TWI423599B - Method for reducing rf circuit area and communication apparatus using the same - Google Patents

Description

Method for reducing RF circuit area and communication device thereof

This invention relates to a radio frequency circuit, and more particularly to a method of reducing the area of a radio frequency circuit and a communication device using the same.

At present, wireless communication devices are becoming more and more diverse, such as smart mobile phones, multimedia players, personal digital assistants, and satellite navigation devices. Electronic devices with wireless transmission functions are also being improved toward light, thin and short design concepts to achieve electronic products that are more suitable for daily use. It is worth mentioning that the RF circuit is an indispensable component of many wireless communication systems, and it is a major component of the overall performance of the wireless communication device.

Taking the mobile telephone communication system as an example, since different countries have different telecommunication specifications, in order to achieve roaming between different countries, the wireless communication device must support multiple frequency bands. For example, as shown in the following list 1, in Europe, the frequency band used by the Global System for Mobile Communications (hereinafter referred to as 2G) for the second generation mobile phone communication technology specification (abbreviated as 2G) is 880 to 960 MHz and 1710 to 1880 MHz. The frequency band used by the wideband code division multiplexing multiple access system (referred to as WCDMA) belonging to the third generation mobile phone communication technical specification (referred to as 3G) has 1920 to 2170 MHz and 880 to 960 MHz. However, in the United States, the frequency bands used by GSM are 824-894 MHz and 1850-1990 MHz, and the frequency bands used by WCDMA are 1850-1990 MHz and 824-894 MHz.

In other words, in order to achieve roaming in the United States and Europe, the radio frequency circuit and antenna of the wireless communication device must simultaneously support the multiple frequency bands listed in Table 1 above. Generally, each frequency band has an independent transceiver circuit path, so wireless communication devices supporting multiple frequency bands usually have a large RF circuit area. However, as national telecommunications specifications continue to increase the available wireless communication bands, for example, WCDMA systems will continue to add Band 9 to Band 10 bands, and the RF circuit area of wireless communication devices will continue to increase. As a result, the overall circuit cost of the wireless communication device will continue to increase, and the space available for other modules (eg, touch modules, camera modules, audio modules) and the like can be reduced.

In view of the above, an exemplary embodiment of the present invention provides a method of reducing the area of a radio frequency circuit and a communication apparatus using the same, using an isolation apparatus or a filtering apparatus to reduce interference of other received signals or transmitted signals. In addition, a common receive path is also used for signals of at least two receive bands whose frequencies overlap, and the cost of the components and the space of the overall radio frequency circuit are reduced accordingly.

According to an exemplary embodiment of the present invention, the present invention provides a method for reducing the area of a radio frequency circuit, which is suitable for a communication device operating in at least a first frequency band and at least a second frequency band, and the method for reducing the area of the radio frequency circuit Includes the following steps. Using a transceiver to provide a first signal of the first frequency band and a second signal of the second frequency band, and receiving a third signal of the first frequency band and a fourth signal of the second frequency band, and the frequency of the third signal Overlaps the frequency of the fourth signal. Furthermore, an isolator is used to receive the first signal and to isolate the second signal, the third signal, and the fourth signal into the transceiver. In addition, the third signal and the fourth signal are supplied to the transceiver and the second signal through a duplexer, and the third signal and the fourth signal share a common reception between the duplexer and the transceiver. path.

In an exemplary embodiment of the present invention, the method for reducing the area of the radio frequency circuit further includes the following steps. The first signal and the second signal are wirelessly transmitted by using an antenna coupled to the isolator and the duplexer, and the third signal and the fourth signal are wirelessly received. In addition, a plurality of signals of the first frequency band and the second frequency band are switched by a switch coupled to the antenna, the isolator, and the duplexer.

In an exemplary embodiment of the present invention, the method for reducing the area of the radio frequency circuit further includes: when the communication device operates in the first frequency band, transmitting the first signal from the transceiver to the antenna through the isolator, and transmitting The duplexer and the common receiving path transmit the third signal from the antenna to the transceiver; and when the communication device operates in the second frequency band, the second signal is transmitted from the transceiver to the antenna through the duplexer, and is transmitted through the transceiver The duplexer and the common receive path transmit the fourth signal from the antenna to the transceiver.

