JP2006287877A - Linearizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linearizer capable of suppressing instantaneous spectrum spreading on a frequency axis by suppressing occurrence of an impulse-like DC voltage change in a baseband input of a modulator while maintaining power supply control due to burst operation of a circuit required for equipment even in a leading block or the like of burst transmission of a TDMA transmitter. <P>SOLUTION: Even in the leading block or the like of burst transmission of a TDMA transmitter, a switch 10 for electrically connecting or disconnecting a baseband signal input terminal 4 and a DC offset controllable terminal 7 is controlled in accordance with a burst timing, thereby suppressing the occurrence of an impulse-like DC voltage change in the baseband input of a modulator 28 and suppressing instantaneous spectrum spreading on a frequency axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linearizer such as a Cartesian loop system.

  Conventionally, in order to suppress spurious due to a DC offset generated in a modulator or a differential amplifier, a method of adjusting a DC value of a baseband signal input to the modulator or a DC value of one element of a differential amplifier after demodulation Is generally known.

  FIG. 7 shows an example of a circuit configuration for performing DC offset adjustment in a conventional modulator. This circuit includes a load resistor 1, a semiconductor element 2, a local signal differential input terminal 3, and a baseband. Signal input terminal 4, current source 5, DC offset adjustment variable voltage DC power supply 6, DC offset adjustment variable voltage DC power supply connection terminal 7, modulated wave differential output terminal 8, and main power supply for modulator 28 The connection terminal 9 is comprised.

  The spurious appearing in the modulator output and caused by the DC offset is reduced by adjusting the DC voltage of the DC offset adjusting variable voltage DC power source 6 connected to the DC offset adjusting variable voltage DC power source connection terminal 7. The At this time, the DC voltages of the baseband signal input terminal 4 and the DC offset adjusting variable voltage DC power source 6 are substantially equal. Also, the DC offset factor that is normally assumed is the base-emitter potential difference between the semiconductor elements of the baseband circuit and the modulator, variations in resistance value creation, temperature changes thereof, and the like.

  In a Cartesian loop type linearizer that compensates for non-linear distortion of the transmission system by a negative feedback loop, a DC voltage at the baseband signal input terminal 4 is taken out by a low-pass filter, compared with a reference voltage, and a baseband signal input by the difference is obtained. An adaptive DC offset correction that corrects the DC voltage at the terminal 4 has been proposed (see, for example, Patent Document 1).

  Also, in a TDMA (Time Division Multiple Access) system radio, a variable gain amplifier or power amplifier of a transmission system is used in a transmission off section at the time of burst transmission in order to reduce power consumption and reduce transmitter noise to a receiving circuit. It is necessary to turn off the power. Similarly, in the example of the transmitter using the Cartesian distortion compensation method in which the negative feedback loop is formed and the distortion compensation is performed in the baseband shown in FIG. 8, the variable gain amplifier 34 and the power amplifier are used in the transmission off period at the time of burst transmission. 35 is disconnected from the transmission main power supply 24.

  The basic operation of the transmitter of FIG. The undistorted signal output from the baseband signal generator 21 is mixed with the local signal by the modulator 28 to become a high-frequency modulated signal, and passes through the variable gain amplifier 34 and the power amplifier 35. At this time, the power amplifier 35 generates nonlinear distortion. A part of the high-frequency signal including the distortion is extracted by the directional coupler 36, the level is adjusted by the variable attenuator 33, and then converted to a baseband signal by the demodulator 32. By subtracting the baseband signal including the distortion from the undistorted baseband signal of the baseband signal generator 21 by the subtractor 31, only the distortion component having the opposite phase is extracted. The error (antiphase distortion) amplified by the error amplifier 30 is added to the undistorted baseband signal of the baseband signal generator 21 by the adder 29. That is, this signal includes an inverse characteristic of distortion generated by the power amplifier 35, and is modulated by this signal and passed through the power amplifier 35 to compensate for nonlinear distortion of the power amplifier 35.

  However, in the Cartesian distortion compensation method, when the high-frequency power input to the feedback system 40 is turned off by turning off the power of the variable gain amplifier 34 or the power amplifier 35, the circuit does not operate as a closed loop, and the circuit is simply fed back. It becomes a signal inverting amplifier circuit. At this time, the DC value of the signal input terminal of the feedback system slightly shifts from a stable transmission state (a state in which the DC offset is adjusted) due to a change in impedance of the semiconductor elements constituting the demodulator 32 and the like. When this slight DC value deviation is amplified by the error amplifier 30 and input to the modulator 28, the DC value greatly deviates from the stable transmission state (the state in which the DC offset is adjusted). End up. Here, when the variable gain amplifier 34 and the power amplifier 35 are turned on again to enter the transmission state, a closed loop is formed again, and the feedback system is in a stable transmission state (a state where the DC offset is adjusted). The desired high-frequency power is input, and the amplified error (shifted greatly) DC value is changed (returned) to the DC value in the stable transmission state in a very short time according to the response speed of the loop.

