JP2010103791A - Transmitter and portable information terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter capable of dynamically correcting a DC offset even in a UMTS which continues transmission, etc. <P>SOLUTION: Two or more quadrature modulators are arranged in the transmitter, and the transmission is performed by switching the quadrature modulators by every transmission slot. Since a specific quadrature modulator is not used in two or more continuous transmission slots, the specific quadrature modulator becomes an object for DC offset calibration during a period when it does not take charge of the transmission, and a DC offset control circuit 129 executes calibration of the DC offset to the object for DC offset calibration. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to carrier leak correction of a UMTS transmitter, particularly, a quadrature modulator during continuous transmission.

  In the UMTS (Universal Mobile Telecommunication Systems) transmission system, direct up-conversion is employed. Therefore, when implementing a UMTS transmission system, high carrier leak suppression (−40 dBc) is required.

  As a cause of occurrence of carrier leak, a DC offset between the I signal and the Q signal can be considered. Therefore, it is desirable to continue adjusting the I and Q signals in the transmitter modulation circuit as much as possible.

In Japanese Patent Laid-Open No. 2006-41631 (Patent Document 1), the control unit adds a test pattern corresponding to a correction value in a state where the I signal and the Q signal are not present and the carrier frequency is constant, It is described that the control unit detects the output after signal synthesis to correct the DC offset.
JP 2006-41631 A

  However, unlike the TDMA (Time Division Multiple Access) method, the CDMA (Code Division Multiple Access) method adopted by UMTS has no transmitter pause until the end of data transmission once it is started. For this reason, once the transmission state is entered, the gain (gain) for each slot (there are 15 slots in one frame (10 msec)) can be changed, but the time for correcting (calibrating) the carrier leak cannot be secured. There was a problem.

  The same applies to the technique described in Patent Document 1, and there is a premise that “the I signal and the Q signal are not present”, and it is practically difficult to apply to a UMTS transmission system in which there is no pause of the transmitter during a call (transmission). It is.

  Further, when the gain is varied by the variable gain low noise amplifier circuit at the output stage of the quadrature modulator, the carrier leak is determined at the quadrature modulator output terminal. Therefore, when the gain of the variable gain low noise amplifier circuit is changed, the ratio between the carrier leak and the desired transmission signal is kept. On the other hand, when temperature fluctuations and power supply voltage fluctuations occur during a long-term call or the like, the actual state of carrier leakage cannot be correctly reflected and carrier leakage may be deteriorated.

  Further, when the quadrature modulator and the RF gain variable circuit are configured by the CMOS, the inventor considers that it may be preferable to switch between two or more quadrature modulators having different gains.

  An object of the present invention is to provide a transmitter capable of dynamically correcting a DC offset even in UMTS or the like that continuously performs transmission.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  A transmitter according to a representative embodiment of the present invention includes two or more quadrature modulators having different gains, and a control unit that selects one quadrature modulator to be used for transmission from the two or more quadrature modulators. A transmitter that continuously transmits a transmission frame composed of a plurality of transmission slots during data transmission, wherein the control unit switches between two or more orthogonal modulators for each transmission slot and uses them for transmission. And

  This transmitter may be characterized in that the gains of the two or more quadrature modulators are distributed at equal intervals.

  The transmitter further includes two or more variable amplifiers. Each of the two or more variable amplifiers has a variable width that is twice the gain distribution interval of the two or more quadrature modulators. Two or more variable amplifiers may be switched, and settings of two or more variable amplifiers may be updated.

  This transmitter further includes a DC offset control circuit, and the control unit selects one of the quadrature modulators not used for data transmission as a DC offset calibration target, and sets dummy data as the DC offset calibration target. The output of the DC offset calibration target may be input to the DC offset control circuit, and the DC offset control circuit may perform calibration of the DC offset calibration target.

  In this transmitter, when the quadrature modulator is switched for each transmission slot, the control unit may select the DC offset calibration target of the transmission slot that has just ended for transmission.

  The transmitter may be characterized in that selection of a DC offset calibration target and setting of the variable amplifier are determined based on a transmission gain of a next transmission slot.

  The transmitter according to the representative embodiment of the present invention selects two or more variable quadrature modulators having different variable gains and one variable quadrature modulator to be used from the two or more variable quadrature modulators. A transmitter that continuously transmits a transmission frame including a plurality of transmission slots during data transmission, and the controller switches two or more variable quadrature modulators in units of transmission slots for transmission. It is characterized by using.

  In this transmitter, the control unit may select one variable quadrature modulator to be used from the two or more variable quadrature modulators based on the transmission gain of the transmission slot.

  The present invention also includes a portable information terminal using the transmitter.

  The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

  If the transmitter according to the representative embodiment of the present invention is used, the calibration (correction) of the DC offset can be performed without interrupting the transmission or the transmission frame by alternately using two or more quadrature modulation circuits. Can be done.

  Further, by using two or more quadrature modulation circuits and shifting the gain of the quadrature modulator, it is possible to reduce the variable amount of the subsequent stage variable amplifier.

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
Hereinafter, a basic embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing where a carrier leak calibration mechanism according to the present invention is located in a transceiver. Since this figure is for explaining the internal block, the signal is not described separately for the I component and the Q component.

  This transceiver includes an antenna 101, a duplexer 102, oscillators 103, 103R, BPF 111, LNA 112, a mixer circuit 113, an amplifier 114, a BPF 115, an AD converter 116, a DA converter 121, an attenuator 122, an LPF 123, a DAC 124, a mixer circuit 125, and an amplifier 126. , SAW127, HPA128, DC offset control circuit 129, and 90 degree phase shifters 131 and 131R.

  The duplexer 102 is a duplexer for the transmitter and the receiver to share the antenna 101.

  The oscillators 103 and 103R are LO (local) oscillators for performing conversion from a carrier frequency to a baseband frequency and vice versa. 103R on the receiver side and 103 on the transmitter side. It is assumed that the wavelengths output from the oscillators 103 and 103R have been divided by a PLL or the like.

  A BPF (band pass filter) 111 is a filter circuit for extracting a frequency of a certain band from a received wave received via the antenna 101. In order not to amplify unnecessary frequency components by the LNA 112, it is used before the LNA 112.

