JP2004040678A - Demodulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a demodulator which secures a high communication quality by realizing accurate demodulation. <P>SOLUTION: A quadrature demodulation circuit 1 demodulates a quadrature-modulated received signal into an I phase component and a Q phase component of a baseband signal, a phase error correction circuit 2 corrects an error in phase relations of the demodulated I phase component and Q phase component with respect to the relevant I phase component and the relevant Q phase component, and an amplitude error correction circuit 3 corrects an error in the amplitudes of the demodulated I phase component and Q phase component with respect to the relevant I phase component and the relevant Q phase component. In the phase error correction circuit, the phase of the Q phase component, for example, is changed by a phase change circuit, the error in the phase relations is detected by the phase error detection circuit, and the phase change is controlled by a first control coefficient application circuit. In the amplitude error correction circuit 3, the amplitude of the Q phase component, for example, is changed by an amplitude change circuit, the error in the amplitude is detected by an amplitude error detection circuit, and the amplitude change is controlled by a second control coefficient application circuit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a demodulator for demodulating a quadrature-modulated received signal into an I-phase component and a Q-phase component of a baseband signal, and more particularly, to an error in a phase relationship between an I-phase component and a Q-phase component and an error in amplitude. Related to correction technology.
[0002]
[Prior art]
For example, in a radio device using a high radio frequency for communication, a heterodyne system or a superheterodyne system using an intermediate frequency (IF) has been generally implemented. The purpose of such a method is to reduce the gain (amplifier gain) of the amplifier at the same frequency by using the intermediate frequency, or to amplify the signal at several intermediate frequencies to increase the overall gain (total gain). The purpose of this is to make the circuit easier by preventing oscillation of the amplifier.
Also, when configuring a quadrature detector (quadrature demodulator) for converting an intermediate frequency signal to a baseband signal, performing such conversion at a lower intermediate frequency can easily realize a circuit with better characteristics. We were able to.
[0003]
However, in a circuit using an intermediate frequency such as a heterodyne method, the number of components such as a filter, a mixer, and an oscillator increases, and the circuit becomes expensive.
Further, in a system that handles a wide band of radio frequencies such as a system of a software defined radio that receives signals of several types of radio frequencies, a communicable frequency band is limited to an intermediate frequency filter. For this reason, for example, if a wideband quadrature detection can be directly performed even with a signal of a high radio frequency, a great effect can be obtained.
[0004]
FIG. 4 shows an example of a conventional quadrature detection circuit.
In the quadrature detection circuit shown in the figure, an intermediate frequency (IF) signal is distributed by a distributor 41, one distributed signal is inputted to one multiplier 44, and the other distributed signal is inputted to the other multiplier 45. I do. Also, a carrier signal corresponding to, for example, the I signal is oscillated by the oscillator 42, and the 90 ° shifter 43 outputs the carrier signal to one of the multipliers 44 and shifts the phase of the carrier signal by 90 ° (degrees). The signal is output to the other multiplier 45 as a carrier signal of the Q signal. One multiplier 44 obtains an I signal by mixing (mixing) one distribution signal and a carrier signal corresponding to the I signal, and similarly, the other multiplier 45 converts the other distribution signal and the Q signal into the other distribution signal and the Q signal. A Q signal is obtained by mixing with the corresponding carrier signal.
[0005]
Here, there is a difficulty in realizing a quadrature detection circuit corresponding to a wide band frequency at a high radio frequency. Specifically, for example, it is difficult to make the phase difference between the I-phase local frequency signal and the Q-phase local frequency signal used for extracting the I-phase signal and the Q-phase signal exactly 90 degrees. Therefore, the orthogonality between the I phase and the Q phase is broken. In addition, for example, after a received signal is converted into a baseband signal, sampling is performed by an A / D (Analog to Digital) converter. The level at this time is determined by the characteristics of an amplifier provided in the baseband circuit. There is a difficulty that a level difference occurs between the I phase and the Q phase due to variations in the filter and the filter, and therefore, it is impossible to perform demodulation accurately.
[0006]
FIG. 5 shows the state of deformation of the constellation when the phase error is 10 degrees and the amplitude error is 0 dB (none) with respect to the orthogonality and the amplitude of the phases of the I phase and the Q phase. An example is shown.
FIG. 6 shows the constellation deformation when the phase error is 0 degree (none) and the amplitude error is 1 dB with respect to the orthogonality and the amplitude of the phases of the I phase and the Q phase. An example of the situation is shown.
As shown in FIG. 5 and FIG. 6, when there is the above-described phase error or amplitude error between the I phase and the Q phase, the error rate (error rate) deteriorates, and The signal cannot be accurately demodulated.
[0007]
[Problems to be solved by the invention]
As shown in the above conventional example, in the conventional quadrature detection circuit, for example, when demodulating a wideband signal at a high radio frequency, the above-described phase error and amplitude error between the I phase and the Q phase. , There is a problem that demodulation cannot be performed accurately.
[0008]
The present invention has been made to solve such a conventional problem.For example, when performing direct conversion for demodulating a high radio frequency or wideband signal directly to a baseband signal, quadrature modulation is performed. To provide a demodulation device capable of correcting an error of a phase relationship between an I-phase component and a Q-phase component and an error of an amplitude when demodulating a received signal into an I-phase component and a Q-phase component of a baseband signal. With the goal.
[0009]
In the technology described in the following document, for example, correction of a phase error and an amplitude error relating to an I-phase component and a Q-phase component is performed. By the control, it is possible to effectively correct the error of the phase relationship and the error of the amplitude between the I-phase component and the Q-phase component.
For example, in "a demodulator having an automatic quadrature control function" described in JP-A-2001-21220, it is possible to correct a quadrature error between the in-phase and quadrature components of a signal quadrature-detected by a quadrature detector. , The amplitude error of each component is corrected. In the "compensation method of receiving apparatus, receiving apparatus and transmitting / receiving apparatus" described in JP-A-8-307465, data of an error generated in the I signal and the Q signal detected by the detector is stored in a memory, During the communication, the error data is read from the memory to compensate for the error. In the "quadrature and amplitude error compensation circuit" described in Japanese Patent Application Laid-Open No. H10-56484, it is possible to compensate for quadrature errors and amplitude errors for in-phase and quadrature signals output from a quadrature quasi-synchronous detector. Done.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the demodulation device according to the present invention employs the following configuration to demodulate a quadrature-modulated received signal into an I-phase component and a Q-phase component of a baseband signal. The phase error and the amplitude error between the phase components are corrected.
That is, the quadrature demodulation circuit demodulates the quadrature-modulated reception signal into the I-phase component and the Q-phase component of the baseband signal, and the phase error correction circuit converts the demodulated I-phase component and the Q-phase component to the I-phase component and the Q-phase component. An error in the phase relationship with the Q-phase component is corrected, and an amplitude error correction circuit corrects the amplitude error between the demodulated I-phase component and the Q-phase component between the I-phase component and the Q-phase component.
[0011]
In the phase error correction circuit, the phase change circuit multiplies one of the I-phase component and the Q-phase component by the first control coefficient, and subtracts the result of the multiplication from the other component to obtain a phase error. A detection circuit multiplies the one component and the result of the subtraction by the phase change circuit to average the result of the multiplication, and a first control coefficient providing circuit converts a coefficient based on the result of the averaging by the phase error detection circuit to a phase. It is given as the first control coefficient of the changing circuit. Then, the phase error correction circuit controls the result of the averaging by the phase error detection circuit to be small, and subtracts the one component and the result of the subtraction by the phase change circuit from the I-phase component whose phase-related error has been corrected and Output as Q-phase component.
[0012]
In the amplitude error correction circuit, the amplitude change circuit multiplies one of the I-phase component and the Q-phase component by the second control coefficient, and the amplitude error detection circuit squares the result of squaring the other component and the amplitude. The result obtained by subtracting the result of squaring the result of the multiplication by the change circuit and the result of averaging is averaged, and the second control coefficient providing circuit converts the coefficient based on the result of the averaging by the amplitude error detection circuit to the second control coefficient of the amplitude change circuit. Give as. In the amplitude error correction circuit, control is performed so that the result of averaging by the amplitude error detection circuit is reduced, and the result of multiplication by the other component and the amplitude change circuit is used as the I-phase component and the Q-phase in which the amplitude error is corrected. Output as a component.
[0013]
Therefore, the phase error correction circuit can correct the demodulated I-phase component and Q-phase component so that the error in the phase relationship between the I-phase component and the Q-phase component becomes small. Can correct the demodulated I-phase component and the Q-phase component so that the amplitude error between the I-phase component and the Q-phase component becomes small, whereby the demodulated I-phase component and the Q-phase component can be corrected. And the amplitude error can be corrected.
[0014]
Here, various modulation schemes may be used as the quadrature modulation, and for example, a QPSK (Quadrature Phase Shift Keying) scheme, a QAM (Quadrature Amplitude Modulation) scheme, or the like can be used.
Various signals may be used as the reception signal.
[0015]
Further, the phase error correction circuit corrects an error from a quadrature as an error of the phase relationship between the I-phase component and the Q-phase component, that is, the phase difference between the I-phase component and the Q-phase component is 90 degrees or 90 degrees. Correct so that it is close to
Further, the amplitude error correction circuit corrects, for example, an error from the same as the amplitude error between the I-phase component and the Q-phase component, that is, the amplitude difference between the I-phase component and the Q-phase component becomes zero or close to zero. Correction as follows.
Further, the order of performing the phase error correction by the phase error correction circuit and the amplitude error correction by the amplitude error correction circuit may be arbitrary. For example, a configuration in which the amplitude error correction is performed after the phase error correction may be used. Alternatively, a configuration in which phase error correction is performed after amplitude error correction may be used.
[0016]
Further, as the one component used in the phase change circuit of the phase error correction circuit, any of the I-phase component and the Q-phase component may be used.
In addition, in the subtraction performed by the phase change circuit, for example, the result of the multiplication may be subtracted from the other component, or the other component may be subtracted from the result of the multiplication.
[0017]
In the phase error detection circuit of the phase error correction circuit, for example, the result of the multiplication is temporally averaged. The result of such averaging reflects an error in the phase relationship between the I-phase component and the Q-phase component. If control is performed such that the result of such averaging is reduced, the I- and Q-phase components are reduced. Can be reduced.
In addition, as a mode for controlling such an averaging result to be small, for example, it is preferable to control the averaging result to be 0, but other modes within a practically effective range are preferable. May be used.
[0018]
Also, as a result of the subtraction by the phase change circuit and one component output from the phase error correction circuit, for example, a configuration is used in which the one component is an I-phase component and the subtraction result is a Q-phase component. Alternatively, a configuration may be used in which one of the components is a Q-phase component and the result of the subtraction is an I-phase component.
[0019]
As the one component used in the amplitude change circuit of the amplitude error correction circuit, any of the I-phase component and the Q-phase component may be used. As the one component used in the phase change circuit of the phase error correction circuit and the one component used in the amplitude change circuit of the amplitude error correction circuit, for example, different components are used for the I-phase component and the Q-phase component. Or the same components may be used.
[0020]
In addition, in the subtraction performed by the amplitude error detection circuit of the amplitude error correction circuit, for example, the result of squaring the other component may be subtracted from the result of squaring, or the result of the multiplication may be squared. The result obtained may be subtracted from the result obtained by squaring the other component.
[0021]
In the amplitude error detection circuit of the amplitude error correction circuit, for example, the result of the subtraction is temporally averaged. The result of such averaging reflects an error in the amplitude between the I-phase component and the Q-phase component. If control is performed such that the result of such averaging becomes small, the I-phase component and the Q-phase component will be compared. The amplitude error can be reduced.
In addition, as a mode for controlling such an averaging result to be small, for example, it is preferable to control the averaging result to be 0, but other modes within a practically effective range are preferable. May be used.
[0022]
Also, as a result of the multiplication by the other component output from the amplitude error correction circuit and the amplitude changing circuit, for example, a configuration is used in which the other component is an I-phase component and the multiplication result is a Q-phase component. Alternatively, a configuration may be used in which the other component is a Q-phase component and the result of the multiplication is an I-phase component.
[0023]
Further, the radio receiver according to the present invention includes the demodulation device according to the present invention as described above, receives a signal orthogonally modulated and transmitted by radio as follows, and converts the received signal to baseband. When demodulating a signal into an I-phase component and a Q-phase component, an error in a phase relationship between the I-phase component and the Q-phase component and an error in amplitude are corrected.
That is, the receiving unit receives the radio signal, and the demodulation device demodulates the signal received by the receiving unit into the I-phase component and the Q-phase component of the baseband signal in which the phase-related error and the amplitude error are corrected. Data acquisition means acquires received data based on a result demodulated by the demodulation device.
[0024]
Therefore, for example, even in a radio receiver that performs direct conversion for demodulating a high radio frequency or wideband signal directly to a baseband signal, the quadrature-modulated reception signal is converted into the I-phase component and the Q-phase component of the baseband signal. Upon demodulation into components, errors in the phase relationship between the I-phase component and the Q-phase component and errors in the amplitude can be corrected.
[0025]
Here, various radio receivers may be used.
Further, the reception data acquisition means acquires the reception data by performing, for example, synchronization establishment processing, descrambling processing, and CRC (Cyclic Redundancy Check character) determination processing based on the result demodulated by the demodulation device. The transmitting side that wirelessly transmits the modulated signal performs scramble processing and CRC determination processing on the signal.
[0026]
The present invention may be applied to various communication systems, and is particularly suitable for application to, for example, intelligent short-range communication (DSRC: Dedicated Short Range Communication) of intelligent transport systems (ITS). Things.
Here, in the intelligent transportation system, information is transmitted and received between a person, a road and a vehicle to improve road safety and transportation efficiency, and to improve a driving environment and a walking environment. . Specifically, information is communicated between a wireless device mounted on a vehicle and a base station wireless device installed on a road or a wireless device mounted on another vehicle.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a demodulation device according to the present invention. The demodulation device of this example is provided in a wireless receiver, and demodulates a quadrature modulated signal received by the wireless receiver.
As shown in the figure, an analog quadrature demodulation circuit 1, a phase error correction circuit 2 for performing feedback control, and an amplitude error correction circuit 3 for performing feedback control are connected in series to the demodulation device of the present example. Provided.
[0028]
The analog quadrature demodulation circuit 1 receives, for example, a received signal of a wide band and a high radio frequency, and performs analog quadrature demodulation on the received signal.
The phase error correction circuit 2 receives the I-phase component and the Q-phase component of the baseband signal obtained by using the analog quadrature demodulation circuit 1, and corrects an error in the phase relationship between the I-phase component and the Q-phase component. I do.
The amplitude error correction circuit 3 receives the I-phase component and the Q-phase component output from the phase error correction circuit 2 and corrects an amplitude error between the I-phase component and the Q-phase component.
[0029]
In the demodulation device of this example, using such a configuration, for example, after demodulated baseband signals are sampled by an A / D converter (not shown), the phase relationship between the I-phase component and the Q-phase component is determined. Errors and amplitude errors are detected, and correction is performed by the amount of these errors.
Further, in this example, a synchronization establishment process, a descrambling process, and a CRC determination process are performed on the received signal based on the I-phase component and the Q-phase component output from the amplitude error correction circuit 3, whereby the received data ( Received data) and analyze it.
[0030]
Next, a configuration example of the phase error correction circuit 2 of the present example will be described.
FIG. 2 shows a configuration example of the phase error correction circuit 2 of the present example. The phase error correction circuit 2 of the present example includes a multiplier 11, an adder 12, a multiplier 13, and a low-pass filter (LPF). : Low Pass Filter) 14, an integrator 15, and a multiplier 16.
Further, the I-phase component and the Q-phase component of the demodulated baseband signal are input to the phase error correction circuit 2 of the present example, and the input I-phase component is output from the I-phase output terminal as it is. .
[0031]
The multiplier 11 multiplies the I-phase component input to the phase error correction circuit 2 by a first control coefficient α1 input from a multiplier 16, which will be described later, and outputs the result of the multiplication to the adder 12.
The adder 12 subtracts the result of the multiplication input from the multiplier 11 from the Q-phase component input to the phase error correction circuit 2 (that is, adds them in opposite phases), and multiplies the result of the subtraction by the multiplier. 13 and output from the Q-phase output terminal of the phase error correction circuit 2.
Here, the multiplier 11 and the adder 12 change (correct) the phase of the Q-phase component.
[0032]
The multiplier 13 multiplies the I-phase component input to the phase error correction circuit 2 by the result of the subtraction input from the adder 12, and outputs the result of the multiplication to the LPF 14. Here, the multiplier 13 multiplies the I phase and the Q phase.
The LPF 14 averages the result of the multiplication input from the multiplier 13 by filtering, and outputs the result of the averaging to the integrator 15.
The integrator 15 integrates the result of the averaging input from the LPF 14 and outputs the result of the integration to the multiplier 16.
[0033]
The multiplier 16 multiplies the integration result input from the integrator 15 by the loop gain coefficient Gp1, and outputs the result of the multiplication to the multiplier 11 as the first control coefficient α1. The loop gain coefficient Gp1 is supplied to the multiplier 16 under the control of, for example, a control unit (not shown).
[0034]
In the phase error correction circuit 2 of the present example, an output value obtained by averaging the result of multiplying the I-phase component by the multiplier 13 and the Q-phase component after the phase change (phase correction) by the LPF 14 is, for example, the I-phase value. When the orthogonality between the component and the Q-phase component is deviated, the value changes to either a positive (+) value or a negative (-) value instead of 0. For this reason, in this example, the error of the phase relationship between the I-phase component and the Q-phase component is corrected by controlling the feedback loop so that the output from the LPF 14 approaches 0. In this example, the multiplier 13, the LPF 14, the integrator 15, and the multiplier 16 form a feedback loop circuit.
[0035]
Next, a configuration example of the amplitude error correction circuit 3 of the present example will be described.
FIG. 3 shows a configuration of the amplitude error correction circuit 3 integrated with a quadrature demodulation unit having an analog quadrature demodulation circuit and an A / D converter in order to explain a configuration example of the amplitude error correction circuit 3 of the present example. An example is shown.
Here, the local signal oscillator 21, the phase shifter 22, the multiplier 23, the multiplier 24, the multiplier 25, the LPF 26 and the LPF 27 shown in FIG. The D converter 28 and the A / D converter 29 are parts for converting the I component and the Q component of the baseband signal demodulated by the analog quadrature demodulation circuit from an analog signal to a digital signal.
[0036]
In the present example, the quadrature demodulation unit composed of the analog quadrature demodulation circuits 21 to 27 and the A / D converters 28 and 29 is provided before the phase error correction circuit 2. Although the configuration is not directly connected, a configuration example of the quadrature demodulation unit will be described here.
[0037]
That is, the local signal oscillator 21 oscillates, for example, a carrier signal corresponding to the I phase and outputs the carrier signal to the phase shifter 22 and the multiplier 23.
The phase shifter 22 shifts the phase of the carrier signal input from the local signal oscillator 21 by (90 + Δθ) degrees, and outputs the signal after the phase shift to the multiplier 24 as a carrier signal corresponding to the Q phase. Here, Δθ causes an error in the phase relationship between the I-phase component and the Q-phase component.
[0038]
The multiplier 23 multiplies (mixes) the signal (input band signal S) input as a demodulation target and the I-phase carrier signal input from the local signal oscillator 21, and outputs the result of the multiplication to the LPF 26.
The multiplier 24 multiplies (mixes) the signal (input band signal S) input as a demodulation target and the Q-phase carrier signal input from the phase shifter 22, and outputs the result of the multiplication to the LPF 27.
[0039]
Here, the multiplier 25 shown between the multiplier 24 and the LPF 27 generates an error in the amplitude of the I-phase component and the Q-phase component due to a factor ΔG caused by, for example, the characteristics of the amplifier and the dispersion of the filter. This is a conceptual representation of the situation.
[0040]
The LPF 26 filters the result of the multiplication input from the multiplier 23 to extract an I-phase component, and outputs the I-phase component to the A / D converter 28.
The LPF 27 filters the result of the multiplication input from the multiplier 24 to extract a Q-phase component, and outputs the Q-phase component to the A / D converter 29.
The A / D converter 28 converts the I-phase component input from the LPF 26 from an analog signal to a digital signal.
The A / D converter 29 converts the Q-phase component input from the LPF 27 from an analog signal to a digital signal.
[0041]
Next, a configuration example of the amplitude error correction circuit 3 of the present example will be described.
As shown in FIG. 3, the amplitude error correction circuit 3 of the present example includes a multiplier 30, a squarer 31, a squarer 32, an adder 33, an LPF 34, an integrator 35, And an adder 37.
In the amplitude error correction circuit 3 of this example, the I-phase component and the Q-phase component output from the phase error correction circuit 2 are input, and the input I-phase component is output from the I-phase output terminal as it is. Is done.
[0042]
The multiplier 30 multiplies a Q-phase component input to the amplitude error correction circuit 3 by a second control coefficient α2 input from an adder 37 described later, and outputs a result of the multiplication to the squarer 32. At the same time, the signal is output from the Q-phase output terminal of the amplitude error correction circuit 3. Here, the multiplier 30 changes (corrects) the amplitude of the Q-phase component.
[0043]
The squarer 31 obtains energy (power) by squaring the I-phase component input to the amplitude error correction circuit 3, and outputs the squared result to the adder 33.
The squarer 32 obtains energy (power) by squaring the result of the multiplication input from the multiplier 30, and outputs the squared result to the adder 33.
The adder 33 subtracts the result of the square input from the squarer 31 from the result of the square input from the squarer 32 (that is, adds them in opposite phases), and calculates the result of the subtraction. Output to LPF34.
[0044]
The LPF 34 averages the result of the subtraction input from the adder 33 by filtering, and outputs the result of the averaging to the integrator 35.
The integrator 35 integrates the result of the averaging input from the LPF 34 and outputs the result of the integration to the multiplier 36.
[0045]
The multiplier 36 multiplies the integration result input from the integrator 35 by the loop gain coefficient Gp2, and outputs the result of the multiplication to the adder 37. The loop gain coefficient Gp2 is supplied to the multiplier 36 under the control of, for example, a control unit (not shown).
The adder 37 subtracts, for example, the result of the multiplication input from the multiplier 36 from the value of “1” (that is, adds them in opposite phases), and uses the result of the subtraction as the second control coefficient α2. The result is output to the multiplier 30.
[0046]
In the amplitude error correction circuit 3 of the present example, the difference between the square result of the I-phase component and the square result of the Q-phase component after the amplitude change (amplitude correction) is obtained by the two multipliers 31 and 32 and the adder 33. If the output value obtained by averaging the results obtained by the LPF 34 has, for example, a difference in amplitude between the I-phase component and the Q-phase component, the value is not 0 but a positive (+) value or a negative value. (-). Therefore, in this example, the error of the amplitude between the I-phase component and the Q-phase component is corrected by controlling the feedback loop so that the output from the LPF 34 approaches 0. In this example, a feedback loop circuit is configured by the squarer 31, the squarer 32, the adder 33, the LPF 34, the integrator 35, the multiplier 36, and the adder 37.
[0047]
As described above, the demodulation device provided in the wireless receiver of the present embodiment is applied to a quadrature detector (quadrature demodulator) used for demodulating a signal modulated by, for example, a QPSK method or a QAM method. The distortion of the received signal is reduced by automatically correcting the phase and amplitude of the I-phase component and the Q-phase component obtained by demodulating the received signal using the phase error correction circuit 2 and the amplitude error correction circuit 3. be able to. In the present embodiment, as a preferable mode, the phase error correction circuit 2 and the amplitude error correction circuit 3 are disposed immediately after the analog quadrature demodulation circuit 1. The configuration is such that signal errors are automatically corrected.
[0048]
More specifically, the demodulation device provided in the wireless receiver of the present embodiment includes a quadrature demodulation circuit 1 that demodulates a received QPSK signal, a QAM signal, and the like to obtain I-phase and Q-phase baseband signals, A phase error correction circuit 2 for correcting an error in the mutual phase relationship between the I-phase and the Q-phase of the I-phase and Q-phase baseband signals, and an I-phase and a Q-phase baseband signal in which the error in the phase relationship is corrected And an amplitude error correction circuit 3 for correcting the mutual amplitude error of the I-phase and the Q-phase.
[0049]
In the phase error correction circuit 2, a loop state is formed as shown in FIG. 2, and the output from the LPF 14 becomes 0 or almost 0 (that is, the I phase and the Q phase are orthogonal or almost orthogonal). Control).
In the amplitude error correction circuit 3, a loop state is formed as shown in FIG. 3, and the output from the LPF 34 becomes 0 or almost 0 (that is, the amplitudes of the I phase and the Q phase match or Control).
[0050]
Further, the wireless receiver of the present example includes a receiving unit that receives a QPSK signal, a QAM signal, or both of these signals, and the above-described baseband signal demodulation circuit that demodulates the received signal. Synchronization is established with respect to the obtained signal, descrambling is performed, CRC is determined, and after performing S / P (Serial to Parallel) conversion, a control signal or the like as a received signal is extracted.
[0051]
As described above, in the demodulator provided in the wireless receiver of the present embodiment, for example, when performing direct conversion over a high radio frequency or a wide band, the quadrature detector detects the phase error and the amplitude error with respect to the I-phase component and the Q-phase component. In such a case, these errors can be corrected, so that accurate demodulation can be performed, and the error rate of the received signal can be improved.
[0052]
As a specific example, in the case of receiving a plurality of desired signal waves, using a conventional heterodyne method in which a received wave is once converted into an intermediate frequency signal (IF) using a local frequency, the bandwidth of an IF filter is increased. The characteristics limit the number of desired received signals over a wide band, increase the size of the hardware, and, for example, to reduce the complexity of the system in a software defined radio. It is more advantageous to demodulate the quadrature signal without dropping the signal into the IF band. On the other hand, since accurate separation (demodulation) of orthogonal I-phase and Q-phase signals in a high frequency band is required, a phase difference of exactly π / 2 (= 90 degrees) is synchronized with the high frequency band frequency. A disadvantage arises in that it is necessary to prepare a demodulation orthogonal local frequency signal that maintains the following. Further, there is a problem that an error occurs in the amplitude of each phase (I phase and Q phase) after separation. Here, with respect to such a phase error and an amplitude error, examples of distortion of the signal point arrangement of the I-phase and Q-phase signals subjected to the quadrature detection are as shown in FIGS. 5 and 6 described above. Such a phase error and an amplitude error cause an error rate of a communication line to deteriorate.
[0053]
On the other hand, such a problem can be solved by using the demodulation device of the present embodiment.
That is, in the demodulation device of the present example, for example, separation and demodulation of I-phase and Q-phase signals by a normal analog method using a local frequency signal wave including a certain error in a phase difference of π / 2 in a high frequency band, for example. In such a case, the output of the demodulation result is sampled and digitized, and then the correction of the phase-related error and the correction of the amplitude error are executed by digital processing, thereby providing a communication line. Can be improved.
[0054]
In the phase error correction circuit 2 of the present embodiment, the I-phase component is used as one component, the Q-phase component is used as the other component, and the one component is multiplied by the first control coefficient α1 by the multiplier 11. A circuit for subtracting the result of the multiplication and the other component by the adder 12 constitutes a phase change circuit, and the one component and the result of the subtraction by the phase change circuit are multiplied by the multiplier 13. A phase error detection circuit is composed of a circuit for averaging the result of the multiplication by the LPF 14, and a coefficient based on the result of the averaging by the phase error detection circuit is integrated by the integrator 15 and the multiplier 16 into the first phase change circuit. A first control coefficient assigning circuit is constituted by a circuit assigned as the control coefficient α1.
[0055]
Further, in the amplitude error correction circuit 3 of the present example, a circuit in which the Q-phase component is one component, the I-phase component is the other component, and the one component is multiplied by the second control coefficient α2 by the multiplier 30. And a result obtained by adding the result of squaring the other component by the squarer 31 and the result of squaring the result of multiplication by the amplitude change circuit by the squarer 32 and subtracting the result by the adder 33. An amplitude error detection circuit is constituted by a circuit for averaging by the LPF 34, and a coefficient based on the result of averaging by the amplitude error detection circuit is integrated by the integrator 35, the multiplier 36, and the adder 37 into the second of the amplitude change circuit. A second control coefficient assigning circuit is constituted by a circuit assigned as the control coefficient α2.
[0056]
Further, in the wireless receiver of the present example, a receiving unit is configured by a function of receiving a quadrature modulated signal transmitted wirelessly from the transmitting side, and communication data received based on a result demodulated by the demodulation device and the like. A function of acquiring control data or the like as received data constitutes a received data acquisition unit.
[0057]
Here, the configurations of the demodulation device and the wireless receiver according to the present invention are not necessarily limited to those described above, and various configurations may be used. Note that the present invention can be provided, for example, as a method for executing the processing according to the present invention, a program for realizing such a method, or the like.
Further, the application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
[0058]
Further, as various processes performed in the demodulation device and the wireless receiver according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A configuration controlled by performing the above-described processing may be used. For example, each functional unit for executing the processing may be configured as an independent hardware circuit.
Further, the present invention can be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the above-mentioned control program or the program (the program itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.
[0059]
【The invention's effect】
As described above, according to the demodulation device according to the present invention, when the received signal orthogonally modulated by the orthogonal demodulation circuit is demodulated into the I-phase component and the Q-phase component of the baseband signal, the demodulated signal is demodulated by the phase error correction circuit. The phase error between the I-phase component and the Q-phase component is corrected for the I-phase component and the Q-phase component, and the I-phase component and the Q-phase component are demodulated by the amplitude error correction circuit. As a configuration for correcting an amplitude error with a phase component, in a phase error correction circuit, a phase change circuit changes, for example, the phase of a Q-phase component, and a phase error detection circuit detects a phase-related error and a first control coefficient. The giving circuit controls the phase change. In the amplitude error correcting circuit, the amplitude changing circuit changes the amplitude of, for example, the Q-phase component, and the amplitude error detecting circuit detects the amplitude error. Because you to control the amplitude change, it is possible to effectively correct errors and errors in the amplitude of the phase relationship between the demodulated I-phase component and the Q-phase component.
