JP3521868B2 - Filter, antenna duplexer and communication device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter, an antenna duplexer and a communication device used in a microwave band, for example.

[0002]

2. Description of the Related Art In recent years, along with the downsizing of communication equipment such as mobile phones, the size of filters and antenna duplexers has been reduced, and the distance between components mounted on a printed circuit board in the communication equipment has been reduced. Is also getting smaller.

By the way, in order to form an inductance, a winding type coil (air core coil, bobbin coil, etc.) around which a conductive wire is wound, or a chip type coil (laminated coil, thin film coil, spiral coil, etc.) is generally used. To be A plurality of these coils are used in one filter. For example, the actual Kaihei 5-4603
In the publication, a plurality of air-core coils are integrated to reduce the number of parts, and the air-core coils are fitted in the coil housing to prevent fluctuations in filter characteristics, or adjacent air-core coils are attached. There is described a filter in which the axis of the spiral portion of is displaced and arranged.

[0004]

However, when a plurality of coils are used in one filter and the distance between the components becomes small, unnecessary electromagnetic field coupling occurs between the coils. This unnecessary electromagnetic field coupling causes deterioration of filter characteristics (especially deterioration of attenuation characteristics). Also,
Even in the case of an antenna duplexer in which two filters, a transmission filter and a reception filter, share an antenna terminal, when the distance between the components becomes small, the coil of the transmission filter and the coil of the reception filter are unnecessary. There is a problem that the coupling characteristics are caused and the isolation characteristic between the transmission band and the reception band is deteriorated.

When a plurality of air-core coils are integrated in order to reduce the number of parts as in the filter described in Japanese Utility Model Laid-Open No. 5-4603, the air-core coil itself becomes large and the automatic mounting machine is installed. It becomes difficult to use and mount on a board. In addition, if a coil housing portion (hole or recess) for fitting the air-core coil is formed on the substrate in order to make the fluctuation of the filter characteristic less likely to occur, the problem of increased cost of the substrate occurs. Further, if the axes of the spiral portions of the adjacent air core coils are displaced in order to prevent the filter characteristics from changing, a plurality of air core coils will be arranged in a zigzag manner. Therefore, useless space is generated on the circuit board, which hinders downsizing of the filter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a filter, an antenna duplexer, and a communication device which are small in size and inexpensive, and which suppress unnecessary electromagnetic field coupling between coils.

[0007]

[0008]

In order to achieve the above object, a filter according to the present invention comprises at least one resonator and at least two inductance elements, and one of the inductances of the adjacent inductance elements. element is a air-core coil, the other inductance element Ri Ah in the laminated coil, the coil axis direction of the air-core coil
It differs by more than 45 degrees to the coil axis direction of the laminated coil.
Characterized that you have been urchin arranged.

Further, the filter according to the present invention is a band pass type filter having at least one resonator, and the input side and output side reactance elements for matching with an external circuit are inductance elements. , in two air-core coil while the inductance element of the inductance elements, and the other one of the inductance elements Ri Ah in the laminated coil, the coil axis direction of the air-core coil
The orientation is different from the coil axis direction of the laminated coil by 45 degrees or more.
Characterized that you have arranged so that.

Here, a dielectric resonator or the like is used as the resonator.

With the above construction, unnecessary electromagnetic field coupling between the coils can be suppressed and excellent filter characteristics can be obtained. Also, since the coil is small, it is possible to use an automatic mounting machine. Moreover, the coils can be densely mounted on the circuit board, and a wasteful space is unlikely to occur on the circuit board.

