JP2648957B2 - Level calibration method for propagation delay time measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field of the Present Invention> The present invention receives a signal spread-modulated with a pseudo-noise signal (hereinafter referred to as a PN signal), and converts the received wave into a PN signal on a transmitting side. The present invention relates to a level calibration method for a propagation delay time measuring device for measuring a propagation delay time of a received wave by performing correlation detection with a signal spread and modulated with a PN signal having the same code sequence as the signal.

<Prior Art> A measurement system as shown in FIG. 6 has been conventionally used to accurately measure a propagation delay time of a radio wave, for example, a delay time of a reflected wave with respect to a direct wave.

In this figure, reference numeral 1 denotes a transmitter that outputs a radio wave spread and modulated by a PN signal, and 2 outputs a PN signal synchronized with a clock signal of a frequency f1 output from a signal generator 3.
PN signal generator 4, frequency output from signal generator 3
A modulator that spreads and modulates the carrier signal of f2 with the PN signal and outputs the result from the antenna 5.

Reference numeral 10 denotes a reflected wave arriving at the antenna 11 through a propagation path different from the direct wave due to the direct wave from the transmitting side and reflection due to correlation detection of the received wave by receiving the radio wave from the transmitter 1 by the antenna 11. Is a propagation delay time measuring device for measuring the delay time of the signal.

12 is a phase shifter that divides the received wave into signal components having phases different from each other by 90 degrees and outputs the signals, and 13 and 14 output signals from the phase shifter 12,
The correlation detector 15 performs correlation detection on the signal spread and modulated with the PN signal transmitted from the modulator 18. The correlation detector 15 calculates the root mean square of the detection output from the correlation detectors 13 and 14 and is input to the transporter 12. This is an arithmetic unit for synthesizing a signal corresponding to the signal strength.

A PN signal generator 16 outputs a PN signal synchronized with a clock signal having a frequency f1−Δf output from the signal generator 17. The PN signal generator has a PN signal having the same code sequence (for example, a 511-bit sequence) as the PN signal on the transmission side. Output a signal.

Reference numeral 18 denotes a modulator that spreads and modulates the carrier signal of the frequency f2 output from the signal generator 17 with a PN signal.

Accordingly, the relative phase between the PN signal on the transmitting side and the PN signal on the receiving side is shifted at a speed corresponding to the difference Δf between the clock frequencies, so that the direct wave and the PN signal within one frame (511 bits) of the PN code can be obtained. The phase of the PN signal of the reflected wave
When the phase of the PN signal coincides with the time difference T, as shown in FIG. 7, the correlation outputs A and B changing in a triangular wave form are output from the computing unit 15.

By observing this output with an oscilloscope or the like, the time difference T between the correlation output A of the direct wave and the correlation output B of the reflected wave can be obtained. From this time difference T, the propagation delay time of the reflected wave with respect to the direct wave can be calculated and measured.

<Problems to be Solved by the Invention> However, in such an apparatus for measuring the delay time of a received wave, the measurement can be performed as long as the relative magnitude of the correlation output can be determined. There is no awareness of accurately determining the level itself, and a reliable level measurement cannot be performed.

In the present invention, the correlation output of the propagation delay time measuring device is maximized when the code phase of the PN signal of the wave to be measured matches the PN signal from the PN signal generator 16, and at this time, Focusing on the fact that the correlation output is proportional to the strength of the signal input to the phase shifter 12, a level that allows the input level of the measurement target wave in the propagation delay time measuring device to be accurately obtained. It is intended to provide a calibration method.

<Means for Solving the Problems> In order to solve the above problems, a level calibration method for a propagation delay time measuring device according to the present invention includes the steps of: receiving a measurement target wave spread-modulated with a pseudo noise signal of a predetermined code sequence; Propagation delay time measuring device for measuring a propagation delay time by performing correlation detection on the measurement target wave with a correlation signal spread-modulated with a pseudo noise signal of the same code sequence whose code phase changes with respect to the pseudo noise signal A level calibration method for enabling an input level of a measurement target wave to be obtained, wherein the modulation level is modulated by a pseudo noise signal whose code phase matches a pseudo noise signal modulating the correlation signal; and Inputting a calibration signal of a known level having a predetermined frequency difference with respect to the correlation signal to the propagation delay time measuring device, and varying the level of the calibration signal to Detecting a correlation detection output for each level or a combined output thereof; and, based on each level of the calibration signal, and a correlation detection output or a combined output detected for each level, a propagation delay time measuring device Obtaining calibration data relating the correlation detection output or the composite output of the correlation detection output with respect to the input level, and the maximum value of the correlation detection output detected by the propagation delay time measuring device receiving the measurement target wave or the composite output thereof By referring to the calibration data, the input level of the wave to be measured can be obtained.

