JP2001249057A - Method and apparatus for measuring atmospheric temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately measure a temperature with a small increase in quantity of arithmetic operations. SOLUTION: A data rate of a receiving signal after A/D converted is decreased for an electric wave reflected by an atmospheric turbulent flow or a sound wave plane. A Doppler velocity of an echo of the atmospheric turbulent flow is calculated on the basis of the receiving signal having the data rate decreased. Meanwhile, the receiving signal after A/D converted is frequency converted thereby decreasing the data rate. A Doppler velocity of an echo of the sound wave plane is calculated on the basis of the frequency converted receiving signal having the data rate decreased, and is corrected for an amount by the frequency conversion. A sound velocity in the atmosphere is calculated on the basis of the calculated Doppler velocity of the echo of the atmospheric turbulent flow and the corrected Doppler velocity of the echo of the sound wave plane. The atmospheric temperature is obtained from the sound velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a Radio A
The present invention relates to an atmospheric temperature measuring method and an apparatus for measuring the temperature of the atmospheric air by using a coustic sounding system (hereinafter referred to as RASS).

[0002]

2. Description of the Related Art An atmospheric temperature measuring method called RASS, which measures the temperature of the atmosphere by using both a Doppler radar for atmospheric observation and sound waves, has been conventionally known. FIG.
An atmospheric temperature measuring device (hereinafter referred to as RAS) for measuring the atmospheric temperature by a conventional atmospheric temperature measuring method (hereinafter referred to as RAS)
FIG. 2 is a block diagram illustrating an overall configuration of an S device. In the figure, an antenna 131 transmits radio waves to the atmosphere whose temperature is to be measured, and receives radio waves reflected by an atmospheric turbulence in the atmosphere or a sound wave surface that is an equal phase surface of a sound wave from the speaker 136. Is a radar transmission / reception means for transmitting / receiving a transmission radio wave and a reception radio wave, 133 is a signal processing means for processing a received signal, 134 is a data display / recording means for recording and displaying data, and 135 is a radar transmission / reception means 132 Control means 136 for controlling the generation means 137 is a speaker for transmitting a sound wave to the sky where the temperature is to be measured, and 137 is a sound wave generation means for generating a sound wave to be transmitted to the sky.

FIG. 11 is an explanatory diagram showing the principle of measuring the temperature distribution by RASS. First, a sound wave is transmitted to the sky by the speaker 136. As a result, the sound wave surface propagates over the sky at the speed of sound. When this sound wave surface is observed by a Doppler radar composed of the antenna 131, the radar transmission / reception means 132, the signal processing means 133, and the data display / recording means 134, the wave surface reflected by the sound wave surface (hereinafter referred to as a sound wave surface echo) The Doppler velocity of the sound plane can be measured.

The speed of the sound wave surface is the sum of the sound speed and the wind speed because the sound wave surface is caused to flow by the wind which is the flow of the atmosphere. In the Doppler radar, a radio wave reflected by atmospheric turbulence (hereinafter referred to as atmospheric turbulence echo) other than the sound wave surface echo is observed simultaneously with the sound wave surface echo. Since the Doppler velocity of the atmospheric turbulence echo becomes the line-of-sight component of the wind speed, the sound wave front echo and the atmospheric turbulence echo are observed with a Doppler radar, and if the sound wave surface velocity is obtained from the former and the wind velocity in the line of sight is obtained from the latter, both are obtained. The sound speed Ca [m / s] is obtained from the difference between the two.

Further, if Kd is a constant between the sound speed Ca and the temporary temperature Tv of the air above, Tv = Ca / K
Since there is a relationship represented by d, it is possible to calculate the provisional temperature Tv [K] of the air above the air. However,
Kd is a constant and takes a value of Kd = 20.047. Here, the provisional temperature Tv is defined as Tv = (1+) using the mixing ratio w (the ratio between the density of water vapor and the density of dry air) and the atmospheric temperature T [K].
0.61w) It is an amount represented by T. Usually, in the troposphere, since the difference between the atmospheric temperature T and the provisional temperature Tv is 1 K or less, an approximate value of the atmospheric temperature T can be known from the provisional temperature Tv.

As described above, in the RASS observation, the atmospheric turbulence echo and the sound wave echo are simultaneously observed. Therefore, as a conventional technique 1, the radar transmitting / receiving means 132 shown in FIG.
And RASS by the signal processing means 133 shown in FIG.
It is conceivable to achieve temperature measurement with the device.

FIG. 12 is a block diagram showing the configuration of the radar transmitting / receiving means 132 of the prior art 1, which has the same configuration as the radar transmitting / receiving means of a general radar device.
In the figure, reference numeral 301 denotes transmission / reception switching means for switching between a transmission radio wave and a reception radio wave, 302 a transmission means for generating a transmission radio wave, and 303 a reception means for receiving and processing a reception radio wave received by the antenna 131. This receiving means 303
Amplifying means 304, frequency converting means 305, phase detecting means 306, local oscillator 307, and reference signal generator 30
8.

[0008] The amplification means 304 amplifies the received signal. The frequency conversion means 305 converts the amplified received signal into an intermediate frequency. Phase detection means 30
Numeral 6 is for generating an analog complex reception signal from the reception signal converted to the intermediate frequency. Local oscillator 307
Outputs a local oscillation wave for converting a received signal into an intermediate frequency. The reference signal generator 308 generates a reference signal for performing phase detection on the received signal converted to the intermediate frequency.

Next, the operation of the radar transmitting / receiving means 132 will be described. A transmission radio wave is generated by the transmission means 302 and transmitted to the antenna 131 via the transmission / reception switching means 301. The antenna 131 emits the transmission radio wave to the atmosphere. The radio wave radiated to the atmosphere is reflected by atmospheric turbulence or a sound wave surface in the atmosphere, and the radio wave reflected by the antenna 131 is received by the radar. This received radio wave is input to the receiving means 303 via the transmission / reception switching means 301. After the receiving means 303 amplifies the received signal by the amplifying means 304, the frequency converting means 305 converts the received signal to an intermediate frequency. Further, an analog complex reception signal is generated by the phase detection means 306 and output to the signal processing means 133.

Next, the signal processing means 133 will be described. FIG. 13 is a block diagram showing the configuration of the signal processing means 133.
A / D conversion means 101 for converting an analog complex reception signal input from the receiver 03 into a digital complex reception signal.
FFT means for performing a fast Fourier transform on the D-converted complex received signal; 102, a spectrum separation means for separating the spectrum of the atmospheric turbulence echo and the spectrum of the sound wave echo on the frequency axis; First incoherent integration means for performing incoherent integration processing on the atmospheric turbulence echo after spectral separation in order to calculate the Doppler velocity; 104a a first Doppler peak detection means for calculating the Doppler velocity of the atmospheric turbulence echo ,
103b denotes second incoherent integration means for performing incoherent integration processing on the sound wave front echo after spectral separation in order to calculate the Doppler velocity of the sound wave front echo.
04b is a second Doppler peak detecting means for calculating the Doppler velocity of the sound wave echo, 108 is a sound velocity calculating means for calculating the sound velocity from the difference between the Doppler velocity of the sound wave echo and the Doppler velocity of the atmospheric turbulence echo, and 109 is the atmospheric velocity. It is a temperature calculating means for calculating the temperature.

Next, the operation of the signal processing means 133 will be described. First, the phase detection means 3 of the reception means 303
A / D converter 100 converts the analog complex reception signal input from 06 into a digital complex reception signal. The FFT means 101 performs FFT processing on the complex reception signal after the AD conversion. As a result, the spectrum of the atmospheric turbulence echo has a peak in a low frequency region, and the spectrum of the sound wave front echo has a peak in a high frequency region. Therefore, the spectrum of the atmospheric turbulence echo and the spectrum of the sound wave front echo are separated on the frequency axis by the spectrum separating means 102.

For the atmospheric turbulence echo after the spectral separation, the Doppler velocity is calculated by the first incoherent integrating means 103a and the Doppler peak detecting means 104a. On the other hand, the Doppler velocity is calculated by the second incoherent integration means 103b and the Doppler peak detection means 104b for the sound wave front echo after the spectrum separation. The sound velocity calculating means 108 calculates the sound velocity from the difference between the Doppler velocity of the sound wave echo and the Doppler velocity of the atmospheric turbulence echo, and approximates the atmospheric temperature T by the above-mentioned equation, Tv = Ca / Kd, in the temperature calculating means 109. calculate.

However, in the RASS observation, 340 m / s
Since it is necessary to measure the sound wave velocity at a high level with a high degree of accuracy, the load of signal processing increases with the increase in the number of FFT points in the prior art 1. For example, to obtain a frequency resolution higher than 0.5 m / s, 1360 or more FFT points are required. Therefore, this method has hardly been used conventionally.

Instead, conventionally, by performing phase detection using a coherent oscillator whose frequency is offset in accordance with the sound wave surface echo, the apparent Doppler frequency of the sound wave surface echo is reduced, and a high frequency with a small number of FFT points is obtained. A Doppler spectrum with high resolution is obtained. FIG. 14 and FIG. 15 show a prior art 2 as a specific method for realizing this.

