CA2094077A1 - Diversity antenna having an electric field antenna and a magnetic field antenna - Google Patents
Diversity antenna having an electric field antenna and a magnetic field antennaInfo
- Publication number
- CA2094077A1 CA2094077A1 CA002094077A CA2094077A CA2094077A1 CA 2094077 A1 CA2094077 A1 CA 2094077A1 CA 002094077 A CA002094077 A CA 002094077A CA 2094077 A CA2094077 A CA 2094077A CA 2094077 A1 CA2094077 A1 CA 2094077A1
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- antenna
- electric field
- magnetic field
- field antenna
- diversity
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Abstract
ABSTRACT OF THE DISCLOSURE
An electric field antenna mainly sensitive to an electric field standing wave and a magnetic field antenna mainly sensitive to a magnetic field standing wave are disposed close to each other. The electric field antenna and the magnetic field antenna are switched in accordance with strengths of signals received by those antennas. Typical examples of the electric field antenna and the magnetic field antenna are a mono-pole antenna and a balanced shielded loop antenna, respectively.
An electric field antenna mainly sensitive to an electric field standing wave and a magnetic field antenna mainly sensitive to a magnetic field standing wave are disposed close to each other. The electric field antenna and the magnetic field antenna are switched in accordance with strengths of signals received by those antennas. Typical examples of the electric field antenna and the magnetic field antenna are a mono-pole antenna and a balanced shielded loop antenna, respectively.
Description
DIVERSI~ ANTENNA HAVING AN ELECTRIC FIELD ANTENNA
AND A MAGNETIC FIELD ANTENNA
BACKGROUND OF THE INVENTION
The present invention relates to a diversity antenna for receiving radio waves and a cordless telephone using the same.
Fig. 11 is a block diagram showing a device including a conventional diversity antenna and a receiving/controlling circuit therefor, which device is described, for instance, on page 1,120 of the Handbook for Electronics and Communications (written in Japanese) published on August 20, 1982 by Ohmsha, Ltd.
In Fig. 11, each of a first antenna 1 and a second antenna 2 is a whip antenna, and these antennas are disposed with a sufficiently large separation. An electronic switch 3 serves to switch between the first and second antennas 1 and 2, and has an output terminal 4. Reference numeral 5 represents a high-frequency amplifier/mixing circuit; 6, an intermediate-frequency amplifier circuit for amplifying a received signal;
7, a detector circuit for converting the received signal to an audio signal; 8, an audio signal control circuit for outputting the audio signal at an output terminal 9; 10, a logic control circuit; and 11, a switch driver for controlling the electronic switch 3 via an input terminal 12.
The operation of the above device is as follows.
" 2~''3l~7~
The first antenna 1 and the secor.~ antenna 2 are disposed with a separation not less than 1/4 (1: wavelength).
The signal received by the first antenna 1 or second antenna 2, which is selected by the electronic switch ~, is provided to the high-frequency amplifier/mixing circuit 5 via the output terminal 4 of the electronic switch 3. Afte- being subjected to the signal processing in the circuit S, the received signal is amplified by the intermediate-frequency amplifier circuit 6, converted to the audio signal by the detector circuit 7, and finally output from the output terminal 9 via ~he audio control circuit 8.
Part of the received signal is provided from the intermediate-frequency amplifier circuit 6 to the logic control circuit 10, which judges whether to select the first antenna 1 or second antenna 2 and controls the electro~ic switch 3 via the switch driver 11. The logic control ci~cuit 10 further controls the audio control circuit 8 so as to prevent switching noise from being mixed into the audio signal. The switching between the first antenna 1 and second antenna 2 is performed so as to assure the quality of a sound produced from the audio signal.
In the conventional diversity antenna thus constructed, to avoid the Rayleigh fading effect (a ~-ariation of the electric field strength), the first antenna 1 and second antenna 2 need to be separated at an interval of not less than 1/4. In the case of receiving longer-wavelength waves of 400
AND A MAGNETIC FIELD ANTENNA
BACKGROUND OF THE INVENTION
The present invention relates to a diversity antenna for receiving radio waves and a cordless telephone using the same.
