Communication device

A communication device including a signal generator configured to generate a transmitting signal that uses a plurality of frequency bands, an amplifier configured to amplify and output the transmitting signal, a plurality of duplexers configured to separate and output a receiving signal and the transmitting signal, and a controller. The controller is configured to control power amplification of the transmitting signal by the amplifier based on the transmitting signal output from the duplexer, and control power amplification of the transmitting signal by the amplifier based on the transmitting signal input to the duplexer from the amplifier when a temperature is a predetermined value or more or the frequency of the transmitting signal is a predetermined value or more.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese Patent Application No. 2015-127999 (filed on Jun. 25, 2015), the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates generally to communication device, more particularly relates to a communication device capable of transmitting transmission signals by using a plurality of frequency bands.

BACKGROUND

In order to correspond to what is called a carrier aggregation that corresponds to a plurality of frequency bands and sends signals by using the a plurality of frequency bands simultaneously, a communication device in which a broadband coupler, a diplexer and a multiband switch (SW) are mounted between an antenna and a duplexer has been used.

In such a communication device, in order to keep the power of the output signal of the antenna to a predetermined value, a portion of the output signal is branched by a coupler and is detected, then the output of the amplifier is controlled based on the detection result.

SUMMARY

A communication device according to this disclosure includes:

a signal generator configured to generate a transmitting signal that uses a plurality of frequency bands;

an amplifier configured to amplify and output the transmitting signal generated by the signal generator;

a plurality of duplexers configured to separate and output a receiving signal and the transmitting signal output by the amplifier;

a first detection means configured to detect the transmitting signal output from the duplexer;

a controller configured to control power amplification of the transmitting signal by the amplifier based on the detection by the first detection means; and

a second detection means configured to detect the transmitting signal input to the duplexer from the amplifier,

wherein the controller controls the power amplification of the transmitting signal by the amplifier based on the detection by the second detection means when a temperature is a predetermined value or more or a frequency of the transmitting signal is a predetermined value or more.

A communication device according to this disclosure includes:a signal generator configured to generate a transmitting signal that uses a plurality of frequency bands;

an amplifier configured to amplify and output the transmitting signal generated by the signal generator;

a plurality of duplexers configured to separate and output a receiving signal and the transmitting signal output by the amplifier;

a first detection means configured to detect the transmitting signal output from the duplexer;

a controller configured to control power amplification of the transmitting signal by the amplifier based on the detection by the first detection means, and decrease the power amplification of the transmitting signal by the amplifier when a temperature is a predetermined value or more or a frequency of the transmitting signal is a predetermined value or more.

DETAILED DESCRIPTION

The disclosed embodiments will be described in detail below with reference to the drawings.

In the above described conventional communication device, when a decrease in the power of the output signal is detected by wave detection, the power input to the duplexer is increased to increase the output of the amplifier. When the power input to the duplexer is increased, heat generation occurs due to the passing loss in the duplexer (hereinafter appropriately abbreviated as “self heat generation”). The duplexer has characteristics in which the passing properties shift to the low frequency side at a predetermined temperature or more, and the passing loss increases in particular at high frequencies. Therefore, there was a concern that, in the duplexer, if self heat generation continues with an increase in the input power, the passing loss would increase, and as a result, self heat generation would further continue.

It would therefore be helpful to provide a communication device that can prevent continuing self heat generation of a duplexer.

First Embodiment

FIG. 1is a schematic diagram illustrating a configuration of a communication device100according to the first embodiment of this disclosure. As illustrated inFIG. 1, a communication device100includes a controller1, a radio frequency integrated circuit (RFIC)2, a multiband power amplifier (PA)3, low pass filters (LPF)4aand4b, duplexers5aand5b, a multiband switch (SW)6, a diplexer7, a broadband coupler8and an antenna (ANT)9. The communication device100also includes a coupler10between the multiband PA3and the duplexer5band a switch (SW)11that can switch the connection between the broadband coupler8and RFIC2and the connection between the coupler10and RFIC2.

It should be noted that, although two LPFs4aand4band two duplexers5aand5bare indicated for convenience, any number of them can be disposed, respectively, and the number corresponds to the frequency band used by the communication device100. Furthermore, inFIG. 1, the solid lines connecting functional blocks represent the wiring through which the power flows. Although there is a control signal or information flow between the controller1and many functional blocks, only the wiring with RFIC2is illustrated to facilitate visualization.

