JP2007059960A - Transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein hardware and processing become complex since a residual carrier component has been removed by digital signal processing based on programming by using CPUs and DSPs conventionally. <P>SOLUTION: Modulation wave output 10 from an adder 9 is multiplied by the output local oscillation frequency signal of a local oscillator 7 by a multiplier 12. A signal obtained by shifting the local oscillation frequency signal by 90 degrees using a phase shifter 11 is multiplied by the modulation wave output 10 by using a multiplier 13. Harmonics are removed from the output signals of the multipliers 12, 13 by LPFs 14, 15 as subcarrier signals containing offsets and are compared with a "0" level by comparators 16, 17. The integrators 18, 19 integrate the comparison signal to determine whether the offsets are present in either a positive direction or a negative one. The adders 3, 4 add an I-ch signal, a Q-ch signal, and an integral signal to subtract the offsets. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission apparatus, and more particularly to a transmission apparatus that transmits a multicarrier modulated wave modulated by an information signal.

  In a digital wireless communication transmitter, if an offset exists in a baseband signal that is an information signal to be transmitted, a carrier wave leaks into a modulated wave (hereinafter referred to as “residual carrier component” in this specification) and is output. Therefore, it is important to reduce or remove this residual carrier component in order to ensure correct decoding on the reception side and good reception signal quality.

  Therefore, in a transmission apparatus including an orthogonal modulation unit including an I modulation signal mixer, a Q modulation signal mixer, an adder, and a local signal generator, the local leak level included in the orthogonal modulation signal output from the orthogonal modulation unit is reduced. Measure and generate a control signal for reducing the offset component generated in the I modulation signal mixer and the Q modulation signal mixer corresponding to the measurement level, to the I modulation signal mixer and the Q modulation signal mixer. 2. Description of the Related Art Conventionally, a transmission apparatus is known in which offset components generated by an I modulation signal mixer and a Q modulation signal mixer are canceled by supplying the control signal (see, for example, Patent Document 1).

  In addition, in the multi-carrier modulated wave receiver, the residual carrier component is detected as a phase difference from the received I and Q signals including the residual carrier component, and frequency correlation data corresponding to the detected phase difference is generated. A digital Costas loop circuit that generates multiplication data for complex multiplication according to the frequency correlation data and removes the residual carrier component by multiplying the multiplication data with the I signal and Q signal is also known in the art. (For example, refer to Patent Document 2).

  Further, the frequency offset on the receiving side relative to the transmitting side is detected in the detection device based on the baseband including a plurality of carriers arranged on the frequency axis obtained based on the received signal modulated by the multicarrier modulation method and the signal. An apparatus that detects an end point on the frequency axis of a band signal and obtains a frequency offset based on the end point is also known (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 11-27331 JP 2001-103111 A JP 2004-32358 A

  However, the conventional transmission device described in Patent Document 1 uses a central processing unit (CPU) or a digital signal processor (DSP) to remove residual carrier components by digital signal processing based on programming. The problem is that the hardware and the processing become complicated. In addition, it is difficult to adjust an analog circuit such as an amplifier or a filter in a digital wireless communication transmitter.

  On the other hand, the residual carrier component removal methods described in Patent Documents 2 and 3 are both methods in the receiving apparatus, and the residual carrier component in the transmitting apparatus cannot be removed.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission apparatus capable of removing residual carrier components contained in a multicarrier modulated wave with a simple circuit configuration that does not use a CPU or a DSP.

  To achieve the above object, according to a first aspect of the present invention, there is provided a transmitting apparatus for generating and transmitting a modulated wave modulated by a multicarrier modulation method by orthogonally modulating a single carrier with a plurality of subcarrier signals. A signal generating means for generating a first signal and a second signal having a phase difference of 90 degrees from the obtained signal, a modulated wave to be transmitted and the first signal are multiplied to output a first multiplied signal, and modulation is performed. The multiplication means for multiplying the wave and the second signal to output the second multiplication signal, and each level of the first multiplication signal and the second multiplication signal and the predetermined offset 0 level are separately compared in magnitude. Comparator means for outputting the first comparison signal and the second comparison signal, and integrating the first comparison signal to output the first integration signal, and integrating the second comparison signal to obtain the second An integration means for outputting an integration signal, and a first integration signal; And subtracting means for separately subtracting the second integrated signal from the plurality of subcarrier signals, and a single carrier is orthogonally modulated with the signal output from the subtracting means and modulated by the multicarrier modulation method. A modulated wave is generated and transmitted.

