Receiving array antenna device, calibration method in receiving array antenna device, receiving array antenna system, calibration program, and recording medium

Abstract

This receiving array antenna device is provided with: a plurality of excitation coefficient multiplication units (411) to (41N) that each receive, distinctly for receiving systems respectively corresponding to a plurality of element antennas (11) to (1N) in an array antenna (1) comprising the plurality of element antennas (11) to (1N), digital received signals from received signals received respectively by the plurality of element antennas (11) to (1N), multiply the received digital received signals by a corrected excitation coefficient, and obtain corrected digital received signals; a complex adder (42) for summing the corrected digital received signals respectively obtained by the plurality of excitation coefficient multiplication units (411) to (41N) and forming a receiving beam; a correlation detection unit (46) that receives, distinctly for the receiving systems respectively corresponding to the plurality of element antennas (11) to (1N), digital calibration signals from calibration signals received respectively by the plurality of element antennas (11) to (1Ｎ), and obtains receiving system-specific cross-correlation values with regard to the digital calibration signals in the plurality of receiving systems with respect to a digital calibration signal in a reference receiving system that is one receiving system among the plurality of receiving systems; an inter-element-system error calculation unit (47) for subtracting a noise correlation value with respect to noise of the reference receiving system that reaches the correlation detection unit (46) from an element antenna (1n) from an autocorrelation value that is the cross-correlation value in the reference receiving system, thus obtaining an amended autocorrelation value, obtaining an inter-element-system error that is a relative difference in the receiving system-specific cross-correlation values obtained by the correlation detection unit (46) with reference to the amended autocorrelation values, for each distinct receiving system with respect to each of the plurality of receiving systems, and using the resulting inter-element-system error to obtain a correction factor; and an excitation coefficient correction unit (48) for obtaining, with respect to each of the plurality of receiving systems, a corrected excitation coefficient for the excitation coefficient multiplication units from the correction factor obtained by the inter-element-system error calculation unit (47) for each distinct receiving system and a preset receiving system-specific excitation coefficient.

Description

Receiving array antenna device, calibration method for receiving array antenna device, receiving array antenna system, calibration program, and recording medium

[0001] The present disclosure relates to a receiving array antenna device that receives an analog received signal using an array antenna having a plurality of antenna elements and converts the signal into a digital received signal for processing, a calibration method for the receiving array antenna device, a receiving array antenna system, a calibration program, and a recording medium.

[0002] Patent Document 1 discloses a satellite receiver that uses digital beam forming (DBF) to receive signals using an array antenna, convert the received analog signals into digital signals, and control excitation coefficients through digital signal processing. Patent Document 1 also discloses a satellite receiver that can improve communication efficiency by calibrating errors between element systems that occur within the device, namely gain error, delay error, and phase error.

[0003] Specifically, Patent Document 1 discloses a satellite receiver that includes N demultiplexing sections that demultiplex digital received signals obtained by converting calibration signals received by each of N receiving antenna elements into digital signals, into a plurality of subchannel signals of a predetermined band, N excitation coefficient multipliers that multiply each of the plurality of subchannel signals by an excitation coefficient, and a complex adder that adds together the plurality of subchannel signals after being multiplied by the excitation coefficients for each subchannel signal of the same band, one of the N demultiplexing sections being a reference demultiplexing section, a correlation detection section that calculates a cross-correlation value for each subchannel signal output from each demultiplexing section different from the reference demultiplexing section, with respect to a subchannel signal of the same band output from the reference demultiplexing section, and an excitation coefficient generation section that generates corrected excitation coefficients that are excitation coefficients to be multiplied by the subchannel signals by the excitation coefficient multipliers, based on the cross-correlation value calculated by the correlation detection section and excitation coefficients that are prepared in advance to form a desired receiving beam.

[0004] International Publication No. 2021 / 152660

[0005] The inventors further studied calibration that generates corrected excitation coefficients using cross-correlation values ​​and found that when noise superimposed on the calibration signal due to the surrounding environment and the state of the equipment from the receiving antenna elements to the correlation detector is large, that is, when the power ratio of the calibration signal to noise (S / N ratio) is small, a large error occurs in the amplitude estimation values ​​between the systems. As a result, when the power ratio of the calibration signal to noise is small, the accuracy of the corrected excitation coefficients obtained by calibration decreases.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a receiving array antenna device in which the accuracy of excitation coefficients after correction by calibration is high even when the power ratio of the calibration signal to noise is small.

[0007] A receiving array antenna device according to the present disclosure includes a plurality of excitation coefficient multipliers that receive digital reception signals from reception signals received by each of a plurality of element antennas in an array antenna having a plurality of element antennas, each of which receives a digital reception signal for each of the plurality of element antennas in a separate reception system corresponding to each of the plurality of element antennas, and multiplies the received digital reception signal by a corrected excitation coefficient to obtain a corrected digital reception signal; a complex adder that adds the corrected digital reception signals obtained by the plurality of excitation coefficient multipliers to form a reception beam; and a digital calibration signal that receives a digital calibration signal from a calibration signal received by each of the plurality of element antennas in a separate reception system corresponding to each of the plurality of element antennas, and multiplies the digital calibration signal by a digital calibration signal in a reference reception system that is one of the plurality of reception systems. an inter-element system error calculation unit that calculates an inter-element system error, which is a relative difference between the cross-correlation values ​​for each of the plurality of receiving systems obtained by the correlation detection unit using the corrected autocorrelation value for each of the plurality of receiving systems, based on the cross-correlation value for each of the plurality of receiving systems; and an excitation coefficient correction unit that calculates a corrected excitation coefficient for the excitation coefficient multiplication unit using the correction coefficient obtained by the inter-element system error calculation unit for each of the plurality of receiving systems and a preset excitation coefficient for each of the plurality of receiving systems.

[0008] According to the present disclosure, the cross-correlation value is corrected using a noise correlation value for noise in the reference system, so even if the power ratio of the calibration signal to the noise is small, the accuracy of the excitation coefficient after correction by calibration is high, and calibration can be achieved with high precision.

[0009] FIG. 1 is a configuration diagram showing a receiving array antenna apparatus according to a first embodiment. FIG. 2 is a flowchart showing a calibration method in the receiving array antenna apparatus according to the first embodiment. FIG. 3 is a diagram showing the hardware configuration of a DBF receiving unit in the receiving array antenna apparatus according to the first embodiment. FIG. 4 is a configuration diagram showing a receiving array antenna apparatus according to a second embodiment. FIG. 5 is a configuration diagram showing a receiving array antenna apparatus according to a third embodiment. FIG. 6 is a diagram for explaining sequence control in the receiving array antenna apparatus according to the third embodiment. FIG. 7 is a configuration diagram showing a receiving array antenna apparatus according to a fourth embodiment. FIG. 8 is a diagram showing signals after demultiplexing into sub-channels in a digital calibration signal in the receiving array antenna apparatus according to the fourth embodiment. FIG. 9 is a configuration diagram showing a receiving array antenna apparatus according to a fifth embodiment.

[0010] First Embodiment A receiving array antenna apparatus according to a first embodiment will be described with reference to Figs. 1 to 3. The receiving array antenna apparatus according to the first embodiment is used as a satellite repeater in a satellite communication system. The receiving array antenna apparatus according to the first embodiment comprises a plurality of element antennas 1. １ ~1 Ｎ An array antenna 1 having a plurality of receivers 2 １ ~2 Ｎ and a plurality of analog-to-digital converters (ADCs) 3. １ ~3 Ｎ and a digital beam forming (DBF) receiver 4.

[0011] The DBF receiver 4 includes a plurality of excitation coefficient multipliers 41 １ ~41 Ｎ a complex adder 42, a noise correlation value storage unit 43, a correction coefficient storage unit 44, an excitation coefficient storage unit 45, a correlation detection unit 46, an element-system error calculation unit 47, and a complex multiplier 48 １ ~48 Ｎ and an excitation coefficient correction unit 48 having the following formula: N is a natural number of 2 or more.

[0012] In the following description, 1 to N each represent a plurality of element antennas 1 １ ~1 Ｎ Each of the reference reception systems indicates one corresponding reception system. n indicates reception systems 1 to N, and m indicates a reference reception system selected from the reception systems 1 to N. In the first embodiment, the reference reception system is the reception system with the maximum received power, but any reference reception system can be selected. When it is not necessary to explain each component individually, the number n will be used for the explanation.

[0013] First, before explaining each component, the error between the element systems will be explained. １ ~1 Ｎ The reception patterns received by each of the element antennas 1 １ ~1 Ｎ This is an error between element systems due to the characteristic difference between element antennas (hereinafter referred to as "error between element systems due to the characteristic difference between element antennas"), which indicates the difference in power and phase determined by the positional relationship between each antenna and the ground station and the calibration ground station.

[0014] Second, there are errors between element systems that occur within the device, that is, errors between element systems due to gain error, delay error, and phase error (hereinafter referred to as errors between element systems that occur within the device). Third, there are noises that affect the estimation of errors between element systems that occur within the device, such as noises caused by the surrounding environment and the antenna element 1. １ ~1 Ｎ This is a noise component that is superimposed on the digital calibration signal depending on the state of the equipment from the calibration unit 40 to the correlation detection unit 46.

