JPS6110329Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a wireless device, and its purpose is to provide a wireless device that can always obtain efficient reception during actual use. In general, in wireless equipment that uses radio waves, when using a rod antenna on the receiver side to increase reception sensitivity and a rod antenna whose length can be changed, when receiving a single frequency, if the length of the antenna changes, the antenna impedance will change. changes. Furthermore, since the input impedance of the receiver is constant, it is necessary to match the impedances in order to receive efficiently, so it is not possible to use only antennas of a certain length. Furthermore, it is known that the receiving directivity changes depending on the length of the antenna (when placed vertically) relative to the wavelength. This invention was proposed in view of the above-mentioned drawbacks.
This will be explained below using examples. The receiver 1 is equipped with a rod antenna 2 that is connected to a built-in receiving circuit (not shown) and inputs a received signal to the receiving circuit. This rod antenna 2
It expands and contracts in multiple stages, and the length l in the fully expanded state is approximately 0.63 times the wavelength of radio waves that can be used in wireless devices, and the length in the unstretched state.
l' is set to approximately 0.3 times. In other words, from the relationship between the vertical antenna and the vertical plane pattern shown in Figure 3, the relationship between the length of the rod antenna in the horizontal direction and the radio wave strength is shown in Figure 5, and as can be seen from this graph, 0.3λ , the strength of radio waves increases at an antenna length of 0.63λ. In other words, the horizontal directivity is excellent at these antenna lengths, and even when the transmitter and receiver are used at positions apart from each other, the horizontal directivity can be large. Therefore, radio waves can be received or transmitted well in the horizontal direction.
This is particularly advantageous for wireless devices where receivers are often placed in horizontally opposed positions. By the way, about
As is clear from FIG. 4, the antenna impedance at a point that satisfies both 0.3λ and approximately 0.63λ is approximately 70Ω. Receiver 1 therefore sets its input impedance to approximately 70Ω. Note that if the length of 0.3λ is long, some mismatching may be allowed, so it can be made a little shorter. In Figure 4
Ka indicates the characteristic impedance of the antenna, and the table below shows the change in Ka depending on the length l and diameter d of the antenna.

[Table] Therefore, when the distance between the transmitter and receiver 1 is short, it is sufficient to shorten the length of rod antenna 2 to approximately 0.3λ, and conversely, when the distance between the transmitter and receiver is long, Rod antenna 2 is in a state of approximately 0.63λ.
It is better to extend the length of the signal, and efficient reception can be achieved in each state. In this invention, since the receiver is equipped with a rod antenna, the length of the antenna can be shortened when not in use, so troubles such as antenna breakage are less likely to occur. Since the impedance of each antenna in the reduced state is set to approximately the same value as the input impedance of the receiver only by changing the length of the rod antenna, there is no need to change the input impedance of the receiver to match the length of the antenna. By changing the length of the antenna according to the positional relationship between the transmitter and receiver, it has the advantage of receiving with the maximum efficiency under that condition, and does not require a loading coil. It has the advantage of being simple in structure and low in cost.

[Brief explanation of the drawing]

1 and 2 are perspective views showing the usage state of an embodiment of the present invention, and FIGS. 3, 4, and 5 are diagrams explaining the principle of the same, in which 1 is a receiver, and 2 is an antenna. It is.

Claims (1)

[Scope of claim for utility model registration] (1) A transmitter that transmits signal radio waves when a transmission switch consisting of a manual switch, sensor, etc. is turned on, and a receiver that receives radio waves from the transmitter to control a chime or electrical equipment. In a wireless device, the receiver is equipped with a rod antenna, and the antenna impedance of the rod antenna in its maximum extended state and in its most contracted state can be made approximately equal to the input impedance of the receiver only by changing the length of the rod antenna. A wireless device configured to (2) The wireless device as set forth in claim 1 of the utility model registration claim, which comprises a rod antenna set to 0.63 times the wavelength of the radio wave used in the maximum extension state and 0.3 times the wavelength of the radio wave used in the minimum contraction state.