Tracking system, identification method, and program

Abstract

To provide a tracking system capable of improving accuracy for directing an antenna in a direction of a satellite when modulation is performed by a modulation method for lowering a level in a certain frequency band of a modulation signal.SOLUTION: A tracking system includes: first specification means configured to, when it is determined that a demodulated signal is not valid, specify an angle error by performing correlation detection on a sum system signal and a difference system signal in a signal band before demodulation; and second specification means for specifying the angle error by performing correlation detection on the sum system signal and the difference system signal after demodulation when it is determined that the demodulated signal is valid.SELECTED DRAWING: Figure 5

Description

[[Technical Field]]

[0001] The present disclosure relates to a tracking system, a specifying method, and a program. [[Background Art]]

[0002] Communication is actively conducted in various fields. Directional antennas may be used in some cases for communication. Patent Document 1 discloses a technology related to a tracking receiver as a related technology. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2014-115226 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] By the way, in a tracking system, a modulated signal is generally used to cause an antenna to track the direction of a satellite. For a modulated signal modulated by a modulation method that reduces the level in a certain frequency range of the modulated signal such as frequency spreading, the SN (Signal-Noise) ratio decreases. As a result, in a tracking system, when a modulated signal generated by a modulation method that reduces the level in a certain frequency range of the modulated signal is used to cause the antenna to track the direction of a satellite, the decrease in the SN ratio may reduce the accuracy of directing the antenna toward the direction of the satellite.

[0005] Figure 8 shows an example of the relationship between the signal levels and angular error of the sum and difference signals. Angular error is the angular error included when the antenna tracks the satellite, and the angle at which the antenna is directly facing the satellite is represented as error 0. In Figure 8, the vertical axis represents the signal level, and the horizontal axis represents the angle. The downward direction of the difference signal's convex peak represents the angle at which the antenna and satellite are directly facing each other, and the angle at which the angular error is 0. Figure 8 shows two signals: one with an S / N ratio of G101 and another with an S / N ratio of G102. The signal with an S / N ratio of G101 has a higher signal level relative to noise than the signal with an S / N ratio of G102. As shown in Figure 8, when the S / N ratio is G101, the angular error when pointed towards the satellite has a width of G201, and when the S / N ratio is G102, the angular error when pointed towards the satellite has a width of G202. Therefore, as can be seen from Figure 8, the angular error increases as the S / N ratio decreases.

[0006] Therefore, in tracking systems, when modulation is performed using a modulation method that reduces the signal-to-noise ratio of the modulated signal, there is a need for technology that can improve the accuracy of directing the antenna towards the satellite.

[0007] Each aspect of this disclosure aims to provide a tracking system, identification method, and program that can solve the above-mentioned problems. [Means for solving the problem]

[0008] To achieve the above objective, according to one aspect of this disclosure, the tracking system is: The system includes: a first identification means that, if the demodulated signal is determined to be invalid, identifies the angular error, which is the angular error included when the antenna tracks the satellite, by performing correlation detection on the sum and difference signals of the signal bandwidth before demodulation; and a second identification means that, if the demodulated signal is determined to be valid, identifies the angular error by performing correlation detection on the sum and difference signals after demodulation. .

[0009] To achieve the above objective, according to another aspect of this disclosure, the identification method is: If the demodulated signal is determined to be invalid, the method includes: identifying the angular error, which is the angular error included when the antenna tracks the satellite, by performing correlation detection on the sum and difference signals of the signal bandwidth before demodulation; and if the demodulated signal is determined to be valid, identifying the angular error by performing correlation detection on the sum and difference signals after demodulation. .

[0010] To achieve the above objective, according to another aspect of this disclosure, the program is: The computer is instructed to perform the following actions: if it determines that the demodulated signal is invalid, it will identify the angular error, which is the angular error included when the antenna tracks the satellite, by performing correlation detection on the sum and difference signals of the signal bandwidth before demodulation; and if it determines that the demodulated signal is valid, it will identify the angular error by performing correlation detection on the sum and difference signals after demodulation. . [Effects of the Invention]