[0015] The receiving array antenna apparatus according to the first embodiment eliminates inter-element system errors due to differences in characteristics between element antennas using excitation coefficients that are preset for each receiving system. Furthermore, inter-element system errors that occur within the apparatus are eliminated by obtaining a cross-correlation value between the digital calibration signal for each receiving system and a reference calibration signal for the digital calibration signal for each receiving system. Furthermore, when obtaining inter-element system errors that occur within the apparatus, noise components are removed, thereby improving the accuracy of the calculated inter-element system errors.

[0016] Multiple element antennas 1 １~1 Ｎ Each (hereinafter, unless there is a need to distinguish between them, they will be referred to as element antenna 1 ｎ The calibration ground station 100 receives a received signal, which is an actual communication signal (transmitted signal) consisting of radio waves (in the radio frequency (RF) band) from a ground station (not shown), and a calibration signal 110 consisting of radio waves from the calibration ground station 100.

[0017] Multiple element antennas 1 １ ~1 Ｎ Since the received signal and the calibration signal 110 have spatial spread, each antenna receives the same received signal and the calibration signal 110. ｎ The power and phase of the received signal and calibration signal 110 at element antenna 1 ｎ The difference in power and phase determined by the reception pattern and the positional relationship between the ground station and the calibration ground station 100 is calculated by the element antenna 1. ｎ This is called the difference in characteristics between the two.

[0018] Although the expressions "received signal" and "calibration signal" are used, this does not mean that the received signal and calibration signal are simultaneously received and processed, but simply means that the received signal and calibration signal are received. This also applies to the following explanation.

[0019] Multiple receivers 2 １ ~2 Ｎ Each (hereinafter, unless there is a need to distinguish between them, ｎ (explained as) is a plurality of element antennas 1 for each receiving system n. １ ~1 Ｎ A receiver 2 is provided corresponding to each of them. ｎ is the corresponding element antenna 1 ｎ The RF band received signal and the calibration signal from the receiver 2 are frequency converted and converted into an electrical signal, and then converted into an analog received signal in the baseband frequency band suitable for subsequent processing. ｎ adjusts the power of the analog received signal to an appropriate value.

[0020] Multiple ADCs １ ~3 ＮEach (hereinafter, unless there is a need to distinguish between them, ADC3 ｎ (explained as) is a plurality of receivers 2 for each receiving system n. １ ~2 Ｎ The ADC3 is electrically connected to the ADC3. ｎ is the corresponding receiver 2 ｎ The analog reception signal and analog calibration signal from the DBF receiver 4 are converted into digital signals, and the digital reception signal and digital calibration signal are output to the DBF receiver 4 .

[0021] The receiver group 2 and the ADC group 3 convert the received signals and calibration signals, which are radio waves received by the array antenna 1, into baseband frequency bands, and then digitally convert the analog received signals and analog calibration signals, which are electrical signals, and then transmit the digitally converted digital received signals and digital calibration signals to the multiple element antennas 1 in the array antenna 1. １ ~1 Ｎ A reception signal preprocessing unit is configured to output to the DBF receiving unit 4 for each of the corresponding reception systems n.

[0022] The DBF receiver 4 has a function of forming a receive beam (beam former) and a function of obtaining corrected excitation coefficients (excitation coefficient generator). The beam former in the DBF receiver 4 uses corrected excitation coefficients to obtain corrected digital receive signals from the digital receive signals output for each of n receive systems from the receive signal preprocessor for the receive signals consisting of actual communication signals from a ground station received by the array antenna 1, and forms a calibrated receive beam by adding the obtained corrected digital receive signals for each of n receive systems. The receive beam formed by the beam former is a receive beam in which, by using the corrected excitation coefficients, errors between element systems due to characteristic differences between element antennas and errors between element systems generated within the device based on the hardware characteristics of the receive signal preprocessor are calibrated.

[0023] The excitation coefficient generator in DBF receiver 4 first determines one of the multiple reception systems 1 to N as a reference reception system m, and determines the digital calibration signal output from the reception signal pre-processing unit in reference reception system m as the reference calibration signal for calibration signal 110 received by array antenna 1 from calibration ground station 100, and obtains a cross-correlation value for the digital calibration signal for each of reception systems n with respect to the reference calibration signal for the digital calibration signal for each of reception systems n output from the reception signal pre-processing unit. The correlation value for the digital calibration signal of reference reception system m with respect to the reference calibration signal for the digital calibration signal of reference reception system m is also called a cross-correlation value, and when it is necessary to distinguish it, it is called an auto-correlation value.

[0024] Next, the excitation coefficient generator subtracts the noise correlation value for the noise of the reference receiving system m from the autocorrelation value in the reference receiving system m to obtain a corrected autocorrelation value. Furthermore, the excitation coefficient generator obtains an inter-element system error, which is a relative difference in the cross-correlation value for each receiving system n based on the corrected autocorrelation value, and obtains a correction coefficient using the obtained inter-element system error.

[0025] The excitation coefficient generator obtains the relative difference in cross-correlation values ​​using a corrected autocorrelation value obtained by subtracting the noise correlation value for the noise of the reference receiving system m. Therefore, even when the noise component is large and the power ratio of the calibration signal to noise is small, the relative difference in cross-correlation values ​​can be calculated with high accuracy, and as a result, the error between the element systems can be obtained with high accuracy.

[0026] The excitation coefficient generator obtains corrected excitation coefficients for each of the n receiving systems to be sent to the beam former using the correction coefficients for each of the n receiving systems and preset excitation coefficients for each of the n receiving systems. The preset excitation coefficients are excitation coefficients for forming receiving beams, and are excitation coefficients that allow the beam former to obtain desired receiving beams when it is assumed that there is no error between the receiving systems in the received signal preprocessing unit.

[0027] The preset excitation coefficient is ｎ and the reception pattern received by element antenna 1 ｎ and the element antenna 100, which indicates the difference in power and phase determined by the positional relationship between the element antenna 100 and the ground station and the calibration ground station 100. ｎThe correction coefficient for each n-th receiving system is a coefficient that can calibrate the inter-element system error that occurs inside the device, which is the difference in characteristics between n-th receiving systems in the received signal pre-processing unit. Note that the inter-element system error, which is the relative difference in cross-correlation values, includes the inter-element system error due to the difference in characteristics between the element antennas and the inter-element system error that occurs inside the device, and the excitation coefficient generation unit removes the inter-element system error due to the difference in characteristics between the element antennas before obtaining the correction coefficient.

[0028] The beam forming unit in the DBF receiver 4 includes a plurality of excitation coefficient multipliers 41 １ ~41 Ｎ and a complex adder 42. The excitation coefficient generation unit in the DBF receiver 4 includes a correlation detection unit 46, an inter-element system error calculation unit 47, and an excitation coefficient correction unit 48.

[0029] A plurality of excitation coefficient multipliers 41 １ ~41 Ｎ Each of them (hereinafter, unless there is a need to distinguish between them, they will be referred to as the excitation coefficient multiplication unit 41 ｎ ) corresponds to the ADC 3 in the ADC group 3 that constitutes the received signal pre-processing section. ｎ and the corrected excitation coefficients of the corresponding receiving system n from the excitation coefficient generating unit in the DBF receiving unit 4. The corrected excitation coefficients are complex numbers.

[0030] Excitation coefficient multiplier 41 ｎ The complex adder 42 multiplies the corresponding digital received signal by the corrected excitation coefficient to obtain a corrected digital received signal for each receiving system n. １ ~41 Ｎ The corrected digital received signals for each of the n receiving systems are added together, that is, the corrected digital received signals are vector-synthesized to form a receiving beam.

[0031] The correlation detector 46 detects the correlation between the corresponding ADC 3 in the ADC group 3 that constitutes the received signal pre-processing unit. ｎThe digital calibration signal from the reference receiving system m is received for each of n receiving systems, one of the plurality of receiving systems 1 to N is designated as a reference receiving system m, the digital calibration signal in the reference receiving system m is designated as a reference calibration signal, and a cross-correlation value for each of n receiving systems with respect to the reference calibration signal for the digital calibration signal in the receiving system n is obtained.

[0032] The correlation detection unit 46 selects the reception system with the greatest reception power among the reception powers of the digital calibration signals in each of the reception systems n as the reference reception system m. Note that the correlation detection unit 46 may use the digital calibration signal in the reception system that has been set in advance as the reference reception system m as the reference calibration signal. The cross-correlation value detected by the correlation detection unit 46 is obtained by calculating a correlation vector between the digital calibration signal of the reception system n and the reference calibration signal.

[0033] The inter-element system error calculation unit 47 has the following functions: The first function is to read out the noise correlation value for the reference reception system stored in the noise correlation value storage unit 43, and to obtain a corrected autocorrelation value by subtracting the read-out noise correlation value from the autocorrelation value for the reference reception system m obtained by the correlation detection unit 46.

[0034] The noise correlation value for the reference receiving system is ｍ The noise correlation value is a noise correlation value (correlation value due to noise power) of the noise of each receiving system n with respect to the noise of the reference receiving system m from the correlation detector 46. The noise correlation value is a value obtained by measuring or calculating the noise component in advance, or in the first embodiment, the noise power (amplitude of the noise component).

[0035] The second function is a function of obtaining, for each of a plurality of receiving systems n, an inter-element system error, which is the relative difference in cross-correlation values ​​for each receiving system n obtained by the correlation detection unit 46 using as a reference the corrected autocorrelation value for the reference receiving system m obtained by the first function for each receiving system n. The inter-element system error, which is the relative difference in cross-correlation values ​​for each receiving system n obtained by the correlation detection unit 46 using as a reference the autocorrelation value for the reference receiving system m, includes inter-element system errors due to differences in characteristics between the element antennas and inter-element system errors generated within the device. Furthermore, because the relative difference in cross-correlation values ​​is obtained using the corrected autocorrelation value, even when the noise component is large and the power ratio of the calibration signal to noise is small, the relative difference in cross-correlation values ​​can be calculated with high accuracy, and as a result, the inter-element system error can be obtained with high accuracy.