  A power amplifier power switch 26 that is turned on / off by a power amplifier power control signal 22 output from the transmitter controller 20 is provided between the transmission main power supply 24 and the power amplifier 35. Between the transmission main power supply 24 and the variable gain amplifier 34, there is provided a variable gain amplifier power switch 27 which is turned on / off by a variable gain amplifier power control signal 23 output from the transmitter control device 20. ing. The directional coupler 36 is connected to an antenna 39 through an isolator 37 and a transmission / reception switching high-frequency switch 38.

  FIG. 9 shows a temporal change in the baseband input of the modulator at this time. The movement in which the DC value greatly changes is the same phenomenon as when an impulse is input to the baseband input of the modulator, and the waveform in the transition process is not subject to any band limitation as an original communication signal, At that moment, spectrum spread occurs on the frequency axis as shown in FIG. In order to cope with such a change, a method (ramping) for smoothing the rising of the variable gain amplifier 34 or the rising of the baseband signal is also conceivable.

JP 2001-333124 A

  However, the above-mentioned Cartesian loop type linearizer adaptively tries to suppress the deviation of the DC value, but the follow-up speed is slow because there are many additional circuits such as a differential amplifier, and it is slow due to temperature changes and changes over time. Even if the offset fluctuation can be followed, in the first section of burst transmission of the TDMA transmitter, etc., it is not possible to correct the deviation of a large DC offset in a very short period, and spurious is radiated during that period. There was a drawback of end. Further, since control means such as a low-pass filter and a comparator are required, there is a drawback that the apparatus becomes large.

  In the case of a method (ramping) in which the rise of the variable gain amplifier 34 and the rise of the baseband signal are smoothed (ramping), control according to conditions (extra control) such as waveform optimization control in accordance with the modulation signal bandwidth on the signal processing side. Therefore, if the signal is within the band of the negative feedback loop design, the characteristic of the system that the closed loop operation with the same control can be performed is impaired. Further, as the gain of the error amplifier 34, which is the convergence accuracy in the closed loop and is the distortion improvement amount itself, increases, the amount of deviation increases and the spread of the spectrum increases. If the baseband signal or the gain of the amplifier or the rise of the power supply is slowed down in order to suppress it, there is a possibility that the information at the beginning of the necessary signal is lost. In other words, it is impossible to absorb a large DC voltage fluctuation in an extremely short time using an existing method such as ramping.

  The present invention has been made in view of such circumstances, and the baseband of the modulator is maintained while maintaining the above-described power control by the burst operation of the circuit necessary for the device even in the head section of the burst transmission of the TDMA transmitter. An object of the present invention is to provide a linearizer that can suppress the occurrence of an impulse DC voltage change at the input and suppress the spread of the spectrum on the instantaneous frequency axis.

The above object is achieved by the following configuration.
(1) A linearizer that electrically connects or disconnects a modulation means having a baseband signal input terminal and a DC offset adjustable terminal, and the baseband signal input terminal and the DC offset adjustable terminal. Terminal connection cutting means, and control means for controlling the terminal connection cutting means.

(2) The linearizer according to (1), further comprising power control means for controlling the power circuit of the Cartesian loop, wherein the power control means and the control means for controlling the terminal connection disconnecting means are synchronized or have a predetermined time difference. Control with.

  In the linearizer described in (1) above, a terminal for electrically connecting or disconnecting a baseband signal input terminal and a terminal capable of adjusting a DC offset in accordance with the burst timing even in the first section of burst transmission of a TDMA transmitter By controlling the connection disconnection means, it is possible to suppress the occurrence of an impulse DC voltage change at the baseband input of the modulator, and to suppress the spread of the spectrum on the instantaneous frequency axis.

  In the linearizer described in the above (2), the power supply circuit of the Cartesian loop is synchronized with the control means for controlling the terminal connection cutting means for electrically connecting or disconnecting the baseband signal input terminal and the DC offset adjustable terminal. By controlling at a predetermined time difference, not only the instantaneous spread of the spectrum on the frequency axis can be suppressed, but also a reduction in power consumption during non-transmission can be realized.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a circuit diagram showing a configuration of a Cartesian loop type linearizer according to Embodiment 1 of the present invention. In this figure, the Cartesian loop type linearizer of the present embodiment includes a load resistor 1, a semiconductor element 2, a local signal differential input terminal 3, a baseband signal input terminal 4, a current source 5, and a DC offset. Adjustable variable voltage DC power supply 6, DC offset adjusting variable voltage DC power supply connection terminal 7, modulated wave differential output terminal 8, main power supply connection terminal 9 of modulator (modulation means) 28, and switch (terminal connection) (Cutting means) 10, a transmitter control device (control means) 20, and a control signal 25 of the switch 10.

  Conventionally, when the transmission variable gain amplifier or power amplifier is turned off with a Cartesian loop type linearizer, the DC voltage is greatly shifted as shown in the transmission off section of FIG. In this embodiment, the spurious signal is output. In this embodiment, the baseband signal input terminal 4 is switched to the adjusted DC value by forcibly shorting the switch 10 to the transmission-off interval (electrical connection state). Therefore, the DC voltage difference between the transmission off period and the transmission on period does not occur as shown in FIG. That is, the spread of the spectrum is suppressed as shown in FIG.

