KR101922574B1 - Multiplexer - Google Patents

Abstract

The multiplexer according to the present invention includes a plurality of filters connected to an antenna to pass signals of different frequency bands, at least one of the plurality of filters is an LC filter, and at least one of the plurality of filters is a SAW filter .

Description

Multiplexer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplexer, and more particularly, to a multiplexer connected to an antenna and including a plurality of filters for passing signals of different frequency bands.

Currently, mobile communication terminals are equipped with multiband and multimode communication functions, and accordingly a multiplexer is necessarily provided in the RF front end module.

The multiplexer typically includes a plurality of filters coupled to the antenna and passing signals of different frequency bands, the plurality of filters being selected from the group consisting of a lowpass filter, a bandpass filter, highpass filter).

However, the conventional multiplexer is composed only of an LC filter implemented by an inductor and a capacitor, or a SAW filter using a surface acoustic wave (SAW) device.

The LC filter uses an LC resonant circuit composed of an inductor and a capacitor, whereas the SAW filter uses a surface acoustic wave on a piezoelectric body. The operation principle of the LC filter is very different from that of the LC resonant circuit.

However, since the conventional multiplexer is composed of only LC filter or SAW filter alone, it has a limitation that it can not take advantage of the advantages of LC filter and SAW filter.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a multiplexer capable of effectively utilizing the advantages of both the LC filter and the SAW filter.

According to an aspect of the present invention, there is provided a multiplexer including a plurality of filters connected to an antenna and passing signals of different frequency bands, at least one of the plurality of filters is an LC filter, At least one of them is a SAW filter.

The multiplexer may further include a matching device connected between the antenna and the ground to match the impedance.

The multiplexer may further include at least one matching element connected between the antenna and at least one of the plurality of filters to match the impedance.

Wherein the plurality of filters comprises: a first filter having a GPS frequency band; A second filter having a first Wi-Fi frequency band; And a third filter having a second Wi-Fi frequency band higher than the first Wi-Fi frequency band, wherein the first filter or the second filter is a SAW filter, and the third filter is an LC filter.

At least one of the plurality of filters may be a filter formed by combining an LC filter and a SAW filter.

The filter formed by combining the LC filter and the SAW filter may be a filter formed by connecting an LC filter and a SAW notch filter in series.

Wherein the filter formed by connecting an LC filter and a SAW notch filter in series is connected in parallel with another filter having a pass band adjacent to the pass band of the LC filter and a cutoff band of the SAW notch filter is connected in parallel to the other And may include the lower cutoff frequency of the filter.

Or a filter formed by serially connecting an LC filter and a SAW notch filter, and another filter having a pass band adjacent to the pass band of the LC filter are connected in parallel, and a cutoff band of the SAW notch filter is connected to the other And may include an upper cutoff frequency of the filter.

The filter formed by combining the LC filter and the SAW filter may be a filter formed by connecting an LC filter and a SAW band-pass filter in parallel.

Wherein the filter formed by connecting an LC filter and a SAW band pass filter in parallel and another filter having a pass band adjacent to the LC filter are connected in parallel and the upper cutoff frequency of the SAW band pass filter And the lower cutoff frequency of the SAW bandpass filter may be larger than the upper cutoff frequency of the LC filter.

Or a filter formed by connecting an LC filter and a SAW band pass filter in parallel and another filter having a pass band adjacent to the LC filter and a lower pass band adjacent to the LC filter are connected in parallel, Is less than the required lower cutoff frequency of the filter and the upper cutoff frequency of the SAW bandpass filter may be less than the lower cutoff frequency of the LC filter.

In addition, the above-described filter constructed by combining an LC filter and a SAW filter includes a first filter formed by serially connecting an LC filter and a SAW notch filter; And a second filter formed by connecting an LC filter and a SAW band-pass filter in parallel.

