JP2005286928A - Receiving device and receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a positioning error due to a signal processing delay time difference in respective receivers 100 when a plurality of receivers 100 receive a radio wave from an unknown station 102 and the unknown station 102 is positioned from a difference of reception time. <P>SOLUTION: A calibration function is given inside the receiver 100. The function changes over output of an antenna and a calibration signal by a switch and makes the calibration signal pass through a frequency conversion circuit. The calibration signal made into a base band is Fourier-transformed and a distortion of a phase at every frequency is acquired. A phase characteristic by a frequency converter is specified at every frequency. A correction coefficient for negating the specified phase characteristic is obtained and it is multiplied by output obtained by Fourier-transforming a base band signal of the radio wave which is actually received. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a receiving technique, and more particularly to a receiving apparatus that receives a radio wave emitted from a radio wave source to generate a baseband signal and a receiving method for obtaining a frequency component of the baseband signal. The present invention also relates to a calibration technique used in such a reception technique.

A technique for identifying the position of a mobile object or other unknown radio wave source (hereinafter referred to as an “unknown station”) may be necessary for security or crime prevention purposes. Patent Document 1 proposes a technique in which a plurality of receiving devices are arranged at intervals and a position of an unknown station is estimated based on a time difference between radio waves reaching each receiving device. In this technique, when each receiving apparatus receives a radio wave, the frequency component data of the modulated wave is notified to the positioning center, and the positioning center compares the reception times to identify the position where the unknown station may exist.
Japanese Patent Laid-Open No. 2002-40120

  Generally, in the receiving apparatus, the delay time of the reception processing system varies due to individual differences in the characteristics of elements having a group delay such as an internal filter. This variation affects the output signal of the receiving apparatus and deteriorates the accuracy of estimating the position of the unknown station. In order to estimate the position of an unknown station with high accuracy, it is necessary to accurately detect a slight difference in arrival time of the same radio wave in a plurality of receivers, so the delay time of the reception processing system must be kept as small as possible. I must.

  The present invention was born from recognition of such problems, and an object thereof is to provide a reception technique and a calibration technique that reduce a delay time difference of the reception processing system. Another object of the present invention is to realize such a technique with a relatively small circuit scale.

  The receiving device of the present invention receives a radio wave emitted from a radio wave source, performs frequency conversion, outputs a baseband signal, a Fourier transform unit that develops the baseband signal into frequency components, and a frequency conversion Calibration means for canceling phase characteristics inherent in the output of the Fourier transform means based on the correction amount obtained by passing the calibration signal through the means.

  The “frequency converting means” may have various forms such as a combination of a receiving unit that drops radio frequency radio waves to an intermediate frequency and a frequency converting unit that drops a signal of the intermediate frequency to a baseband signal.

  The “phase characteristic” is a characteristic generated in the reception processing system, particularly the frequency conversion means, and is generated by, for example, the group delay characteristic of the filter. The phase characteristic is a state of phase distortion or rotation with respect to frequency, and is a characteristic unique to the receiving apparatus. According to the present invention, since the correction amount for canceling the phase characteristic is obtained by passing the calibration signal in advance, it is possible to suppress delay time variations inherent in the receiving apparatus. This is because the delay time for each frequency depends on the phase characteristics.

  Another aspect of the present invention is also a receiver, a selection unit that selects one of a reception signal of a radio wave emitted from a radio wave source and a calibration signal, frequency conversion is performed on the output of the selection unit, and an in-phase component and a quadrature component A frequency converting means for outputting the separated baseband signal, a Fourier transform means for applying a Fourier transform to the in-phase component and the quadrature component, and developing them into a set of complex frequency components, and a phase characteristic inherent in the output of the Fourier transform means Correction amount calculating means for calculating and holding a correction amount for canceling the correction, and calibration means for causing the calculated and held correction amount to act on the output of the Fourier transform means. The correction amount calculating means calculates and holds the correction amount when the selection means selects the calibration signal, and the calibration means Fourier transforms the correction amount when the selection means selects the radio wave reception signal. It acts on the output of the means. Even in this aspect, it is possible to suppress variations in delay time of the receiving apparatus.

  These receiving devices further include means for generating the calibration signal by applying a rectangular modulation wave to a predetermined carrier signal. In this case, since the fundamental wave and harmonics of the modulated wave component have the same phase, if the harmonics cover the frequency band of the assumed radio wave, calibration is performed using the phase of each harmonic as the reference phase. Calibration using signals becomes possible.

