| 摘要 |
PROBLEM TO BE SOLVED: To provide a miniaturized and inexpensive radio equipment by making a line from an antenna reception branching point to an antenna switch terminal into the microstrip line having the 1/4 wavelength line length of desired passing frequency and turning the OFF terminal of the antenna switch terminal into a short-circuiting mode. SOLUTION: When antenna switch terminals (g) and (b) of an antenna switch 3 are turned on, an antenna switch terminal (c) of an antenna switch 4 becomes the OFF terminal and is turned into the short-circuiting mode. Then, since a line Lac from an antenna reception branching point (a) to the antenna switch terminal (c) becomes a top end short-circuiting stub, the branching point (a) away from the terminal (c) forλrf/4 (theλrf in the expression is the wavelength of a radio frequency Frf on a substrate) becomes a band pass filter for passing the desired frequency Frf, and an unwanted frequency component such as forming an image band can be prevented being fetched from an antenna 1. Thus, space saving and cost down in a filtering function can be attained.
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