JP2012015591A - Output control device and transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably adjust transmission electric power regardless of a size of the transmission electric power.SOLUTION: An output control device (15) adjusts gain of amplification means (121) by detecting one part of an output signal output from the amplification means by detection means (152). The output control device comprises: combining means (151) for combining one part of the output signal with the detection means; and changing means (154) for changing a combining amount (155) according to an electric power value (20) of the output signal.

Description

  The present invention relates to a technical field of an output control device that adjusts the gain of an amplifier according to, for example, a detection result of a part of an output signal of the amplifier, and a transmitter (for example, a wireless transmitter) that transmits the output signal.

  In a wireless transmitter such as a mobile phone, automatic power control (APC) is performed in order to keep transmission power constant or a desired value. The automatic power control is performed by, for example, feedback control shown below. First, a coupler such as a coupling capacitor extracts a part of the transmission signal output from the power amplifier. A part of the extracted transmission signal is detected by a detector. Thereafter, the comparison result between the detection voltage that is the output of the detector and a predetermined reference voltage (reference voltage) is fed back to the power amplifier (that is, feedback), thereby adjusting the gain of the power amplifier. For example, when the detection voltage is lower than the reference voltage, the input power of the power amplifier is increased, or the gain of the power amplifier (in other words, the output) is increased by adjusting the bias. On the other hand, when the detection voltage is higher than the reference voltage, the input power of the power amplifier is lowered or the gain of the power amplifier is lowered by adjusting the bias. As a result, the power of the transmission signal output from the power amplifier (that is, transmission power) is kept constant or at a desired value.

  The power amplifier has a characteristic that the output impedance changes when the power supply voltage changes. For this reason, even when the power (transmission power) of the transmission signal output from the power amplifier changes, a state in which the detection voltage of the detector does not change occurs. As a result, automatic power control is not performed. For this reason, there has been proposed a technique for adjusting the amount of coupling to the detector (in other words, the amount of coupling of the coupler) in accordance with the change in the power supply voltage of the power amplifier.

JP-A-8-274659

  By adjusting the coupling amount according to the change in the power supply voltage of the power amplifier, the accuracy of control of the transmission power with respect to the change in the power supply voltage of the power amplifier is improved. However, since the coupling amount is constant in an environment where the power supply voltage of the power amplifier is constant, the following technical problems may occur.

  First, if the transmission power is relatively large, the technical problem of degrading the distortion characteristics of the radio transmitter because the operating point of the power amplifier approaches the saturation region by increasing the gain of the power amplifier. cause. On the other hand, when the transmission power is relatively small, the amount of detection becomes small due to a decrease in the absolute amount of the transmission signal coupled to the detector. Therefore, a technical problem that the detection accuracy of the transmission power is lowered and the adjustment accuracy of the transmission power is lowered as a result may occur.

  Examples of problems to be solved by the present invention include the above. An object of this invention is to provide the output control apparatus and transmitter which can adjust transmission power suitably, for example irrespective of the magnitude of transmission power.

  The above problem can be solved by an output control device that adjusts the gain of the amplifying means by detecting at least part of the output signal output from the amplifying means by the detecting means. The amplification means outputs the amplified output signal. The detection means detects at least a part of the output signal output from the amplification means. The output control device includes coupling means and changing means. The coupling unit couples at least a part of the output signal output from the amplification unit to the detection unit. That is, the coupling unit extracts at least a part of the output signal output from the amplification unit and transfers at least a part of the extracted output signal to the detection unit. The changing means changes the coupling amount of the output signal to the detection means (in other words, the coupling amount of the output signal by the coupling means) according to the power value of the output signal to be output from the amplifying means. In other words, the changing means changes the coupling amount according to the power value specified as the target value of the power value of the output signal.

  The above-described problem can be solved by a transmitter including the above-described amplification unit, the above-described detection unit, the above-described coupling unit, and the above-described changing unit.