  The LNA (low noise amplifier) 112 is an amplifier for amplifying a signal having only a necessary frequency band by the BPF 111 to facilitate handling.

  The mixer circuit 113 is a mixer circuit that multiplies the signal amplified by the LNA 112 and the output of the oscillator 103. Since it is necessary to reduce the frequency from the carrier frequency to the baseband frequency at the time of reception, the mixer circuit 113 includes a low-pass filter in the subsequent stage.

  The amplifier 114 is an amplifier for amplifying the baseband signal obtained by the mixer circuit 113. A BPF (band pass filter) 115 is a filter for removing unnecessary frequency components from the signal amplified by the amplifier 114.

  The AD converter 116 is an analog-to-digital conversion circuit for converting the obtained noise-free baseband signal (analog signal) into a digital signal.

  The DA converter 121 is a digital-analog conversion circuit that converts sent digital data into the original analog data for transmission.

  The attenuator 122 is an attenuator that once attenuates the analog data (baseband frequency) converted by the DA converter 121.

  The LPF (low-pass filter) 123 is a filter for removing harmonic components of analog data attenuated by the attenuator.

  The DAC 124 is a digital-analog conversion circuit that applies an offset DC bias to analog data after passing through the LPF 123, specifically, an I component and a Q component. At this time, the amount of the offset DC bias is determined based on the output of the DC offset control circuit 129.

  The mixer circuit 125 is a mixer circuit for up-converting from a baseband frequency to a carrier frequency. Actually, the I and Q components are up-converted, and the up-converted I and Q components are synthesized. However, due to the nature of the drawing that it is not described separately for the I component and Q component, circuits such as an adder do not appear in this figure.

  The amplifier 126 is an amplifier for amplifying the output of the mixer circuit 125.

  A SAW 127 is a SAW filter for cutting noise from the output of the amplifier 126.

  The HPA (high power amplifier) 128 is a high power amplifier that amplifies the output of the SAW 127 to output it from the antenna 101 to the wireless section.

  The DC offset control circuit 129 is a circuit for detecting a DC offset amount that amplifies the output of the mixer circuit 125 and checks the deviation of the direct current components of the I component and the Q component. A limiter circuit or the like is often used for the DC offset control circuit 129.

  The 90-degree phase shifter 131 is a circuit that generates the output of the oscillator 103 that is shifted by a quarter wavelength, supplies the output that is not shifted to the I component or the Q component, and supplies the output that is shifted by a quarter wavelength to the other. . The 90 degree phase shifter 131R is in charge of the receiver side, and the 90 degree phase shifter 131 is in charge of the transmitter side.

  The attenuator 122, LPF 123, DAC 124, and mixer circuit 125 are the quadrature modulator 130. As can be seen from the above description, the purpose of the quadrature modulator 130 is to up-convert the baseband signal component to the carrier frequency (RF band).

  The present invention mainly relates to the configuration of the DAC 124, the mixer circuit 125, and the amplifier 126, and the handling of these and the DC offset control circuit 129.

  Next, the configuration of a circuit around the conventional mixer circuit 125 will be described.

  FIG. 2 is a block diagram showing a circuit configuration around the conventional quadrature modulator 130. In this figure, the I component and the Q component are shown separately. Accordingly, mixers 125 -I and 125 -Q and an adder 125 -A not shown in FIG. 1 are described.

  The mixers 125 -I and 125 -Q are elements of the mixer circuit 125. This mixer multiplies the signal supplied from the 90-degree phase shifter 131 and the baseband signal supplied from the DACs 124-I and 124-Q, and upconverts the carrier frequency.

  The adder 125 -A is one element of the mixer circuit 125. This is an adder that combines up-converted I-component and Q-component baseband signals and renders them in a transportable state.

  The I component of the baseband signal becomes an I component signal of the carrier frequency through the attenuator 122 -I, LPF 123 -I, DAC 124 -I, and mixer 125 -I. On the other hand, the Q component of the baseband signal passes through the attenuator 122-Q, LPF 123-Q, DAC 124-Q, and mixer 125-Q, and becomes the Q component signal of the carrier frequency. The adder 125-A adds these I component and Q component signals to form an RF signal. The RF signal is appropriately amplified by the amplifier 126 depending on the type of output (for example, communication based on the GSM system or communication based on the UMTS system).

  Under ideal conditions, the I and Q components are orthogonal in a complex function and do not affect each other. However, in reality, carrier leaks are generated at the output of the quadrature modulator 130 due to variations in pairs of elements of the attenuator 122, the LPF 123, and the DAC 124 that receive the baseband and local leaks due to parasitic imbalance.

  As a countermeasure, calibration is performed by the DC offset control circuit 129 and the DACs 124-I and 124-Q in the conventional example. However, in the conventional method, once data transmission is started, calibration cannot be performed midway. Therefore, it cannot follow the temperature fluctuation and power supply fluctuation that occur after the transmission starts.

  FIG. 3 is a block diagram showing a circuit configuration around the quadrature modulator according to the present embodiment.

  In the basic embodiment of the present invention, the presence of the two systems of quadrature modulators 151 and 152, the presence of the baseband side changeover switch 155 and the RF side changeover switch 156, and the control unit 153 performs these controls. What is different from the conventional example is that the DC offset control circuit 154 is controlled by the control unit 153.

  For simplification of the drawing, the same item numbers as those in FIG. 2 are omitted. Since the internal configurations of the quadrature modulators 151 and 152 are the same as those of the quadrature modulator 130, the item numbers of the internal elements are also omitted.

  The control unit 153 is a control circuit that controls switching of the quadrature modulators 151 and 152, the DC offset control circuit 154, the baseband side changeover switch 155, and the RF side changeover switch 156.

  The quadrature modulators 151 and 152 are quadrature modulators composed of the same components. In this embodiment, two quadrature modulators are prepared and switched for each time slot of a physical channel (for example, DPCH in UMTS). This switching is performed by the control unit 153.

  Similar to the DC offset control circuit 129 of FIG. 2, the DC offset control circuit 154 is a circuit for detecting the DC offset amount by amplifying the output of the mixer 124 and checking the deviation of the DC components of the I component and the Q component. Here, in the present embodiment, there are two detection targets, quadrature modulators 151 and 152. The DC offset control circuit 154 detects the DC offset amount of the quadrature modulator that is not currently used. Also, calibration is performed on the quadrature modulator that is currently detected.

