JP2004260253A - Wireless transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless transmitter whereby an offset inputted to an orthogonal transform unit is adjusted with high accuracy. <P>SOLUTION: The wireless transmitter including the orthogonal transform unit includes: a digital / analog converter for converting I, Q components of a digital baseband signal respectively into an analog baseband signal; a digital compensation unit for inputting a digital offset value to the digital / analog converter; and an analog compensation unit for inputting an analog offset value to each of low-pass filters for I, Q components for receiving output signals of the I, Q components from each digital / analog converter, and uses them in parallel to adjust the offset value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radio transmitter, and more particularly, to a radio transmitter using an orthogonal transformer, which has improved adjustment accuracy when adjusting offset values of I and Q components of a baseband signal.
[0002]
[Prior art]
FIG. 4 is a schematic diagram schematically showing a radio transmitter in the case of a conventional FDD (Frequency Division Duplex) system based on a demodulation system such as a four-phase phase modulation (QPSK, Quadrature Phase Shift Keying) or the like.
A baseband signal converted into a digital signal having I and Q2 components (hereinafter, referred to as a digital baseband signal) is converted into two sets of analog signals, I, I} and D / A converters (DACI 202, DACQ 204), respectively. After being converted into Q, Q￣ (hereinafter, a signal converted into an analog signal is referred to as an analog baseband signal), it is input to the low-pass filter 206 and the low-pass filter 208, respectively. Here, I￣ and Q￣ represent the opposite phase signals of I and Q, respectively.
[0003]
The analog baseband signals that have passed through the low-pass filters 206 and 208 are input to a quadrature transformer 210, multiplied by a desired carrier, and then amplified by a voltage gain controller (VGA) 212 to form a band-pass filter 214 and a power amplifier. The signal is output from the antenna via a duplexer (DUP) 220 that transmits a received signal to the receiving unit 222 at the same time via the power detector 216 and the power detector 218.
[0004]
At this time, if there is an offset in the input signal of the orthogonal transformer 210, that is, if some DC voltage is applied as a signal component, even in the case of a non-transmitted signal, the carrier frequency is just set at the antenna end. The offset, that is, an extra signal is detected. Therefore, it is necessary to devise the orthogonal transformer 210 to remove the offset signal, but conventionally, for example, by applying a voltage to the low-pass filter units 206 and 208 or the output unit of the DAC to obtain a difference from the signal voltage. The offset signal was deleted.
[0005]
For example, the orthogonal transformer 210 processes a difference between I and I￣ converted into an analog signal by the DACI 202 as a voltage signal. At the time of non-transmission, since the voltage of I and I 通常 is usually the same, the difference between I and I￣ is 0. However, as described above, when a DC voltage is applied, this difference does not become zero even in the case of no transmission.
Therefore, a predetermined voltage is applied from the compensators 224 and 226 to the low-pass filters 206 and 208, respectively, so that the difference between I and I￣ and between Q and Q￣ is adjusted to 0 when no transmission is performed. I have.
[0006]
[Problems to be solved by the invention]
However, in the high-speed data communication standard represented by the third generation, high-speed data communication is considered in mind, and therefore, parts used are required to have higher accuracy than the second generation.
In particular, a 10-bit precision DAC is newly used as a digital / analog converter (DAC) in the transmission system. In this case, the offset adjustment accuracy is also required to be 1 LSB (equivalent to 1 to 2 mV). In the case where the offset adjustment is performed using an analog value as in the above-described conventional example, another DAC having the same accuracy is required, which is expensive.
In addition, such adjustment of the analog offset needs to be finely compensated according to, for example, temperature characteristics during energization, and also needs to be compensated during a call.
In addition, variations in the offset due to the analog circuit for each individual circuit and changes due to the operating environment (battery voltage, temperature), etc., are also significant.
[0007]
It is also possible to measure the transmission power with the power detector 218 and individually adjust the analog offset values input to the low-pass filters 206 and 208 from the compensators 224 and 226. Is difficult to satisfy.
[0008]
Further, since the accuracy of the power detector 218 is about 20 dB to 30 dB in the dynamic range, the transmission power measured by the power detector 218 is an insensitive index to be used for detecting the offset amount. It has been desired to detect the offset itself using a baseband signal that is sensitive to the offset.
[0009]
The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a wireless transmitter capable of adjusting an offset value input to an orthogonal transformer with high accuracy.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problem, a first aspect of the present invention is a wireless transmitter having an orthogonal transformer, wherein the digital / digital converter converts I and Q components of a baseband signal from a digital signal to an analog signal. A digital compensator for inputting a digital offset value to the analog converter, and an analog offset for each of the I and Q component low-pass filters to which the I and Q component output signals from the respective digital / analog converters are input. A wireless transmitter having an analog compensator for inputting a value and adjusting an offset value by using them in combination.