[0036] The third function is a function of calculating a final inter-element system error by removing the inter-element system error due to the characteristic difference between the element antennas from the inter-element system error obtained by the second function. The inter-element system amplitude error in the final inter-element system error is a value obtained by dividing the inter-element system amplitude error for each receiving system n in the inter-element system error obtained by the second function by the amplitude difference between the amplitude of the digital calibration signal in the reference receiving system m and the amplitude of the digital calibration signal in the receiving system n relative to the amplitude of the digital calibration signal in the reference receiving system m.

[0037] The final inter-element system phase error in the inter-element system error is a value obtained by subtracting the phase difference between the phase of the digital calibration signal in the reception system n, using the phase of the digital calibration signal in the reference reception system m as a reference, from the inter-element system phase error for each reception system n in the inter-element system error obtained by the second function. When there is no need to distinguish between the inter-element system amplitude error and the inter-element system phase error, both are collectively referred to as the inter-element system error.

[0038] The fourth function is to calculate a correction coefficient for correcting the inter-element system error occurring inside the device using the final inter-element system error. The correction coefficient for each of the n receiving systems calculated by the inter-element system error calculation unit 47 is stored in the correction coefficient storage unit 44. The correction coefficient obtained by the inter-element system error calculation unit 47 is less affected by noise, has high accuracy, and is a coefficient that can cancel the inter-element system error occurring inside the device.

[0039] Complex multiplier 48 １ ~48 Ｎ (Hereinafter, unless there is a need to distinguish between them, the complex multiplier 48 ｎ The excitation coefficient correction unit 48 having the excitation coefficients (described as excitation coefficients) calculates the excitation coefficients of the excitation coefficient multiplier 41 by using the preset excitation coefficients for each of the n receiving systems stored in the excitation coefficient storage unit 45 and the correction coefficients for each of the n receiving systems stored in the correction coefficient storage unit 44. １ ~41 Ｎ The corrected excitation coefficients for each receiving system n are obtained.

[0040] Complex multiplier 48 ｎ is a signal obtained by multiplying the excitation coefficient of the receiving system n stored in the corresponding excitation coefficient storage unit 45 by the correction coefficient of the receiving system n stored in the correction coefficient storage unit 44. ｎ The corrected excitation coefficient of the receiving system n is given to the excitation coefficient correcting unit 48 using the correction coefficient obtained by the inter-element system error calculating unit 47. The corrected excitation coefficient obtained by the excitation coefficient correcting unit 48 using the correction coefficient obtained by the inter-element system error calculating unit 47 is also less affected by noise, has high accuracy, and is a coefficient that can cancel out the inter-element system error due to the characteristic difference between the element antennas and the inter-element system error generated inside the device.

[0041] Next, a calibration method for the receiving array antenna apparatus according to the first embodiment will be described with reference to Fig. 2. Excitation coefficients for n receiving systems are stored in advance in the excitation coefficient storage unit 45, and noise correlation values ​​(correlation values ​​due to noise power) of noise for n receiving systems are stored in the noise correlation value storage unit 43.

[0042] The array antenna 1 receives a calibration signal 110 from a calibration ground station 100, and outputs the calibration signal 110 to the element antenna 1 from a reception signal pre-processing unit configured by a receiver group 2 and an ADC group 3. ｎ When the correlation detector 46 in the DBF receiver 4 receives the digital calibration signals for n reception systems corresponding to the above, the following process is performed in step ST1.

[0043] The correlation detector 46 receives the digital calibration signal R ｎ [k] is expressed by the following equation (1).

[0044] In the above equation (1), k is the frequency (subchannel number), A ｎ [k] is the amplitude of the calibration signal of the receiving system n, φ ｎ [k] is the phase of the calibration signal of the receiving system n, N ｎ [k] denotes the noise component of the calibration signal of the receiving system n.

[0045] The correlation detector 46 receives the calibration signal R ｍ [k] is expressed by the following equation (2): The reference receiving system m is one of the receiving systems n, and in the first embodiment, the receiving system with the maximum received power among the receiving systems n is taken as the reference receiving system m, and the calibration signal R ｍ [k] is the calibration signal of the receiving system that maximizes the received power.

[0046] In the above equation (2), k is the frequency (subchannel number), A ｍ [k] is the amplitude of the calibration signal of the reference receiving system m, φ ｍ [k] is the phase of the calibration signal of the reference receiving system m, N ｍ [k] denotes the noise component of the calibration signal of the reference receiving system m.

[0047] In step ST1, the correlation detector 46 detects the calibration signal R ｍ [k] and the digital calibration signal R in the receiving system n shown by the above equation (1) ｎ [k] is used to calculate the cross-correlation value (correlation vector) in the receiving system n.

[0048] The cross-correlation value in the receiving system n calculated by the correlation detector 46 and expressed by the following equation (3) is expressed by the following equation (4).

[0049] In the cross-correlation value in the receiving system n expressed by the above equation (4), the cross-correlation value in the reference receiving system m is an auto-correlation value, and the auto-correlation value in the reference receiving system m shown by the following equation (5) is expressed by the following equation (6).

[0050] Step ST1 is a step in which the correlation detection unit 46 obtains the cross-correlation value in the receiving system n shown by the above formula (4) and the auto-correlation value in the reference receiving system m shown by the above formula (6). In short, step ST1 is a step in which the correlation detection unit 46 obtains (calculates) the cross-correlation value for each receiving system n with respect to the digital calibration signal in the reference receiving system m, which is one receiving system among the multiple receiving systems, for the digital calibration signal in each of the multiple receiving systems n.

[0051] The cross-correlation value in receiving system n and the auto-correlation value in reference receiving system m are ensemble averages, and correlation components between low-correlation signals and noise components, and correlation components between noises in different systems, can be ignored. Therefore, the relative difference in the amplitude of the cross-correlation value in receiving system n, with the amplitude of the auto-correlation value in reference receiving system m as a reference, is calculated as shown in the following equation (7) (the left side of equation (7) below). Furthermore, the relative difference in the phase of the cross-correlation value in receiving system n, with the phase of the auto-correlation value in reference receiving system m as a reference, is calculated as shown in the following equation (8) (the left side of equation (8) below).

[0052]

[0053] The relative difference in the amplitude of the cross-correlation value in the receiving system n with respect to the amplitude of the auto-correlation value in the reference receiving system m as a reference indicates an amplitude error between the element systems. The relative difference in the phase of the cross-correlation value in the receiving system n with respect to the phase of the auto-correlation value in the reference receiving system m as a reference indicates a phase error between the element systems.

[0054] Here, in the case where there is no noise component, that is, in the ideal case, the noise component N ｍ [k] is 0, and the relative difference in the amplitude of the cross-correlation value in the receiving system n, with the amplitude of the auto-correlation value in the reference receiving system m as the reference, is calculated as follows: (9) Furthermore, the phase of the relative difference in the phase of the cross-correlation value in the receiving system n, with the auto-correlation value in the reference receiving system m as the reference, is calculated as follows: (10)

[0055]

[0056] However, in reality, noise components (noise power) are superimposed in the received signal preprocessing section, so the relative difference in the amplitude of the cross-correlation value in the receiving system n with respect to the amplitude of the auto-correlation value in the reference receiving system m is expressed as the noise component N of the digital calibration signal in the reference receiving system m in the denominator, as shown in the above equation (7). ｍ [k] (the amplitude (power value) of the noise component) exists.

[0057] Therefore, the cross-correlation value of the digital calibration signal in the receiving system n with respect to the reference calibration signal calculated by the correlation detector 46 is calculated by adding the noise component N of the calibration signal in the reference receiving system m. ｍ When the noise superimposed on the signal is large and the signal-to-noise power ratio (S / N ratio) is small, the effect becomes significant and can result in a large error.

[0058] In step ST2, the element-to-element system error calculation unit 47 calculates the noise correlation value N' for the reference receiving system stored in the noise correlation value storage unit 43. ｍ [k] is read out, and the noise correlation value N for the reference receiving system m is read out from the autocorrelation value for the reference receiving system m obtained by the correlation detection unit 46. ｍ The corrected autocorrelation value (the left side of the following equation (11)) calculated by the element-to-system error calculation unit 47 is expressed by the following equation (11).

[0059]

[0060] In step ST3, the inter-element system error calculation unit 47 calculates the relative difference in amplitude of the cross-correlation value in the reception system n using the amplitude of the corrected autocorrelation value in the reference reception system m as a reference, which is expressed by the following equation (12): Also, the relative difference in phase of the cross-correlation value in the reception system n using the phase of the corrected autocorrelation value in the reference reception system m as a reference is calculated as the following equation (13):

[0061]

[0062] The relative difference in the amplitude of the cross-correlation value in receiving system n, with the amplitude of the corrected autocorrelation value in reference receiving system m as a reference, indicates the inter-element system amplitude error with reduced noise components in amplitude. The relative difference in the phase of the cross-correlation value in receiving system n, with the phase of the corrected autocorrelation value in reference receiving system m as a reference, indicates the inter-element system phase error. Note that the noise component is mainly noise power, which affects amplitude but not phase, so the inter-element system phase error shown by equation (13) above is the same as the inter-element system phase error when there is no noise component, shown by equation (10) above.