According to another exemplary embodiment of the present invention, the present invention provides a method for reducing the area of a radio frequency circuit, which is suitable for a communication device operating in at least a first frequency band and at least a second frequency band, and the above-mentioned reducing the area of the radio frequency circuit The method includes the following steps. Using a transceiver to provide a first signal of the first frequency band and a second signal of the second frequency band, and receiving a third signal of the first frequency band and a fourth signal of the second frequency band, and the frequency of the third signal Overlaps the frequency of the fourth signal. Moreover, the first signal and the second signal are wirelessly transmitted by using an antenna coupled to the transceiver, and the third signal and the fourth signal are wirelessly received. In addition, the first signal is amplified by a first power amplifier coupled to the transceiver; the third signal and the fourth signal are supplied to the transceiver and the second signal are received through a duplexer coupled to the transceiver. And the third signal and the fourth signal share a common receiving path between the duplexer and the transceiver. A plurality of signals coupled to the first frequency band and the second frequency band are further switched by a switch coupled to the antenna and the duplexer. The first signal is also received by a filter coupled to the first power amplifier, the duplexer, and the switch, and the circuit path connecting the filter to the first power amplifier, the duplexer, and the switch is filtered. The noise on the filter, and the filter essentially only allows the first signal to pass.

In accordance with an exemplary embodiment of the present invention, the present invention provides a communication device adapted to operate in at least a first frequency band and at least a second frequency band. The above communication device comprises a transceiver, an isolator and a duplexer. The transceiver is configured to provide a first signal of the first frequency band and a second signal of the second frequency band, and receive a third signal of the first frequency band and a fourth signal of the second frequency band, and the frequency of the third signal The frequencies of the four signals overlap. The isolator is coupled to the transceiver for receiving the first signal and isolating the second signal, the third signal, and the fourth signal into the transceiver. In addition, the duplexer is coupled to the transceiver for providing the third signal and the fourth signal to the transceiver and the second signal, and the third signal and the fourth signal share a duplex between the duplexer and the transceiver. Common receiving path.

In accordance with another exemplary embodiment of the present invention, the present invention provides a communication device adapted to operate in at least a first frequency band and at least a second frequency band. The communication device includes a transceiver, an antenna, a first power amplifier, a duplexer, a switch, and a filter. The transceiver is configured to provide a first signal of the first frequency band and a second signal of the second frequency band, and receive a third signal of the first frequency band and a fourth signal of the second frequency band, and the frequency of the third signal The frequencies of the four signals overlap. An antenna is coupled to the transceiver for wirelessly transmitting the first signal and the second signal, and wirelessly receiving the third signal and the fourth signal. The first power amplifier is coupled to the transceiver for amplifying the first signal. a duplexer coupled to the transceiver for providing the third signal and the fourth signal to the transceiver and receiving the second signal, and the third signal and the fourth signal sharing a common reception between the duplexer and the transceiver path. The switch is coupled to the antenna and the duplexer for switching the plurality of signals in the first frequency band and the second frequency band. In addition, the filter is coupled to the first power amplifier, the duplexer and the switch for receiving the first signal, and filtering the circuit path connecting the filter to the first power amplifier, the duplexer and the switch. The noise, while the filter essentially only allows the first signal to pass.

Based on the above, in the above embodiments of the present invention, a method for reducing the area of a radio frequency circuit and a communication device using the same are provided, wherein the isolation device is used to isolate other received signals or transmitted signals, or the filtering device is used to filter other signals in a transmission. Noise generated in the signal path to reduce interference from other received or transmitted signals to the power amplifier. In addition, a common receive path is also used for signals of at least two receive bands whose frequencies overlap, and the cost of the components and the space of the overall radio frequency circuit are reduced accordingly.

The above described features and advantages of the present invention will be more apparent from the following description.

The present invention will be described in detail with reference to the exemplary embodiments of the invention.

1 is a system block diagram of a communication device 100 suitable for multi-band operation, in accordance with an exemplary embodiment of the present invention. In FIG. 1, the RF circuit portion of the communication device 100 is mainly illustrated, and the communication device 100 is applicable to at least a first frequency band (for example, Band 8 of WCDMA) and at least a second frequency band (for example, Table 1 above). Show Band 1). Referring to FIG. 1 , the RF circuit of the communication device 100 includes an antenna module 110 , a switch 120 , an isolator 130 , a duplexer 140 , and a first power amplifier (Power Amplifier, PA). 152. A second power amplifier 154 and a transceiver 160. However, the present invention is not limited to the above, and the communication device 100 can support more than two frequency bands, multi-mode or multiple communication protocol standards. In addition, the communication device 100 may further include other components, such as a processor module (not shown), a memory module (not shown), a display module (not shown), and an input module (not shown).

