JP2004260509A - Radio communication device and integrated circuit used for it - 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&NCIPI

Description

[0001]
TECHNICAL FIELD 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, the present invention is suitable for a wireless communication device of a wireless communication system that employs a modulation method of transmitting information by changes in both phase and amplitude.
[0002]
[Prior art]
2. Description of the Related 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 changes in both phase and amplitude is often used. In this modulation method, if the waveform of the transmission signal is distorted, the data cannot be correctly determined on the receiving side, so that a transmission power amplifier that amplifies the signal requires high linearity. Conventional wireless communication terminals have met this requirement by using linear amplifiers, but linear amplifiers have poor power efficiency. Therefore, the inventors of the present invention combined Japanese Patent Application No. 2002-259526 filed by the present applicant and combined an EER (Envelope Elimination and Restoration) system with a conventional linear amplifier system, thereby achieving an efficient saturation amplifier even for a mobile phone having a wide output dynamic range. A configuration that can be used was proposed.
[0003]
As a method of further expanding the output dynamic range, for example, an up converter is used in an EER type power supply voltage control circuit described in Non-Patent Document 1, and the power supply voltage is temporarily increased to increase the power supply voltage. Is known. In the saturation amplifier used in the EER method, the power supply voltage Vdd and the output voltage Vout are proportional, and Vout is changed by controlling Vdd. However, when Vdd falls to a certain level or less, the transistor inside the amplifier does not operate. The problem is that the control range is narrower than a linear amplifier that controls Vout with the input voltage Vin. By boosting 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 up-converter. 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 using a switch 303 such as an FET, and the energy stored in the inductance L302 is extracted by a rectifier diode D304. To obtain an output voltage higher than the original power supply voltage. There are also switched-capacitor upconverters that store energy in capacitance instead of inductance.
[0005]
[Patent Document 1] US Pat. No. 6,377,784 [Non-Patent Document 1] Ranjan Et. Al, “Microwave Power Amplifiers with Digitally-controlled Power Supplied Voltage for High Efficiency and High Energy Linearity”, 2000 IE SIE Dies
[Non-Patent Document 2] Yamawaki et. al, "A 2.7-V GSM RF transfer sever IC", IEEE Journal of Solid-State Circuits vol. 32, Issue 12, pp. 2089-2096, Dec. 1997
[0006]
[Problems to be solved by the invention]
Upconverters store energy in inductance or capacitance and rectify and boost their output, causing a slight delay until the output voltage rises to the desired voltage. If the responsiveness is increased, the amount of stored energy is correspondingly reduced, and a high voltage or current cannot be generated. In order to expand the control range, it is necessary to control not only the power supply voltage but also the power supply voltage.
[0007]
[Means for Solving the Problems]
The present invention provides a power supply voltage control circuit for an EER system having a wide control range and a high response by configuring an up converter in combination with a step-down element (a regulator or the like) having a high response. Also, a method of analyzing transmission signal waveform information prior to output from a power amplifier, determining whether boosting is necessary, and generating a control signal to each element will be described.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the configuration of a general terminal used in a wireless communication system will be described with reference to FIG. The reception signal received from the antenna 107 is transmitted / received and separated by an antenna switch (or duplexer) in the front end unit 101, filtered, and then subjected to frequency conversion in the radio unit 102 to be dropped to a baseband band. Further, the signal is converted into a digital signal in the interface unit 103, demodulated in the baseband unit 104, output through the user interface unit 105, and provided 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 undergoes modulation processing 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 frequency in a desired frequency band in the radio 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 for each unit, manage timing, and the like. The present invention particularly relates to a circuit configuration method of a radio 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. Things. The interface unit 103 can be physically configured as a part of the baseband unit 104, a part of the RF-IC 108, or a 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 as an EER-type power amplifier module.
