Multiplexer

Abstract

A multiplexer according to the present invention comprises: a first band pass filter connected to an antenna to pass a signal in a low frequency band; and a second band pass filter connected to the antenna to pass a signal in a high frequency band, wherein the first band pass filter is composed of a surface acoustic wave (SAW) resonator included in a bare chip, and the second band pass filter is composed of an inductor included in a package and a capacitor included in the bare chip.

Description

multiplexer

[0001] The present invention relates to a multiplexer, and more particularly, to a multiplexer including a plurality of filters connected to an antenna and passing signals of different frequency bands.

[0002] Currently, mobile communication terminals are trending toward multiband and multimode communication functions, and therefore, multiplexers are essential for RF front-end modules.

[0003] A multiplexer typically includes a plurality of filters connected to an antenna to pass signals of different frequency bands, and these filters may be lowpass filters, bandpass filters, or highpass filters.

[0004] However, existing multiplexers have a problem of parasitic coupling occurring because they implement high-frequency filters using capacitor elements and inductor elements within the package and implement low-frequency filters using IDTs within the chip, which causes the capacitors and inductors within the package to be close together.

[0005] The technical problem to be achieved by the present invention is to provide a multiplexer that can increase space utilization within a multiplexer package and reduce mutual parasitic coupling.

[0006] According to one embodiment of the present invention for solving the above technical problem, a multiplexer includes a first bandpass filter connected to an antenna to pass a signal of a low frequency band; and a second bandpass filter connected to the antenna to pass a signal of a high frequency band, wherein the first bandpass filter is configured with a SAW (surface acoustic wave) resonator included in a bare chip, and the second bandpass filter is configured with an inductor included in a package and a capacitor included in the bare chip.

[0007] The above capacitor is characterized by including at least one of an IDT (Inter Digital Transducer) capacitor and a MIM (Metal-Insulator-Metal) capacitor.

[0008] The above IDT capacitor is characterized in that it is arranged so as to be rotated by 90 degrees with respect to the IDT constituting the SAW resonator.

[0009] The above IDT capacitor is characterized in that it is configured to have a thickness at least 1.5 times greater than the thickness of the IDT constituting the SAW resonator.

[0010] The above IDT capacitor is characterized in that it is configured with a line width that is at least 1.5 times greater than the line width of the IDT constituting the SAW resonator.

[0011] The line spacing of the above IDT capacitor is characterized by being formed to be 30% or less of the IDT capacitor line width.

[0012] The primary metal and secondary metal of the above MIM capacitor are characterized by being composed of the same material as the first bandpass filter configured within the bare chip.

[0013] According to the present invention described above, by implementing a capacitor inside a bare chip in a high-frequency bandpass filter, there is an effect of improving the Q factor and insertion loss.

[0014] Furthermore, by placing IDT capacitors or MIM capacitors within the bare chip instead of placing capacitors within the package to implement high-frequency bandpass filters, space utilization within the package can be improved. Furthermore, parasitic coupling of the LC component, which occurs due to the conventional co-location of capacitors and inductors within the package, can be reduced.

[0015] Figure 1 is a circuit diagram of a multiplexer according to one embodiment of the present invention.

[0016] FIG. 2 is a reference diagram of one embodiment of a first bandpass filter and a second bandpass filter implemented in a package and a bare chip.

[0017] Figure 3 is a planar enlarged view of the IDT capacitor of the second bandpass filter included in the bare chip.

[0018] FIG. 4 is a reference diagram for a first bandpass filter and a second bandpass filter of another embodiment implemented in a package and a bare chip.

[0019] Figure 5 is a planar enlarged view of the MIM capacitor of the second bandpass filter included in the bare chip.

[0020] Figure 6 is a graph for evaluating the performance of the first bandpass filter and the second bandpass filter according to the present invention.

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and the attached drawings, substantially identical components are represented by the same reference numerals, thereby omitting redundant descriptions. Furthermore, when describing the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention.

[0022] Figure 1 is a circuit diagram of a multiplexer (100) according to one embodiment of the present invention.

[0023] A multiplexer (100) according to one embodiment of the present invention includes a plurality of filters connected to an antenna and passing signals of different frequency bands. The multiplexer (100) has a structure in which it has a plurality of outputs when the antenna side is an input, and a structure in which it has a plurality of inputs when the antenna (100) side is an output.

[0024] Referring to FIG. 1, a multiplexer (100) according to the present embodiment includes a first bandpass filter (110: bandpass filter, BPF) and a second bandpass filter (120: bandpass filter, BPF) that are connected to an antenna and pass signals of different frequency bands.