[0011] According to each aspect of this disclosure, when a tracking system modulates using a modulation scheme that reduces the level of the modulated signal in a certain frequency range, i.e., reduces the signal-to-noise ratio, the accuracy of directing the antenna towards the satellite can be improved. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example of the configuration of a tracking system according to one embodiment of the present disclosure. [Figure 2] This figure shows an example of the processing flow of a tracking system according to one embodiment of the present disclosure. [Figure 3] This figure shows an example of the processing flow of a tracking system according to a second embodiment of the present disclosure. [Figure 4] This figure shows an example of the configuration of a tracking system according to the third embodiment of this disclosure. [Figure 5] This figure shows the minimum configuration of the tracking system according to the embodiment of the present disclosure. [Figure 6] This figure shows an example of the processing flow of a minimal tracking system according to the embodiments of this disclosure. [Figure 7] This is a schematic block diagram showing the configuration of a computer according to at least one embodiment. [Figure 8] This figure shows an example of the relationship between the noise / signal level ratio and angular error. [Modes for carrying out the invention]

[0013] The embodiments will be described in detail below with reference to the drawings. <First Embodiment> (Configuration of the tracking system) A tracking system 1 according to the first embodiment of this disclosure will be described with reference to the drawings. The tracking system 1 is a system that, when it is determined that the demodulated signal is not valid, identifies the angular error by performing correlation detection on the sum signal and difference signal of the signal band before demodulation (i.e., the frequency band of the modulated signal), and directs the antenna towards the satellite based on the identified angular error. Furthermore, if the tracking system 1 is determined that the demodulated signal is valid, it is a system that identifies the angular error by performing correlation detection on the sum signal and difference signal after demodulation, and directs the antenna towards the satellite based on the identified angular error. Examples of angular errors include those expressed as EL ERR (elevation angle error) and AZ ERR (azimuth angle error) as described later, as well as those expressed as ER ERR (elevation angle error) and CR-EL ERR (error in the direction perpendicular to the elevation angle). The modulated signal received by the tracking system 1 is a signal modulated using a modulation method that reduces the signal-to-noise ratio.

[0014] Figure 1 shows an example of the configuration of a tracking system 1 according to a first embodiment of the present disclosure. As shown in Figure 1, the tracking system 1 includes an antenna 100a, low-noise amplifiers (labeled as LNAs in Figure 1) 110, 111, frequency converters (labeled as D / Cs in Figure 1) 112, 113, a tracking receiver 200, a reference signal generation unit 300, and an antenna control unit (labeled as ACUs in Figure 1) 400. The antenna 100a includes an antenna reflector 100 and a feed unit 101.

[0015] The antenna reflector 100 and the feeding unit 101 receive a signal transmitted from a tracking target such as a satellite. The antenna reflector 100 is one or more reflectors having a curved surface, such as a parabolic antenna, a Cassegrain antenna, a Gregorian antenna, and a ring focus antenna. The antenna reflector 100 converges the received signal at a focal position. The feeding unit 101 is arranged at the focal position. The feeding unit 101 includes a higher-order mode coupler or the like that separates the received signal into a sum signal and a difference signal. Note that the feeding unit 101 may be configured using a known technique. The feeding unit 101 separates the received signal into the sum signal and the difference signal, and outputs the respective separated signals to low-noise amplifiers 110 and 111, respectively.

[0016] The low-noise amplifiers 110 and 111 amplify the signals received from the feeding unit 101 while suppressing noise to a low level. Frequency converters 112 and 113 convert the received high-frequency signals into low-frequency signals. The frequency converters 112 and 113 output the converted signals to a tracking receiver 200.

[0017] A tracking reception device 200 is a device that receives a signal output from a frequency conversion device 112 which is a difference signal and a signal output from a frequency conversion device 113 which is a sum signal, and outputs an angle error from a LAN_I / F 260, which will be described later, to an antenna control device 400. As shown in Fig. 1, the tracking reception device 200 comprises analog-to-digital converters (denoted as A / D (Analog to Digital Converter) in Fig. 1) 210, 211, band-pass filters (denoted as BPF (Band Pass Filter) in Fig. 1) 230, 231, low-pass filters (denoted as LPF (Low Pass Filter) in Fig. 1) 232, 233, integrators (denoted as Σ in Fig. 1) 234, 235, automatic gain controls (denoted as AGC (Auto Gain Control)) 240, 241, 242, 243, demodulators (denoted as DEM (Demodulator) in Fig. 1) 244, 245, correlation detection units (denoted as Cross Correlation in Fig. 1) 250, 251, an error calculation unit 252 (an example of a first specifying means, an example of a second specifying means, an example of a third specifying means, and an example of a determining means), a LAN_I / F (denoted as LAN I / F (Local Area Network Interface) in Fig. 1) 260, and multipliers 270, 271, 272, 273.