The controller1is configured, for example, by a microcomputer or the like that has a non-volatile memory and a processor that executes a control program stored in the memory, and controls operation of each portion. Specifically, the controller1stores the information associating the information of the detection signal from the broadband coupler8with the power of the transmitting signal on the position of the broadband coupler8and the information associating the information of the detection signal from the coupler10with the power of the transmitting signal on the position of the coupler10. Then the controller1determines the power of the transmitting signal on the position of the broadband coupler8or the power of the transmitting signal on the position of the coupler10depending on the connection state of the switch11described below, based on the information on the detection signal input from RFIC2, and controls the power amplification of the multiband PA3so that the power of these transmitting signals is included in the preferable range.

The controller1also stores a program that allows the communication device100to execute the operation illustrated inFIG. 3, which is described below, and the temperature threshold and the frequency threshold used for the processing of this program.

RFIC2is a signal generator that generates a transmitting signal such as a transmitting signal that uses a plurality of frequency bands according to a control signal from the controller1. The transmitting signal generated by RFIC2is a signal of the communication standard, such as, for example, GSM (GSM is a registered trademark in Japan, other countries, or both) (Global System for Mobile communications), LTE (Long Term Evolution), UMTS (Universal Mobile Telecommunications System), or the like. RFIC2outputs the generated transmitting signals to the multiband PA3through a signal path that is chosen depending on the type and the working frequency band of the transmitting signal. Furthermore, when a detection signal is input from the broadband coupler8or the coupler10, RFIC2outputs the information of the detection signal that has been input.

The multiband PA3amplifies the power of the transmitting signal input from RFIC2to a predetermined level and outputs the amplified transmitting signal to LPFs4aand4bor the duplexers5aand5bthrough a signal path that corresponds to the path for the signals to be input. For example, the multiband PA3outputs a transmitting signal of GSM standard or the like to LPFs4aand4b, and outputs a transmitting signal of LTE or UMTS standard or the like to the duplexers5aand5b. Furthermore, a temperature detection circuit is normally provided in the vicinity of the multiband PA3, and the temperature detection circuit outputs the measurement temperature data to the controller1. It should be noted that the temperature detection circuit is not necessarily provided in the vicinity of the multiband PA3, and it is provided in the vicinity of the duplexer5bto which the coupler10is connected.

LPFs4aand4bare filters that cut off the frequency component that is higher than a specific cutoff frequency from the transmitting signals of the GSM standard or the like that are input from the multiband PA3and output the resulting signals to the multiband SW6.

The duplexers5aand5bare filters that are used to separate the transmitting signal and the receiving signal of the standard that adopts the FDD (Frequency Division Duplex) system such as LTE, UMTS, or the like, in which data transmission and reception are carried out simultaneously by using the frequency bands different from each other, and separate the transmitting signal input from the multiband PA3and the receiving signal input from the antenna9. As a type of the duplexers5aand5b, a SAW (Surface Acoustic Wave) duplexer is commonly used. The number of duplexers in the communication device100depends on the working frequency band of the FDD system.

The multiband SW6is a switch that switches between LPFs4aand4bor duplexers5aand5bto be connected depending on the frequency band of the transmitting signal and the receiving signal to be input.

The diplexer7branches the receiving signal input from the antenna9into a high frequency band (e. g. 1 GHz or more) and a low frequency band (e. g. less than 1 GHz), and outputs the signal to the multiband SW6. As the diplexer7, a laminated type is used, for example.

The broadband coupler8is a coupler that operates in all frequency bands to which the communication device100corresponds, and outputs a portion (e.g. approx. 1/10) of the transmitting signals input by the diplexer7to the switch11and the remaining signals to the antenna9. The coupler also outputs all the receiving signals input from the antenna9to the diplexer7.

The coupler10is connected between the multiband PA3and the duplexer5b, and outputs a portion (e.g. approx. 1/100) of the transmitting signals input from the multiband PA3to the switch11and the remaining signals to the duplexer5b. It should be noted that the coupler10is connected to the duplexer that uses the frequency band that may cause the property deterioration due to self heat generation described below. Furthermore, a plurality of couplers10may be connected to a plurality of duplexers, respectively. The coupler10may also be built in the multiband PA3.

According to the control signal from the controller1, the switch11switches between the state where the broadband coupler8and RFIC2are connected (hereinafter appropriately referred to as “the first state”) and the state where the coupler10and RFIC2are connected (hereinafter appropriately referred to as “the second state”). As a result of this, in the first state, the broadband coupler8functions as a first detection means that detects the power of the transmitting signal on the position of the broadband coupler8, and in the second state, the coupler10functions as a second detection means that detects the power of the transmitting signal on the position of the coupler10.