[0011]
Preferably, the digital compensator has a register for holding a digital offset value and a register controlled by a CPU, and switches between these registers at a predetermined timing.
[0012]
Preferably, the analog compensator has a register for holding an analog offset value, and inputs the same analog offset value to each of the I and Q component low-pass filters.
[0013]
Similarly, in order to solve the above-described problem, a second aspect of the present invention is a wireless transmitter having an orthogonal transformer, which converts I and Q components of a baseband signal from a digital signal to an analog signal, respectively. A digital compensator for inputting a digital offset value to a digital / analog converter, a means for demodulating its own transmission signal by a demodulation means, and detecting the power and demodulation accuracy from the demodulated signal and performing the digital compensation. Control means for adjusting and controlling the offset value of the transmitter.
[0014]
Further, it is preferable that the transmission signal is demodulated in a non-transmission section where no transmission data exists during a transmission operation of the wireless transmitter.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a wireless transmitter of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
[0016]
FIG. 1 is a block diagram illustrating a schematic configuration of the wireless transmitter according to the first embodiment of the present invention.
As shown in FIG. 1, the radio transmitter according to the present embodiment includes a digital / analog converter (Digital Analog Converter) DACI2, DACQ4, low-pass filters 6, 8, a quadrature converter 10, a variable gain amplifier (VGA) 12, It comprises a bandpass filter 14, a power amplifier 16, a power detector 18 and a duplexer 20, and the duplexer 20 is connected to a receiving unit 22.
[0017]
In addition, the radio transmitter according to the present embodiment is different from the above-described configuration in that digital compensators 30 and 32 that input digital offset values to DACI2 and DACQ4 that convert digital baseband signals into analog baseband signals, respectively. And an analog compensator 34 for inputting an analog offset value to each of the low-pass filters 6 and 8. Further, the wireless transmitter has a CPU 36 for controlling these components.
[0018]
DACI2 converts the I component of the digital baseband signal into an analog signal, and DACQ4 converts the Q component of the digital baseband signal into an analog signal.
The low-pass filter 6 receives the I and I components of the analog baseband signal, and the low-pass filter 8 receives the Q and Q components of the analog baseband signal.
[0019]
The orthogonal transformer 10 orthogonally transforms a carrier having a predetermined frequency with the I component and the Q component of the analog baseband signal that has passed through the low-pass filters 6 and 8, respectively. The converted signal is amplified by a power amplifier (PA) 16 through a variable gain amplifier (VGA) 12 and a band-pass filter 14, and then output from an antenna via a duplexer 20.
[0020]
The digital compensator 30 is for adjusting the offset for the I component of the digital baseband signal, and the digital compensator 32 is for adjusting the offset for the Q component of the digital baseband signal.
The digital compensator 30 has a register 30a for holding a digital offset value (gain adjustment value GI (1) and offset adjustment value OFI (1)), and a register 30b controlled by the CPU.
Similarly, the digital compensator 32 has a register 32a for holding a digital offset value (gain adjustment value GQ (1) and offset adjustment value OFQ (1)), and a register 32b controlled by the CPU 36. .
[0021]
The analog compensator 34 inputs the same analog offset value to each of the low-pass filters 6 and 8 for the I and Q components of the analog baseband signal, and has a register 34a for holding the analog offset value. I have.
The analog compensator 34 further includes a TXAGC DAC (transmission AGC) 34b, a communication output monitoring AGC 34c, and a time detector 34d. The detection data of the transmission power detected by the power detector 18 is input to the communication output monitoring AGC 34c. The output of the time detector 34d is input to the registers 30a, 30b, 32a, 32b of the digital compensators 30, 32. The CPU 36 switches between the two registers 30a and 30b and 32a and 32b at a predetermined timing according to the detection signal.
[0022]
Hereinafter, the operation of the present embodiment will be described.
The I component of the digital baseband signal is input to the digital compensator 30, and the Q component of the digital baseband signal is input to the digital compensator 32. In the digital compensator 30, the digital baseband signal I component is multiplied by the gain adjustment value GI (1) held in the register 30a (or the register 30b), and the offset adjustment value OFI (1) is added. You. Thereafter, the I component of the digital baseband signal output from the digital compensator 30 is input to the DACI 2, converted into the I and I￣ components of the analog baseband signal, and input to the low-pass filter 6.
[0023]
Similarly, in the digital compensator 32, the digital baseband signal Q component is multiplied by the gain adjustment value GQ (1) held in the register 32a (or the register 32b), and the offset adjustment value OFQ (1) Is added. Thereafter, the digital baseband signal Q component output from the digital compensator 32 is input to the DAC Q4, converted into analog baseband signals Q and Q￣ components, and input to the low-pass filter 8.
