JP2006086871A - Composite branch circuit, chip part using the same, high-frequency module, and radio communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite branch circuit which demultiplexes a plurality of frequency bands and is capable of preventing low-frequency notches caused by a SAW duplexer 16 connected in series. <P>SOLUTION: The branch circuit is equipped with an input terminal which is not electrically connected to a GND and through which signals undergoing demultiplexing are inputted, and extracts signals belonging to a second frequency band out of first, second, and third frequency bands with frequencies gradually higher in this sequence. The branch circuit is composed of a phase adjusting circuit 6 composed of inductors, capacitors and a SAW filter 7. By this setup, the composite branch circuit is capable of restraining the distortion of harmonics from occurring without increasing a transmission loss. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

 The present invention relates to a composite demultiplexing circuit that can demultiplex a plurality of high-frequency signals in different frequency bands, and a chip component, a high-frequency module, and a wireless communication device using the same.

In recent years, cellular phones have been widely used, and functions and services of cellular phones have been improved.
A multiband mobile phone has been proposed as a new mobile phone. A multi-band mobile phone handles a plurality of transmission / reception systems, whereas a normal mobile phone handles only one transmission / reception system. As a result, the user can select and use any transmission / reception system suitable for the region, purpose of use, and the like.

Furthermore, a receiving system in a new frequency band (1500 MHz band) such as GPS (Global Positioning System) for position detection is also added to the mobile phone.
Here, with reference to FIG. 9, the configuration of a cellular / GPS / PCS high frequency circuit capable of switching between three transmission / reception systems Cellular (800 MHz band) / GPS / PCS (Personal Communication Services; 1900 MHz band) will be briefly described. To do.

  In the Cellular / GPS / PCS high frequency circuit, the high frequency signals of three transmission / reception systems Cellular / GPS / PCS having different pass bands are demultiplexed by the composite demultiplexing circuit 10, and each of the transmission / reception systems in the Cellular transmission / reception system A SAW (Surface Acoustic Wave) duplexer 16 that switches between Tx and the reception system Rx is provided, and a SAW duplexer 18 that switches between the transmission system Tx and the reception system Rx in the PCS transmission / reception system is provided. Furthermore, a power amplifier constituting the Cellular transmission / reception system Tx, a low noise amplifier constituting the reception system Rx, a power amplifier constituting the PCS transmission / reception system Tx, a low noise amplifier constituting the reception system Rx, and a GPS reception system Rx are constructed. A low noise amplifier or the like (not shown) is provided.

One of the features of this circuit is that the SAW duplexers 16 and 18 are used, whereby the transmission and reception systems can be separated without using switching elements such as diodes.
The composite demultiplexing circuit 10 includes a low-pass LC filter circuit 5 for passing through a cellular transmission / reception system, a high-pass LC filter circuit 8 for passing through a PCS transmission / reception system, and a phase adjustment circuit 6 for GPS reception. And a SAW filter 7.

The SAW filter 7 is an element for allowing only a reception high-frequency signal of GPS frequency to pass, and has a sharp pass characteristic. The inductor element 9 connected in parallel to the antenna side of the high-pass LC filter circuit 8 is an element for phase adjustment.
JP 2003-8469 A Japanese Patent Laid-Open No. 11-225088

Characteristics 21 of transmission loss (insertion loss) of the low-pass LC filter circuit 5 from the antenna input terminal P in the cellular reception frequency band of the composite branching circuit 10 to the output terminal 1 of the low-pass LC filter circuit 5 Is shown in FIG.
FIG. 10B shows a transmission loss characteristic 22 of the SAW duplexer 16 from the output terminal 1 of the low-pass LC filter circuit 5 to the low-noise amplifier input terminal 11 constituting the cellular reception system.

FIG. 10 (c) shows a case where the low-pass LC filter circuit 5 and the SAW duplexer 16 are connected in cascade from the antenna input terminal P of the composite branching circuit 10 to the low-noise amplifier input terminal 11 of the Cellular reception system. Transmission characteristics 23 are shown.
As shown in FIGS. 10A and 10B, the low-frequency notch 24 is not generated in the transmission waveforms 21 and 22 of the low-pass LC filter circuit 5 alone and the SAW duplexer 16 alone. According to (c), it can be seen that a low frequency notch 24 is generated in the transmission waveform 23 in the case of cascade connection. The generation of the low-frequency notch 24 is caused by the fact that the antenna side terminal of the SAW duplexer connected in cascade with the composite branching circuit is electrically connected to the ground GND.

