JPH05235798A - Antenna duplexer - Google Patents

Abstract

(57) [Abstract] [Object] An object of the present invention is to provide an antenna duplexer having a simple configuration of a reception filter. [Structure] The reception filter of the antenna duplexer of the present invention is
The first parallel resonant circuit 20 and the capacitor C ₂ are connected in series between the branching section 2 to which the antenna 1 is connected and the terminal 4 to which the receiver is connected. In addition, there is a second parallel resonant circuit 21 that couples with the resonant circuit 20. The resonance circuit 20 resonates at harmonics of the transmission frequency, and the resonance circuit 21 resonates at the transmission frequency. Further, the resonance circuit 20, the resonance circuit 21, and the capacitor C ₂ equivalently form a circuit having a small insertion impedance at the reception frequency. Resonance circuit 20 and resonance circuit 21
The harmonics of the transmitted signal and the transmitted signal are blocked by so that only the received signal passes. [Effect] Since the circuit configuration is simple and the number of coils and capacitors is small, it is possible to contribute to downsizing of the antenna duplexer. Of course, the price will be lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a reception filter of an antenna duplexer.

[0002]

2. Description of the Related Art In a mobile radio device, for example, a cordless parent-child telephone and a car telephone, simultaneous transmission and reception are performed for simultaneous communication, but an antenna is commonly used for transmission and reception. In that case, an antenna duplexer that separates the transmission signal and the reception signal is used so that the transmission signal does not mix with the receiver side and the reception signal mixes with the transmitter side.

FIG. 7 is an illustration of an antenna duplexer.
It has a transmitter-side and receiver-side branch 2 to which the antenna 1 is connected, and a branch 2 between the branch 2 and the terminal 3 connected to the transmitter.
And a transmission filter 5 between the terminal 4 to which the receiver and the receiver are connected,
The reception filter 6 is connected, and both filters 5 and 6 are connected.
Thus, the transmission signal and the reception signal are separated.

FIG. 8 is an example of a circuit diagram of a reception filter of a conventional antenna duplexer. A plurality of parallel resonance circuits 10 connected between the branching section 2 and the terminal 4 and the ground and the resonance circuit thereof are shown. band-pass filter consisting of the coupling capacitor C ₁₀ for coupling the 10, and a parallel resonance circuit 11 connected to the band-pass filter between the branch section 2. The bandpass filter passes only the reception signal except unnecessary waves, and the parallel resonant circuit 11 has a role of blocking the transmission signal.

However, such a receiving filter requires a large number of coils used for the resonance circuits 10 and 11, and the resonance circuits 10 and 11 also need to be housed in a case so as not to interfere with each other. growing. This is not desirable for downsizing the duplexer.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an antenna duplexer having a simplified shape of a reception filter and a reduced shape.

[0007]

SUMMARY OF THE INVENTION The present invention has a transmitter-side and receiver-side branch portion for connecting an antenna, and a transmission filter between the branch portion and the transmitter and between the branch portion and the receiver, respectively. In an antenna duplexer having a reception filter, the reception filter is coupled to a first parallel resonance circuit, which is composed of a coil connected between a branch unit and the receiver and a capacitor connected in parallel to the coil, and a first parallel resonance circuit. A second parallel resonant circuit, and another capacitor connected in series with the coil of the first parallel resonant circuit. One side of the first and second parallel resonant circuits resonates at the transmission frequency, and the other side of the parallel resonant circuit. Alternatively, the first and second parallel resonant circuits resonate at a desired frequency for removing harmonic components of the transmission frequency, and the additional capacitor forms an equivalent circuit in which the insertion impedance becomes small at the reception frequency. And wherein the are. First
The second parallel resonance circuit is used as a trap circuit with a large insertion impedance. Normally, this resonance frequency is adjusted to the frequencies of the fundamental signal and harmonic signals on the transmitter side to eliminate the signal on the transmitter side. To do. However, since this frequency can be set arbitrarily, other unnecessary signals can be effectively removed. Further, since the first and second parallel resonant circuits and the other capacitor form a resonant circuit with a small insertion impedance, they are usually used as a bandpass filter by matching this resonant frequency with the reception frequency. The bandpass filter can also be formed by connecting another coil in series to the coil of the first parallel resonance circuit and forming the other coil and the first and second parallel resonance circuits. Further, the selectivity of the bandpass filter is improved by providing a parallel resonance circuit between the output side of the reception filter and the ground.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an antenna duplexer of the present invention will be described below with reference to FIG. FIG. 1 specifically shows a circuit diagram of the reception filter. A coil L ₁ is provided between the branching part 2 connected to the antenna 1 and the terminal 4 connected to the receiver.
And the capacitor C ₁ is connected in parallel with the coil L ₁ to form the first parallel resonant circuit 20.