[0063] In the above equation (12), Δ is the error of the noise component in the digital calibration signal in the reference receiving system m. Δ is the square value of the noise correlation value of the autocorrelation value in the reference receiving system m |N ｍ [k] | ２ From the squared value |N' of the noise correlation value of the corrected autocorrelation value in the reference receiving system m ｍ [k] | ２ is a value obtained by subtracting

[0064] Although Δ is not 0 strictly, if the settings of the components constituting the received signal preprocessing unit are not changed, the noise correlation value for the reference receiving system stored in the noise correlation value storage unit 43 can be approximated to be almost the same as the noise component (noise power) superimposed on the calibration signal in the reference receiving system m. As is clear from the above equations (12) and (13), the influence of the noise component is reduced from the relative difference in the cross-correlation value of receiving system n using the autocorrelation value in the reference receiving system m as the reference, that is, the error between the element systems.

[0065] In step ST3, the inter-element system error calculation unit 47 calculates a relative difference based on the corrected autocorrelation value for each of the cross-correlation values ​​for each of the n receiving systems, thereby obtaining an inter-element system error for each receiving system. In step ST4, the inter-element system error calculation unit 47 removes the inter-element system error due to the characteristic difference between the element antennas from the inter-element system error obtained in step ST3 to determine a final inter-element system error, and obtains a correction coefficient due to the final inter-element system error. The correction coefficient obtained by the inter-element system error calculation unit 47 is stored in the correction coefficient storage unit 44.

[0066] That is, the final inter-element system amplitude error is a value obtained by dividing the inter-element system amplitude error calculated by the above equation (12) by the amplitude difference (shown by the following equation (15)) between the amplitude of the digital calibration signal in the reference reception system m and the amplitude of the digital calibration signal in the reception system n, using the amplitude of the digital calibration signal in the reference reception system m as a reference.

[0067] The final inter-element system phase error is a value obtained by subtracting the phase difference (shown by the following equation (16)) between the phase of the digital calibration signal in the reference receiving system m and the phase of the digital calibration signal in the receiving system n, which is based on the phase of the digital calibration signal in the reference receiving system m, from the inter-element system phase error calculated by the above equation (13).

[0068] Steps ST3 and ST4 are steps in which the inter-element system error calculation unit 47 calculates the relative difference based on the corrected autocorrelation value for each of the cross-correlation values ​​for each of the n receiving systems to obtain inter-element system errors for each receiving system, and then obtains correction coefficients using the obtained inter-element system errors.

[0069] In step ST5, the excitation coefficient correction unit 48 reads out the excitation coefficients for the n receiving systems stored in the excitation coefficient storage unit 45 and the correction coefficients for the n receiving systems obtained by the inter-element system error calculation unit 47 and stored in the correction coefficient storage unit 44, and multiplies each of the n receiving systems by the correction coefficients for the n receiving systems corresponding to the excitation coefficients for the n receiving systems to obtain corrected excitation coefficients.

[0070] The excitation coefficients after correction obtained by the excitation coefficient correction unit 48 are multiplied by the excitation coefficient multiplication unit 41. １ ~41 Ｎ Step ST5 is a step in which the excitation coefficient corrector 48 generates corrected excitation coefficients based on the correction coefficients for each of the reception systems n and the preset excitation coefficients.

[0071] Next, the hardware configuration of the DBF receiving unit 4 in the receiving array antenna apparatus according to the first embodiment will be described with reference to Fig. 3. The DBF receiving unit 4 includes a CPU (Central Processing Unit) 401, a ROM (Read Only Memory) 402, a RAM (Random Access Memory) 403, an input interface unit 404, and an output interface unit 405. The CPU 401, ROM 402, RAM 403, input interface unit 404, and output interface unit 405 are connected to a bus 406, and data, control signals, and the like are exchanged between them via the bus 406.

[0072] The CPU 401 temporarily loads a program recorded in the ROM 402 into the RAM 403 and executes processing according to the loaded program. The ROM 402 stores various data, a program for executing processing in the DBF receiving unit 4, a processing program required to start up the DBF receiving unit 4, and the like.

[0073] The ROM 402 stores a beamforming program for executing the function of forming a receiving beam (beam forming unit) and a calibration program for executing the function of obtaining corrected excitation coefficients (excitation coefficient generating unit). The RAM 403 has a noise correlation value storage unit 43, a correction coefficient storage unit 44, and an excitation coefficient storage unit 45, and also has a storage unit for temporarily storing the programs recorded in the ROM 402.

[0074] The input interface unit 404 is an ADC3 １ ~3 Ｎ The digital receive signal and the digital calibration signal are input from each of the inputs, and the output interface unit 405 outputs the receive beam.

[0075] When the functions of the excitation coefficient generation unit including the correlation detection unit 46, the inter-element system error calculation unit 47, and the excitation coefficient correction unit 48 are realized by the CPU 401 and the RAM 403, the calibration program for the receiving array antenna apparatus, which is recorded in the ROM 402 and executed by the CPU 401, includes "a procedure for obtaining, for digital calibration signals received by a plurality of element antennas, cross-correlation values ​​for each of the plurality of receiving systems with respect to the digital calibration signals of the plurality of receiving systems relative to the digital calibration signal in a reference receiving system, which is one of a plurality of receiving systems corresponding to each of the plurality of element antennas; a procedure for obtaining a corrected autocorrelation value by subtracting a noise correlation value for the reference receiving system from the autocorrelation value for the digital calibration signal in the reference receiving system; a procedure for calculating a relative difference for each of the cross-correlation values ​​for each of the receiving systems using the corrected autocorrelation value as a reference to obtain inter-element system errors for each of the receiving systems, and obtaining correction coefficients using the obtained inter-element system errors; and a procedure for generating corrected excitation coefficients based on the correction coefficients for each of the receiving systems and a preset excitation coefficient."

[0076] As described above, the receiving array antenna apparatus according to the first embodiment has a plurality of element antennas 1 １ ~1 Ｎ A plurality of element antennas 1 in an array antenna 1 having １ ~1 Ｎ The inter-element system error calculation unit 47 obtains a corrected autocorrelation value by subtracting the noise correlation value for the reference receiving system m from the autocorrelation value in the reference receiving system m from the autocorrelation value in the reference receiving system m, and for each of the plurality of receiving systems n, obtains an inter-element system error which is the relative difference in the cross-correlation value for each receiving system n obtained by the correlation detection unit 46 using the corrected autocorrelation value for each receiving system n as a reference, and obtains a correction coefficient using the obtained inter-element system error, and the excitation coefficient correction unit 48 obtains a correction coefficient for each receiving system from the inter-element system error calculation unit 47 and a preset excitation coefficient.Therefore, even if the power ratio of the calibration signal to noise between the digital calibration signal and the noise component superimposed in the received signal pre-processing unit is small, the inter-element system error which occurs inside the device and is calculated from the relative difference between the receiving systems with respect to the reference receiving system m can be obtained with high accuracy, and as a result, the receive beam can be calibrated with high accuracy.

[0077] Embodiment 2 A receiving array antenna apparatus according to embodiment 2 will be described with reference to Fig. 4. The receiving array antenna apparatus according to embodiment 2 is a receiving array antenna apparatus compatible with an actual communication signal (transmission signal) transmitted from a ground station (not shown) in which a plurality of subchannels formed by subcarrier signals of a plurality of different frequencies are multiplexed, and a calibration signal 110 from a calibration ground station 100 in which a plurality of subchannels formed by subcarrier signals of a plurality of different frequencies are multiplexed.

[0078] The receiving array antenna apparatus according to the second embodiment differs from the receiving array antenna apparatus according to the first embodiment in that it basically has a plurality of branching sections 5 in the received signal pre-processing section. １ ~5 Ｎ 4 differs in that a branching section group 5 having the same functions as those in FIGS. 1 to 3 is arranged after the ADC group 3, but in other respects the functions are similar. Therefore, the following description will focus on the differences from the receiving array antenna apparatus according to the first embodiment. In FIG. 4, the same reference numerals as those in FIGS. 1 to 3 indicate the same or corresponding parts.

[0079] The receiving array antenna apparatus according to the second embodiment includes a plurality of branching sections 5 １ ~5 Ｎ The excitation coefficient generator in the DBF receiver 4 obtains the corrected excitation coefficient for each sub-channel demultiplexed into the bands set by each of the demultiplexers 5. １ ~5 Ｎ (Hereinafter, unless there is a need to distinguish between them, the demultiplexing unit 5 ｎ (explained as) is a plurality of ADCs 3 for each receiving system n. １ ~3 Ｎ They are electrically connected to each other.

[0080] Demultiplexer 5 ｎ is the corresponding ADC3 ｎThe digital reception signal and digital calibration signal from are demultiplexed into predetermined frequency bands, i.e., into the frequency bands of multiple sub-channels 1 to K, and the demultiplexed digital reception signals and digital calibration signals of multiple sub-channels 1 to K are output to the DBF receiver 4. 1 to K indicate the sub-channel number. k indicates the sub-channel number 1 to K, and will be described as sub-channel k unless it is necessary to distinguish between the multiple sub-channels 1 to K. K indicates a natural number of 2 or greater.