[0018] The analog-to-digital converter 210 samples the analog signal received from the frequency conversion device 112 at a fixed period. Then, the analog-to-digital converter 210 converts the sampled signal into digital data. The analog-to-digital converter 210 outputs the converted digital data to the multiplier 270 and the multiplier 272.

[0019] The analog-to-digital converter 211 samples the analog signal received from the frequency conversion device 113 at a fixed period. Then, the analog-to-digital converter 211 converts the sampled signal into digital data. The analog-to-digital converter 211 outputs the converted digital data to the multiplier 271 and the multiplier 273.

[0020] The multiplier 270 multiplies the real part (Ich) signal of the imaginary part (Qch) signal contained in the digital data output by the analog-to-digital converter 210 by the cosine signal generated by the reference signal generation unit 300, which will be described later. The multiplier 270 outputs the multiplication result to the bandpass filter 230 and the lowpass filter 232.

[0021] The multiplier 271 multiplies the real part (Ich) signal of the digital data output by the analog-to-digital converter 211 (of which it includes both a real part (Ich) signal and an imaginary part (Qch) signal) by the cosine signal generated by the reference signal generation unit 300. The multiplier 271 outputs the multiplication result to the bandpass filter 231 and the lowpass filter 233.

[0022] The multiplier 272 multiplies the imaginary part (Qch) signal contained in the digital data output by the analog-to-digital converter 210 by a sine signal generated by the reference signal generation unit 300 (described later). The multiplier 272 outputs the multiplication result to the bandpass filter 230 and the lowpass filter 232.

[0023] The multiplier 273 multiplies the imaginary part (Qch) signal contained in the digital data output by the analog-to-digital converter 211 by the sine signal generated by the reference signal generation unit 300. The multiplier 273 outputs the multiplication result to the bandpass filter 231 and the lowpass filter 233.

[0024] The bandpass filter 230 outputs only signals within a predetermined frequency range from the signals received by the multipliers 270 and 272 to the automatic gain control 240. The bandpass filter 231 outputs only signals within a predetermined frequency range from the signals received by the multipliers 271 and 273 to the automatic gain control 241.

[0025] The low-pass filter 232 outputs only the signals below a predetermined frequency from the signals received by the multipliers 270 and 272 to the integrator 234. The low-pass filter 233 outputs only the signals below a predetermined frequency from the signals received by the multipliers 271 and 273 to the integrator 235.

[0026] Integrator 234 integrates a fixed period of the signal received from the low-pass filter 232. Then, integrator 234 outputs the integrated result to the automatic gain control 242. Integrator 235 integrates a fixed period of the signal received from the low-pass filter 233. Then, integrator 235 outputs the integrated result to the automatic gain control 243.

[0027] The automatic gain control unit 241 generates a signal with a constant amplitude by correcting the gain according to the amplitude of the signal received from the bandpass filter 231. The automatic gain control unit 241 then outputs the generated signal with a constant amplitude to the correlation detection unit 250.

[0028] The automatic gain control 243 generates a signal with a constant amplitude by correcting the gain according to the amplitude of the signal received from the integrator 235. The automatic gain control 243 then outputs the generated signal with a constant amplitude to the demodulator 245.

[0029] Automatic gain control 240 corrects the gain with the same control amount as automatic gain control 241 and outputs the signal amplified with the corrected gain to the correlation detection unit 250. Automatic gain control 242 corrects the gain with the same control amount as automatic gain control 243 and outputs the signal amplified with the corrected gain.