  The baseband side changeover switch 155 is a switch that determines which of the orthogonal modulators 151 and 152 inputs the baseband signal. That is, it is necessary to switch the baseband side switch 155 in order to switch the quadrature modulator to be operated.

  The RF side changeover switch 156 is a switch that determines which of the orthogonal modulators outputs the RF signal. Further, switching is performed so that the output of the quadrature modulator that is not used is output to the DC offset control circuit 154.

  It is necessary to input dummy data for checking the offset amount to the quadrature modulator to be calibrated (= the quadrature modulator not used for transmission at that time) at the time of calibration of the DC offset. Although it is conceivable to input dummy data by inputting only the LO transmission of the I component and Q component, other systems may be used by providing a separate circuit.

  Next, switching timing of the control unit 153 according to the present embodiment will be described. Here, a case where this embodiment is applied to a UMTS transmitter and a mobile phone including the UMTS transmitter will be described.

  FIG. 4 is a diagram for explaining calibration timing of a conventional UMTS transmitter.

  When communicating with a mobile phone, a band is selected before transmission / reception. Since the frequency to be locked can be limited when the band is determined, the transmission frequency is locked. In the present embodiment, this means that the output of the oscillator 103 is fixed. Then, after the frequency is determined, the transmitter is operated.

  In the conventional method of FIG. 4, after the frequency is determined, the DC offset control circuit 129 measures the amount of DC offset. Then, a calibration value is derived before transmission, and an offset DC bias is set for the DAC 124 -I and DAC 124 -Q of the quadrature modulator 130.

  However, since the LO oscillation from the oscillator 103 is used to measure the amount of DC offset, there is a problem that once the transmission / reception is started, the offset DC bias cannot be reset.

  On the other hand, FIG. 5 is a diagram for explaining the timing of calibration of the UMTS transmitter according to the first embodiment of the present invention.

  In the system of the present invention, the control unit 153 switches between the quadrature modulator 151 and the quadrature modulator 152 for each slot. In UMTS, one frame is defined as 10 msec. Since there are 15 slots in one frame, the control unit 153 switches the baseband side changeover switch 155 and the RF side changeover switch 156 about every 667 μsec.

  Then, the DC offset control circuit 154 sets a quadrature modulator that is not used at that time as a calibration target. Then, the amount of DC offset to be calibrated is measured, and the DAC 124-I and DAC 124-Q of the calibration target quadrature modulator are set.

  Thereafter, when the transmission slot is switched, transmission is performed using the quadrature modulator immediately after the calibration is performed.

  By controlling in this way, it becomes possible to perform DC offset calibration in one slot cycle (about 667 μsec). As a result, the transmission quality of the transmitter is not deteriorated even during a long-time call.

  In the present embodiment, two quadrature modulators are prepared. However, even if the number of quadrature modulators is three or more, the present invention can be realized without any problem (the circuit configuration of the baseband side changeover switch 155 and the RF side changeover switch 156, and those. The operation related to is complicated). Further, although the switching timing of the quadrature modulator is switched for each slot, it may be switched on a frame basis.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  This embodiment is a description specific to the UMTS system. However, if it corresponds to the actual situation of each communication method, it can be easily implemented in other methods.

  In the UMTS system, it is required to perform transmission output control so that transmission power reaching a base station is constant between terminals. This is to prevent the signal of the own terminal from being buried in the signal from the other terminal and preventing the signal of the other terminal from being buried in the signal from the own terminal.

  Naturally, as long as this specification is followed, the mobile terminal must be able to control the transmission power. In 3GPP TS (Technical Specification) 25.101, output gain (gain) adjustment of a transmission power of 74 dB in total is required, ie, a minimum of −50 dB and a maximum of 24 dB.

  FIG. 6 is a conceptual diagram of the operation in the present embodiment.

  As can be seen from this figure, the present embodiment covers the width of 74 dB with eight variable quadrature modulators. For this reason, eight variable quadrature modulators having an output width of 10 dB are prepared. It is assumed that the variable quadrature modulator to be used is switched according to the transmission output.

  In FIG. 6, the output gain is covered by the following correspondence.

Variable quadrature modulator 1: -50 dB to -40 dB
Variable quadrature modulator 2: -40 dB to -30 dB
Variable quadrature modulator 3: -30 dB to -20 dB
Variable quadrature modulator 4: -20 dB to -10 dB
Variable quadrature modulator 5: -10 dB to 0 dB
Variable quadrature modulator 6: 0 dB to 10 dB
Variable quadrature modulator 7: 10 dB to 20 dB
Variable quadrature modulator 8: 20 dB or more The transmission power control bit in UMTS is transmitted from the base station in the form of a decibel reduction or increase relative to the current output gain. The transmitter determines how many dB of output gain is required after calculating a correction value of the gain specified by the current output and the transmission power control bit.

  Thereafter, an output assumed to correspond to the output gain of the variable quadrature modulator is compared to determine a variable quadrature modulator to be used. It also determines how much the output gain of the variable quadrature modulator is to be increased.

  At this time, in the case of # 1 in FIG. 6, since the same variable quadrature modulator (variable quadrature modulator 4) is continuously used, calibration of the DC offset cannot be executed. However, in the case of # 2 in FIG. 6, a different variable quadrature modulator is used by shifting from the variable quadrature modulator 4 to the variable quadrature modulator 3. At this time, calibration of the DC offset of the variable quadrature modulator to be used next is executed immediately before changing the variable quadrature modulator.

  FIG. 7 is a block diagram showing a circuit configuration around the quadrature modulator according to the present embodiment. As described above, eight variable quadrature modulators are prepared in this embodiment. Correspondingly, the number of switching targets of the baseband side switch 171 and the RF side switch 172 increases from two to eight. Along with this, the operations of the control unit 159 and the DC offset control circuit 160 also change.

  The variable quadrature modulators 1 to 8 are quadrature modulators whose output gain can be varied by 10 dB. Similar to the quadrature modulators 151 and 152 of the first embodiment, the DC offset calibration is possible.