In order to suppress the low-frequency notch 24 of the reception system output generated by connecting the SAW duplexer 16 in the subsequent stage of the composite branching circuit 10 in this way, the low-pass LC filter circuit 5, the SAW duplexer 16, In the meantime, it is necessary to insert the capacitor 15 in series, which causes problems such as deterioration of transmission loss and increase in the number of constituent elements.
SUMMARY OF THE INVENTION An object of the present invention is to provide a composite demultiplexing circuit capable of demultiplexing a plurality of frequency bands by connecting a plurality of demultiplexing circuits in parallel, without deteriorating transmission loss and constituting elements. An object of the present invention is to provide a composite demultiplexing circuit that can suppress an increase in the number.

  Another object of the present invention is to provide a small and highly reliable chip component, a high frequency module and a wireless communication device which do not generate a low frequency notch, using the composite type demultiplexing circuit.

  The composite demultiplexing circuit according to the present invention demultiplexes a plurality of frequency bands by including a plurality of demultiplexing circuits, and transmits and receives at least one demultiplexing circuit and a high-frequency signal in the frequency band. A SAW duplexer that separates transmission and reception signals is connected in cascade with a circuit, and an element that passes a DC component between a line connecting a branch point connected to an antenna terminal and a composite branching circuit, and a ground. Is not connected.

  According to this configuration, a composite demultiplexing circuit is configured by making a circuit in which a direct current component cannot pass between the line connecting the branch point connected to the antenna terminal and the complex demultiplexing circuit and the ground. Therefore, it is possible to suppress a low-frequency notch in the output of the reception system, which is generated due to the cascade connection of the SAW duplexer downstream of the at least one branching circuit. Therefore, it is not necessary to insert a capacitor between the branching circuit and the SAW duplexer, and accordingly, the number of constituent elements is not increased, and the generation of harmonic distortion due to deterioration of transmission loss is also eliminated.

The element that passes the DC component is, for example, an inductor element. In the present invention, since this inductor element is not used, it is possible to suppress the low frequency notch of the reception system output without inserting a capacitor between the branching circuit and the SAW duplexer.
As an example of the composite type demultiplexing circuit of the present invention, there can be cited one composed of three demultiplexing circuits for demultiplexing the first frequency band, the second frequency band, and the third frequency band.

In this case, the circuit for extracting the electric signal in the first frequency band is constituted by at least one low-pass filter, and the circuit for extracting the electric signal in the third frequency band is constituted by at least one high-pass filter. .
The demultiplexing circuit of the second frequency band may be a circuit composed of a phase adjustment circuit and a surface acoustic wave filter. The reason is that a band pass filter is suitable for the branching circuit of the second frequency band, and the steep attenuation characteristic of the surface acoustic wave filter can be used. Specifically, a circuit configured in the order of a series capacitor, a parallel capacitor, a series inductor, and a parallel capacitor from the input side can be employed as the phase adjustment circuit.

  This composite demultiplexer circuit has the sum of the real part of the admittance normalized by the characteristic admittance of the total demultiplexer circuit as seen from the branch point connected to the antenna terminal in each frequency band, and the sum of the imaginary part. It is desirable that the relationship of 0 is established. If this relationship is satisfied, it is possible to provide a composite demultiplexing circuit that can handle a plurality of frequency bands and has no transmission loss in any frequency band.

The SAW filter may be either a Balance output type or an Unbalance output type, but if the Balance output type is used, the IC connected to the subsequent stage is a balanced input type (the balanced input is more advantageous for noise). Can adapt.
In addition, the chip component of the present invention is configured by mounting each component circuit of the composite demultiplexing circuit on a dielectric multilayer substrate. This makes it possible to obtain a compact and low-profile composite branching circuit.

In addition, according to the present invention, the composite multilayer circuit is provided on the surface and / or inside of the dielectric multilayer substrate, and any or all of the duplexer and the power amplifier are mounted, so that the transmission characteristics can be reduced. An excellent high-frequency module can be configured.
In addition, by providing the high frequency module, it is possible to provide a wireless communication device applicable to a plurality of frequency bands.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a composite demultiplexing circuit according to the present invention, and FIG. 2 is a circuit diagram of the composite demultiplexing circuit.
This composite type demultiplexing circuit is a triple-band compatible, and the three communication systems are Cellular communication system (first frequency band; 800 MHz), GPS communication system (second frequency band; 1500 MHz), PCS communication. System (third frequency band; 1900 MHz).

The composite demultiplexing circuit includes an ANT terminal connected to an antenna, a first terminal 1 for inputting / outputting a transmission / reception high-frequency signal in a first frequency band, and a second terminal for inputting a reception high-frequency signal in a second frequency band. 2. It has a third terminal 3 for inputting / outputting transmission / reception high frequency signals in the third frequency band.
A low pass filter circuit (hereinafter referred to as “LPF”) 5 is connected between the ANT terminal and the first terminal 1.

