KR20070040516A - Saw duplexer - Google Patents

Abstract

The present invention provides a transmission filter arranged to transmit a signal transmitted from a transmitting end to an antenna end and comprising a plurality of resonators; A reception filter disposed to receive a signal transmitted through the antenna stage and configured of a plurality of resonators; A first capacitor connected in parallel between the transmission filter and the antenna terminal and implemented as a transmission line pattern; A second capacitor connected in parallel between the receiving filter and the antenna terminal and embodied in a transmission line pattern; And a inductor connected in series between the antenna terminal and the second capacitor.

Saw duplexer, miniaturized

Description

SAW duplexer

1 is a block diagram schematically showing the configuration of a duplexer using a conventional LTCC.

2a and 2b show a typical resonator;

3 is a schematic diagram of a saw duplexer according to the present invention;

4A is an exemplary view for explaining the configuration of a transmission filter according to the present invention.

Figure 4b is an exemplary view for explaining the configuration of the receiving filter according to the present invention.

5 is a view showing the structure of a capacitor according to the present invention.

* Explanation of symbols for main parts of drawings *

300: saw duplexer 310: transmission filter

311,321: first resonator 312,322: second resonator

313,323: third resonator 314,324: fourth resonator

315,325 fifth resonator 316,326 sixth resonator

320: reception filter 330: first capacitor

340: second capacitor 350: inductor

The present invention relates to a saw duplexer, and more particularly, to a small saw duplexer without a phase shifter.

Recently, RF components that are applied in addition to the multi-functionality, slimness and low cost of mobile communication terminals are also demanding for miniaturization.

In addition to miniaturization and high performance of communication equipment, a saw filter for transmitting or receiving a signal to receive or receive a signal having a certain frequency band when transmitting or receiving is often used. For RF filters, SAW (Surface Acoustic Wave) duplexers with good signal processing efficiency are widely used.

A conventional saw duplexer is composed of a transmission filter 104, a reception filter 108, and a phase shifter 110 using a low temperature co-fired ceramic (LTCC), as shown in FIG. The transmission filter 104 serves to transmit a signal transmitted from the transmitter to the antenna terminal, and the reception filter 108 serves to receive a signal transmitted through the antenna terminal.

The transmission filter 104 and the reception filter 108 may be of a ladder type in which a one-port resonator as shown in FIGS. 2A and 2B is connected in series and in parallel. As shown in FIGS. 2A and 2B, a typical one-port resonator is an input / output interdigital transducer (IDT) for filtering an external signal input to an input terminal, and is filtered through the input / output IDT. It consists of an output terminal for output.

In addition, the one-port resonator illustrated in FIGS. 2A and 2B has reflection parts formed on both sides of the input / output IDT to prevent the signal from being lost when the external signal is filtered in the input / output IDT. By constructing such a one-port resonator in series and in parallel, it is possible to construct an unbalanced surface acoustic wave filter of various ladder types.

Such a conventional duplexer is used as a filter for minimizing mutual interference so that a signal is transmitted and received simultaneously in a mobile communication terminal, and is composed of a transmission filter and a reception filter, and each filter is a LiTaO _3. An input converter configured to convert an electrical input signal into mechanical vibration on a piezoelectric body, and an output converter formed opposite to the input converter to convert mechanical vibration into an electrical signal and output the load to a load. In the output transducer, comb-shaped aluminum electrodes are formed to be spaced apart from each other by a predetermined distance.

In addition, the saw duplexer is manufactured in the form of an integrated package with circuit elements formed on a ceramic laminate substrate by a technique called low temperature co-fired ceramic (LTCC) having excellent high frequency performance.

Typical packages used for the packaging of saw filters are alumina ceramics and HTCC packages fabricated at high temperatures using W and Mo as electrode materials, which are often combined with duplexers or FEMs with built-in saw filters due to the reduced electrical conductivity of the electrode materials. In the case of devices, since passive devices for circuits cannot be implemented in the form of patterns in the package, integration and miniaturization are difficult.

Therefore, the use of the LTCC can use an electrode material having excellent electrical conductivity, and can achieve integration and miniaturization because it is a cofire process technology in which a metal and its ceramic substrate are simultaneously made at a low temperature.

