JP2001217601A - Module substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a module substrate which can improve passing loss characteristic of a reception frequency outputted from a reception terminal by reducing the transmission loss of strip lines of switch circuits connected to two filters respectively. SOLUTION: A low-pass filter LPF1 and a high-pass filter HPF1, and a switch which is connected to those low-pass filter LPF1 and high-pass filter HPF1 respectively, comprises at least diodes D1, D2, D3, D4, and strip lines SL1 and SL2, and splits transmission and reception signals are incorporated, and the strip lines SL1 and SL2 of the switch are constituted by using the low-pass filter LPF1 for the switch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a module board having a dual-band antenna switching circuit incorporated in a high-frequency circuit section of a mobile radio communication device such as a cellular phone and a car phone.

[0002]

2. Description of the Related Art In recent years, dualization of portable telephones (for example, transmission and reception of both 900 MHz band and 1800 MHz band) has been promoted.

[0003] With the dualization of the mobile phone, two reception filters and two transmission filters are simply required. In the future, with the advance of triple and multi-system,
The number of filters tends to increase. Then, from the viewpoint of miniaturization, it is required that one filter be shared for transmission and reception and incorporated in one substrate.

On the other hand, since one transmission / reception filter requires a switch circuit for separating transmission / reception signals, when two or more filters described above are mounted on a substrate, the transmission / reception corresponding to each filter is required. A switch circuit for separating the signal for use is required.

[0005] Therefore, for example, a module substrate incorporating a circuit as shown in FIG. 6 has been proposed. FIG.
FIG. 3 is an equivalent circuit diagram of a dual band compatible antenna switching circuit.

In FIG. 6, between an antenna terminal A and a transmission terminal T1, a high-pass filter HPF1, a coupling capacitor C1, and a high-frequency switching diode D1 which form a diplexer circuit and pass a transmission / reception frequency in the 1800 MHz band are connected in series. (Serial), and between the coupling capacitor C1 and the high-frequency switching diode D1, and the receiving terminal R
1, the receiving circuit side looks high impedance (infinity) from the antenna terminal A during transmission, and
A strip line SL1 having an electrical length of １ ／ of the wavelength λ1 with respect to the transmission frequency is provided so that impedance matching with the high-pass filter HPF1 can be achieved.

The receiving terminal R1 and the strip line S
A high-frequency switching diode D2 for switching between transmission and reception and preventing a high-frequency signal for transmission from entering the receiving circuit is inserted between L1 and one end thereof, and one end thereof is grounded. The high-frequency switching diode D2 operates in conjunction with the high-frequency switching diode D1.

Similarly, between the antenna terminal A and the transmission terminal T2, a low-pass filter LPF1, which constitutes a diplexer circuit for passing a transmission / reception frequency of, for example, a 900 MHz band and cutting a second harmonic and a third harmonic of the transmission frequency, is provided. The coupling capacitor C2 and the high-frequency switching diode D3 are connected in series. Further, between the coupling capacitor C2 and the high-frequency switching diode D3 and between the receiving terminal R2, 1 / of the wavelength λ2 with respect to the transmission frequency. Strip line S having an electrical length of 4
L2 is provided, and a high-frequency switching diode D is provided between the reception terminal R2 and the strip line SL2.
4 is inserted and one end thereof is grounded.

High frequency switching diodes D1, D
2. A switch circuit for the high-pass filter HPF1 is configured by the strip line SL1, and the high-frequency switching diodes D3 and D4 and the strip line SL
2 constitutes a switch circuit for the low-pass filter LPF1.

[0010]

In the above switch circuit, for example, 900M
The received signal in the Hz band is output from a 900 MHz band receiving terminal R2 via a low-pass filter LPF1 that allows the 900 MHz band to pass, and further via a strip line SL2 having an electrical length of 波長 of the wavelength λ2 with respect to the transmission frequency. At this time, the high-frequency switching diodes D1, D2, D3, and D4 of the switch circuit need to be turned off.

Even if a module substrate in which the two switch circuits shown in the above equivalent circuit are built in a ceramic substrate using a material having a relative dielectric constant of about 8 is manufactured, the width of the strip line may be about 145 μm. , Can be formed stably, has high characteristic impedance, and has a strip line SL
1. The transmission loss of SL2 is as low as about 0.2 dB, and does not affect the received signals output from the receiving terminals R1 and R2.

However, the 2 shown in the above equivalent circuit
In order to configure a small module in which two switch circuits are built in a ceramic substrate using a material having a high relative permittivity, particularly a material having a relative permittivity of 15 or more in order to reduce the size of the module, Set the thickness of the ceramic substrate to 0.
When the thickness is reduced to about 7 to 1 mm, the width of the strip line cannot be stably formed to a line width of 75 μm or less because of the process, so that the characteristic impedance is reduced to about 40Ω. The transmission loss of the line SL2 and the strip line SL1 of the switch circuit for the 1800 MHz band is 0.6 to 0.6.
There is a problem in that the received signals output from the receiving terminals R1 and R2 are deteriorated to about 0.8 dB.

Accordingly, the present invention has been made in view of the above circumstances, and has as its object to provide a dual-band high-frequency antenna switching circuit, for example, at 900 MHz.
Improve the transmission characteristics of the strip line constituting the switch circuit for the z band and the switch circuit for the 1800 MHz band,
The object is to improve the transmission loss with respect to the reception frequency output from the reception terminals R1 and R2.

[0014]

A module board according to the present invention comprises a low-pass filter and a high-pass filter, and a switch connected to the low-pass filter and the high-pass filter, respectively, for separating a transmission / reception signal comprising at least a diode and a strip line. The switch is built-in, and the strip line of the switch is configured using at least a low-pass filter for a switch.

By adopting such a configuration, for example, when the switch is provided with at least a strip line and a diode on the receiving side and at least a diode on the transmitting side, the characteristic impedance of the switch circuit is formed. By adding a switch low-pass filter circuit to a part of the low strip line,
Since the impedance in the reception frequency band can be made close to 50Ω, deterioration of the passing loss due to impedance mismatch can be prevented.

The module substrate of the present invention functions effectively especially when the substrate is made of a material having a large relative dielectric constant for the purpose of miniaturization, particularly a material having a relative dielectric constant of 15 or more.

It is preferable that the strip line of the switch is constituted by using a low-pass filter for the switch and a strip line for adjusting the electric length connected to the low-pass filter for the switch. As described above, by connecting the electrical length adjusting strip line to the switch low-pass filter and controlling the length of the electrical length adjusting strip line, the electrical length of the switch strip line is adjusted, and the switch strip line is adjusted. Can be controlled to have a length of 1/4 of the wavelength.

As described above, the electric length of the strip line of the switch with respect to the transmission frequency is set to １ ／ of the wavelength.
, The strip line operates as a switch circuit at the time of transmission, and at the same time, has a function as a transmission line with a small passage loss at the time of reception, thereby reducing the passage loss at the time of transmission and reception. be able to.

Further, the strip line of the switch is
It is desirable to use a switch low-pass filter and an input / output capacitor connected to the switch low-pass filter. By connecting the input / output capacitors to the switch low-pass filter in this way, the filter circuit can be downsized, and the GND capacitance of the switch low-pass filter can be reduced, so that the loss can be reduced. .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A module board for a dual band antenna according to the present invention will be described below. FIG.
FIG. 3 is an equivalent circuit diagram of a dual-band antenna module substrate incorporating the antenna switching circuit of the present invention.

In FIG. 1, reference symbol A denotes an antenna terminal, T1
Is a transmitting terminal of the pass frequency f1 (for example, 1800 MHz band), R1 is a receiving terminal of the pass frequency f2 (1800 MHz band), and T2 is a pass frequency f3 (for example, 900 MHz band).
R2 is a pass frequency f4 (900 MHz band)
HPF1 is a high-pass filter that passes frequencies f1 and f2, and LPF1 is a low-pass filter that passes frequencies f3 and f4 and cuts harmonics twice, three times, and four times the passing frequency f3. In addition, a diplexer circuit is formed by the low-pass filter LPF1 and the high-pass filter HPF1.

Symbols C1 and C2 denote coupling capacitors for cutting DC, D1 and D2 denote transmission frequencies f1,
This is a high-frequency switching diode for switching transmission and reception of the reception frequency f2, and one end of D2 is grounded. The strip line SL1, together with the high-frequency switching diodes D1 and D2, constitutes a transmission / reception switching circuit for frequencies f1 and f2, that is, a switch.

D3 and D4 are high-frequency switching diodes for switching between transmission and reception at the transmission frequency f3 and the reception frequency f4, and one end of D4 is grounded. The strip line SL2 includes high-frequency switching diodes D3 and D3.
4, a transmission / reception switching circuit for frequencies f3 and f4,
That is, a switch is configured.

The strip line SL1 has a transmission frequency f
1 has an electrical length of の of the wavelength λ1, and the strip line SL2 has an electrical length of １ ／ of the wavelength λ2 of the transmission frequency f3.
Electrical length.

In the module board of the present invention, as shown in FIGS. 1 and 2, a part of the strip lines SL1 and SL2 constituting the transmission / reception switching circuit (switch) is replaced with a low-pass filter (circuit) LPFS1 for switching.
It is composed of LPFS2. These switching low-pass filters LPFS1 and LPFS2 are provided to reduce the passage loss of the strip lines SL1 and SL2.