A second parallel resonant circuit 21 electromagnetically coupled to the first resonant circuit 20 is formed of a coil L ₂ and a capacitor C ₃ . First parallel resonant circuit 20
Resonates at twice the transmission frequency, and the second parallel resonance circuit 21 resonates at the transmission frequency. Furthermore, the resonance circuit 20
A circuit having a small insertion impedance at the reception frequency is equivalently formed by the capacitor C ₂ , the resonance circuit 20, and the resonance circuit 21 which are connected in series with each other. A coil L is provided between the output side of the reception filter configured as above and the ground.
_A parallel resonance circuit 22 including ₉ and a capacitor C ₉ is connected. The resonance circuit 22 is coupled to the capacitor C ₂ via the coupling coil L ₈ , and the terminal 4 is connected to the tap of the coil L ₉ . Then, the resonance circuit 22 has a maximum insertion impedance at the reception frequency.

FIG. 2 is an equivalent circuit diagram of FIG. 1. A receiving filter is constructed by connecting the first parallel resonant circuit 20 and the second parallel resonant circuit 21 in series on both sides of the capacitor C ₂ . .. The reception filter includes a capacitor C ₂ and a resonance circuit 20, and a capacitor C ₂ and a resonance circuit 21.
It may be considered to be composed of a set of resonant circuits. Since each resonance circuit has a frequency at which the insertion impedance becomes maximum and a frequency at which the insertion impedance becomes minimum, the circuit of FIG. 2 can reduce the insertion impedance at the reception frequency by using the frequency at which the insertion impedance becomes minimum.

In the resonance circuit composed of the capacitor C ₂ and the resonance circuit 21, the frequency f ₁ at which the insertion impedance becomes minimum is expressed by the equation (1). f ₁ = 1 / 2π {L ₂₂ · (C ₂ + C ₃₃ )} ^1/2 (1) The frequency f ₂ at which the insertion impedance becomes maximum is given by the equation (2). f ₂ = 1 / 2π (L ₂₂ · C ₃₃ ) ^1/2 (2)

In the resonance circuit 20, the frequency f ₃ at which the insertion impedance becomes maximum is expressed by the equation (3). f ₃ = 1 / 2π (L ₁₁ · C ₁₁ ) ^1/2 (3) In the formulas (1), (2) and (3), L ₂₂ and L ₁₁ are coils L ₂₂ and L _{11 respectively.} Inductance value, C ₂
And C ₃₃ represent the capacitance values of the capacitors C ₂ and C ₃₃ , respectively.

In the embodiment, the frequency f ₁ is matched with the receiving frequency, the frequency f ₂ is matched with the transmitting frequency, and the frequency f ₃ is matched with twice the transmitting frequency. The frequency at which the insertion impedance of the resonance circuit including the capacitor C ₂ and the resonance circuit 20 is minimized is not used, but this frequency may of course be matched with the reception frequency.

[0014] Thus, by either the resonance of the capacitor C ₂ of the parallel resonant circuits 20 and 21 for equivalently connected in series across the capacitor C _2, it can be reduced insertion impedance at the reception frequency. Further, at the transmission frequency or the frequency twice as high as the transmission signal, the parallel resonant circuits 21 and 20 resonate, so that the insertion impedance becomes large. Therefore,
The received signal is efficiently received through the antenna 1,
The transmitted signal does not enter the receiver through terminal 4. Also, twice the higher harmonics of the transmitted signal will not enter the receiver.

When the coupling between the coil L ₁ and the coil L ₂ is strengthened to bring the coupling coefficient close to 1, the attenuation at the transmission frequency increases, but at the same time, the attenuation of the reception frequency also occurs. It is advisable to select a coupling coefficient that does not cause attenuation. Further, the resonance circuit 22 is equivalent to the coil L ₉₈ and the capacitor C including the coupling coil L _8.
It is represented in FIG. 2 as a parallel circuit consisting of ₉₉ . The resonance circuit 22 plays a role of improving the selectivity of the resonance circuit including the capacitor C ₂ used as a bandpass filter and the resonance circuit 21, but is not an essential circuit of the present invention. Coil L ₁ of the resonant circuit 20, coil L ₂ of the resonant circuit 21,
Further, the coil L ₉ and the coupling coil L ₈ of the resonance circuit 22 are
The same bobbin 51 as shown in FIG. 3, which is a front view of the bobbin.
Then, the coupling coefficient may be adjusted by the collar 52 and the winding groove 53.