Wherein the second filter is connected in parallel with the first filter and the passband of the first filter and the neighboring higher passband, and the cut-off band of the SAW notch filter is a required sub- Wherein the lower cutoff frequency of the SAW bandpass filter is less than a required lower cutoff frequency of the second filter and the upper cutoff frequency of the SAW bandpass filter is lower than the lower cutoff frequency of the second filter, May be less than the cut-off frequency.

According to the present invention, by implementing the multiplexer using the LC filter and the SAW filter together, it is possible to provide a multiplexer having both advantages of the LC filter and the SAW filter.

1 shows a configuration of a multiplexer according to an embodiment of the present invention.
Fig. 2 shows a configuration in which a matching element connected between an antenna and each filter is added to the multiplexer of Fig.
Figure 3 shows an example of the required frequency response of each filter of Figure 1;
4 shows a configuration of a multiplexer in which some passbands are implemented by combining an LC filter and a SAW filter according to an embodiment of the present invention.
Figure 5 shows the frequency response of each filter of Figure 4;
6 shows a configuration of a multiplexer in which a pass band is implemented by combining an LC filter and a SAW filter according to another embodiment of the present invention.
Figure 7 shows the frequency response of each filter in Figure 6;
8 shows a configuration of a multiplexer in which some passbands are implemented by combining an LC filter and a SAW filter according to another embodiment of the present invention.
Figure 9 shows the frequency response of each filter of Figure 8;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and the accompanying drawings, substantially the same components are denoted by the same reference numerals, and redundant description will be omitted. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 shows a configuration of a multiplexer according to an embodiment of the present invention.

Referring to FIG. 1, the multiplexer according to the present embodiment includes a plurality of filters 210, 220, 230 connected to an antenna 100 to pass signals of different frequency bands, And a matching element 300 connected between ground and matching the impedance. The multiplexer has a plurality of outputs when the antenna 100 is an input, and a plurality of inputs when the antenna 100 is an output.

Although the multiplexer in this embodiment is made up of three first filters 210, a second filter 220 and a third filter 230 connected in parallel (referred to as a triplexer) It can be composed of two filters (called diplexers), four filters in parallel (called a quadplexer), and five filters in parallel (quintuple) Quot; quintplexer ") or more.

Each of the filters 210, 220 and 230 has different passbands and may be a lowpass filter (LPF), a bandpass filter (BPF), or a highpass filter (HPF). For example, if the frequency of the passband is larger in the order of the first filter 210, the second filter 220 and the third filter 230, then the first filter 210 may be an LPF or a BPF, BPF, and the third filter 230 may be HPF or BPF.

The matching element 300 may include an inductor and / or a capacitor according to a matching impedance, and may transmit a signal of maximum power through impedance matching.

The matching element 300 may be coupled between the antenna 100 and ground as shown in Figure 1 and alternatively or additionally the matching elements 310,320 and 330 may be coupled to the antenna & 100 and the filters 210, 220, 230 to match the impedances.

In an embodiment of the present invention, at least one of the plurality of filters 210, 220, 230 uses an LC filter, and at least one of the plurality of filters 210, 220, 230 uses a SAW filter. The LC filter is suitable for realizing a wide pass band, but has limitations in improving the skirt characteristic. On the other hand, the SAW filter is difficult to realize a wide pass band as compared with the LC filter due to its characteristics, but has a merit of good skirt characteristics. The skirt characteristic means how well the pass band and the stop band are distinguished. The good skirt characteristic means that the slope of the transition band between the pass band and the stop band is steep .

Therefore, when the LC filter and the SAW filter are used together in consideration of the required pass bandwidth of each filter and the interval between passbands, the advantages of both the LC filter and the SAW filter can be utilized.

For example, an SAW filter can be used for a frequency band in which an LC filter is used for a relatively large frequency band and a frequency band for which a passband is relatively small. If the gap between two adjacent passbands is large, an LC filter is used. If the gap between two adjacent passbands is narrow, one or both of the SAW filters can be used.

