KR20090030154A - Front end module - Google Patents

Abstract

A front end module is provided to embed an inductor and a capacitor in the front end module, thereby simplifying a manufacturing process of a mobile communication terminal. A selecting unit(12) selects a route between a transceiving end and an antenna. A filter unit(13) passes a frequency signal of a predetermined band among receiving frequency signals selected in the selecting unit. An impedance matching unit(14) is connected to the filter unit. And, the impedance matching unit controls impedance matching between an LNA(Low Noise Amplifier) and the filter unit. The selecting unit, filter unit and matching unit are formed in different areas on a dielectric substrate(11).

Description

Front End Module {FRONT END MODULE}

The present invention relates to a front end module, and more particularly to a front end module for improving the impedance matching between the filter and the external circuit is formed by the impedance matching portion at the end of the frequency reception filter.

With the recent development of mobile communication systems, mobile communication devices such as mobile phones and portable information terminals are rapidly spreading, and a system for transmitting and receiving signals of different frequency bands in various fields is also provided. have.

Therefore, from the demand for miniaturization and high performance of these devices, miniaturization and high performance of components used in them are required, and efforts for miniaturization and cost reduction of portable electronic devices are inevitably studied for integration of passive elements constituting them. Is going on. Increasingly, the demand for passive device integration technology for miniaturizing electronic devices and improving the performance and reliability of these passive devices is increasing day by day. Integration technology using ceramic substrates has been actively studied.

A front end module (FEM) used in a mobile communication terminal transmits a received signal received from an antenna to a circuit inside the terminal and transmits a transmitted signal transmitted from the terminal through the antenna. Since there is a difference in impedance between the front end module and a circuit inside the mobile communication terminal, it is necessary to match the impedance between the two components in order to connect the two RF components.

In order to solve the above problems, an object of the present invention is to provide a structure in which an impedance matching portion is formed in a front end module.

The present invention includes a selection unit for selecting a path between an antenna and a transmitting and receiving end, a filter unit for passing a frequency signal of a predetermined band among the reception frequency signals selected by the selection unit, and a filter unit connected to the filter unit and an external unit. A front end module including an impedance matching unit for adjusting impedance matching between a low noise amplifier (LNA), which is a circuit, and a dielectric substrate having the selection unit, the filter unit, and the matching unit formed in different areas, respectively. Can be.

The selector may be a switching diode.

The filter unit may include at least one band pass filter configured to pass only a frequency signal of a predetermined band among respective frequency signals selected by the selector.

The filter unit may include four band pass filters, wherein the four band pass filters are band pass filters for passing signals in the GSM850 MHz, GSM 900 MHz, GSM 1800 MHz, and GSM 1900 MHz bands, respectively. Can be.

The at least one band pass filter may be a surface acoustic wave (SAW) filter.

The impedance matching unit may include at least one impedance matching circuit respectively connected to the at least one band pass filter.

The impedance matching circuit may include an inductor and a capacitor.

The impedance matching circuit includes an inductor for providing a connection end, one end of which is connected to the band pass filter and the other end of which is connected to the low noise amplifier, and a capacitor, one end of which is connected to one end of the inductor and the other end of which is connected to ground. It may include.

The inductor may be a spiral conductive pattern formed on the substrate, and the capacitor may be a conductive layer formed to face each other with a dielectric layer of the substrate interposed therebetween.

Each of the at least one impedance matching circuit may provide an impedance of about 50 ohms between the at least one filter and a low noise amplifier (LNA), which is an external circuit connected to each of the at least one filter.

The dielectric substrate may be a low temperature co-fired ceramic (LTCC) substrate.

According to the present invention, the RF terminal structure of the mobile communication terminal can be further simplified, and the inductor and the capacitor can be embedded in the front end module, thereby simplifying the manufacturing process of the mobile communication terminal, reducing manufacturing cost, and miniaturization.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a configuration diagram of a front end module according to an embodiment of the present invention.

Referring to FIG. 1, the front end module 10 according to the present embodiment may include a substrate 11, a selection unit 12, a filter unit 13, and an impedance matching unit 14.

The substrate 11 may be a low temperature co-fired ceramic (LTCC) substrate. The low temperature cofired ceramic substrate 11 may be formed by stacking a plurality of dielectric layers, and a circuit pattern and a passive element may be formed between the stacked dielectric layers.

The selector 12 may select a path between the antenna and the transceiver.

The selector 12 may include a diplexer (not shown) and a plurality of transmit / receive switches (not shown). The diplexer may serve to separate a frequency band signal transmitted and received by the antenna. That is, the low frequency band signal and the high frequency band signal received by the antenna may be separated, or the low frequency band signal and the high frequency band signal transmitted by the antenna may be separated. The low frequency band signal may include GSM850 MHz and GSM900 MHz, and the high frequency band signal may include GSM1800 MHz and GSM1900 MHz signals.

A transmission / reception switch may be used to send a frequency band signal separated by the diplexer to a receiving end Rx, or to send a signal of a transmitting end Tx to the diplexer. That is, the transmission / reception switch may determine the transmission mode or the reception mode of the front end module.

In the present embodiment, the selector 12 performs the functions of the diplexer and the transmit / receive switch, and the a, b, c, and d terminals transmit the received frequency signal received through the antenna to the filter unit 13. A terminal for transmitting, and e, f terminal may be a terminal for transmitting a transmission signal to the antenna. The selector may be a switching diode. remind The selector serving as a switching role may be implemented in various ways.

In the front end module of the present embodiment, when the switch of the selector is connected to the e or f terminal, the front end module can operate in the transmission mode, and the switch of the selector is connected to one of the a, b, c, and d terminals. Once connected, the front end module can operate in receive mode.

