JP3988656B2 - Wireless communication apparatus and integrated circuit used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult to use an up-converter for controlling a power supply voltage for a power amplifier of a high-EER portable telephone because it exhibits low responsivity and it can not decrease a voltage lower than the power supply voltage though the range of control can be extended by using it. <P>SOLUTION: A power supply voltage control circuit of an EER type which exhibits a wide control range and high responsivity is obtained by combining the up-converter with a high-responsivity step-down element. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device that performs transmission in a wireless communication system such as a mobile phone or a wireless LAN, and a configuration of an integrated circuit used as a component in the device. In particular, it is suitable for a wireless communication apparatus of a wireless communication system that employs a modulation method for transmitting information by changing both the phase and amplitude.
[0002]
[Prior art]
In recent years, in a wireless communication system such as a mobile phone, a modulation method (for example, 16QAM: Quadrature Amplitude Modulation) that transmits information by changing both the phase and the amplitude is often used. In this modulation method, if the waveform of the transmission signal is distorted, data cannot be correctly identified on the receiving side, so that high linearity is required for the transmission power amplifier that amplifies the signal. Conventional wireless communication terminals have met this requirement by using linear amplifiers, but linear amplifiers have poor power efficiency. Therefore, the inventors combined an EER (Envelope Elimination and Restoration) method and a conventional linear amplifier method according to Japanese Patent Application No. 2002-259526 filed by the same applicant, and a saturation amplifier that is efficient even in a mobile phone having a wide output dynamic range. A configuration that can be used is proposed.
[0003]
As a method for further expanding the output dynamic range, for example, an up converter is used for the EER power supply voltage control circuit described in Non-Patent Document 1, and the power supply voltage is temporarily boosted to increase the power voltage to a power amplifier. The method of giving to is known. The saturation amplifier used in the EER system is proportional to the power supply voltage Vdd and the output voltage Vout, and changes Vout by controlling Vdd. However, when Vdd drops below a certain level, the transistor inside the amplifier does not operate. The problem is that the control range is narrower than that of a linear amplifier that controls Vout with the input voltage Vin. By increasing Vdd, the control range is expanded and the output dynamic range can be expanded.
[0004]
FIG. 3 shows a circuit configuration of a BOOST type DC-DC converter known as a general upconverter. In the BOOST type DC-DC converter, the other end of the inductance L302 connected to the power supply 301 is turned on / off with respect to GND by using a switch 303 such as an FET, and the energy stored in the inductance L302 is extracted by the rectifier diode D304. , Obtain an output voltage higher than the original power supply voltage. Some switched-capacitor upconverters store energy in capacitance instead of inductance.
[0005]
[Patent Document 1]
US Pat. No. 6,377,784 [Non-Patent Document 1]
M. Ranjan Et. Al, “Microwave Power Amplifiers with Digitally-controlled Power Supply Voltage for High Efficient and High Linear E 2000”
[Non-Patent Document 2]
T. Yamawaki et.al, "A 2.7-V GSM RF transceiver IC" IEEE Journal of Solid-State Circuits vol. 32, Issue 12, pp 2089-2096, Dec. 1997.
[0006]
[Problems to be solved by the invention]
The upconverter stores energy in an inductance or capacitance and rectifies and boosts its output, causing a slight delay until the output voltage rises to the desired voltage. If the responsiveness is made faster, the amount of energy that can be stored is reduced, and a high voltage or current cannot be generated. In order to expand the control range, it is necessary to control not only to increase the power supply voltage but also to decrease it.
[0007]
[Means for Solving the Problems]
The present invention provides a power supply voltage control circuit for the EER system having a wide control range and quick response by configuring an up converter in combination with a step-down element (regulator or the like) having quick response. In addition, a technique for analyzing transmission signal waveform information prior to output from a power amplifier to determine whether or not boosting is necessary and generating a control signal to each element is shown.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
First, the configuration of a general terminal used in a wireless communication system will be described with reference to FIG. A reception signal received from the antenna 107 is transmitted and received by an antenna switch (or duplexer) in the front end unit 101, subjected to filtering, and then subjected to frequency conversion in the radio unit 102 and dropped to a baseband band. Further, the signal is converted into a digital signal by the interface unit 103, demodulated by the baseband unit 104, output through the user interface unit 105, and used for subsequent processing. A transmission signal to be transmitted to the base station is input to the baseband unit 104 via the user interface unit 105 and subjected to a modulation process such as error correction coding. Thereafter, the transmission signal is converted into an analog signal in the interface unit 103, becomes a signal of a desired frequency band in the wireless unit 102, is filtered by the front end unit 101, and is transmitted from the antenna 107. The control unit 106 uses a CPU or DSP to set parameter values in each unit, perform timing management, and the like. In particular, the present invention relates to a circuit configuration technique of a high-frequency integrated circuit (RF-IC) 108, a power amplifier (109), an EER control unit (110), and an interface unit 103, which are one of the main components of the radio unit 102. Is. The interface unit 103 can be physically configured as part of the baseband unit 104, configured as part of the RF-IC 108, or configured as part of the EER control unit 110. Further, the EER control unit 110 can be configured as a part of the RF-IC 108 or can be combined with the power amplifier 109 to be an EER type power amplifier module.
