| 摘要 |
A band pass filter (1) comprises an air filled aluminium chamber (2), having a lid (3) and a cuboid resonant cavity (4) having a central iris (5). At opposite end nodes of the cavity, perfect electric conductors (PECs) (6, 7) are provided. One is connected to a feed wire (8) from an input (9) at one end of the cavity. The other PEC is connected via a further feed (10) wire to a radiator (11) in an adjacent wave guide (12). Threaded tuning productions (14, 15) opposite the PECs and (16) in the iris are provided, whereby the pass band and the transmission characteristics of the filter in the pass band can be tuned to match the input impedance of the band pass filter and the wave guide to the output impedance of a microwave drive circuit (not shown). Typically the impedance will be 507. The wave guide (12) is of ceramic and metallised on its outer surfaces. It is mounted on one end of the filter chamber, with an electrodeless bulb (21) in a central cavity (22) directed axially away from the chamber and the radiator in a further cavity (23) set to one side of the central cavity. When the filter is driven, the wave guide resonates driving the bulb. |