<Operation> As described above, the calibration signal of the known level which is modulated by the pseudo noise signal having the same code phase as the pseudo noise signal modulating the correlation signal and has a predetermined frequency difference from the correlation signal is propagated. By inputting to the delay time measuring device, the correlation detection output of the propagation delay time measuring device is in a state of having a constant amplitude at a frequency equal to the predetermined frequency difference, so that the correlation detection output for each level of the calibration signal or It is possible to obtain stable and highly accurate calibration data from the combined output, and it is possible to accurately obtain the input level of the measurement target wave by referring to the calibration data.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a transmitter 20 and a propagation delay time measuring device (hereinafter, referred to as
FIG. 2 is a block diagram showing a connection for level calibration in which a measurement device 30 is connected via an attenuator 50 and a correlation output can be observed by an oscilloscope 40.

In FIG. 1, a transmitter 20 outputs a PN signal synchronized with a clock signal of a frequency f1 from a PN signal generator 21 to a modulator 22, and spread-modulates a carrier signal of a frequency f2 (140 MHz in the event of a fall) with the PN signal. (Hereinafter referred to as PN modulation), and the PN modulated signal is converted into a local oscillation signal having a frequency f3 by the frequency converter 23, for example.
It is configured to convert the frequency to the GHz band.

The clock signal, carrier signal and local signal are output from a PLL-type signal generator 24 using a rubidium oscillator as a reference signal source, and the frequency of each signal is the precision required for highly accurate delay time measurement. have.

Measuring device that receives radio waves from transmitter 20 and performs correlation detection
A frequency converter 31 converts the input signal into an intermediate frequency signal (for example, a 140 MHz band) with a local oscillation signal having a frequency f3 in a frequency converter 31, and the intermediate frequency signals are mutually phase-shifted by a phase shifter 32.
The signal is divided into two signals I and Q that differ by 90 degrees, and the first and second correlation detectors 33 and 34 respectively perform correlation detection.

The local oscillation signal, the carrier signal and the clock signal to be described later of the measuring device 30 are output from a signal generator 35 using a rubidium oscillator as a reference signal source, similarly to the transmitter 20.

Signals obtained by PN-modulating the carrier signal output from the distributor 36 by the modulators 37 and 38 are input to the first and second correlation detectors 33 and 34. The PN-modulated signal and the signal I , Q and the correlation detection outputs i and q are input to the calculator 39 from the first and second correlation detectors 33 and 34, and the combined output e obtained by combining the correlation detection outputs i and q is displayed on the oscilloscope 40. Is done.

The computing unit 39 ^combines the correlation detection outputs i and q by the operation of e = (i ² + q ² ) ^1/2 . Here, it is generally expressed by i = Acosθ, q = Bsin (θ + φ),
In the optimal case, A ≒ B and φ ≒ 0.

The carrier signal input to the distributor 36 is configured such that the switch 42 can switch between the carrier signal of the frequency f2 from the signal generator 35 and the carrier signal of the frequency f2 ′ output from the crystal oscillation circuit 41. .

The crystal oscillation circuit 41 is for generating a carrier signal of a correlation signal used at the time of level calibration, and the accuracy of the frequency f2 'of the carrier signal is usually about 10 ^-6 .
The oscillation frequency f2 'is, for example, several tens of hours with respect to the frequency f2 (accuracy is 10 ^-11 ) using a rubidium oscillator as a reference signal source.
It has a deviation of about several hundred Hz from z.

Further, the PN signals input to the modulators 37 and 38 are different from the PN signal output from the PN signal generator 43 in synchronization with the clock signal of the frequency f1−Δf output from the signal generator 35 and the transmitter.
The switch 44 switches between the PN signal input from the switch 20 and the PN signal. This is because the PN signal is received from the transmitter 20 at the time of level calibration and the correlation is quickly and reliably obtained, and the PN signal from the internal PN signal generator 43 is output.
It is also possible to use signals.