For example, if the first filter 210 is a GPS band filter, the second filter 220 is a 2.4 GHz Wi-Fi band filter, and the third filter 230 is a 5 GHz Wi-Fi band filter, the GPS band and the 2.4 GHz Wi- The SAW filter is used for the first filter 210 and the second filter 220. Since the 5 GHz WiFi band is relatively far away from the 2.4 GHz WiFi band and the passband width is large, (230) may be an LC filter.

Further, in addition to the LC filter and the SAW filter, a bulk acoustic wave (BAW), a film bulk acoustic resonator (FBAR), or the like can be further used.

In addition, in the case of the LC filter, the inductor and the capacitor constituting the LC filter are embedded in a package such as LTCC (Low Temperature Co-fired Ceramics) or PCB, or the package or the inductor and the commercial capacitor are used as all or a part of the inductor and capacitor It can be mounted using SMT (Surface Mounter Technology).

The matching device 300 may also be implemented in an embedded pattern in a package such as HTCC (High Temperature Co-Fired Ceramic), LTCC, or PCB, or may be implemented using SMT in a package using a commercial inductor or a commercial capacitor as all or a part of the inductor and capacitor As shown in FIG.

For example, when the first filter 210 of the GPS band and the second filter 220 of the 2.4 GHz Wi-Fi band use a SAW filter and the third filter 230 of the 5 GHz Wi-Fi band uses an LC filter, The inductor and the capacitor constituting the filter 230 are embodied in a package such as LTCC or PCB and the first filter 210 and the second filter 220 which are the SAW filters are formed in a package common to the third filter 230 .

FIG. 3 shows an example of the required frequency response of the first filter 210, the second filter 220, and the third filter 230. Here, the frequency response is expressed as a frequency band (VS) insertion loss (IL). 3 shows an example in which the pass band of each filter is wide (for example, 150 MHz or more) and the interval between the pass band of the second filter 220 and the third filter 230 is narrow (for example, 150 MHz or less).

3, the passband of the first filter 210 is 600 MHz to 960 MHz, the passband width thereof is 360 MHz, the passband of the second filter 220 is 1400 to 2200 MHz, the passband width thereof is 800 MHz, 230 has a pass band of 2300 to 2700 MHz and a passband width of 400 MHz. Therefore, the pass bandwidths of the first filter 210, the second filter 220, and the third filter 230 are all 150 MHz or more, and the interval between the passbands of the second filter 220 and the third filter 230 is 100 MHz.

In this case, the second filter 220 and the third filter 230 are required to have a good skirt characteristic while providing a wide pass band. Particularly, the second filter 220 should have a good skirt characteristic at an upper cutoff frequency (2200 MHz) or higher and lower than a lower cutoff frequency (2300 MHz) in the case of the third filter 230). For example, in the case of the second filter 220, the insertion loss at the lower cutoff frequency (2300 MHz) of the third filter 230 is -35 dB or less, and in the case of the third filter 230, It is required that the insertion loss at an upper cutoff frequency (2200 MHz) of -35 dB or less.

However, it is very difficult to implement a filter that satisfies both the wide pass band and good skirt characteristics with an LC filter or a SAW filter. As described above, the LC filter has poor skirt characteristics, and it is difficult to realize a wide pass band with the SAW filter.

However, in the embodiment of the present invention, as described later, by implementing a given pass band in combination with the LC filter and the SAW filter, it is possible to satisfy a wide pass bandwidth and a good skirt characteristic at the same time.

FIG. 4 shows a configuration of a multiplexer in which some passbands are implemented by combining an LC filter and a SAW filter according to an embodiment of the present invention, and FIG. 5 shows a frequency response of each filter in FIG.

Referring to FIG. 4, a filter is constructed by connecting a first filter 210, a second filter 221 and a first SAW notch filter 222 in series, and a third filter 231 and a second filter 233, SAW notch filters 222 connected in series are connected in parallel.