[0009]
Next, with reference to FIG. 2, a description will be given of a first embodiment of the transmission system radio unit and interface unit configuration according to the present invention. In this embodiment, the IQ → EER conversion unit 202 of the interface unit 201 is placed in front of the DACs 204 to 206, and functions are realized by digital signal processing. If the functions are equivalent, the same effect can be obtained even if they are realized by analog signal processing. The IQ → EER conversion unit 202 separates and extracts amplitude information and phase information. In the conventional EER system, the phase information is represented only by the phase angle θ, but in the present embodiment, the phase information is represented by an IQ orthogonal component projected on a unit circle and is output to the RF-IC 207. Since the IQ orthogonal component on the unit circle always has a constant amplitude value when combined, it has no amplitude information. However, since the frequency conversion can be performed in the same manner as the IQ orthogonal component in the case of the conventional linear method, the conventional RF-IC This is advantageous in that the circuit configuration technology (quadrature modulator, filter, etc.) is easily utilized (details are described in Japanese Patent Application No. 2002-259526 filed by the same applicant). In addition to the transmission signal, transmission power level information L is also sent from the baseband unit 104 to the EER control unit 210 via the DAC 203 of the interface unit. The RF-IC 207 frequency-converts the input signal represented by IQ on the unit circle by the quadrature modulator 208. The frequency-converted and IQ-combined result is input to the signal input pin of the saturation power amplifier 209. Here, IQ notation on a unit circle and frequency conversion by a quadrature modulator are used, but the same effect can be obtained even if the circuit configuration is different as long as the processing contents are equivalent. On the other hand, the amplitude information R is input to the EER control unit 210, separated and converted into control signals for the up converter and the step-down element together with the transmission power level information L, and then supplied to the up converter 211 and the step-down element 212. Upconverter 211 and step-down element 212 are connected in series to DC power supply Vdd 213 and control the power supply voltage that drives the power supply voltage pin of power amplifier 209. Since the output voltage of the saturation power amplifier 209 basically changes in proportion to the power supply voltage, the envelope modulation of the output signal can be performed by controlling the power supply voltage. Even if voltage control is applied not only to the power supply voltage side terminal but also to the ground side terminal of the power amplifier, the same effect can be obtained if the voltage applied to the power amplifier is the same. However, in this case, the input of the power amplifier needs to be a differential input.
[0010]
Next, a second embodiment of the configuration of the transmission radio unit and interface unit according to the present invention will be described with reference to FIG. In this embodiment, an offset PLL system (see Non-Patent Document 2) is used for the RF-IC 802. An input signal from the interface unit 801 is frequency-converted to the IF frequency band by the quadrature modulator 803, and the IQ synthesized result is input to the frequency control terminal of the RF-VCO 805 through the phase comparator 804. The output of the RF-VCO 805 is amplified by the power amplifier 806, divided by the coupler, multiplied by the IF frequency local signal 807 and the mixer 808, and fed back to the phase comparator 804. In this embodiment, the control signal L810 to the up-converter and the control signal R811 to the step-down element are separated and converted by digital signal processing in the IQ → EER conversion unit in the interface unit. Thereby, the processing burden by the EER control unit 807 can be reduced. The separation conversion process can also be performed in the baseband unit. The output signal of the power amplifier 806 is divided by a coupler and fed back to the EER control unit 809. A configuration in which the feedback signal is returned to the interface unit or the baseband unit is also conceivable. Each component of the configuration example shown in FIG. 8 can be independently replaced with a corresponding portion of the first embodiment.