FIG. 14 is a block diagram showing a configuration of the radar transmitting / receiving means 141 of the prior art 2 in place of the radar transmitting / receiving means 132 of the prior art 1. In FIG. 14, the same portions as those in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, 306b is an offset COH
Second phase detection means for performing phase detection using an O (coherent oscillator) signal, 309 is a COHO frequency offset means for offsetting the output frequency of the reference signal generator 308, and 313 is a reception means for the radar transmission / reception means 141.

The radar transmitting / receiving means 141 shown in FIG. 14 differs from the radar transmitting / receiving means 132 of the prior art 1 shown in FIG. 12 in that it has two phase detecting means. The phase detection means 306 is C as in the case of the phase detection means 306 of FIG.
Phase detection is performed using the OHO signal. On the other hand, the second phase detection means 306b performs phase detection using an offset COHO signal obtained by offsetting the frequency of the output of the reference signal generator 308 by the COHO frequency offset means 309. Thereby, as shown in FIG. 16, the Doppler velocity of the sound wave surface echo becomes apparently a small Doppler velocity.

The 2 output from the radar transmitting / receiving means 141
The analog complex reception signal after the two phase detections is subjected to signal processing by signal processing means 142 shown in FIG.

FIG. 15 is a block diagram showing the structure of the signal processing means 142. In FIG. 15, the same portions as those in FIG. 13 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 100a denotes first AD conversion means for converting an analog complex reception signal phase-detected by a COHO signal into a digital complex reception signal, and 100b denotes an offset COH signal.
Second AD conversion means for converting an analog complex reception signal phase-detected by the O signal into a digital complex reception signal;
03c is a first coherent integration means for performing coherent integration processing on the digital complex reception signal converted by the first AD conversion means 100a, and 103d is a coherent integration processing for the digital complex reception signal converted by the second AD conversion means 100b. Is a first Doppler velocity calculating means for calculating the Doppler velocity of the atmospheric turbulence echo, 112 is a second Doppler velocity calculating means for calculating the Doppler velocity of the sound wave echo, and 113 is a sound wave echo Offset correction means for correcting the offset of the Doppler velocity.

As shown in FIG. 14, in the prior art 2, two received signals are output. Therefore, the signal processing means 142
In order to simultaneously process these two received signals, the first AD converter 100a, the second AD converter 100b,
A first coherent integrating means 103c, a second coherent integrating means 103d, a first Doppler velocity calculating means 111,
The second Doppler velocity calculation means 112 is provided.

A received signal phase-detected by a COHO signal is input to the first AD converter 100a shown in FIG. 15, and the Doppler velocity of the atmospheric turbulence echo is output from the first Doppler velocity calculator 111.

On the other hand, the received signal phase-detected by the offset COHO signal is input to the second AD converter 100b, and the Doppler velocity of the sound wave echo is output from the second Doppler velocity calculator 112. However, since the frequency of the Doppler velocity of the output sound wave echo is offset, the offset of the Doppler velocity is corrected by the offset correction unit 113.

FIG. 17 shows the first Doppler speed calculating means 11.
FIG. 4 is a block diagram showing a configuration of first and second Doppler velocity calculating means 112. In the figure, 121 is FFT means, 1
22 is an incoherent integration means, and 123 is a Doppler peak detection means.

Here, the signal processing means 142 shown in FIG.
The coherent integration performed by the first coherent integration means 103c and the second coherent integration means 103d is defined as a process of integrating complex signals without changing the phase. The SN ratio is improved by the coherent integration. Further, since the data rate is reduced by the coherent integration, the number of FFT points can be reduced as compared with a case where the COHO frequency is not offset.

The coherent integration has a low-pass frequency characteristic. Due to this low-pass characteristic, in the atmospheric turbulence echo processing, a sound wave front echo component existing in a high frequency range is suppressed.
On the other hand, in the sound wave front echo processing, the atmospheric turbulence echo moves to a high frequency range due to the frequency offset, and thus the atmospheric turbulence echo component is suppressed. However, since the high-frequency suppression characteristics of coherent integration do not have a very high degree of suppression, even after coherent integration, atmospheric turbulence echoes may be mixed into the band of the FFT processing due to aliasing. Therefore, from the Doppler velocity of the atmospheric turbulence echo obtained from the data of the atmospheric turbulence echo, the Doppler frequency of the atmospheric turbulence echo mixed by aliasing is calculated, and the spectrum around it is removed.

However, when the aliasing of the atmospheric turbulence echo overlaps the sound wave surface echo on the frequency axis, it becomes impossible to remove the atmospheric turbulence echo. So, usually,
The observation parameters are set so that they do not overlap as much as possible. The frequency range in which the terrain echo and the atmospheric turbulence echo are mixed by aliasing is determined by the sampling rate of the FFT. Therefore, in order to prevent the terrain echo and the atmospheric turbulence echo from overlapping with the sound wave echo, it is necessary to appropriately adjust the sampling interval of FFT, that is, the product of the pulse repetition period and the coherent integration number.

Although the prior art 2 requires two reception channels, the RA which realizes this by one channel is used.
SS devices are also employed. Next, the related art 3 will be described. FIG. 18 is a block diagram showing a configuration of the radar transmitting / receiving means 151 of the related art 3 in place of the radar transmitting / receiving means 132 of the related art 1. In the figure, the same parts as those in FIG. 14 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, reference numeral 310 denotes a reference signal switching means, 32
Reference numeral 3 denotes a receiving unit of the radar transmitting / receiving unit 151.

In this method, the COHO signal and the offset COHO signal are alternately switched by the reference signal switching means 310 every time the atmospheric turbulence echo and the sound wave front echo are observed in order to use one reception channel. This means that the observation of the atmospheric turbulence echo and the observation of the sound front echo are alternately repeated. When observing atmospheric turbulence echo, C
The OHO signal is used, and the offset COHO signal is used when observing the sound wave echo.

FIG. 19 is a block diagram showing a configuration of a signal processing means 152 according to prior art 3 which replaces the signal processing means 142 according to prior art 2. In FIG. 19, the same portions as those in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted.
In the figure, reference numeral 115 denotes an A which converts an analog received signal input from the receiving means 323 into a digital received signal.
D conversion means 116 is a coherent integration means for performing coherent integration processing on the digital received signal, 117
Means for calculating Doppler velocity in observation of atmospheric turbulence echo and observation of sound wave front echo, 118
Is a Doppler velocity switching means for switching processing between observation of atmospheric turbulence echo and observation of sound wave front echo.

In the signal processing unit 152 as well, the processing is switched by the Doppler velocity switching unit 118 between observation of the atmospheric turbulence echo and observation of the sound wave front echo.
That is, the output of the Doppler velocity calculating means 117 is input to the sound velocity calculating means 108 when observing the atmospheric turbulence echo,
At the time of sound wave surface echo observation, the output of the Doppler velocity calculation means 117 is input to the offset correction means 113, and the Doppler velocity is input to the sound velocity calculation means 108 after the offset of the Doppler velocity is corrected by the offset correction means 113.

In the prior art 3, only one phase detector 306 of the receiver 323 and one AD converter 115 of the signal processor 152 are required. However, the observation of the atmospheric turbulence echo and the observation of the sound wave echo are performed alternately, so that there is a time lag between the two observations. This degrades the accuracy of sound velocity calculation.

As described above, the conventional RASS observation methods can be classified into the following three types. Prior art 1: No COHO offset. Simultaneous observation of sound wave front echo and atmospheric turbulence echo is possible. This prior art 1
As shown in FIGS. 12 and 13, this method simultaneously processes the atmospheric turbulence echo and the sound wave echo with a large number of FFT points. It is superior to the other two prior arts 2 and 3 except that the FFT score is increased,
Conventionally, it is hardly used because the signal processing load is large due to the large score.

Prior art 2: COHO offset. Simultaneous observation of sound wave front echo and atmospheric turbulence echo is possible. According to the prior art 2, as shown in FIG. 14, a received signal is branched into two parts, one of which is subjected to phase detection as an atmospheric turbulence echo signal, and the other is used as a sound wave front echo signal to offset the COHO frequency. And the respective I and Q signals are input to the signal processing means 142 shown in FIG. Since the processing of the sound wave front echo can be performed with a small number of FFT points, it has been conventionally used well.

In this method, it is necessary to appropriately set the PRF (pulse repetition frequency) and the coherent integration number so that the sound wave surface echo and the atmospheric turbulence echo do not overlap due to Doppler spectrum aliasing. Therefore, in the case of a radar having a low degree of freedom in setting the PRF and the coherent integration number, an appropriate observation parameter cannot be selected, and it may be difficult to separate the acoustic echo from the atmospheric turbulence echo.

Prior art 3: COHO offset. Alternate observation of sound front echo and atmospheric turbulence echo. This prior art 3 uses a radar transmitting / receiving means 51 shown in FIG.
This method collects atmospheric turbulence data and sound wave surface data by alternately repeating observation without offsetting HO and observation with offset, and performs signal processing by the signal processing means 152 shown in FIG. In this method, since a sound wave front echo and an atmospheric turbulence echo cannot be obtained at the same time, it is necessary to appropriately perform time-direction data interpolation for correcting a time difference between the two echoes. However, when the weather condition changes in a short time, there is a possibility that a deterioration in the accuracy of the data interpolation may cause a temperature measurement error.