Fig. 11 is a block diagram showing a device including a conventional diversity antenna and a receiving/controlling circuit therefor, which device is described, for instance, on page 1,120 of the Handbook for Electronics and Communications (written in Japanese) published on August 20, 1982 by Ohmsha, Ltd.
In Fig. 11, each of a first antenna 1 and a second antenna 2 is a whip antenna, and these antennas are disposed with a sufficiently large separation. An electronic switch 3 serves to switch between the first and second antennas 1 and 2, and has an output terminal 4. Reference numeral 5 represents a high-frequency amplifier/mixing circuit; 6, an intermediate-frequency amplifier circuit for amplifying a received signal;
7, a detector circuit for converting the received signal to an audio signal; 8, an audio signal control circuit for outputting the audio signal at an output terminal 9; 10, a logic control circuit; and 11, a switch driver for controlling the electronic switch 3 via an input terminal 12.
The operation of the above device is as follows.
" 2~''3l~7~
The first antenna 1 and the secor.~ antenna 2 are disposed with a separation not less than 1/4 (1: wavelength).
The signal received by the first antenna 1 or second antenna 2, which is selected by the electronic switch ~, is provided to the high-frequency amplifier/mixing circuit 5 via the output terminal 4 of the electronic switch 3. Afte- being subjected to the signal processing in the circuit S, the received signal is amplified by the intermediate-frequency amplifier circuit 6, converted to the audio signal by the detector circuit 7, and finally output from the output terminal 9 via ~he audio control circuit 8.
Part of the received signal is provided from the intermediate-frequency amplifier circuit 6 to the logic control circuit 10, which judges whether to select the first antenna 1 or second antenna 2 and controls the electro~ic switch 3 via the switch driver 11. The logic control ci~cuit 10 further controls the audio control circuit 8 so as to prevent switching noise from being mixed into the audio signal. The switching between the first antenna 1 and second antenna 2 is performed so as to assure the quality of a sound produced from the audio signal.
In the conventional diversity antenna thus constructed, to avoid the Rayleigh fading effect (a ~-ariation of the electric field strength), the first antenna 1 and second antenna 2 need to be separated at an interval of not less than 1/4. In the case of receiving longer-wavelength waves of 400
2 ~
MHz or less, a space occupied by the antennas 1 and 2 is therefore appreci~ble and it is difficult to downsize receiving devices that use the diversity antenna.
For example, in cordless telephones, which utilize radio frequency bands of about 250-380 MHz, an interval of about 20-30 cm is required between the first antenna 1 and the second antenna 2. Where the diversity antenna is used in a cordless telephone as a receiving device, the cordless telephone itself becomes very bulky.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a diversity antenna in which two antennas can be arranged close to each other to enable downsizing of a receiving device.
Another object of the invention is to provide a cordless telephone using the above diversity antenna.
According to the invention, a diversity antenna device comprises:
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
2 ~ 7 ~l According to another aspect of the i-vention, the above diversity antenna device is used in a cord ess telephone.
BRIEF DESCRIPTION OF THE DRA~-NGS
Fig. 1 is a block diagram showing z diversity antenna and a receiving/controlling circuit there-or according to a first embodiment of the present invention;
Fig. 2 shows standing-wave patterns appearing in front of a reflection plate in the first embodim~nt;
Fig. 3 is a block diagram showing - diversity antenna and a receiving/controlling circuit there-or according to a second embodiment of the invention;
Fig. 4 shows details of a mono-pole antenna used in the second embodiment;
Fig. 5 shows details of a balan^ed shielded loop antenna used in the second embodiment;
Fig. 6 includes seethrough vie~a of a cordless telephone according to the second embodimer.t;
Figs. 7(a) and 7(b) are graphs showing simulation results of the relationship between the distance of the cordless telephone from a reflection plate and the received signal strength of a radio wave;
Fig. 8 includes seethrough vie~-s of a cordless telephone according to a third embodiment of the invention;
Fig. 9 includes seethrough vie~-s of a cordless telephone according to a fourth embodiment of the invention;
2~ 7 Fig. 10 includes seethrough vie-~s of a cordless telephone according to a fifth embodiment of the invention; and Fig. 11 is a block diagram showing a conventional diversity antenna and a receiving/controlling circuit therefor.