[0011]
Next, a first embodiment of transmission output control according to the present invention will be described with reference to FIG. A wireless communication system using an OFDM (Orthogonal Frequency Division Multiplexing) scheme such as IEEE802.11a is characterized in that PAPR 501 (Peak to Average Power Ratio) is as large as 12 to 17 dB. In order to apply the EER method to a system with a wide range of instantaneous changes in transmission output, it is necessary to make the power supply voltage control width of the power amplifier as wide as possible, but the power supply voltage change width of the power amplifier is usually about 2-3V. In order to control the transmission output to change by 12 dB (about 15 times) within this range, it is necessary to make the slope of the power supply voltage-transmission output characteristic steep, which is difficult to realize. In this embodiment, an up-converter is used to boost the power supply voltage of the power amplifier to a value higher than the power supply voltage of the DC power supply only during the interval 502 in which the transmission power is significantly larger than the average value. The envelope voltage is modulated at high speed by reducing the control voltage to the required value. The output voltage waveform of the up-converter is shown at 503, and the output voltage waveform of the step-down element is shown at 504.
[0012]
A configuration example of a circuit necessary for determining the range of the boosting section 502 is shown in FIG. The IQ transmission signal 701 modulated by the baseband unit is synthesized, and the peak hold circuit 702 detects the maximum value of the baseband signal. In step 703, the step-up switching threshold value is compared with the maximum output value. If the threshold value is greater than or equal to the threshold value, step-up On is selected. If step-down is greater, step-up Off is selected and set in the IQ-EER conversion unit 705 or EER control unit in the interface unit 708. . In order to correct the processing delay of the blocks 702 and 703 and the processing circuit delay Tdc of the EER control unit 110 at the subsequent stage, it is necessary to delay the input transmission signal to the IQ-EER conversion unit 705. As the delay element 704, a memory, a shift register, or the like is used. The boost determination circuit 706 can be included in any of the baseband unit 707, the interface unit 708, and the EER control unit 110 due to its configuration.
[0013]
Next, a second embodiment of transmission output control according to the present invention will be described with reference to FIG. This embodiment also uses an up-converter as in the first embodiment, but there is a difference in the method for determining the boosting section. In the first embodiment, the transmission output waveforms are sequentially compared and boosted only in a necessary interval. In the present embodiment, the presence or absence of boosting is determined only once in the transmission power control period, and boosting is necessary. Boosts the entire control cycle section 601. By reducing the number of determinations in the boosting section, the power efficiency is slightly reduced, but the processing load is reduced, so that the power consumption of the control circuit is reduced. It is also possible to realize a configuration in which the baseband unit 104 determines the boosting interval and the interface unit 103 only follows the control signal in terms of the control cycle. Whether to boost or not in a certain control cycle section 601 is determined by setting the channel being transmitted (modulation method to be used, the number of channels simultaneously multiplexed and transmitted, the power ratio between channels, each channel output, and the bit for the combined output) This is performed based on the maximum PAPR value 602 obtained from the adjustment method and the like and the average control level value 603. When maximum PAPR value 602 + average control level value 603 <boosting switching threshold value 604, boosting is OFF, and when maximum PAPR value 602 + average transmission power control level value 603 ≧ boosting switching threshold value 604, boosting is ON. When the step-up OFF period continues according to the channel setting condition, the operation of the determination circuit itself is stopped or paused unless a parameter related to the determination formula is changed. Since the up-converter takes time for the circuit delay Tdc from the start of control until the output voltage actually increases, the up-converter starts the control by Tdc 605 from the timing at which transmission power control is actually desired. When returning to the original state, conversely, the control voltage is changed after the control section is completely completed. The output voltage waveform of the up-converter is shown at 606, and the output voltage waveform of the step-down element is shown at 607.
[0014]
Next, a third embodiment of transmission output control according to the present invention will be described with reference to FIG. In a wireless communication standard such as W-CDMA, a wireless communication state between a base station and a terminal is monitored, and closed-loop transmission power control is performed so that communication can be performed with appropriate power. In the example of W-CDMA (3GPP standard DS-FDD system), the transmission power of the wireless terminal is ± 1 power control step 402 (normal transmission) in accordance with the timing of the slot head at every control cycle 401 (1 slot = 667 μs). In the case of = 1 dBm). A method corresponding to this transmission power control in the transmission system configuration according to the present invention will be described.
[0015]
(1) When the transmission power is increased by one power control step (when continuously increasing twice or more)
In this embodiment, the up-converter is controlled to be constant at a value higher than the required power supply voltage control value for obtaining the transmission power required as a result of control, and the control voltage is lowered to the required value by the step-down element. Therefore, high-speed envelope modulation is performed. The up-converter control margin 403 is desirably set to the same level as the PAPR determined by the transmission signal modulation method. If the power control is in the positive (increase) direction twice in the process of transmission power control (404 in the figure), the up-converter is turned on by Tdc (405) hours before the actual increase in transmission power. Start control. An output voltage waveform of the up-converter is indicated by 406, and an average output voltage level of the step-down element is indicated by 407.