Referring to FIG. 1, in the exemplary embodiment, the transceiver 160 is configured to provide a first signal of the first frequency band and a second signal of the second frequency band, and receive the third signal and the second frequency band of the first frequency band. The fourth signal, wherein the frequency of the third signal overlaps with the frequency of the fourth signal. It is worth mentioning here that, more precisely, in the frequency division duplex mode (referred to as FDD for short), the first frequency band has both the first transmission band and the first reception band, and the second band has the second transmission at the same time. Band and second receive band. In addition, the frequency of the first signal belongs to the first transmission band (for example, the transmission band of Band 4 used in the United States, the frequency is between 1710 MHz and 1755 MHz), and the frequency of the second signal belongs to the second transmission band (for example: the United States) The receiving band of Band 4 used has a frequency between 2110MHz and 2155MHz. The frequency of the third signal belongs to the first receiving frequency band (for example, the transmitting band of Band 1 used in Europe, the frequency is between 1920MHz and 1980MHz. Between) and the frequency of the fourth signal belongs to the second receiving band (for example, the receiving band of Band 1 used in Europe, the frequency is between 2110 MHz and 2170 MHz). Moreover, the radio frequency circuit of the communication device 100 operates only in one frequency band, that is, when the communication device 100 operates in the first frequency band, the communication device 100 cannot transmit or receive the radio frequency signal of the second frequency band. Conversely, when the communication device 100 operates in the second frequency band, the communication device 100 cannot transmit or receive the radio frequency signal of the first frequency band.

Referring to FIG. 1 , the isolator 130 is coupled to the transceiver for receiving the first signal and isolating the second signal, the third signal, and the fourth signal into the transceiver. It is worth mentioning here that the isolator 130 only transmits the first signal from the first power amplifier 152 to the switch 120 and isolates the second signal, the third signal and the fourth signal to prevent these signals from entering (or coupling). Entering) a first power amplifier 152 or transceiver 160. The duplexer 140 is coupled to the transceiver 160 for providing the third signal and the fourth signal to the transceiver 160 and the second signal, and the third signal and the fourth signal share the duplexer 140 and the transceiver 160. A common receiving path DRX between. The antenna 110 is coupled to the isolator 130 and the duplexer 140 for wirelessly transmitting the first signal and the second signal, and wirelessly receiving the third signal and the fourth signal. The switch 120 is coupled to the antenna 110, the isolator 130, and the duplexer 140 for switching a plurality of signals of the first frequency band and the second frequency band. That is, when the communication device 100 operates in the first frequency band, the switch 120 switches the radio frequency circuit path of the communication device 100 such that the transceiver 160 can only transmit the first signal and receive the third signal. Conversely, when the communication device 100 is operating in the second frequency band, the switch 120 switches the RF circuit path of the communication device 100 such that the transceiver 160 can only transmit the second signal and receive the fourth signal.

Referring to FIG. 1 , the first power amplifier 152 is coupled to the transceiver 160 and the isolator 130 for amplifying the first signal. In addition, the second power amplifier 154 is coupled to the transceiver 160 and the duplexer 140 for amplifying the second signal. Moreover, when the communication device 100 operates, it has the following circuit operation features. When the communication device 100 operates in the first frequency band, the first signal is transmitted by the transceiver 160 to the antenna 110 through the isolator 130, and the third signal is transmitted from the antenna 110 to the transceiver 160 through the duplexer 140 and the common receiving path DRX. In addition, when the communication device 100 operates in the second frequency band, the second signal is transmitted from the transceiver 160 to the antenna 110 through the duplexer 140, and the fourth signal is transmitted from the antenna 110 to the transceiver through the duplexer 140 and the common receiving path DRX. 160.

2 is a system block diagram of a communication device 200 suitable for multi-band operation, in accordance with another exemplary embodiment of the present invention. Referring to FIG. 1 and FIG. 2 simultaneously, the communication device 200 is substantially similar to the communication device 100, but in the communication device 200, the filter 230 replaces the isolator 130 of the communication device 100. In addition, the filter 230 is coupled to the first power amplifier 152, the duplexer 140, and the switch 120 for receiving the first signal, and filtering the filter 230 with the first power amplifier 152, the duplexer 140, and the switch. The noise on the circuit path of 120 is connected, wherein the filter 230 substantially only allows the first signal to pass. As such, interference of the second, third, and fourth signals can be reduced to prevent these signals from entering (or coupling into) the first power amplifier 152 or transceiver 160.