DESCRIPTION OF THE PREFERRED_EMB0DIMENTS
Embodiments of the present invention are described hereinafter with reference to the accompanying drawings.
Embodiment 1 Fig. 1 is a block diagram showing a device including a diversity antenna and a receiving/controlling circuit therefor according to a first embodiment of the invention, and Fig. 2 shows standing-wave patterns appearing in front of a reflection plate in this embodiment.
The parts in Fig. 1 that are the same as or equivalent to those in Fig. 11 are given the same reference numerals and descriptions therefor are omitted here. Reference numeral 13 represents an electric field antenna mainly sensitive to the electric field component of electromagnetic waves; 14, a grounding plate; and 15, a coaxial cable. A magnetic field antenna 16 is mainly sensitive to the magnetic field component of electromagnetic waves, and is disposed close to the electric field antenna 13. Reference numerals 17, 18 and 19 represent a tuning capacitor, a matching loop and a coaxial cable, respectively. An antenna switch 20 has contacts 21, 22 and 23.
Reference numerals 24 and 25 represent a receiving signal input terminal and a control signal input terminal, respectively.
æ~
In Fig. 2, reference numeral 26 represents a reflection plate that reflects electromagnetic waves. ~umerals 27 and 28 respectively represent an electric field standing wave and a magnetic field standing wave of an electro.agnetic wave that appear in front of the reflection plate 26. It is seen from Fig. 2 that the valleys of the electric file~ standing wave 27 and the magnetic field standing wave 28 aDpear alternately every A/4-distance.
The operation of the above device is described below.
A radio wave transmitted and pro~agated through a certain space is partially reflected by the reflection plate 26, and the electric standing wave 27 and the magnetic standing wave 28 appear in front of the reflection plate 26 as shown in Fig. 2.
As a receiving device having the di~ersity antenna is moved, the antenna switch 20 is controlled by the switch driver ll so that the contact 21 is connected to ~he contact 23 at locations where the magnetic field standing ~-~ve 28 is stronger than the electric field standing wave, to introduce a signal received by the magnetic antenna 16 to the receiving signal input terminal 24 via the matching loop 18 and the coaxial cable 19. On the other hand, at locations ~-here the electric field standing wave 27 is stronger than the magnetic field standing wave, the contact 21 is connected to the contact 22 in the antenna switch 20, to introduce a signal received by the 2~
electric field antenna 13 to the receiving signal input terminal 24.
The operations of the high--frequency amplifier/mixing circuit 5, intermediate-frequency amplifier circuit 6, detector circuit 7 and audio control circuit 8 to produce an audio signal from the receiving signal and output it at the output terminal 9 is the same as the conventional device of Fig. 11.
In order to switch between the electric field antenna 13 and the magnetic field antenna 16, part of the receiving signal branched in theintermediate-frequency amplifier/mixing circuit 6 is input to the logic control circuit 10. Monitoring the strengths of the electric field standing wave 27 and the magnetic field standing wave 28, the logic control circuit 10 provides a control signal for antenna switching to the control signal input terminal 25.
While in the above embodiment the single receiving circuit consisting of the high-frequency amplifier/mixing circuit 5 to the output terminal 9 is used, separate receiving circuits may be provided for the electric field antenna 13 and the magnetic field antenna 16. In the latter case, the receiving signal strengths of the respective receiving circuits are detected and compared to select the receiving circuit that produces a larger signal level. There can be obtained advantages similar to those of the first embodiment.
Embodiment 2 ~ $ ~ 7 ~
The second embodiment is directed to the case where a diversity antenna of the invention is employed in a cordless telephone. Fig. 3 is a block diagram showing a diversity antenna and a controlling circuit therefor according to the second embodiment. Fig. 4 and 5 shows details of a mono-pole antenna and a balanced shielded loop antenna, respectively.
