EP1041664A1

EP1041664A1 - Dual-band non-reversible circuit device

Info

Publication number: EP1041664A1
Application number: EP00106872A
Authority: EP
Inventors: Koji c/o Tokin Corporation Kamei; Atsushi c/o Tokin Corporation Furuta; Norihiko c/o Tokin Corporation Ono; Shigeyoshi C/O Tokin Corporation Yoshida; Kenji C/O Nec Corporation Takamoro
Original assignee: NEC Corp; Tokin Corp
Current assignee: NEC Corp; Tokin Corp
Priority date: 1999-03-30
Filing date: 2000-03-30
Publication date: 2000-10-04
Also published as: CN1271975A; JP2000286611A; NO20001663D0; NO20001663L

Abstract

A dual-band non-reversible circuit device is constituted by two circulator components operating in different frequencies in a magnetic circuit. One circulator component is a lumped constant type component operating toward the low frequency side. The other circulator component is a distributed constant type component operating toward the high frequency side.

Description

Background of he Invention:

The present invention relates to a dual-band non-reversible circuit device used for transmitting and receiving wireless service which has two different frequencies in one terminal, the device operating in two different frequency bands in a mobile communication field.
An invention disclosed in Japanese Unexamined Patent Publication (JP-A) No. H02-55406 (55406/1990) has been known as a prior art. The invention is characterized in that two circulators are arranged in a magnetic circuit. This constitution can facilitate the control of the intensity of a magnetic field and reduce the number of parts. This prior art provides a circulator having a simple constitution.
The invention disclosed in the Japanese Unexamined Patent Publication (JP-A) No. H02-55406 will be described below. The invention is the one relative to a circulator type hybrid. This circulator type hybrid has two circulators arranged at its input side or output side. Each of the circulators comprises an internal conductor and a ferrite. A grounded conductor and a magnet are laminated on each circulator. The above-mentioned two circulators are fixed to sandwich a magnetic body made of iron or the like between them. With this structure, the impedance matching of the input side or the output side of the hybrid can be performed. When the magnets corresponding to the two circulators are magnetized, they can be magnetized at the same time by a magnetic field in the same direction.
In this case, since the magnets corresponding to the two circulators can be magnetized simultaneously at the same magnetic field, the intensity of each magnetic field can be easily controlled. The number of parts constituting a circulator type hybrid decrease. The structure of the hybrid simplifies.
However, in the case of the above-mentioned conventional dual circulator, when two non-reversible circuit devices are connected in parallel, an insertion loss degrades because of the impedance mismatch.
Also, recent communication systems tend to have a wide pass bandwidth to ensure a large circuit capacity. Since the conventional non-reversible circuit device has a narrow bandwidth, it can not be applied to these systems.
Also, large attenuation is required to prevent a second or a third harmonic. In the conventional constitution, it is difficult to ensure a large attenuation in a spurious band. Also, from the viewpoint of productivity, it is required that the device has a compact low-profile shape and a simple structure. The present invention has been made in consideration of these problems. It is the object of the present invention to provide a dual-band non-reversible circuit device which does not suffer deterioration through insertion loss even if two non-reversible circuits are connected in parallel and has a wide bandwidth, a compact and low-profile shape, and a simple structure.
An antenna sharing device constituted by a diplexer, a switch, a lowpass-filter (hereinafter referred to as LPF), and a band-pass-filter (hereinafter referred to as BPF) and capable of corresponding to two frequency bands is well known. However, the addition of the insertion losses of the diplexer, the switch, the LPF, and the BPF causes a greater loss of the transmitting and receiving signal. This in turn results in a shortage of transmitting power and the deterioration of receiving sensitivity. Further, when the switch is changed over, power is consumed, which shortens the life of a battery. The present invention has been made in consideration of these problems, and another object of the present invention is to provide an antenna sharing device with little insertion loss and no power consumption.

Summary of the Invention:

It is therefore an object of the present invention to provide a dual-band non-reversible circuit device which does not suffer deterioration through insertion loss even if two non-reversible circuits are connected in parallel, and has a wide bandwidth, a compact and low-profile shape, and a simple structure.
It Is another object of the present invention to provide an antenna sharing device having little insertion loss and no power consumption.
A dual-band non-reversible circuit device in accordance with the present invention has, in a case, a first non-reversible circuit component and a second circuit component each of which includes at least a ferrite plate, a central conductor, a magnet, and a grounded conductor. The first non-reversible circuit component operates in a first frequency band and the second non-reversible circuit component operates in a second frequency band, wherein the first frequency band is different from the second frequency band. The first non-reversible circuit component has a lumped constant type frequency band toward the low frequency side. The second non-reversible circuit component has a distributed constant type frequency band toward the high frequency side.
Each of the first and the second non-reversible circuit components has a primary Chebyshev circuit including an inductor and a condenser connected in series to the input/ output terminals thereof. Therefore, they can unerringly operate in a broad-band system.
The first and the second non-reversible circuit components are connected in parallel to each other via an impedance matching circuit for matching their impedance. This makes it possible to control impedance easily.
An antenna is connected to the impedance matching circuit so that the antenna is connected in common to the first and the second non-reversible circuit components. That is, an antenna sharing device having no power consumption and little insertion loss can be constituted by using the non-reversible circuit devices as antenna sharing devices corresponding to two frequencies.
A transmitting device and a receiving device for the first frequency band is connected to the terminal of the first non-reversible circuit component A transmitting device and a receiving device corresponding to the second frequency band is connected to the terminal of the second non-reversible circuit component.
The first and the second non-reversible circuit components function as circulators or isolators. Either the first or the second non-reversible circuit components may be an isolator and the other may be a circulator.

Brief Description of the Drawing:

FIGs. 1A and 1B are views showing the constitution of a conventional circulator type hybrid.
FIG. 2 is an illustration showing the constitution of a conventional dual-band type antenna sharing device.
FIG. 3 is an exploded perspective view showing one preferred embodiment of a dual-band non-reversible circuit device in accordance with the present invention.
FIG. 4 is an illustration showing the circuit constitution of a circulator for an 800 MHz band.
FIG. 5 is an illustration showing the structure of a distributed constant type non-reversible circuit element.
FIG. 6 is an illustration showing one preferred embodiment of the connection of a circulator for an 800 MHz band and a circulator for a 1.9 GHz band.
FIG. 7 is a cross-sectional view showing the constitution of a dual-band non-reversible circuit device in accordance with one preferred embodiment of the present invention.
FIG. 8 is a cross-sectional view showing the constitution of a dual-band non-reversible circuit device in accordance with another preferred embodiment of the present invention.
FIG. 9A is an illustration showing the frequency characteristics in the 800 MHz band of a dual circulator in accordance with the present invention.
FIG. 9B is an illustration showing the frequency characteristics in the 1.9 GHz band of a dual circulator in accordance with the present invention.
FIG. 10 is an illustration of an example in which a dual-band circulator in accordance with the present invention is applied to a device for PDC/800 MHz transmitting and receiving and a device for PHS/1.9 GHz transmitting and receiving.

Description of the Preferred Embodiments:

A conventional combination of circulator and hybrid (disclosed in Japanese Unexamined Patent Publication (JP-A) No. H02-55406) will be described below specifically with reference to FIGs. 1A and 1B. The invention disclosed in the official gazette is the one relating to a circulator type hybrid. This circulator type hybrid, as shown in FIGS. 1A and 1B, has two circulators 4, 14 arranged at the input side or the output side of the hybrid. The circulator 4 is constituted by an internal conductor 5 and a ferrite 6. The circulator 14 is constituted by an internal conductor 15 and a ferrite 16. A grounded conductor 7 and a magnet 8 are laminated on the circulator 4. A grounded conductor 17 and a magnet 18 are laminated on the circulator 14. The circulator 4 and the circulator 14 are fixed to sandwich a magnetic body 11 made of iron or the like between them. This structure can match the impedance of the input side or the output side of the hybrid. When magnets 8, 18 corresponding to the two circulators 4, 14 are magnetized, they can be magnetized at the same time by a magnetic field in the same direction.
In this case, since the magnets corresponding to the two circulators can be magnetized simultaneously at the same magnetic field, the intensity of each magnetic field can be easily controlled. The number of parts constituting a circulator type hybrid decrease. The structure of the hybrid simplifies.
However, in the case of the above-mentioned conventional dual circulator, when two non-reversible circuit devices are connected in parallel, an insertion loss degrades because of the impedance mismatch.
Also, recent communication systems tend to have a wide pass bandwidth to ensure a large circuit capacity. Since the conventional non-reversible circuit device has a narrow bandwidth, it can not be applied to these systems.
Also, large attenuation is required to prevent a second or a third harmonic. In the conventional constitution, it is difficult to ensure a large attenuation in a spurious band. Also, from the viewpoint of productivity, it is required that the device has a compact low-profile shape and a simple structure. The present invention has been made in consideration of these problems. It is the object of the present invention to provide a dual-band non-reversible circuit device which does not suffer deterioration through insertion loss even if two non-reversible circuits are connected in parallel and has a wide bandwidth, a compact and low-profile shape, and a simple structure.
Also, a constitution shown in FIG. 2 has been proposed as an antenna sharing device corresponding to two frequency bands. However, since the insertions of a diplexer 21, switches 22, 23, low-pass-filters (LPF) 24, 26, bandpass-filters (BPF) 25, 27 to the device all cause the loss of the transmitting and receiving signal, the total loss is great. This in turn results in a shortage of transmitting power and the deterioration of receiving sensitivity. Further, when the switch is changed over, power is consumed. Therefore, the life of a battery shortens.
The present invention has been proposed to solve the above-mentioned problems. One preferred embodiment of the present invention will be described with reference to the drawings. The structure of a dual-band circulator corresponding to two frequency bands of a PDC/ 800 MHz band and a PHS/1.9 MHz band is shown in FIG. 3. A circulator component 101 for the PDC/ 800 MHz band is constituted by a ferrite disk 102 and a network-shaped central conductor 103 bonded thereto. The circulator component 101 for the PDC/ 800 MHz band uses 810 MHz to 830 MHz for a receiving band and 940 MHz to 960 MHz for a transmitting band. Therefore, in order to cover all transmitting and receiving bands, it is necessary for the circulator component 101 for the PDC/ 800 MHz band to be adapted to 810 MHz to 960 MHz.
The pass bandwidth of the circulator is usually about 80 MHz. As shown in FIG. 4, a coil 107 and a condenser 108 are connected in series to the input/ output terminals 104, 105, 106 of the circulator 101. This is because it is necessary to produce a Chebyshev characteristic in a broad band. Therefore, this can ensure the bandwidth of 150 MHz necessary for the circulator 101 for the PDC/ 800 MHz band. The coil 107 and the condenser 108 are housed on a packaging substrate 125.
Next, the structure of a circulator component 109 for the 1.9 MHz band will be described with reference to FIG. 5. A ring-shaped dielectric plate 111 surrounds the outer periphery of a ferrite disk 110. A central conductor 112 is formed on the ferrite disk 110 and an electrode 113 is formed on the dielectric plate 111 to produce capacitance 114. The central conductor 112 and the capacitance 114 constitute an equivalent low-pass filter. This increases the amount of attenuation in the frequency band 2 or 3 times that of the pass band to prevent harmonics. Also, this simple structure can simplify the manufacturing process.
The circulator component 101 for the 800 MHz band and the circulator component 109 for the 1.9 GHz band are arranged to sandwich a grounded substrate 115 having conductive films on both surfaces. Spacers 124 are used for evening the tops of the circulator components 101, 109. The two circulator components 101, 109 are connected to input/output terminals via pins 130.
The higher the frequency is, the smaller the size of the circulator component in the radial direction is. When a circulator component for the 800 MHz band and a circulator component the 1.9 GHz band are constituted by use of a distributed constant type component, the circulator component for the 1.9 GHz band is smaller in size in the radial direction than the circulator component for the 800 MHz band. On the other hand, a lumped constant type circulator component can be made smaller in size in the radial direction than a distributed constant type circulator component. If a circulator component for the 800 MHz band uses a lumped constant type component and a circulator component for the 1.9 GHz band uses a distributed constant type component, the two circulator components are nearly same size in the radial direction. That is, this is a suitable structure for overlaying one circulator component on the other one. Further, since the distributed type circulator component is thin in structure, the distributed constant type circulator component can be made tall as compared with a combination of two lumped constant type circulator components.
The terminal 106 of the circulator component 101 (for the 800 MHz band) and the terminal 116 of the circulator component 109 (for the 1.9 GHz band), as shown in FIG. 6, are in parallel connected to a common terminal 121 via an impedance matching circuit. The impedance matching circuit comprises coils 119 and a condenser 120. The coils 119 and the condenser 120 are mounted on the housing substrate 125. It is possible to control impedance matching easily by freely selecting the constant of the coils 119 and the condenser 120.
A permanent magnet 122 is arranged over the ferrite disk 102 with a predetermined gap between them to produce a desired magnetic field. Another permanent magnet 122 is arranged below the ferrite disk 109 with a predetermined gap between them to produce a desired magnetic field. The permanent magnets 122 and the ferrite disks 102, 109 are inserted in metallic cases with yokes 123.
In this connection, in the above-mentioned preferred embodiment, two circulator components 101, 109 are sandwiched by two permanent magnets 122, but as shown in FIG. 8, one permanent magnet 129 may be sandwiched by two circulator components 101, 109.
An RF signal inputted from the common terminal 121 is outputted to terminals 117, 127. An RF signal inputted from terminals 126, 118 is outputted to the common terminal 121. The RF signal inputted from the common terminal 121 is outputted to terminals 126, 118 by reversing the direction of the magnetic field. The RF signal entered from the terminals 117, 127 can also be outputted to the common terminal 121.
As a specific example, the circulator for the 800 MHz band is constituted by a ferrite having a diameter () of 4 mm and a magnetic field density (4πMs) of 760 Gauss and an central conductor having a width (d) of 1 mm. Capacitance (C1) for forming an LPF is 12 pF and the inductance (Ls) of a coil for a broad band is 10 nH and the capacitance (Cs) of a condenser for a broad band is 1.5 pF. The circulator for the 1.9 GHz band is constituted by a ferrite having a diameter () of 3.5 mm and a magnetic field density (4πMs) of 550 Gauss and an central conductor having a width (d) of 0.5 mm. The frequency characteristics in the 800 MHz band of the dual circulator in accordance with the present invention are shown in FIG. 9A and the frequency characteristics in the 1.9 GHz band thereof are shown in FIG. 9B, respectively.
FIG. 10 is an illustration showing an example in which the above mentioned dual-band circulator is applied to a transmitting and receiving device corresponding to PDC/800 MHz and a transmitting and receiving device corresponding to PHS/1.9 GHz. An antenna 135 is connected to the common terminal 121 of the dual-band circulator. An 800 MHz transmtting device 131 and an 800 MHz receiving device 134 which correspond to PDC/800 MHz are connected to the terminals 126 and 127, respectively. A 1.9 GHz receiving device 133 and a 1.9 GHz transmitting device 132 which correspond to PHS/1.9 GHz are connected to the terminals 117 and 118, respectively.
Here, considering the flow of the microwave signal of the dual-band circulator, it will be understood that the transmitting and receiving devices 131, 132, 133, 134 corresponding to two frequency bands can share one antenna. A dual-band antenna sharing device described in this preferred embodiment has little insertion loss and little power consumption as compared with a conventional dual-band antenna sharing device changed over with a selector switch.
As described above, the dual-band circulator in accordance with the present invention can also correspond to a broad band system if a primary Chebyshev circuit is added thereto. Also, the dual-band circulator in accordance with the present invention can prevent higher harmonics by use of a distributed constant type non-reversible circuit component. Also, since the dual-band circulator in accordance with the present invention has a simple structure, it is possible to reduce costs and to increase productivity. Further, according to the present invention, two non-reversible circuit components are connected in parallel via a impedance matching circuit including a coil, a condenser, and the like and hence an impedance matching can be controlled easily.
Further, according to the present invention, if non-reversible circuit devices are used as antenna sharing devices corresponding to two frequencies, they can constitute antenna sharing devices having no power consumption and little insertion loss.

