Communications circuit for reducing crosstalk

This application claims the priority of Korean Patent Application No. 10-2010-0078779 filed on Aug. 16, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

1. Field of the Invention

The present invention relates to a communications circuit for reducing crosstalk, and more particularly, to a communications circuit for reducing crosstalk between a low-frequency band and a high-frequency band by adding an inductor component to a conductive power supply pattern supplying power to a first integrated passive device of the low-frequency band and a second integrated passive device of the high-frequency band.

2. Description of the Related Art

In general, transmitters in mobile communications terminals such as a cellular phone and the like, include power amplifiers for amplifying the power of a transmission signal and the power amplifiers amplify the transmission signal to an appropriate level of electric power. The power amplifiers generally perform matching and couple electric powers by using transformers each having two or more input conductive lines and one output conductive line.

In order to improve the performance of mobile communications terminals including power amplifiers and the transformers, research into reducing crosstalk that occurs between different frequency bands in a communications module of limited size is actively being carried out. Herein, crosstalk refers to a phenomenon in which a harmonic component of a low-frequency band crosses to a high-frequency band. In particular, in a global system for mobile communications (GSM) terminal, since a low-frequency band of 900 MHz and a high-frequency band of 1.8 GHz are used together, the reduction of crosstalk is a very important issue.

An aspect of the present invention provides a communications circuit capable of reducing crosstalk between a low-frequency band and a high-frequency band.

According to an aspect of the present invention, there is provided a communications circuit for reducing crosstalk including: a conductive power supply pattern supplying driving power applied from the outside; a first transformer implemented as an integrated passive device (IPD) type having a first input conductive line receiving a first signal of a low-frequency band received from a first power amplifier and a first output conductive line close to the first input conductive line and electromagnetically coupled with the first input conductive line, and receiving the driving power supplied from the conductive power supply pattern through a terminal formed on the first input conductive line; and a second transformer implemented as the IPD type having a second input conductive line receiving a second signal of a high-frequency band received from a second power amplifier and a second output conductive line close to the second input conductive line and electromagnetically coupled with the second input conductive line, and receiving the driving power supplied from the conductive power supply pattern through a terminal formed on the second input conductive line, and the conductive power supply pattern includes an inductor component.

The conductive power supply pattern may have a structure separated into a first conductive power supply pattern supplying the driving power to the first transformer and a second conductive power supply pattern supplying the driving power to the second transformer.

Specifically, the first conductive power supply pattern and the second conductive power supply pattern may include serpentine patterns, triangular-wave patterns, or quadrangular-wave patterns.

Further, the first signal may be a low-frequency signal of a 900 MHz band and the second signal maybe a high-frequency signal of a 1.8 GHz band.

The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing a communications circuit for reducing crosstalk according to an exemplary embodiment of the present invention; and

FIG. 2 is a diagram illustrating the structure of a transformer 120 of FIG. 1 .

Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. While those skilled in the art could readily devise many other varied embodiments that incorporate the teachings of the present invention through the addition, modification or deletion of elements, such embodiments may fall within the scope of the present invention.

The same or equivalent elements are referred to by the same reference numerals throughout the specification.

FIG. 1 is a diagram showing a communications circuit for reducing crosstalk according to an exemplary embodiment of the present invention, and FIG. 2 is a diagram illustrating the structure of a transformer 120 of FIG. 1 .

Referring to FIG. 1 , a communications circuit for reducing crosstalk according to an exemplary embodiment of the present invention may include high-frequency modules 110 and 120 , low-frequency modules 130 and 140 , and a conducive power supply pattern 150 for supplying driving power Vdd to the low-frequency modules 130 and 140 and the high-frequency modules 110 and 120 .

The low-frequency modules 130 and 140 may include a first power amplifier 130 receiving and amplifying a first signal of a low frequency of 900 MHz and thereafter, transferring the amplified signal to a first transformer 140 , and the first transformer 140 coupling and outputting the first signal received from the first power amplifier 130 .

The high-frequency modules 110 and 120 may include a second power amplifier 110 receiving and amplifying a second signal of a high frequency of 1.8 GHz and thereafter, transferring the amplified signal to a second transformer 120 , and the second transformer 120 coupling and outputting the second signal received from the second power amplifier 110 .

Since the first transformer 140 and the second transformer 120 have the same structure, the second transformer 120 will now be primarily described in terms of the simplification of the present invention.

Referring to FIG. 2 , the second transformer 120 according to the exemplary embodiment may include a lamination substrate, input conductive lines LI 1 and LI 2 connected to input ports 121 a , 121 b , 121 c , and 121 d , and an output conductive line LO 1 connected to output ports 123 a and 123 b.