3 is a flow chart of a method 300 of reducing the area of a radio frequency circuit, in accordance with an exemplary embodiment of the present invention. Referring to FIG. 1 and FIG. 3 simultaneously, the method 300 for reducing the RF circuit area includes the following steps. In step S302, a transceiver 160 is used to provide a first signal of the first frequency band and a second signal of the second frequency band, and a third signal of the first frequency band and a fourth signal of the second frequency band, and a third signal. The frequency of the signal overlaps with the frequency of the fourth signal. In step S304, an isolator 130 is used to receive the first signal and to isolate the second signal, the third signal, and the fourth signal into the transceiver 160. In step S306, the third signal and the fourth signal are supplied to the transceiver 160 and the second signal is transmitted through a duplexer 140, and the third signal and the fourth signal share the duplexer 140 and the transceiver 160. A common receiving path DRX between. In step S308, a plurality of signals of the first frequency band and the second frequency band are switched by a switch 120 coupled to the antenna 110, the isolator 130, and the duplexer 140.

In step S310, the first signal and the second signal are wirelessly transmitted by using the antenna 110 coupled to the isolator 130 and the duplexer 140, and the third signal and the fourth signal are wirelessly received. In step S312, it is determined that the current communication device 100 is operating in the first frequency band or the second frequency band. If the communication device 100 is currently operating in the first frequency band, the process proceeds to step S314. Conversely, if the communication device 100 is operating in the second frequency band, the process proceeds to step S316. In step S314, when the communication device 100 operates in the first frequency band, the first signal is transmitted from the transceiver 160 to the antenna 110 through the isolator 130, and the third signal is transmitted from the antenna through the duplexer 140 and the common receiving path DRX. 110 is transmitted to transceiver 160. In step S316, when the communication device 100 operates in the second frequency band, the second signal is transmitted from the transceiver 160 to the antenna 110 through the duplexer 140, and the fourth signal is transmitted through the duplexer 140 and the common receiving path DRX. Antenna 110 is transmitted to transceiver 160. After step S314 or step S316, the method 300 of reducing the area of the radio frequency circuit ends here.

4 is a flow chart of a method 400 of reducing the area of a radio frequency circuit in accordance with another exemplary embodiment of the present invention. Referring to FIG. 2 and FIG. 4 simultaneously, the method 400 for reducing the RF circuit area includes the following steps. In step S402, the first signal of the first frequency band and a second signal of the second frequency band are provided by the transceiver 160, and the third signal of the first frequency band and the fourth signal of the second frequency band are received, and the third signal is received. The frequency overlaps with the frequency of the fourth signal. In step S404, the first signal is amplified using a first power amplifier 152 coupled to the transceiver 160. In step S406, the third signal and the fourth signal are supplied to the transceiver 160 and the second signal is received through the duplexer 140 coupled to the transceiver 160, and the third signal and the fourth signal share the duplexer 140 and A common receive path DRX between transceivers 160. In step S408, a plurality of signals of the first frequency band and the second frequency band are switched by the switch 120 coupled to the antenna 110 and the duplexer 140.

In step S410, the first signal is received by the filter 230 coupled to the first power amplifier 154, the duplexer 140, and the switch 120, and filtered in the filter 230 and the first power amplifier 152, the duplexer 140. The noise on the circuit path connected to the switch 120. In step S412, it is determined that the communication device 100 is currently operating in the first frequency band or the second frequency band. Steps S412 to S416 are substantially the same as steps S312 to S316 in FIG. 3, and thus details thereof will not be described in detail herein. After step S414 or step S416, the method 400 of reducing the area of the radio frequency circuit ends here.

FIG. 5 is a system block diagram of a communication device 500 suitable for multi-band operation, in accordance with another exemplary embodiment of the present invention. The communication device 500 is substantially similar to the communication device 100 or the communication device 200, but in the communication device 500, the communication device 500 further includes another module to transmit or receive a fifth channel (for example, Band 2 of WCDMA). The signal and the sixth signal, and the frequency of the fifth signal belongs to the third transmission channel of the third channel (for example, between 1850 MHz and 1910 MHz), and the frequency of the sixth signal belongs to the third receiving channel of the third channel (for example , between 1930MHz and 1990MHz). In addition, the communication device 500 is coupled to the transceiver 150 by a third power amplifier 156 for amplifying the fifth signal, and coupled to the switch 120 through another duplexer 142 to transmit the fifth signal to the antenna 110.