[0016]
(2) When the transmission power is lowered by one power control step (when turning from positive to negative)
In the process of transmission power control, when the power control changes from plus (increase) to minus (decrease) (408 in the figure), it cannot be lowered prior to the timing of actually reducing the transmission power as in the case of increasing, The up-converter control voltage is maintained by maintaining the same output level as in the previous transmission power period during the next transmission power control period, and increasing the amount reduced by the step-down element.
[0017]
(3) When the transmission power is lowered by one power control step (when continuously lowering twice or more)
In the process of transmission power control, if it is negative (decreased) twice or more consecutively (409 in the figure), the control voltage of the upconverter is lowered by the amount corresponding to the control step in accordance with the timing of actually reducing the transmission power. Since there is a margin for one control step in the control margin of the upconverter at the stage (2), the operation can be performed prior to the actual change point.
[0018]
(4) When the transmission power is increased by one power control step (when turning from minus to plus)
In the process of transmission power control, when the power control changes from minus (decrease) to plus (increase) (410 in the figure), the control voltage of the up-converter keeps the same output level as in the previous transmission power control period. Keep it, and reduce it by the step-down element. (2) Since there is a margin for one control step in the control margin of the upconverter at the stage of (3), it is not necessary to increase the power anew.
[0019]
In the present invention, the up-converter is described as an example in any of the embodiments, but a more efficient circuit can be realized by using an up-down converter capable of stepping up and down. Further, the control method in the third embodiment can be similarly applied to a circuit using a down converter that performs only step-down, and the same effect can be obtained.
[0020]
【The invention's effect】
According to the present invention, a power supply voltage control circuit for the EER system having a wide control range and quick response is provided by configuring an up-converter in combination with a step-down device having quick response.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a general terminal used in a wireless communication system.
FIG. 2 is a diagram showing a first embodiment of a configuration of a transmission radio unit / interface unit according to the present invention.
FIG. 3 is a diagram showing a circuit configuration of a general up-converter.
FIG. 4 is a diagram showing a third embodiment of transmission power control according to the present invention.
FIG. 5 is a diagram showing a first embodiment of transmission power control according to the present invention.
FIG. 6 is a diagram showing a second embodiment of transmission power control according to the present invention.
FIG. 7 is a diagram showing boost determination processing for transmission power control according to the present invention.
FIG. 8 is a diagram showing a second embodiment of the configuration of the transmission radio unit / interface unit according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Front end part, 102 ... Wireless part, 103, 202, 708, 801 ... Interface part, 104, 707 ... Baseband part, 105 ... User interface part, 106 ... Control part, 107 ... Antenna, 108, 207 , 802... RF-IC, 109, 209, 806... Power amplifier, 110, 210, 809... EER control unit, 202, 705... IQ to EER conversion unit, 203, 204, 205, 206 ... DAC, 208, 803. Quadrature modulator, 810 ... upconverter control circuit, 811 ... step-down element control circuit, 211 ... upconverter, 212 ... step-down element, 213, 301 ... DC power supply, 302 ... inductance L, 303 ... FET switch, 304 ... rectifier diode D 405, 605... Upconverter control delay, 406 503, 606 ... output voltage waveform of the up converter, 407, 504, 607 ... output voltage waveform of the step-down element, 401, 601 ... transmission power control cycle, 402 ... transmission power control step, 403 ... up converter control output margin, 404 ... Location where power control becomes positive continuously for 2 times or more, 408: Location where power control changes from positive to negative, 409: Location where power control becomes negative continuously for 2 times or more, 408: Power control changes from negative to positive 501 ... 602 (PAPR (peak value versus average value of output power)), 502 ... boost section, 603 ... average power control level, 604 ... boost switching threshold, 701 ... IQ baseband signal, 702 ... peak hold Circuit 703 ... Boost switching judgment circuit 704 ... Delay element 804 ... Phase comparator 805 ... RF VCO, 807 ... IF local oscillator, 808 ... mixer.

