JPH0720711U - Planar antenna - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a planar antenna in which a tuning coil for matching the impedance with the planar antenna and the planar antenna are integrally formed by a mold or the like, and the resonance frequency is adjusted by using a short rod. To aim. [Structure] A tuning coil for matching the impedance with the planar antenna and the planar antenna are integrally molded with a mold or the like, and a short rod is provided so as to be perpendicular to the planar antenna.
The planar antenna is characterized in that the resonance frequency of the antenna is adjusted by the short rod.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a keyless entry system that uses radio waves to open and close a door lock of a house or a vehicle, start an engine of a car, or turn on and off a house or a vehicle, and more specifically, in a keyless entry system. It relates to the structure of a planar antenna that can adjust the resonance frequency used in a transceiver.

[0002]

[Prior art]

 This type of keyless entry system emits radio waves when a driver pushes a button on a transmitter when he / she gets into a car, for example, and a receiver set in the car receives the radio waves to unlock the door. The door is locked by pressing the button again when getting off. As a conventional keyless entry system, the one shown in FIG. 5 is known as its structure.

In FIG. 5, reference numeral 30 is a transmitting circuit, 32 is a transmitting antenna, 34 is a receiving antenna, 4 is a receiving circuit, and 36 is a door lock opening / closing device. The reception antenna 34 receives the electric wave transmitted from the transmission antenna 32 from the transmission circuit 30 that transmits the signal for opening and closing the door lock of the vehicle, and sends it to the reception circuit 4. In the receiving circuit 4, the door lock is opened / closed by outputting a drive signal for opening / closing the door lock to the door lock opening / closing device 36.

The configuration of the receiving circuit 4 used in the keyless entry system will be described with reference to FIG. In the figure, 38 is a tuning circuit, 40 is a demodulation circuit, and 42 is an amplifier.

The signal received by the receiving antenna 34 is tuned by the tuning circuit 38, the signal from the tuning circuit 38 is input to the demodulation circuit 40, and the signal demodulated by the demodulation circuit 40 is input to the amplification device 42. The signal amplified by the amplifier 42 is output to the door lock opening / closing device 36 as a drive signal.

Next, the configuration of the keyless entry system used in the receiver will be described with reference to FIG. In the figure, 2 is a substrate, 4 is a receiving circuit, 6 is a planar antenna, and 44 is a tuning coil. The conventional planar antenna is configured by providing the receiving circuit 4 on the substrate 2 and further providing the planar antenna 6 having the tuning coil 44 on the receiving circuit 4. This planar antenna was tuned by the tuning coil 44 and the tuning circuit 38 in the receiving circuit 4.

[0007]

[Problems to be solved by the device]

 However, in the above-described conventional planar antenna, when tuning is performed by the tuning coil 44 separately provided from the planar antenna 6, the energy loss due to the tuning coil 44 is large. This energy loss adversely affects the power consumption of the entire receiving circuit and malfunctions of the door lock opening / closing device. Further, there is a problem that adjustment of the tuning coil is difficult and it takes time to adjust. Further, since many tuning coils are spring-shaped, there is a problem in that tuning is not possible due to deformation of the shape during assembly.

In view of the above problems, the present invention provides a planar antenna in which a tuning coil for matching the impedance with the planar antenna and the planar antenna are integrally formed with a mold or the like, and the resonance frequency is adjusted using a short rod. The purpose is to provide.

[0009]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention integrally molds a tuning coil for matching impedance with a flat antenna and a flat antenna with a mold or the like, and provides a short rod perpendicular to the flat antenna. The resonant frequency of the antenna is adjusted by the short rod.

[0010]

[Action]

 In the planar antenna having the above structure, the tuning coil for matching the impedance with the planar antenna and the planar antenna are integrally formed by a mold or the like, so that the spring-shaped tuning coil is not necessary. Furthermore, a short rod provided so as to be perpendicular to the antenna plays the role of a capacitor, and the resonance frequency can be adjusted by adjusting this short rod.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the same components as those of FIG. 7 showing the conventional technique are designated by the same reference numerals, and the duplicate description thereof will be omitted.

FIG. 1 is a perspective view showing a state in which a planar antenna is mounted on a substrate. In FIG. 1, 8 is a tuning coil, 10 is a short rod, 12 is a leg, and 14 is a hole.

Since the required resonance frequency is predetermined, the shape and size of the receiving circuit 4 are also uniquely determined. Therefore, the planar antenna 6 can be integrally formed with the receiving circuit 4 by using a die, wire cut, laser machining, electric discharge machining or the like.

The shaped planar antenna 6 is fixed to the substrate 2 by bending the tuning coil 8 along the line AA ′, inserting the legs 12 provided on the tuning coil 8 into the holes 14 of the substrate 2, and bending the legs. It

Next, the short rod 10 is provided on the portion of the substrate 2 corresponding to the lower surface of the planar antenna 6 so as to be perpendicular to the lower surface of the planar antenna 6. Here, the planar antenna 6 can be considered as an equivalent circuit as shown in FIG. Therefore, the resonance frequency f of the planar antenna 6 can be obtained from the equation (1). In equation (1), L1 is the inductance of the La portion, L2 is the inductance of the Lb portion, and C is the capacitance.

F = 1 / (2π√ (C (L1 + L2))) (1) FIG. 3 shows measurement points for investigating the relationship between the distance between the planar antenna 6 and the rod 10 and the resonance frequency. 4 is a diagram showing the relationship between the resonance frequency and the distance between the planar antenna 6 and the short rod 10 at the positions a, b, and c of the short rod 10 shown in FIG. As can be seen from FIG. 3, when the distance between the planar antenna 6 and the short rod 10 is changed, the same change as the previously calculated value is found. Therefore, the resonance frequency can be adjusted by changing the distance between the planar antenna 6 and the short rod 10.

[0017]

[Effect of device]

 As is apparent from the above-mentioned embodiment, the present invention can easily adjust the resonance frequency by providing the short bar so as to be perpendicular to the plane antenna. Further, by integrally molding the planar antenna and the tuning coil, the loss of energy by the tuning coil is reduced, and the variation of the resonance frequency due to the deformation of the shape during assembly or use can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of a planar antenna of the present invention.

FIG. 2 is a diagram showing a circuit equivalent to a planar antenna.

FIG. 3 is a diagram showing measurement points for examining the relationship between the resonance frequency and the distance between the planar antenna and the short rod.

FIG. 4 is a diagram showing a relationship between a distance between a planar antenna and a short rod and a resonance frequency.

FIG. 5 is a diagram showing a configuration of a conventional keyless entry system.

FIG. 6 is a diagram showing a configuration of a receiver used in a conventional keyless entry system.

FIG. 7 is a perspective view showing a configuration of a conventional planar antenna.

[Explanation of symbols]

 2 board 4 receiving circuit 6 plane antenna 8 tuning coil 10 short rod 12 leg 14 hole 30 transmitting circuit 32 transmitting antenna 34 receiving antenna 36 door lock opening / closing device 38 tuning circuit 40 demodulating circuit 42 amplifying circuit 44 tuning coil

Claims (1)

[Scope of utility model registration request] 1. A flat antenna used as a transmitter or a receiver in a device for opening and closing a door lock of a house or a vehicle, starting an engine of a vehicle, and turning on and off a house or a vehicle by using radio waves. In, the transmitter coil of the transmitter or the receiver circuit of the receiver and the tuning coil for matching the impedance of the planar antenna and the planar antenna are integrally molded with a mold or the like, and are short so as to be substantially perpendicular to the antenna. A planar antenna, wherein a rod is provided, and the resonance frequency of the antenna is adjusted by the rod.