Assuming that the switch11is in the first state all the time, the duplexer5bmay be damaged when the input power Pin increases. Its mechanism is described below.FIG. 2is a conceptual diagram illustrating the frequency dependence of the passing properties of the duplexer5b. Here, the horizontal axis is a frequency and indicates an increase in the frequency from the left to the right, and the vertical axis is a passing loss and indicates an increase in the passing loss from the upward to the downward.

For the duplexer5b, the passing properties shift to the low frequency side as the temperature rises, and the passing loss increases in particular at high frequencies. For example, as illustrated inFIG. 2, at the frequency f2, which is higher than the frequency f1, there is a greater increase in the passing loss when the temperature increases from 25° C. to 60° C.

When Pin increases to be a predetermined value or more, heat generation occurs due to passing loss in the duplexer5b(hereinafter approximately abbreviated as “self heat generation”). Since the passing properties of the duplexer5bshifts to the low frequency side due to this self heat generation, the passing loss further increases and more self heat generation occurs. At the same time, the detected power decreases due to an increase in the passing loss, and thus the controller1increases the output power of the transmitting signal, and as a result of this, there is a further increase in Pin. Thus, in the duplexer5b, self heat generation may continue to increase due to an increase in the passing loss.

In order to avoid the above described situation, the communication device100allows the controller1to execute the operation described below.FIG. 3is a flow chart illustrating an operation example of the communication device100according to this embodiment. This operation example is executed while the communication device100outputs transmitting signals. Furthermore, during a normal operation, the switch11is connected to the first state, that is, to the broadband coupler8.

First, the controller1acquires the information of the measured temperature by the temperature detection circuit and of the working frequency of a transmitting signal (step S101). Here, the information of the working frequency of the transmitting signal is the information of the working frequency of the transmitting signal that is generated and controlled by the controller1using RFIC2at the time when this step is executed.

Next, the controller1determines whether or not the temperature or the frequency acquired at step S101is a predetermined value or more (step S102). Here, a predetermined value means a threshold of the temperature or a threshold of the frequency stored by the controller1, and when the frequency is a predetermined value or more, it means that there is a frequency that is the threshold of the frequency or more in the working frequencies of the transmitting signal. It should be noted that the threshold of the temperature and that of the frequency stored by the controller1may be thresholds over which self heat generation of the duplexer5bmay continue when the switch11is in the first state all the time.

When the controller1determines that the temperature and the frequency are less than the predetermined value (No at step S102), the process returns to step S101. On the other hand, when the controller1determines that the temperature is the predetermined value or more or the frequency is the predetermined value or more (Yes at step S102), it switches the switch11to the second state, that is, to the coupler10side (step S103).

According to this embodiment, even if the temperature exceeds the predetermined value and the frequency exceeds the predetermined value, then as a result the passing loss of the duplexer5bincreases, when the switch11switches to the coupler10side, the power Pin that is input to the duplexer5bis detected, and as a result, the detection result is not affected by the increase in the passing loss of the duplexer5b. Thus, an increase in Pin can be prevented, and as a result, continuing self heat generation of the duplexer5bcan be prevented.

It should be noted that, at step S102, instead of determining whether or not the temperature is a predetermined value or more or the frequency is a predetermined value of more, whether or not the temperature is the predetermined value or more, whether or not the frequency is the predetermined value or more, or whether or not the temperature and the frequency are the predetermined values or more may be determined.

Second Embodiment

FIG. 4is a schematic diagram illustrating a configuration of a communication device200according to the second embodiment of this disclosure. As illustrated inFIG. 4, the communication device200has, instead of the coupler10, a branch point between the multiband PA3and the duplexer5b, and a resistance12between the branch point and the switch11. Other than that, the configuration is the same as that of the communication device100according to the first embodiment, and thus the description is omitted.

When the switch11is connected to the resistance12side, a portion of the transmitting signal input from the multiband PA3is input to RFIC2through the resistance12as a detection signal, and Pin decreases. For example, when the resistance12of 100Ω is used, Pin decreases by about 1.2 dB.

FIG. 5is a flow chart illustrating an operation example of the communication device200according to this embodiment. This operation example is executed while the communication device200outputs transmitting signals. During a normal operation, the switch11is connected to the first state, that is, the broadband coupler8. The steps S201and S202of this operation example are the same as the steps S101and S102of the operation example of the first embodiment, thus the explanation is omitted.

The controller1switches the switch11to the resistance12side (step S203) when it determines that the temperature is a predetermined value or more or the frequency is a predetermined value of more (Yes at step S202).