[0030] Demodulator 244 demodulates the modulated signal received from automatic gain control 242. Demodulator 245 demodulates the modulated signal received from automatic gain control 243. The demodulation process performed by demodulators 244 and 245 includes a process that increases the signal level in a certain frequency range compared to the signal in the pre-demodulation signal band (i.e., the frequency band of the modulated signal). For example, if the modulated signal is generated by a spread frequency modulation scheme, the demodulation process performed by demodulators 244 and 245 includes a despreading process. Therefore, if the modulated signal is a signal modulated by a modulation scheme that spreads the signal over a wide frequency band and reduces the signal level against noise, the demodulation process performed by demodulators 244 and 245 will result in the signal level in a certain frequency band of the demodulated signal being greater than the level of the pre-demodulation signal in that frequency band. Demodulator 244 outputs the demodulated signal to the correlation detection unit 251. The demodulator 245 outputs the demodulated signal to the correlation detection unit 251. More specific examples of modulated signals include signals modulated using modulation schemes such as BPSK (Binary Phase-Shift Keying), QPSK (Quadrature Phase Shift Keying), FHSS (Frequency Hopping Spread Spectrum), and PCM-PM (Pulse Code Modulation-Phase Modulation).

[0031] The correlation detection unit 250 performs correlation detection on the difference signal received from the demodulator 244 and the sum signal received from the demodulator 245. The correlation detection unit 250 then outputs EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount of automatic gain control 240, 241 when the output of the sum signal is kept constant), and quality information (Q / D (Quality of Data)) representing the quality of the signal to the error calculation unit 252. Note that the method for calculating the angle error and the output conditions for the quality information may use well-known techniques.

[0032] The correlation detection unit 251 performs correlation detection on the difference signal received from the automatic gain control 240 and the sum signal received from the automatic gain control 241. The correlation detection unit 251 then outputs EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount of automatic gain controls 242 and 243 when the output of the sum signal is kept constant), and quality information (Q / D (Quality of Data)) representing the quality of the signal to the error calculation unit 252.

[0033] The error calculation unit 252 receives correlation detection results from the correlation detection units 250 and 251, respectively. The error calculation unit 252 then selects the angular error to be used for automatic tracking according to the two received correlation detection results. The error calculation unit 252 outputs EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount for automatic gain control 240, 241 or 242, 243 when the output of the summed signal is kept constant), and quality information (Q / D (Quality of Data)) representing the quality of the signal to the antenna control device 400 via the LAN_I / F260.

[0034] The LAN_I / F260 outputs the angular error output by the error calculation unit 252 to the antenna control device 400 via the LAN_I / F260. Note that the interface between the tracking receiver 200 and the antenna control device 400 is not limited to the LAN_I / F260, but may also be a serial interface for data transmission, a contact-based voltage transmission, or other methods.

[0035] The reference signal generation unit 300 generates a reference signal. The reference signal is generally a signal synchronized with a signal source based on a globally common signal source such as GPS. In this system, the sine and cosine signals generated from the reference signal are used. The antenna control device 400 receives the angular error from the error calculation unit 252. The antenna control device 400 controls the antenna 100a so that it points in the direction corrected according to the angular error. The transmitting device 2 transmits a transmission signal containing the desired information to the outside of the tracking system 1.

[0036] Next, the processing performed by the tracking system 1 according to the first embodiment of this disclosure will be described. Figure 2 is a diagram showing an example of the processing flow of the tracking system 1 according to the first embodiment of this disclosure. Here, the processing performed by the error calculation unit 252 of the tracking system 1 to select the angle error to be used for automatic tracking will be described.

[0037] The error calculation unit 252 determines whether the data received from the correlation detection unit 251 (i.e., EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant)) is valid based on the quality information (Q / D) of the angular error received from the correlation detection unit 251 (step S1).

[0038] If the error calculation unit 252 determines that the data received from the correlation detection unit 251 is valid (YES in step S1), it determines whether the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) received from the correlation detection unit 251 is above a threshold value (step S2).

[0039] If the error calculation unit 252 determines that the AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant) received from the correlation detection unit 251 is greater than or equal to a threshold (YES in step S2), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) from the correlation detection unit 251 to the antenna control device 400 via the LAN_I / F260 (step S3). After that, the error calculation unit 252 terminates processing. Here, the angular errors output from the correlation detection unit 251 to the antenna control device 400 via the LAN_I / F260, namely the EL ERR (elevation error) and AZ ERR (azimuth error), are generated based on a demodulated signal with a higher signal-to-noise ratio than the modulated signal. Therefore, the antenna control device 400 can orient the antenna 100a in the direction of the satellite with higher precision than the EL ERR (elevation error) and AZ ERR (azimuth error) generated based on the pre-demodulated signal transmitted in step S6, which will be described later.