[0012]

[0013]

Further, since the antenna duplexer and the communication device according to the present invention are provided with the filter having the above-mentioned characteristics, unnecessary electromagnetic field coupling between the coils can be suppressed and excellent high frequency characteristics can be obtained.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a filter, an antenna duplexer and a communication device according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment, FIGS. 1 to 9] FIG. 1 is a plan view of an antenna duplexer 1 in which components are mounted on a circuit board 40. In the antenna duplexer 1, the transmission side circuit 57 is electrically connected between the transmission terminal Tx and the antenna terminal ANT, and the reception side circuit 58 is electrically connected between the reception terminal Rx and the antenna terminal ANT. is doing. The antenna duplexer 1 outputs the transmission signal from the transmission system circuit to the transmission terminal Tx to the antenna terminal ANT via the transmission side circuit 57, and also receives the reception signal from the antenna terminal ANT to the reception side circuit. The signal is output from the receiving terminal Rx to the receiving system circuit via 58.

FIG. 2 is an electric circuit diagram of the antenna duplexer 1. The transmission side circuit 57 is a variable frequency band stop filter circuit. The band elimination filter circuit 57 includes a resonance circuit
The resonator 2 is connected in stages and electrically connected to the transmission terminal Tx via the resonance capacitor C1 and the antenna terminal ANT via the resonance capacitor C2 and the matching coil L4. And the resonator 3 that has been formed. The matching coil L4 functions as a reactance element for phase-combining the transmission side circuit 57 and the reception side circuit 58. The resonance capacitors C1 and C2 are capacitors that determine the amount of stopband attenuation. Resonator 2
The series resonance circuit of the resonance capacitor C1 and the resonance capacitor C1 is coupled to the series resonance circuit of the resonator 3 and the resonance capacitor C2 by the coupling coil L.
It is electrically connected via 1. Further, capacitors C5 and C6 are electrically connected in parallel to these two series resonance circuits, respectively.

As shown in FIG. 1, the coupling coil L1 and the matching coil L4 are air core coils formed by winding a copper wire or the like. In the horizontal direction, the coil axis direction of the coil L1 is 9 with respect to the coil axis direction of the coil L4.
The coils L1 and L4 are mounted on the circuit board 40 so that they differ by 0 degrees. As a result, the adjacent coils L1 and L
Unnecessary electromagnetic field coupling between the four can be suppressed, and deterioration of the attenuation characteristics of the band elimination filter circuit 57 can be prevented.

As shown in FIG. 2, at the intermediate connection point between the resonator 2 and the resonance capacitor C1, a PIN diode D1 which is a reactance element has its cathode grounded via a frequency varying capacitor C3. 2 is electrically connected in parallel. On the other hand, at an intermediate connection point between the resonator 3 and the resonance capacitor C2, a PIN diode D2 is electrically connected in parallel to the resonator 3 via a frequency variable capacitor C4 with its cathode grounded. There is. The frequency variable capacitors C3 and C4 are capacitors for changing the two attenuation pole frequencies of the attenuation characteristic of the frequency variable band stop filter circuit 57, respectively. A choke coil L15 is connected between the anode of the PIN diode D2 and the ground.

The voltage control terminal CONT1 is electrically connected to the intermediate connection point between the anode of the PIN diode D1 and the frequency variable capacitor C3 via the control voltage supply resistor R1, the bypass capacitor C22 and the choke coil L2, and is also controlled. It is electrically connected to an intermediate connection point between the anode of the PIN diode D2 and the frequency varying capacitor C4 via the voltage supply resistor R1, the bypass capacitor C22 and the choke coil L3.

A capacitor C15 is electrically connected between the ground and the antenna terminal ANT.
The capacitor C15 constitutes a T-shaped phase circuit together with the matching coil L4 of the transmission side circuit 57 and the matching coil L5 of the reception side circuit 58.