[0024]
For example, when the DAC processes a 10-bit digital signal, it takes a value of 0 to 1023 as the entire area of the signal. Since the difference between the output voltage corresponding to the maximum value and the minimum value is about 1 V, it is necessary to control the offset value about every 1 mV. In this case, the possible range of the offset value is, for example, a value of ± 64, and this offset value is held in the registers 30a and 32a. The registers 30b and 32b are controlled by the CPU 36. The CPU 36 switches between the registers 30a and 30b and the registers 32a and 32b at a predetermined timing, for example, at the beginning of a radio frame, or stores the data in the registers 30b and 32b. By transferring the offset amount to the registers 30a and 32a, the offset amount according to the time is compensated.
[0025]
The I and I components of the analog baseband signal are input to the low-pass filter 6, and the Q and Q components of the analog baseband signal are input to the low-pass filter 8. At this time, the same analog offset value (analog offset voltage) is input from the analog compensator 34 to the low-pass filters 6 and 8 at the same time.
As described above, in the present embodiment, the digital compensators 30 and 32 and the analog compensator 34 are used in combination. Conventionally, it is necessary to input analog offset values separately for the I and Q components, but in the present embodiment, only one adjustment of the analog offset is required.
[0026]
The signals that have passed through the low-pass filters 6 and 8 are input to an orthogonal transformer 10, where they are orthogonally transformed, and then output as transmission signals from an antenna via a VGA 12, a band-pass filter 14, a power amplifier 16 and a duplexer 20. The transmission power of the signal amplified by the power amplifier 16 is detected by the power detector 18, and the detected data is input to the communication output monitoring AGC 34 c of the analog compensator 34 and used for offset adjustment.
[0027]
As described above, in the present embodiment, the digital baseband signal is input to the DACs (DACI2, DACQ4) via the offset compensators (digital compensators 30 and 32), and the output of the analog compensator 34 is input to the low-pass filter 6. , 8. As described above, by using the digital compensators 30 and 32 and the analog compensator 34 together, the required accuracy of the analog compensator can be reduced as compared with a compensator using a conventional analog circuit.
That is, by performing coarse adjustment of the analog compensator and fine adjustment (fine adjustment) by the digital compensator, the adjustment can be performed with high accuracy.
[0028]
In addition, by using the digital compensator, it is possible to quickly compensate for the offset adjustment in units of 1 LSB, which is the accuracy limit of the DAC, in units of time of one system clock. For example, when the required specification is ± 2 mV, the control by the conventional analog compensator is about ± 30 mV. However, by performing the control by the digital compensator as in the present embodiment, 1 LSB (± 1 mV) is obtained. Can be controlled.
Further, since the I and Q components can be individually and precisely adjusted by the digital compensators 30 and 32, the same analog compensation voltage is applied to the low-pass filters 6 and 8 for both the I and Q components as described above. It becomes possible.
[0029]
Next, a second embodiment of the present invention will be described.
FIG. 2 shows a schematic configuration of a wireless transmitter according to the second embodiment. The wireless transmitter of the second embodiment detects the transmission power and the demodulation accuracy by actually demodulating the transmission signal in the receiving unit 122, and performs offset adjustment control by feeding back such information to the digital compensator. Things.
[0030]
As shown in FIG. 2, similarly to the first embodiment, the radio transmitter according to the second embodiment processes digital / analog converters DACI 102 and DACQ 104 to process a digital baseband signal having an I component and a Q component. , A low-pass filter 106, a quadrature converter 110, a variable gain amplifier (VGA) 112, a band-pass filter 114, a power amplifier 116, and a duplexer 120, and further converts a digital baseband signal to an analog baseband signal. And DACQ 104 are provided with digital compensators 130 and 132 for inputting digital offset values, respectively.
[0031]
Further, the digital compensators 130 and 132 have registers 130a and 132a, respectively, for holding digital offset values (gain adjustment values and offset adjustment values). After the digital baseband signal is multiplied by the gain adjustment value, the offset adjustment value is added.
[0032]
In the first embodiment, the transmission power of the transmission signal is detected by the power detector 18. However, in the present embodiment, the power compensator is not provided, and the transmission signal is actually demodulated by the receiving unit. Feedback to
That is, a switch 121 for directly extracting a transmission signal without passing through the duplexer 120 is provided, and a circuit for demodulating the transmission signal in the same manner as a normal reception signal is provided.
[0033]
Although such a circuit is not particularly limited, in the present embodiment, as shown in FIG. 2, a transmission signal captured via the switch 121 is a low noise amplifier (LNA, Low Noise Amplifier) 140 ( Alternatively, after being input to an attenuator ATT), it passes through a band-pass filter 142 and is converted into I and Q components by a quadrature transformer 144. After passing through low-pass filters 146 and 148, each component is converted into an analog / digital converter. The signal is converted into a digital signal by the (ADCI 150, ADCQ 152) and demodulated by the demodulator 154.