That is, the low-pass filter LPF for the switch
S1 and LPFS2 are a strip line SLA and a pair of GND capacitors C between the strip line SLA and the ground electrode.
gnd, and strip line SL1,
SL2 is a low-pass filter for switch LPFS1, LFS
PFS2 and low-pass filter LPFS for this switch
1. A strip line SLB for electrical length adjustment connected to LPFS2, and an input / output capacitor Cio for connecting the input and output of the low-pass filter for switching (LPFS1, LPFS2) with a capacity between the strip lines SLA.

In the module substrate configured as described above, a part of the switch strip lines SL1 and SL2 is connected to the switch low-pass filters LPFS1 and LPFS.
By adding 2, it is possible to make the impedance in the reception frequency band close to 50Ω, and it is possible to prevent deterioration of the passing loss due to impedance mismatch.

In particular, the switch stripline SL
1, SL2 is connected to a strip line SLA and a GND capacitor C.
Low-pass filter LPFS for switch composed of gnd
1, the LPFS2 and the input / output capacitance Cio, the strip line SLA, the input / output capacitance Cio, the GN
By optimizing the D capacitance Cgnd, the impedance within the reception signal band of the strip lines SL1 and SL2 can be made close to 50Ω, so that the reflection loss can be reduced, and as a result, the transmission loss of the strip lines SL1 and SL2 can be further improved. .

A low-pass filter LPF for a switch
S1, LPFS2, electrical length adjustment strip line S
LB is connected, LPFS LPFS for switch
1. Strip lines SL1 and SL including LPFS2
2 is set to 1/1/3 of the transmission frequencies f1 and f3.
Strip line SLB for electric length adjustment so as to have four wavelengths
By adjusting the length, the transmission loss at the time of reception can be further improved without impairing the function as a transmission / reception switch circuit.

The layer structure of the switch portion of the module substrate of the present invention will be described with reference to FIG. In the module substrate of the present invention, the ground electrode GND1 is formed in the base 30 and the ground electrode GND is formed on the bottom of the base 30.
2 are formed, and these ground electrodes GND1,
A switch circuit is formed between GND2.

That is, the ceramic between the ground electrodes GND1 and GND2 is made of a material having a relative permittivity of 15 or more in order to reduce the size of the module, and the thickness thereof is reduced in order to reduce the thickness. Have been.
It is desirable that the ceramic above the ground electrode GND1 be made of a material having a lower relative dielectric constant than the ceramic between the ground electrodes GND1 and GND2.

A low-pass filter for switching LPFS1 (LPF1) is provided in a part between the ground electrodes GND1 and GND2.
S2), input / output capacitance Cio, and strip line SLB
Is formed, and a low-pass filter LPF for a switch is formed.
The S1 (LPFS2) and the input / output capacitance Cio connect via a via-hole conductor 35 a spiral-structured strip line 31 and a spiral-structured strip line 33 formed by sandwiching ceramics so as to face the strip line 31. It is formed by this.

A low-pass filter LPF for a switch
S1 (LPFS2) is connected to an electrode 38 formed on the surface of the base 30 by a via-hole conductor 37 passing through an opening formed in the ground electrode GND1, and one end of the strip line SLB is formed in the ground electrode GND1. Via hole conductor 39 passing through the opening
It is connected to an electrode 40 formed on the surface of the base 30.

The input / output capacitance Cio in FIG. 1 and FIG.
Is formed by the stray capacitance formed at the portion where
The ND capacitance Cgnd is formed by effectively using the parasitic capacitance generated between the strip line 33 and the ground electrode GND1 and between the strip line 31 and the ground electrode GND2. The strip lines 31 and 33 are formed so as not to overlap, and the input / output capacitances Cio and GN
A low-pass filter LPFS1, LPFS2 for a switch may be configured by separately providing a capacitor electrode for forming the D capacitor Cgnd.

The operation of the circuit built in the module substrate of the present invention will be described. When transmitting the frequency f3, the high-frequency switching diodes D3 and D4 are turned on, and the high-frequency switching diodes D1 and D2 are turned off. Then, since the strip line SL2 forming the switch has a length of の of the wavelength λ2 of the transmission frequency f3, the strip line SL2 functions as a 波長 wavelength resonator in which one end of the strip line SL2 is grounded. For,
The impedance on the receiving terminal R2 side at the pass frequency f3 viewed from the antenna terminal A becomes high impedance (infinity), and the transmission signal is transmitted from the transmission terminal T2 to the transmission frequency f
Almost propagate to the antenna terminal A via the low-pass filter LPF1 that passes through the antenna terminal A.