[0060]
Further, according to the radio receiver according to the present invention, a demodulation device as described above is provided, a radio signal is received, and a signal received by the demodulation device is converted into a baseband signal in which a phase-related error and an amplitude error are corrected. Demodulated into the I-phase component and the Q-phase component, and the received data is obtained based on the result demodulated by the demodulation device. For example, a high-frequency or wideband signal is directly demodulated into a baseband signal. Even when performing direct conversion, when demodulating a quadrature-modulated received signal into an I-phase component and a Q-phase component of a baseband signal, an error in the phase relationship between the I-phase component and the Q-phase component and an error in the amplitude. Can be corrected, whereby accurate demodulation can be realized and high communication quality can be ensured.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a demodulation device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration example of a phase error correction circuit.
FIG. 3 is a diagram illustrating a configuration example of an amplitude error correction circuit.
FIG. 4 is a diagram illustrating an example of a quadrature detection circuit.
FIG. 5 is a diagram showing an example of a state of deformation of a constellation when there is a phase error.
FIG. 6 is a diagram illustrating an example of a state of deformation of a constellation when there is an amplitude error.
[Explanation of symbols]
1. Analog quadrature demodulation circuit 2. Phase error correction circuit
3. Amplitude error correction circuit,
11, 13, 16, 23 to 25, 30, 36,...
12, 33, 37 ... Adder, 14, 26, 27, 34 ... LPF,
15, 35 integrator, 21 local signal oscillator,
22 ··· Phase shifter, 28, 29 ·· A / D converter,
31, 32 ... squarer,

Claims (2)

In a demodulation device that demodulates a quadrature-modulated received signal into an I-phase component and a Q-phase component of a baseband signal,
A quadrature demodulation circuit for demodulating a quadrature-modulated received signal into an I-phase component and a Q-phase component of a baseband signal;
A phase error correction circuit that corrects an error in a phase relationship between the I-phase component and the Q-phase component with respect to the demodulated I-phase component and the Q-phase component;
An amplitude error correction circuit that corrects an amplitude error between the demodulated I-phase component and the Q-phase component between the I-phase component and the Q-phase component;
A phase error correction circuit configured to multiply one of the I-phase component and the Q-phase component by a first control coefficient and to subtract a result of the multiplication from the other component; A phase error detection circuit that averages the result of the multiplication by multiplying the result of the subtraction by the phase change circuit, and a coefficient based on the result of the averaging by the phase error detection circuit as a first control coefficient of the phase change circuit. And a first control coefficient providing circuit for controlling the phase error detection circuit so that the result of averaging by the phase error detection circuit is reduced. Output as corrected I-phase component and Q-phase component,
The amplitude error correction circuit includes an amplitude change circuit that multiplies one of the I-phase component and the Q-phase component by the second control coefficient, and a result of squaring the other component and a result of the multiplication by the amplitude change circuit. An amplitude error detection circuit for averaging the result obtained by subtracting the squared result, and a second control coefficient providing circuit for providing a coefficient based on the result of averaging by the amplitude error detection circuit as a second control coefficient of the amplitude change circuit And the control is performed so that the result of the averaging by the amplitude error detection circuit is reduced, and the result of the multiplication by the other component and the amplitude change circuit is used as the I-phase component and the Q-phase component in which the amplitude error is corrected. Output as
A demodulator characterized by the above-mentioned. In a radio receiver that receives a signal that is orthogonally modulated and transmitted by radio, and demodulates the received signal into an I-phase component and a Q-phase component of a baseband signal,
Receiving means for receiving a radio signal;
2. The demodulator according to claim 1, wherein the demodulation device demodulates the signal received by the receiving unit into an I-phase component and a Q-phase component of the baseband signal in which a phase-related error and an amplitude error are corrected.
Reception data acquisition means for acquiring reception data based on a result demodulated by the demodulation device,
A wireless receiver comprising:

Images