[0081] In FIG. 4, the demultiplexing unit 5 １ ~5 Ｎ Each of them is connected to the DBF receiver 4 by a single line, but the demultiplexer 5 １ ~5 Ｎ From each of the antennas, digital reception signals and digital calibration signals of multiple (K) sub-channels are input to the DBF receiver 4. ｎ From branching section 5 ｎ Each of the K branches distributed by the branching unit 5 is called a receiving branch. ｎ The group of K receiving systems distributed by the above is ｎ That is, in the second embodiment, the element antenna 1 ｎ The receiving system n corresponding to element antenna 1 ｎ The branching unit 5 corresponding to ｎ The K receiving systems are divided into groups by the formula:

[0082] A plurality of excitation coefficient multipliers 41 １ ~41 Ｎ Each of them is a branching unit 5 ｎ The excitation coefficient multiplication unit 41 corresponds to the K reception systems distributed by １１ ~41 １Ｋ、・・・、 41 Ｎ１ ~41 ＮＫ Excitation coefficient multiplication unit 41 ｎｋ is the corresponding branching unit 5 ｎ The digital received signal from the element antenna 1 is multiplied by the corresponding corrected excitation coefficient to obtain a corrected digital received signal for each receiving system nk. ｎ Receiving system n to branching unit 5ｎ The receiving system means the receiving system k distributed by

[0083] The complex adder 42 includes a complex adder 42 corresponding to a plurality of sub-channels. １ ~42 Ｋ The complex adder 42 is configured as follows: ｋ is a plurality of excitation coefficient multipliers 41 for the corresponding sub-channel k. １ｋ ~41 Ｎｋ The corrected digital received signals for each receiving system n k are added together, that is, the corrected digital received signals are vector-combined to form a receiving beam for sub-channel k. ｋ adds corrected digital received signals of sub-channel k in the same frequency band in a plurality of receiving systems n.

[0084] The correlation detection unit 46 detects the correlation between the demultiplexing unit 5 ｎ and for each sub-channel k, one of the plurality of receiving systems 11 to 1K, ..., N1 to NK is designated as a reference receiving system mk, the digital calibration signal in the reference receiving system mk is designated as a reference calibration signal, and a cross-correlation value for each receiving system nk of the digital calibration signal in the receiving system nk with respect to the reference calibration signal is obtained. The correlation detection unit 46 obtains, for each sub-channel k, the cross-correlation value for the receiving system nk shown by the above equation (4) and the auto-correlation value for the reference receiving system mk shown by the above equation (6).

[0085] The reference reception system mk is a reception system for sub-channel k selected as the reference reception system m. Note that, although a reference reception system mk is selected for each sub-channel k, it is also possible to select the reception system with the greatest reception power among the reception powers of the digital calibration signals in each of the multiple reception systems nk as the reference reception system, and use this as a reference calibration signal in the reference reception system that is common to the digital calibration signals in all sub-channels k in the reception system n.

[0086] That is, in the selected reference reception system m, the number of subchannels k may be set as the reference reception system mk, or one subchannel in the reference reception system m selected for all subchannels may be set as the reference reception system. In this case, one subchannel in the reference reception system m becomes the reference reception system mk.

[0087] The element-to-system error calculation unit 47 reads out the noise correlation value for the reference reception system m stored in the noise correlation value storage unit 43 for each subchannel k, and, as shown in the above equation (11), subtracts the read noise correlation value from the autocorrelation value for the reference reception system m obtained by the correlation detection unit 46 to obtain a corrected autocorrelation value (first function).

[0088] The element-system error calculation unit 47 obtains, for each subchannel k, an element-system error, which is the relative difference between the cross-correlation values ​​for each receiving system n k obtained by the correlation detection unit 46 using the corrected autocorrelation value for the reference receiving system m k as a reference, as shown in the above equations (12) and (13) (second function).

[0089] The inter-element system error calculation unit 47 calculates a final inter-element system error for each sub-channel k by removing the inter-element system error due to the characteristic difference between the element antennas from the inter-element system error, which is the relative difference in cross-correlation values ​​(third function). The inter-element system error calculation unit 47 calculates a correction coefficient for each sub-channel k using the final inter-element system error to correct the inter-element system error generated inside the device (fourth function). The correction coefficients for each reception system n k calculated by the inter-element system error calculation unit 47 are stored in the correction coefficient storage unit 44.

[0090] A plurality of complex multipliers 48 constituting the excitation coefficient correction unit 48 １ ~48 Ｎ Each of the complex multipliers 48 corresponds to a subchannel k. １１ ~48 １Ｋ、・・・、 48 Ｎ１ ~48 ＮＫ A plurality of complex multipliers 48 １１ ~48 １Ｋ、・・・、 48 Ｎ１ ~48 ＮＫEach of the excitation coefficient multiplication units 41 calculates the excitation coefficients for each of the reception systems n k stored in the excitation coefficient storage unit 45 and the correction coefficients for each of the reception systems n k stored in the correction coefficient storage unit 44 for each of the sub-channels k. １１ ~41 １Ｋ、・・・、 41 Ｎ１ ~41 ＮＫ The corrected excitation coefficients for each receiving system n are obtained. ｎｋ is a signal obtained by multiplying the excitation coefficient of the corresponding receiving system nk stored in the excitation coefficient storage unit 45 by the correction coefficient of the corresponding receiving system nk stored in the correction coefficient storage unit 44. ｎｋ The corrected excitation coefficient of the receiving system nk corresponding to

[0091] In the receiving array antenna apparatus according to the second embodiment, the time delay in the time domain is expressed as follows: ｎ Since this appears in the phase term in the frequency domain of the digital calibration signal distributed by

[0049] , the amount of delay can be estimated from the slope of the phase term in the frequency domain.

[0092] That is, the element-system error calculation unit 47 calculates the frequency response of the phase error between the systems using the error between the receiving systems for each sub-channel k obtained by the second function, calculates the delay amount in the time domain from the gradient of the phase with respect to the frequency, and performs temporal correction by applying the delay amount calculated for each receiving system n in the received signal pre-processing unit, thereby making it possible to correct the temporal delay difference in the time domain that occurs between the receiving systems n.

[0093]

[0094] In the receiving array antenna apparatus according to the second embodiment, the inter-element system error calculation unit 47 obtains a corrected autocorrelation value by subtracting the noise correlation value for the reference receiving system mk from the autocorrelation value in the reference receiving system mk, and obtains an inter-element system error, which is the relative difference between the cross-correlation values ​​for each receiving system n obtained by the correlation detection unit 46 using the corrected autocorrelation value for each receiving system nk as a reference, to obtain a correction coefficient by using the obtained inter-element system error, and the excitation coefficient correction unit 48 obtains a correction coefficient by using the correction coefficient obtained by the inter-element system error calculation unit 47 for each receiving system nk and a preset excitation coefficient.Therefore, even if the power ratio of the calibration signal to noise is small, the inter-element system error generated inside the apparatus, which is calculated from the relative difference between the receiving systems with respect to the reference receiving system mk, can be obtained with high accuracy, and as a result, the receiving beam for each sub-channel k can be calibrated with high accuracy.

[0095] Third Embodiment A receiving array antenna apparatus according to a third embodiment will be described with reference to Fig. 5 and Fig. 6. The receiving array antenna apparatus according to the third embodiment differs from the receiving array antenna apparatus according to the first embodiment in that the noise correlation value |N' of the noise stored in the noise correlation value storage unit 43 is ｍ [k] | ２ The difference is that the noise correlation value storage unit 43 acquires the noise correlation value in advance and stores it in the noise correlation value storage unit 43, but in other respects it has the same functions.

[0096] That is, the receiving array antenna apparatus according to embodiment 3 further comprises a calibration processing sequence control unit 6 in addition to the components of the receiving array antenna apparatus according to embodiment 1. Therefore, the following description will focus on the differences from the receiving array antenna apparatus according to embodiment 1. In Figures 5 and 6, the same reference numerals as those in Figures 1 to 3 indicate the same or corresponding parts.

[0097] The calibration processing sequence control unit 6 executes a noise power acquisition sequence for acquiring a noise correlation value before, or preferably immediately before, the DBF receiving unit 4 executes the calibration sequence, and obtains the noise correlation value |N' ｎ [k] | ２and stores it in the noise correlation value storage unit 43. The calibration sequence executed by the DBF receiver 4 includes a beam forming sequence and a corrected excitation coefficient generation sequence, similar to the receiving array antenna apparatus according to embodiment 1. The corrected excitation coefficient generation sequence is executed before the beam forming sequence.

[0098] The corrected excitation coefficient generation sequence is executed by the excitation coefficient generation unit in the DBF receiver 4. The corrected excitation coefficient generation sequence is executed by calculating the cross-correlation value in the digital calibration signal for each of the n receiving systems and the noise correlation value |N' for the noise of the n receiving system stored by the noise power acquisition sequence executed before the calibration sequence is executed. ｎ [k] | ２ The noise correlation value |N' for the noise of the reception system m selected by the correlation detection unit 46 as the reference reception system is ｍ [k] | ２ the inter-element system error which is the relative difference between the cross-correlation values ​​of the n receiving systems using the inter-element system error, the correction coefficient for the n receiving systems using the inter-element system error, and the corrected excitation coefficient for the n receiving systems using the correction coefficient and a preset excitation coefficient for the n receiving systems.

[0099] The beam forming sequence is a sequence in which corrected digital received signals for n receiving systems are obtained using corrected excitation coefficients for n receiving systems obtained by the corrected excitation coefficient generation sequence, and a calibrated receive beam is formed by adding the obtained corrected digital received signals for n receiving systems.