[0035]

Since the conventional atmospheric temperature measuring method and apparatus are constructed as described above, the PRF and the atmospheric turbulence echo are not overlapped by the Doppler spectrum aliasing so that the acoustic wave front echo and the atmospheric turbulent echo do not overlap. It is necessary to set the coherent integral number appropriately. In the case of a radar having a low degree of freedom in setting the PRF and the coherent integration number, there is a problem that an appropriate observation parameter cannot be selected, and there is a possibility that it is difficult to separate a sound wave echo from an atmospheric turbulence echo.

In order to simultaneously obtain a sound wave front echo and an atmospheric turbulence echo, two reception systems are required. If observation is performed alternately on one channel, a time direction for correcting a time lag between the two echoes is required. It is necessary to appropriately perform data interpolation. However, when the weather condition changes in a short time, there has been a problem that the deterioration of the accuracy of the data interpolation may cause a temperature measurement error.

These problems can be solved by increasing the number of FFT points instead of performing coherent integration, that is, by obtaining both the atmospheric turbulence echo spectrum and the sound wave front echo spectrum by one FFT processing. To increase the score, high-performance signal processing hardware is required. In particular, when the RAS function is added to a wind profiler that has already been manufactured, a large number of FFTs can be performed due to signal processing hardware limitations.
There has been a problem that it is not easy to perform high-accuracy temperature measurement due to hardware restrictions, such as inability to perform processing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an atmospheric temperature measuring method and apparatus capable of performing accurate temperature measurement with a small increase in the amount of computation. And

[0039]

An atmospheric temperature measuring method according to the present invention reduces the data rate of a received signal after AD conversion of radio waves reflected by atmospheric turbulence or a sound wave surface, and reduces the data rate of the received signal. On the basis of the signal, the Doppler velocity of the atmospheric turbulence echo is calculated, the received signal after the AD conversion is frequency-converted, the data rate is reduced, and the data rate is reduced. Is calculated based on the Doppler velocity of the sound wave front echo, the frequency conversion is corrected for the calculated Doppler velocity of the sound wave echo, the Doppler velocity of the calculated atmospheric turbulence echo, the corrected sound wave front The sound velocity in the atmosphere is calculated based on the Doppler velocity of the echo, and the atmospheric temperature is determined from the sound velocity.

The method for measuring the atmospheric temperature according to the present invention employs the method for measuring the atmospheric turbulence or the radio wave reflected by the sound wave surface.
The data rate of the converted received signal is reduced, and the Doppler velocity of the atmospheric turbulence echo is calculated from the reduced received signal. The echo component is removed, a signal of only the sound wave front echo component is extracted, the extracted signal is down-sampled, the Doppler velocity of the sound wave front echo is determined from the down-sampled signal, and the Doppler velocity is determined with respect to the determined Doppler velocity. The velocity is looped back, and the sound velocity is calculated based on the Doppler velocity of the sound wave echo that has been looped back and the Doppler velocity of the atmospheric turbulence echo that is obtained, and the atmospheric temperature is obtained from the sound velocity. is there.

The atmospheric temperature measuring apparatus according to the present invention has an AD converter for AD converting a received signal input from a radar transmitting / receiving means.
Converting means, a first data rate lowering means for receiving the AD converted reception signal output from the A / D converting means, and lowering the data rate of the received signal, and a first data rate lowering means. First Doppler velocity calculating means for calculating the Doppler velocity of the atmospheric turbulence echo from the output data rate-reduced received signal, frequency offset means for offsetting the frequency of the AD-converted received signal, Second data rate lowering means for lowering the data rate of the received signal output from the frequency offset means and frequency offset, and a received signal output from the second data rate lowering means and having the data rate reduced. Second Doppler velocity calculating means for calculating the Doppler velocity of the sound wave echo from the sound wave, and the output from the second Doppler velocity calculating means. Offset correction means for correcting the Doppler velocity offset caused by the frequency offset processing in the frequency offset means for the Doppler velocity, and the Doppler velocity of the atmospheric turbulence echo output from the first Doppler velocity calculation means. A sound speed calculating means for calculating a sound speed by calculating a difference between Doppler velocities of the acoustic wave echoes with the offset corrected, and a temperature calculating means for calculating the temperature of the atmosphere from the sound speed output from the sound speed calculating means. It was done.

The atmospheric temperature measuring apparatus according to the present invention includes a down-sampling means for reducing the data rate by thinning out the input AD-converted signal on the time axis.
The data rate lowering means or the second data rate lowering means is provided.

An atmospheric temperature measuring apparatus according to the present invention comprises a low-pass filter means for performing a low-pass filter process on an input signal after AD conversion, and a signal output from the low-pass filter means on a time axis. The first data rate lowering means or the second data rate lowering means includes downsampling means for lowering the data rate by thinning out the above.

In the atmospheric temperature measuring apparatus according to the present invention, the first data rate lowering means or the second data rate lowering means includes coherent integrating means for performing coherent integration processing on the input AD-converted signal. It was done.

An atmospheric temperature measuring apparatus according to the present invention comprises: a window function means for applying a window function to an input signal after AD conversion; and a coherent integration means for performing coherent integration processing on a signal output from the window function means. Is provided in the first data rate lowering means or the second data rate lowering means.

The atmospheric temperature measuring apparatus according to the present invention comprises frequency offset means for offsetting the frequency of the input signal by multiplying the input signal by a complex exponential function having a phase angle proportional to time and having a magnitude of one. It is prepared for.

The atmospheric temperature measuring apparatus according to the present invention reads a complex exponential function value from a complex exponential function table having a finite number of complex exponential function values having a phase angle proportional to time and having a magnitude of 1, A configuration is provided in which the frequency of the input signal is offset by multiplying the input signal by the complex exponential function value.

The atmospheric temperature measuring apparatus according to the present invention is capable of controlling the atmospheric turbulence or the radio wave reflected by the sound wave surface.
A data rate slowing means for slowing down the data rate of the converted received signal; a first Doppler speed calculating means for calculating a Doppler speed of the atmospheric turbulence echo from the slowed received signal at the data rate; Band-pass filter means for removing the atmospheric turbulence echo component from the AD-converted received signal by a band-pass filter and passing only the sound wave front echo component; Down-sampling means;
Second Doppler velocity calculating means for obtaining a Doppler velocity of a sound wave echo from a signal output from the down-sampling means, and a Doppler velocity for performing aliasing correction of the Doppler velocity with respect to the Doppler velocity output from the second Doppler velocity calculating means Loopback correction means, sound speed calculation means for calculating a sound speed by calculating the difference between the Doppler speed of the atmospheric turbulence echo calculated by the first Doppler speed calculation means and the Doppler speed of the sound wave front echo corrected for loopback, Temperature calculating means for calculating the temperature from the sound speed.

In the atmospheric temperature measuring apparatus according to the present invention, the data rate lowering means includes first down-sampling means for reducing the data rate by thinning out the input received signal after AD conversion on the time axis. It was made.

An atmospheric temperature measuring apparatus according to the present invention comprises a low-pass filter for performing low-pass filtering on an input received signal after AD conversion, and a signal output from the low-pass filter for time conversion. The data rate lowering means includes first down-sampling means for lowering the data rate by thinning on the axis.

In the atmospheric temperature measuring apparatus according to the present invention, the data rate lowering means is provided with coherent integrating means for performing coherent integration processing on the input received signal after AD conversion.

An atmospheric temperature measuring apparatus according to the present invention comprises: a window function means for applying a window function to an input AD converted reception signal; and a coherent integration means for performing coherent integration processing on a signal output from the window function means. Are provided in the data rate slowing means.

The atmospheric temperature measuring apparatus according to the present invention performs an FFT process on an input signal, calculates a power spectrum from the output subjected to the FFT process, and performs an incoherent integration process on the calculated power spectrum. Do
A first Doppler velocity calculating means or a second Doppler velocity calculating means for calculating a Doppler velocity of the input signal from the power spectrum after the incoherent integration.

In the atmospheric temperature measuring apparatus according to the present invention, the first Doppler velocity calculating means or the second Doppler velocity calculating means includes pulse pair means for calculating Doppler velocity of input data by pulse pair processing.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 shows a temperature measuring device (hereinafter, referred to as a RASS device) for measuring the atmospheric temperature to which the atmospheric temperature measuring method (hereinafter, referred to as RASS) of the first embodiment is applied.
FIG. 2 is a block diagram showing the entire configuration of the embodiment. In the drawing, 1 is an antenna transmitting radio waves to the atmosphere whose temperature is to be measured, and an antenna for receiving radio waves reflected by turbulence or sound waves in the atmosphere, and 2 is an antenna transmitting the air whose temperature is to be measured. Radar transmitting and receiving means for transmitting and receiving radio waves and the reflected radio waves; 3 for signal processing means for processing received signals; 4 for data display / recording means for recording and displaying data; Control means for controlling the generation means 7, a speaker (sound wave transmission means) 6 for transmitting a sound wave to the sky where temperature is to be measured, and 7 a sound wave generation means for generating a sound wave signal to be transmitted to the sky.