Referring to FIGS. 4 and 5, the first filter 210 has an LC filter having a lower cutoff frequency and an upper cutoff frequency of 600 MHz and 960 MHz, respectively. The second filter 221 has a lower cutoff frequency and an upper cutoff frequency of 1400 MHz, 2200 MHz, and the third filter 231 is an LC filter having a lower cut-off frequency and an upper cut-off frequency of 2300 MHz and 2700 MHz, respectively.

The insertion loss of the first filter 210 at the lower cutoff frequency of 1400 MHz of the second filter 221 is -35 dB or less, The insertion loss in the second filter 221 at the upper cutoff frequency (960 MHz) of the first filter 210 is also less than -35 dB, which is not a particular problem.

However, since the interval between the pass band of the second filter 221 and the pass band of the neighboring third filter 231 is narrow, the second filter 231 at the lower cutoff frequency (2300 MHz) of the third filter 231, Since the insertion loss of the second filter 221 is -35 dB or more and the insertion loss of the third filter 231 at the upper cutoff frequency 2200 MHz of the second filter 221 is also -35 dB or more, There is a problem that signal interference occurs between the cutoff frequency (2200 MHz) and the lower cutoff frequency (2300 MHz) of the third filter 231.

In order to solve such a problem, a SAW notch filter having a narrow cut-off bandwidth and a good skirt characteristic can be connected in series to the second filter 221 and the third filter 231, respectively.

Specifically, a first SAW notch filter 222 including a lower cutoff frequency (2300 MHz) of the third filter 231 is connected in series to the second filter 221, and a third SAW notch filter 222, 231, a cutoff band connects a second SAW notch filter 222 including an upper cutoff frequency (2200 MHz) of the second filter 221.

A signal near the lower cutoff frequency (2,300 MHz) of the third filter 231 passing through the second filter 221 is attenuated by the first SAW notch filter 222, The signal near the upper cutoff frequency (2200 MHz) of the second filter 221 that has passed through the filter 231 is attenuated by the second SAW notch filter 222.

Therefore, the skirt characteristic by the combination of the second filter 221 and the first SAW notch filter 222 is good, and the insertion loss at the lower cutoff frequency (2,300 MHz) of the third filter 231 is -35 dB or less And the skirt characteristic by the combination of the third filter 231 and the second SAW notch filter 222 is also good so that the insertion loss at the upper cutoff frequency (2200 MHz) of the second filter 231 is -35 dB Or less.

FIG. 6 shows a configuration of a multiplexer in which some passbands are implemented by combining an LC filter and a SAW filter according to another embodiment of the present invention, and FIG. 7 shows a frequency response of each filter in FIG.

6, a filter formed by connecting a first filter 210, a second filter 223 and a first SAW band-pass filter 224 in parallel, and a filter formed by connecting a third filter 233 and a second SAW band Pass filters 234 are connected in parallel.

6 and 7, the first filter 210 has an LC filter having a lower cutoff frequency and an upper cutoff frequency of 600 MHz and 960 MHz, respectively. The second filter 223 has a lower cutoff frequency and an upper cutoff frequency of 1400 MHz and And the third filter 233 is an LC filter having a lower cut-off frequency and an upper cut-off frequency of 2500 MHz and 2700 MHz, respectively.

The lower frequency of the stop band of the second filter 223 is designed to be 2300 MHz and the upper frequency of the stop band of the third filter 233 is designed to be 2200 MHz in the present embodiment, The insertion loss of the third filter 233 is -35 dB or less at the frequency of 2200 MHz and the insertion loss of the second filter 223 is -35 dB or less at the lower cutoff frequency of 2300 MHz of the third filter 233 Respectively.

However, since the second filter 223 and the third filter 233 have poor bar skirt characteristics, which is an LC filter, the actual upper cutoff frequency of the second filter 223 is 1980 MHz, which is less than the required upper cutoff frequency 2200 MHz And the actual lower cutoff frequency of the third filter 233 is 2500 MHz, which exceeds the required lower cutoff frequency (2300 MHz).