Fig. 6 includes seethrough views of the cordless telephone.
In Fig. 4, reference numeral 29 represents a mono-pole antenna serving as the electric field antenna 13, and numeral 30 represents a signal received by the antenna 29. In Fig. 5, reference numeral 31 represents a balanced shielded loop antenna serving as the magnetic field antenna 16; 32, a matching capacitor; 33, a semi-rigid coaxial cable; 34, a copper cable having the same diameter as the semi-rigid coaxial cable 33; and 35, a signal received by the antenna 31.
Stated strictly, the balanced shielded loop antenna 31 also receives the electric field standing wave 27 to generate a small current. To minimize this effect, the antenna 31 is constructed so as to assume a symmetrical shape with respect to the matching capacitor 32 as a load. Further, the shielded structure is employed to avoid influences of other metal parts when the antenna 31 is incorporated in a cordless telephone 36 (described later). As a result, the ability of receiving the magnetic field standing wave 28 is improved.
Fig. 6 shows a cordless telephone which includes the mono-pole antenna 29 and the balanced shielded loop antenna 31.
Reference numeral 37 represents a case. A circuit board 38 has the receiving/controlling circuit and processes the receiving signals 30 and 35. Numerals 39 and 40 are an earpiece and a mouthpiece, respectively. The mono-pole antenna 29 and the balanced shielded loop antenna 31 are disposed near the locations of the receiving signals 30 and 35 so as not to be placed in parallel with each other and not to be overlapped with each other.
Fig. 6 shows only the parts th2t relate to the invention, though the cordless telephone 36 has many other types of parts. Since the cordless telephone 36 is mainly used in a house, a wall of reinforced concrete or a steel door serves as the reflection plate 26.
The operation of the second embodiment is described below.
As in the case of the first embodiment, the controlling circuit consisting of the antenna switch 20 etc. (mounted on the circuit board 35) switches between the mono-pole antenna 29 and the balanced shielded loop antenna 31 so as to receive the electric field standing wave 27 or magnetic filed standing wave 28, whichever is stronger.
Figs. 7(a) and 7(b) show simulation results of the relationship between the distance of the cordless telephone from the reflection plate 26 and the received signal strength of a radio wave. Fig. 7(a) is for the case of using the diversity antenna consisting of the electric field antenna 13 2 ~ 7 r~
and the magnetic field antenna 16, and Fi~. 7(b) is for the case of using only the electric field antenna 13.
It is assumed that a radio wave of frequency 300 MHz (wavelength 1.0 m) is transmitted from a transmitting device located in a space 10-m away from the reflection plate 26, and that the reflectance of the reflection plate 26 is 1.0 (total reflection).
It is understood from Figs. 7(a) and 7(b) that the received signal strength E varies less with respect to the distance D in the case of using both of the electric field antenna 13 and the magnetic field antenna 16 than the case of using only the electric field antenna 13.
To confirm the advantage of the second embodiment, another experiment was conducted in which the cordless telephone 36 (main unit and sub-unit) was placed in a room of 4 m x 4 m = 16 m2 enclosed with an heat-insulating material with aluminum foil (drawing omitted). While there occurred standing wave noise at 47 locations, noise was eliminated at all the 47 locations by using the diversity antenna consisting of the mono-pole antenna 29 and the balanced shielded loop antenna 31.
Although in the second embodiment the mono~pole antenna 29 is used as the electric field antenna 13, it may be replaced with a helical antenna. These types of antennas have advantages that the antenna length can be shortened and that they can be accommodated in a limited space.
2 ~ 7 7 Embodiment 3 Advantages similar to those of the second embodiment can be obtained by employing other types of electric field antenna and magnetic field antenna.
Fig. 8 includes seethrough views of a cordless telephone 41 using a diversity antenna according to a third embodiment of the invention. Reference numeral 42 represents a case. A whip antenna 43 as the electric f eld antenna 13 is capable of expansion and contraction.