  In the present invention, offset components contained in a plurality of subcarrier signals, which are baseband signals, are substantially canceled out by the first and second integrated signals output from the integrating means without using a CPU or DSP. Is done.

  In order to achieve the above object, the second invention generates a modulated wave modulated by a multicarrier modulation method by orthogonally modulating a single carrier wave with an I-ch signal and a Q-ch signal. In a transmitting apparatus for transmitting, a local oscillating means for outputting a local oscillation frequency signal as a single carrier wave, and a first signal for converting the local oscillation frequency signal into a first signal and a second signal having a phase difference of 90 degrees from each other. Phase shift means, first multiplication means for multiplying the first signal and I-ch signal to generate a first multiplication signal, second signal and Q-ch signal multiplied by the second A second multiplying unit that generates a multiplication signal of the first, a summing unit that generates a modulated wave modulated by the multicarrier modulation method by adding the first and second multiplication signals, and a local oscillation frequency signal of 90 degrees to each other. Change to third and fourth signals with different phases A second phase shift means, a third multiplication means for generating a third multiplication signal by multiplying the third signal and the modulated wave output from the addition means, a fourth signal and the addition means The fourth multiplication means for multiplying the output modulated wave to generate the fourth multiplication signal, the level of the third multiplication signal and the predetermined offset 0 level are compared in magnitude, and the first comparison signal is obtained. A first comparison means for generating, a second comparison means for generating a second comparison signal by comparing the level of the fourth multiplication signal with a predetermined offset 0 level, and integrating the first comparison signal The first integration means for generating the first integration signal, the second integration means for integrating the second comparison signal to generate the second integration signal, and the first multiplication means. Supplied to the first subtracting means for subtracting the first integrated signal from the I-ch signal and the second multiplying means From Q-ch signal is obtained with the second integrated signal and configured to have a second subtraction means for subtracting.

  In the present invention, the transmitted multicarrier modulation wave is multiplied by the third and fourth signals (local oscillation frequency signals) output from the same local oscillation means and having a phase difference of 90 degrees from each other, and then again the base The I-ch signal and Q-ch signal, which are band signals, are reproduced, compared with the offset 0 level, and the comparison result is integrated to determine whether the offset exists positively or negatively. As a result, the residual carrier component included in the multicarrier modulated wave can be removed.

  In order to achieve the above object, the present invention removes the harmonics of the third multiplication signal and supplies the first filter means to the first comparison means and the harmonics of the fourth multiplication signal. And a second filter means that is removed and supplied to the second comparison means.

  In order to achieve the above object, the present invention includes a local oscillation means, first and second phase shift means, first to fourth multiplication means, addition means, first and second comparison means, Each of the first and second integrating means and the first and second subtracting means is constituted by a digital circuit. The first and second filter means may be constituted by a digital circuit.

  Further, the present invention includes a local oscillating means, first and second phase shifting means, first to fourth multiplying means, adding means, first and second comparing means, first and second integrating means, The first and second subtracting means, and the first and second filter means constitute a large-scale semiconductor integrated circuit.

  According to the present invention, whether the offset component included in each of the plurality of subcarrier signals, which are baseband signals, is positive or negative is obtained by using the comparison means and the integration means, and this is determined as the transmission base. Since the band signal is subtracted, the residual carrier component contained in the multicarrier modulation wave is greatly reduced or eliminated without using a CPU or DSP. Also, according to the present invention, the CPU or DSP is not used. The simplification of the circuit can be expected. Furthermore, according to the present invention, each circuit is constituted by a digital circuit, and all the control processing is performed digitally, thereby making it possible to make the circuit non-adjustable and to make LSI easy, thereby improving the reliability. it can.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of a transmission apparatus according to the present invention. The present embodiment is a transmission apparatus that generates and transmits a multicarrier modulated wave composed of a plurality of subcarriers. Here, various types of multi-carrier modulation waves have been conventionally known. Here, subcarrier signals that are logically combined in the vicinity of 0 Hz as shown in FIG. 2 are combined using a quadrature modulator. It is the multicarrier modulation wave converted into the radio frequency which made fc the center frequency as shown in FIG. In addition, in multicarrier modulation, it is known that when a baseband signal has an offset, a carrier wave leaks and is output in a modulated wave, and this is called a residual carrier component in this specification as described above. Assuming that there is a residual carrier component of the carrier wave (fc) of the multicarrier modulation wave, a description will be given of a method for removing the residual carrier component.