In the case of the saw duplexer, the cost of parts is continuously lowered in accordance with the demand of lower price of the user. The duplexer must be completely isolated because the unwanted received signal is infinite impedance at the time of transmission. On the contrary, the duplexer must be completely isolated due to the infinite impedance when receiving the unwanted signal.

According to the conventional saw duplexer design technique, the filter meets the above condition because the impedance of the transmission filter is almost infinite in the reception band due to the design structure of the filter, but the impedance of the reception filter is formed so low that it is close to a short circuit in the transmission band. Therefore, it was difficult to completely isolate the design of the chip, and a phase shifter had to be separately installed on the antenna terminal side of the receiving filter.

The phase shifter 110 serves as a key element that enables bidirectional communication of the duplexer by moving the impedance of the reception filter in the transmission band to almost infinity. In order to configure the phase shifter 110 in a package in the form of a strip line, low temperature cofired ceramics (LTCC) having low loss at high frequencies are used.

In addition, the length of the phase shifter is one quarter of the period, which is considerably longer, limiting the size and thickness of the package, which is an obstacle to achieving miniaturization and low cost. For example, when the LTCC material with a dielectric constant of 7.8 is used, the length of the phase shifter is about 32 mm, and the area is increased to achieve the same plane, and if it is implemented in multiple layers, the size is reduced but the thickness is increased. The limit of miniaturization is reached.

On the other hand, inductors and capacitors can be used to implement phase shifters on printed circuit boards outside of the package, which increases the surface area of printed circuit boards as well as the increased cost resulting from the increased number of surface mount (SMT) devices. It can also be a factor.

An object of the present invention is to implement a small surface acoustic wave duplexer at a low cost.

The present invention for achieving the above object is a transmission filter disposed to transmit a signal transmitted from the transmitting end to the antenna end and composed of a plurality of resonators; A reception filter disposed to receive a signal transmitted through the antenna stage and configured of a plurality of resonators; A first capacitor connected in parallel between the transmission filter and the antenna terminal and implemented as a transmission line pattern; A second capacitor connected in parallel between the receiving filter and the antenna terminal and embodied in a transmission line pattern; And a inductor connected in series between the antenna terminal and the second capacitor.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. The saw duplexer according to the present invention proposes a form without a conventional phase shifter.

3 is a schematic configuration diagram of the saw duplexer according to the present invention. As shown in FIG. 3, the saw duplexer 300 according to the present invention may have a transmission filter 310, a reception filter 320, and a song. The first capacitor 330 connected to the credit filter 310, the second capacitor 340 connected to the receiving filter 320, and the inductor 350 connected to the capacitor 340.

The first capacitor 330 connected to the transmission filter 310 is disposed at the antenna terminal, and the second capacitor 340 and the inductor 350 connected to the reception filter 320 are also disposed at the antenna port. In this case, when the inductor 350 is configured in the package, the inductor 350 may be configured in a strip line form or may be configured in an external printed circuit board of the package. Preferably, the inductor 350 may be configured in an external printed circuit board for miniaturization of the saw duplexer.

As shown in FIG. 4A, the transmission filter 310 includes a first resonator 311 disposed in series at an antenna stage in order to have infinite impedance in a reception band.

The sixth resonator 316 is connected in series with the transmission input terminal, and the fifth resonator 315 is connected in parallel with the output of the sixth resonator 316. At this time, the fifth resonator 315 is grounded in a parallel connection.

The third resonator 313 and the fourth resonator 314 are connected in series with the output of the sixth resonator 316, and the second resonator 312 is connected in parallel with the output of the third resonator 313. At this time, the second resonator 312 is formed between the output of the third resonator 313 and the output of the fifth resonator 315.

The third resonator 313 is connected in series with the first resonator 311 and connected in series with the antenna terminal.

In this way, the transmission filter 310 is configured in the form of a ladder circuit, the first capacitor 330 connected in parallel with the output of the first resonator 311 is the output of the second resonator 312 and the fifth resonator 315 It is grounded in parallel with the output of.