In this embodiment, in order to calibrate the level of the measuring device 30 configured as described above using the output of the transmitter 20, the transmitter
20 output is connected to the measuring device 30 via the attenuator 50 and the switch 51, and the signal from the attenuator 50 can be switched and input to either the measuring device 30 or the wattmeter 52 by the switch 51 as a calibration signal. While connecting the PN signal from the PN signal generator 21 of the transmitter 20 to the external input side of the switch 44,
The output of the calculator 39 is measured by the oscilloscope 40.

The power meter 52 is for correctly knowing the level of the calibration signal output from the attenuator 50 when the level of the measuring device 30 is calibrated.

The level calibration of the measuring device 30 is performed by switching the switch 42 to the crystal oscillation circuit 41 side, the switch 44 to the external input side (the PN signal generator 21 side of the transmitter 20), and the switch 51 to the measuring device 30 side.

At this time, the PN signals on the transmitter 20 side and the measuring device 30 side are completely in code synchronization, but there is a difference in the frequency of the carrier signal and the signals are slightly detuned. The correlation output from the correlation detectors 33 and 34 of the second (a)
As shown in (b), a frequency f2-f2 'having a phase difference of 90 degrees
Are output at a constant amplitude.

The frequency f2-f2 'is about several tens Hz to several hundreds Hz as described above, and passes through the integration bands of the first and second correlation detectors 33 and 34 without loss.

The arithmetic unit 39 averages the square of these two signals as described above, and outputs a DC signal having a constant voltage as shown in FIG.

After measuring this output with an oscilloscope 40,
Switch 51 to the power meter 52 side and measure the absolute level of the input signal.

By performing the same measurement while changing the amount of attenuation of the attenuator 50, that is, changing the input level of the calibration signal to the measuring device 30, the calibration data representing the relationship between the input level and the correlation output as shown in FIG. 3 is obtained. can get.

The first and second correlation detectors 3 corresponding to the input level
When calibrating the correlation detection outputs 3 and 34 independently, the correlation detection outputs may be connected to the oscilloscope 40 for measurement. The oscilloscope 40 in the above description is used to measure a peak value of a level, so to speak, and any other measuring device may be used as long as it can measure the peak level.

When the propagation delay time is actually measured after obtaining the calibration data indicating the relationship between the input level of the calibration signal and the correlation output, an antenna is provided for the output of the transmitter 20 and the input of the measurement device 30. Connect and install the transmitter 20 and the measuring device 30 at both ends of the propagation path to be measured.
The switch 42 is switched to the signal generator 35 side and the switch 44 is switched to the PN signal generator 43 side to measure the propagation delay time and the like in a tuned state.

At this time, the height (maximum value) of the correlation output waveform appearing on the oscilloscope 40 is measured, and the input level of the direct wave or the reflected wave as the measurement target wave can be accurately known from the calibration data for the measured value.

<Another embodiment of the present invention> In the above embodiment, a crystal oscillation circuit is provided in the measuring device 30.
The output of the crystal oscillation circuit 41 is switched by the switch 44 at the time of level calibration to generate a signal for correlation.However, this does not limit the present invention. Alternatively, the oscillation circuit 41 may be provided separately from the measuring device 30 as an oscillator for level calibration, and the carrier signal of the measuring device 30 or the transmitter 20 may be switched to the output signal of the oscillator.

Also, the signal generator 24 of the transmitter 20 or the signal generator 35 of the measuring device 30 can output a signal having a frequency f2 ′ slightly different from the frequency f2 as a carrier signal for calibration or correlation. With this configuration, the crystal oscillation circuit 41 used in the above embodiment can be omitted.

Further, in the above embodiment, the PN modulation signal is
The signal subjected to the frequency conversion into the z band was subjected to the reverse frequency conversion on the measuring device 30 side and input to the phase shifter 32. However, this is not intended to limit the present invention and is shown in FIG. As described above, the present invention can be applied to a system for directly transmitting and receiving a PN modulated wave.