Next, the principle of measuring the temperature distribution by the RASS apparatus will be described. First, a sound wave is transmitted to the sky by the speaker 6. As a result, the sound wave surface propagates over the sky at the speed of sound. When this sound wave surface is observed by a Doppler radar composed of the antenna 1, the radar transmitting / receiving means 2, the signal processing means 3, and the data display / recording means 4, the wave reflected by the sound wave surface (hereinafter referred to as sound wave echo) The Doppler velocity of the sound plane can be measured.

The speed of the sound wave surface is the sum of the sound speed and the wind speed since the sound wave surface is caused to flow by the wind which is the flow of the atmosphere. In the Doppler radar, a radio wave reflected by atmospheric turbulence (hereinafter referred to as atmospheric turbulence echo) other than the sound wave surface echo is observed simultaneously with the sound wave surface echo. Since the Doppler velocity of the atmospheric turbulence echo becomes the line-of-sight component of the wind speed, the sound wave front echo and the atmospheric turbulence echo are observed with a Doppler radar, and if the sound wave surface velocity is obtained from the former and the wind velocity in the line of sight is obtained from the latter, both are obtained. The sound speed Ca [m / s] is obtained from the difference between

Further, since Kd is a constant between the sound velocity Ca and the temporary temperature Tv of the atmosphere, the temporary temperature Tv [K] of the atmosphere is calculated because Tv = Ca / Kd. It becomes possible. Where Kd is a constant and Kd
d = 20.047. Here, the provisional temperature Tv is
It is an amount represented by Tv = (1 + 0.61w) T using the mixing ratio w (ratio of the density of water vapor and the density of dry air) and the atmospheric temperature T [K]. Usually, in the troposphere, since the difference between the atmospheric temperature T and the provisional temperature Tv is 1 K or less, an approximate value of the atmospheric temperature T can be known from the provisional temperature Tv.

FIG. 2 is a block diagram showing the configuration of the radar transmitting / receiving means 2 shown in FIG. 1, and has the same configuration as the radar transmitting / receiving means of a general radar device. In the figure,
11 is transmission / reception switching means for switching between a transmission radio wave transmitted to the atmosphere whose temperature is to be measured and a reception radio wave reflected by atmospheric turbulence or a sound wave surface in the atmosphere, 12 is a transmission means for generating a transmission radio wave, and 13 is a transmission means. This is a receiving unit that receives and processes a radio wave received by the antenna 1. This receiving means 13
Amplifying means 14, frequency converting means 15, phase detecting means 1
6, a local oscillator 17 and a reference signal generator 18.

The amplifying means 14 amplifies the received signal of the received radio wave. The frequency conversion means 15 converts the amplified received signal into an intermediate frequency. The phase detector 16 generates an analog complex reception signal from the reception signal converted to the intermediate frequency.
The local oscillator 17 outputs a local oscillation wave for converting the amplified received signal into an intermediate frequency.
The reference signal generator 18 generates a reference signal for performing phase detection on the received signal converted to the intermediate frequency.

Next, the operation of the radar transmitting / receiving means 2 will be described. A transmission radio wave is generated by the transmission means 12 and transmitted to the antenna 1 via the transmission / reception switching means 11. The antenna 1 emits the transmission radio wave to the atmosphere. Radio waves radiated to the atmosphere are reflected by atmospheric turbulence or sound waves in the atmosphere, and received radio waves are received by the Doppler radar via the antenna 1. This received radio wave is input to the receiving means 13 via the transmission / reception switching means 11. The receiving means 13 amplifies the received signal based on the received radio wave by the amplifying means 14, and then converts the received signal into an intermediate frequency by the frequency converting means 15. Further, an analog complex reception signal is generated by the phase detection means 16 and output to the signal processing means 3.

FIG. 3 is a block diagram showing the structure of the signal processing means 3. In the figure, reference numeral 21 denotes AD conversion means for AD-converting the analog complex reception signal received from the phase detection means 16 of the reception means 13, and reference numeral 22 denotes a digital complex reception signal after AD conversion output from the AD conversion means 21. A first data rate lowering means for lowering the data rate; a first Doppler velocity calculating means for calculating a Doppler velocity in the radar line-of-sight direction from a digital complex reception signal output from the first data rate lowering means , 24 are frequency offset means for inputting the digital complex reception signal AD-converted by the AD conversion means 21 and frequency-converting the frequency of the complex reception signal by signal processing, and 25 is a frequency offset output from the frequency offset means 24. Receiving the digital complex reception signal after the The second data rate slow means a for slowed output No. of data rates,
26 is a second Doppler velocity calculating means for calculating and outputting a Doppler velocity of a sound wave echo from the digital complex reception signal output from the second data rate lowering means 25;
27 is an offset correction unit for inputting the Doppler speed output from the second Doppler speed calculation unit 26 and correcting an offset of the Doppler speed caused by frequency offset by the frequency offset unit 24; 28 is a first Doppler speed calculation A sound velocity calculating means for calculating a sound velocity by calculating a difference between a Doppler speed of a radar line-of-sight direction wind velocity (atmospheric turbulence echo) outputted from the means 23 and a sound wave echo outputted from the second Doppler velocity calculating means 26;
Is a temperature calculating means for calculating the temperature from the sound speed output from the sound speed calculating means 28.

Next, the operation of the signal processing means 3 will be described. The AD conversion means 21 receives the analog complex reception signal output from the radar transmission / reception means 2, and the AD conversion means 21 generates and outputs a digital complex reception signal. An analog complex reception signal is input to the AD converter 21 every time the Doppler radar performs pulse transmission. Then, each time a pulse is transmitted, the AD conversion means 21 generates digital reception signals corresponding to the number of range bins. Therefore, a digital complex reception signal of each range bin is output from the AD conversion means 21 at a data rate equal to the pulse repetition frequency of the Doppler radar.

The received signal of the Doppler radar contains two signal components: an atmospheric turbulence echo having a Doppler velocity of at most about several tens m / s and a sound wave echo having a Doppler velocity close to a sound velocity of 340 m / s. ing. The pulse repetition frequency of the Doppler radar is set to be higher than the Nyquist frequency for the Doppler frequency of the acoustic wave echo.

The digital complex reception signal output from the A / D conversion means 21 is
And frequency offset means 24. The digital complex reception signal input to the first data rate lowering means 22 is used to calculate the Doppler velocity of the atmospheric turbulence echo. On the other hand, the digital complex reception signal input to the frequency offset means 24 is used for calculating the Doppler velocity of the sound wave front echo.

Next, the calculation of the Doppler velocity of the atmospheric turbulence echo will be described. As described above, the data rate of the received signal is set so that the Doppler velocity of the sound wave echo can be observed without aliasing. However, for the atmospheric turbulence echo having a lower Doppler frequency than the acoustic wave front echo, the Doppler velocity can be obtained without aliasing even at a lower data rate. Therefore, after the data rate of the complex reception signal is reduced by the first data rate lowering unit 22, the first Doppler speed calculating unit 23
To calculate the Doppler velocity by performing the FFT processing. In this case, the first Doppler velocity calculating means 23 applies FFT (Fast Fourier Tr) to the input signal.
ansform) process, further calculates a power spectrum from the output subjected to the FFT process, performs an incoherent integration process on the calculated power spectrum, and calculates a power spectrum of the input signal from the power spectrum after the incoherent integration. Calculate Doppler velocity. That is, the configuration of the first Doppler velocity calculating means 23 is as follows.
It has the same configuration as the first Doppler velocity calculating means 111 in the conventional technique shown in FIG. Since the data rate is reduced, the score of the FFT processing in the first Doppler velocity calculating means 23 can be reduced, so that the FF
The amount of calculation required for the T processing is not different from the RAS signal processing according to the prior art.

In the FFT processing, the number of FFT points can be reduced by shortening the data time length instead of lowering the data rate. However, in this case, the frequency resolution of the FFT decreases, which is not a preferable method.

Next, a method for lowering the data rate in the first data rate lowering means 22 will be described.
The simplest way to lower the data rate is to downsample the data at each distance. That is, the first data rate lowering means 22 is constituted by the down-sampling means 31 as shown in FIG.

FIG. 5 shows another embodiment of the first data rate lowering means 22. In the figure, 32 is a low-pass filter means, and 33 is a down-sampling means. The low-pass filter means 32 passes only low-frequency regions where atmospheric turbulence echoes may exist, and removes other frequency components. Thereby, the sound wave front echo component existing in the high frequency region is removed. Further, the removal of the white noise component outside the pass band improves the SN ratio. Low-pass filter means 3
2 includes a well-known FIR (Finite
Impulse Response) filter and IIR
(Infinity Impulse Responses
e) Filter processing on the time axis such as a filter may be employed.

The down-sampling means 33 reduces the data rate by thinning out the signal output from the low-pass filter means 32. Since the sound wave front echo component has already been removed by the low-pass filter means 32, even if the down-sampling process is performed, mixing of the sound wave front echo due to aliasing does not occur.

FIG. 6 shows another embodiment of the first data rate lowering means 22. In the figure, reference numeral 41 denotes a coherent integrating means. In the coherent integration means 41,
Data is coherently integrated in the time axis direction for each range bin. The coherent integration process improves the SN ratio and lowers the data rate. Since the coherent integration processing has a low-pass characteristic, similarly to the first data rate slowing means 22 using the low-pass filter means 32 shown in FIG. Since the coherent integration process has a low-pass characteristic, the implementation using the coherent integration means 41 of FIG. 6 can be regarded as one of the specific examples of the implementation using the low-pass filter means 32 of FIG. . Since the coherent integration process is a simple data integration process, there is an advantage that it is a low-pass filter realizing method with a small amount of calculation.