[0040] Furthermore, if the error calculation unit 252 determines that the data received from the correlation detection unit 251 is invalid (NO in step S1), or if it determines that the AGC LV (control amount of automatic gain control 242, 243 when the output of the sum signal is kept constant) received from the correlation detection unit 251 is less than a threshold (NO in step S2), it determines whether the undemodulated data received from the correlation detection unit 250 (i.e., EL ERR (error in the elevation direction), AZ ERR (error in the azimuth direction), AGC LV (control amount of automatic gain control 240, 241 when the output of the sum signal is kept constant)) is valid based on the quality information (Q / D) of the angular error received from the correlation detection unit 250 (step S4).

[0041] If the error calculation unit 252 determines that the data received from the correlation detection unit 250 is valid (YES in step S4), it determines whether the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) received from the correlation detection unit 250 is above a threshold value (step S5).

[0042] If the error calculation unit 252 determines that the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) received from the correlation detection unit 250 is greater than or equal to a threshold (YES in step S5), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) from the correlation detection unit 250 to the antenna control device 400 via the LAN_I / F 260 (step S6). After that, the error calculation unit 252 terminates processing. Here, the angular errors output from the correlation detection unit 250 to the antenna control device 400 via the LAN_I / F 260, namely the EL ERR (elevation error) and AZ ERR (azimuth error), are generated based on the pre-demodulated signal, which has a lower signal-to-noise ratio than the demodulated signal. Therefore, the antenna control device 400 is less accurate in orienting the antenna 100a towards the satellite compared to using the EL ERR (elevation error) and AZ ERR (azimuth error) generated based on the demodulated signal transmitted in step S3. However, the antenna control device 400 can track the satellite over a wider angle range compared to using the EL ERR (elevation error) and AZ ERR (azimuth error) generated based on the demodulated signal transmitted in step S3.

[0043] Furthermore, if the error calculation unit 252 determines that the data received from the correlation detection unit 250 is invalid (NO in step S4), or if it determines that the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) received from the correlation detection unit 250 is less than a threshold (NO in step S5), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) as invalid data to the antenna control device 400 via the LAN_I / F260 (step S7). After that, the error calculation unit 252 terminates processing.

[0044] The tracking system 1 according to the first embodiment of this disclosure has been described above. In the tracking system 1, if the error calculation unit 252 (an example of a first identification means) determines that the demodulated signal is not valid, it identifies the angular error by performing correlation detection on the sum signal and difference signal of the signal band before demodulation. If the error calculation unit 252 (an example of a second identification means) determines that the demodulated signal is valid, it identifies the angular error by performing correlation detection on the sum signal and difference signal after demodulation. This tracking system 1 can improve the accuracy of directing the antenna toward the satellite when the modulated signal is modulated using a modulation method that reduces the level in a certain frequency range.

[0045] <Second Embodiment> (Configuration of the tracking system) Next, a tracking system 1 according to a second embodiment of the present disclosure will be described. Similar to the tracking system 1 according to the first embodiment of the present disclosure shown in Figure 1, the tracking system 1 comprises an antenna 100a, low-noise amplifiers 110, 111, frequency converters 112, 113, tracking receiver 200, reference signal generation unit 300, and antenna control device 400.

[0046] The tracking receiver 200, like the tracking receiver 200 shown in Figure 1, includes analog-to-digital converters 210, 211, bandpass filters 230, 231, lowpass filters 232, 233, integrators 234, 235, automatic gain controls 240, 241, 242, 243, demodulators 244, 245, correlation detection units 250, 251, error calculation unit 252, LAN interface 260, and multipliers 270, 271, 272, 273. The difference between the tracking system 1 according to the second embodiment of this disclosure and the tracking system 1 according to the first embodiment of this disclosure is the processing performed by the error calculation unit 252. Therefore, the processing performed by the error calculation unit 252 according to the second embodiment of this disclosure will be described here.

[0047] Figure 3 shows an example of the processing flow of the tracking system 1 according to the second embodiment of this disclosure. Here, we will explain the process by which the error calculation unit 252 of the tracking system 1 selects the angular error to be used for automatic tracking.

[0048] The error calculation unit 252 determines whether the data received from the correlation detection unit 251 (i.e., EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant)) is valid based on the quality information (Q / D) of the angular error received from the correlation detection unit 251 (step S11).