Further, the first terminal 1 is connected to a SAW duplexer 16 that switches between the transmission system Tx and the reception system Rx in the Cellular transmission / reception system, and the third terminal 3 is connected to the transmission system Tx in the PCS transmission / reception system, respectively. A SAW duplexer 18 for switching to the reception system Rx is connected.
As shown in FIG. 2, the LPF 5 is an LC filter in which a strip line 5L and a capacitor 5C are formed in each layer in the multilayer substrate. The LPF 5 is designed to attenuate the frequency band of the GPS communication system and the PCS communication system. The frequency band of the cellular communication system includes harmonics such as second harmonics and third harmonics, and these harmonics can also be attenuated.

  Further, between the ANT terminal and the second terminal 2, a phase adjustment circuit 6 including an inductor 6L and capacitors 6C1, 6C2, and 6C3 and a SAW filter 7 are included. The phase adjusting circuit 6 is composed of a series capacitor 6C1, a parallel capacitor 6C2 connected to the ground, a series inductor 6L, and a parallel capacitor 6C3 in this order from the ANT terminal, which are composed of strip lines and capacitors formed in a multilayer substrate. Alternatively, an inductor or a capacitor chip part may be used.

The structures of the SAW filter 7, SAW duplexer 16, and SAW duplexer 18 are not limited, but preferably 36 ° Y cut-X propagation LiTaO ₃ crystal, 64 ° Y cut-X propagation LiNbO ₃ crystal, 45 ° X cut A comb-shaped IDT (Inter Digital Transducer) electrode is formed on a substrate made of a -Z-propagating LiB ₄ O ₇ crystal or the like.

The SAW filter 7 may be a SAW filter that outputs a Balance high-frequency signal with respect to an input of an Unbalance high-frequency signal, and is a SAW filter that outputs an Unbalance high-frequency signal with respect to an input of an Unbalance high-frequency signal. May be.
The phase adjustment circuit 6 is a circuit necessary for increasing the respective impedances in the first frequency band and the third frequency band between the ANT terminal and the second terminal 2, and the SAW filter 7 alone is used. Each low impedance in the first frequency band and the third frequency band can be increased by rotating the phase while maintaining the impedance matching state of the second frequency band.

The first frequency band (800 MHz band), the second frequency band (1500 MHz band), and the third frequency when the cellular transmission / reception system is viewed from the branch point P that performs the third branching of the composite branching circuit. Admittance in the band (1900MHz band)
Y1a = G1a + jB1a,
Y2a = G2a + jB2a,
Y3a = G3a + jB3a
The positional relationship is shown in the admittance chart of FIG.

Furthermore, when the GPS reception system is viewed from the branch point P, the admittance in the first frequency band (800 MHz band), the second frequency band (1500 MHz band), and the third frequency band (1900 MHz band),
Y1b = G1b + jB1b,
Y2b = G2b + jB2b,
Y3b = G3b + jB3b
And the positional relationship is illustrated in the admittance chart of FIG.

Furthermore, when the PCS transmission / reception system is viewed from the branch point P, the admittance in the first frequency band (800 MHz band), the second frequency band (1500 MHz band), and the third frequency band (1900 MHz band),
Y1c = G1c + jB1c,
Y2c = G2c + jB2c,
Y3c = G3c + jB3c
And the positional relationship is illustrated in the admittance chart of FIG.

If the matching condition is designed so as to satisfy the following expression (3) in the above-described composite branching circuit, a composite branching circuit with good matching can be obtained. n is a number indicating a frequency band, and it is necessary to hold for all of n = 1, 2, and 3.
Gna + Gnb + Gnc = 1
Bna + Bnb + Bnc = 0 (n = 1, 2, 3) (3)
However, the value “1” is a value obtained by standardizing the characteristic admittance Y0 (Y0 is set to, for example, 0.02S).

As the SAW filter 7 used between the ANT terminal and the second terminal 2, it is desirable to use a SAW filter that outputs a Balance high-frequency signal with respect to an input of an Unbalance high-frequency signal. Since the Balance output has a characteristic that is strong against high-frequency noise, information data can be well extracted from the high-frequency signal output from the SAW filter.
The phase adjustment circuit 6 and the SAW filter 7 can attenuate the frequency band of the cellular communication system and the PCS communication system.