Further, the first data rate lowering means 22
FIG. 7 shows another example of the implementation. In the figure, 51 is a window function means, and 52 is a coherent integration means. In this embodiment, the window function means 51 is added to the configuration shown in FIG. As described above, the coherent integration means has a low-pass characteristic. Coherent integration is equivalent to convolving a rectangular window with data in the time domain. Therefore, the frequency characteristic is represented by a sinc function which is a Fourier transform of a rectangular window. Since the side lobe is relatively high in the frequency characteristic represented by the sinc function, there is a possibility that the suppression of the sound wave front echo becomes insufficient. Therefore, in the configuration of FIG. 7, by performing a window function process before the coherent integration process, the side lobe of the frequency characteristic of the coherent integration process is reduced, and the performance of suppressing sound wave front echo is enhanced.

The first Doppler velocity calculating means 23 calculates the Doppler velocity of the atmospheric turbulence echo. When the first data rate lowering means 22 is realized by the configuration shown in FIG. 4, since the data rate is reduced by the down-sampling means 31, even when the Doppler speed is calculated by the FFT processing, the FFT with a small number of FFT points is performed. Processing is possible.

When the first data rate lowering means 22 is realized by any one of the configurations shown in FIGS. 5, 6, and 7, the pulse pair method is used in place of the FFT processing to further perform the signal processing operation. The amount can be reduced.
The use of the pulse pair method is based on the premise that the signal has a single Gaussian function type spectral component. However, the first data rate slowing means 22 having the configuration of FIGS. 5, 6 and 7 includes:
This has the effect of suppressing high frequencies. Therefore, the sound wave front echo component is suppressed and only the atmospheric turbulence echo component is included, so that the pulse pair method can be used.

When this pulse pair method is used, the first Doppler velocity calculating means 23 is realized by the configuration shown in FIG. In the figure, reference numeral 61 denotes an autocorrelation calculating means (pulse pair means) for obtaining an autocorrelation coefficient with a time interval of both samples as a lag by correlating two temporally continuous received signal samples. Integrating means (pulse pair means) for integrating the autocorrelation coefficient calculated at the time, 63 is speed calculating means (pulse pair means) for calculating the Doppler velocity from the phase value of the integrated autocorrelation coefficient.

The auto-correlation calculating means 61 calculates the correlation between two temporally continuous received signal samples,
An autocorrelation coefficient is determined using the time interval between both samples as a lag. Such an autocorrelation coefficient is calculated at a plurality of times and integrated by the integration means 62. Since the phase value of the integrated autocorrelation coefficient is proportional to the Doppler speed, the speed calculation means 63
, The Doppler velocity is calculated from the phase value of the autocorrelation coefficient.

Next, the calculation of the Doppler velocity of the sound wave front echo will be described. The Doppler velocity of the sound wave front echo is obtained by the frequency offset means 24, the second data rate lowering means 25, the second Doppler velocity calculating means 26, and the offset correcting means 27.

The frequency offset means 24 offsets the frequency of the digitally-converted complex received signal subjected to AD conversion by digital signal processing. In order to offset the frequency, the frequency transition of Fourier transform may be used. The principle will be described below.

The Fourier transform of the time series signal a (t) is represented by A
(F). At this time, the movement on the frequency axis means that the original signal is multiplied by a complex sine wave having a phase proportional to the time on the time axis from the frequency transition of the Fourier transform. If f _o is the amount of the frequency offset, the frequency transition is A (f−f _o ) = F [a (t) exp (j2π
f _ot )].

Here, F represents a Fourier transform. R
If the frequency of the sound wave front echo is set to be close to 0 with respect to the data of the ASS observation, and each sample of the time series signal is complex-multiplied by exp (j2πf _o t), the processing of the signal in the time series is performed. The frequency can be shifted. As a result, since the sound wave echo moves to the low frequency region, if the sampling rate is reduced by downsampling, the frequency analysis of the sound wave echo can be performed with a small number of FFT points without lowering the frequency resolution. .

According to this method, each data sample is multiplied by a complex exponential function, so that N-point data must be subjected to N complex multiplications. On the other hand, FF
Since T requires an operation amount proportional to Nlog ₂ N, the operation amount can be reduced in this method.

Note that, in this method, the complex exponential function ex
In order to reduce the calculation amount of p (j2πf _o t), it is preferable to prepare this value in advance as a table. In this case, in order to make the number of exponential function values prepared finite, it is necessary to periodically return the exponential function value to the original value.

[0083] Here, N _e sample result data have been processed, the phase of exp (j2πf _o t) is When rotated _{Np, N p = f o N} e / (PRF) is satisfied (PR
F; pulse repetition frequency).

Therefore, it is sufficient to find f _o such that both N _p and N _e are integers in this equation. For example, PR
When F is 20 kHz, the above equation is expressed as f _o / 20 kHz = N
It is modified as _p / N _e.

[0085] Thus, for example, if _{N p = 3, N e =} 20, it is possible to 3000Hz to f _o.

In the digital complex reception signal whose frequency has been offset by the frequency offset means 24, the sound wave front echo moves to a low frequency region, and the atmospheric turbulence echo moves to a high frequency region. For the digital complex reception signal, the second data rate lowering means 25 and the second Doppler velocity calculating means 26 calculate the Doppler velocity of the sound wave front echo.

The operation of the second data rate lowering means 25 and the second Doppler velocity calculating means 26 is the same as the atmospheric turbulence echo processing by the first data rate lowering means 22 and the first Doppler velocity calculating means 23. However, the Doppler speed output from the second Doppler speed calculating means 26 is the Doppler speed in a state where the frequency offset has been performed by the frequency offset means 24. Therefore, the Doppler velocity corresponding to the offset frequency is compensated by the offset correction means 27.

An example of realizing the configuration of the second data rate lowering means 25 is the same as the example of realizing the first data rate lowering means 22 shown in FIG. 4, FIG. 5, FIG. 6, and FIG. , The same components as those of the first data rate lowering means 22. Further, the second Doppler velocity calculating means 26 in the case of using the pulse pair method is realized by the configuration of FIG.

The second Doppler velocity calculating means 26 calculates the Doppler velocity of the sound wave front echo. When the second data rate lowering means 25 is realized by the configuration of FIG.
Downsampling means 31 of data rate reducing means 25
Has reduced the data rate by FFT
Even when the Doppler velocity is calculated by processing, FFT processing with a small number of FFT points is possible.

When the second data rate lowering means 25 is realized by any one of the configurations shown in FIGS. 5, 6, and 7, the pulse processing method is used in place of the FFT processing to further perform the signal processing operation. The amount can be reduced.
The use of the pulse-pair method presupposes that the signal has a single Gaussian-type spectral component, but FIGS. 5, 6 and 7
The second data rate lowering means 25 having the configuration described above has an effect of suppressing high frequencies. Therefore, the atmospheric turbulence echo component frequency-converted to a high frequency by the frequency offset unit 24 is suppressed, and only the sound wave front echo component is included, so that the pulse pair method can be used.

The Doppler velocity of the atmospheric turbulence echo output from the first Doppler velocity calculating means 23 and the Doppler velocity of the sound wave echo output from the offset correcting means 27 are input to the sound velocity calculating means 28. In the sound speed calculation means 28,
For each distance, the sound velocity is calculated by subtracting the Doppler velocity of the atmospheric turbulence echo from the Doppler velocity of the acoustic echo. The calculated sound speed at each distance is input to the temperature calculating means 29, and the following equation described in the prior art, Tv = Ca / Kd
, The temperature at each distance is obtained, and the atmospheric temperature T is approximately calculated. The calculated atmospheric temperature T is output to the data display / recording means 4.

As described above, according to the first embodiment, in the calculation of the Doppler velocity of the acoustic wave front echo, since the terrain echo and the atmospheric turbulence echo are suppressed by using the low-pass filter, the aliasing is performed. There is an effect that an atmospheric temperature measuring method and a RASS device that do not deteriorate the accuracy of Doppler velocity calculation due to superposition of an atmospheric turbulence echo or a terrain echo on a sound wave echo are obtained.

In the prior art, it is necessary to limit the PRF and the coherent integral number in order to avoid the atmospheric turbulence echo and the terrain echo from being superimposed on the sound wave echo. Since there is no need to provide any restrictions, there is an effect that an atmospheric temperature measurement method and a RASS device in which the parameters of the observation parameters can be freely set are obtained.

Also, since the atmospheric turbulence echo and the acoustic wave front echo can be simultaneously observed by one radar receiver, it is compared with the prior art 3 in which the atmospheric turbulence echo and the acoustic wave echo are observed alternately by one radar receiver. Therefore, an error in atmospheric temperature measurement due to a difference in observation time between the atmospheric turbulence echo and the acoustic wave echo does not occur, so that the temperature measurement accuracy is improved. Also, compared to the conventional technique of simultaneously observing the atmospheric turbulence echo and the acoustic wave echo using two radar receivers, only one radar receiver is required, so that the atmospheric temperature can be reduced and the cost of the apparatus can be reduced. There is an effect that a measuring method and a RASS device can be obtained.