  Another aspect of the present invention relates to a receiving method. This method includes a step of calculating a correction amount for canceling the phase characteristic based on the phase characteristic obtained by passing the calibration signal through the reception processing system, and receiving the radio wave emitted by the radio wave source. The baseband signal is converted into a baseband signal, the baseband signal obtained by the conversion is expanded into frequency components, and the correction amount is applied to the expanded frequency components.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to align internal delay times unique to a receiving apparatus.

Outline of Embodiment The point to be understood as the premise of the following explanation is that “a frequency-dependent delay characteristic (hereinafter simply“ delay characteristic ”) is a frequency-dependent phase characteristic (hereinafter simply“ phase characteristic ”). It is the fact that it is differentiated with respect to. Therefore, the delay characteristic can be obtained if the phase characteristic is obtained. In the following description, the delay characteristic may be obtained directly or the phase characteristic may be obtained unless otherwise required.

  The receiving apparatus according to the embodiment receives a radio wave emitted from an unknown station, measures a frequency component of the modulated wave, and notifies the positioning center. The positioning center receives notification of the frequency component of the modulated wave of the received signal from a plurality of receiving devices, and specifies the position of the unknown station based on the time difference detected from the difference in the phase characteristics. At that time, it is only necessary to pay attention to one of the frequencies included in the radio wave. Therefore, in principle, the position can be specified regardless of the modulation method used by the unknown station.

  The radio wave received by each receiver is first dropped to an intermediate frequency and then dropped to a baseband signal. At this time, the in-phase component and the quadrature component are generated separately. The in-phase component and the quadrature component are expanded into a set of frequency components by fast Fourier transform (hereinafter simply referred to as FFT). The positioning center pays attention to the frequency components from any two receiving apparatuses, and calculates the arrival time difference between the two receiving apparatuses for a specific frequency based on the “arrival time difference calculation principle” described later.

  However, the delay time of a series of reception processing systems that receive radio waves and drop them into intermediate-frequency signals and further baseband signals has frequency-dependent variations due to the group delay characteristics of the filter. Has delay characteristics. As a result, an error that is different for each receiving device is mixed in the frequency component of the modulated wave of the received signal measured in each receiving device, and an error is naturally also mixed in the arrival time difference obtained by the positioning center.

  In order to solve this problem, the receiving apparatus according to the present embodiment has a calibration function. This function obtains the delay characteristic inside the reception processing system using the calibration signal, and then determines the correction amount so that the delay characteristic becomes constant regardless of the frequency. The correction amount is a numerical value obtained by multiplying the in-phase component and the quadrature component of the frequency component (complex number) of the modulated wave of the received signal output by the receiving apparatus, and has an in-phase component and a quadrature component for each frequency. Since this correction amount uses a calibration signal generated inside the receiving apparatus, it is possible to cancel the delay characteristic that is purely caused by the internal characteristics of the receiving apparatus. As a result, the frequency component that the radio wave has and its arrival time can be accurately determined, and the position of the unknown station can be accurately identified by the positioning center.

  In addition to the variation in delay characteristics of the receiving apparatus, the radio wave has phase characteristics due to multipath or the like during propagation. Since this phase characteristic also becomes a position specifying error, it is considered that the influence of the phase characteristic on the radio frequency signal is eliminated in the above-described “Principle of arrival time difference calculation”.

  The calibration function needs to work correctly within the frequency band (hereinafter referred to as “target band”) of radio waves that are assumed to be received by the receiving apparatus. For this reason, in this embodiment, a calibration signal is generated by applying a rectangular modulation wave to a predetermined carrier signal. This calibration signal includes a harmonic of a rectangular wave, and covers the target band with a fundamental frequency wave and a harmonic. Conversely, the frequency of the carrier signal and the rectangular modulation wave is determined so as to satisfy such a requirement. However, since harmonics appear only discretely, the entire target band cannot be covered with the calibration signal as it is. Therefore, in the present embodiment, when the delay characteristic inside the receiving apparatus is obtained, the frequency of the calibration signal is interpolated, and the delay characteristic is obtained even for a frequency that does not exist.