On the other hand, the receiving side circuit 58 is a variable frequency band pass filter circuit. Band pass filter circuit 58
Is a resonance circuit in which three stages are coupled, and the resonance coil L
Resonator 4 electrically connected to antenna terminal ANT via 9 and matching coil L5, and resonance coil L
10 and a resonator 6 electrically connected to the receiving terminal Rx via the matching coil L11, and a resonator 5 electrically connected between the resonators 4 and 6 via coupling capacitors C11 and C12. Have

The matching coils L5 and L11 function as input-side and output-side reactance elements for matching the frequency variable band pass filter circuit 58 and an external circuit, respectively. Matching coils L5, L11
Is an air-core coil in which a copper wire or the like is wound, as shown in FIGS. Then, the matching coils L5, L
In No. 11, the coil axis directions are parallel to each other and the winding directions are different from each other. 5 and 6, arrows K1 and K2 indicate the directions in which the high-frequency current flows through the coils L5 and L11, respectively. Therefore, the directions of the magnetic fields generated by the matching coils L5 and L11 are opposite and cancel each other. As a result, the matching coils L5 and L11 are not electromagnetically coupled to each other, and deterioration of the attenuation characteristics of the bandpass filter circuit 58 can be prevented.

Further, the resonance coils L9 and L10 are laminated coils, as shown in FIGS. 7 and 8 show the resonance coil L9 as a typical example. As shown in FIG. 8, the resonance coils L9 and L10 are formed by forming the coil conductor patterns 43a to 43d on each of the ceramic green sheets 42 by a method such as a printing method, and then forming the coil conductor patterns 43a to 43d. Is a via hole 47 provided in the ceramic green sheet 42.
The ceramic green sheets 42 are stacked and integrally fired so as to form a spiral coil 43 by being electrically connected in series via the sinter laminated body. External terminals 48 and 49 are formed on the left and right ends of the sintered laminated body, respectively, as shown in FIG. One end of the coil conductor pattern 43a is connected to the external terminal 48, and one end of the coil conductor pattern 43d is connected to the external terminal 49. A mark 50 for recognizing the winding direction of the spiral coil 43 is printed on the upper surfaces of the resonance coils L9 and L10.

When the resonance coils L9 and L10 are mounted on the circuit board 40, the coil axis direction of the spiral coil 43 is perpendicular to the circuit board 40. Therefore,
The matching coils L5 and L11 whose coil axis directions are parallel to the circuit board 40 and the resonance coils L9 and L10 are mounted so that their coil axis directions differ from each other by 90 degrees. As a result, unnecessary electromagnetic field coupling between the adjacent coils L5 and L9 or between the adjacent coils L11 and L10 can be suppressed, and deterioration of the attenuation characteristics of the bandpass filter circuit 58 can be further prevented.

The matching coils L4 and L5 are
The coil axis directions differ from each other by 90 degrees, and the winding directions also differ from each other. The matching coil L4 constitutes a part of the transmission side circuit 57, and the matching coil L5
Since it constitutes a part of the reception side circuit 58, unnecessary electromagnetic field coupling between the transmission side circuit 57 and the reception side circuit 58 can be suppressed, and the isolation between the transmission band and the reception band can be achieved. It is possible to prevent deterioration of characteristics.

At the intermediate connection point between the resonator 4 and the resonance coil L9, a series circuit of the frequency varying capacitor C7 and the PIN diode D4 is electrically connected to the resonator 4 with the cathode of the PIN diode D4 grounded. Are connected in parallel. At the intermediate connection point between the resonator 5 and the coupling capacitors C11 and C12, a series circuit of the frequency varying capacitor C8 and the PIN diode D5 is electrically parallel to the resonator 5 with the cathode of the PIN diode D5 grounded. Connected to. At the intermediate connection point between the resonator 6 and the resonance coil L10, a series circuit of a frequency varying capacitor C9 and a PIN diode D6 is electrically parallel to the resonator 6 with the cathode of the PIN diode D6 grounded. Connected.

The voltage control terminal CONT2 is electrically connected to the intermediate connection point between the anode of the PIN diode D4 and the frequency varying capacitor C7 via the bypass capacitor C23 and the choke coil L6, and the bypass capacitor C2.
PIN diode D5 via 3 and choke coil L7
Is electrically connected to an intermediate connection point between the anode of the capacitor and the frequency varying capacitor C8, and further, the bypass capacitor C23
And the anode of the PIN diode D6 and the intermediate connection point of the frequency varying capacitor C9 via the choke coil L8.