Reference numeral 44 represents a loop antenna as the magnetic field antenna 16; 45, a matching capacitor; 46, a radio signal supply line; 47, a grounding point; 48, a receiving signal; 49, a circuit board having the receiving/controlling circuit; 50, a radio signal supply point;
51, an earpiece; 52, a microphone provided in a mouthpiece; 53, dial buttons; 54, a cover that is closed to cover the dial buttons 53 when the telephone 41 is not in use.
The cordless telephone 41 operates in the same manner as in the first embodiment. That is, the whip antenna 43 and the loop antenna 44 are switched by the controlling circuit provided on the circuit board 49.
Embodiment 4 Fig. 9 includes seethrough view of a cordless telephone using a diversity antenna according to a fourth embodiment of the invention. A dipole antenna 55 as the electric field antenna 13 is incorporated in a case 36 and receives the 2 ~ s~
electric field standing wave 27. The same balanced shielded loop antenna 31 as in the second embodiment s employed as the magnetic field antenna 16. The operation of the third embodiment is not described here because it is the same as of the second embodiment.
Embodiment 5 Fig. 10 includes seethrough views of a cordless telephone using a diversity antenna acco-ding to a fifth embodiment of the invention. An inverted-F-shaped antenna 56 as the electric field antenna 13 is incorporated in a case 36 and receives the electric field standing w2ve 27. The same balanced shielded loop antenna 31 as in the second embodiment is employed as the magnetic field antenna 16. The operation of the fourth embodiment is not described here because it is the same as of the second embodiment.
As described above, according to the invention, the electric field antenna and the magnetic field antenna are arranged close to each other, and one of the two antennas is selected by the switching means in accordance with the received signal strength. Since the electric field standing wave or magnetic field wave is selectively received to provide a larger signal strength in a desired frequency band, the received signal level can be kept high. Further, the diversity antenna can be obtained which can downsize the receiving device.
Since there can be reduced such noise as occurs in frequency bands in which the received signal strength of the 2 ~ 7 ~
electric field standing wave or magnetic fie~d standing wave is small, the noise included in the receiv_ng signal can be reduced.
When the diversity antenna of the in.-ention is employed in a cordless telephone, the quality of th~ reproduced sound can be improved to provide comfortable telep~.one conversations.
MHz or less, a space occupied by the antennas 1 and 2 is therefore appreci~ble and it is difficult to downsize receiving devices that use the diversity antenna.
For example, in cordless telephones, which utilize radio frequency bands of about 250-380 MHz, an interval of about 20-30 cm is required between the first antenna 1 and the second antenna 2. Where the diversity antenna is used in a cordless telephone as a receiving device, the cordless telephone itself becomes very bulky.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a diversity antenna in which two antennas can be arranged close to each other to enable downsizing of a receiving device.
Another object of the invention is to provide a cordless telephone using the above diversity antenna.
According to the invention, a diversity antenna device comprises:
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
2 ~ 7 ~l According to another aspect of the i-vention, the above diversity antenna device is used in a cord ess telephone.
BRIEF DESCRIPTION OF THE DRA~-NGS
Fig. 1 is a block diagram showing z diversity antenna and a receiving/controlling circuit there-or according to a first embodiment of the present invention;
Fig. 2 shows standing-wave patterns appearing in front of a reflection plate in the first embodim~nt;
Fig. 3 is a block diagram showing - diversity antenna and a receiving/controlling circuit there-or according to a second embodiment of the invention;
Fig. 4 shows details of a mono-pole antenna used in the second embodiment;
Fig. 5 shows details of a balan^ed shielded loop antenna used in the second embodiment;
Fig. 6 includes seethrough vie~a of a cordless telephone according to the second embodimer.t;
Figs. 7(a) and 7(b) are graphs showing simulation results of the relationship between the distance of the cordless telephone from a reflection plate and the received signal strength of a radio wave;
Fig. 8 includes seethrough vie~-s of a cordless telephone according to a third embodiment of the invention;
Fig. 9 includes seethrough vie~-s of a cordless telephone according to a fourth embodiment of the invention;
2~ 7 Fig. 10 includes seethrough vie-~s of a cordless telephone according to a fifth embodiment of the invention; and Fig. 11 is a block diagram showing a conventional diversity antenna and a receiving/controlling circuit therefor.