Principle of calculating arrival time difference Since the receiving device functions as a sensor for detecting radio waves, it may be hereinafter referred to as a “sensor station”. At each sensor station, frequency conversion to a complex baseband using in-phase and quadrature components (hereinafter also referred to as I / Q components) is performed, and a signal obtained by fast Fourier transform according to a reference time by GPS (Global Positioning System) Then, it is transmitted to the positioning center by wired or wireless line. The positioning center calculates the complex conjugate product after compensating for the frequency offset of each received signal, and detects the radio wave arrival time difference between the sensor stations from the amount of phase rotation of the conjugate product in the frequency axis direction.

未知局から発射された信号は、センサ局１では、雑音を無視すると式２の信号として受信される。

Let fc be the carrier frequency of a radio wave emitted from an unknown station. The frequency component of the frequency fc + fk in the transmission signal is expressed by Equation 1.

A signal emitted from an unknown station is received at the sensor station 1 as a signal of Equation 2 when noise is ignored.

Here, the subscript “1” is the number of the sensor station, and τ ₁ is the propagation delay time from the unknown unknown station to the sensor station 1. The received signal is divided into I / Q components at each sensor station and frequency-converted into a complex baseband signal. In the sensor station 1, the signal of the baseband frequency fk is shown in Equation 3.

センサ局２についても同様に、ベースバンド周波数ｆｋの信号をフーリエ変換して式５を得る。

Here, the phase of the radio frequency signal is ψ ₁ = 2πfc (t−τ ₁ ). Equation 4 is Fourier transformed to obtain Equation 4.

Similarly, for the sensor station 2, the signal of the baseband frequency fk is Fourier transformed to obtain Equation 5.

式６と同様、ベースバンド周波数ｆｋのフーリエ変換出力について、式７のセンサ局間の共役積を得る。

式６、７から式８の共役積を求めることにより無線周波数信号の位相Ψを除去する。

電波到達時間差ｄ_１２＝τ_２−τ_１は、式８の偏角を２π（ｆ_ｋ’−ｆ_ｋ）で除すことにより得られる。

Next, the phase Ψ of the radio frequency signal is removed without detecting the received signal. The conjugate product of Equations 4 and 5 is shown in Equation 6.

Similar to Equation 6, the conjugate product between the sensor stations of Equation 7 is obtained for the Fourier transform output of the baseband frequency fk.

The phase Ψ of the radio frequency signal is removed by obtaining the conjugate product of Expressions 6 and 7 to Expression 8.

The radio wave arrival time difference d ₁₂ = τ ₂ −τ ₁ is obtained by dividing the declination of Equation 8 by 2π (f _{k ′} −f _k ).

  According to the above principle, time difference detection can be performed without depending on the radio frequency phase difference between the sensor stations, and the application range of the transmission frequency and radio wave format of the unknown station is not limited.

Embodiment FIG. 1 shows an overall configuration of a positioning system 200 according to an embodiment. The positioning system 200 includes a plurality of receiving devices 100 that are sensor stations and a positioning center 104, and the receiving devices 100 are connected to the positioning center 104 by wired or wireless lines, respectively. Each receiving device 100 receives radio waves from the unknown station 102, converts them into baseband signals, performs FFT, and notifies the positioning center 104 of the data obtained as a result. The positioning center 104 identifies a position where the unknown station 102 can exist based on the notified data and the “principle of arrival time difference calculation”. In principle, if the notification from three or more receiving apparatuses 100 is obtained, the positioning center 104 can uniquely identify the position of the unknown station 102.

  FIG. 2 shows an internal configuration of one receiving apparatus 100. The antenna 10 receives radio waves from the unknown station 102. The received radio wave is input to one end of the switch 12. A calibration signal CA is input to the other end of the switch 12. The switch 12 performs a selection operation according to a selection signal SW from the digital signal processing circuit 18.

  The radio frequency signal RF selected by the switch 12 is input to the frequency converter 14. The frequency converter 14 down-converts this signal into a signal IF having an intermediate frequency and outputs it to the A / D converter 16. The A / D converter 16 undersamples this signal at a sampling frequency fs lower than the Nyquist frequency of the carrier frequency fc, and converts it into a digital signal. The converted signal is input to the digital signal processing circuit 18. The signal input to the digital signal processing circuit 18 is subjected to FFT in the digital signal processing circuit 18 to output a digital signal Dout (hereinafter also referred to as “final signal Dout”). The final signal Dout is a signal to be sent to the positioning center 104, and the transmission is performed by a communication unit (not shown). The digital signal processing circuit 18 controls the switch 12 in accordance with a calibration period or another normal period (hereinafter simply referred to as “normal period”).

  The calibration signal generator 20 receives a predetermined carrier signal fc having a frequency fc, converts it into a signal in the above-described target band, and generates a calibration signal CA.

  In the above configuration, both the frequency converter 14 and the quadrature detector (described later) in the digital signal processing circuit 18 have a function of converting the frequency, and therefore one or a combination thereof is grasped as a “frequency converting means”. be able to.

  FIG. 3 shows the internal configuration of the digital signal processing circuit 18. The digital signal processing circuit 18 calculates the correction amount for canceling the phase characteristic from the output of the fast Fourier transformer 42 in the calibration period, and the fast Fourier transformer 42 that performs FFT on the output thereof. An amount calculation unit 44, a memory 46 that records the calculated correction amount, and a calibration unit 48 that reads the correction amount from the memory 46 during a normal period and multiplies the output of the fast Fourier transformer 42 by the multiplier 50. . The correction amount calculation unit 44 generates a selection signal SW. At this time, the selection signal SW is designed to select the calibration signal CA in the switch 12 during the calibration period and to select the radio wave received from the antenna 10 during the normal period. The signals after the Fast Fourier Transformer 42 are also complex numbers having a real part and an imaginary part, but are shown by a single signal line for the sake of convenience.

  The quadrature detector 30 converts the output of the A / D converter 16 into a baseband and an I / Q component. The quadrature detector 30 inputs a sampling frequency fs and an output thereof is π / 2. It has a phase shifter 34 that delays only by. The output of the NCO 32 is multiplied by the output of the A / D converter 16 by the multiplier 36, and the output of the phase shifter 34 is multiplied by the A / D converter 16 by another multiplier 38, and the output of each multiplier is in-phase component. I and quadrature component Q are obtained. The I / Q component is input to a CIC (Cascaded Integrator-Comb) / FIR 40. The CIC filter at the front stage of the CIC / FIR filter 40 is a low-pass filter that drops the data rate of the baseband-converted I / Q component, and the post-stage FIR filter extracts only the band necessary for baseband conversion.

  The I / Q component that has been subjected to the necessary band processing (hereinafter also referred to as “I / Q component before FFT”) is input to the fast Fourier transformer 42. From the I / Q components before the FFT, phase characteristic data X (hereinafter also simply referred to as “phase characteristic data X”) for each frequency component is obtained in the fast Fourier transformer 42. Based on the phase characteristic data X input during the calibration period, the correction amount calculation unit 44 obtains a correction amount that makes the phase characteristic zero by a method described later, and records this in the memory 46.

  4A to 4C are examples of the internal configuration of the calibration signal generator 20. The calibration signal generator 20 is a logic circuit or an analog circuit that obtains a calibration signal CA by applying a rectangular modulation wave MCLK having a modulation wave fundamental frequency of fm to the carrier signal fc, as shown in FIG. Then, the attenuator 60 is used. The attenuator 60 ASK modulates the carrier signal fc with the rectangular modulation wave MCLK. In FIG. 4B, an AND gate 62 is used. The AND gate 62 takes the logical product of the carrier signal fc and the rectangular modulation wave MCLK. As a result, ASK modulation is performed. In FIG. 4C, an XOR (exclusive or) 64 is used. The XOR gate 64 takes an exclusive OR of the carrier signal fc and the rectangular modulation wave MCLK. As a result, PSK modulation is performed. In either case, the configuration is very simple, and it is advantageous in terms of both cost and mounting area when it is incorporated into the apparatus.

  5A shows an example of a frequency spectrum that appears as a result of ASK modulation by the calibration signal generator 20 of FIG. 4A or FIG. 4B, and FIG. 5B shows the calibration signal of FIG. 4C. Examples of frequency spectra that appear as a result of PSK modulation by the generator 20 are shown. In any case, it has a frequency component in which the modulated wave fundamental frequency fm and its harmonics are distributed around the frequency fc of the carrier signal. The correction amount calculation unit 44 obtains a correction amount that cancels the phase characteristic of each frequency component of the calibration signal CA, and calculates the phase characteristic in the target band caused by the reception processing system, particularly the group delay characteristic of the frequency converter 14. Eliminate.

