| 摘要 |
A radio pager receives a paging signal with a halfsize microstrip antenna. A pair of electrical conductive elements sandwich a printed circuit board on which elements constituting pager circuitry are mounted. The conductive elements and conductive connecting pins fastening them constitute an electromagnetic shield case for the circuitry elements, reducing the radiation of unnecessary electromagnetic waves to the outside from the circuitry mounted on the printed circuit board, in particular from a local oscillation circuit. Since the antenna has an earth plate thereof connected to one of the conductive plates with respect to high frequency, the conductive plate plays the role of an extension of the earth plate at the same time. As a result, a microstrip base plate is miniaturized while the space available for parts is increased. A ground conductive portion surrounds the antenna element and conceals screws and other conductive structural parts, whereby the antenna directivity pattern is not susceptible to changes in the dimension and position of the conductive structural parts. The conductor of the antenna element may be formed with slits to further miniaturize the antenna element and, therefore, the entire pager.
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