[0100] The noise power acquisition sequence is a sequence in which a noise power value is acquired, a noise correlation value of the noise is calculated based on the acquired noise power, and the calculated noise correlation value is stored in the noise correlation value storage unit 43. １ ~1 Ｎ In a state where the actual communication signal (transmission signal) from the ground station and the calibration signal 110 from the calibration ground station 100 are not received, the receiving array antenna device is operated, and the power of the signal output from the received signal pre-processing unit, that is, ADC3 １ ~3 ＮThe power value of the signal output from each is obtained, and the obtained results are used as the noise power N' ｎ Let [k].

[0101] The noise correlation value of noise is calculated by using the noise power N' of each receiving system n. ｎ The correlation value for [k], i.e., the noise correlation value |N' ｎ [k] | ２ The noise correlation value |N' stored in the noise correlation value storage unit 43 is calculated. ｎ [k] | ２ is the noise correlation value |N' for the reception system m selected as the reference reception system by the correlation detection unit 46. ｍ [k] | ２ is the noise correlation value |N' for the noise of the reference receiving system m read out by the element-to-system error calculation unit 47. ｍ [k] | ２ This becomes:

[0102] Immediately before executing the calibration sequence, a noise power acquisition sequence is executed to acquire the power value of the signal output from the received signal pre-processing unit, and the acquired noise power N' ｎ [k] gives the noise correlation value |N' for each receiving system n ｎ [k] | ２ and obtain the noise correlation value |N' with respect to the noise of the reference receiving system m. ｍ [k] | ２ Since the noise correlation value is obtained in the ambient environment and in the state of the equipment in the received signal pre-processing unit immediately before the calibration sequence is executed, the error between element systems can be calculated with high accuracy by the error between element systems calculation unit 47, and as a result, the receive beam can be calibrated with higher accuracy.

[0103] The receiving array antenna apparatus according to the third embodiment has the same effects as the receiving array antenna apparatus according to the first embodiment. In addition, since the noise power acquisition sequence is executed to obtain a noise correlation value for each of the n receiving systems before executing a calibration sequence including a corrected excitation coefficient generation sequence and a beam forming sequence, the inter-element system error calculation unit 47 can calculate the inter-element system error with high accuracy, and as a result, the calibration accuracy for the receiving beam is further improved.

[0104] The receiving array antenna apparatus according to the second embodiment may be configured to further include the calibration processing sequence control unit 6 in the receiving array antenna apparatus according to the third embodiment. That is, the receiving array antenna apparatus according to the second embodiment further includes the calibration processing sequence control unit 6, and the calibration processing sequence control unit 6 controls the DBF receiving unit 4 to perform the calibration sequence described in the second embodiment before, or preferably immediately before, the DBF receiving unit 4 executes the calibration sequence. １ ~1 Ｎ The noise correlation value |N′ is obtained by executing a noise power acquisition sequence for acquiring a noise correlation value in a state in which neither the actual communication signal (transmission signal) from the ground station nor the calibration signal 110 from the calibration ground station 100 is received. ｎ [k] | ２ is stored in the noise correlation value storage unit 43.

[0105] Embodiment 4. A receiving array antenna apparatus according to embodiment 4 will be described with reference to Figures 7 and 8. The receiving array antenna apparatus according to embodiment 4 differs from the receiving array antenna apparatus according to embodiment 2 in that the DBF receiver 4 further includes a sub-channel selector 410, but otherwise has similar functions. Therefore, the following description will focus on the differences from the receiving array antenna apparatus according to embodiment 2. In Figures 7 and 8, the same reference numerals as those in Figures 1 to 4 indicate the same or corresponding parts.

[0106] As a representative example, the receiving array antenna apparatus according to the second embodiment stores a noise correlation value for the receiving system for each sub-channel k in the digital calibration signal in the noise correlation value storage unit 43 before the corrected excitation coefficient generation sequence in the calibration sequence. In contrast, the receiving array antenna apparatus according to the fourth embodiment stores a noise correlation value for each sub-channel k in the receiving system for each sub-channel k in the digital calibration signal in the noise correlation value storage unit 43. １ ~1 Ｎ The noise correlation value for the reference receiving system m selected by the correlation detection unit 46 from the corresponding receiving systems is stored in the noise correlation value storage unit 43 .

[0107] The sub-channel selector 410 selects the reference reception system m selected by the correlation detector 46, as shown in FIG. ｎ a digital calibration signal having a plurality of (K) subchannels and an empty subchannel input to the DBF receiver 4 is selected, a power value of the selected empty subchannel is obtained, and the obtained result is used as the noise power N' ｎ [k], and the noise power N' ｎ The correlation value for [k], i.e., the noise correlation value |N' ｎ [k] | ２ Calculate the noise correlation value |N' in the reference receiving system m ｎ [k] | ２ to the noise correlation value storage unit 43.

[0108] The empty sub-channel in the digital calibration signal selected by the sub-channel selector 410 is a sub-channel to which no calibration signal is input, and only the noise components in the received signal pre-processing section are input to the received signal pre-processing section, i.e., the demultiplexing section 5. ｎ It is output from and can be obtained as a noise power value.

[0109] As shown in FIG. 8, the empty subchannel in the digital calibration signal selected by the subchannel selector 410 is either an empty subchannel of a frequency adjacent to the subchannel to which the digital calibration signal is input, or an empty subchannel of a frequency away from the subchannel to which the digital calibration signal is input, in order to take into account leakage of the digital calibration signal, and in a position where there is no influence of leakage of the digital calibration signal.

[0110] The correlation detection unit 46 detects the correlation between the demultiplexing unit 5 ｎ The correlation detector 46 receives the digital calibration signals distributed by the distributed signal m for each of the reception systems n, and designates one of the reception systems n as the reference reception system m. The correlation detector 46 uses each of the multiple subchannels of the reception system selected as the reference reception system m as a reference calibration signal for the reference reception system mk, and obtains a cross-correlation value for each reception system nk with respect to the reference calibration signal for the digital calibration signal in the reception system nk.

[0111] The sub-channel selector 410 selects one empty sub-channel from the digital calibration signal in the reference reception system m selected by the correlation detector 46, and calculates the power value of the selected empty sub-channel as noise power N' ｎ The sub-channel selector 410 obtains the obtained noise power N' ｎ [k] to noise correlation value |N' ｎ [k] | ２ Calculate the noise correlation value |N' in the reference receiving system m ｎ [k] | ２ to the noise correlation value storage unit 43.

[0112] The inter-element system error calculation unit 47 reads out the noise correlation value for the reference reception system m, which is obtained by the subchannel selection unit 410 and stored in the noise correlation value storage unit 43, and subtracts the read noise correlation value from the autocorrelation value in the reference reception system mk, obtained by the correlation detection unit 46, for each subchannel in the reference reception system m, to obtain a corrected autocorrelation value (first function). The noise correlation value subtracted from the autocorrelation value in the reference reception system mk is the same for each subchannel k in the reference reception system m.

[0113] The element-system error calculation unit 47 obtains, for each subchannel k, an element-system error, which is the relative difference between the cross-correlation values ​​for each receiving system n k obtained by the correlation detection unit 46 using the corrected autocorrelation value for the reference receiving system m k as a reference (second function).

[0114] The inter-element system error calculation unit 47 calculates a final inter-element system error by removing the inter-element system error due to the characteristic difference between the element antennas from the inter-element system error for each sub-channel k (third function). The inter-element system error calculation unit 47 calculates a correction coefficient for correcting the inter-element system error using the final inter-element system error for each sub-channel k (fourth function). The correction coefficient for each reception system n k calculated by the inter-element system error calculation unit 47 is stored in the correction coefficient storage unit 44.

[0115] The excitation coefficient corrector 48, like the excitation coefficient corrector 48 in the receiving array antenna apparatus according to the second embodiment, calculates, for each sub-channel k, an excitation coefficient multiplier 41 using a preset excitation coefficient for each receiving system n k stored in the excitation coefficient storage unit 45 and a correction coefficient for each receiving system n k stored in the correction coefficient storage unit 44. ｎｋ The corrected excitation coefficients for each receiving system n k are obtained.

[0116] The receiving array antenna apparatus according to the fourth embodiment has the same effects as the receiving array antenna apparatus according to the second embodiment. In addition, the sub-channel selector 410 obtains the cross-correlation value for each receiving system n k by the correlation detector 46, and simultaneously acquires the noise correlation value in the reference receiving system m. Therefore, errors between element systems that occur inside the apparatus can be obtained with higher accuracy, and as a result, the calibration accuracy for the receiving beam for each sub-channel k is further improved.

[0117] Fifth Embodiment A receiving array antenna system according to a fifth embodiment will be described with reference to Fig. 9. The receiving array antenna system according to the fifth embodiment includes a receiving array antenna device and a control station 200.

[0118] The receiving array antenna device in the receiving array antenna system according to embodiment 5 differs from embodiment 2 in that it includes a tracking telemetry command device (hereinafter referred to as TTC) 7 instead of the inter-element system error calculation unit 47 in the receiving array antenna device according to embodiment 2, but otherwise has similar functions. Therefore, the following description will focus on the differences from the receiving array antenna device according to embodiment 2 and the control station 200. In Fig. 9, the same reference numerals as those in Figs. 1 to 4 indicate the same or corresponding parts.

