BROADCASTING WAVE RECEPTION ANTENNA

Abstract: A broadcasting wave reception antenna used in cars have a magnetic core (1) having multiple radial projections (2) extending on a common plane, and respective projections are provided with coils (3) wound on them.

Description: This invention relates to an antenna for receiving broadcasting waves, and more particularly to a magnetic antenna which is installed in a desired interior position of a car and not in the exterior thereof and which ensures wider-band, nondirectional highly-sensitive and reliable reception of broadcasting waves including AM, FM and TV bands. Most antennas heretofore used in cars were pole-type antennas configured to project to the exterior of the car during signal reception. Such an outwardly projecting configuration often invites its destruction. Such a prior art antenna is not configured to receive all different broadcasting bands, i.e. AM, FM and TV bands, and a car requires two or more antennas for reception of different bands. Many antennas outwardly projecting from the car body usually spoil the car appearance. In order to improve the appearance, some cars are provided with a glass antenna. However, since such a glass antenna, although expensive, is not configured to receive all different bands, a single car must use pole-type antennas in addition to the glass antenna in most cases. There is another antenna of this type which is disclosed in Japanese Utility Model Laying-Open Publication No. 62-75615 which uses ferrite bars having pickup coils wound thereon to pick up a high frequency signal induced in a car roof or other body portion of the car at the boundary between the roof and a pillar portion. However, since signals passing from the roof to the pillar portion, if any, are weak waves, the antenna must be mounted near the roof, etc. Beside this, the antenna cannot receive signals unless a booster is connected. Also when the booster is used, noises increase during reception of weak broadcasting waves, and hence degrades the signal-to-noise ratio. This necessarily results in signal reproduction difficult to hear. Further, since a significantly wide band amplifier is required to amplify AM, FM and TV bands, this also invites a deterioration of the signal-to-noise ratio and an increase of the manufacturing cost. In order to establish a complete non-directivity by disposing ferrite bar cores in a crossing relationship and by connecting pickup coils, it is necessary to shift the phase of the induced voltage of one of the coils by π/2 for subsequent signal composition. However, it is a very difficult technology to shift the phase throughout a wide band. Further, since most car bodies are arcuated at the boundary between the roof and the pillar portion, it is difficult to reliably mount and hold such an antenna there. JP-A-51-131243 discloses a car antenna having a wire wound cross shaped magnetic core. It is an object of embodiments of the invention to provide an antenna in which a magnetic member has a particular configuration to establish a wide-band and nondirectional property improving the reception efficiency and to ensure an acceptable reception wherever of the car body the antenna is located. According to the invention, there is provided a broadcasting wave reception antenna comprising: a magnetic membr having multiple radial projections extending on a common plane; coils wound on respective said projections of said magnetic member; and a cable connecting said coils to a receiver; characterised in that said coils are connected in series to form a loop type antenna. When coils on the radial projections on the magnetic member are all connected in series to form a loop type antenna, reception of electromagnetic waves is not largely affected by the position of the antenna in the car body. It is rather preferable to slightly isolate the antenna from the car body to improve the antenna gains. The series-connection of all coils on respective radial projections establishes a property tunable at AM, FM and TV bands. Examples of the present invention will now be described with reference to the drawings, in which:- Figure 1 is a perspective view showing an antenna according to one embodiment of the present invention fully embedded in an insulating material which is partly cut out to show the antenna therein; Figure 2 shows different preferred configurations of a magnetic member; Figure 3 is a view for explanation of a loop type antenna according to one embodiment of the present invention; Figures 4(a) and 4(b) are views for explanation of a dipole antenna; Figure 5 shows an exemplary connection between loop-shaped coils acording to one embodiment of the present invention; Figure 7 is a perspective view of an antenna body used in a further embodiment of the invention which is fully embedded in a resilient member shown here as being partly cut out to show the antenna body therein; Figure 8(a) is a side elevation of the assembly of Figure 7 before mounted in position of a car; Figure 8(b) is a side elevation of the assembly of Figure 7 after mounted in position of a car in a compressed fashion; Figures 9 and 10 show where and how the assembly of Figure 1 is mounted in a line manufacturing process; and Figure 11 is a perspective view showing a configuration of a soft resilient member. Figure 1 shows an embodiment in which a magnetic member 1 has radially extending projections 2 wound with coils 3 to form an antenna A at a base 4 thereof. The magnetic member 1 is fully embedded in an insulating material. As shown at (a) and (b) in Figure 2, the magnetic member 1 is formed in a single body having radial projections 2 extending on a common plane. Respective projections 2 are provided with coils wound thereon which are connected as described later, and a supply line 6 extending therefrom is connected to a receiver (not shown). The single-body arrangement of the magnetic member 1 having coplanarly extending projections 2 permits any complicated configuration or arrangement of the projections other than those in Figure 2, without doubling or tripling the thickness thereof, unlike the prior art arrangement in which two or more magnetic members are piled and hence increase the entire thickness. Therefore, the single-body magnetic member 1 may originally have an increased thickness to provide a large cross-sectional area of each projection 2. The coplanarly extending relationships between the projections 2 ensures a close magnetic coupling. As a result, the antenna exhibits a high gain under selected coil winding conditions and selected connecting conditions between the coils, and this permits omission of the booster used in the prior art arrangement. Figure 1 shows the magnetic member 1 as having eight projections 