In this case, in order to correct the actual upper cut-off frequency of the second filter 223 to the required upper cut-off frequency and to correct the actual lower cut-off frequency of the third filter 233 to the required lower cut-off frequency, It is possible to connect the SAW band-pass filter having good characteristics to the second filter 223 and the third filter 233 in parallel.

Concretely, the second filter 223 is supplied with a higher cutoff frequency (preferably equal to the upper cutoff frequency 2200 MHz) and a lower cutoff frequency than the actual upper cutoff frequency (1980 MHz) of the second filter 223 The third filter 233 is connected to the first SAW bandpass filter 224 in parallel and the upper cutoff frequency lower than the lower cutoff frequency 2300 MHz The second SAW band-pass filter 234, which is smaller than the actual lower cut-off frequency (2500 MHz) of the filter 233, is connected in parallel.

The upper cut-off frequency of the filter in which the second filter 223 and the first SAW band-pass filter 224 are connected in parallel becomes higher than the required upper cut-off frequency (2200 MHz), and the third filter 233 and the second SAW band The lower cut-off frequency of the filter to which the pass filter 234 is connected in parallel becomes less than or equal to the required lower cut-off frequency (2300 MHz).

Even if the third filter 233 is operated at the required upper cutoff frequency (2200 MHz) of the second filter 223 while the pass bandwidth of the second filter 223 and the third filter 233 is corrected in accordance with the required pass bandwidth, The insertion loss of the second filter 223 is still less than -35 dB at the lower cut-off frequency of 2300 MHz of the third filter 233.

FIG. 8 shows a configuration of a multiplexer in which some passbands are implemented by combining an LC filter and a SAW filter according to another embodiment of the present invention, and FIG. 9 shows a frequency response of each filter in FIG.

8 and 9, the first filter 210 has an LC filter having a lower cutoff frequency and an upper cutoff frequency of 600 MHz and 960 MHz, respectively, the second filter 221 has a lower cutoff frequency and an upper cutoff frequency of 1400 MHz, 2200 MHz, and the third filter 233 is an LC filter having a lower cut-off frequency and an upper cut-off frequency of 2500 MHz and 2700 MHz, respectively.

In this embodiment, the second filter 221 is designed to have the same passband as the required passband (1400 MHz to 2200 MHz), the third passband 233 requires a passband of 2200 MHz to 2700 MHz, In contrast, by designing at 2500 MHz to 2700 MHz, the insertion loss at the upper cutoff frequency (2200 MHz) of the second filter 221 is set to be? 35 dB or less.

Since the second filter 221 is an LC filter and the skirt characteristic is poor, the insertion loss at the lower cutoff frequency (2300 MHz) of the third filter 233 is? 35 dB or more. Since the third filter 233 is also an LC filter having a poor skirt characteristic, the insertion loss is designed to be? 35 dB or less at the upper cutoff frequency (2200 MHz) of the second filter 221, (2300 MHz), which is required as a low cutoff frequency.

In order to solve this problem, a SAW notch filter 222 having a narrow cut-off bandwidth and a good skirt characteristic is connected in series to the second filter 221, and the actual lower cut- The SAW bandpass filter 234 having a narrow pass bandwidth and a good skirt characteristic can be connected to the third filter 233 in parallel.

Specifically, the SAW notch filter 222 including the lower cutoff frequency (2300 MHz) at which the third filter 233 is required is connected in series to the second filter 221, and the SAW notch filter 222 connected in series to the third filter 233 The SAW bandpass filter 234 whose lower cutoff frequency is lower than or equal to the lower cutoff frequency (2300 MHz) required (preferably equal) and whose upper cutoff frequency is smaller than the actual lower cutoff frequency (2500 MHz) of the third filter 233, .

