1. Field of the Invention
The present invention relates to high frequency switches to be mounted on boards and methods of testing high frequency apparatus by means of such h-f switches.
2. Description of the Related Art
A conventional method of testing the performance of each of h-f circuits mounted on the same board includes the steps of cutting off signal conductor between the respective h-f circuits, picking up signals from the cut off portions for testing, and, after testing, filling the cut off portions with conductor for soldering. Another method includes putting earphone jack coaxial connectors in transmission lines to take signals for testing h-f circuits connected to the transmission lines. H-f switches are used to switch between built-in speakers and earphones or outside and inside antennas in the RF (coaxial) circuits of RF apparatus such as portable phones and BS or ordinary TV sets.
Such h-f switches includes a pair of parallel ground conductive plates and an non-ground conductive plate disposed between and at right angles with the parallel ground conductive plates to provide an impedance match. The switches are used to switch between two circuits A and B mounted in an apparatus without disturbing the impedance match. Consequently, it is necessary to mount two circuits (if one of them is open, then an open circuit) in the apparatus.
In addition, the outputs of the two circuits are made parallel to the board on which the h-f switch is mounted so that it is necessary to make a signal pick-up circuit to take a signal from one of the outputs or to mount the switch on an edge of the board thereby providing a large space around the output.
The above method in which the cut-off conductor portions are soldered after testing requires a large number of steps of operation. In the testing method in which an earphone jack coaxial connector is disposed on the transmission line, the coaxial connector lowers the impedance of a portion of the transmission line, causing an impedance mismatch and reflection at the connector. The connector is disposed on the transmission line without cutting the line so that it is impossible to pick up all of the signals because part of the signals still flow the transmission line.
Such problems with the above methods will be described more specifically with reference to FIGS. 1-3. In FIG. 1, an non-ground conductive plate 11a is disposed between and at right angles with parallel ground conductive plates 12a to provide an impedance match. It is known that even if the non-ground conductive plate 11a is bent as shown by broken lines, the impedance match is maintained. However, as shown in FIG. 2, when the ground conductive plates 21a are disposed in parallel to the board 23a or, as shown in FIG. 3, when the ground conductive plates 31a are disposed in perpendicular to the board, the output directions of circuits A and B are parallel to the board 23a or 33a.
That is, as shown in FIG. 4, when such a h-f switch 41a is mounted on a board 42a, the output directions of circuits A and B are parallel to the board 42a. Where the output of circuit A is a transmission line for supplying signals and signals are taken out from the output of circuit B, it is necessary to provide either a signal pick-up circuit matched to the output of the circuit B or a large space around the circuit B at the expense of other components. In addition, it is very hard to take out a signal in the direction of B or parallel to the board 42a.
In order to avoid such a problem, as shown in FIG. 5, an h-f switch 51a is mounted on an edge of a board 52a. However, this puts limits to the location of an h-f switch and makes it impossible to test all of the h-f circuits.
As shown in FIG. 6, where a coaxial connector 61a is put on a h-f transmission line 62a an impedance mismatch occurs at the location of the coaxial connector 61a, causing reflection at the location of the coaxial connector 61a. The value of transmitted signals N is equal to the value of (transmitting signals L--reflected signals R) so that the value of N decreases as the frequency or power increases.
Where signals are taken out from the coaxial connector 61a in the direction perpendicular to the board 62a, most of the transmitting signals L are transmitted as the transmitted signals N so that the value of picked-up signals M is very low. The value of the picked-up signals M also decreases as the frequency or power increases.