  According to the output control apparatus described above, the amount of coupling by the coupling means changes according to the power value of the output signal. Therefore, the output control device can set a suitable coupling amount for each of cases where the power of the output signal is relatively large and relatively small. For this reason, the output control device can suitably adjust the gain of the amplification means (that is, the power of the output signal output from the amplification means) regardless of the magnitude of the power of the output signal.

  Moreover, according to the transmitter demonstrated above, the effect similar to the output control apparatus mentioned above can be enjoyed.

It is a block diagram which shows the structure of a mobile terminal. It is a graph which shows the transmission power characteristic of the coupling | bonding amount setting value which the parameter setting part with which a mobile terminal is provided. It is a graph which shows the transmission power characteristic of the detection voltage which the detector with which a mobile terminal is provided detects. It is a graph which shows the transmission power characteristic of the reference voltage value which the parameter setting part with which a mobile terminal is provided sets. A detector when the coupling amount of the directional coupler is constant without depending on the transmission power indicated by the transmission power information and when the coupling amount of the directional coupler is constant without depending on the transmission power indicated by the transmission power information It is a graph which shows the detection characteristic in

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the description is made using the mobile terminal 1 such as a mobile phone as an example of a transmitter. However, not only the mobile terminal 1, but also other various transmitters (for example, a wireless base station, a PDA or a personal computer having a communication function, and other various types) capable of transmitting a signal via a wireless line or a wired line. You may employ | adopt the structure mentioned later for a communication apparatus etc.).

  With reference to FIG. 1, the mobile terminal 1 of this embodiment is demonstrated. FIG. 1 is a block diagram showing the configuration of the mobile terminal 1.

  As shown in FIG. 1, the mobile terminal 1 includes a baseband processing unit 11, a wireless transmission unit 12, an antenna 13, a system control unit 14, an output control unit 15 as an example of an “output control device”, It has.

  The baseband processing unit 11 performs baseband processing including transmission (for example, error correction coding such as convolutional code and turbo code) processing, modulation processing such as QPSK modulation and 16QAM modulation, and the like on transmission data. . The baseband processing unit 11 outputs transmission data (transmission signal) subjected to baseband processing to the wireless transmission unit 12.

  The wireless transmission unit 12 performs wireless transmission processing on the transmission signal. The wireless transmission unit 12 includes a variable gain amplifier 121 that is an example of an “amplifying unit” and a power amplifier 122 that is an example of an “amplifying unit”. The variable gain amplifier 121 performs amplification processing for amplifying the power (transmission power) of the transmission signal in accordance with the gain determined based on the comparison calculation result in the comparator 153 described later. Variable gain amplifier 121 outputs the amplified transmission signal to power amplifier 122. The power amplifier 122 performs an amplification process for amplifying the transmission power of the transmission signal to a predetermined power value. The power amplifier 122 outputs the amplified transmission signal to the antenna 13 via a directional coupler 151 described later.

  The antenna 13 transmits a radio wave corresponding to a transmission signal output from the radio transmission unit 12 via the directional coupler 151 to a radio base station or another mobile terminal.

  The system control unit 14 controls the operation of the entire mobile terminal 1. The system control unit 14 is input with transmission power information 20 indicating the target transmission power of the transmission signal output from the wireless transmission unit 12. For this reason, the wireless transmission unit 12 described above transmits the transmission signal so that the actual transmission power of the transmission signal matches the transmission power indicated by the transmission power information 20 or the difference between the two transmission powers becomes small. It is preferable to adjust the power. The transmission power information 20 is transmitted from the radio base station or the like to the mobile terminal 1. However, when the present embodiment is applied to various transmitters other than the mobile terminal 1, the transmission power information 20 may be preset in the system control unit 14 or transmitted from other devices. May be.

  The output control unit 15 adjusts the gain of the variable gain amplifier 121 according to the output of the wireless transmission unit 12 (in other words, the output of the power amplifier 122 and the actual transmission power of the transmission signal). The output control unit 15 includes a directional coupler 151 as an example of “coupling means”, a detector 152 as an example of “detection means”, a comparator 153 as an example of “adjustment means”, and a “change means”. ”As an example.