Here, in the resonators 2 to 6, for example, FIG.
And as shown in FIG. 4, a λ / 4 coaxial dielectric resonator is used. 3 and 4 show the resonator 2 as a typical example. The dielectric resonators 2 to 6 include a tubular dielectric 17 formed of a high dielectric constant material such as TiO ₂ -based ceramic, an outer conductor 18 provided on an outer peripheral surface of the tubular dielectric 17, and a tubular dielectric. The inner conductor 19 is provided on the inner peripheral surface of the dielectric 17. The outer conductor 18 is one opening end face 1 of the dielectric 17.
7a (hereinafter referred to as the open side end surface 17a), the inner conductor 1
9 is electrically opened (separated) from the other opening end face 17
b (hereinafter referred to as short-circuit side end face 17b), the inner conductor 19
Is electrically short-circuited (conducted). Dielectric resonator 2
Is electrically connected to the resonance capacitor C1 via the conductor 20 and the like at the open side end face 17a. These dielectric resonators 2 to 6 are soldered together by an outer conductor 18 to be integrated.

Next, the function and effect of the antenna duplexer 1 having the above configuration will be described. The trap frequency of the variable frequency band stop filter circuit 57, which is the transmission side circuit, is
Depending on the respective resonance frequencies of the resonance system composed of the frequency variable capacitor C3, the resonance capacitor C1 and the resonator 2, and the resonance system composed of the frequency variable capacitor C4, the resonance capacitor C2 and the resonator 3. Decided. Then, when a positive voltage is applied as the control voltage to the voltage control terminal CONT1, the PIN diodes D1 and D2 are turned on. Therefore, the frequency changing capacitors C3 and C4
Are grounded via the PIN diodes D1 and D2, the frequencies of the two attenuation poles are both low, and the transmission side circuit 5
The pass band of 7 is low.

On the contrary, when a negative voltage is applied as the control voltage, the PIN diodes D1 and D2 are turned off.
Instead of applying the negative voltage, the voltage control terminal CON
100k control circuit to supply control voltage to T1
High impedance over ohm, voltage control terminal CO
The control voltage may be set to 0 V and the PIN diodes D1 and D2 may be turned off by preventing the voltage from being applied to NT1. As a result, the frequency varying capacitors C3 and C4 are opened, the two attenuation pole frequencies both increase, and the pass band of the transmitting side circuit 57 increases. Thus, the transmission side circuit 57 can have two different pass band characteristics by grounding or opening the band varying capacitors C3 and C4 by voltage control.

On the other hand, the pass frequency of the frequency variable band pass filter circuit 58, which is the receiving side circuit, is the resonance system constituted by the frequency varying capacitor C7, the resonance coil L9 and the resonator 4, and the frequency varying capacitor C8. It is determined by the resonance frequency of each of the resonance system composed of the resonator 5 and the resonance system composed of the frequency varying capacitor C9, the resonance coil L10, and the resonator 6. Then, when a positive voltage is applied as the control voltage to the voltage control terminal CONT2, the PIN diodes D4, D5, D6 are turned on. Therefore, the frequency changing capacitors C7, C8, C9
Are grounded through the PIN diodes D4, D5 and D6, respectively, and the passing frequency becomes low. On the contrary, if a negative voltage is applied as the control voltage, the PIN diodes D4, D5,
D6 is turned off. As a result, the frequency varying capacitors C7, C8, C9 are opened, and the passing frequency becomes high. In this way, the receiving side circuit 58 can have two different pass band characteristics by grounding or opening the frequency varying capacitors C7 to C9 by voltage control.

This frequency variable band pass filter circuit 58
In accordance with the switching between the high and low pass bands of the transmission side circuit 57, the band pass frequency is lowered when the low frequency pass band is selected as the transmission band, and the high frequency pass band is selected as the transmission band. At this time, the voltage is controlled so as to increase the band pass frequency.