[0025] However, the multiplexer (100) of the present invention is exemplary and may be composed of two filters connected in parallel (referred to as a diplexer or duplexer), four filters connected in parallel (referred to as a quadplexer), or five filters connected in parallel (referred to as a quintplexer) or more filters.

[0026] Additionally, the multiplexer (100) may include an impedance matching element. The impedance matching element may include an inductor and / or a capacitor depending on the impedance to be matched, and may transmit a signal of maximum power through impedance matching. The impedance matching element may be connected between the antenna and ground, or alternatively or additionally, may be connected between the antenna and each filter to match the impedance.

[0027] In an embodiment of the present invention, at least one of a plurality of filters uses an LC filter, and at least another of the plurality of filters uses a SAW filter. LC filters are suitable for implementing a wide pass band, but have limitations in improving the skirt characteristic. On the other hand, SAW filters have the advantage of having a good skirt characteristic, although it is difficult to implement a wide pass band compared to LC filters due to their characteristics. The skirt characteristic refers to how well the pass band and the stop band are distinguished, and a good skirt characteristic means that the slope of the transition band between the pass band and the stop band is steep.

[0028] Therefore, by using LC filters and SAW filters together while considering the required passband of each filter and the spacing between the passbands, the advantages of both LC filters and SAW filters can be utilized.

[0029] For example, an LC filter may be used for a frequency band with a relatively large pass bandwidth, and a SAW filter may be used for a frequency band with a relatively small pass bandwidth. Furthermore, when the gap between two adjacent pass bands is large, an LC filter may be used, and when the gap between two adjacent pass bands is narrow, one or both of them may be used as a SAW filter.

[0030] In Fig. 1, the first bandpass filter (110) may be a 2.4 GHz band filter, and the second bandpass filter (120) may be a 5 GHz band filter.

[0031] The first bandpass filter (110) is connected to the antenna and passes signals in a low frequency band (e.g., 2.4 GHz band), and the second bandpass filter (120) is connected to the antenna and passes signals in a high frequency band (e.g., 5 GHz band).

[0032] Since the 2.4 GHz band has a relatively small pass bandwidth and a narrow gap between them, the first bandpass filter (110) can use a SAW filter, and since the 5 GHz band has a large pass bandwidth, the second bandpass filter (120) can use an LC filter.

[0033] Referring to Figure 1, the area indicated by the blue block corresponds to the bare chip, and the area indicated by the red block corresponds to the package.

[0034] The first bandpass filter (110) is composed of a surface acoustic wave (SAW) resonator included within a bare chip. In addition, the second bandpass filter (120) is composed of an inductor included within a package and a capacitor included within the bare chip.

[0035] The capacitor included in the bare chip to configure the second bandpass filter (120) may be at least one of an IDT (Inter Digital Transducer) capacitor or a MIM (Metal-Insulator-Metal) capacitor.

[0036]

[0037] FIG. 2 is a reference diagram of one embodiment of a first bandpass filter (110) and a second bandpass filter (120) implemented in a package and a bare chip.

[0038] In Fig. 1, the first bandpass filter (110) is implemented as a SAW resonator within a bare chip corresponding to a blue block. Also, referring to Fig. 2, the first bandpass filter (110) can be implemented as a SAW resonator within a bare chip.

[0039] Meanwhile, in Fig. 1, in order to configure the second bandpass filter (120), an inductor (120-1) is implemented within a package corresponding to a red block, and a capacitor (120-2) is implemented within a bare chip corresponding to a blue block.

[0040] Referring to FIG. 2, an inductor (120-1) constituting a second bandpass filter (120) is included within the package, and the bare chip not only includes a SAW resonator corresponding to the first bandpass filter (110) described above, but also includes a capacitor (120-2) constituting the second bandpass filter (120). The inductor (120-1) is embedded within the package and connected to ground (GND).

[0041] The capacitor (120-2) included in the bare chip to implement the second bandpass filter (120) may be an IDT capacitor. This IDT capacitor may be positioned rotated by 90 degrees with respect to the IDT of the SAW resonator (110) constituting the first bandpass filter (110).

[0042] The IDT capacitor constituting the second bandpass filter (120) may be configured to have a thickness at least 1.5 times greater than the IDT thickness of the SAW resonator constituting the first bandpass filter (110).

[0043] Since the thickness of the IDT capacitor constituting the second bandpass filter (120) is implemented in a structure that is at least 1.5 times thicker than the IDT thickness of the SAW resonator constituting the first bandpass filter (110), the Q factor can be improved and the capacity of the IDT capacitor can be increased.