[0009]
Next, a first embodiment of the configuration of the transmission radio section and the interface section according to the present invention will be described with reference to FIG. In the present embodiment, the IQ → EER conversion unit 202 of the interface unit 201 is placed before the DACs 204 to 206, and the function is realized by digital signal processing. If the functions are equivalent, the same effect can be obtained even if the functions are realized by analog signal processing. The IQ → EER conversion unit 202 separates and extracts amplitude information and phase information. Although the phase information is represented only by the phase angle θ in the conventional EER method, in the present embodiment, the phase information is represented by an IQ orthogonal component projected on a unit circle and output to the RF-IC 207. Since the IQ quadrature components on the unit circle always have a constant amplitude value when synthesized, they have no amplitude information. However, since the frequency can be converted in the same manner as the IQ quadrature components in the case of the conventional linear system, the conventional RF-IC The advantage is that the circuit configuration technology (quadrature modulator, filter, etc.) can be easily used (for details, refer to 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. Although the IQ notation on the unit circle and the frequency conversion by the quadrature modulator are used here, 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. The up-converter 211 and the step-down element 212 are connected in series to the DC power supply Vdd 213, and control the power supply voltage for driving the power supply voltage pin of the power amplifier 209. Since the output voltage of the saturation power amplifier 209 basically changes in proportion to the power supply voltage, envelope modulation of the output signal can be performed by controlling the power supply voltage. Even if voltage control is applied to not only the power supply voltage side terminal of the power amplifier but also the ground side terminal, the same effect can be obtained as long as 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, with reference to FIG. 8, a description will be given of a second embodiment of the configuration of the transmission system radio unit and the interface unit according to the present invention. In this embodiment, the offset PLL method (see Non-Patent Document 2) is used for the RF-IC 802. The input signal from the interface unit 801 is frequency-converted into an IF frequency band by the quadrature modulator 803, and the result of IQ synthesis 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, is divided by a coupler, is multiplied by a local signal 807 of IF frequency by a mixer 808, and is fed back to a 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. As a result, the processing load on the EER control unit 807 can be reduced. The separation conversion processing can be performed in the baseband unit. The output signal of the power amplifier 806 is divided by the coupler and fed back to the EER control unit 809. A configuration that returns the feedback signal 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 part 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. In a wireless communication system using OFDM (Orthogonal Frequency Division Multiplexing) such as IEEE802.11a, PAPR501 (Peak to Average Power Ratio: the peak value to the average value of output power) is 12 to 17 dB. To apply the EER method to a system in which the instantaneous change width of the transmission output is wide, it is necessary to make the power supply voltage control width of the power amplifier as wide as possible. However, the power supply voltage change width of the power amplifier is usually about 2 to 3 V. In order to control the transmission output to change by 12 dB (about 15 times) within this width, it is necessary to make the slope of the power supply voltage-transmission output characteristic steep, which is difficult to realize. In this embodiment, the upconverter 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 where the transmission power is significantly larger than the average value, and , A high-speed envelope modulation is performed by lowering the control voltage to a 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]
FIG. 7 shows a configuration example of a circuit necessary for determining the range of the boosting section 502. The IQ transmission signal 701 modulated in the baseband unit is synthesized, and the peak hold circuit 702 detects the maximum value of the baseband signal. In step 703, the boost switching threshold value and the maximum output value are compared. If the threshold value is equal to or higher than the threshold value, boost On is selected. If the threshold value is equal to or smaller than the threshold value, boost Off is selected. . In order to correct the processing delay of the blocks 702 and 703 and the processing circuit delay Tdc of the subsequent EER control unit 110, it is necessary to delay the transmission signal input 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 in terms of configuration.