[0034]
The power and demodulation accuracy of the demodulated signal are detected, and the detected data is input to the transmission gain / offset control means 156. The transmission gain / offset control unit 156 performs offset adjustment control by feeding these information back to the digital compensators 130 and 132 and reflecting the information on the offset value (gain adjustment value, offset adjustment value).
[0035]
In this case, the demodulator, the analog / digital converter, the low-pass filter, and the other RF circuit may use a conventional receiving system circuit as it is.
For example, in the third generation mobile communication standard by 3GPP, there is no transmission data called GAP which is in use during a call for handover or the like for downlink (DL) and uplink (UL). There is a non-transmission section.
[0036]
For example, as shown in FIG. 3, when there is a GAP in both the downlink and the uplink at the same time and the uplink is not transmitting, the receiving circuit of the mobile device is operated at the transmission frequency and the DC component of the baseband is reduced. Measure. Thus, the offset voltage can be directly obtained, and the offset adjustment control can be performed by performing feedback to the digital compensator so as to minimize the value.
[0037]
As described above, in the present embodiment, by adjusting the accuracy of adjustment and performing temperature correction and the like by receiving and demodulating its own transmission signal. That is, by operating the receiving circuit (the demodulation circuit of the transmission signal) of the present embodiment at the time of the GAP, it is possible to perform the adjustment corresponding to the temperature and the voltage change during use.
[0038]
As described above, according to the present embodiment, the transmission signal is received by itself, so that the power can be detected with higher accuracy than that detected by a power detector or the like.
In a conventional example using a power detector, the same adjustment can be performed as long as no transmission is performed. However, in the case of a GAP or the like, the operation of the power detector is expected to be delayed. On the other hand, according to the method of the present embodiment, it is possible to use GAP during a call.
Note that the output signal of the VGA 12 may be input to the orthogonal transformer 144 and demodulated as indicated by a broken line in FIG.
[0039]
As described above, the wireless transmitter according to the present invention has been described in detail, but the present invention is not limited to the above embodiments, and various improvements and changes are made without departing from the scope of the present invention. Of course it is good.
[0040]
【The invention's effect】
As described above, according to the present invention, it is possible to adjust the offset value input to the orthogonal transformer with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a wireless transmitter according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a schematic configuration of a wireless transmitter according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a state of a radio frame.
FIG. 4 is a block diagram illustrating a schematic configuration of an example of a conventional wireless transmitter.
[Explanation of symbols]
2,102 Digital / analog converter (DACI)
4,104 Digital / analog converter (DACQ)
6, 8, 106, 108, 146, 148 Low-pass filter 10, 110, 144 Quadrature transformer 12, 112 Variable gain amplifier (VGA)
14, 114, 142 Bandpass filter 16, 116 Power amplifier 18 Power detector 20, 120 Duplexer 22, 122 Receiver 30, 32, 130, 132 Digital compensator 30a, 30b, 32a, 32b, 34a, 130a, 132a Register 34 Analog compensator 34b DAC for TXAGC
AGC for communication output monitor
34d time detector 36 CPU
140 Low Noise Amplifier (LNA)
150 Analog / Digital Converter (ADCI)
152 Analog / Digital Converter (ADCQ)
154 demodulator 156 transmission gain / offset control means

Claims (5)

A wireless transmitter having an orthogonal transformer,
A digital compensator for inputting a digital offset value to a digital / analog converter for converting I and Q components of a baseband signal from a digital signal to an analog signal, respectively;
An analog compensator for inputting an analog offset value to each of the low-pass filters for the I and Q components, to which the output signals of the I and Q components from the respective digital / analog converters are respectively input;
And a wireless transmitter that adjusts an offset value by using these together. The wireless transmitter according to claim 1, wherein the digital compensator has a register for holding a digital offset value and a register controlled by a CPU, and switches between these registers at a predetermined timing. The wireless transmitter according to claim 1, wherein the analog compensator has a register for holding an analog offset value, and inputs the same analog offset value to each of the I and Q component low-pass filters. A wireless transmitter having an orthogonal transformer,
A digital compensator for inputting a digital offset value to a digital / analog converter for converting I and Q components of a baseband signal from a digital signal to an analog signal, respectively;
Means for demodulating its own transmission signal by demodulation means,
Control means for detecting the power and demodulation accuracy from the demodulated signal, and adjusting and controlling the offset value of the digital compensator,
A wireless transmitter, comprising: The radio transmitter according to claim 4, wherein the transmission signal is demodulated in a non-transmission section where no transmission data exists during a transmission operation of the radio transmitter.

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