DESCRIPTION OF THE PREFERRED_EMB0DIMENTS
Embodiments of the present invention are described hereinafter with reference to the accompanying drawings.
Embodiment 1 Fig. 1 is a block diagram showing a device including a diversity antenna and a receiving/controlling circuit therefor according to a first embodiment of the invention, and Fig. 2 shows standing-wave patterns appearing in front of a reflection plate in this embodiment.
The parts in Fig. 1 that are the same as or equivalent to those in Fig. 11 are given the same reference numerals and descriptions therefor are omitted here. Reference numeral 13 represents an electric field antenna mainly sensitive to the electric field component of electromagnetic waves; 14, a grounding plate; and 15, a coaxial cable. A magnetic field antenna 16 is mainly sensitive to the magnetic field component of electromagnetic waves, and is disposed close to the electric field antenna 13. Reference numerals 17, 18 and 19 represent a tuning capacitor, a matching loop and a coaxial cable, respectively. An antenna switch 20 has contacts 21, 22 and 23.
Reference numerals 24 and 25 represent a receiving signal input terminal and a control signal input terminal, respectively.
æ~
In Fig. 2, reference numeral 26 represents a reflection plate that reflects electromagnetic waves. ~umerals 27 and 28 respectively represent an electric field standing wave and a magnetic field standing wave of an electro.agnetic wave that appear in front of the reflection plate 26. It is seen from Fig. 2 that the valleys of the electric file~ standing wave 27 and the magnetic field standing wave 28 aDpear alternately every A/4-distance.
The operation of the above device is described below.
A radio wave transmitted and pro~agated through a certain space is partially reflected by the reflection plate 26, and the electric standing wave 27 and the magnetic standing wave 28 appear in front of the reflection plate 26 as shown in Fig. 2.
As a receiving device having the di~ersity antenna is moved, the antenna switch 20 is controlled by the switch driver ll so that the contact 21 is connected to ~he contact 23 at locations where the magnetic field standing ~-~ve 28 is stronger than the electric field standing wave, to introduce a signal received by the magnetic antenna 16 to the receiving signal input terminal 24 via the matching loop 18 and the coaxial cable 19. On the other hand, at locations ~-here the electric field standing wave 27 is stronger than the magnetic field standing wave, the contact 21 is connected to the contact 22 in the antenna switch 20, to introduce a signal received by the 2~
electric field antenna 13 to the receiving signal input terminal 24.
The operations of the high--frequency amplifier/mixing circuit 5, intermediate-frequency amplifier circuit 6, detector circuit 7 and audio control circuit 8 to produce an audio signal from the receiving signal and output it at the output terminal 9 is the same as the conventional device of Fig. 11.
In order to switch between the electric field antenna 13 and the magnetic field antenna 16, part of the receiving signal branched in theintermediate-frequency amplifier/mixing circuit 6 is input to the logic control circuit 10. Monitoring the strengths of the electric field standing wave 27 and the magnetic field standing wave 28, the logic control circuit 10 provides a control signal for antenna switching to the control signal input terminal 25.
While in the above embodiment the single receiving circuit consisting of the high-frequency amplifier/mixing circuit 5 to the output terminal 9 is used, separate receiving circuits may be provided for the electric field antenna 13 and the magnetic field antenna 16. In the latter case, the receiving signal strengths of the respective receiving circuits are detected and compared to select the receiving circuit that produces a larger signal level. There can be obtained advantages similar to those of the first embodiment.
Embodiment 2 ~ $ ~ 7 ~
The second embodiment is directed to the case where a diversity antenna of the invention is employed in a cordless telephone. Fig. 3 is a block diagram showing a diversity antenna and a controlling circuit therefor according to the second embodiment. Fig. 4 and 5 shows details of a mono-pole antenna and a balanced shielded loop antenna, respectively.
Fig. 6 includes seethrough views of the cordless telephone.