[0044] In addition, the IDT capacitor constituting the second bandpass filter (120) may have a line width that is at least 1.5 times greater than the IDT line width of the SAW resonator constituting the first bandpass filter (110), and the line spacing of the IDT capacitor may be formed to be 30[%] or less of the IDT capacitor line width.

[0045] Figure 3 is a planar enlarged view of the IDT capacitor of the second bandpass filter (120) included in the bare chip.

[0046] Referring to FIG. 3, the line width and line spacing for the IDT capacitors constituting the second bandpass filter (120) are illustrated. As illustrated in FIG. 3, the line width of the IDT capacitors constituting the second bandpass filter (120) is at least 1.5 times greater than the line width of the IDT of the SAW resonator constituting the first bandpass filter (110), and the line spacing of the IDT capacitors is formed to be 30[%] or less of the line width of the IDT capacitor, thereby improving the Q factor and increasing the capacity of the IDT capacitor.

[0047]

[0048] FIG. 4 is a reference diagram for another embodiment of a first bandpass filter (110') and a second bandpass filter (120') implemented in a package and a bare chip.

[0049] Referring to FIG. 4, the first bandpass filter (110') can be implemented as a SAW resonator within a bare chip.

[0050] Meanwhile, to configure the second bandpass filter (120'), an inductor (120'-1) is implemented within the package, and a capacitor (120'-2) is implemented within the bare chip.

[0051] Referring to FIG. 4, an inductor (120'-1) constituting a second bandpass filter (120') is included in the package, and a SAW resonator corresponding to a first bandpass filter (110') is included in the bare chip, as well as a capacitor (120'-2) constituting a second bandpass filter (120').

[0052] The capacitor (120'-2) included in the bare chip to implement the second bandpass filter (120') may be a MIM (Metal-Insulator-Metal) capacitor.

[0053] Figure 5 is a planar enlarged view of the MIM capacitor of the second bandpass filter (120') included in the bare chip.

[0054] The MIM capacitor illustrated in Fig. 5 includes a structure in which an insulator is formed between a primary metal and a secondary metal on a wafer substrate.

[0055] MIM capacitors can be configured in groups of at least two to prevent misalignment between the primary and secondary metals during the fabrication process. If misalignment occurs, one C value decreases and the other increases, thus complementing each other.

[0056] The primary metal of the MIM capacitor is made of the same material as the first bandpass filter (110') configured within the bare chip, and the secondary metal of the MIM capacitor is also made of the same material as the first bandpass filter (110') configured within the bare chip.

[0057]

[0058] Figure 6 is a graph for evaluating the performance of the first bandpass filter (110) and the second bandpass filter (120) according to the present invention.

[0059] Referring to Fig. 6, in the case of the first bandpass filter (110), there is almost no difference in performance from the existing bandpass filter.

[0060] However, by implementing the capacitor inside the bare chip in the second bandpass filter (120) of the present invention, it can be confirmed that the Q factor is improved and the insertion loss is improved.

[0061] That is, by implementing the capacitor within the bare chip instead of inside the package and arranging the inductor within the package, the inductor and capacitor are prevented from being adjacent, thereby preventing parasitic coupling of the LC component within the package. Consequently, the Q factor can be improved, thereby reducing insertion loss.

[0062] The present invention has been described above, focusing on preferred embodiments thereof. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than limiting. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

[0063] The present invention can be used in the field of manufacturing multiplexers.

Claims

1. A first bandpass filter connected to the antenna to pass signals of a low frequency band; and A second bandpass filter is connected to the antenna and passes signals of a high frequency band, The above first bandpass filter is composed of a SAW (surface acoustic wave) resonator included in a bare chip, A multiplexer characterized in that the second bandpass filter is composed of an inductor included in the package and a capacitor included in the bare chip.

2. In claim 1, the capacitor, A multiplexer characterized by including at least one of an IDT (Inter Digital Transducer) capacitor and a MIM (Metal-Insulator-Metal) capacitor.

3. In claim 2, the IDT capacitor, A multiplexer characterized in that the IDT constituting the above SAW resonator is arranged rotated by 90 degrees.

4. In claim 2, the IDT capacitor, A multiplexer characterized in that it is configured with a thickness at least 1.5 times greater than the thickness of the IDT constituting the above SAW resonator.

5. In claim 2, the IDT capacitor, A multiplexer characterized in that it is configured with a line width at least 1.5 times greater than the line width of the IDT constituting the above SAW resonator.

6. In claim 2, A multiplexer characterized in that the line spacing of the IDT capacitor is formed to be 30% or less of the line width of the IDT capacitor.

7. In claim 2, A multiplexer characterized in that the primary metal and secondary metal of the above MIM capacitor are composed of the same material as the first bandpass filter configured within the above bare chip.

Images