[0049] If the error calculation unit 252 determines that the data received from the correlation detection unit 251 is valid (YES in step S11), it determines whether the AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant) received from the correlation detection unit 251 is above a threshold value (step S12).

[0050] If the error calculation unit 252 determines that the AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant) received from the correlation detection unit 251 is above a threshold (YES in step S12), it determines whether the data received from the correlation detection unit 251 has been continuously determined to be valid (step S13). For example, if the error calculation unit 252 determined YES in the previous step S11 and also determined YES in the previous step S12, it determines that the data has been continuously determined to be valid. Otherwise, the error calculation unit 252 determines that the data has not been continuously determined to be valid. Note that the number of processes used for determination and the duration of the processes may be changed depending on the stability of the communication, frequency, modulation method, etc.

[0051] If the error calculation unit 252 determines that the data is valid for several consecutive steps (YES in step S13), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) from the correlation detection unit 251 to the antenna control device 400 via the LAN_I / F260 (step S14). After that, the error calculation unit 252 terminates its processing.

[0052] Furthermore, the error calculation unit 252 determines whether the data received from the correlation detection unit 251 was valid up to the immediate prior time (step S15) if it determines that the data received from the correlation detection unit 251 is invalid (NO in step S11), if it determines that the AGC LV (control amount of automatic gain control 242, 243 when the output of the summed signal is kept constant) received from the correlation detection unit 251 is less than a threshold (NO in step S12), or if it determines that it has not consecutively determined that the data received from the correlation detection unit 251 is valid (NO in step S13). The number of times or period for determining the immediate prior time varies depending on the stability of the communication, the frequency, the modulation method, etc., but is generally between several hundred milliseconds and several seconds.

[0053] If the error calculation unit 252 determines that the data received from the correlation detection unit 251 up to the immediate prior time was valid (YES in step S15), it identifies the angular error from the error changes up to the immediate prior time. For example, if the period judged to be the immediate prior time is several hundred ms, the error calculation unit 252 estimates the angular error by extrapolating using interpolation methods such as linear interpolation or higher-order interpolation, assuming that the way the angular error changes during those several hundred ms continues. The error calculation unit 252 then outputs the estimated angular error (i.e., EL ERR (error in the elevation direction) and AZ ERR (error in the azimuth direction)) from the correlation detection unit 251 to the antenna control device 400 via the LAN_I / F260 (step S16). After that, the error calculation unit 252 terminates its processing.

[0054] Furthermore, if the error calculation unit 252 determines that the data received from the correlation detection unit 251 up to that point was invalid (NO in step S15), it determines whether the undemodulated data received from the correlation detection unit 250 (i.e., EL ERR (elevation error), AZ ERR (azimuth error), AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant)) is valid based on the quality information (Q / D) of the angle error received from the correlation detection unit 250 (step S17).

[0055] If the error calculation unit 252 determines that the data received from the correlation detection unit 250 is valid (YES in step S17), it determines whether the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) received from the correlation detection unit 250 is above a threshold value (step S18).

[0056] If the error calculation unit 252 determines that the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant), received from the correlation detection unit 250, is greater than or equal to a threshold (YES in step S18), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) from the correlation detection unit 250 to the antenna control device 400 via the LAN_I / F260 (step S19). After that, the error calculation unit 252 terminates processing.

[0057] Furthermore, if the error calculation unit 252 determines that the data received from the correlation detection unit 250 is invalid (NO in step S17), or if it determines that the AGC LV (control amount of automatic gain control 240, 241 when the output of the summed signal is kept constant) is less than a threshold (NO in step S18), it outputs the EL ERR (elevation error) and AZ ERR (azimuth error) as invalid data to the antenna control device 400 via the LAN_I / F260 (step S20). After that, the error calculation unit 252 terminates processing.

[0058] The tracking system 1 according to the second embodiment of this disclosure has been described above. In the tracking system 1, the error calculation unit 252 (an example of the second identification means) determines that the demodulated signal is valid for at least one of a predetermined number of times and a predetermined period of time, and then identifies the angular error by performing correlation detection on the demodulated sum signal and difference signal. This tracking system 1 makes it possible to identify a signal that has a signal-to-noise ratio at the boundary between whether demodulation is possible or not. As a result, it is possible to avoid frequent switching between cases where the angular error is valid and cases where it is invalid, and the stability of signal tracking can be improved.