The reception filter 320 will be described with reference to FIG. 4B.

As shown in FIG. 4B, a sixth resonator 326 disposed at an antenna stage is provided in the reception filter 320 in parallel with the capacitor 340 to provide the ladder circuit type of the capacitor 340.

The first resonator 321 is connected in series to the antenna stage, the second resonator 322 is connected in series with the output of the first resonator 321, and the third resonator 323 is the output of the second resonator 322. Is connected in series.

The fourth resonator 324 is grounded in parallel between the second resonator 322 and the third resonator 323, and the fifth resonator 325 is connected between the first resonator 321 and the second resonator 322. Grounded in parallel.

As described above, the sixth resonator 326 is connected in parallel with the second capacitor 340, and is also connected in parallel with the first resonator 321 and the fifth resonator 325, so that the capacitor 340 and the fifth resonator 325 are connected. It is connected to the ground terminal of ground.

As described above, the receiving filter 320 is connected to the second capacitor 340 in the form of a ladder circuit, and the inductor 350 according to the present invention is connected in series to the input side of the second capacitor 340 at the antenna terminal. .

Since the saw duplexer 300 according to the present invention as described above does not have a conventional phase shifter, the length can be reduced to 200 μm to 400 μm, thereby achieving miniaturization, and the capacitor 330 and the capacitor 340 according to the present invention. As shown in FIG. 5, the performance of the saw duplexer 300 may be adjusted by changing the overlap between the same electrodes and the overlap between the different electrodes by forming a transmission line pattern having the same line width n. .

Specifically, as shown in FIG. 5, the distance ℓ between the same electrodes having the same line width for each of the capacitor 330 and the capacitor 340 according to the present invention is implemented differently from the pattern interval of the resonator, so that Do not affect resonance. In addition, by adjusting the overlap (h) between the electrodes and the number of electrodes, it is possible to adjust the Q value of the saw duplexer 300 according to the present invention.

Although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiments are for the purpose of description and not of limitation.

In addition, those skilled in the art will understand that various implementations are possible within the scope of the technical idea of the present invention.

As described above, miniaturization is possible by using the saw duplexer of the present invention, and since the phase shifter can be implemented in a general low cost high temperature co-fired ceramic package without implementing the expensive LTCC, it is possible to reduce the cost.

In addition, when the saw duplexer of the present invention is used, phase matching is possible by using a small inductor having a large Q value, thereby reducing the loss of the duplexer.

Claims (8)

A transmission filter disposed to transmit a signal transmitted from the transmitting end to the antenna end and configured of a plurality of resonators; A reception filter disposed to receive a signal transmitted through the antenna stage and configured of a plurality of resonators; A first capacitor connected in parallel between the transmission filter and the antenna terminal and implemented as a transmission line pattern; A second capacitor connected in parallel between the receiving filter and the antenna terminal and embodied in a transmission line pattern; And And a duplexer in series between the antenna stage and the second capacitor. The method of claim 1, The transmission line pattern of the first capacitor and the transmission line pattern of the second capacitor is a saw duplexer, characterized in that implemented by two electrodes forming a corresponding uneven structure with a predetermined distance. The method of claim 2, And the transmission line pattern spacing distance of the first capacitor is different from the pattern spacing of the transmission line pattern of each resonator constituting the transmission filter. The method of claim 2, And the transmission line pattern spacing distance of the second capacitor is different from the pattern spacing of the transmission line pattern of each resonator constituting the receiving filter. The method of claim 2, The transmission line pattern separation distance of the first capacitor and the transmission line pattern separation distance of the second capacitor are different from the pattern interval of the transmission line pattern of each resonator constituting the transmission filter and the transmission filter. . The method of claim 1, And a plurality of resonators constituting the transmission filter are connected to the first capacitor in the form of a ladder circuit. The method of claim 1, And a plurality of resonators constituting the receiving filter are connected to the second capacitor in the form of a ladder circuit. The method of claim 2, And a Q value is adjusted by adjusting an overlapping area between the electrodes in the transmission line pattern of the first capacitor and the transmission line pattern of the second capacitor.

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