[0013]
Next, a second embodiment of the 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 differs in the method of determining the boosting section. In the first embodiment, transmission output waveforms are successively compared and boosted only in a necessary section. On the other hand, in the present embodiment, whether or not boosting is performed is determined only once in a transmission power control cycle. Boosts the entire control cycle section 601. By reducing the number of times the boosting section is determined, the power efficiency is slightly reduced, but the processing load is reduced, so that the power consumption of the control circuit is reduced. Further, it is also possible to realize a configuration in which the baseband unit 104 determines the boosting section and the interface unit 103 only follows the control signal in terms of the control cycle. The determination as to whether or not to boost the voltage in a certain control cycle section 601 is made based on the channel setting during transmission (the modulation method to be used, the number of channels to be multiplexed and transmitted at the same time, the power ratio between channels, the bits for each channel output and the combined output). Adjustment method, etc.) and the average control level value 603. When the maximum PAPR value 602 + the average control level value 603 <the boost switching threshold value 604, the boosting is turned off, and when the maximum PAPR value 602 + the average transmission power control level value 603 ≧ the boosting switching threshold value 604, the boosting is turned on. In the case where the boosting OFF section continues due to the channel setting condition, the operation of the determination circuit itself is stopped or stopped unless a parameter related to the above-mentioned determination formula is changed. The up-converter requires a circuit delay Tdc from the start of the control until the output voltage actually rises. Therefore, the up-converter starts the control by Tdc 605 before the timing at which the transmission power control is actually desired to be performed. Conversely, when returning to the original state, 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 the 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 base station and a terminal monitor each other's wireless communication status and perform closed-loop transmission power control so that communication can be performed with appropriate power. In the example of W-CDMA (DS-FDD system of the 3GPP standard), the transmission power of the wireless terminal is set to ± 1 power control step 402 (normal transmission) in accordance with the timing at the beginning of the slot every control cycle 401 (1 slot = 667 μs). In the case of = 1 dBm). A method corresponding to the 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 the transmission power is increased continuously twice or more)
In the present embodiment, the up converter controls the power supply voltage to be constant at a value higher than the required power supply voltage control value for obtaining the required transmission power as a result of the control, and reduces the control voltage to the required value by the step-down element. Thus, high-speed envelope modulation is performed. It is desirable that the up-converter control margin 403 be approximately equal to the PAPR determined by the modulation scheme of the transmission signal. In the process of the transmission power control, if the power control is performed in the positive (increase) direction twice consecutively (404 in the figure), the timing of the up-converter is increased by Tdc (405) time before the transmission power is actually increased. Start control. The output voltage waveform of the up-converter is shown at 406, and the average output voltage level of the step-down element is shown at 407.
[0016]
(2) When the transmission power is reduced by one power control step (when the power changes from plus to minus)
In the process of transmission power control, when the power control changes from plus (increase) to minus (decrease) (408 in the figure), it is not possible to decrease the transmission power prior to the actual timing of decreasing the transmission power as in the case of increasing the power. The control voltage of the up-converter keeps the same output level as the previous one in the next transmission power control cycle period, and responds by increasing the amount reduced by the step-down element.
[0017]
(3) When the transmission power is reduced by one power control step (when the power is continuously reduced two or more times)
In the process of transmission power control, when the value is negatively (lowered) twice or more consecutively (409 in the figure), the control voltage of the up-converter is reduced by the control step in accordance with the timing of actually reducing the transmission power. Since the control margin of the up-converter has a margin for one control step in the step (2), the operation can be performed before the actual change point.
[0018]
(4) When raising the transmission power by one power control step (when turning from minus to plus)
In the process of the transmission power control, when the power control changes from minus (lower) to plus (up) (410 in the figure), the control voltage of the up converter keeps the same output level in the next transmission power control cycle period as in the previous time. This is addressed by reducing the amount that is reduced by the step-down element. (2) Since the control margin of the upconverter has a margin of one control step at the stage of (3), it is not necessary to newly increase the power.
[0019]
In each of the embodiments of the present invention, an up converter is described as an example. However, a more efficient circuit can be realized by using an up / down converter capable of boosting and stepping down. The control method according to 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】
The present invention provides a power supply voltage control circuit for an EER system having a wide control range and a high response by configuring an up converter in combination with a step-down element having a high response.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a general terminal used in a wireless communication system.
FIG. 2 is a diagram showing a first embodiment of the configuration of a transmission system radio unit / interface unit according to the present invention;
FIG. 3 is a diagram showing a circuit configuration of a general upconverter.
FIG. 4 is a diagram showing a third embodiment of the 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 the transmission power control according to the present invention.
FIG. 7 is a diagram showing a boost determination process of transmission power control according to the present invention.
FIG. 8 is a diagram showing a second embodiment of the configuration of a transmission system radio unit / interface unit according to the present invention.
[Explanation of symbols]
101: Front end unit, 102: Wireless unit, 103, 202, 708, 801: Interface unit, 104, 707: Baseband unit, 105: User interface unit, 106: Control unit, 107: Antenna, 108, 207 , 802 RF-IC, 109, 209, 806 power amplifier, 110, 210, 809 EER control unit, 202, 705 IQ → EER conversion unit, 203, 204, 205, 206 DAC, 208, 803 Quadrature modulator, 810: Up converter control circuit, 811: Step-down element control circuit, 211: Up converter, 212: Step-down element, 213, 301: DC power supply, 302: Inductance L, 303: FET switch, 304: Rectifying diode D , 405, 605 ... control delay of up-converter, 40 , 503, 606 ... up converter output voltage waveforms, 407, 504, 607 ... step-down element output voltage waveforms, 401, 601 ... transmission power control cycle, 402 ... transmission power control step, 403 ... up converter control output margin, 404 ... A place where the power control becomes positive twice or more consecutively, 408... A place where the power control changes from plus to minus, 409... A place where the power control becomes minus two or more times continuously, and 408. Turning point, 501, 602... PAPR (peak value vs. average value of output power)), 502... Boost section, 603... Average power control level, 604... Boost switching threshold, 701... IQ baseband signal, 702. Hold circuit, 703 boost switching determination circuit, 704 delay element, 804 phase comparator, 805 RF-VCO, 807 ... IF local oscillator, 808 ... mixer.