Then, unnecessary electromagnetic field coupling between the adjacent coils L1 and L4, between L5 and L11, between L5 and L9, between L11 and L10, and between L4 and L5 can be suppressed. As a result, it is possible to obtain the antenna duplexer 1 that includes the transmission side circuit 57 and the reception side circuit 58 having excellent filter characteristics and has an excellent isolation characteristic between the transmission terminal Tx and the reception terminal Rx. . FIG. 9 shows the isolation characteristic of the antenna duplexer 1 (S2
1) (see solid line 59). Coil L1 for comparison
And L4 are parallel to each other in the coil axis direction, and the coils L5 and L11 are wound in the same winding direction, and the isolation characteristics of the antenna duplexer that does not suppress unnecessary electromagnetic field coupling between the coils are also described. (See dotted line 60).

Further, since the coils L1, L4, L5, L11 and the like are small in size, an automatic mounting machine can be used. Moreover, the coils L1, L4, etc. can be densely mounted on the circuit board 40, and a wasteful space on the circuit board 40 is unlikely to occur.

[Second Embodiment, FIG. 10 and FIG. 11] Second Embodiment
The embodiment is a further miniaturization of the antenna duplexer 1 of the first embodiment. FIG. 10 is a plan view of the antenna duplexer 61 in which each component is mounted on the circuit board 40.
FIG. 11 is an electric circuit diagram thereof. In FIGS. 10 and 11, R2 to R5 are resistors and C24 is a capacitor. Note that in FIGS. 10 and 11, FIGS.
The same reference numerals are given to those corresponding to, and duplicate description will be omitted.

The receiving side circuit 58 is a variable frequency band pass filter circuit in which resonant circuits are coupled in two stages. The matching coils L5 and L11 function as input-side and output-side reactance elements for matching the variable frequency band pass filter circuit 58 and an external circuit, respectively. The matching coil L5 is an air-core coil, and its coil axis direction is parallel to the circuit board 40. On the other hand, the matching coil L11 is a laminated coil, and its coil axis direction is perpendicular to the circuit board 40.

Therefore, the matching coils L5 and L11
Are mounted so that the coil axis directions differ from each other by 90 degrees. As a result, unnecessary electromagnetic field coupling between the coils L5 and L11 can be suppressed, and deterioration of the attenuation characteristics of the receiving side circuit 58 can be further prevented. As the coil L11, as shown in FIG. 10, an air core coil having a different winding direction may be used for the coil L5.

[Third Embodiment, FIG. 12] The third embodiment shows an embodiment of a communication device according to the present invention, and a mobile phone will be described as an example. FIG. 12 shows a mobile phone 1.
It is an electric circuit block diagram of the RF part of 20. In FIG. 12, reference numeral 122 is an antenna element, 123 is a duplexer, 131 is a transmission side isolator, 132 is a transmission side amplifier, 133 is a transmission side interstage bandpass filter, and 134.
Is a mixer on the transmitting side, 135 is an amplifier on the receiving side, 136 is a bandpass filter for inter-stage receiving side, 137 is a mixer on receiving side,
Reference numeral 138 is a voltage controlled oscillator (VCO), and 139 is a local band pass filter.

As the duplexer 123, the antenna duplexers 1 and 61 of the first and second embodiments can be used here. By mounting these antenna duplexers 1 and 61, it is possible to realize a mobile phone having excellent isolation characteristics.

[Other Embodiments] The filter, the antenna duplexer, and the communication device according to the present invention are not limited to the above embodiments, but can be variously modified within the scope of the gist thereof.

For example, in the above embodiment, the coil axial directions of the adjacent coils are set to differ from each other by 90 degrees, but it is not always necessary to set them to 90 degrees, and they are set to differ by 45 degrees or more. If so, there is an effect of suppressing unnecessary electromagnetic field coupling. Further, in the above embodiment, the coil axis directions of the coils L1 and L4 of the transmission side circuit may be parallel to each other and the winding directions may be different from each other. Alternatively, the coil axis directions of the coils L5 and L11 of the receiving side circuit may be set to 4
You may set so that it may differ by 5 degrees or more.