A high-pass filter (hereinafter referred to as “HPF”) 8 is configured between the ANT terminal P and the third terminal 3. The HPF 8 can also be constituted by strip lines and capacitors formed in the multilayer substrate.
This HPF 8 is designed to attenuate the frequency band of the cellular communication system and the GPS communication system. Further, harmonics such as second harmonics and third harmonics in the frequency band of the PCS communication system are included, and these harmonics can also be attenuated.

The HPF 8 is not formed with the parallel inductor 9 for phase adjustment as shown in FIG. 9 between the HPF 8 and the ground. Therefore, in the transmission loss characteristic of the synthesis circuit of the LPF 5 and the SAW duplexer 16, the low frequency notch 24 as shown in FIG. 9 does not occur, so that the reception characteristic of the cellular reception system is improved.
FIG. 6 shows an example of the circuit configuration of a composite demultiplexing circuit in which the function of suppressing harmonic components is further enhanced while maintaining the demultiplexing function of the composite demultiplexing circuit described so far.

The composite demultiplexing circuit of FIG. 6 further adds LPF 11 to LPF 5 of the circuit for extracting the high frequency signal of the first frequency band of the composite demultiplexing circuit of FIG. 2 to extract the high frequency signal of the third frequency band. A band elimination filter (hereinafter referred to as “BEF”) 12 is added to the HPF 8 of the circuit.
By adding LPF11 and BEF12 in this way, the second harmonic and the third harmonic in the first frequency band are suppressed, and the second harmonic and the third harmonic in the third frequency band are suppressed. Can be achieved.

FIG. 7 shows an external perspective view of the composite demultiplexing chip component 30 of the present invention having the above circuit configuration.
As shown in FIG. 7, the composite demultiplexing chip component 30 includes a dielectric multilayer substrate 31, a SAW filter 7 mounted on the substrate, an LPF 5 inside the substrate, a phase adjustment circuit 6, and an HPF 8. The The LPF 5, the phase adjustment circuit 6, and the HPF 8 are configured by LC chip components 33, strip lines, inductors, and capacitors formed in a dielectric multilayer substrate 31 configured by stacking a plurality of dielectric layers.

Each dielectric layer is formed by, for example, forming a conductor pattern with a conductor such as a copper foil on an organic dielectric multilayer substrate such as glass epoxy resin, and laminating and thermosetting, or a ceramic material. Various conductor patterns are formed on the inorganic dielectric layer, and these are laminated and fired at the same time.
In particular, if a ceramic material is used, the dielectric constant of the ceramic dielectric is usually 9 to 25, which is higher than that of the resin substrate. The distance between the elements can be reduced and the distance between the elements can be reduced.

In particular, it is desirable to use a ceramic material that can be fired at a low temperature, such as glass ceramics, because the conductor pattern can be formed of a low-resistance material such as copper or silver.
In addition, via hole conductors necessary for vertically connecting circuits are formed in each dielectric layer in a vertical direction across a plurality of layers. The via-hole conductor is formed by plating a through hole formed in the dielectric layer or filling a conductor paste.

As shown in FIG. 7, an electrode 34 for connecting the conductor pattern to the outside is provided on the end face or the back face of the dielectric multilayer substrate 31 formed as described above. In this way, the composite demultiplexing chip component 30 including the composite demultiplexing circuit is completed.
FIG. 8 is an external perspective view of the composite high-frequency module 40 incorporating the composite branching circuit of the present invention.

  On the multilayer circuit board 35, passive and active elements such as the SAW filter 7 and the LC chip component 33, the SAW duplexers 16 and 18, the power amplifier 42, and the SAW bandpass filter 43 forming a composite branching circuit are mounted. ing. Part or all of the inductors and capacitors constituting the matching circuit between the components are integrated and formed in the multilayer circuit board 35.

In FIG. 8, a plurality of terminal electrodes 44 are formed on the back surface of the multilayer circuit board 35. This terminal electrode 44 includes those having the function of the input / output terminals of the composite branching circuit and the composite high frequency module.
Such a high-frequency module 40 can be used in a wireless communication apparatus such as a multiband mobile wireless terminal.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments. For example, Cellular, PCS, and GPS have been cited as communication systems for each transmission / reception system. However, these are examples of communication systems and frequency bands, and the present invention includes GSM, GPS, DCS (Digital Cellular System), Cellular. , PCS, W-CDMA, etc., any frequency band can be applied.