[0059] <Third Embodiment> (Configuration of the tracking system) Next, a tracking system 1 according to a third embodiment of the present disclosure will be described. Figure 4 is a diagram showing an example of the configuration of the tracking system 1 according to a third embodiment of the present disclosure. Similar to the tracking system 1 according to the first embodiment of the present disclosure shown in Figure 4, the tracking system 1 includes an antenna 100a, low-noise amplifiers 110, 111, frequency converters 112, 113, tracking receiver 200, reference signal generation unit 300, and antenna control device 400.

[0060] As shown in Figure 4, the tracking receiver 200 includes analog-to-digital converters 210, 211, bandpass filters 230, 231, lowpass filters 232, 233, integrators 234, 235, automatic gain controls 240, 241, 242, 243, demodulators 244, 245, correlation detection units 250, 251, LAN interface 260, and multipliers 270, 271, 272, 273. In other words, the tracking system 1 according to the third embodiment of this disclosure has the same configuration as the tracking system 1 according to the first embodiment of this disclosure shown in Figure 1, with the error calculation unit 252 removed.

[0061] In the third embodiment of this disclosure, both the correlation detection unit 250 and the correlation detection unit 251 output EL ERR (elevation error), AZ ERR (azimuth error), quality information (Q / D), and AGC LV (control amount of automatic gain control 240, 241, 242, 243 when the output of the summed signal is kept constant) to the antenna control device 400 via the LAN_I / F260.

[0062] The tracking system 1 according to the third embodiment of this disclosure has been described above. Both the correlation detection unit 250 and the correlation detection unit 251 output EL ERR (elevation error) and AZ ERR (azimuth error) to the antenna control device 400. As a result, the antenna control device 400 can acquire information on EL ERR (elevation error), AZ ERR (azimuth error), quality information (Q / D), and AGC LV (control amount of automatic gain control 242, 243 when the output of the sum signal is kept constant) in the demodulated signal, and EL ERR (elevation error), AZ ERR (azimuth error), quality information (Q / D), and AGC LV (control amount of automatic gain control 240, 241 when the output of the sum signal is kept constant) in the signal before demodulation, and it becomes possible to select which of the angular errors to use at antenna 100a and control the direction of the antenna.

[0063] Figure 5 shows the minimum configuration of the tracking system 1 according to an embodiment of the present disclosure. As shown in Figure 5, the tracking system 1 comprises a first identification unit 1a (an example of a first identification means) and a second identification unit 1b (an example of a second identification means). The first identification unit 1a determines that the demodulated signal is not valid, and identifies the angular error by performing correlation detection on the sum signal and difference signal of the signal band before demodulation. The second identification unit 1b determines that the demodulated signal is valid, and identifies the angular error by performing correlation detection on the sum signal and difference signal after demodulation.

[0064] Figure 6 shows an example of the processing flow of the minimal tracking system 1 according to the embodiment of this disclosure. Next, the processing of the minimal tracking system 1 according to the embodiment of this disclosure will be described with reference to Figure 6.

[0065] If the first identification unit 1a determines that the demodulated signal is not valid, it identifies the angular error by performing correlation detection on the sum signal and difference signal of the signal bandwidth before demodulation (step S101). If the second identification unit 1b determines that the demodulated signal is valid, it identifies the angular error by performing correlation detection on the sum signal and difference signal after demodulation (step S102).

[0066] The minimum configuration of the tracking system 1 according to the embodiment of this disclosure has been described above. This tracking system 1 can improve the accuracy of directing the antenna toward the satellite when modulation is performed using a modulation method that reduces the level in a certain frequency band of the modulated signal.

[0067] In addition, the order of processing in the embodiments of this disclosure may be changed, as long as appropriate processing is performed.

[0068] Although embodiments of this disclosure have been described, the tracking system 1, error calculation unit 252, antenna control device 400, and other control devices described above may have a computer system inside. The process described above is stored in program form on a recording medium readable by a computer, and the above process is performed when the computer reads and executes this program. A specific example of a computer is shown below.

[0069] Figure 7 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. As shown in Figure 7, computer 5 includes a CPU 6, main memory 7, storage 8, and interface 9.