Further, without performing coherent integration, F
Compared to the method of processing using only FT, the number of signal processing operations is reduced by reducing the number of FFT points, so that the RASS function described in the first embodiment can be easily added to a conventional RASS device. Becomes

Embodiment 2 In the first embodiment, the Doppler velocity calculation with a small number of FFT points is performed by lowering the frequency of the sound wave front echo by performing frequency offset by signal processing. In the second embodiment, in the processing of the sound wave echo in the signal processing means, the atmospheric turbulence echo is suppressed by filtering before the data rate is reduced, so that the Doppler of the sound wave echo can be obtained without performing the frequency offset. The speed can be calculated.

FIG. 9 shows the configuration of the signal processing means of the RASS apparatus according to the second embodiment. In FIG. 9, the same portions as those in FIGS. 3 and 5 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, 9 is a signal processing means of the second embodiment, 73 is a band-pass filter means for suppressing a frequency component other than a frequency range where a sound wave echo can exist, and 74 is a data for an output of the band-pass filter means 73. Down-sampling means (second down-sampling means) for lowering the rate, and 75 is Doppler velocity loopback correction means for correcting the Doppler velocity that has undergone frequency loopback.

Note that the low-pass filter means 32 and the down-sampling means (first down-sampling means) 33 of the second embodiment shown in FIG. 9 correspond to the first data rate low speed shown in FIG. 3 of the first embodiment. Data rate lowering means corresponding to the data rate lowering means 22 or the data rate lowering means 25. The data rate lowering means corresponds to the configuration of the embodiment described in the first embodiment with reference to FIGS. It is possible to apply.

Next, the operation will be described. The part of the signal processing means 9 according to the second embodiment that is different from the operation of the signal processing means 3 according to the first embodiment is a means for determining the Doppler velocity of the sound wave front echo, that is, the band-pass filter means 73, This is the part of the means 74, the second Doppler velocity calculating means 26, and the Doppler velocity return correcting means 75, and the other parts in FIG. 9 perform the same operations as in FIG.

The band-pass filter 73 suppresses frequency components outside the frequency range where sound wave front echoes can exist. Bandpass filters are generally well known FIR
Filter processing on a time axis such as a filter or an IIR filter may be employed. The data rate of the signal output from the band-pass filter unit 73 is reduced by being decimated by the down-sampling unit 74. As a result, the sound wave echo returns to a state where the Doppler velocity is turned back.
Since the atmospheric turbulence echo and the terrain echo are suppressed by the band-pass filter processing, the aliased sound wave front echo does not overlap with other echo components.

The second Doppler velocity calculating means 26 calculates the Doppler velocity of the sound wave front echo. Since the data rate is reduced by the downsampling means 74 in the preceding stage, even when the Doppler velocity is calculated by the FFT processing, the FFT processing with a small number of FFT points is possible. In order to further reduce the amount of signal processing operation, FF
A pulse pair method may be used instead of the T processing. The use of the pulse-pair method presupposes that the signal has a single Gaussian function type spectral component.
3, the signal includes only the sound wave front echo component, so that the pulse pair method can be used.

The Doppler speed calculated by the second Doppler speed calculating means 26 is equal to the Doppler speed of the preceding stage.
Signal is undergoing aliasing. The number of times the frequency is folded back by aliasing is determined by the maximum Doppler velocity that can be calculated without the occurrence of the folding by the FFT processing or the pulse pair processing, and the band-pass filter unit 73.
From the passband frequency of The maximum Doppler velocity can be obtained from the data rate input to the FFT processing or the pulse pair processing. However,
In order for the number of times of frequency folding to be uniquely determined, the bandwidth B of the band-pass filter means 73 needs to be equal to or less than the data rate after down-sampling.

As described above, according to the second embodiment, the low-pass filter means 32 and the band-pass filter means 73 accurately separate the simultaneously received atmospheric turbulence echo and sound wave echo. Therefore, the Doppler velocity of each echo can be accurately calculated. Also,
There is no time lag between atmospheric turbulence echo and sound front echo. For these reasons, it is possible to measure the temperature with higher accuracy than the conventional RASS device. In addition, since a small number of FFT processing or pulse pair processing is used for Doppler velocity calculation,
There is an effect that an atmospheric temperature measuring method and a RASS device in which the increase in the amount of calculation is small compared to the conventional technology can be obtained.

[0104]

As described above, according to the present invention, AD turbulence or radio waves reflected by a sound wave surface are controlled.
While lowering the data rate of the converted received signal and calculating the Doppler velocity of the atmospheric turbulence echo based on the reduced received data rate, the received signal after the AD conversion is frequency-converted, Slowing down the rate, calculating the Doppler velocity of the sound wave echo based on the frequency-converted received signal whose data rate has been reduced, and correcting the frequency conversion for the Doppler velocity of the sound wave echo. The sound velocity in the atmosphere is calculated based on the Doppler velocity of the calculated atmospheric turbulence echo and the Doppler velocity of the corrected sound wave front echo, and the atmospheric temperature is obtained from the sound velocity. Can simultaneously observe the Doppler velocity of the atmospheric turbulence echo and the Doppler velocity of the acoustic wave front echo, which has the effect of suppressing an increase in cost. In addition, since the observation of the atmospheric turbulence echo and the sound wave echo can be simultaneously performed without time lag, there is an effect that the error of the temperature measurement can be reduced. Further, since signal processing can be performed with a small number of FFT points, there is an effect that the scale of hardware for performing signal processing can be reduced.

According to the present invention, the data rate of the received signal after AD conversion of the radio wave reflected by the atmospheric turbulence or the sound wave surface is reduced, and the Doppler velocity of the atmospheric turbulence echo is calculated from the reduced received signal. While calculating
From the received signal after the AD conversion, the atmospheric turbulence echo component is removed by a band-pass filter to extract a signal of only a sound wave front echo component, the extracted signal is down-sampled, and a sound wave is extracted from the down-sampled signal. Determine the Doppler velocity of the surface echo, perform the Doppler velocity loopback correction on the determined Doppler velocity, calculate the sound velocity based on the Doppler velocity of the obtained atmospheric turbulence echo and the Doppler velocity of the sound wave echo. Since the atmospheric temperature is determined from the sound velocity, the Doppler velocity of the atmospheric turbulence echo and the Doppler velocity of the acoustic wave front echo can be simultaneously observed on one receiving channel, and thus the cost can be reduced. Also,
Since the atmospheric turbulence echo and the sound wave front echo are simultaneously observed without time lag, there is an effect that errors in temperature measurement can be reduced. Further, since signal processing can be performed with a small number of FFT points, there is an effect that the hardware scale for signal processing can be reduced. In addition, the use of the band-pass filter improves the accuracy of separating the atmospheric turbulence echo and the acoustic wave front echo, so that there is an effect that the temperature measurement accuracy is high.

According to the present invention, A / D conversion means for A / D converting a received signal input from the radar transmission / reception means,
A first data rate lowering means for receiving a received signal after the A / D conversion output from the D converting means and lowering a data rate of the received signal, and a data rate output from the first data rate lowering means; First Doppler velocity calculating means for calculating the Doppler velocity of the atmospheric turbulence echo from the received signal having a reduced speed, frequency offset means for offsetting the frequency of the AD-converted received signal, and output from the frequency offset means. Second data rate lowering means for lowering the data rate of the received signal whose frequency is offset, and a sound wave plane based on the received data signal having the lower data rate output from the second data rate lowering means. Second Doppler velocity calculating means for calculating the Doppler velocity of the echo, and Doppler output from the second Doppler velocity calculating means Offset correction means for correcting the Doppler velocity offset caused by the frequency offset processing in the frequency offset means, based on the Doppler velocity of the atmospheric turbulence echo and the corrected Doppler velocity of the sound wave echo. Since the apparatus is provided with a configuration for calculating the speed of sound and calculating the temperature of the atmosphere, the Doppler velocity of the atmospheric turbulence echo and the Doppler velocity of the sound wave front echo can be simultaneously observed on one reception channel, thereby suppressing an increase in cost. effective. In addition, since the observation of the atmospheric turbulence echo and the sound wave echo can be simultaneously performed without time lag, there is an effect that the error of the temperature measurement can be reduced. Further, since signal processing can be performed with a small number of FFT points, there is an effect that the scale of hardware for performing signal processing can be reduced.

According to the present invention, the downsampling means for lowering the data rate by thinning out the input signal after AD conversion on the time axis is provided by the first data rate lowering means or the second data rate lowering means. Since the data rate of the signal can be reduced by down-sampling by the down-sampling means and the Doppler velocity can be calculated with a small number of FFT points, the hardware scale for signal processing is reduced. This has the effect of being small.

According to the present invention, low-pass filter means for performing low-pass filter processing on an input signal after AD conversion, and thinning out a signal output from the low-pass filter means on a time axis The first data rate lowering means or the second data rate lowering means is provided with downsampling means for lowering the data rate by means of the above. Therefore, the S / N ratio of the received signal is improved by the low-pass filter processing. In addition, since the atmospheric turbulence echo and the sound wave surface echo do not overlap each other due to the Doppler velocity return, it is possible to calculate the Doppler velocity with high accuracy, and there is an effect that the temperature measurement precision is improved.