  In FIG. 1, an I-ch signal that is a sine component of a subcarrier signal that is logically combined in the vicinity of 0 Hz is input to input terminal 1, and a Q-ch signal that is a cos component is input to input terminal 2. Is done. The above I-ch signal and Q-ch signal are already modulated by a digital modulation method such as QPSK modulation, BPSK modulation, 16QAM modulation, 32QAM modulation, 64QAM modulation, or π / 4QPSK modulation, and are converted into multicarriers. Baseband signal.

  Here, the first multiplied signal obtained by multiplying the I-ch signal by the multiplier 5 by the signal obtained by shifting the local oscillation frequency signal of the frequency fc from the local oscillator 7 by 90 degrees by the phase shifter 8. 3 and the second multiplied signal obtained by multiplying the Q-ch signal and the local oscillation frequency signal from the local oscillator 7 by the multiplier 6 by the adder 9, FIG. A multicarrier modulation wave centered on the indicated carrier wave fc is generated. In this case, as described above, if there is an offset in the signals input to the multipliers 5 and 6, the carrier wave (fc) having the local oscillation frequency of the local oscillator 7 is leaked and output.

  Therefore, in this embodiment, in order to extract the leakage component of the carrier wave (fc), the multicarrier modulated wave output 10 output from the adder 9 and the output local oscillation frequency signal of the local oscillator 7 are supplied to the multiplier 12. The harmonics in the obtained third multiplication signal are removed by a reduction filter (LPF) 14, while the multicarrier modulated wave output 10 output from the adder 9 and the output local oscillation of the local oscillator 7 The multiplier 13 multiplies the frequency signal by 90 degrees phase-shifted by the phase shifter 11 and removes the higher harmonics in the obtained fourth multiplication signal by the reduction filter (LPF) 15. The multiplication signal from which the harmonics are removed output from the LPFs 14 and 15 is a subcarrier signal including an offset.

  The subcarrier signals output from the LPFs 14 and 15 are input to comparators 16 and 17 for comparing whether they are larger or smaller than “0”, and “1” if the inputted subcarrier signals are larger than “0”. If it is smaller, the comparators 16 and 17 operate so as to output “−1”. When this is integrated for each sampling by the integrators 18 and 19, the output of the comparator 16 is positive if the output is “1”, and negative if the output is “−1”.

  With this operation, it can be determined whether the offset exists in the positive or negative direction. The values obtained by the integrators 18 and 19 are inverted and added to the I-ch signal and Q-ch signal by the adders 3 and 4, whereby the obtained offset can be subtracted. Thus, the signal passing through the path from the multiplier 12 to the integrator 18 is added by the adder 3, and the signal passing through the path from the multiplier 13 to the integrator 19 is continuously added by the adder 4. By operating, it can be converged with a value very close to the offset component previously included in the subcarrier signal, and thereafter, it is stable and the residual carrier component included in the modulated wave output 10 is minimized.

  Next, the operation of this embodiment will be described in more detail. In FIG. 1, an I-ch signal that is a sine component (in-phase component) of a subcarrier signal logically combined in the vicinity of 0 Hz is supplied from an input terminal 1 to an adder 3, where integration is performed. It is added to the signal from the device 18. Further, the Q-ch signal which is a cos component (reverse phase component) of the subcarrier signal is supplied from the input terminal 2 to the adder 4 where it is added to the signal from the integrator 19.

  On the other hand, a local oscillation frequency signal from a local oscillator 7 that generates a local oscillation frequency signal that becomes a carrier wave fc of a multicarrier modulation wave is supplied to a multiplier 12, where a multicarrier modulation wave 10 from an adder 9 to be described later and On the other hand, the local oscillation frequency signal whose phase is shifted by 90 degrees by the phase shifter 11 is supplied to the multiplier 13 where it is multiplied by the multicarrier modulation wave 10. The third multiplication signal output from the multiplier 12 has its harmonics removed by the LPF 14, and the fourth multiplication signal output from the multiplier 13 has its harmonics removed by the LPF 15.

  The signals output from the LPFs 14 and 15 are subcarrier signals including an offset, and have a waveform as shown in FIG. 4 (A) or FIG. 6 (A). The signals output from the LPFs 14 and 15 are supplied to the comparators 16 and 17, respectively, where they are compared with the 0 level. When the signal is larger than the 0 level, "1" is obtained, and when the signal is smaller, "-1" is obtained. Output as a comparison result. Therefore, when the signal output from the LPF 14 or LPF 15 has a waveform as shown in FIG. 4A, the signal output from the comparator 16 or the comparator 17 is as shown in FIG. In the case of a signal including a positive offset component as shown in FIG. 9A, a comparison result with a long time “1” is obtained.

  Similarly, as shown in FIG. 6A, if the subcarrier signal including the offset supplied to the comparators 16 and 17 includes a negative offset component, as shown in FIG. A comparison result with a long time “−1” is obtained. The comparison results output from the comparators 16 and 17 are supplied to the integrators 18 and 19 and integrated for each sampling (addition of each sampling is repeated).

  Here, when the comparison result output from the comparators 16 and 17 is a signal longer than the time “-1” as shown in FIG. 4B, the integrator 18. , 19, the integration result obtained in FIG. 5 moves in the positive direction toward the included offset value, converges at a positive value very close to the included offset value, and then stable. To do. On the other hand, as shown in FIG. 6B, when the comparison result is a signal longer than the time “-1” compared to the time “1”, the integration results obtained by the integrators 18 and 19 are as shown in FIG. As shown in FIG. 4, the value shifts in the negative direction toward the included offset value, converges at a negative value very close to the included offset value, and then stabilizes. By the integration operation of the integrators 18 and 19, it can be determined whether the offset exists in the positive or negative direction, and the obtained integration value is inverted and supplied by the adders 3 and 4. To do.

  As a result, the I-ch signal input from the input terminal 1 is added in the adder 3 with the polarity opposite to that of the integrated signal having substantially the same level as the offset component included in the I-ch signal from the integrator 18 (that is, By subtracting, the adder 3 takes out the I-ch signal from which the offset component is substantially canceled out and supplies it to the multiplier 5. On the other hand, the Q-ch signal input from the input terminal 2 is added (that is, subtracted) in the adder 4 with an opposite polarity to the integrated signal having substantially the same level as the offset component included in the Q-ch signal from the integrator 19. ), The Q-ch signal from which the offset component is almost canceled out is extracted from the adder 4 and supplied to the multiplier 6.

  The multiplier 5 multiplies the signal obtained by shifting the local oscillation frequency signal of the frequency fc from the local oscillator 7 by 90 degrees by the phase shifter 8 and the I-ch signal from which the offset component from the adder 3 is substantially canceled out. Then, the first multiplication signal is output. On the other hand, the multiplier 6 multiplies the local oscillation frequency signal of the frequency fc from the local oscillator 7 and the Q-ch signal from which the offset component from the adder 4 is substantially canceled out, and outputs a second multiplication signal. .

  These first and second multiplication signals are added by an adder 9 to form a multicarrier modulated wave 10 centered on the carrier wave fc shown in FIG. 12 and 13 are fed back. Here, since the offset components included in the I-ch signal and the Q-ch signal, which are baseband signals, are substantially canceled out with values very close to the offset components output from the integrators 18 and 19, respectively, The residual carrier component contained in the multicarrier modulated wave 10 is minimized.

  In the present embodiment, as described above, each of the I-ch signal and the Q-ch signal is converted into a simple circuit using the comparators 16 and 17 and the integrators 18 and 19 without using a CPU or a DSP. The offset component included can be detected and subtracted from the I-ch signal and the Q-ch signal, respectively, so that the residual carrier component included in the multicarrier modulated wave 10 can be greatly reduced or eliminated. Further, by configuring each circuit of FIG. 1 with a digital circuit, it is possible to eliminate the adjustment of the circuit and to make a large-scale semiconductor integrated circuit (LSI). In that case, the reliability of the device can be improved, and the weight and size can be reduced. .

It is a circuit system diagram of one embodiment of the present invention. It is a frequency spectrum figure which shows an example of a subcarrier signal. It is a frequency spectrum figure of an example of a multicarrier modulation wave. FIG. 2 is a signal waveform diagram of an example for explaining the operation of FIG. 1. It is an output signal characteristic view of an example of the integrator in FIG. FIG. 6 is a signal waveform diagram of another example for explaining the operation of FIG. 1. It is an output signal characteristic view of the other example of the integrator in FIG.

Explanation of symbols

1 I-ch signal input terminal 2 Q-ch signal input terminal 3, 4, 9 Adder 5, 6, 12, 13 Multiplier 7 Local oscillator 8, 11 Phase shifter 10 Multicarrier modulation wave 14, 15 Low pass filter ( LPF)
16, 17 Comparator 18, 19 Integrator

Claims (6)

In a transmission apparatus that generates and transmits a modulated wave modulated by a multicarrier modulation method by orthogonally modulating a single carrier wave with a plurality of subcarrier signals,
Signal generating means for generating a first signal and a second signal having a phase difference of 90 degrees from the signal serving as the carrier;
Multiplying the modulated wave to be transmitted and the first signal to output a first multiplied signal, and multiplying the modulated wave and the second signal to output a second multiplied signal Means,
A comparison means for separately comparing the levels of the first multiplication signal and the second multiplication signal with a predetermined offset 0 level and outputting a first comparison signal and a second comparison signal;
Integrating means for integrating the first comparison signal to output a first integration signal and integrating the second comparison signal to output a second integration signal;
Subtracting means for subtracting the first integrated signal and the second integrated signal separately from the plurality of subcarrier signals, and orthogonally modulating the single carrier with the signal output from the subtracting means And generating and transmitting the modulated wave modulated by the multi-carrier modulation method. In a transmission apparatus that generates and transmits a modulated wave modulated by a multicarrier modulation method by orthogonally modulating a single carrier wave with an I-ch signal and a Q-ch signal,
Local oscillation means for outputting a local oscillation frequency signal to be the single carrier wave;
First phase shift means for converting the local oscillation frequency signal into a first signal and a second signal that are 90 degrees out of phase with each other;
First multiplication means for multiplying the first signal and the I-ch signal to generate a first multiplication signal;
Second multiplying means for multiplying the second signal and the Q-ch signal to generate a second multiplied signal;
Adding means for adding the first and second multiplication signals to generate a modulated wave modulated by the multi-carrier modulation method;
Second phase shift means for converting the local oscillation frequency signal into a third signal and a fourth signal having a phase difference of 90 degrees from each other;
Third multiplication means for multiplying the third signal and the modulated wave output from the addition means to generate a third multiplication signal;
Fourth multiplication means for generating a fourth multiplication signal by multiplying the fourth signal and the modulated wave output from the addition means;
First comparing means for generating a first comparison signal by comparing the level of the third multiplication signal with a predetermined offset 0 level;
Second comparing means for comparing the level of the fourth multiplication signal and the predetermined offset 0 level to generate a second comparison signal;
First integrating means for integrating the first comparison signal to generate a first integrated signal;
Second integrating means for integrating the second comparison signal to generate a second integrated signal;
First subtracting means for subtracting the first integrated signal from the I-ch signal supplied to the first multiplying means;
And a second subtracting means for subtracting the second integrated signal from the Q-ch signal supplied to the second multiplying means.   First filter means for removing harmonics of the third multiplication signal and supplying the first comparison means to the first comparison means; and removing harmonics of the fourth multiplication signal and supplying the second comparison means to the second comparison means The transmission apparatus according to claim 2, further comprising: a second filter unit.   The local oscillating means, the first and second phase shifting means, the first to fourth multiplying means, the adding means, the first and second comparing means, the first and second integrating means, 3. The transmission apparatus according to claim 2, wherein each of the first and second subtracting means is constituted by a digital circuit.   4. A transmission apparatus according to claim 3, wherein said first and second filter means are constituted by digital circuits. The local oscillating means, the first and second phase shifting means, the first to fourth multiplying means, the adding means, the first and second comparing means, the first and second integrating means, 4. The transmission apparatus according to claim 3, wherein the first and second subtracting means and the first and second filter means constitute a large-scale semiconductor integrated circuit.

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