It is a block diagram which shows the composite type | mold demultiplexing circuit of this invention. It is a circuit diagram of the composite type branching circuit. FIG. 5 is an admittance chart diagram showing admittance when a cellular transmission / reception system of a composite branching circuit is viewed from a branch point P. FIG. 4 is an admittance chart diagram showing admittance when a GPS receiving system of a composite branching circuit is viewed from a branch point P. FIG. 5 is an admittance chart diagram showing admittance when a PCS transmission / reception system of a composite branching circuit is viewed from a branch point P. This is an equivalent circuit of a composite demultiplexing circuit in which the function of suppressing harmonic components is further enhanced while maintaining the demultiplexing function of the composite demultiplexing circuit. 1 is an external perspective view of a composite demultiplexing chip component including a composite demultiplexing circuit according to the present invention. 1 is an external perspective view of a composite high frequency module incorporating a composite branching circuit of the present invention. It is a block diagram which shows the conventional composite type | mold demultiplexing circuit of a 3 band corresponding | compatible type. (A) is a graph which shows the transmission loss (insertion loss) of the low-pass LC filter circuit 5 of the composite type | mold demultiplexing circuit of FIG. (B) is a graph showing the transmission loss of the SAW duplexer 16. (C) is a graph showing transmission characteristics when the low-pass LC filter circuit 5 and the SAW duplexer 16 are connected in cascade.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission / reception terminal in 1st frequency band (Cellular) 2 Reception terminal in 2nd frequency band (GPS) Transmission / reception terminal in 3rd frequency band (PCS) 5 Low pass filter 6 Phase adjustment circuit 7 SAW filter 8 High pass filter 9 Parallel Inductor 11 Cellular Reception Terminal 12 Cellular Transmission Terminal 13 PCS Reception Terminal 14 PCS Transmission Terminal 15 Coupling Capacitor 16 SAW Duplexer 18 SAW Duplexer 30 Composite Demultiplexing Chip Component 40 High Frequency Module

Claims (11)

In a composite demultiplexing circuit that demultiplexes a plurality of frequency bands by providing a plurality of demultiplexing circuits,
A SAW duplexer that separates transmission / reception signals is cascade-connected between at least one branching circuit and a transmission / reception circuit that transmits / receives a high-frequency signal in the frequency band.
An element for passing a direct current component is not connected between a branch point connected to an antenna terminal of the compound branching circuit and the ground.   2. The composite branching circuit according to claim 1, wherein the element that allows the direct current component to pass is an inductor element. The plurality of frequency bands are a first frequency band, a second frequency band higher than the first frequency band, and a third frequency band higher than the second frequency band;
3. The branching circuit comprising: a branching circuit that extracts a first frequency band; a branching circuit that extracts a second frequency band; and a branching circuit that extracts a third frequency band. The composite type branching circuit as described.   The circuit for extracting the electric signal of the first frequency band is constituted by at least one low-pass filter, and the circuit for extracting the electric signal of the third frequency band is constituted by at least one high-pass filter. The composite type branching circuit as described.   The circuit for extracting the signal of the second frequency band is composed of a phase adjusting circuit (Matching Network) including an inductor and a capacitor, and a surface acoustic wave filter connected in series to the phase adjusting circuit. Item 5. The composite branching circuit according to Item 3 or Claim 4.   In each frequency band, the relationship where the sum of the real part of the admittance normalized by the characteristic admittance is 1 and the sum of the imaginary part is 0, as seen from the branch point connected to the antenna terminal, is established. 6. The composite branching circuit according to claim 1, wherein the composite branching circuit is provided. The admittances in the first frequency band, the second frequency band, and the third frequency band of the branching circuit of the first frequency band are Y1a = G1a + jB1a,
Y2a = G2a + jB2a,
Y3a = G3a + jB3a
And the admittance in the first frequency band, the second frequency band, and the third frequency band of the branching circuit in the second frequency band is represented by Y1b = G1b + jB1b,
Y2b = G2b + jB2b,
Y3b = G3b + jB3b
And the admittances in the first frequency band, the second frequency band, and the third frequency band of the branching circuit in the third frequency band are Y1c = G1c + jB1c,
Y2c = G2c + jB2c,
Y3c = G3c + jB3c
The composite type demultiplexing circuit according to claim 6, wherein the demultiplexing circuit is designed to satisfy the following formula (j is an imaginary unit, and n is a number indicating a frequency band).
Gna + Gnb + Gnc = 1
Bna + Bnb + Bnc = 0 (n = 1, 2, 3)   8. The composite branching circuit according to claim 1, wherein the SAW filter is a Balance output type or an Unbalance output type.   9. A chip component in which each demultiplexing circuit included in the composite demultiplexing circuit according to claim 1 is mounted on a dielectric multilayer substrate.   A high frequency wave comprising the composite branching circuit according to any one of claims 1 to 9 on the surface and / or inside of a dielectric multilayer substrate, and mounting any or all of a duplexer and a power amplifier. module.   A wireless communication device comprising the high-frequency module according to claim 10.

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