  FIG. 2 is a block diagram showing a configuration example of a Cartesian distortion compensating transmitter using the Cartesian loop type linearizer of FIG. In FIG. 2, the same components as those in FIG. 8 described above are denoted by the same reference numerals, and description thereof is omitted. The configuration example of the Cartesian distortion compensation transmitter shown in FIG. 2 is that the control signal 25 of the switch 10 output from the transmitter controller 20 is supplied to the modulator 28 (switch 10). It is different from the thing.

  According to the Cartesian loop type linearizer of this embodiment, the baseband signal input terminal 4 and the DC offset adjustable terminal 7 can be adjusted in accordance with the burst timing even in the first section of burst transmission of the TDMA transmitter. By controlling the switch 10 that electrically connects or disconnects the transmitter 10 with the transmitter control device 20, the occurrence of an impulsive DC voltage change at the baseband input of the modulator 28 is suppressed, and the instantaneous frequency axis is changed. The spread of the spectrum can be suppressed.

(Embodiment 2)
FIG. 5 is a circuit diagram showing a configuration of a Cartesian loop type linearizer according to Embodiment 2 of the present invention. The basic circuit configuration is the same as in FIG. 1 except that a variable gain amplifier power control signal 23 output from the transmitter controller 20 is used as a control signal for controlling the switch 10. In synchronization with the switch 10 being connected (turned on) during the transmission off period, the power of the variable gain amplifier is turned off to reduce the power consumption during transmission while suppressing the spread of the spectrum.

  FIG. 6 is a block diagram showing a configuration example of a Cartesian distortion compensating transmitter using the Cartesian loop type linearizer of FIG. In FIG. 6, the same components as those in FIG. 8 described above are denoted by the same reference numerals, and description thereof is omitted. Further, the configuration example of the Cartesian distortion compensation transmitter shown in FIG. 6 is illustrated in that the variable gain amplifier power control signal 23 output from the transmitter controller 20 is supplied to the modulator 28 (switch 10). It is different from eight.

  According to the Cartesian loop type linearizer of this embodiment, all or a part of the power circuit of the Cartesian loop is electrically connected to the baseband signal input terminal 4 and the DC offset adjustable terminal 7 or By controlling in synchronization with the power supply control means that controls the means for cutting or with a predetermined time difference, not only suppresses the spread of the spectrum on the frequency axis instantaneously, but also realizes low power consumption during non-transmission. be able to.

  The present invention controls terminal connection / cutting means for electrically connecting or disconnecting a baseband signal input terminal and a terminal capable of adjusting a DC offset in accordance with the burst timing even in a burst transmission head section of a TDMA transmitter. Thus, it is possible to suppress the occurrence of an impulse DC voltage change at the baseband input of the modulator, and to suppress the spread of the spectrum on the instantaneous frequency axis. Useful for machine etc.

1 is a circuit diagram showing a configuration of a Cartesian loop type linearizer according to Embodiment 1 of the present invention; 1 is a block diagram showing a configuration example of a Cartesian distortion compensation transmitter using the Cartesian loop linearizer of FIG. The figure which shows the time change of the modulator input signal at the time of using this invention The figure which shows the transmitter output (no DC sudden change) at the time of using this invention A circuit diagram showing composition of a Cartesian loop type linearizer concerning Embodiment 2 of the present invention FIG. 5 is a block diagram showing a configuration example of a Cartesian distortion compensation transmitter using the Cartesian loop linearizer of FIG. Circuit diagram showing the configuration of a conventional Cartesian loop linearizer FIG. 7 is a block diagram showing a configuration example of a Cartesian distortion compensation transmitter using the Cartesian loop linearizer of FIG. The figure which shows the time change of the modulator input signal when not using this invention The figure which shows the transmitter output (with DC sudden change) when not using this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Load resistance 2 Semiconductor element 3 Local signal differential input terminal 4 Baseband signal input terminal 5 Current source 6 DC offset adjustment variable voltage DC power supply 7 DC offset adjustment variable voltage DC power supply connection terminal 8 Modulation wave differential output terminal 9 Modulator main power supply connection terminal 10 Switch 20 Transmitter control device 21 Baseband signal generator 22 Power amplifier power supply control signal 23 Variable gain amplifier power supply control signal 24 Transmission system main power supply 25 Switch 10 control signal 26 Power amplifier power supply Switch 27 variable gain amplifier power switch 28 modulator 29 adder 30 error amplifier 31 subtractor 32 demodulator 33 variable attenuator 34 variable gain amplifier 35 power amplifier 36 directional coupler 37 isolator 38 transmission / reception switching high-frequency switch 39 antenna 40 Return system

Claims (2)

Modulation means having a baseband signal input terminal and a DC offset adjustable terminal;
A terminal connection cutting means for electrically connecting or disconnecting the baseband signal input terminal and the DC offset adjustable terminal;
Control means for controlling the terminal connection cutting means;
A linearizer comprising:   2. The linearizer according to claim 1, further comprising a power control unit that controls a power circuit of a Cartesian loop, wherein the power control unit and the control unit that controls the terminal connection cutting unit are controlled synchronously or at a predetermined time difference.

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