2. However, the substantially same capacity is obtained by other configurations including that of Figure 2(b) provided that a plurality of projections 2 are formed. Figure 3 shows a connection configuration between respective coils to form a loop-type antenna, so that the antenna is tuned at any received frequencies in AM, FM and TV bands to effectively receive electromagnetic waves. Figure 4(b) shows a connection for forming a dipole antenna in which the coils are divided into two antenna coil groups 3a and 3b and are connected in each group. One end of one antenna coil group 3a is connected to a signal line 6a of the supply line 6 whereas one end of the other antenna coil group 3b is connected to a ground connection 6b of the supply line 6 so as to form the dipole antenna shown in Figure 4(b). Figure 5 shows an arrangement of the loop-connected antenna according to the invention in which the coils 3 on respective projections 2 are connected in series sequentially. In this case, the coils 3 may be connected, skipping respective adjacent ones. As described above, the inventive antenna is made of a magnetic member (core) which is a single body having radially extending projections 2 each having a relatively large cross-sectional area and therefore reduces the loss in the magnetic flux. Therefore, the antenna is particularly suitable for use as a car antenna which requires a nondirectional property so as to ensure all directional reception during navigation of the car. Although the magnetic member 1 may be formed in a single body by sintering ferrite powder or other ferromagnetic powder, it may be made from multiple ferromagnetic bars which are united together to form a flat plane as shown in Figure 2. Figures 7 through 11 show a further embodiment of the invention which is particularly suitable as an antenna fully embedded in a wall of a car. Figure 7 shows an arrangement of an antenna body in which reference numeral 11 designates a low band reception antenna of a tuning type having a known magnetic core wound with coils, and these coils and a capacitor form a tuning circuit. The magnetic core 11′ has a cross-like configuration, and coils 12 are wound thereon. The coils 12 are connected to a tuning capacitor element (not shown) to form a tuning circuit for reception of low band waves. Reference numeral 13 denotes a high band reception antenna. The illustrated arrangement includes multiple high band reception antennas 13 in the form of spiral contracted antennas. These antennas 11 and 13 form an antenna body 15 from which a cable 16 secured to a base member 14 is extracted. The antenna body 15 has a flat, planar configuration having a thickness D1 of about 10mm, and is fully embedded in a soft resilient member 17 which may be sponge, cotton or other insulating material having a large compression ratio. The antenna A of Figure 1 may be used in lieu of the antenna body 15. Figures 8(a) and 8(b) are cross-sectional views showing the antenna body 15 and the resilient member 17 wrapping it closely. Figure 8(a) shows an antenna assembly consisting of the antenna body 15 and the resilient member 17 before it is mounted in position of a car, and the thickness D2 amounts to about 40 to 60mm. Figure 8(b) shows the antenna assembly after it is mounted between a car body wall 18 and an interior wall member 19 of a car as shown in Figure 9. The resilient member 17 is compressively sandwiched by the car body wall and the interior wall member so as to exhibit its minimum thickness D3 which approaches D3 ≒ D1. The antenna assembly may be mounted in any type of car, and the best position therefor can be selected in individual car designs. If the car roof is selected, a thermal insulation sheet 20 is partly cut out to define a space for receiving the antenna body 15 therein during the line manufacturing process of the car. In this process, when the interior wall member 19 is overlaid on the antenna assembly after the latter is put in contact with the car body, the resilient member 17 is compressed by the interior wall member 19 against the car body. Therefore, the antenna assembly is forcibly, immovably held between the car body wall and the interior wall member without requiring any particular fixing means. Figure 10 shows the antenna assembly mounted in a rear wall of a car in a line manufacturing process as in the case of Figure 9. The antenna assembly may also be mounted in a door of a car. Figure 11 shows a configuration of the soft resilient member 17. According to the mounting method the antenna fully embedded in the soft resilient member is reliably held between a car body wall and an interior wall member, and immovable with respect to the car body when the car body vibrates during navigation. Therefore, it is not necessary to use any fixture member to fix the antenna assembly in position. Further, the antenna assembly can be mounted in any desired position of a car in a line manufacturing process of the car. The core may also be made by combining multiple bar-shaped cores. As described above, the antenna includes a magnetic member in which multiple radial projections extend on a common plane, and in which coils wound on the projections are connected in a loop configuration or in a dipole configuration. Therefore, wherever the antenna is mounted in the car, a highly-sensitive, non-directional reception is ensured for wide band waves including AM, FM and TV bands also during navigation of a car. Further, since the antenna can be mounted in any desired position in a car, it is seldom destroyed and never spoils the appearance of the car, as compared to the prior art antenna which must be extended in the exterior of the car for signal reception.

Claims: A broadcasting wave reception antenna comprising: a magnetic member having multiple radial projections extending on a common plane; coils wound on respective said projections of said magnetic member; and a cable connecting said coils to a receiver; characterised in that said coils are connected in series to form a loop type antenna. An antenna according to Claim 1 wherein said magnetic member is a single body. An antenna according to Claim 1 wherein said magnetic member is a combination of multiple magnetic bars. An antenna according to Claim 1 wherein said magnetic member and said coils are fully embedded in an insulating material. An antenna according to Claim 1 wherein said magnetic member and said coils are fully embedded in a soft resilient member having a large compression ratio and are sandwichingly held between a car body wall and an interior wall member of a car.

Inventors: SAITO, SYOZO, TAKIZAWA, AKIO
Applicants: NIPPON ANTENNA CO., LTD.
Application year: 1988
Main classification: H01Q1
IPC codes: H01Q1, H01Q7, H01Q21