According to the present invention, the first data rate lowering means or the second data rate lowering means comprises coherent integrating means for performing coherent integration processing on the input signal after AD conversion. Since the low-pass filter processing is realized by the coherent integration processing, there is an effect that the temperature measurement accuracy can be improved with a smaller amount of calculation.

According to the present invention, the window function means for applying a window function to the input signal after AD conversion, and the coherent integration means for performing coherent integration processing on the signal output from the window function means, include the first data. Since the data rate reduction means or the second data rate reduction means is configured to be provided, by applying a window function before the coherent integration processing, there is an effect that the accuracy of suppressing high frequency components is improved and the accuracy of temperature measurement can be improved. .

According to the present invention, a frequency offset means for offsetting the frequency of an input signal by multiplying the input signal by a complex exponential function having a phase angle proportional to time and having a magnitude of 1 is provided. Therefore, by utilizing the frequency transition of the Fourier transform, a frequency offset can be realized by the signal processing, and the temperature measurement accuracy can be improved with a small amount of calculation.

According to the present invention, a complex exponential function value is read from a complex exponential function table having a finite number of complex exponential function values having a phase angle proportional to time and having a magnitude of 1, and Since a configuration is provided in which the frequency of the input signal is offset by multiplying the input signal by the value, a complex exponential function value used for the frequency offset is calculated in advance, so that the effect of further reducing the amount of calculation can be obtained. is there.

According to the present invention, the data rate lowering means for lowering the data rate of the received signal after the AD conversion for the radio wave reflected by the atmospheric turbulence or the sound wave surface, and the data output from the data rate lowering means. First Doppler velocity calculating means for calculating a Doppler velocity of an atmospheric turbulence echo from the received signal having a reduced data rate,
Band-pass filter means for removing the atmospheric turbulence echo component from the AD-converted received signal by a band-pass filter and passing only the sound wave front echo component; and a second sampler for down-sampling the signal output from the band-pass filter means. 2 down-sampling means, second Doppler velocity calculating means for obtaining a Doppler velocity from a signal output from the second down-sampling means, and folding back of the Doppler velocity with respect to the Doppler velocity output from the second Doppler velocity calculating means Doppler velocity aliasing correction means for performing correction, and a configuration for calculating a sound velocity based on the calculated Doppler velocity of the atmospheric turbulence echo and the Doppler velocity of the acoustic wave echo echoed back, and calculating the atmospheric temperature from the sound velocity. So that 1
Since the Doppler velocity of the atmospheric turbulence echo and the Doppler velocity of the acoustic wave front echo can be simultaneously observed on one reception channel, the cost can be reduced. In addition, since the atmospheric turbulence echo and the sound wave echo are simultaneously observed without time lag, there is an effect that errors in temperature measurement can be reduced. Further, since signal processing can be performed with a small number of FFT points, there is an effect that the hardware scale for signal processing can be reduced. In addition, the use of the band-pass filter improves the accuracy of separating the atmospheric turbulence echo and the acoustic wave front echo, so that there is an effect that the temperature measurement accuracy is high.

According to the present invention, the data rate reducing means is provided with the first down-sampling means for reducing the data rate by thinning out the input AD-converted received signal on the time axis. In addition, since the Doppler velocity can be calculated with a small number of FFT points due to the reduction in the data rate, the hardware scale for signal processing can be reduced.

According to the present invention, low-pass filter means for performing low-pass filter processing on the input received signal after AD conversion, and thinning out the signal output from the low-pass filter means on the time axis. Therefore, the data rate slowing means is provided with the first downsampling means for slowing down the data rate. In addition to improving the S / N ratio of the received signal by the low-pass filter processing, Since the atmospheric turbulence echo and the sound wave echo are not superimposed by the Doppler velocity return, it is possible to calculate the Doppler velocity with high accuracy, and there is an effect that the temperature measurement precision can be improved.

According to the present invention, since the data rate lowering means is provided with the coherent integration means for performing coherent integration processing on the input AD-converted received signal, the low-pass filter is provided by the coherent integration processing. Since the processing is realized, there is an effect that the temperature measurement accuracy can be improved with a smaller amount of calculation.

According to the present invention, the window function means for applying a window function to the input received signal after AD conversion, and the coherent integration means for performing coherent integration processing on the signal output from the window function means, have a data rate Since the low-speed means is configured to be provided, to apply a window function before the coherent integration processing, the suppression accuracy of high-frequency components is improved,
This has the effect of improving the temperature measurement accuracy.

According to the present invention, the FF is added to the input signal.
T is performed, a power spectrum is calculated from the output subjected to the FFT processing, an incoherent integration process is performed on the calculated power spectrum, and the Doppler of the input signal is calculated from the power spectrum after the incoherent integration. Since the apparatus is provided with the first Doppler velocity calculating means or the second Doppler velocity calculating means for calculating the velocity, the Doppler velocity is calculated with a small number of FFT points.
The increase in the amount of signal processing calculation is small, the atmospheric turbulence echo and the acoustic wave front echo can be simultaneously observed without time lag, and there is an effect that the temperature measurement accuracy is high.

According to the present invention, since the first Doppler velocity calculating means or the second Doppler velocity calculating means is provided with the pulse pair means for calculating the Doppler velocity of the input data by the pulse pair processing, the Doppler velocity is calculated by the pulse pair method. Since the calculation is performed, there is an effect that the amount of calculation can be further reduced as compared with the case where FFT is used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an atmospheric temperature measuring device to which an atmospheric temperature measuring method according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a radar transmitting / receiving means of the atmospheric temperature measuring device according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a signal processing unit in the atmospheric temperature measuring device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing an implementation example of a first data rate lowering unit of the signal processing unit in the atmospheric temperature measuring device according to the first embodiment of the present invention.

FIG. 5 is a block diagram showing an implementation example of a first data rate lowering unit of the signal processing unit in the atmospheric temperature measuring device according to the first embodiment of the present invention.

FIG. 6 is a block diagram illustrating an implementation example of a first data rate lowering unit of the signal processing unit in the atmospheric temperature measuring device according to the first embodiment of the present invention;

FIG. 7 is a block diagram illustrating an implementation example of a first data rate lowering unit of the signal processing unit in the atmospheric temperature measuring device according to the first embodiment of the present invention;

FIG. 8 is a block diagram illustrating a configuration example of a first Doppler velocity calculating unit and a second Doppler velocity calculating unit when the pulse pair method is used in the signal processing of the atmospheric temperature measuring device according to the first embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a signal processing unit in an atmospheric temperature measuring device to which the atmospheric temperature measuring method according to Embodiment 2 of the present invention is applied.

FIG. 10 is a block diagram showing the entire configuration of a conventional atmospheric temperature measuring device.

FIG. 11 is an explanatory diagram showing a principle of measuring a temperature distribution by an atmospheric temperature measuring method.

FIG. 12 is a block diagram showing a configuration of a radar transmitting / receiving means of the atmospheric temperature measuring device of the related art 1.

FIG. 13 is a block diagram illustrating a configuration of a signal processing unit of the atmospheric temperature measuring device according to the related art 1.

FIG. 14 is a block diagram showing a configuration of a radar transmitting / receiving means of the atmospheric temperature measuring device of the related art 2.

FIG. 15 is a block diagram illustrating a configuration of a signal processing unit of the atmospheric temperature measuring device according to the related art 2.

FIG. 16 is an explanatory diagram showing an operational characteristic of a radar transmission / reception means of the atmospheric temperature measurement device of the related art 2 with respect to a reception signal.

FIG. 17 is a block diagram showing a configuration of a first Doppler speed calculating unit and a second Doppler speed calculating unit of the atmospheric temperature measuring device of the related art 2.

FIG. 18 is a block diagram showing a configuration of a radar transmitting / receiving means of the atmospheric temperature measuring device of Prior Art 3;

FIG. 19 is a block diagram illustrating a configuration of a signal processing unit of an atmospheric temperature measuring device according to Conventional Technique 3.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 antenna, 2 radar transmitting / receiving means, 3 and 9 signal processing means, 6 loudspeaker (sound wave transmitting means), 7 sound wave generating means, 21 AD converting means, 22 first data rate lowering means, 23 first Doppler velocity calculating means, 24 frequency offset means, 25 second data rate lowering means, 26 second Doppler velocity calculating means, 27 offset correction means, 28 sound velocity calculating means, 29 temperature calculating means, 31 down sampling means, 32 low-pass filter means (data Rate downsampling means), 33 downsampling means (first downsampling means, data rate slowing down means), 41, 52 coherent integration means, 51
Window function means, 61 autocorrelation calculating means (pulse pair means), 62 integrating means (pulse pair means), 63 speed calculating means (pulse pair means), 73 band-pass filter means, 74 downsampling means (second downsampling means), 75 Doppler velocity aliasing correction means.