  Details of the output control unit 15 will be described below with reference to FIGS. FIG. 2 is a graph showing transmission power characteristics of the coupling amount setting value 155 set by the parameter setting unit 154 included in the mobile terminal 1. FIG. 3 is a graph showing the transmission power characteristics of the detection voltage detected by the detector 152 included in the mobile terminal 1. FIG. 4 is a graph showing the transmission power characteristics of the reference voltage value 156 set by the parameter setting unit 154 included in the mobile terminal 1.

  The directional coupler 151 extracts a part of the transmission signal output from the wireless transmission unit 12 and outputs the extracted transmission signal to the detection unit 152. That is, the directional coupler 151 couples a part of the transmission signal output from the wireless transmission unit 12 to the detection unit 152. The amount of coupling by the directional coupler 151 (that is, the amount of transmission signal extracted by the directional coupler 151) is set by the parameter setting unit 154.

  The parameter setting unit 154 sets a coupling amount setting value indicating the coupling amount by the directional coupler 151 according to the transmission power indicated by the transmission power information 20. Specifically, the parameter setting unit 154, for example, according to the transmission power indicated by the transmission power information 20, sets one coupling amount among a plurality of coupling amount setting values 155 stored in the parameter setting unit 154. Select the value 155. The parameter setting unit 154 controls the operation of the directional coupler 151 so that the directional coupler 151 extracts the transmission signal by an amount corresponding to the coupling amount indicated by the selected one coupling amount setting value 155. That is, the parameter setting unit 154 sets the coupling amount setting value 155 so that the coupling amount by the directional coupler 151 changes according to the transmission power indicated by the transmission power information 20.

  For example, as shown in FIG. 2, the parameter setting unit 154 stores therein a plurality of coupling amount setting values 155 that change stepwise by a predetermined amount with respect to the change in transmission power indicated by the transmission power information 20. Yes. More specifically, as shown in FIG. 2, the parameter setting unit 155, for example, sets the transmission power P [dBm] to n (where n is an integer equal to or greater than 1) (for example, P0 ≦ P <P1). (Where P1 [dBm]> P0 [dBm]), P1 ≦ P <P2 (where P2 [dBm]> P1 [dBm]),..., And Pn−1 ≦ P <Pn ( However, Pn [dBm]> Pn−1 [dBm]), and n coupling amount setting values 155 respectively corresponding to the n ranges are stored. In FIG. 2, the coupling amount setting value 155 of C1 corresponds to the transmission power range P0 ≦ P <P1, and the coupling amount setting value 155 of C2 corresponds to the transmission power range P1 ≦ P <P2. Therefore, the coupling amount setting value 155 of C3 corresponds to the transmission power range of P2 ≦ P <P3, and the coupling amount setting value 155 of C4 corresponds to the transmission power range of P3 ≦ P (<P4). An example is shown. Therefore, when the transmission power P indicated by the transmission power information 20 satisfies the condition of P0 ≦ P <P1, the parameter setting unit 154 sets a plurality of coupling amount setting values 155 from “C1” to “Cn”. Of these, “C1” is selected. That is, when the transmission power P indicated by the transmission power information 20 satisfies the condition that Pk−1 ≦ P <Pk (where k is an integer that satisfies 1 ≦ k ≦ n), the parameter setting unit 154 “Ck” is selected from “C1” to “Cn”, which is a plurality of coupling amount setting values 155.

  Note that the coupling amount setting value 155 shown in FIG. 2 is an example, and a coupling amount setting value 155 that changes in another manner may be used. However, it is preferable to use a coupling amount setting value 155 such that the coupling amount setting value 155 increases as the transmission power indicated by the transmission power information 20 decreases. In other words, it is preferable to use a coupling amount setting value 155 such that the coupling amount setting value 155 decreases as the transmission power indicated by the transmission power information 20 increases.