  The baseband side changeover switch 171 is a switch for determining which variable quadrature modulator 1 to 8 the baseband signal is input to.

  The RF side changeover switch 172 is a switch for transmitting the output of the variable quadrature modulator to which the baseband signal is input to the amplifier 126. In the first embodiment, the RF side changeover switch 156 outputs the output of the unused quadrature modulator to the DC offset control circuit 154. In the present embodiment, according to the determination by the control unit 159, the RF side of the first embodiment is switched in that the output of the variable quadrature modulator to be calibrated for DC offset is input to the DC offset control circuit 154. This is different from the changeover switch 156.

  Unlike the control unit 153 of the first embodiment, the control unit 159 is a variable quadrature modulator that is a DC offset calibration target for the baseband switch 171, the RF switch 172, and the DC offset control circuit 160. Instruct.

  Unlike the DC offset control circuit 154 of the first embodiment, the DC offset control circuit 160 of this embodiment increases the number of transmission destinations to eight. Along with this, a destination instruction is received from the control unit 159.

  As described above, the transmission power control bit (or the increase / decrease value of the output gain after interpreting the contents) is input to the control unit 159 from outside the transmitter. After that, the control unit 159 determines the output gain of the next transmission slot with reference to these. After the output gain of the next transmission slot is determined, if the variable quadrature modulator is changed from the currently used one, dummy data is stored after connecting the variable quadrature modulator to be used next and the DC offset control circuit 160. Next, it inputs into the variable orthogonal modulator to be used. Next, the output from the variable quadrature modulator to be used is input to the DC offset control circuit 160. Thereafter, the DC offset control circuit 160 adjusts the variable quadrature modulator that has received an instruction from the control unit 159, that is, the variable quadrature modulator that has received the input of dummy data. The DC offset control circuit 160 confirms the distortion of the output of the variable quadrature modulator based on the dummy data input to the variable quadrature modulator. As a result, it can be seen how much adjustment is required for the corresponding variable quadrature modulator. The DC offset control circuit 160 sets this necessary adjustment amount for the DACs 124 -I and 124 -Q (or adjustment points corresponding thereto) of the variable quadrature modulator to be calibrated.

  At the time of switching the transmission slot, the control unit 159 switches to a quadrature modulator that has performed DC offset calibration as a quadrature modulator for transmission. This makes it possible to perform DC offset calibration each time the variable quadrature modulator is changed.

  If the present embodiment is provided in this way, it is expected that the DC offset calibration is executed at a certain period. As a result, it is possible to provide a transmitter that can dynamically correct a DC offset even in UMTS or the like that continuously performs transmission, which is an object of the present invention.

(Third embodiment)
Next, a third embodiment will be described.

  FIG. 8 is a conceptual diagram of the operation in the present embodiment. FIG. 9 is a block diagram showing a circuit configuration around the quadrature modulator according to the present embodiment.

  In the second embodiment, eight variable quadrature modulators are prepared, and the process of selectively using the variable quadrature modulators is performed according to the expected output gain. When the output gain changes to some extent, this method can be expected to execute DC offset calibration at a certain period. On the other hand, the second embodiment does not guarantee that the DC offset calibration is performed with 100% certainty.

  The object of the present embodiment is to calibrate the DC offset reliably for each slot.

  That is, as in the second embodiment, eight quadrature modulators having different output gains are prepared. At this time, the quadrature modulator is fixed at the output without adjusting the output gain. One feature of the present embodiment is that a rough gain is set by determining the quadrature modulator, and a final output gain is determined using a variable amplifier located at the subsequent stage of the quadrature modulator.

  This embodiment has another feature. That is, the adjustment width of the output gain of the variable amplifier can be varied by a width twice as large as the output gain arrangement interval of the orthogonal modulator. Thus, the second feature is that even when transmission with the same output gain continues, the quadrature modulator can be switched.

  This will be described with reference to FIG.

  In this figure, it is assumed that the output gain is changed from (1) to (2). In the second embodiment, the DC offset calibration can be executed only when the variable quadrature modulator is switched by changing the output gain.

On the other hand, by combining a quadrature modulator and a variable amplifier,
Quadrature modulator 166 + variable amplifier
Transmission is possible by any combination of the quadrature modulator 165 and the variable amplifier. This is because the adjustment range of the output gain of the variable amplifier is variable by a width that is twice the arrangement interval of the output gains of the quadrature modulator.

  Therefore, the DC offset calibration of the unused quadrature modulator is performed, and the DC offset calibration can be continuously performed even when transmission is continued with substantially the same output gain by switching periodically. It is something that can be done.

  Next, the configuration of the circuit will be described with reference to FIG.

  In the present embodiment, unlike the second embodiment, quadrature modulators 161 to 168 are used instead of the variable quadrature modulators 1 to 8. Another difference is that two variable amplifiers (173, 174) are prepared instead of one amplifier 126 following the quadrature modulator. Further, the control unit becomes the control unit 169 as the number of controlled objects increases.

  As described above, the quadrature modulators 161 to 168 are quadrature modulators having different output gains in units of 10 dB. Of the eight quadrature modulators, one is actually used for transmission at the same time as the variable quadrature modulator of the second embodiment. Further, only one of the seven quadrature modulators other than the one used for transmission is controlled by the DC offset control circuit 175. In this figure, the gains of the quadrature modulators 161 to 168 are as follows.

Quadrature modulator 161: 0 dB
Quadrature modulator 162: -10 dB
Quadrature modulator 163: -20 dB
Quadrature modulator 164: -30 dB
Quadrature modulator 165: -40 dB
Quadrature modulator 166: -50 dB
Quadrature modulator 167: -60 dB
Quadrature modulator 168: -70 dB
Since the basic configuration is the same as that of the first embodiment, description of the internal configuration is omitted.

  The variable amplifiers 173 and 174 correspond to the amplifier 126 of the first embodiment. Unlike the quadrature modulator, the variable amplifiers 173 and 174 have the same specifications, but have a peripheral circuit capable of changing the amplification factor and switching the variable amplifier to be used according to an instruction from the control unit 169. To do. The variable widths of the variable amplifiers 173 and 174 are assumed to be 20 dB from 24 dB to 4 dB, which is twice the output gain interval of the quadrature modulators 161 to 168.