Claims (16)

[Claims] 1. A sound wave and a transmission radio wave are transmitted in the air, an atmospheric turbulence or a radio wave reflected by the sound wave surface is received, a Doppler velocity of a sound wave surface echo and an atmospheric turbulence echo is observed, and a sound velocity in the atmosphere is measured. An air temperature measuring method for measuring the atmospheric temperature, wherein the first data rate lowering step lowers the data rate of the received signal after AD conversion of the reflected radio wave; A first Doppler velocity calculating step of calculating a Doppler velocity of an atmospheric turbulence echo based on the reduced reception signal; a frequency offset step of frequency-converting the AD-converted reception signal; A second data rate lowering step of lowering the data rate of the received signal frequency-converted in the second data rate; A second Doppler velocity calculating step of calculating a Doppler velocity of a sound wave front echo based on the frequency-converted received signal whose data rate has been lowered in the step-down speed step, and a second Doppler velocity calculating step. A frequency offset correction step of correcting the frequency conversion by the frequency offset step with respect to the Doppler velocity of the sound wave front echo, a Doppler velocity of the atmospheric turbulence echo calculated in the first Doppler velocity calculation step, and the second Doppler. A sound speed calculation step of calculating a sound speed in the atmosphere based on the Doppler speed of the sound wave front echo calculated in the speed calculation step and corrected in the frequency offset correction step, and a sound speed calculated in the sound speed calculation step. And a temperature calculating step of calculating the temperature in the atmosphere, A method for measuring atmospheric temperature, characterized in that: 2. Transmitting sound waves and transmission radio waves into the air, receiving atmospheric turbulence or radio waves reflected by the sound wave surface, observing Doppler velocities of sound wave surface echoes and atmospheric turbulence echoes, and measuring sound velocities in the atmosphere. In the atmospheric temperature measuring method for measuring the atmospheric temperature, a data rate lowering step for lowering the data rate of the received signal after the AD conversion of the reflected radio wave is performed, and the data rate is reduced in the data rate lowering step. A first Doppler velocity calculating step of calculating a Doppler velocity of an atmospheric turbulence echo from the received signal which has been reduced in speed; and a sound wave obtained by removing an atmospheric turbulent echo component from the AD-converted received signal by a band-pass filter. A sound wave front echo component extracting step of extracting a signal of only the surface echo component, and a signal extracted in the sound wave front echo component extracting step. A second downsampling step for sampling, a second Doppler velocity calculating step for obtaining a Doppler velocity from the signal downsampled in the second downsampling step, and a Doppler velocity for the Doppler velocity obtained in the second Doppler velocity calculating step. A Doppler velocity correction step of performing a velocity return correction, and a sound velocity calculation step of calculating a sound velocity based on the Doppler velocity obtained in the first Doppler velocity calculation step and the Doppler velocity corrected in the Doppler velocity correction step. A temperature calculating step of calculating a temperature from the sound speed output from the sound speed calculating step. 3. A sound wave transmitting means for transmitting sound waves in the air,
An antenna that transmits a transmission radio wave into the air and receives radio waves reflected by the atmospheric turbulence or the sound wave surface, and generates and transmits the transmission radio wave to the antenna, and receives and receives a reception radio wave from the antenna. An atmospheric temperature measuring device comprising: a radar transmitting / receiving unit that generates a signal; and a signal processing unit that receives the received signal generated by the radar transmitting / receiving unit and calculates an atmospheric temperature. A / D conversion means for performing A / D conversion on a reception signal input from the means, and a first signal for inputting the A / D converted reception signal output from the A / D conversion means and reducing the data rate of the reception signal.
Data rate reducing means; first Doppler velocity calculating means for calculating a Doppler velocity of atmospheric turbulence echo from the received data rate reduced signal output from the first data rate reducing means; A frequency offset means for inputting a reception signal after the AD conversion by the conversion means and offsetting a frequency of the reception signal after the AD conversion, and reducing a data rate of the frequency-offset reception signal output from the frequency offset means to a low speed Second
Data rate lowering means; second Doppler velocity calculating means for obtaining a Doppler velocity of a sound wave front echo from the data rate reduced reception signal output from the second data rate lowering means; Offset correction means for correcting the Doppler velocity offset generated by the frequency offset processing in the frequency offset means with respect to the Doppler velocity output from the velocity calculation means, and atmospheric turbulence output from the first Doppler velocity calculation means A sound velocity calculating means for calculating a sound velocity by calculating a difference between the Doppler velocity of the echo and the Doppler velocity of the sound wave front echo corrected by the offset correcting means; and calculating the temperature of the atmosphere from the sound velocity outputted from the sound velocity calculating means. An atmospheric temperature measuring device, comprising: a temperature calculating unit. 4. The first data rate lowering means or the second data rate lowering means.
4. The atmospheric temperature measuring device according to claim 3, wherein the data rate lowering means includes down sampling means for lowering the data rate by thinning out the input signal after AD conversion on a time axis. . 5. The first data rate lowering means or the second data rate lowering means.
The data rate reducing means includes a low-pass filter means for performing low-pass filtering on the input signal after AD conversion, and a data output by thinning the signal output from the low-pass filter means on a time axis. 4. The atmospheric temperature measuring device according to claim 3, further comprising down sampling means for lowering a rate. 6. The first data rate lowering means or the second data rate lowering means.
4. The atmospheric temperature measuring apparatus according to claim 3, wherein the data rate lowering means includes coherent integration means for performing coherent integration processing on the input signal after AD conversion. 7. The first data rate lowering means or the second data rate lowering means.
The data rate slowing means includes: a window function means for applying a window function to an input signal after AD conversion; and a coherent integration means for performing coherent integration processing on a signal output from the window function means. The atmospheric temperature measuring device according to claim 3, wherein: 8. The frequency offset means offsets the frequency of the input signal by multiplying the input signal by a complex exponential function having a phase angle proportional to time and having a magnitude of one. 3. The atmospheric temperature measuring device according to 3. 9. The frequency offset means has a complex exponential function table having a phase angle proportional to time and storing only a finite number of complex exponential function values having a magnitude of one. 9. The atmospheric temperature measuring apparatus according to claim 8, wherein a complex exponential function value is read from the input signal, and the complex exponential function value is multiplied by the input signal to offset the frequency of the input signal. 10. A sound wave transmitting means for transmitting a sound wave in the air, an antenna for transmitting a transmission radio wave in the air and receiving an air turbulence or a radio wave reflected by the sound wave surface, and generating the transmission radio wave to generate the transmission radio wave. A radar transmitting / receiving means for outputting to the antenna and receiving radio waves from the antenna to generate a reception signal, and a signal processing means for inputting the reception signal generated by the radar transmitting / receiving means and calculating an atmospheric temperature. In the atmospheric temperature measuring device, the signal processing unit is configured to input an A / D conversion unit for performing an A / D conversion on the input reception signal, and to input the reception signal after the A / D conversion output from the A / D conversion unit and reduce a data rate thereof. Calculating a Doppler velocity of an atmospheric turbulence echo from a data-rate-reduced reception signal output from the data rate-lowering means; A first Doppler velocity calculating unit, a band-pass filter unit that receives a received signal after AD conversion by the AD converting unit, removes an atmospheric turbulence echo component by a band-pass filter, and passes only a sound wave front echo component, Second downsampling means for downsampling a signal output from the band-pass filter means, second Doppler velocity calculating means for obtaining a Doppler velocity from the signal downsampled by the second downsampling means, and the second Doppler velocity Doppler velocity return correction means for performing Doppler velocity return correction on the Doppler velocity output from the calculation means, Doppler velocity output from the first Doppler velocity calculation means, and Doppler output from the Doppler velocity return correction means A sound speed calculating means for calculating a sound speed by calculating a speed difference; An atmospheric temperature measuring device comprising: a temperature calculating unit that calculates a temperature from a sound speed output from the speed calculating unit. 11. The data rate lowering means includes first down-sampling means for reducing the data rate by thinning out the input AD-converted received signal on a time axis. Item 11. The atmospheric temperature measuring device according to Item 10. 12. The data rate lowering means includes: low-pass filter means for performing low-pass filter processing on the input AD-converted received signal; and a signal output from the low-pass filter means on a time axis. 12. The atmospheric temperature measuring apparatus according to claim 10, further comprising: a first down-sampling means for lowering a data rate by thinning the data. 13. The atmospheric temperature measuring apparatus according to claim 10, wherein the data rate lowering means includes a coherent integration means for performing a coherent integration process on the input received signal after AD conversion. 14. A data rate reducing means, comprising: a window function means for applying a window function to an input received signal after AD conversion; a coherent integration means for performing coherent integration processing on a signal output from the window function means; The atmospheric temperature measuring device according to claim 10, further comprising: 15. The first Doppler velocity calculating means or the second Doppler velocity calculating means.
The Doppler velocity calculating means performs FFT processing on the input signal, calculates a power spectrum from the output subjected to the FFT processing, performs incoherent integration processing on the calculated power spectrum, and performs The atmospheric temperature measuring apparatus according to any one of claims 3 to 14, wherein a Doppler velocity of the input signal is calculated from a power spectrum of the atmospheric temperature. 16. The first Doppler velocity calculating means or the second Doppler velocity calculating means.
15. The Doppler velocity calculating means includes pulse pair means for calculating Doppler velocity of input data by pulse pair processing.
The atmospheric temperature measuring device according to any one of claims 1 to 4.