  FIG. 6 schematically shows the phase characteristic data X input to the correction amount calculation unit 44. Here, the phase θ is rotated according to the frequency in the target band. In the figure, n is the order of FFT. FIG. 7 schematically shows the correction amount obtained by the correction amount calculation unit 44, here the phase characteristic data XY after the correction coefficient Y is applied. As shown in the figure, by applying the correction coefficient Y, the amount of phase rotation is all zero within the target band. Since the delay characteristic is obtained by differentiating the phase characteristic with respect to the frequency, if the phase characteristic is zero, the delay characteristic is also zero, and variations in delay time among the receiving apparatuses 100 can be eliminated. As a result, the positioning accuracy of the unknown station 102 can be increased.

また、位相と振幅によりX(n)を表すと以下の関係がある。

Derivation of the correction coefficient Y by the correction amount calculation unit 44 is performed according to the following procedure. Since the output of the fast Fourier transformer 42 is complex data, when each complex data is represented by X (n) = a (n) + jb (n), the phase θ (n) and the amplitude A (n at each n ) Is obtained by the following equation.

Further, when X (n) is expressed by the phase and the amplitude, there is the following relationship.

Y(n)=c(n)+jd(n)とおくと

Considering the phase correction coefficient Y (n) for correcting the phase θ (n) to zero (A (n) + j0) without changing the amplitude A (n) of this complex data X (n), X ( n) From Y (n) = A (n)

Y (n) = c (n) + jd (n)

となり、受信電波に対する周波数領域複素データX_RF(n)の位相θ_RF (n)からキャリブレーション信号入力のXc(n)の位相θc(n)を差し引いた位相を持つ周波数領域複素データとなる。 The frequency domain complex data acquired in the calibration period is Xc (n) (phase θc (n), amplitude Ac (n)), and its correction coefficient is Yc (n). The result of multiplying the frequency domain complex data X _RF (n) (phase θ _RF (n), amplitude A _RF (n)) for any received radio wave acquired in the normal period by the correction coefficient Yc (n) is

Thus, the frequency domain complex data having a phase obtained by subtracting the phase θc (n) of Xc (n) of the calibration signal input from the phase θ _RF (n) of the frequency domain complex data X _RF (n) for the received radio wave.

よって以下の式となる。

Here, both the phase θ _RF (n) and the phase θc (n) include the influence of the inherent phase characteristic mainly by the analog circuit that passes through before being input to the reception processing system, particularly the A / D converter 16. This is the phase φ _RCV (n), and the phase components in terms of the input end of the reception processing system excluding this from the phase θ _RF (n) and phase θc (n) are φ _RF (n) and φc (n), respectively. If

Therefore, the following formula is obtained.

となり、位相補正された周波数領域複素データX_RF (n)Yc(n)からは受信処理系の固有位相特性φ_RCV(n)が消える。 From this equation, Equation 10 becomes

Thus, the intrinsic phase characteristic φ _RCV (n) of the reception processing system disappears from the phase-corrected frequency domain complex data X _RF (n) Yc (n).

φ _RF (n) and φ _C (n) include the carrier phase of each input signal. If the above-mentioned `` Principle of arrival time difference calculation '' is used, the difference in carrier phase between receivers is the time difference. It can be ignored for detection. From the above, the correction amount calculation unit 44 obtains the correction coefficient Yc (n) in advance using the calibration signal CA, and the calibration unit 48 uses this to calculate X _RF (n ) Multiplied by Yc (n), correct positioning is realized by eliminating the influence of the phase characteristic unique to the receiving apparatus 100. Note that the frequencies not included in the calibration signal CA may be obtained by using a known interpolation method in the correction amount calculation unit 44, as indicated by the broken line in FIG.

  The operation according to the above configuration is as follows. First, in the calibration period, the switch 12 selects the calibration signal CA. This signal is input to the digital signal processing circuit 18 through the frequency converter 14 and the A / D converter 16. During this time, a delay characteristic peculiar to the receiving apparatus 100 occurs due to group delay or the like. The output of the A / D converter 16 is converted into a baseband by the quadrature detector 30 of the digital signal processing circuit 18, and an I / Q component is output. The fast Fourier transformer 42 performs FFT on the I / Q component and outputs phase characteristic data X. The correction amount calculation unit 44 calculates a correction coefficient Y that is a correction amount for canceling the phase characteristic in the above-described procedure, and stores it in the memory 46. Thereafter, the correction amount calculation unit 44 switches the selection signal SW.

  The switch 12 outputs the radio wave received by the antenna 10 by switching the selection signal SW. This radio wave is input to the digital signal processing circuit 18 through the frequency converter 14 and the A / D converter 16. The quadrature detector 30 of the digital signal processing circuit 18 converts the output of the A / D converter 16 into baseband and I / Q components. The calibration unit 48 reads the correction coefficient Y from the memory 46 and outputs it to the multiplier 50. The output of the fast Fourier transformer 42 is input thereto, and the final signal Dout is output in a state where the delay characteristic unique to the receiving apparatus 100 disappears due to the action of the correction coefficient Y. Thereafter, the final signal Dout is notified to the positioning center 104 through a circuit (not shown).

  According to this embodiment, the following effects can be obtained. First, a simple configuration realizes a calibration function that can be easily incorporated into a device. This is an effect obtained by interpolating discretely obtained phase characteristic data for each frequency component of the calibration signal. Furthermore, according to the embodiment, since calibration is performed by digital signal processing, reproducibility and stability are high. In addition, since the delay characteristic unique to the receiving apparatus 100 is removed, the positioning center 104 can perform highly accurate positioning.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  As an example, in the embodiment, the correction coefficient Y is obtained so that the phase characteristic is zero, but it is not necessarily required to be zero. The delay characteristic is obtained by differentiating the phase characteristic with respect to the frequency, and it is sufficient that the delay characteristic is constant. Therefore, the phase characteristic is af + b (where a is constant, f is the frequency, and b is an arbitrary constant). It may be corrected. That is, a correction coefficient Y that satisfies XY = af + b may be used.

  In the embodiment, the group delay of the filter is considered as a problem. However, the present invention is not necessarily limited to the group delay, and a variation in an arbitrary element that processes radio waves may be a problem. In the embodiment, calibration can be performed including such an effect.

It is a figure showing the whole positioning system composition concerning an embodiment. It is a figure which shows the structure of the receiver which concerns on embodiment. It is a figure which shows the structure of the digital signal processing circuit of a receiver. FIG. 4A to FIG. 4C are diagrams each showing a configuration of the calibration signal generator according to the embodiment. FIGS. 5A and 5B are diagrams showing examples of the frequency spectrum of the calibration signal. It is a figure which shows typically the phase characteristic data X thrown into a correction amount calculation part. It is a figure which shows typically the phase characteristic data XY after making the correction coefficient Y calculated | required by the correction amount calculation part act.

Explanation of symbols

  12 switches, 14 frequency converters, 18 digital signal processing circuits, 20 calibration signal generators, 30 quadrature detectors, 42 fast Fourier transforms, 44 correction amount calculation units, 48 calibration units, 100 receivers, 104 positioning centers, 200 Positioning system.

Claims (5)

Frequency conversion means for receiving radio waves emitted from a radio wave source, performing frequency conversion, and outputting a baseband signal;
Fourier transform means for expanding the baseband signal into frequency components;
Calibration means for canceling the phase characteristics inherent in the output of the Fourier transform means, based on the correction amount obtained by passing the calibration signal through the frequency transform means,
A receiving apparatus comprising: A selection means for selecting one of a reception signal of a radio wave emitted from a radio wave source and a calibration signal;
Frequency conversion means for performing frequency conversion on the output of the selection means and outputting a baseband signal separated into an in-phase component and a quadrature component;
Fourier transform means for applying a Fourier transform to the in-phase component and the quadrature component, and expanding the set to a set of complex frequency components;
Correction amount calculating means for calculating and holding a correction amount for canceling the phase characteristic inherent in the output of the Fourier transform means;
Calibration means for applying the calculated and held correction amount to the output of the Fourier transform means;
The correction amount calculation means calculates and holds the correction amount when the selection means selects the calibration signal, and the calibration means calculates the correction amount when the selection means selects the radio wave reception signal. Is applied to the output of the Fourier transform means.   3. The receiving apparatus according to claim 1, further comprising means for generating the calibration signal by applying a rectangular modulation wave to a predetermined carrier signal.   4. The apparatus according to claim 1, wherein the phase characteristic is caused by at least an internal characteristic of the frequency converting means. Calculating a correction amount for canceling the phase characteristic based on the phase characteristic obtained by passing the calibration signal through the reception processing system;
Receiving radio waves emitted by radio sources and converting them to baseband signals;
Expanding a baseband signal obtained by the conversion into frequency components;
Causing the correction amount to act on the developed frequency component;
A receiving method comprising:

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