FIG. 4 is a circuit diagram showing another embodiment of the antenna duplexer of the present invention, specifically showing only the circuit diagram of the receiving filter. A coil L ₃ and a capacitor C ₄ are connected in series between a branching part 2 to which the antenna 1 is connected and a terminal 4 to which the receiver is connected. A capacitor C ₅ is connected in parallel with this series circuit to connect the first and second terminals. The parallel resonant circuit 30 is formed.

A second parallel resonance circuit 31 formed of a coil L ₄ and a capacitor C ₆ is coupled to the resonance circuit 30. The resonance circuit 30 resonates at a frequency twice as high as the transmission frequency, and blocks double harmonics. In addition, the resonance circuit 31
Resonates at the transmit frequency and blocks the transmit signal. Also in this embodiment, as in the case of FIG. 1, it is possible to equivalently form a circuit having a small insertion impedance at a specific frequency, so that only the received signal can be passed by matching that frequency with the received frequency. ..

FIG. 5 is a circuit diagram showing still another embodiment of the antenna duplexer of the present invention. A coil L ₅ and a coil L ₇ are connected in series between the branching part 2 to which the antenna 1 is connected and the terminal 4 to which the receiver is connected, and a capacitor C _{7 is} connected to the coil L _5.
Are connected in parallel to form a first parallel resonant circuit 40.

A second parallel resonance circuit 41 formed of a coil L ₆ and a capacitor C ₈ is coupled to the resonance circuit 40. The first parallel resonant circuit 40 and the second parallel resonant circuit 41 resonate at a frequency twice the transmission frequency and a transmission frequency, respectively. Although FIG. 6 is an equivalent circuit diagram of FIG. 5, a first parallel resonant circuit 40 and a second parallel resonant circuit 41 are connected in series on both sides of the coil L ₇ .

The circuit of FIG. 6 has a coil L ₇ and a resonance circuit 4
0, the coil L ₇ and the resonance circuit 41 may be considered to be composed of two sets of resonance circuits. Since each resonance circuit has a frequency at which the insertion impedance becomes maximum and a frequency at which the insertion impedance becomes minimum, the frequency at which the resonance impedance becomes minimum is obtained. Can be used to reduce the insertion impedance at the reception frequency.

In the resonance circuit composed of the coil L ₇ and the resonance circuit 41, the frequency f at which the insertion impedance is minimized
_The frequency f ₅ that becomes maximum with ₄ is expressed by the equations (4) and (5). f ₄ = 1 / 2π (L ₈ · C ₈₈ ) ^1/2 (4) f ₅ = 1 / 2π (L ₆₆ · C ₈₈ ) ^1/2 (5) In addition, L ₈ is a coil L ₇ and a coil L _66. Is a series combined inductance of.

In the resonance circuit composed of the coil L ₇ and the resonance circuit 40, the frequency f at which the insertion impedance becomes maximum
₆ is expressed by equation (6). f ₆ = 1 / 2π (L ₅₅ · C ₇₇ ) ^1/2 (6) Then, match the frequency f ₄ with the reception frequency, the frequency f ₅ with the transmission frequency, and the frequency f ₆ with twice the transmission frequency. is there.

As described above, even if another coil L ₇ is connected instead of connecting the capacitor in series to the coil L ₅ of the first parallel resonant circuit 40, the parallel connection in which both ends of the coil L ₇ are equivalently connected in series is achieved. The insertion impedance can be reduced at the reception frequency by the resonance of either of the resonance circuits 40 and 41 and the coil L ₇ .

The difference between the case where a capacitor is connected in series to the coil of the first parallel resonant circuit and the case where a coil is connected is that in the former case, the frequency at which the insertion impedance becomes smaller is lower than the frequency at which it becomes larger, and in the latter case. In this case, the frequency at which the insertion impedance decreases becomes higher than the frequency at which it decreases. This is clear from the equations (1) and (2), and the equations (4) and (5). Therefore, the former is preferably used when the reception frequency is lower than the transmission frequency, and the latter is preferably used when the reception frequency is higher than the transmission frequency.

As an example of a cordless telephone, the transmission frequency of the base unit is 46.8 MHz and the reception frequency is 49.8 MH.
z, the transmission frequency of the cordless handset is 49.8 MHz, and the reception frequency is 46.8 MHz. Therefore, a capacitor is connected to the reception filter of the antenna duplexer of the cordless handset, and a coil is connected to the reception filter of the antenna duplexer of the parent device. Good to do.