[0119] The received signal pre-processing unit including the receiver group 2, ADC group 3, and demultiplexing unit group 5 in the receiving array antenna apparatus is the same as the received signal pre-processing unit in the receiving array antenna apparatus according to embodiment 2, and therefore a description thereof will be omitted. The function of the correlation detection unit 46 of the DBF receiver 4 in the receiving array antenna apparatus is also the same as the function of the correlation detection unit 46 of the DBF receiver 4 in the receiving array antenna apparatus according to embodiment 2, and therefore a description thereof will be omitted.

[0120] The TTC 7 in the receiving array antenna apparatus transmits to the control station 200 the cross-correlation values ​​for each receiving system n k obtained by the correlation detection unit 46 of the DBF receiving unit 4 in the receiving array antenna apparatus, to the control station 200 which is equipped with an arithmetic unit 220 having an inter-element system error calculation unit 223, receives correction coefficients calculated based on the cross-correlation values ​​transmitted from the control station 200, and provides the correction coefficients to the excitation coefficient correction unit 48 in the DBF receiving unit 4.

[0121] That is, the TTC 7 receives the cross-correlation value in the receiving system nk and the auto-correlation value in the reference receiving system mk for each sub-channel k in the digital calibration signal from the correlation detection unit 46. The TTC 7 telemetry the cross-correlation value in the receiving system nk and the auto-correlation value in the reference receiving system mk for each sub-channel k, and transmits the telemetry signal 310 to the control station 200 via the TTC transmitting and receiving antenna 8.

[0122] The control station 200 receives the telemetrized signal 310 via the control station transmitting and receiving antenna 210, converts the telemetrized signal 310 into a digital signal indicating the cross-correlation value in the receiving system nk and the autocorrelation value in the reference receiving system mk, calculates a correction coefficient for each receiving system nk using the calculation device 220, telemetrizes the correction coefficient for each receiving system nk, and transmits the telemetrized signal 320 to the receiving array antenna device via the control station transmitting and receiving antenna 210. Having received the telemetrized signal 310, the control station 200 calculates a correction coefficient and transmits the telemetrized signal 320 to the receiving array antenna device via the control station transmitting and receiving antenna 210.

[0123] The calculation device 220 in the control station 200 includes a noise correlation value storage unit 221, a correction coefficient storage unit 222, and an element-system error calculation unit 223. The noise correlation value storage unit 221 stores noise correlation values ​​(correlation values ​​due to noise power) for each subchannel k in each receiving system n in a received signal pre-processing unit including the receiver group 2, ADC group 3, and demultiplexer group 5 in the receiving array antenna device. The noise correlation values ​​are values ​​obtained by measuring or calculating noise components in advance, or noise power (amplitude of the noise components) in the fifth embodiment.

[0124] The element system inter-error calculation unit 223 obtains the cross-correlation value in the received receiving system nk and the autocorrelation value in the reference receiving system mk, reads out the noise correlation value for the reference receiving system mk stored in the noise correlation value storage unit 221 for each subchannel k, and subtracts the noise correlation value for the reference receiving system mk from the autocorrelation value in the reference receiving system mk, as shown in the above equation (11), to obtain a corrected autocorrelation value (first function).

[0125] The element-system error calculation unit 223 obtains, for each subchannel k, an element-system error, which is the relative difference in the cross-correlation value for each receiving system n k based on the corrected autocorrelation value for the reference receiving system m k , as shown in the above equations (12) and (13) (second function).

[0126] The inter-element system error calculation unit 223 calculates a final inter-element system error by removing the inter-element system error due to the characteristic difference between the element antennas from the inter-element system error for each sub-channel k (third function). The inter-element system error calculation unit 223 calculates a correction coefficient for correcting the inter-element system error using the final inter-element system error for each sub-channel k (fourth function).

[0127] The correction coefficients for each of the receiving systems nk calculated by the inter-element system error calculation unit 223 are stored in the correction coefficient storage unit 222. The inter-element system error calculation unit 223 has substantially the same function as the inter-element system error calculation unit 47 of the DBF receiving unit 4 in the receiving array antenna apparatus according to the second embodiment.

[0128] The control station 200 converts the correction coefficients for each receiving system nk stored in the correction coefficient storage unit 222 into a telemetry signal 320 and transmits it to the receiving array antenna device via the control station transmitting and receiving antenna 210. When the TTC 7 receives the telemetry signal 320 via the TTC transmitting and receiving antenna 8, it converts the telemetry signal 320 into a digital signal indicating the correction coefficients for each receiving system nk and provides it to the excitation coefficient correction unit 48 of the DBF receiving unit 4. The complex multiplier 48 corresponding to the sub-channel k that constitutes the excitation coefficient correction unit 48 １１ ~48 １Ｋ、・・・、 48 Ｎ１ ~48 ＮＫ Each of them is multiplied by an excitation coefficient multiplier 41 using a preset excitation coefficient for each receiving system nk stored in an excitation coefficient storage unit 45 and a correction coefficient for each receiving system nk from the TTC 7 for each sub-channel k. １１ ~41 １Ｋ、・・・、 41 Ｎ１ ~41 ＮＫ The corrected excitation coefficients for each receiving system n k are obtained.

[0129] Excitation coefficient multiplier 41 of DBF receiver 4 in receiving array antenna device １１ ~41 １Ｋ、・・・、 41 Ｎ１ ~41 ＮＫ A plurality of excitation coefficient multipliers 41 configured by １ ~41 Ｎ and the complex adder 42 １ ~42 Ｋ The function of the complex adder 42 configured as above is the same as that of the excitation coefficient multiplier 41 of the DBF receiver 4 in the receiving array antenna apparatus according to the second embodiment. １ ~41 Ｎ The function of the complex adder is the same as that of the complex adder, so the explanation will be omitted.

[0130] Although the TTC transmission / reception antenna 8 is an antenna for transmission and reception, it may be a separate antenna for transmission and reception, i.e., a transmission antenna and a reception antenna. Also, although the control station transmission / reception antenna 210 is an antenna for transmission and reception, it may be a separate antenna for transmission and reception, i.e., a transmission antenna and a reception antenna.

[0131] The receiving array antenna system according to the fifth embodiment reduces the computational load of the DBF receiver 4 in the receiving array antenna device, and can accurately calculate the inter-element system error, which is the relative difference between the receiving systems with respect to the reference receiving system mk, even when the power ratio of the calibration signal to noise between the digital calibration signal and the noise component superimposed in the received signal pre-processing unit in the receiving array antenna device is small, and as a result, can calibrate the receiving beam for each sub-channel k with high accuracy.

[0132] Note that the receiving array antenna apparatus according to the first embodiment may be configured to include a TTC 7 instead of the inter-element system error calculation unit 47 in the receiving array antenna apparatus according to the first embodiment, similar to the receiving array antenna apparatus in the receiving array antenna system according to the fifth embodiment, and may be configured as a receiving array antenna system in which the cross-correlation values ​​for each of the n receiving systems obtained by the correlation detection unit 46 of the DBF receiver 4 are transmitted to the control station 200, and correction coefficients calculated based on the cross-correlation values ​​transmitted from the control station 200 are received.

[0133] In this case, the noise correlation value stored in the noise correlation value storage unit 221 of the arithmetic device 220 in the control station 200 is the same as the noise correlation value stored in the noise correlation value storage unit 43 of the DBF receiver 4 in the receiving array antenna apparatus according to embodiment 1, the function of the inter-element system error calculation unit 223 of the arithmetic device 220 in the control station 200 is the same as the function of the inter-element system error calculation unit 47 of the DBF receiver 4 in the receiving array antenna apparatus according to embodiment 1, and the correction coefficient stored in the correction coefficient storage unit 222 of the arithmetic device 220 in the control station 200 is the same as the correction coefficient stored in the correction coefficient storage unit 44 of the DBF receiver 4 in the receiving array antenna apparatus according to embodiment 1.

[0134] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted.

[0135] A receiving array antenna device according to the present disclosure is suitable for a satellite repeater in a satellite communication system.

[0136] 1 array antenna, 1 １~1 Ｎ Element antenna, 2 Receiver group, 2 １ ~2 Ｎ Receiver, 3 ADC group, 3 １ ~3 Ｎ ADC, 4 DBF receiver, 41 １ ~41 Ｎ Excitation coefficient multiplier, 42 complex adder, 43 noise correlation value memory, 44 correction coefficient memory, 45 excitation coefficient memory, 46 correlation detector, 47 element system error calculator, 48 excitation coefficient corrector, 48 １ ~48 Ｎ Complex multiplier, 410 Sub-channel selection unit, 5 Demultiplexing unit group, 5 １ ~5 Ｎ Branching unit, 6 calibration processing sequence control unit, 7 TTC, 200 control station, 220 calculation device.