On the other hand, the transceiver 150 of the communication device 500 receives the sixth signal received by the antenna 110 through the switch 120, the duplexer 142, and a single receiving path SRX. It is worth mentioning that the isolator 130, the duplexer 140 and the duplexer 142 are coupled together, but the isolator 130 isolates the second signal and the third signal when the communication device 500 operates in the first frequency band. The fourth signal, the fifth signal, and the sixth signal enter the first power amplifier 152. However, the present invention is not limited to the above, and the communication device provided by the present invention can also operate in three or more frequency bands. Additionally, in other exemplary embodiments of the present invention, the communication device may also replace the isolator with a filter to prevent other radio frequency signals from entering the power amplifying circuit path of the transmitted signal of the first frequency band.

In summary, in various exemplary embodiments of the present invention, a method for reducing an RF circuit area and a communication device using the same are provided, and an isolation device or a filtering device is used to reduce other received signals or transmitted signals to a power amplifier. interference. In addition, signals of at least two of the received frequency bands that overlap in frequency use a common receive path and thereby reduce the cost of the component and the space of the overall RF circuit.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100, 200, 500‧‧‧ communication devices

110‧‧‧Antenna module

120‧‧‧Switch

130‧‧‧Isolator

140, 142‧‧‧ duplexer

152‧‧‧First power amplifier

154‧‧‧second power amplifier

156‧‧‧ Third Power Amplifier

160‧‧‧ transceiver

230‧‧‧ filter

300, 400‧‧‧Methods for reducing the area of RF circuits

S302~S316, S402~S416‧‧‧ steps

DRX‧‧‧Common receiving path

SRX‧‧‧ single receiving path

1 is a system block diagram of a communication device suitable for multi-band operation, in accordance with an exemplary embodiment of the present invention.

2 is a system block diagram of a communication device suitable for multi-band operation, in accordance with another exemplary embodiment of the present invention.

FIG. 3 is a flow chart showing a method of reducing the area of a radio frequency circuit according to an exemplary embodiment of the invention.

4 is a flow chart showing a method of reducing the area of a radio frequency circuit according to another exemplary embodiment of the present invention.

FIG. 5 is a system block diagram of a communication device suitable for multi-band operation according to another exemplary embodiment of the present invention.

S302~S316. . . step

Claims (10)