  In addition to the second embodiment, the control unit 169 switches the variable amplifiers 173 and 174 and sets the amplification factor.

  Next, the control of this embodiment will be described with reference to FIG. FIG. 10 is a diagram showing a specific usage of the quadrature modulator and the variable amplifier.

  Also in this embodiment, the mobile phone performs DC offset calibration before transmission after a frequency lock period in which power-on, band selection, and frequency lock are attempted, and transmission of a frame for transmitting voice and data is started. Hereinafter, in this figure, the downward arrow means execution of calibration of the target quadrature modulator.

  In FIG. 10, only the operation of the quadrature modulator and the variable amplifier in the first frame is described, but the same operation is performed in the second and subsequent frames.

(Operation before frame 1 slot 0)
First, assume that the output gain expected in frame 1 slot 0 is −48 dB. Toward this end, before starting transmission (= before frame 1 slot 0), the control unit 169 sets the quadrature modulator 168 (−70 dB) as the operation target of frame 1 slot 0, and sets the variable amplifier 173 to +22 dB. is doing.

  Prior to the operation in frame 1 slot 0, the DC offset calibration with the above settings is performed before transmission in slot 0.

(Operation in frame 1 slot 0)
The transmitter executes transmission of frame 1 slot 0 under the above setting conditions.

  During the transmission period, the mobile phone derives a transmission output gain from a base station (not shown) by a transmission power control bit. In the transmission power control bit, an instruction is given to raise (decrease) a relative dB. After finishing the analysis of the transmission power control bit on the receiving side, the control unit 169 determines the output gain expected in the frame 1 slot 1.

  During frame 1 slot 0, control unit 169 determines the expected value of the transmission output gain in frame 1 slot 1 after the requested adjustment. Based on the determined value, the control unit 169 determines a quadrature modulator to be moved to the next slot (= frame 1 slot 1). At this time, the currently used quadrature modulator cannot adjust the DC offset, so it is not used in the frame 1 slot 1.

  In FIG. 10, an output gain of −47 dB is assumed in frame 1 slot 1. Based on this, during the frame 1 slot 0 period, the control unit 169 determines which quadrature modulator is used in the frame 1 slot 1.

  In order to realize an output gain of −47 dB, use of a quadrature modulator 166 (−50 dB), a quadrature modulator 167 (−60 dB), and a quadrature modulator 168 (−70 dB) can be considered. Of these, the quadrature modulator 168 is excluded from use in the frame 1 slot 1 because it is used in the frame 1 slot 0. Further, since the variable amplifier 174 in the subsequent stage cannot take +2 dB, the quadrature modulator 166 is excluded. Therefore, the control unit 169 uses the quadrature modulator 167 in the frame 1 slot 1. Hereinafter, the quadrature modulator that cannot obtain the desired output gain by changing the variable amplifier will not be described as a selection target in principle, but the control unit 169 will select the selection target in an internal process and then exclude it from the bottom. It may be done.

  Accordingly, the control unit 169 sets the variable amplifier 174 to +13 dB.

  After completing the selection / setting, the control unit 169 causes the DC offset control circuit 175 to perform DC offset calibration of the quadrature modulator 167. This can be done by checking how much DC offset occurs in the output of the quadrature modulator 167 due to the input of dummy data. Specifically, the output of the quadrature modulator 167 that has received the input of dummy data is input to the DC offset control circuit 175. In accordance with this input result, the DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 167 to execute DC offset calibration even during the transmission operation.

  At the timing of moving from frame 1 slot 0 to frame 1 slot 1, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 167 and the variable amplifier to the variable amplifier 174. The switch 172 is controlled.

(Operation in frame 1 slot 1)
After switching the baseband side changeover switch 171 and the RF side changeover switch 172, the control unit 169 derives the output gain in the frame 1 slot 2. In FIG. 10, it is assumed that the output gain in frame 1 slot 2 is −46 dB.

  Similar to frame 1 slot 1, in frame 1 slot 2, a quadrature modulator 166 (-50 dB), a quadrature modulator 167 (-60 dB), and a quadrature modulator 168 (-70 dB) can be considered. However, since the quadrature modulator 167 is in use in the frame 1 slot 1, it is excluded from being used in the frame 1 slot 2.

  Unlike the selection of the quadrature modulator to be used in the frame 1 slot 1, the frame 1 slot 2 (−46 dB) can be realized by either the quadrature modulator 166 (−50 dB) or the quadrature modulator 168 (−70 dB). it can. This is because the variable amplifier 173 may be set to +4 dB when the quadrature modulator 166 is used, and the variable amplifier 173 may be set to +24 dB when the quadrature modulator 168 is used. Which one to select is a design matter of the control unit 169, but here it is assumed that the quadrature modulator 166 is used in the frame 1 slot 2. It should be noted here that a higher gain of the quadrature modulator is advantageous in terms of signal / noise ratio.

  If the quadrature modulator to be used is determined, the value set in the variable amplifier 173 used in frame 1 slot 2 is +4 dB. The control unit 169 performs this setting for the variable amplifier 173. After this setting, the control unit 169 causes the DC offset control circuit 175 to perform DC offset calibration for the quadrature modulator 166. The DC offset control circuit 175 performs adjustment on the DACs 124 -I and 124 -Q of the quadrature modulator 166.

  At the timing of moving from frame 1 slot 1 to frame 1 slot 2, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 166 and the variable amplifier to the variable amplifier 173. The switch 172 is controlled.

(Operation in frame 1 slot 2)
In frame 1 slot 2, data is transmitted by a combination of quadrature modulator 166 and variable amplifier 173. During this transmission period, the control unit 169 sets the quadrature modulator and variable amplifier 174 used in the frame 1 slot 3 as before.

  After the transmission power bit analysis result is sent, the control unit 169 determines the output gain of the transmitter. In FIG. 10, the assumed output gain in frame 1 slot 3 is −46 dB, which is the same as that in frame 1 slot 2. However, since the DC offset calibration cannot be performed by the quadrature modulator 166 used in the frame 1 slot 2, it is necessary to select another quadrature modulator. As described above, it is determined whether the output gain assumed by the combination of the gain of the quadrature modulator and the gain of the variable amplifier can be realized. In this figure, the control unit 169 selects the quadrature modulator 167 for the frame 1 slot 3.

