherein said first, second, and third resonators are quarter wavelength transmission lines.
36. The bandpass filter of claim 33, wherein said bypass line input coupler is formed from an outer segment of said first resonator that is in parallel with a first portion of said bypass line, said bypass line output coupler is formed from an outer segment of said second resonator that is in parallel with a second portion of said bypass line, and a third portion of said bypass line is coupled between said first portion and said second portion.
37. The bandpass filter of claim 36, wherein said first, second, and third portions of said bypass line have a substantially constant trace width.
38. The bandpass filter of claim 33, wherein said input capacitor and said output capacitor are printed finger capacitors.
39. The bandpass filter of claim 33, wherein said signal produced by said bypass line is out-of-phase with said image channel.
40. The bandpass filter of claim 33, further comprising:
a first ground via that couples said first resonator to said ground;
a second ground via that couples said second resonator to said ground; and
a third ground via that couples said third resonator to said ground,
wherein said ground is located on the opposite side of a substrate as said first resonator, said second resonator, said third resonator, said bypass line, said input capacitor, said output capacitor, said bypass line input coupler, and said bypass line output coupler.
41. The bandpass filter of claim 40, further comprising:
a first land pattern;
a second land pattern;
a first land pattern via that couples said input to said first land pattern; and
a second land pattern via that couples said output to said second land pattern,
wherein said first and second land patterns are located on the opposite side of said substrate as said first resonator, said second resonator, said third resonator, said bypass line, said input capacitor, said output capacitor, said bypass line input coupler, and said bypass line output coupler.
42. The bandpass filter of claim 41, wherein said first and second land patterns are on the same side of said substrate as said ground and separate from said ground where necessary to couple a first signal carrying element from said input to said first land pattern and to couple a second signal carrying element from said output to said second land pattern.
43. The bandpass filter of claim 42, wherein said first and second land patterns are coupled to said ground where necessary to connect said ground to a printed circuit board on which said first and second land patterns are landed.
44. A differential bandpass filter, comprising:
a first plurality of resonators that are electromagnetically coupled to each other, each resonator having a terminal coupled to a ground;
a first bypass line, in parallel with said first plurality of resonators, said first bypass line having a first bypass line input coupled to a first resonator and a first bypass line output coupled to a second resonator;
a first input, coupled to said first resonator;
a first output, coupled to said second resonator;
a second plurality of resonators that are electromagnetically coupled to each other, each resonator having a terminal coupled to said ground;
a second bypass line, in parallel with said second plurality of resonators, said second bypass line having a second bypass line input coupled to a third resonator and a second bypass line output coupled to a fourth resonator;
a second input, coupled to said third resonator; and
a second output, coupled to said fourth resonator;
said first bypass line electromagnetically coupled to said first resonator and said second resonator, and electromagnetically isolated from at least one of said first plurality of resonators between said first and second resonators;
said second bypass line electromagnetically coupled to said third resonator and said fourth resonator, and electromagnetically isolated from at least one of said second plurality of resonators between said third and fourth resonators; and
said first input and said second input forming a differential input capable of receiving a differential signal, said first output and said second output forming a differential output capable of producing a differential signal.
45. The differential bandpass filter of claim 44, wherein said first and second plurality of resonators are spiral resonators.
46. The differential bandpass filter of claim 44, wherein said first bypass line has a substantially constant trace width, and said second bypass line has a substantially constant trace width.
47. A double conversion tuner, comprising:
a tuner input;
a first variable gain amplifier, coupled to said tuner input;
a first mixer coupled to a first local oscillator and said first variable gain amplifier;
a printed bandpass filter, coupled between said first mixer and a second mixer, including
a plurality of resonators that are electromagnetically coupled to each other, each resonator having a terminal coupled to a ground;
a bypass line, in parallel with said plurality of resonators, said bypass line having a bypass line input coupled to a first resonator and a bypass line output coupled to a second resonator, said bypass line electromagnetically coupled to said first resonator and said second resonator, and electromagnetically isolated from at least one of said plurality of resonators between said first and second resonators;
a bandpass filter input coupled to an output of said first mixer; and
a bandpass filter output coupled to an input of said second mixer;
a second local oscillator, coupled to said second mixer;
a second intermediate frequency (IF) bandpass filter coupled to said second mixer and a second variable gain amplifier; and
a tuner output, coupled to said second variable gain amplifier.
48. The double conversion tuner of claim 47, wherein said plurality of resonators are spiral resonators.
49. The double conversion tuner of claim 47, wherein said bypass line has a substantially constant trace width.
50. The double conversion tuner of claim 47, wherein said printed bandpass filter is a differential bandpass filter.