The lamination substrate maybe a dielectric substrate having a plurality of layers. As shown in FIG. 2 , the input conductive lines LI 1 and LI 2 and the output conductive line LO 1 are disposed on the same plane of the substrate in a circumferential direction of the substrate, and a plurality of via holes V are formed on the substrate in order to prevent the input conductive lines LI 1 and LI 2 and the output conductive line LO 1 from being short-circuited due to direct contact with each other. As the lamination substrate, a high-frequency substrate may be used.

Meanwhile, the input conductive lines LI 1 and LI 2 are formed on the substrate and ends of the input conductive lines LI 1 and LI 2 are connected to two pairs of input ports 121 a and 121 b and 121 c and 121 d formed on the substrate to be provided as input terminals of respective positive ‘+’ and negative ‘−’ signals. In the exemplary embodiment, ports 121 a , 121 b , 121 c, and 121 d of both ends of two respective input conductive lines LI 1 and LI 2 may be connected to the power amplifier 110 . Further, the power Vdd may be supplied to each of the input conductive lines LI 1 and LI 2 through the conductive power supply pattern 150 . In the transformer of the exemplary embodiment, the input conductive lines may be connected to a power amplifier implemented as a CMOS type used in a mobile communications terminal.

The output conductive line LO 1 is close to each of the input conductive lines LI 1 and LI 2 to be electromagnetically coupled with the input conductive lines LI 1 and LI 2 and one end of the output conductive line LO 1 may be connected to a ground GND through the output port 123 a or 123 b . Through current supplied to the input conductive lines LI 1 and LI 2 , magnetically induced current may be generated in the output conductive line LO 1 .

Further, in the exemplary embodiment of the present invention, power supplying pads 122 a and 122 b may be formed on portions of two input conductive lines LI 1 and LI 2 , respectively. The power supplying pads 122 a and 122 b may be provided as terminals for supplying the power Vdd to the input conductive lines LI 1 and LI 2 , respectively. Positions at which the power supplying pads 122 a and 122 b are formed may be positions on the input conductive lines LI 1 and LI 2 where an electric RF swing potential is 0V. Since the CMOS power amplifier has no DC-based ground, the CMOS power amplifier uses an AC-based ground. The RF swing potential of 0V means the AC-based ground. The second transformer 120 may be implemented as an example of an integrated passive device (IPD).

Meanwhile, the conductive power supply pattern 150 supplies the driving power Vdd applied from the outside to the input conductive lines LI 1 and LI 2 of each of the transformers 120 and 140 , as shown in FIG. 1 . Specifically, the driving power Vdd is applied to the conductive power supply pattern 150 and the driving power Vdd applied to the conductive power supply pattern 150 is supplied to the power supplying pads 122 a and 122 b formed on the input conductive lines LI 1 and LI 2 of each of the transformers 120 and 140 through a conductive bar 161 or 162 disposed on the side.

According to an exemplary embodiment of the present invention, the conductive power supply pattern 150 is separated into a first conductive power supply pattern 150 b for the first transformer 140 and a second conductive power supply pattern 150 a for the second transformer 120 to increase the length of the conductive power supply pattern 150 , thereby increasing an inductor component. That is, by increasing the length of the conductive power supply pattern 150 , crosstalk that occurs due to the transferring of a harmonic component of the amplifier 130 of a low-frequency signal to the amplifier 110 of a high-frequency signal can be reduced.

Further, according to another exemplary embodiment of the present invention, in order to include the inductor component, the conductive power supply pattern 150 maybe formed in various embodiments.

According to a first exemplary embodiment of the present invention, as shown in reference numeral 151 , the first conductive power supply pattern 150 b and the second conductive power supply pattern 150 a may be formed by triangular-wave patterns 151 b and 151 a.

According to a second exemplary embodiment of the present invention, as shown in reference numeral 152 , the first conducive power supply pattern 150 b and the second conductive power supply pattern 150 a may be formed by quadrangular-wave patterns 152 b and 152 a.

According to a third exemplary embodiment of the present invention, as shown in reference numeral 153 , the first conducive power supply pattern 150 b and the second conductive power supply pattern 150 a maybe formed by serpentine patterns 153 b and 153 a.

The shapes of the conductive patterns are merely one exemplary embodiment, and the conductive patterns may be implemented to have various shapes according to the needs of those skilled in the art.

As set forth above, crosstalk between a low-frequency band and a high-frequency band can be reduced by adding an inductor component to a conductive power supply pattern supplying power to a first integrated passive device of the low-frequency band and a second integrated passive device of the high-frequency band.

While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.