  When the quadrature modulator to be used is determined, the gain of the variable amplifier 174 used in the frame 1 slot 3 is also determined. Here, the gain of the variable amplifier 174 is determined to be +14 dB.

  After determining the setting of the quadrature modulator and variable amplifier 174, the control unit 169 causes the DC offset control circuit 175 to perform calibration of the DC offset of the quadrature modulator 167. The DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 167 to prepare for execution of transmission of the frame 1 slot 3.

  At the timing of moving from frame 1 slot 2 to frame 1 slot 3, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 167 and the variable amplifier to the variable amplifier 174. The switch 172 is controlled.

(Operation in frame 1 slot 3)
In frame 1 slot 3, data is transmitted by a combination of quadrature modulator 167 and variable amplifier 174. During this transmission period, the control unit 169 sets the quadrature modulator and variable amplifier 173 used in the frame 1 slot 4.

  After the transmission power bit analysis result is sent, the control unit 169 determines the output gain of the transmitter. In FIG. 10, the assumed output gain of the transmitter in frame 1 slot 4 is −45 dB. To realize -45 dB, a quadrature modulator 167 (-60 dB), a quadrature modulator 166 (-50 dB), and a quadrature modulator 165 (-40 dB) not shown in FIG. Of these, if the quadrature modulator 167 that is currently in use and cannot be calibrated for DC offset is excluded, the use of the quadrature modulator 166 and the quadrature modulator 165 is considered. Here, it is assumed that the control unit 169 has selected the quadrature modulator 166 (−50 dB).

  If the quadrature modulator is determined, the setting contents of the variable amplifier 173 are also determined naturally. The control unit 169 sets +5 dB for the variable amplifier 173.

  After this setting, the control unit 169 performs DC offset calibration of the quadrature modulator 166. After the calibration is performed, the DACs 124 -I and 124 -Q of the quadrature modulator 166 are adjusted to prepare for the transmission of the frame 1 slot 3.

  At the timing of shifting from frame 1 slot 3 to frame 1 slot 4, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 166 and the variable amplifier to the variable amplifier 173. The switch 172 is controlled.

(Operation in frame 1 slot 4)
In frame 1 slot 4, data is transmitted by a combination of quadrature modulator 166 and variable amplifier 173. The control unit 169 sets the quadrature modulator and variable amplifier 174 used in the frame 1 slot 5.

  After the transmission power bit analysis result is sent, the control unit 169 determines the output gain of the transmitter. In FIG. 10, the assumed output gain in frame 1 slot 5 is −45 dB as in frame 1 slot 4. In this output gain condition, as described above, the quadrature modulator 167 (−60 dB), the quadrature modulator 166 (−50 dB), and the quadrature modulator 165 (−40 dB) can be considered. If the quadrature modulator 166 in use is excluded, the use of the quadrature modulator 167 (−60 dB) and the quadrature modulator 165 (−40 dB) in the frame 1 slot 5 can be considered. Here, the control unit 169 selects the quadrature modulator 167.

  When the quadrature modulator is determined, the setting of the variable amplifier 174 used in the frame 1 slot 5 is determined. The control unit 169 sets the amplification factor of the variable amplifier 174 to +15 dB.

  Thereafter, the control unit 169 causes the DC offset control circuit 175 to perform calibration of the DC offset of the quadrature modulator 167, and the DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 167. This prepares for transmission of frame 1 slot 5.

  At the timing of moving from frame 1 slot 4 to frame 1 slot 5, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 167 and the variable amplifier to the variable amplifier 174. The switch 172 is controlled.

(Operation in frame 1 slot 5)
In frame 1 slot 5, data is transmitted by a combination of quadrature modulator 167 and variable amplifier 174. During this time, the control unit 169 sets the quadrature modulator and variable amplifier 173 used in the frame 1 slot 6. First, the control unit 169 determines an output gain. In FIG. 10, the output gain in frame 1 slot 6 is assumed to be −44 dB. Under this condition, a quadrature modulator 167 (−60 dB), a quadrature modulator 166 (−50 dB), and a quadrature modulator 165 (−40 dB) can be considered.

  Since the quadrature modulator 167 is in use, the control unit 169 selects either the quadrature modulator 166 or the quadrature modulator 165. In the figure, the quadrature modulator 166 is selected.

  The output gain of the quadrature modulator 166 is −50 dB. Therefore, the control unit 169 sets the amplification factor of the variable amplifier 173 to +6 dB.

  Thereafter, the control unit 169 causes the DC offset control circuit 175 to execute calibration of the DC offset of the quadrature modulator 166, and the DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 166.

  At the timing of moving from frame 1 slot 5 to frame 1 slot 6, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 166 and the variable amplifier to the variable amplifier 173. The switch 172 is controlled.

(Operation in frame 1 slot 6)
In frame 1 slot 6, the transmitter transmits data using a combination of quadrature modulator 166 and variable amplifier 173. During this time, the control unit 169 determines the quadrature modulator used in the frame 1 slot 7 and sets the variable amplifier 174. First, the control unit 169 determines an output gain. In FIG. 10, it is assumed that the output gain in the frame 1 slot 7 is −42 dB. Under this condition, quadrature modulator 167 (−60 dB) + variable amplifier 174 (+18 dB), quadrature modulator 166 (−50 dB) + variable amplifier 174 (+8 dB) can be considered. Since the quadrature modulator 166 is used in the frame 1 slot 6, the control unit 169 selects the quadrature modulator 167 and sets the amplification factor of the variable amplifier 174 to +18 dB.

  Thereafter, the control unit 169 causes the DC offset control circuit 175 to perform calibration of the DC offset of the quadrature modulator 167. The DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 167.

  At the timing of moving from frame 1 slot 6 to frame 1 slot 7, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the orthogonal modulator to be used to the orthogonal modulator 167 and the variable amplifier to the variable amplifier 174. The switch 172 is controlled.

(Operation in frame 1 slot 7)
In frame 1 slot 7, the transmitter transmits data using a combination of quadrature modulator 167 and variable amplifier 174. During this time, the control unit 169 determines the quadrature modulator used in the frame 1 slot 8 and sets the variable amplifier 173.