In the embodiment, the parallel resonant circuit that resonates at a frequency twice as high as the transmission frequency is used to block the double harmonic. However, when another harmonic is mixed in the transmission signal more than that. The desired harmonic may be blocked by resonating with the frequency. Further, the first parallel resonant circuit may resonate at a transmission frequency, and the second parallel resonant circuit may resonate at a harmonic frequency of the transmission frequency. If the harmonics are weak, both parallel resonant circuits may be resonated at the transmission frequency. Also,
It goes without saying that the capacitor or coil connected in series to the coil of the first parallel resonant circuit may be connected to either the antenna side or the receiver side.

[0027]

As described above, the reception filter of the antenna duplexer of the present invention is composed of two parallel resonance circuits to be coupled, a capacitor or another coil connected in series to the coil of the one parallel resonance circuit. And forms an equivalent circuit in which the insertion impedance becomes small at the reception frequency. The parallel resonance with the increased insertion impedance blocks the transmission signal and the harmonics of the transmission signal, and the equivalently formed circuit reduces the insertion impedance so that only the reception signal passes.

The number of resonance circuits is reduced and the circuit structure is simplified. Also, since the number of coils is small, it can contribute to downsizing of the duplexer. Needless to say, the price will be lower.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an antenna duplexer of the present invention. Is.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is a front view of a bobbin around which a coil of the antenna duplexer of the present invention is wound.

FIG. 4 is a circuit diagram showing another embodiment of the antenna duplexer of the present invention.

FIG. 5 is a circuit diagram showing still another embodiment of the antenna duplexer of the present invention.

FIG. 6 is an equivalent circuit diagram of FIG.

FIG. 7 is an explanatory diagram of an antenna duplexer.

FIG. 8 is a circuit diagram of a conventional antenna duplexer.

[Explanation of symbols] 1 antenna 2 branching unit 3 terminal L ₁ coil C ₁ capacitor

Claims (5)

[Claims] 1. An antenna duplexer having branch portions on a transmitter side and a receiver side for connecting an antenna, and having a transmission filter and a reception filter between the branch portion and the transmitter and between the branch portion and the receiver, respectively. In the first filter, a first parallel resonant circuit including a coil connected between the branch unit and the receiver and a capacitor connected in parallel to the coil, a second parallel resonant circuit coupled to the first parallel resonant circuit, It is composed of another capacitor connected in series with the coil of the parallel resonant circuit of 1.
One side of the first and second parallel resonance circuits resonates at the transmission frequency, the other side resonates at the transmission frequency or a desired frequency for removing a harmonic component of the transmission frequency, and the first and second
2. The antenna duplexer, wherein the parallel resonance circuit and the other capacitor form an equivalent circuit whose insertion impedance becomes small at the reception frequency. 2. An antenna duplexer having branch portions on the transmitter side and the receiver side for connecting an antenna, and a transmission filter and a reception filter respectively provided between the branch portion and the transmitter and between the branch portion and the receiver. In the first parallel resonance circuit, wherein the reception filter includes a capacitor connected in parallel to a series circuit of a coil and a capacitor connected between the branch unit and the receiver, and a second parallel resonance circuit coupled to the first parallel resonance circuit. One side of the first and second parallel resonant circuits resonates at the transmission frequency, the other side resonates at the transmission frequency or a desired frequency for removing a harmonic component of the transmission frequency. An antenna duplexer characterized in that the second parallel resonant circuit and the second parallel resonant circuit form an equivalent circuit having a small insertion impedance at the reception frequency. 3. An antenna duplexer having a transmitter-side and receiver-side branching part for connecting an antenna, and having a transmission filter and a reception filter between the branching part and the transmitter and between the branching part and the receiver, respectively. In the first filter, a first parallel resonant circuit including a coil connected between the branch unit and the receiver and a capacitor connected in parallel to the coil, a second parallel resonant circuit coupled to the first parallel resonant circuit, 1 parallel resonance circuit coil and another coil connected in series,
And one side of the second parallel resonance circuit resonates at the transmission frequency, and the other side resonates at the transmission frequency or a desired frequency for removing a harmonic component of the transmission frequency, and the first and second parallel resonance circuits, The antenna duplexer, wherein the other coil forms an equivalent circuit having a small insertion impedance at the reception frequency. 4. The antenna duplexer according to claim 1, claim 2 or claim 3, wherein the coils of the first parallel resonant circuit and the second parallel resonant circuit are wound on the same bobbin. 5. The antenna duplexer according to claim 1, wherein a parallel resonance circuit is provided between the output side of the reception filter and the ground.