The signal near the required lower cutoff frequency (2300 MHz) of the third filter 231 that has passed through the second filter 221 is enhanced by attenuation by the SAW notch filter 222, The skirt characteristic by the combination of the filter 221 and the SAW notch filter 222 becomes good so that the insertion loss at the lower cutoff frequency of 2300 MHz of the third filter 231 becomes -35 dB or less.

The lower cut-off frequency of the filter in which the third filter 233 and the SAW band-pass filter 234 are connected in parallel is lower than the lower cut-off frequency (2300 MHz) required and the passband of the third filter 233 is required The insertion loss of the third filter 233 at the upper cutoff frequency (2200 MHz) of the second filter 221 can still be made to be? 35 dB or less, while being corrected to meet the pass bandwidth.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (13)

delete delete delete delete delete delete And a plurality of filters connected to the antenna for passing signals of different frequency bands,
Wherein at least one of the plurality of filters is an LC filter,
Wherein at least one of the plurality of filters is a filter formed by serially connecting an LC filter and a SAW notch filter,
The filter formed by connecting an LC filter and a SAW notch filter in series and another filter having a pass band adjacent to the LC filter and having a higher pass band adjacent thereto are connected in parallel,
Wherein the cut-off band of the SAW notch filter comprises a lower cut-off frequency of the other filter. And a plurality of filters connected to the antenna for passing signals of different frequency bands,
Wherein at least one of the plurality of filters is an LC filter,
Wherein at least one of the plurality of filters is a filter formed by serially connecting an LC filter and a SAW notch filter,
A filter formed by connecting an LC filter and a SAW notch filter in series, and another filter having a pass band adjacent to the LC filter and a lower pass band adjacent thereto,
And the cutoff band of the SAW notch filter includes an upper cutoff frequency of the other filter. delete And a plurality of filters connected to the antenna for passing signals of different frequency bands,
Wherein at least one of the plurality of filters is an LC filter,
At least one of the plurality of filters is a filter formed by connecting an LC filter and a SAW band-pass filter in parallel,
The filter comprising the LC filter and the SAW band-pass filter connected in parallel and the other filter having the pass band of the LC filter and the adjacent higher pass band are connected in parallel,
Wherein the upper cut-off frequency of the SAW band-pass filter is higher than a required upper cut-off frequency of the filter formed by connecting the LC filter and the SAW band-pass filter in parallel, and the lower cut-off frequency of the SAW band- Lt; RTI ID = 0.0 > frequency. ≪ / RTI > And a plurality of filters connected to the antenna for passing signals of different frequency bands,
Wherein at least one of the plurality of filters is an LC filter,
At least one of the plurality of filters is a filter formed by connecting an LC filter and a SAW band-pass filter in parallel,
The filter comprising the LC filter and the SAW band pass filter connected in parallel and the other filter having the pass band of the LC filter and the adjacent lower pass band are connected in parallel,
Wherein the lower cut-off frequency of the SAW band-pass filter is lower than a required lower cut-off frequency of the filter formed by connecting the LC filter and the SAW band-pass filter in parallel, and the upper cut-off frequency of the SAW band- Frequency. And a plurality of filters connected to the antenna for passing signals of different frequency bands,
Wherein at least one of the plurality of filters is an LC filter,
At least one of the plurality of filters is a first filter formed by serially connecting an LC filter and a SAW notch filter,
Wherein at least one of the plurality of filters is a second filter formed by connecting an LC filter and a SAW band pass filter in parallel. 13. The method of claim 12,
Wherein the first filter and the second filter having a pass band adjacent to the pass band of the first filter are connected in parallel,
Wherein the cutoff band of the SAW notch filter includes a required lower cutoff frequency of the second filter,
The lower cut-off frequency of the SAW band-pass filter is lower than a required lower cut-off frequency of the second filter, and the upper cut-off frequency of the SAW band-pass filter is smaller than the lower cut-off frequency of the LC filter constituting the second filter Multiplexer.

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