  In addition to or instead of a plurality of coupling amount setting values 155 that change stepwise by a predetermined amount with respect to changes in transmission power, a plurality of coupling amount setting values 155 that change continuously with respect to changes in transmission power are adopted. May be. In addition to or instead of storing a plurality of coupling amount setting values 155, the coupling amount setting value 155 may be indicated by a function or expression using transmission power indicated by the transmission power information 20 as a variable. As long as the transmission power indicated by the transmission power information 20 is associated with the coupling amount setting value 155, the parameter setting unit 154 may specify the coupling amount setting value 155 in any manner.

  A part of the transmission signal extracted by the directional coupler 151 is detected by the detector 152. That is, the detector 152 detects the power of the transmission signal extracted by the directional coupler 151. When the coupling amount set value 155 changes as shown in FIG. 2, the detection characteristic in the detector 152 is the characteristic shown in FIG. As shown in FIG. 3, for each of n ranges in which the transmission power P is classified, the lower limit of a range that is not more than the upper limit V2 [V] of a range where sufficient detection accuracy is obtained and sufficient detection accuracy is obtained. A detection characteristic is obtained in which the detection voltage (that is, the output of the detector 152) gradually increases as the transmission power increases within a range of V1 [V] or more. In other words, in the transmission power range of P0 ≦ P <P1, the detection characteristic in which the detection voltage gradually increases within the range of the upper limit V2 [V] or less and the lower limit V1 [V] or more as the transmission power increases. Is obtained. Similarly, also in the transmission power range of P1 ≦ P <P2, the detection voltage gradually increases within the range of the upper limit V2 [V] and the lower limit V1 [V] as the transmission power increases. Detection characteristics are obtained. The same applies to the transmission power range of P2 ≦ P <P3 and the transmission power range of P3 ≦ P (<P4).

  The detection voltage output from the detector 152 is input to the comparator 153. The comparator 153 compares the detection voltage output from the detector 152 with the reference voltage set by the parameter setting unit 154.

  The parameter setting unit 154 sets the reference voltage according to the transmission power indicated by the transmission power information 20. Specifically, the parameter setting unit 154 selects one reference voltage 156 among the plurality of reference voltages 156 stored in the parameter setting unit 154, for example, according to the transmission power indicated by the transmission power information 20 To do. The parameter setting unit 154 outputs the selected reference voltage 156 to the comparator 153. That is, the parameter setting unit 154 sets the coupling amount setting value so that the reference voltage changes according to the transmission power indicated by the transmission power information 20.

  The plurality of reference voltages stored by the parameter setting unit 154 preferably have the same or similar characteristics as the detection characteristics in the detector 152. For example, when the detection characteristics in the detector 152 are the characteristics shown in FIG. 3, the plurality of reference voltages stored in the parameter setting unit 154 are the same as or similar to the characteristics shown in FIG. 4 (that is, the characteristics shown in FIG. 3). It is preferable that As shown in FIG. 4, the plurality of reference voltages stored in the parameter setting unit 154 has an upper limit of Vs2 [V] and a lower limit as the transmission power increases for each of n ranges in which the transmission power P is classified. It is preferable that the reference voltage 156 has a characteristic of gradually increasing within a range of Vs1 [V]. That is, the reference voltage 156 used in the transmission power range of P0 ≦ P <P1 gradually increases within the range where the upper limit becomes Vs2 [V] and the lower limit becomes Vs1 [V] as the transmission power increases. It is preferable that it has the characteristic which becomes large. The same applies to other transmission power ranges.

  The comparator 153 adjusts the gain of the variable gain amplifier 121 based on the comparison result (for example, magnitude relationship or difference) between the detection voltage and the reference voltage. For example, when the detection voltage is lower than the reference voltage, the comparator 153 increases the gain of the variable gain amplifier 121. For example, when the detection voltage is higher than the reference voltage, the comparator 153 decreases the gain of the variable gain amplifier 121. As a result, the actual transmission power of the output transmission signal from the wireless transmission unit 12 becomes desired power (for example, transmission power indicated by the transmission power information 20).