[0070] For example, the tracking system 1, error calculation unit 252, antenna control device 400, and other control devices are each implemented in the computer 5. The operation of each of the above-mentioned processing units is stored in storage 8 in the form of a program. The CPU 6 reads the program from storage 8, loads it into main memory 7, and executes the above-mentioned processing according to the program. The CPU 6 also allocates memory areas in main memory 7 corresponding to each of the above-mentioned storage units according to the program.

[0071] Examples of storage 8 include HDDs (Hard Disk Drives), SSDs (Solid State Drives), magnetic disks, magneto-optical disks, CD-ROMs (Compact Disc Read Only Memory), DVD-ROMs (Digital Versatile Disc Read Only Memory), and semiconductor memory. Storage 8 may be an internal medium directly connected to the bus of computer 5, or an external medium connected to computer 5 via interface 9 or a communication line. Furthermore, if this program is distributed to computer 5 via a communication line, computer 5, upon receiving the program, may expand it into main memory 7 and execute the above processing. In at least one embodiment, storage 8 is a tangible storage medium that is not temporary.

[0072] Furthermore, the above program may implement some of the functions described above. Moreover, the above program may be a file that can implement the above functions in combination with a program already recorded in the computer system, a so-called differential file (differential program).

[0073] While several embodiments of this disclosure have been described, these embodiments are illustrative and do not limit the scope of the disclosure. These embodiments may be modified in various ways, without departing from the gist of the disclosure. [Explanation of symbols]

[0074] 1. Tracking System 1a...1st specific part 1b...Second specific part 5. Computers 6..CPU 7. Main Memory 8. Storage 9. Interface 100... Antenna reflector 100a... Antenna 101... Power supply unit 110, 111... Low-noise amplifiers 112, 113... Frequency converter 200... Tracking receiver 210, 211... Analog-to-digital converters 230, 231... Bandpass filters 232, 233... Low-pass filters 234, 235...integrator 240, 241, 242, 243... Automatic gain control 244, 245... Demodulator 250, 251... Correlation detection section 252...Error calculation section 260···LAN_I / F 270, 271, 272, 273... multipliers 300...Reference signal generation section 400... Antenna control device

Claims

1. If the demodulated signal is determined to be invalid, a first identification means identifies the angular error, which is the angular error included when the antenna tracks the satellite, by performing correlation detection on the sum and difference signals of the signal bandwidth before demodulation. If the demodulated signal is determined to be valid, a second identification means identifies the angular error by performing correlation detection on the demodulated sum signal and difference signal, A tracking system equipped with [a specific feature].

2. A determination means for determining whether the demodulated signal is valid based on the quality of the demodulated sum signal and difference signal. Equipped with, The first specific means is, If the determination means determines that the demodulated signal is invalid, the angular error is identified by performing correlation detection on the sum signal and difference signal of the signal bandwidth before demodulation. The second specified means is, If the determination means determines that the demodulated signal is valid, the angular error is identified by performing correlation detection on the demodulated sum signal and difference signal. The tracking system according to claim 1.

3. A third identification means for identifying the quality of the demodulated sum signal and difference signal, Equipped with, The determination means is Based on the quality of the demodulated sum signal and difference signal identified by the third identification means, it is determined whether or not the demodulated signal is valid. The tracking system according to claim 2.

4. The second specified means is, If it is determined that the demodulated signal is valid for at least one of a predetermined number of times and a predetermined period, the angular error is identified by performing correlation detection on the demodulated sum signal and difference signal. A tracking system according to any one of claims 1 to 3.

5. If the demodulated signal is determined to be invalid, correlation detection is performed on the sum and difference signals of the signal bandwidth before demodulation to identify the angular error, which is the angular error included when the antenna tracks the satellite. If the demodulated signal is determined to be valid, the angular error is identified by performing correlation detection on the demodulated sum signal and difference signal. A specific method including

6. On the computer, If the demodulated signal is determined to be invalid, correlation detection is performed on the sum and difference signals of the signal bandwidth before demodulation to identify the angular error, which is the angular error included when the antenna tracks the satellite. If the demodulated signal is determined to be valid, the angular error is identified by performing correlation detection on the demodulated sum signal and difference signal. A program that executes the command.

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