Claims (11)

An integrated circuit that amplifies a transmission signal input from a baseband unit in a wireless communication device in accordance with a transmission output and outputs the amplified signal to a front end unit,
A conversion unit that separates the transmission signal input from the baseband unit into a plurality of components and outputs the plurality of components,
A quadrature modulator for frequency-converting the transmission signal input from the baseband unit,
A power amplifier that amplifies the frequency-converted signal and outputs the amplified signal to the front end unit;
An amplitude modulation circuit that modulates a power supply voltage of the power amplifier based on an output from the conversion unit,
A first potential difference generator that boosts a power supply voltage of the power amplifier, if necessary, based on an output from the conversion unit; and an output voltage of the first potential difference generator that drops the amplitude modulation circuit. A combination of a second potential difference generator,
The converter converts the first and second amplitude modulation control signals to the first and second potential difference generators based on the amplitude modulation signal of the transmission signal, transmission power level information and transmission channel parameter setting information, respectively. An integrated circuit characterized by generating. The integrated circuit according to claim 1, wherein
The first potential difference generator has better power conversion efficiency than the second potential difference generator,
An integrated circuit characterized in that a second potential difference generator having a higher output voltage variable speed than the first potential difference generator is used. The integrated circuit according to claim 1, wherein
When generating the first and second amplitude modulation control signals,
An integrated circuit characterized by referring to a modulation scheme to be used, the number of channels to be multiplexed and transmitted at the same time, a transmission power ratio between channels, a bit output method for each channel output and a combined output as transmission channel parameters. The integrated circuit according to claim 1, wherein
It is used in a wireless communication system that performs closed loop transmission power control,
Following the closed loop transmission power control by the amplitude modulation control using the first potential difference generator,
Controlling the instantaneous fluctuation of the envelope by the amplitude modulation control using the second potential difference generator,
On the basis of the first amplitude modulation control signal, (desired average transmission power level + maximum value of instantaneous fluctuation width of the envelope) is always set as a target value and always kept at a value equal to or higher than the desired average transmission power level
An integrated circuit for lowering to a predetermined value based on a second amplitude modulation control signal. The integrated circuit according to claim 4, wherein
When increasing the power for two consecutive control cycles or decreasing the power for two consecutive control cycles by the transmission power control,
Controlling the amplitude modulation control of the first potential difference generator according to the output voltage variable speed of the second potential difference generator earlier than the transmission power control timing defined in the standard of the wireless communication system;
When the control direction of the transmission power control changes from plus to minus or from minus to plus, it is necessary to keep the value one control cycle before as the target value of the amplitude modulation control of the first potential difference generator. An integrated circuit characterized by: The integrated circuit according to claim 1, wherein
An integrated circuit according to the first potential difference generator, wherein a control range is expanded by increasing a control value to a power supply voltage or more. The integrated circuit according to claim 6, wherein
Whether or not to perform boosting is determined by comparing the level of the transmission signal input from the baseband unit with a predetermined threshold, and the delay in the determination process is delayed by the same amount for the transmission signal. An integrated circuit characterized by correcting. An integrated circuit according to claim 6 or claim 7, wherein
An integrated circuit characterized in that a control load is reduced by determining whether or not to perform boosting only once in a fixed control cycle, not sequentially. An integrated circuit according to claim 6 or claim 7, wherein
An integrated circuit characterized in that when a period during which boosting is not performed is continuous according to a condition of a parameter related to boosting determination, the boosting determination itself is stopped or stopped. The integrated circuit according to claim 1, wherein:
An integrated circuit, 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. The integrated circuit according to claim 1, wherein:
An integrated circuit, wherein the amplitude modulation circuit is integrated on the same circuit or module as any one of the quadrature modulator and the power amplifier.

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