Claims

A dual-band non-reversible circuit device having in one case a first non-reversible circuit component and a second non-reversible circuit component each of which comprises at least a ferrite plate (102, 110), a central conductor (103, 112), a magnet (122, 129), and a grounded conductor (115), wherein:

each of the non-reversible circuit components is operated in a different frequency band in the magnetic circuit,

the first non-reversible circuit component is constituted by using a lumped constant type and has a first frequency band, the first non-reversible circuit component operating toward the low frequency side, and

the second non-reversible circuit component is constituted by using a distributed constant type and has a second frequency band, the second non-reversible circuit component operating toward the high frequency side.
A device as claimed in claim 1, wherein a primary Chebyshev circuit is connected to the input/output terminals (126, 127; 117, 118) of at least one among the first and the second non-reversible circuit components, the primary Chebyshev circuit comprising an inductor and a condenser.
A device as claimed in claim 1 or 2, wherein the first and second non-reversible circuit components are connected in parallel to each other via an impedance matching circuit (119, 120) for matching impedance.
A device as claimed in claim 3, wherein:
an antenna (135) is connected to the impedance matching circuit (119, 120) such that the antenna (135) is connected in common to the first and the second non-reversible circuit components,

a transmitting device (131) and a receiving device (134) corresponding to the first frequency band are connected to the terminal (126, 127) of the first non-reversible circuit component, and

a transmitting device (132) and a receiving device (133) corresponding to the second frequency band are connected to the terminal (117, 118) of the second non-reversible circuit component.
A device as claimed in one of claims 1 to 4, wherein the first and second non-reversible circuit components are circulators (101, 109).
A device as claimed in one of claims 1 to 4, wherein the first and second non-reversible circuit components are isolators.
A device as claimed in one of claims 1 to 4, wherein either the first or the second non-reversible circuit components is an isolator and the other is a circulator (101, 109).