In Fig. 4, reference numeral 29 represents a mono-pole antenna serving as the electric field antenna 13, and numeral 30 represents a signal received by the antenna 29. In Fig. 5, reference numeral 31 represents a balanced shielded loop antenna serving as the magnetic field antenna 16; 32, a matching capacitor; 33, a semi-rigid coaxial cable; 34, a copper cable having the same diameter as the semi-rigid coaxial cable 33; and 35, a signal received by the antenna 31.
Stated strictly, the balanced shielded loop antenna 31 also receives the electric field standing wave 27 to generate a small current. To minimize this effect, the antenna 31 is constructed so as to assume a symmetrical shape with respect to the matching capacitor 32 as a load. Further, the shielded structure is employed to avoid influences of other metal parts when the antenna 31 is incorporated in a cordless telephone 36 (described later). As a result, the ability of receiving the magnetic field standing wave 28 is improved.
Fig. 6 shows a cordless telephone which includes the mono-pole antenna 29 and the balanced shielded loop antenna 31.
Reference numeral 37 represents a case. A circuit board 38 has the receiving/controlling circuit and processes the receiving signals 30 and 35. Numerals 39 and 40 are an earpiece and a mouthpiece, respectively. The mono-pole antenna 29 and the balanced shielded loop antenna 31 are disposed near the locations of the receiving signals 30 and 35 so as not to be placed in parallel with each other and not to be overlapped with each other.
Fig. 6 shows only the parts th2t relate to the invention, though the cordless telephone 36 has many other types of parts. Since the cordless telephone 36 is mainly used in a house, a wall of reinforced concrete or a steel door serves as the reflection plate 26.
The operation of the second embodiment is described below.
As in the case of the first embodiment, the controlling circuit consisting of the antenna switch 20 etc. (mounted on the circuit board 35) switches between the mono-pole antenna 29 and the balanced shielded loop antenna 31 so as to receive the electric field standing wave 27 or magnetic filed standing wave 28, whichever is stronger.
Figs. 7(a) and 7(b) show simulation results of the relationship between the distance of the cordless telephone from the reflection plate 26 and the received signal strength of a radio wave. Fig. 7(a) is for the case of using the diversity antenna consisting of the electric field antenna 13 2 ~ 7 r~
and the magnetic field antenna 16, and Fi~. 7(b) is for the case of using only the electric field antenna 13.
It is assumed that a radio wave of frequency 300 MHz (wavelength 1.0 m) is transmitted from a transmitting device located in a space 10-m away from the reflection plate 26, and that the reflectance of the reflection plate 26 is 1.0 (total reflection).
It is understood from Figs. 7(a) and 7(b) that the received signal strength E varies less with respect to the distance D in the case of using both of the electric field antenna 13 and the magnetic field antenna 16 than the case of using only the electric field antenna 13.
To confirm the advantage of the second embodiment, another experiment was conducted in which the cordless telephone 36 (main unit and sub-unit) was placed in a room of 4 m x 4 m = 16 m2 enclosed with an heat-insulating material with aluminum foil (drawing omitted). While there occurred standing wave noise at 47 locations, noise was eliminated at all the 47 locations by using the diversity antenna consisting of the mono-pole antenna 29 and the balanced shielded loop antenna 31.
Although in the second embodiment the mono~pole antenna 29 is used as the electric field antenna 13, it may be replaced with a helical antenna. These types of antennas have advantages that the antenna length can be shortened and that they can be accommodated in a limited space.
2 ~ 7 7 Embodiment 3 Advantages similar to those of the second embodiment can be obtained by employing other types of electric field antenna and magnetic field antenna.
Fig. 8 includes seethrough views of a cordless telephone 41 using a diversity antenna according to a third embodiment of the invention. Reference numeral 42 represents a case. A whip antenna 43 as the electric f eld antenna 13 is capable of expansion and contraction.
Reference numeral 44 represents a loop antenna as the magnetic field antenna 16; 45, a matching capacitor; 46, a radio signal supply line; 47, a grounding point; 48, a receiving signal; 49, a circuit board having the receiving/controlling circuit; 50, a radio signal supply point;
51, an earpiece; 52, a microphone provided in a mouthpiece; 53, dial buttons; 54, a cover that is closed to cover the dial buttons 53 when the telephone 41 is not in use.