  As a comparative example for the mobile terminal 1 of the present embodiment described above, the detection characteristics in the detector 152 when the coupling amount of the directional coupler 151 is constant without depending on the transmission power indicated by the transmission power information 20. This will be described with reference to FIG. FIG. 5 shows the directional coupler 151 without depending on the coupling amount of the directional coupler 151 that is constant without depending on the transmission power indicated by the transmission power information 20 and the transmission power indicated by the transmission power information 20. It is a graph which shows the detection characteristic in the detector 152 in case the coupling | bonding amount of becomes constant.

  As shown in FIG. 5A, it is assumed that the coupling amount of the directional coupler 151 is fixed to a fixed value “C3” without depending on the transmission power indicated by the transmission power information 20. In this case, the detection characteristics in the detector 152 are the characteristics shown in FIG. As shown in FIG. 5 (b), in the transmission power range of P2 ≦ P <P3, detection is performed within a range that is lower than the upper limit V2 [V] and higher than the lower limit V1 [V] as the transmission power increases. A detection characteristic in which the voltage gradually increases can be obtained. Therefore, the detection accuracy in the detector 152 does not deteriorate in the range of transmission power P2 ≦ P <P3.

  On the other hand, in the range of transmission power of P <P2, the coupling amount is fixed, and thus the detection characteristic is shown because the absolute amount of the transmission signal coupled to the detector 152 is small. The slope of the graph becomes smaller. That is, in the range of transmission power of P <P2, the degree of change in the detection voltage with respect to the change in transmission power becomes small, and as a result, the detection accuracy decreases. On the other hand, in the transmission power range of P3 ≦ P, the detection accuracy is not lowered because the slope of the graph indicated by the detection characteristic is large. However, in the transmission power range of P3 ≦ P, since the coupling amount is fixed, it is desirable to increase the output of the power amplifier 122 (that is, increase the gain) when the transmission power is large. It is. However, an increase in the output of the power amplifier 122 leads to bringing the operating point of the power amplifier 122 closer to the saturation region, so that the distortion characteristics of the power amplifier 122 are deteriorated. Therefore, when the amount of coupling of the directional coupler 151 is constant without depending on the transmission power indicated by the transmission power information 20, the transmission power is limited only when the transmission power in a very limited range is used. Only appropriate adjustments can be made.

  However, the mobile terminal 1 of the present embodiment can adjust the coupling amount in the directional coupler 151 according to the transmission power indicated by the transmission power information 20 (that is, the transmission power specified by the radio base station 1). it can. For this reason, the mobile terminal 1 can suitably adjust the gain of the variable gain amplifier 121 regardless of the magnitude of the transmission power (in other words, regardless of the fluctuation of the transmission power). Therefore, the mobile terminal 1 can suitably adjust the transmission power of the transmission signal output from the wireless transmission unit 12 (in other words, output from the power amplifier 122).

  The mobile terminal 1 of the present embodiment defines the relationship between the coupling amount of the directional coupler 151 and the transmission power in consideration of technical problems in the comparative example. That is, the mobile terminal 1 of the present embodiment can increase the coupling amount as the transmission power decreases. Therefore, when the transmission power is relatively small, the slope of the graph indicated by the detection characteristics is not reduced, and therefore the deterioration in detection accuracy is suppressed. Similarly, the mobile terminal 1 of the present embodiment can reduce the coupling amount as the transmission power increases. Therefore, when the transmission power is relatively large, the loss in the main signal sequence due to the coupling in the directional coupler 151 is reduced, and therefore the output of the power amplifier 122 is not increased more than necessary. For this reason, the distortion characteristic of the power amplifier 122 does not deteriorate. As described above, the mobile terminal 1 of the present embodiment can suitably adjust the transmission power of the transmission signal regardless of the range of the transmission power.

  The mobile terminal 1 according to the present embodiment can also change the reference voltage referred to by the comparator 153 according to the coupling amount in the directional coupler 151. Therefore, the comparator 153 is. Even if the coupling amount is changed, an appropriate comparison between the detection voltage and the reference voltage can be performed. Therefore, the mobile terminal 1 can suitably adjust the transmission power of the transmission signal.

  Regarding the embodiment described above, the following additional notes are disclosed.

(Appendix 1)
An output control device that adjusts the gain of the amplifying means by detecting at least a part of the output signal output from the amplifying means by the detecting means, and at least a part of the output signal to the detecting means An output control apparatus comprising: coupling means for coupling; and changing means for changing a coupling amount of the coupling means in accordance with a power value of the output signal to be output from the amplification means.

(Appendix 2)
The output control apparatus according to appendix 1, wherein the changing unit changes the coupling amount so that the coupling amount increases as the power value decreases.

(Appendix 3)
(I) when the power value is a first value or included in a first range, the changing means sets the coupling amount to a first set amount; and (ii) the power value is a first value. When the second value is smaller than the first value or included in the second range smaller than the first range, the coupling amount is set to a second set amount larger than the first set amount. The output control apparatus according to appendix 1 or 2.

(Appendix 4)
The output control device according to any one of appendices 1 to 3, wherein the changing unit changes the coupling amount so that the coupling amount decreases as the power value increases.

(Appendix 5)
(I) when the power value is a first value or included in a first range, the changing means sets the coupling amount to a first set amount; and (ii) the power value is a first value. When the third value is larger than the first value or included in the third range larger than the first range, the coupling amount is set to a third set amount smaller than the first set amount. The output control device according to any one of appendices 1 to 4.

(Appendix 6)
The output control device according to any one of appendices 1 to 5, wherein the changing unit changes the coupling amount step by step by a predetermined amount or continuously by a predetermined ratio.

(Appendix 7)
The adjusting unit further includes an adjusting unit that adjusts a gain of the amplifying unit based on a comparison result between the detection voltage detected by the detecting unit and a predetermined reference voltage, and the changing unit includes the reference voltage according to the power value. The output control device according to any one of appendices 1 to 6, wherein the output control device is changed.

(Appendix 8)
The output control device according to appendix 7, wherein the changing unit changes the reference voltage in accordance with the power value so as to match a detection characteristic of the detection unit.

(Appendix 9)
Amplifying means for outputting an output signal; detecting means for detecting at least part of the output signal output from the amplifying means; and coupling means for coupling at least part of the output signal to the detecting means; A transmitter comprising: changing means for changing a coupling amount of the coupling means in accordance with a power value of the output signal to be output from the amplification means.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification. The transmitter is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Cellular phone 11 Baseband process part 12 Wireless transmission part 121 Variable gain amplifier 122 Power amplifier 13 Antenna 14 System control part 15 Output control part 151 Directional coupler 152 Detector 153 Comparator 154 Parameter setting part 155 Coupling amount setting value 156 Reference voltage value 20 Transmission power information

Claims (4)

An output control device that adjusts the gain of the amplifying means by detecting at least part of the output signal output from the amplifying means by the detecting means,
Coupling means for coupling at least part of the output signal to the detection means;
An output control apparatus comprising: a changing unit configured to change a coupling amount of the coupling unit according to a power value of the output signal to be output from the amplifying unit.   (I) when the power value is a first value or included in a first range, the changing means sets the coupling amount to a first set amount; and (ii) the power value is a first value. When the second value is smaller than the first value or included in the second range smaller than the first range, the coupling amount is set to a second set amount larger than the first set amount. The output control apparatus according to claim 1.   (I) when the power value is a first value or included in a first range, the changing means sets the coupling amount to a first set amount; and (ii) the power value is a first value. When the third value is larger than the first value or included in the third range larger than the first range, the coupling amount is set to a third set amount smaller than the first set amount. The output control apparatus according to claim 1 or 2. Amplifying means for outputting an output signal;
Detection means for detecting at least a part of the output signal output from the amplification means;
Coupling means for coupling at least part of the output signal to the detection means;
A transmitter comprising: changing means for changing a coupling amount of the coupling means in accordance with power of the output signal to be output from the amplification means.

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