  First, the control unit 169 determines an output gain. In FIG. 10, the output gain in the frame 1 slot 8 is assumed to be −45 dB. Under this condition, quadrature modulator 167 (−60 dB) + variable amplifier 173 (+15 dB), quadrature modulator 166 (−50 dB) + variable amplifier 173 (+5 dB) can be considered. Since the quadrature modulator 167 is used in the frame 1 slot 7, the control unit 169 selects the quadrature modulator 166 and sets the amplification factor of the variable amplifier 173 to +5 dB.

  Thereafter, the control unit 169 causes the DC offset control circuit 175 to perform calibration of the DC offset of the quadrature modulator 166. The DC offset control circuit 175 adjusts the DACs 124 -I and 124 -Q of the quadrature modulator 166.

  At the timing of moving from frame 1 slot 7 to frame 1 slot 8, the control unit 169 switches the baseband side changeover switch 171 and the RF side changeover to switch the quadrature modulator to be used to the quadrature modulator 166 and the variable amplifier to the variable amplifier 173. The switch 172 is controlled.

(Operation in frame 1 slot 8)
In frame 1 slot 8, the transmitter transmits data using a combination of quadrature modulator 166 and variable amplifier 173. During this time, the control unit 169 determines the quadrature modulator used in the frame 1 slot 9 and sets the variable amplifier 174.

  The control unit 169 determines the output gain. In FIG. 10, the output gain in the frame 1 slot 9 is assumed to be −47 dB. Under this condition, quadrature modulator 167 (−60 dB) + variable amplifier 174 (13 dB), quadrature modulator 168 (−70 dB) + variable amplifier 174 (23 dB) can be considered. Since the quadrature modulator 166 is used in the frame 1 slot 8, the control unit 169 can select either the quadrature modulator 167 or the quadrature modulator 168. In the figure, the control unit 169 selects the quadrature modulator 167. Accordingly, the variable amplifier 174 is also set to 13 dB.

  Thereafter, the DC offset calibration of the quadrature modulator 167 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at the timing when the frame 1 slot 8 moves to the frame 1 slot 9. .

(Operation in frame 1 slot 9)
In frame 1 slot 9, the transmitter transmits data using a combination of quadrature modulator 167 and variable amplifier 174. During this time, the control unit 169 determines the quadrature modulator used in the frame 1 slot 10 and sets the variable amplifier 173.

  The control unit 169 determines the output gain. In FIG. 10, it is assumed that the output gain in the frame 1 slot 10 is maintained at −47 dB. Since the condition is the same as that of the slot 9 and the quadrature modulator 167 is in use, the control unit 169 selects the quadrature modulator 168. Accordingly, the variable amplifier 173 is also set to 23 dB.

  Thereafter, the DC offset calibration of the quadrature modulator 168 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at the timing of moving from the frame 1 slot 9 to the frame 1 slot 10. .

(Operation in frame 1 slot 10)
In frame 1 slot 10, the transmitter transmits data using a combination of quadrature modulator 168 and variable amplifier 173. During this time, the control unit 169 determines the quadrature modulator used in the frame 1 slot 11 and sets the variable amplifier 174.

  The control unit 169 determines the output gain of the transmitter. In FIG. 10, it is assumed that the output gain in the frame 1 slot 11 is maintained at −47 dB. Since the condition is the same as that of the slot 9 and the quadrature modulator 168 is in use, the control unit 169 selects the quadrature modulator 167. The variable amplifier 174 is not changed and remains set at 13 dB.

  Thereafter, the DC offset calibration of the quadrature modulator 167 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at the timing of moving from the frame 1 slot 10 to the frame 1 slot 11. .

(Operation in frame 1 slot 11)
In frame 1 slot 11, the transmitter transmits data using a combination of quadrature modulator 167 and variable amplifier 174. The control unit 169 determines the quadrature modulator used in the frame 1 slot 12 and sets the variable amplifier 173.

  In FIG. 10, the output gain in the frame 1 slot 12 changes to −49 dB. In order to satisfy this condition, a quadrature modulator 168 (−70 dB) + variable amplifier 174 (21 dB), a quadrature modulator 167 (−60 dB) + variable amplifier 174 (11 dB) can be considered. Since the quadrature modulator 167 in use is unexpected, the control unit 169 selects the quadrature modulator 168. Accordingly, the control unit 169 sets the amplification factor of the variable amplifier 174 to 21 dB.

  Thereafter, DC offset calibration of the quadrature modulator 168 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at a timing when the frame 1 slot 11 moves to the frame 1 slot 12. .

(Operation in frame 1 slot 12)
In frame 1 slot 12, the transmitter transmits data using a combination of quadrature modulator 168 and variable amplifier 173. The control unit 169 determines the quadrature modulator used in the frame 1 slot 13 and sets the variable amplifier 174.

  In FIG. 10, the output gain in the frame 1 slot 13 changes to −50 dB. As a combination of the quadrature modulator and the variable amplifier satisfying this condition, a quadrature modulator 168 (−70 dB) + variable amplifier 174 (+20 dB), a quadrature modulator 167 (−60 dB) + variable amplifier 174 (+10 dB) can be considered.

  Since the quadrature modulator 168 in use is unexpected, the control unit 169 selects the quadrature modulator 167. Accordingly, the control unit 169 sets the amplification factor of the variable amplifier 174 to +10 dB.

  After that, DC offset calibration of the quadrature modulator 167 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at the timing when the frame 1 slot 11 moves to the frame 1 slot 12. .

(Operation in frame 1 slot 13)
In frame 1 slot 13, the transmitter transmits data using a combination of quadrature modulator 167 and variable amplifier 174. The control unit 169 determines the quadrature modulator used in the frame 1 slot 14 and sets the variable amplifier 173.

  In FIG. 10, the output gain of the transmitter in the frame 1 slot 14 is maintained at −50 dB. As described above, any of quadrature modulator 168 (−70 dB) + variable amplifier 174 (+20 dB), quadrature modulator 167 (−60 dB) + variable amplifier 174 (+10 dB) can be considered to satisfy this condition. However, since the quadrature modulator 167 in use is unexpected, the control unit 169 selects the quadrature modulator 168. Accordingly, the control unit 169 sets the amplification factor of the variable amplifier 173 to +20 dB.