The cordless telephone 41 operates in the same manner as in the first embodiment. That is, the whip antenna 43 and the loop antenna 44 are switched by the controlling circuit provided on the circuit board 49.
Embodiment 4 Fig. 9 includes seethrough view of a cordless telephone using a diversity antenna according to a fourth embodiment of the invention. A dipole antenna 55 as the electric field antenna 13 is incorporated in a case 36 and receives the 2 ~ s~
electric field standing wave 27. The same balanced shielded loop antenna 31 as in the second embodiment s employed as the magnetic field antenna 16. The operation of the third embodiment is not described here because it is the same as of the second embodiment.
Embodiment 5 Fig. 10 includes seethrough views of a cordless telephone using a diversity antenna acco-ding to a fifth embodiment of the invention. An inverted-F-shaped antenna 56 as the electric field antenna 13 is incorporated in a case 36 and receives the electric field standing w2ve 27. The same balanced shielded loop antenna 31 as in the second embodiment is employed as the magnetic field antenna 16. The operation of the fourth embodiment is not described here because it is the same as of the second embodiment.
As described above, according to the invention, the electric field antenna and the magnetic field antenna are arranged close to each other, and one of the two antennas is selected by the switching means in accordance with the received signal strength. Since the electric field standing wave or magnetic field wave is selectively received to provide a larger signal strength in a desired frequency band, the received signal level can be kept high. Further, the diversity antenna can be obtained which can downsize the receiving device.
Since there can be reduced such noise as occurs in frequency bands in which the received signal strength of the 2 ~ 7 ~
electric field standing wave or magnetic fie~d standing wave is small, the noise included in the receiv_ng signal can be reduced.
When the diversity antenna of the in.-ention is employed in a cordless telephone, the quality of th~ reproduced sound can be improved to provide comfortable telep~.one conversations.
Claims (10)
1. A diversity antenna device comprising:
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
2. The diversity antenna device of claim 1, wherein the switching means comprises two receiving circuits for the electric field antenna and the magnetic field antenna, respectively.
3. The diversity antenna device of claim 1, wherein the electric field antenna is a mono-pole antenna, and the magnetic field antenna is a balanced shielded antenna that utilizes a semi-rigid coaxial cable.
4. The diversity antenna device of claim 1, wherein the electric field antenna is a whip antenna.
5. The diversity antenna device of claim 1, wherein the electric field antenna is a helical antenna.
6. The diversity antenna device of claim l, wherein the electric field antenna is a dipole antenna.
7. The diversity antenna device of claim 1, wherein the electric field antenna is an inverted-F-shaped antenna
8. The diversity antenna device of claim l, wherein the magnetic field antenna is a loop antenna.
9. The diversity antenna device of claim 1, wherein the magnetic field antenna is a slot antenna.
10. A cordless telephone comprising a diversity antenna device, said diversity antenna device comprising:
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
an electric field antenna mainly sensitive to an electric field component of a radio wave being transmitted;
a magnetic field antenna disposed close to the electric field antenna and mainly sensitive to a magnetic field component of the radio wave; and means for switching between the electric field antenna and the magnetic field antenna in accordance with strengths of respective signals received by the electric field antenna and the magnetic field antenna.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4-97838 | 1992-04-17 | ||
| JP9783892 | 1992-04-17 | ||
| JP29012092 | 1992-10-28 | ||
| JP4-290120 | 1992-10-28 | ||
| JP5-16174 | 1993-02-03 | ||
| JP5016174A JPH06197053A (en) | 1992-10-28 | 1993-02-03 | Diversity antenna and cordless telephone set with diversity antenna mounted thereon |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2094077A1 true CA2094077A1 (en) | 1993-10-18 |
Family
ID=27281277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002094077A Abandoned CA2094077A1 (en) | 1992-04-17 | 1993-04-15 | Diversity antenna having an electric field antenna and a magnetic field antenna |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2094077A1 (en) |
-
1993
- 1993-04-15 CA CA002094077A patent/CA2094077A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |