JP3412015B2 - Station error compensation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal receiving system in a wideband radio interferometer, a high-accuracy positioning system, or the like, in which delay and frequency characteristics in the station cause an error. The present invention relates to an intra-station error compensation method for compensating an error caused by a device or a signal path with high accuracy. 2. Description of the Related Art Conventionally, in a system such as an interferometer in which an intra-station frequency characteristic or the like causes an error, as shown in FIG. The method of injecting the phase calibration signal generated by the calibration signal generation means 52 has been adopted. The received signal into which the phase calibration signal has been injected by the directional coupler 53 is then
The signal is converted by the amplifier 54, the frequency converter 55, the filter 56, and the like, and the received signal and the phase calibration signal are simultaneously sampled by the sampling unit 57. [0003] Correlation processing means 59 uses the data sampled as described above and the SIN component of the phase calibration signal and the COS component of the phase calibration signal created by the SIN / COS component creation means 58 at the frequency at the time of data recording. Performs the correlation processing of the lag 1, and the phase difference detection means 60 calculates the ratio between the SIN correlation component and the COS correlation component based on the acquired correlation value, so that the phase difference of the calibration signal can be detected. The “lag 1” performed by the correlation processing unit 59 is described.
"Correlation processing" means that correlation is obtained without giving a delay between two signals to be correlated. [0004] However, the above-described intra-station error compensation method using the phase difference detection method can simply and perfectly perform phase calibration, but the signal phase to be corrected is The phase is limited to the phase within the frequency range of the calibration signal, and only point correction can be performed. For example, when a tone signal is injected as a phase calibration signal as shown in FIG. 7A, a frequency range in which phase calibration is correctly performed by the above-described conventional method is regarded as equivalent to a phase characteristic represented by the phase calibration signal. It is limited to the frequency band near the phase calibration signal. The tone signal is a signal of one frequency. Here, a method of injecting many phase calibration signals into a band without using a tone signal as a phase calibration signal (FIG. 7)
Although a method of injecting a comb signal as a phase calibration signal as in (b) is also conceivable, it is technically complicated, for example, the phase calibration signal phase must be detected while avoiding the influence of each other's phase calibration signal phase. Was not realistic. When phase correction is performed by injecting a comb signal, specifically, a correlation process as shown in FIG. 8 is performed. Detection of the phase calibration signal is performed using the phase calibration signal (SI
N and COS components) and the sampled data are correlated by one (lag number 1) correlator consisting of exclusive-OR negation (hereinafter, EXNOR) without delay, and the integrated value of each of the SIN component and COS component To get. Then, TAN ^-1 (S
(IN component / COS component) to calculate the phase difference. However, when a phase calibration signal of a certain frequency is detected,
The influence of the phase calibration signal having an odd multiple of the frequency enters, and inputting many phase calibration signals at the same time leads to an error. For example, consider the recorded phase calibration signal shown in FIG. By using the fundamental wave SIN component and the fundamental wave COS component generated to detect this and calculating the cross-correlation with the phase calibration signal,
The phase difference between the recorded phase calibration signal and the original fundamental wave is obtained. The cross-correlation is equivalent to taking EXNOR of two signals. Next, consider a case where the second and third harmonics of the phase calibration signal are mixed. As shown in FIG. 9 (b), the second harmonic signal becomes zero even if it is correlated with the fundamental wave SIN component and the fundamental wave COS component, and thus does not affect the detection of the phase calibration signal of the fundamental wave. However, the third harmonic (odd number harmonic) component is a problem. As shown in FIG. 9C, when the third harmonic is correlated with the fundamental COS component, it does not become zero in the section indicated by “*”. Similarly, third harmonic and fundamental SIN
Even when the correlation with the component is obtained, it does not become zero in the section indicated by “**”. Therefore, simultaneous input of many phase calibration signals at frequencies other than the correct even-numbered frequency leads to an error. Therefore, the present invention realizes high-resolution intra-station errors due to factors such as intra-station delay, delay variation, and frequency characteristics over the entire band of a received signal without using a tone signal or a comb signal as a phase calibration signal. It is an object of the present invention to provide an intra-station error compensation method that can be easily calibrated in time. [0010] In order to solve the above-mentioned problems, the invention according to claim 1 is a method for receiving a signal, such as a broadband radio interferometer or a high-accuracy positioning system, in which frequency characteristics in a station cause an error. In a system, an intra-station error compensating method for compensating for errors due to intra-station devices and signal paths, wherein a sideband of a PSK spread signal obtained by PSK spreading a carrier with a wideband PN signal synchronized with a reference signal is used as a phase calibration signal. The phase calibration signal is received within the station by injecting the received signal immediately below the interferometer element and performing wide lag correlation processing on the sampled data sampled after intra-station transmission and the wideband PN signal phase-synchronized with the reference signal. The delay / delay variation is specified, the intra-station frequency characteristics over the entire band of the received signal are obtained based on the delay / delay variation, and the intra-station error included in the received signal is compensated. It is characterized by doing so. Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a waist of an intra-station configuration in one element of a broadband radio interferometer. For example, a phase calibration signal used for intra-station error compensation is injected immediately below an antenna 1 as an interferometer element. The phase calibration signal is a first PN that generates a wideband PN (pseudo noise) signal that is phase-synchronized with the reference signal generated by the reference signal generation unit 2.
Signal generating means 3 and carrier generating means 4 for generating a carrier wave
A PSK (phase shift keying) spread signal spread by the PSK spreading means 5 which receives the supply of the PN signal and the carrier is generated from the PSK spread signal, and a one side band (upper band or lower band) is generated by the filter 6 from the PSK spread signal. Only one of the sideband waves) is cut out. Here, the generation process of the phase calibration signal will be described with reference to FIG. (A) is a representation of the PN signal on the time axis, which is represented on the frequency axis as shown in (b).
When the carrier signal is spread with the PN signal, a PSK spread signal as shown in FIG. This is a form used in ordinary communication or the like as a PSK spread signal. Then, in the present invention, one side band (upper band in the example of FIG. 2) of the PSK spread signal is cut out as shown in (d), and this is used as a phase calibration signal. As described above, the phase calibration signal for compensating the intra-station error used in the present invention is separated from the ordinary PSK spread signal so as not to have both sidebands of the spread signal in the reception band. Since only the upper band wave or lower band wave of the spread signal is used, there is no need to separate the orthogonal I and Q components and correlate with the code as in a normal PSK spread signal, so no despreading is performed. There is an advantage. The phase calibration signal generated as described above is injected into the received signal at the antenna 1 by the directional coupler 7, and becomes as shown in FIG. After that, the signals are appropriately converted by devices constituting the interferometer, such as the amplifier 8, the frequency conversion means 9, and the filter 10, and the reception signal and the phase calibration signal are simultaneously sampled by the sampling means 11,
Collected and recorded as sampling data. The phase calibration signal included in the sampled data is mutually reciprocated with the PN signal supplied from the second PN signal generation means 12 for generating a PN signal synchronized in phase with the reference signal generated by the reference signal generation means 2. The correlation
Correlation processing is performed by the wide lag correlation processing means 13. Frequency spectrum obtaining means 1 from the wide lag cross-correlation function (cross-correlation spectrum) of the phase calibration signal thus obtained.
The frequency spectrum of the calibration signal is obtained by 4, and this frequency spectrum is supplied to the phase spectrum obtaining means 15. Further, a calibration signal generator (first PN signal generator 3, carrier wave generator 4, PSK) which has been measured in advance.
By comparing the frequency characteristics of the spreading means 5 and the filter 6) with the frequency spectrum obtained by the frequency spectrum obtaining means 14, the intra-station frequency characteristics over the entire band of the received signal can be obtained. In other words, since the phase calibration signal is mixed with the received signal immediately below the antenna, it passes through the same path after the injection point, so the frequency characteristics obtained by the phase calibration signal are subtracted from the received signal phase. ,
It is possible to correct errors due to intra-station frequency characteristics common to the received signal and the phase calibration signal over the entire band of the received signal frequency. Therefore, frequency spectrum acquisition means 1
By using the intra-station frequency characteristics obtained by comparing the frequency spectrum of the calibration signal acquired in step 4 with the known frequency characteristics in the calibration signal generator, intra-station errors included in the reception signal sampled by the sampling unit 11 can be compensated. It is. For this reason, in the present embodiment, the frequency characteristics of the calibration signal generator, which are measured in advance, are stored in the calibration signal generator frequency characteristic storage means 16, and the calibration signal generator frequency characteristic storage means is stored. The intra-station frequency characteristic acquisition unit 17 compares the frequency characteristics supplied from the frequency spectrum 16 with the frequency spectrum supplied from the frequency spectrum acquisition unit 14 so that the intra-station frequency characteristics can be acquired. The intra-station frequency characteristic acquired by the intra-station frequency characteristic acquisition unit 17 in this way is
The internal error compensating means 18 compensates for the internal error contained in the received signal sampled by the sampling means 11. The measurement of the frequency characteristics of the calibration signal generator stored in the calibration signal generator frequency characteristic storage means 15 is performed using, for example, a reference receiver as shown in FIG. The reference receiver is a reception configuration serving as a phase and delay reference, and is configured by, for example, a frequency conversion unit 9 and a filter 10. In a normal receiving system, the antenna 1 is connected to the sampling means 11 by a long cable or the like. However, in the reference receiver, all components are connected without using a long cable or the like. Since the cable does not pass through a long cable, the amplifier 8 is not required. For this reason, the calibration signal generator is connected to the reference receiver on a desk, and the sampling unit 11, the wide lag cross-correlation unit 13, and the frequency spectrum acquisition unit 14 determine the frequency characteristics of the calibration signal generator via the reference receiver. A measurement can be made.
The measurement of the frequency characteristics of the calibration signal generator connected to another interference element (antenna) constituting the interferometer is also performed via the same reference receiver. This makes it possible to perform relative characteristic correction via the common reference receiver.
If necessary, the frequency characteristic of the reference receiver can be acquired by the network analyzer 19, and if this and the relative characteristic correction are combined, the absolute characteristic correction can be performed. When the phase spectrum is calculated from the frequency spectrum by the phase spectrum obtaining means 15 and is recorded in a time series, the change in the intra-station delay as the group delay can be known from the change. The frequency characteristic (phase information) at this time can also be obtained over the entire spread band. Here, since “phase change amount = frequency × delay amount” can be expressed, the delay change and the phase change should have a linear relationship. Therefore, it is determined that the one not in this relationship is due to the change in the frequency characteristic. it can. Here, an example of the wide lag correlation performed by the wide lag cross correlation processing means 13 will be described with reference to FIG. The wide lag correlation process is a process of passing either a PN code or a received signal through a shift register to create data with different delay amounts. In the example of FIG. 4, the received signal is passed through the shift register to be delayed. A wide lag correlation is made between the received signals having different delay amounts and the PN code having no delay by n EXNORs, and a correlation result is obtained for each correlation integral lag. Then, a broadband cross-correlation spectrum is obtained for each correlation integration lag. Next, the principle of intra-station error compensation by intra-station frequency characteristic correction will be described with reference to FIG. What is shown as a bar graph in FIG. 5A schematically shows the relationship between the received signal phase and the calibration signal phase at an arbitrary point (frequency). In the actual measurement, it is obtained as a more continuous phase component for each spread code clock width. Here, since the calibration signal is mixed with the received signal immediately below the antenna, the signal passes through the same path as the received signal after the injection point (directional coupler 7), and has exactly the same delay and phase characteristics as the received signal. Therefore, if the phase of the phase calibration signal is subtracted from the phase of the received signal, the station (for example, the amplifier 8, the frequency conversion means 9, the filter 10, etc.) from the injection point of the phase calibration signal until sampling is performed. It is possible to remove the influence of the delay, delay variation, and frequency characteristics. That is, according to the above-described intra-station error compensation method, the signal delay between the interferometer elements (antennas) which is not affected by the delay / frequency characteristics in the intra-station of the interferometer is obtained. Therefore, an intra-station error caused by a delay amount, a fluctuation amount, a frequency characteristic, and the like can be obtained over the entire spread band of the calibration signal, and a wide band of the compensation range can be realized. Moreover, each interferometer element has a different P
By mixing the N-code calibration signal at the RF frequency, there is also the advantage that the intra-station frequency characteristics can be compensated in real time simultaneously with the interferometer observation without affecting the interferometer observation that correlates between the interferometer elements. is there. The phase of the carrier and the code delay of the PN code are obtained by despreading using a normal PSK spread signal. To realize this, a DLL (Delay L) is used.
In this case, the correlation of three lags shifted by half a clock of the PN code clock has been performed by, for example,
The present invention requires a wide-lag cross-correlation process in a wide time window. Instead of calculating the phase of the carrier and the code delay of the PN code, a frequency spectrum over a wide band is obtained from the wide-lag cross-correlation function. You can do it. As described above, according to the first aspect of the present invention, one side band of a PSK spread signal obtained by PSK spreading a carrier with a wideband PN signal phase-synchronized with a reference signal is calibrated. Since the signal is injected into the received signal immediately below the interferometer element, the phase calibration signal also passes through the same path as the received signal. Can be obtained. Then, the intra-station frequency characteristic that can be obtained by the phase calibration signal can be obtained over the entire band of the received signal, so that the compensation of the frequency characteristic in a wide band can be realized. In addition, since the intra-station delay, delay variation, and frequency characteristics in an actual operation state can be measured over a wide band, when the method of the present invention is applied to an interferometer, the intra-station frequency caused by the intra-station frequency characteristics and the like can be observed simultaneously with the interferometer observation. There is also an advantage that errors can be compensated in real time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram schematically showing a configuration in which the method of the present invention is applied to an interferometer. FIG. 2 is a schematic explanatory diagram from a generation process of a calibration signal used in a method of the present invention to an injection into a received signal. FIG. 3 is a functional block diagram showing a schematic configuration for measuring a frequency characteristic of a calibration signal generator. FIG. 4 is a logic circuit diagram showing an example of a wide lag correlation processing means. FIG. 5 is an explanatory diagram illustrating the principle of compensation for intra-station frequency characteristics. FIG. 6 is a functional block diagram of a conventional interferometer having an intra-station error compensation function. FIG. 7 is a schematic explanatory diagram showing an injection state of a phase calibration signal. FIG. 8 is a logic circuit diagram showing an example of a lag 1 correlation processing means. FIG. 9A is a schematic explanatory diagram showing a correlation between a sampled phase calibration signal and a fundamental SIN component and a fundamental COS component. (B) It is a schematic explanatory view showing the correlation between the second harmonic of the phase calibration signal and the fundamental wave SIN component and fundamental wave COS component. (C) is a schematic explanatory view showing the correlation between the third harmonic of the phase calibration signal and the fundamental wave SIN component and the fundamental wave COS component. [Description of Signs] 1 Antenna 2 Reference signal generating means 3 First PN signal generating means 4 Carrier wave generating means 5 PSK spreading means 6 Filter 7 Directional coupler 8 Amplifier 9 Frequency converting means 10 Filter 11 Sampling means 12 Second PN signal generating means 13 Wide lag cross-correlation processing 14 Frequency spectrum acquisition means 15 Phase spectrum acquisition means

Claims (1)

(57) [Claims] [Claim 1] A signal receiving system such as a broadband radio interferometer and a high-accuracy positioning system in which frequency characteristics in a station cause an error, and an intra-station error caused by an intra-station device or a signal path. In the station error compensating method for compensating for the carrier, a carrier is converted to P by a wideband PN signal synchronized in phase with a reference signal.
One sideband of the SK-spread PSK spread signal is injected as a phase calibration signal into the received signal immediately below the interferometer element, and is spread between the sampled data sampled after intra-station transmission and a wideband PN signal phase-synchronized with the reference signal. By performing the lag correlation process, the delay / delay variation received in the station by the phase calibration signal is specified, and based on this, the intra-station frequency characteristics over the entire band of the received signal are obtained, and the intra-station error included in the received signal is obtained. An intra-station error compensation method characterized in that compensation is performed.