The selector 12 may select one of the a, b, c, and d terminals to select signals of different frequency bands in a reception (Rx) mode. That is, the selector 12 may serve as a diplexer for selecting the desired frequency and a transmission / reception switch for determining a transmission mode or a reception mode.

The filter unit 13 may serve to pass only signals of a predetermined frequency band from the received frequency signal selected by the selector 12.

In the present embodiment, the filter unit 13 may include four filters 13-1, 13-2, 13-3, and 13-4, and the four filters are GSM850 MHz, GSM900 MHz, and GSM1800, respectively. And a band pass filter for passing signals in the MHz and GSM1900 MHz bands.

The plurality of band pass filters 13-1, 13-2, 13-3, and 13-4 may pass only a frequency band signal of a predetermined range among the received signals, but may not pass a signal outside the range. Such a band pass filter can attenuate harmonics of the received signal.

The plurality of band pass filters 13-1, 13-2, 13-3, and 13-4 may be surface acoustic wave (SAW) filters. In general, the SAW filter may be widely used as a band pass filter in communication devices and other electronic devices. The SAW filter may include two inter digital transducers (IDTs) arranged at a predetermined distance on a piezoelectric substrate. The branched SAW filter and the SAW resonator filter constituting the resonator on the piezoelectric substrate can be used.

The impedance matching unit 14 may match an impedance between the filter unit 13 and the low noise amplifier 16, which is an external circuit having one end connected to the filter unit 13 and to which the front end module is connected.

In the present embodiment, the impedance matching unit 14 has four impedance matching circuits 14-1 and 14- connected to the respective SAW filters 13-1, 13-2, 13-3, and 13-4, respectively. 2, 14-3, 14-4).

When the front end module is connected to an external circuit, the impedance between the SAW filter and the low noise amplifier, which is an external circuit, is preferably about 50 ohms. The impedance matching circuit may implement an impedance of about 50 ohms.

2 illustrates an embodiment of the impedance matching circuit.

Referring to FIG. 2, the impedance matching circuit 24 may include an inductor 24-1 and a capacitor 24-2.

One end of the inductor 24-1 may be connected to the SAW filter 23, and the other end thereof may be connected to a low noise amplifier 26 that is an external circuit. One end of the capacitor 24-2 may be connected to one end of the inductor 24-1, and the other end thereof may be connected to a ground portion.

Various methods of implementing an impedance matching circuit on the substrate may be implemented. The impedance matching circuit may be implemented by mounting an inductor chip and a capacitor chip on a substrate. In this embodiment, the inductor 24-1 is formed by implementing a spiral-shaped conductor pattern or strip line on the upper surface of the LTCC substrate, and a conductive film having a predetermined area between the stacked dielectric layers of the LTCC substrate. By forming the capacitor 24-2.

In the present embodiment, the front end module including the impedance matching unit as described above can be provided.

As such, by forming an impedance matching unit for controlling impedance matching with an external circuit in the front end module, the structure of an RF terminal such as a mobile communication terminal using the front end module can be further simplified. That is, since a separate impedance matching unit does not need to be formed between the front end module and the external circuit, a more simplified structure can be provided.

In addition, the inductor and capacitor required for impedance matching are formed in the front end module, thereby reducing cost and miniaturization, and the manufacture of the mobile terminal does not require impedance matching between the front end module and external circuits such as a low noise amplifier. The process can be simplified.

1 is a structural diagram of a front end module according to an embodiment of the present invention.

Fig. 2 is a circuit diagram showing an example of an impedance matching circuit in the front end module according to the embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

11 dielectric substrate 12 selection

13 filter unit 14 impedance matching unit

Claims (12)

A selector for selecting a path between the antenna and the transceiver; A filter unit which passes a frequency signal of a predetermined band among the reception frequency signals selected by the selection unit; An impedance matching unit connected to the filter unit to adjust impedance matching between the filter unit and a low noise amplifier (LNA) which is an external circuit; And A dielectric substrate having the selection part, the filter part, and the matching part respectively formed in different regions Front end module comprising a. The method of claim 1, The selection unit, A front end module, characterized in that the switching diode. The method of claim 1, The filter unit, And at least one band pass filter for passing only a frequency signal of a predetermined band among the respective reception frequency signals selected by the selection unit. The method of claim 3, The filter unit, A front end module comprising four band pass filters. The method of claim 4, wherein The four band pass filters, And a band pass filter for passing signals in the GSM850MHz, GSM900MHz, GSM1800MHz, and GSM1900MHz bands, respectively. The method of claim 3, The at least one band pass filter, A front end module characterized in that it is a Surface Acoustic Wave (SAW) filter. The method of claim 3, The impedance matching unit, And at least one impedance matching circuit each connected to the at least one band pass filter. The method of claim 7, wherein The impedance matching circuit, A front end module comprising an inductor and a capacitor. The method of claim 8, The impedance matching circuit, An inductor having one end connected to the band pass filter and the other end providing a connection end that may be connected to the low noise amplifier; And A capacitor whose one end is connected to one end of the inductor and the other end is connected to ground Front end module comprising a. The method of claim 8, The inductor is a spiral conductive pattern formed on the substrate, And the capacitor is a conductive film formed to face each other with a dielectric layer of the substrate interposed therebetween. The method of claim 7, wherein Each of the at least one impedance matching circuit, And a impedance of about 50 ohms between a low noise amplifier (LNA) which is an external circuit connected to each of said at least one filter and said at least one filter. The method of claim 1, The dielectric substrate, A front end module characterized in that it is a Low Temperature Co-fired Ceramic (LTCC) substrate.

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