Further, in the above-described embodiment, the direct correlation detection is performed with the correlation signal obtained by performing the PN modulation on the carrier signal of the frequency f2 '. For example, as shown in FIG. , And Q are converted to intermediate frequency signals of frequency f4 by correlation multipliers 60 and 70, respectively, and the levels of the signals from the band-pass filters 61 and 71 are logarithmically compressed by logarithmic compressors 62 and 72, respectively. , 73, and LPFs (Low Pass Filters) 64, 74, in the case of a measuring device that detects with a signal of frequency f4 in a detection circuit 65, 75, a carrier signal of frequency f2 '± f4 is converted into a PN signal on the transmitter side. , And input to the correlation multipliers 60 and 70, thereby performing the same level calibration as described above.

In the above embodiment, the transmitter used as the source of the measurement target wave when measuring the propagation delay time also served as the calibration signal source. However, as shown in FIG.
53 may be a propagation delay time measuring device 60 with a level calibration function integrated with the measuring device 30 described above.

In this case, the calibration signal source 53 may receive each signal from the signal generator 35 instead of the signal generator 24 included in the transmitter 20. In this case, the PN signal generator 21 can also be used as the PN signal generator 43. In this case, the switch 44 is provided in front of the PN signal generator 21 and the PN signal generator 21 is provided.
At the time of level calibration of the clock input to 21, frequency f1,
In measuring the propagation delay time, the frequency may be switched to the frequency f1−Δf.

Further, a signal source independent of the transmitter and the measuring device may be used as the calibration signal source 53.

<Effects of the present invention> As described above, the level calibration method of the propagation delay time measuring device of the present invention provides a pseudo-noise signal whose code phase matches a pseudo-noise signal that modulates a correlation signal of the propagation delay time measuring device. By inputting a known-level calibration signal modulated with a noise signal and having a predetermined frequency with respect to the correlation signal to the propagation delay time measurement device, the correlation detection output of the propagation delay time measurement device is equal to the predetermined frequency difference. With a constant amplitude at the frequency, a correlation detection output or a combined output for each level of the calibration signal is obtained, and calibration data relating the correlation detection output or the combined output of the correlation detection output to the input level is obtained. As a result, stable and high-precision calibration data can be obtained, and by referring to this calibration data, the input level of the measurement target wave can be corrected. I can definitely find it.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a connection for level calibration according to an embodiment of the present invention, FIG. 2 is a signal diagram showing a correlation output at the time of level calibration, and FIG. 3 is a diagram showing calibration data obtained by level calibration. It is a figure showing an example. 4 and 5 are block diagrams for explaining another embodiment of the present invention. FIG. 6 is a block diagram showing a basic configuration of a propagation delay time measuring device and a transmitter, and FIG. 7 is an output waveform diagram showing a measuring operation of the configuration of FIG. 20 transmitter, 30 propagation delay time measuring device, 33 first correlation detector, 34 second correlation detector, 35 signal generator, 39 arithmetic unit, 41 … Crystal oscillation circuits, 42, 43…
... Switch, 50 ... Attenuator, 51 ... Switch, 52 ... Wattmeter.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Kozono 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Satoshi Tanaka 1-1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Telegraph and Telephone Co., Ltd. (56) References Japanese Utility Model 1988/2007

Claims (1)

(57) [Claims] 1. A correlation object receiving a measurement object wave spread-modulated with a pseudo-noise signal of a predetermined code sequence and spread-modulated with a pseudo-noise signal of the same code sequence whose code phase changes with respect to the pseudo-noise signal. In a propagation delay time measuring apparatus for measuring a propagation delay time by performing correlation detection on the measurement target wave by a signal, a level calibration method for enabling an input level of the measurement target wave to be obtained, A known-level calibration signal modulated by a pseudo-noise signal having the same code phase as the pseudo-noise signal modulating the correlation signal and having a predetermined frequency difference with respect to the correlation signal is transmitted to the propagation delay time measuring device. Inputting; varying the level of the calibration signal to detect a correlation detection output or a composite output of each level; and each level of the calibration signal; Obtaining correlation data relating the correlation detection output or the composite output of the correlation detection output with respect to the input level of the propagation delay time measuring device from the correlation detection output detected for each level or the combined output thereof, The propagation delay is configured such that the input level of the wave to be measured can be obtained by referring to the calibration data for the maximum value of the correlation detection output detected by the propagation delay time measuring device or the combined output thereof. Level calibration method for time measurement device.