According to this embodiment, even if the temperature exceeds the predetermined value and the frequency exceeds the predetermined value and as a result the passing loss of the duplexer5bincreases, when the switch11switches to the resistance12side, the power Pin input to the duplexer5bis detected, and as a result of this, the detection result is not affected by the increase in the passing loss of the duplexer5b. Furthermore, a portion of the transmitting signal input from the multiband PA3is input to RFIC2as a detection signal, and as a result, Pin decreases. Thus, an increase in Pin can be prevented, and as a result, continuing self heat generation of the duplexer5bcan be prevented.

It should be noted that the resistance12of the communication device200according to this embodiment may be combined with the coupler10of the communication device100according to the first embodiment.

Third Embodiment

FIG. 6is a schematic diagram illustrating a configuration of a communication device300according to the third embodiment of this disclosure. As illustrated inFIG. 6, the communication device300includes a NTC (Negative Temperature Coefficient) thermistor between the broadband coupler8and the switch11. Other than that the configuration is the same as that of the communication device200according to the second embodiment, thus the explanation is omitted.

The NTC thermistor13is a resistance whose resistance decreases as the temperature rises. When the switch11is in the first state, the resistance of the NTC thermistor13decreases as the temperature rises, and as a result, a dummy power on the position of the broadband coupler8detected as a transmitting signal is detected larger than really it is, and as a result, even if the temperature rises, the controller1can suppress an increase in the output power of the transmitting signal. It should be noted that, in order to exhibit this function effectively, the NTC thermistor13may be disposed in the vicinity of the duplexer5b.

Thus, according to this embodiment, even if the temperature exceeds the predetermined value and the frequency exceeds the predetermined value and as a result the passing loss of the duplexer5bincreases, when the switch11switches to the resistance12side, the power Pin input to the duplexer5bis detected, and as a result, the detection result is not affected by the increase in the passing loss of the duplexer5b. Furthermore, a portion of the transmitting signal input from the multiband PA3is input to RFIC2as a detection signal, and as a result, Pin decreases. Moreover, an increase in Pin with increasing temperature can be suppressed by the NTC thermistor13even before the switch11switches to the resistance12side. Thus, an increase in Pin can be prevented, and as a result, continuing self heat generation of the duplexer5bcan be prevented.

It should be noted that the NTC thermistor13of the communication device300according to this embodiment may be provided between the broadband coupler8and the switch11of the communication device100according to the first embodiment.

Fourth Embodiment

FIG. 7is a schematic diagram illustrating a configuration of a communication device400according to the fourth embodiment of this disclosure. As illustrated inFIG. 7, the communication device400does not include the coupler10and the switch11. Other than that the configuration is the same as that of the communication device100according to the first embodiment, thus the explanation is omitted. In the communication device400, a transmitting signal on the position of the broadband coupler8is detected.

FIG. 8is a flow chart illustrating an operation example of the communication device according to this embodiment. This operation example is executed while the communication device400outputs transmitting signals. The steps S301and S302of this operation example are the same as the steps S101and S102of the operation example of the first embodiment, thus the explanation is omitted.

When the controller1determines that the temperature is the predetermined value or more or the frequency is the predetermined value or more (Yes at step S302), it decreases the power amplification of the transmitting signal by the multiband PA3(step S303). Concerning the amount of decrease in the power amplification, when the defined value of output power is 23 dBm, for example, it is decreased by about 1 dBm, and the resulting value is about 22 dBm.

As described above, according to this embodiment, even if the temperature exceeds the predetermined value and the frequency exceeds the predetermined value and as a result the passing loss of the duplexer5bincreases, the controller1decreases the power amplification of the transmitting signal by the multiband PA3, and as a result, Pin decreases. Therefore, an increase in Pin can be prevented, and as a result, continuing self heat generation of the duplexer5bcan be prevented.

It should be noted that control of decrease in the power amplification by the controller1of the communication device400according to this embodiment may be combined with each communication device100,200and300according to the first through third embodiments.

According to the communication device of this disclosure, continuing self heat generation of a duplexer can be prevented.

Although this disclosure has been described with reference to the accompanying drawings and embodiments, it is to be noted that various changes and modifications will be apparent to those skilled in the art based on this disclosure. Therefore, such changes and modifications are to be understood as included within the scope of this disclosure. For example, the functions and the like included in the members, units, steps, and the like may be reordered in any logically consistent way. Furthermore, units, steps, and the like may be combined into one or divided. Furthermore, it may be any combination of any of the first embodiment and the second embodiment and the third embodiment and the fourth embodiment.