Claims

1. A plurality of excitation coefficient multiplication units in an array antenna having a plurality of element antennas, each receiving a digital reception signal based on a reception signal received by each of the plurality of element antennas for each reception system corresponding to the plurality of element antennas, and each multiplying the received digital reception signal by a corrected excitation coefficient to obtain a corrected digital reception signal; a complex adder that adds the corrected digital reception signals obtained by the plurality of excitation coefficient multiplication units to form a reception beam; and a correlation detection unit that receives a digital calibration signal based on a calibration signal received by each of the plurality of element antennas for each reception system corresponding to the plurality of element antennas, and obtains a cross-correlation value for each reception system between the digital calibration signal in the plurality of reception systems and a digital calibration signal in a reference reception system that is one of the plurality of reception systems. an inter-element system error calculation unit that obtains a corrected autocorrelation value by subtracting a noise correlation value for noise in the reference receiving system extending from an element antenna to a correlation detection unit from an autocorrelation value that is a cross-correlation value in the reference receiving system, and obtains, for each of the plurality of receiving systems, an inter-element system error that is a relative difference between the cross-correlation values for each receiving system obtained by the correlation detection unit using the corrected autocorrelation value for each receiving system as a reference, and obtains a correction coefficient using the obtained inter-element system error; and an excitation coefficient correction unit that obtains, for each of the plurality of receiving systems, a corrected excitation coefficient for the excitation coefficient multiplication unit using the correction coefficient obtained by the inter-element system error calculation unit for each receiving system and a preset excitation coefficient for each receiving system.

2. The receiving array antenna device according to claim 1, wherein the digital received signals received by the complex adder for each receiving system are digital received signals having a plurality of sub-channels obtained by dividing, into predetermined frequency bands, the digital received signals for each receiving system that are due to the received signals received by each of the plurality of element antennas, and the digital calibration signals received by the correlation detection unit for each receiving system are digital calibration signals of a plurality of sub-channels obtained by dividing, into predetermined frequency bands, the digital calibration signals for each receiving system that are due to the calibration signals received by each of the plurality of element antennas.

3. A receiving array antenna device as described in claim 2, further comprising a sub-channel selection unit that selects an empty sub-channel from a digital calibration signal having a plurality of sub-channels in a reference receiving system, and obtains a noise correlation value for the noise in the reference receiving system used by the element-system error calculation unit from the power value of the selected empty sub-channel.

4. A receiving array antenna apparatus according to claim 2, wherein the selected empty sub-channel is an empty sub-channel of a frequency adjacent to the sub-channel to which the digital calibration signal is input.

5. A receiving array antenna apparatus according to claim 2, wherein the selected empty subchannel is an empty subchannel at a frequency at a position where there is no influence of leakage of a digital calibration signal from a subchannel to which a digital calibration signal is input.

6. A receiving array antenna device according to any one of claims 1 to 5, wherein the correction coefficient for each receiving system obtained by the inter-element system error calculation unit using the inter-element system error is a correction coefficient obtained by using the inter-element system error obtained by removing the inter-element system error due to characteristic differences between the plurality of element antennas from the inter-element system error, which is the relative difference between the cross-correlation values for each receiving system obtained by the correlation detection unit using the corrected autocorrelation value for each receiving system as a reference.

7. A receiving array antenna device according to any one of claims 1 to 5, further comprising: a calibration processing sequence control unit that executes a noise power acquisition sequence to obtain a noise correlation value based on noise power in the receiving systems corresponding to each of the plurality of element antennas in a state in which the plurality of element antennas do not receive digital calibration signals and digital calibration signals, before executing a calibration sequence including a corrected excitation coefficient generation sequence in which the correlation detection unit obtains a cross-correlation value, the inter-element system error calculation unit obtains a correction coefficient, and the excitation coefficient correction unit obtains a corrected excitation coefficient, and a beam forming sequence in which the plurality of excitation coefficient multiplication units obtain corrected digital received signals and the complex adder forms a receive beam.

8. A receiving array antenna device according to any one of claims 2 to 5, wherein the inter-element system error calculation unit calculates, for each sub-channel, a frequency response of the inter-element system error, which is the relative difference between the cross-correlation values for each sub-channel obtained by the correlation detection unit, with the corrected autocorrelation value used as the reference, and calculates the amount of delay in the time domain from the slope of the phase with respect to frequency.

9. A received signal pre-processing unit that converts received signals and calibration signals consisting of radio waves received by each of a plurality of element antennas in an array antenna having a plurality of element antennas into a baseband frequency band, digitally converts analog received signals and analog calibration signals consisting of electrical signals, and then outputs the digitally converted digital received signals and digital calibration signals for each of the plurality of element antennas; and a beam forming unit that obtains corrected digital received signals by using corrected excitation coefficients for the corresponding receiving systems from each of the digital received signals for each of the receiving systems output from the received signal pre-processing unit, and adds up the obtained corrected digital received signals for each of the receiving systems to form a receiving beam. and an excitation coefficient generation unit that obtains a cross-correlation value for each receiving system between the digital calibration signal for each receiving system output from the received signal pre-processing unit in a reference receiving system that is one of a plurality of receiving systems and the digital calibration signal for each receiving system output from the received signal pre-processing unit, obtains a corrected autocorrelation value by subtracting a noise correlation value for noise in the reference receiving system from an autocorrelation value that is the cross-correlation value in the reference receiving system, obtains an inter-element system error that is a relative difference in the cross-correlation value for each receiving system using the corrected autocorrelation value as a reference for each receiving system, obtains a correction coefficient using the obtained inter-element system error, and obtains the corrected excitation coefficient for each receiving system to be sent to the beam forming unit using the correction coefficient for each receiving system and a preset excitation coefficient for each receiving system.

10. An array antenna having a plurality of element antennas, wherein a plurality of excitation coefficient multipliers receive digital reception signals from reception signals received by each of the plurality of element antennas for each reception system corresponding to each of the plurality of element antennas, and each multiply the received digital reception signals by a corrected excitation coefficient to obtain corrected digital reception signals; a complex adder that adds the corrected digital reception signals obtained by the plurality of excitation coefficient multipliers to form reception beams; a reference receiver that receives digital calibration signals from calibration signals received by each of the plurality of element antennas for each reception system corresponding to each of the plurality of element antennas, and is one of the reception systems. a tracking telemetry command device that transmits, via a TTC transmitting antenna, the cross-correlation value for each receiving system obtained by the correlation detection device and an autocorrelation value that is the cross-correlation value in the reference receiving system, and receives, via a TTC receiving antenna, a correction coefficient for each receiving system; and an excitation coefficient correction unit that obtains, for each of the plurality of receiving systems, a corrected excitation coefficient for the excitation coefficient multiplier using the correction coefficient received by the tracking telemetry command device and a preset excitation coefficient for each receiving system; a control station that receives cross-correlation values for each receiving system from a tracking telemetry command device in the receiving array antenna device and auto-correlation values in the reference receiving system via a control station receiving antenna, obtains corrected auto-correlation values by subtracting a noise correlation value for noise in the reference receiving system extending from an element antenna to a correlation detection unit from the received auto-correlation value in the reference receiving system, obtains inter-element system errors for each of the plurality of receiving systems, which are relative differences in the received cross-correlation values for each receiving system using the corrected auto-correlation value as a reference for each receiving system, and obtains correction coefficients using the obtained inter-element system errors, and transmits the correction coefficients for each receiving system obtained by the calculation device via a control station transmitting antenna.

11. A calibration method for a receiving array antenna device that obtains a receiving beam by multiplying digital received signals in each of a plurality of receiving systems corresponding to each of the plurality of element antennas in an array antenna having a plurality of element antennas by corrected excitation coefficients corresponding to the plurality of receiving systems, and then adding the multiplication results, the calibration method comprising: a correlation detection unit obtaining, for the digital calibration signals received by the plurality of element antennas, a cross-correlation value for each receiving system for the digital calibration signals of the plurality of receiving systems with respect to a digital calibration signal in a reference receiving system that is one of the plurality of receiving systems; a step in which an inter-element system error calculation unit obtains a corrected autocorrelation value by subtracting a noise correlation value for the reference receiving system from the autocorrelation value for the digital calibration signal in the reference receiving system; a step in which the inter-element system error calculation unit calculates a relative difference for each cross-correlation value for each of the receiving systems using the corrected autocorrelation value as a reference to obtain an inter-element system error for each receiving system, and obtains a correction coefficient due to the obtained inter-element system error; and a step in which an excitation coefficient correction unit generates the corrected excitation coefficient based on the correction coefficient for each receiving system and a preset excitation coefficient.

12. A calibration program for a receiving array antenna device that causes a computer to execute the following steps: for digital calibration signals received by a plurality of element antennas, obtaining cross-correlation values for each receiving system for digital calibration signals of the plurality of receiving systems against digital calibration signals in a reference receiving system, which is one of a plurality of receiving systems corresponding to each of the plurality of element antennas; obtaining a corrected autocorrelation value by subtracting a noise correlation value for the reference receiving system from the autocorrelation value for the digital calibration signal in the reference receiving system; calculating a relative difference for each cross-correlation value for each receiving system using the corrected autocorrelation value as a reference to obtain inter-element system errors for each receiving system, and obtaining correction coefficients based on the obtained inter-element system errors; and generating the corrected excitation coefficients based on the correction coefficients for each receiving system and preset excitation coefficients.

13. A recording medium storing a program for causing a computer to execute the following steps: obtaining a cross-correlation value for each receiving system for digital calibration signals of a reference receiving system, which is one of a plurality of receiving systems corresponding to each of the plurality of element antennas, for digital calibration signals received by the plurality of element antennas; obtaining a corrected autocorrelation value by subtracting a noise correlation value for the reference receiving system from the autocorrelation value for the digital calibration signal in the reference receiving system; calculating a relative difference for each cross-correlation value for each receiving system using the corrected autocorrelation value as a reference to obtain inter-element system errors for each receiving system, and obtaining correction coefficients based on the obtained inter-element system errors; and generating the corrected excitation coefficients based on the correction coefficients for each receiving system and preset excitation coefficients.

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