Claims (11)

A wireless communication device,
A baseband unit that performs baseband processing of a transmission signal;
The transmission signal input from the baseband unit is separated into a phase signal and an amplitude signal, the phase signal is output, and the control signal of the first potential difference generator and the control of the second potential difference generator are based on the amplitude signal. A conversion unit that converts the signal into a signal and outputs the signal;
A radio unit that amplifies the phase signal input from the conversion unit according to the transmission output and outputs the amplified signal to the front end unit;
A front end unit that outputs a signal output from the radio unit to an antenna;
The radio unit includes a quadrature modulator that frequency-converts the phase signal input from the conversion unit, a power amplifier that amplifies the frequency-converted signal and outputs the amplified signal to the front end unit, and a first potential difference generator An amplitude modulation circuit that changes a control voltage for controlling the power supply voltage of the power amplifier based on the control signal of the second potential difference generator and the control signal of the second potential difference generator,
The amplitude modulation circuit is controlled so as to step down the power supply voltage of the power amplifier and, if necessary, the first potential difference generator for generating a control voltage so as to boost the power supply voltage of the power amplifier. A combination of a second potential difference generator for generating a voltage;
Based on the amplitude signal, transmission power level information, and transmission channel parameter setting information, the converter converts the first potential difference generator control signal and the second potential difference to the first and second potential difference generators. A wireless communication device that generates a control signal for a generator. The wireless communication device according to claim 1,
The first potential difference generator has better power conversion efficiency than the second potential difference generator,
A wireless communication device characterized in that the second potential difference generator uses a device whose output voltage variable speed is faster than that of the first potential difference generator. The wireless communication device according to claim 1,
When generating the control signal for the first potential difference generator and the control signal for the second potential difference generator ,
A radio communication apparatus characterized in that as a transmission channel parameter, reference is made to a modulation scheme to be used, the number of channels multiplexed and transmitted simultaneously, a transmission power ratio between channels, each channel output, and a bit adjustment method for the combined output. The wireless communication device according to claim 1,
It is used in a wireless communication system that performs closed-loop transmission power control,
Following the closed-loop transmission power control with the control voltage control using the first potential difference generator,
Control the instantaneous fluctuation of the envelope by the control voltage control using the second potential difference generator,
Based on the control voltage of the first potential difference generator , (desired average transmission power level + maximum value of the instantaneous fluctuation width of the envelope) as a target value, the transmission power is always kept at a value equal to or higher than the desired average transmission power level,
A wireless communication apparatus that reduces transmission power to a predetermined value based on a control voltage of the second potential difference generation apparatus. The wireless communication device according to claim 4,
In the case of increasing the power continuously for 2 control cycles or decreasing the power continuously for 2 control cycles by transmission power control,
The control voltage of the first potential difference generator is controlled earlier than the transmission power control timing defined in the standard of the wireless communication system according to the output voltage variable speed of the second potential difference generator,
When the control direction of transmission power control changes from plus to minus or from minus to plus, the value before one control cycle is held as it is as the target value of the control voltage of the first potential difference generator. A wireless communication device. The wireless communication device according to claim 1 ,
Whether or not boosting is performed is determined by comparing the level of the transmission signal output from the baseband unit with a predetermined threshold, and the delay due to the determination process is also delayed by the same amount for the transmission signal. A wireless communication apparatus that performs correction. The wireless communication device according to claim 6 ,
A wireless communication apparatus that reduces a control load by determining whether or not to perform boosting only once in a fixed control cycle instead of sequentially. The wireless communication device according to claim 6 ,
A wireless communication apparatus characterized by stopping or halting boost determination itself when a period during which boost is not performed continues due to parameter conditions related to boost determination. A wireless communication device according to any one of claims 1 to 8 ,
A radio communication apparatus, wherein the conversion unit is integrated on the same circuit or module as any one of the baseband unit, the quadrature modulator, and the amplitude modulation circuit. A wireless communication device according to any one of claims 1 to 8 ,
A radio communication apparatus, wherein the amplitude modulation circuit is integrated on the same circuit or module as either the quadrature modulator or the power amplifier. An integrated circuit that controls amplification of a transmission signal that is input from a baseband unit and output to a front end unit in a wireless communication device,
The transmission signal input from the baseband unit is separated into a phase signal and an amplitude signal, the phase signal is output, and the control signal of the first potential difference generator and the control of the second potential difference generator are based on the amplitude signal. A conversion unit that converts the signal into a signal and outputs the signal;
A quadrature modulator that converts the frequency of the phase signal input from the converter;
A power amplifier that amplifies the frequency converted signal and outputs the amplified signal to the front end;
An amplitude modulation circuit that changes a control voltage for controlling the power supply voltage of the power amplifier based on a control signal of the first potential difference generator and a control signal of the second potential difference generator;
A first potential difference generator for generating a control voltage so as to boost the power supply voltage of the power amplifier as necessary, based on the amplitude signal, transmission power level information, and transmission channel parameter setting information; A control signal for the first potential difference generator and a control for the second potential difference generator for controlling the second potential difference generator for generating a control voltage so as to step down the power supply voltage of the power amplifier as required. An integrated circuit characterized by generating a signal.

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