Further, in addition to the PIN diode, a field effect transistor or a variable capacitance diode may be used. As the resonator, a distributed constant line or the like may be used in addition to the dielectric resonator.

[0044]

As is apparent from the above description, according to the present invention, the filter has at least two coils, and even if the filter size is reduced and the distance between the parts is reduced, the two Unnecessary electromagnetic field coupling between the coils can be suppressed. Therefore, it is possible to obtain a small-sized and inexpensive filter or antenna duplexer having excellent filter characteristics.

Further, according to the present invention, in the antenna duplexer in which the first filter and the second filter each having at least one resonator and at least two coils share one common terminal, Unnecessary electromagnetic field coupling between the coil disposed on the shared terminal side of the first filter and the coil disposed on the shared terminal side of the second filter can be suppressed. As a result, it is possible to obtain an antenna duplexer or a communication device having excellent isolation characteristics.

[Brief description of drawings]

FIG. 1 is a plan view showing a mounting structure of an embodiment of an antenna duplexer according to the present invention.

FIG. 2 is an electric circuit diagram of the antenna duplexer shown in FIG.

FIG. 3 is a perspective view showing an example of a resonator used in the antenna duplexer shown in FIG.

FIG. 4 is a sectional view of the resonator shown in FIG.

5 is a perspective view showing an example of an air core coil used in the antenna duplexer shown in FIG. 1. FIG.

6 is a perspective view showing an example of another air-core coil used in the antenna duplexer shown in FIG.

7 is a perspective view showing an example of a laminated coil used in the antenna duplexer shown in FIG.

8 is an exploded perspective view showing the structure of the laminated coil shown in FIG.

9 is a graph showing isolation characteristics of the antenna duplexer shown in FIG.

FIG. 10 is a plan view showing a mounting structure of another embodiment of the antenna duplexer according to the present invention.

11 is an electric circuit diagram of the antenna duplexer shown in FIG.

FIG. 12 is a block diagram showing an embodiment of a communication device according to the present invention.

[Explanation of symbols]

1,61 ... Antenna duplexer 2 to 6 ... Coaxial dielectric resonator 57 ... Transmission side circuit (frequency variable band stop filter circuit) 58 ... Receiving side circuit (frequency variable band pass filter circuit) L1 ... Coupling coil L4, L5, L11 ... Matching coil L9, L10 ... Resonance coil Tx ... Transmission terminal Rx ... Reception terminal ANT ... Terminal for antenna 120 ... mobile phone 123 ... Duplexer

Continuation of front page (51) Int.Cl. ⁷ identification code FI H01P 1/213 H04B 1/48 H04B 1/48 H01F 15/00 D (58) Fields investigated (Int.Cl. ⁷ , DB name) H01P 1 / 20-1/219 H01P 7/00-7/10 H01F 5/00 H01F 17/02 H01F 27/00 H04B 1/48

Claims (5)

(57) [Claims] 1. An at least one resonator and at least two inductance elements, wherein one of the adjacent inductance elements is an air-core coil and the other inductance element is a laminated coil.
The coil axis direction of the air-core coil of the laminated coil
They are arranged so that they differ by 45 degrees or more with respect to the coil axis direction.
Filter which is characterized Zheng Rukoto. 2. A bandpass filter having at least one resonator, wherein input-side and output-side reactance elements for matching with an external circuit are inductance elements, and one of the inductance elements is used. the inductance element is an air core coil, and the other one of the inductance elements Ri Ah in the laminated coil, the air core carp
The coil axis direction of the
Filter, characterized that you have been placed more than 45 degrees different and. 3. The filter according to claim 1, wherein the resonator is a dielectric resonator. 4. An antenna duplexer comprising a first filter and a second filter, wherein at least one of the first filter and the second filter is one of the first to third embodiments. An antenna duplexer, which is the filter according to any one of the above. 5. The filter according to claim 1,
Alternatively, a communication device including at least one of the antenna duplexers according to claim 4.