At this time, the low-pass filter LPF1
It has a function of cutting harmonics twice, three times and four times the transmission frequency f3. At the transmission frequency f1, no signal is output to the antenna terminal A because the high-frequency switching diode D1 is off.

The same applies to the case of transmitting the transmission frequency f1.

When performing reception, the high-frequency switching diodes D1, D2, D3 and D4 are turned off, so that the strip lines SL1 and SL2 function as transmission lines.
The respective received signals propagate to 1, R2. As described above, the transmission of the high-frequency signal is performed alternately during transmission and reception, and has a switching function.

[0039]

EXAMPLE A dual-band antenna module substrate shown in FIG. 1 was manufactured as follows. Pass frequency f1 is 17
47.5 MHz, f2 is 1842.5 MHz, f3 is 8
With 97.5 MHz and f4 set to 942.5 MHz, strip lines SL1 and SL2 were designed in accordance with the length of 1/4 of the wavelength of frequencies f1 and f3.

The pass frequency of the low-pass filter LPF1 is 880-960 MHz, and the high-pass filter H
Assuming that the pass frequency of the PF1 is 1710 to 1885 MHz, the dimensions of the module substrate are 5.4 mm long × 7 mm wide ×
It was produced as a size having a thickness of 0.8 mm.

Then, a low-pass filter LPFS1 (LPFS2) for a switch, which constitutes a part of the strip line SL1 (or SL2), is formed inside the substrate in a multilayer spiral structure shown in FIG. Here, the relative dielectric constant of the ceramic between the ground electrodes GND1 and GND2 is set to 1
8.7.

The input / output capacitance Cio shown in FIG. 2 is a stray capacitance formed at the overlapping portion of the strip lines 31 and 33, and the GND capacitance Ggnd is generated between the strip lines 31 and 33 and the GND electrodes GND1 and GND2. It is formed by effectively using the parasitic capacitance.

FIG. 4 shows the transmission characteristics of the strip line SL2 formed using the switching low-pass filter LPFS2.

As a comparative example, FIG. 5 shows the transmission characteristics of the strip line SL2 as shown in FIG. 6 without using the switch low-pass filter.

As for the transmission characteristics of the strip line SL2, comparing FIG. 4 and FIG. 5, the pass loss at the frequency f4 (900 MHz) is about -0.7 dB in the comparative example, whereas the transmission loss of the present invention is -0.7 dB. 0.3 dB or less, indicating that the passage loss is small.

[0046]

According to the present invention, in a dual-band antenna module substrate having a low-pass filter, a high-pass filter, and at least two switches each including a diode and a strip line, the frequencies f3, f4
By using a low-pass filter for a switch to configure a part of a strip line constituting a switch (for example, a 900 MHz band) for a switch, the transmission characteristics of the strip line can be improved, so that the pass characteristics with respect to the reception frequency can be improved.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram of a dual-band antenna module substrate according to the present invention.

FIG. 2 is an equivalent circuit diagram of a strip line configured using a low-pass filter for a switch.

FIG. 3 is a perspective view showing a pattern structure of a strip line formed using a low-pass filter for a switch.

FIG. 4 illustrates a case where the module substrate of the present invention is used.
It is a figure which shows the transmission characteristic of the strip line of 0 MHz band.

FIG. 5 is a diagram showing transmission characteristics of a strip line when a conventional dual-band antenna switching circuit is used.

FIG. 6 is an equivalent circuit diagram of a conventional dual-band antenna switching circuit.

[Explanation of symbols]

HPF1: high-pass filter LPF1: low-pass filter D1, D2, D3, D4: high-frequency switching diode SL1, SL2: strip line LPFS1, LPFS2: low-pass filter for switch Cio: input / output capacity SLB: Strip line for electric length adjustment

Claims (5)

[Claims] 1. A low-pass filter and a high-pass filter, and a switch connected to the low-pass filter and the high-pass filter, respectively, for separating a transmission / reception signal composed of at least a diode and a strip line.
A module substrate comprising at least a low-pass filter for a switch. 2. The module according to claim 1, wherein the switch strip line is configured using a switch low-pass filter and an electrical length adjusting strip line connected to the switch low-pass filter. substrate. 3. The module according to claim 1, wherein a strip line of the switch is constituted by using a low-pass filter for the switch and an input / output capacitor connected to the low-pass filter for the switch. substrate. 4. The module substrate according to claim 1, wherein the switch is provided with at least a strip line and a diode on a receiving side and at least a diode on a transmitting side. 5. The module substrate according to claim 1, wherein the electrical length of the switch strip line with respect to the transmission frequency has a length of 波長 of the wavelength.