A method for reducing the area of a radio frequency circuit is applicable to a communication device operating in at least a first frequency band and at least a second frequency band, the method for reducing the area of the radio frequency circuit comprising: using a transceiver to provide one of the first frequency bands a first signal and a second signal of the second frequency band, and a third signal of the first frequency band and a fourth signal of the second frequency band, wherein a frequency of the third signal and a frequency of the fourth signal Overlapping; using an isolator to receive the first signal and isolating the second signal, the third signal and the fourth signal entering the transceiver; providing the third signal and the fourth signal through a duplexer Receiving the second signal, wherein the third signal and the fourth signal share a common receiving path between the duplexer and the transceiver; when the communication device operates in the first frequency band, The isolator transmits the first signal from the transceiver to the antenna, and transmits the third signal from the antenna to the transceiver through the duplexer and the common receive path; and when the communication When the second frequency band is operated, the second signal is transmitted from the transceiver to the antenna through the duplexer, and the fourth signal is transmitted from the antenna to the common receiving path through the duplexer transceiver. The method for reducing the area of a radio frequency circuit as described in claim 1 further includes: transmitting wirelessly by using an antenna coupled to the isolator and the duplexer Transmitting the first frequency band with the first signal and the second signal, and wirelessly receiving the third signal and the fourth signal; and transmitting through an antenna coupled to the antenna, the isolator, and the duplexer The signals of the second frequency band. The method for reducing the area of a radio frequency circuit as described in claim 1 further includes amplifying the first signal and amplifying the second signal. A method for reducing the area of a radio frequency circuit is applicable to a communication device operating in at least a first frequency band and at least a second frequency band, the method for reducing the area of the radio frequency circuit comprising: using a transceiver to provide one of the first frequency bands a first signal and a second signal of the second frequency band, and a third signal of the first frequency band and a fourth signal of the second frequency band, wherein a frequency of the third signal and a frequency of the fourth signal Overlap; wirelessly transmitting the first signal and the second signal by using an antenna coupled to the transceiver, and wirelessly receiving the third signal and the fourth signal; utilizing a first power coupled to the transceiver An amplifier for amplifying the first signal; providing the third signal and the fourth signal to the transceiver and receiving the second signal through a duplexer coupled to the transceiver, wherein the third signal and the third The four signals share a common receiving path between the duplexer and the transceiver; and the switches of the first frequency band and the second frequency band are switched by an switch coupled to the antenna and the duplexer; Profit Coupled to the first power amplifier, the duplexer with the switch a filter for receiving the first signal and filtering a noise on a circuit path connecting the filter to the first power amplifier, the duplexer, and the switch, wherein the filter is substantially only allowed Passing the first signal; when the communication device operates in the first frequency band, transmitting the first signal from the transceiver to the antenna through the filter, and transmitting the first through the duplexer and the common receiving path Transmitting a signal from the antenna to the transceiver; and transmitting, when the communication device is in the second frequency band, the second signal from the transceiver to the antenna through the duplexer, and transmitting the duplexer through the duplexer The common receive path transmits the fourth signal from the antenna to the transceiver. The method for reducing the area of a radio frequency circuit as described in claim 4, further comprising: amplifying the second signal by using a second power amplifier coupled to the transceiver and the duplexer. A communication device is adapted to operate in at least a first frequency band and at least a second frequency band, the communication device comprising: a transceiver for providing a first signal of the first frequency band and a first frequency band of the second frequency band a second signal, and a third signal of the first frequency band and a fourth signal of the second frequency band, wherein a frequency of the third signal overlaps with a frequency of the fourth signal; an isolator coupled to the transceiver And receiving the first signal, and isolating the second signal, the third signal and the fourth signal entering the transceiver; a duplexer coupled to the transceiver for providing the third signal and the fourth signal to the transceiver and receiving the second signal, wherein the third signal shares the duplexer with the fourth signal a common receiving path with the transceiver, when the communication device operates in the first frequency band, the first signal is transmitted from the transceiver to the antenna through the isolator, and the third signal passes through the duplex And the common receiving path is transmitted from the antenna to the transceiver, and when the communication device operates in the second frequency band, the second signal is transmitted to the antenna through the transceiver through the duplexer, and the fourth signal The antenna is transmitted to the transceiver through the antenna through the duplex receiving path. The communication device of claim 6, further comprising: an antenna coupled to the isolator and the duplexer for wirelessly transmitting the first signal and the second signal, and wirelessly receiving the third a signal and the fourth signal; and an switch coupled to the antenna, the isolator and the duplexer for switching the signals of the first frequency band and the second frequency band. The communication device of claim 6, further comprising: a first power amplifier coupled to the transceiver and the isolator for amplifying the first signal; and a second power amplifier coupled to the second power amplifier The transceiver and the duplexer are configured to amplify the second signal. A communication device is adapted to operate in at least a first frequency band and at least a second frequency band, the communication device comprising: a transceiver for providing a first signal and the first frequency band of the first frequency band a second signal of the second frequency band, and a third signal of the first frequency band and a fourth signal of the second frequency band, wherein a frequency of the third signal overlaps with a frequency of the fourth signal; an antenna, coupled Connected to the transceiver for wirelessly transmitting the first signal and the second signal, and wirelessly receiving the third signal and the fourth signal; a first power amplifier coupled to the transceiver for amplifying the a first signal, coupled to the transceiver, for providing the third signal and the fourth signal to the transceiver and receiving the second signal, wherein the third signal is shared with the fourth signal a common receiving path between the duplexer and the transceiver; a switch coupled to the antenna and the duplexer for switching the signals of the first frequency band and the second frequency band; and a a filter coupled to the first power amplifier, the duplexer and the switch for receiving the first signal, and filtering the filter and the first power amplifier, the duplexer and the switch a noise on the path of the connected circuit, where The filter substantially only allows the first signal to pass. When the communication device operates in the first frequency band, the first signal is transmitted by the transceiver to the antenna through the filter, and the third signal passes through the duplex And the common receiving path is transmitted from the antenna to the transceiver, and when the communication device operates in the second frequency band, the second signal is transmitted to the antenna through the transceiver through the duplexer, and the fourth signal The antenna is transmitted to the transceiver through the antenna through the duplex receiving path. The communication device as described in claim 9 further includes: A second power amplifier is coupled to the transceiver and the duplexer for amplifying the second signal.