  After that, DC offset calibration of the quadrature modulator 168 is performed by the DC offset control circuit 175, and the baseband side switch 171 and the RF side switch 172 are switched at the timing when the frame 1 slot 13 moves to the frame 1 slot 14. .

(Operation in frame 1 slot 14)
In frame 1 slot 14, the transmitter transmits data using a combination of quadrature modulator 168 and variable amplifier 173. The control unit 169 determines a quadrature modulator to be used in frame 2 slot 0 and sets the variable amplifier 174.

  In FIG. 10, the output gain of the transmitter in frame 2 slot 0 is maintained at −50 dB. Since the quadrature modulator in use is not taken into consideration, the control unit 169 selects the quadrature modulator 167 and sets the amplification factor of the variable amplifier 174 to 10 dB.

  Thereafter, the DC offset calibration of the quadrature modulator 167 is performed by the DC offset control circuit 175, and the baseband side changeover switch 171 and the RF side changeover switch 172 are switched at the timing of moving from the frame 1 slot 14 to the frame 2 slot 0. .

  As described above, one or two other quadrature modulators are prepared in addition to the quadrature modulator used at the time of transmission of one slot, and the DC offset calibration is executed before switching the slot, thereby switching the slot. Sometimes it is possible to use a quadrature modulator corrected in the latest situation. As a result, it is possible to provide a transmitter that can dynamically correct a DC offset even in UMTS that continuously performs transmission, which is an object of the present invention.

  In the third embodiment, the quadrature modulator is not variable. However, it is also possible to further expand the selection range of the quadrature modulator by using the variable quadrature modulator. At this time, how to determine the variable amount of the output gain of the variable quadrature modulator and the variable amount of the output gain of the variable amplifier is a matter of design.

  In the above description, two variable amplifiers are described. However, three or more variable amplifiers may be present.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention assumes application in a carrier leak calibration mechanism of a UMTS transmitter (including a transceiver). However, the present invention can be applied in the same manner as UMTS as long as it is a communication mode that continuously transmits one channel without a break.

  The present invention is also applied to a portable information terminal (including a mobile phone) including these transmitters.

It is a block diagram showing where a carrier leak calibration mechanism is located in a transmitter / receiver. It is a block diagram which shows the circuit structure around the conventional quadrature modulator. 1 is a block diagram showing a circuit configuration around a quadrature modulator according to a first embodiment of the present invention. It is a figure explaining the timing of the calibration of the conventional UMTS transmitter. It is a figure explaining the timing of the calibration of the UMTS transmitter based on the 1st Embodiment of this invention. It is a conceptual diagram of the operation | movement in the 2nd Embodiment of this invention. It is a block diagram which shows the circuit structure of the orthogonal modulator periphery concerning the 2nd Embodiment of this invention. It is a conceptual diagram of the operation | movement in the 3rd Embodiment of this invention. It is a block diagram which shows the circuit structure of the periphery of the quadrature modulator in connection with the 3rd Embodiment of this invention. It is a figure which shows the usage of the quadrature modulator and variable amplifier in the 3rd Embodiment of this invention.

Explanation of symbols

1, 2, 3, 4, 5, 6, 7, 8 ... variable quadrature modulator,
101 ... Antenna, 102 ... Duplexer, 103 ... Oscillator, 111 ... BPF,
112 ... LNA, 113 ... mixer circuit, 114 ... amplifier, 115 ... BPF,
116 ... AD converter, 121 ... DA converter, 122 ... Attenuator,
123 ... LPF, 124, 124-I, 124-Q ... DAC,
125 ... mixer circuit, 126 ... amplifier, 127 ... SAW, 128 ... HPA,
129 ... DC offset control circuit, 130 ... quadrature modulator,
131 ... 90 degree phase shifter, 151, 152 ... quadrature modulator, 153 ... control unit,
154 ... DC offset control circuit, 155 ... Baseband side changeover switch,
156... RF side changeover switch, 159... Control unit,
161, 162, 163, 164, 165, 166, 167, 168 ... quadrature modulator,
169 ... control unit,
171: Baseband switch, 172: RF switch,
173, 174 ... variable amplifier, 175 ... DC offset control circuit.

Claims (9)

A transmission comprising a plurality of transmission slots during data transmission, comprising two or more quadrature modulators each having a different gain and a control unit for selecting one quadrature modulator to be used for transmission from the two or more quadrature modulators A transmitter for continuously transmitting frames,
The control unit switches the two or more quadrature modulators in units of the transmission slots and uses them for transmission.   2. The transmitter according to claim 1, wherein gains of the two or more quadrature modulators are distributed at equal intervals with reference to decibels. The transmitter of claim 2, further comprising two or more variable amplifiers,
Each of the two or more variable amplifiers has a variable width that is twice the gain distribution interval of the two or more quadrature modulators,
The transmitter is characterized in that the control unit switches the two or more variable amplifiers for each transmission slot, and updates the setting of the two or more variable amplifiers. The transmitter according to claim 3, further comprising a DC offset control circuit,
The control unit selects one of the quadrature modulators not used for data transmission as a DC offset calibration target, inputs dummy data to the DC offset calibration target, and the output of the DC offset calibration target is the Input to the DC offset control circuit,
The transmitter, wherein the DC offset control circuit performs calibration of the DC offset calibration target.   5. The transmitter according to claim 4, wherein when the quadrature modulator is switched in units of the transmission slot, the control unit selects the DC offset calibration target of the transmission slot that has just ended for transmission. Transmitter.   6. The transmitter according to claim 4, wherein selection of the DC offset calibration target and setting of the variable amplifier are determined based on a transmission gain of a next transmission slot. A plurality of variable quadrature modulators each having a variable gain and a control unit that selects one variable quadrature modulator to be used from the two or more variable quadrature modulators; A transmitter for continuously transmitting a transmission frame composed of slots,
The control unit switches the two or more variable quadrature modulators in units of the transmission slots and uses them for transmission.   8. The transmitter according to claim 7, wherein the control unit selects one variable quadrature modulator to be used from the two or more variable quadrature modulators based on a transmission gain of the transmission slot.   A portable information terminal using the transmitter according to claim 1.

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