JPH02241146A - Level calibration method for propagation delay time measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a correlation output with a level corresponding to a level of an input signal continuously and to attain stable level calibration with high accuracy by calibrating the level while a code phase of a pseudo noise signal (PN signal) is coincident and a calibration input signal is received in a detuning state with a frequency difference within a range of able to take correlation. CONSTITUTION:A spread modulation wave from a calibrated transmitter 20 or the like is received in advance as an input signal for calibration and the code phase of a PN signal of a propagation delay time measuring instrument 30 is made coincident with that of a PN signal resulting from modulating the calibration input signal. Then the calibration input signal is subject to correlation detection while being detuned by frequency difference within a range from which the correlation output is able to be obtained and the level of the signal in response to the frequency difference outputted at the correlation detection is detected and the level of the input signal to be received at the propagation delay time measurement is calibrated based on the level. Thus, a correlation output with a level corresponding to the level of the input signal is obtained continuously and stable level calibration with high accuracy is implemented.

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 PN signal), and uses this received wave as a PN signal on the transmitting side. The present invention relates to a level calibration method for a propagation delay time measurement device that measures the propagation delay time of a received wave by performing correlation detection with a signal spread-modulated with a PN signal of the same code string.

<Prior art> (Figures 6 and 7) In order to accurately measure the propagation delay time of radio waves, for example, the delay time of reflected waves relative to direct waves, a measurement system as shown in Figure 6 has conventionally been used. It is used.

In the figure, 1 is a transmitter that outputs a radio wave spread-modulated with a PN signal, and 2 is a PN signal generator that outputs a PN signal synchronized with the clock signal of frequency f1 output from the signal generator 3). , 4 is a modulator that performs spread modulation on the carrier signal of frequency f2 outputted from the signal generator 3 using PN Shintan and outputs it from the antenna 5.

10 receives the radio waves from the transmitter 1 with the antenna 11,
This propagation delay measuring device measures the delay time of a reflected wave that reaches the antenna 11 through a propagation path different from that of the direct wave using a direct wave from the transmitting side and a reflected wave by performing correlation detection on the received wave.

12 is a phase shifter that divides the received wave into signal components with a phase difference of 90 degrees and outputs the divided signal components. 13.14 is a phase shifter that spreads the signal from the phase shifter 12 with PNig@ sent out from the modulator 18. A correlation detector 15 performs correlation detection using a modulated signal, and a correlation detector 15 calculates the root mean square of the detection outputs from the correlation detectors 13 and 14, and synthesizes it into a signal corresponding to the intensity of the signal input to the phase shifter 12. It is a magisterial device.

16 is the signal light and the frequency f1- output from the voltage converter 17.
PN that outputs a PN signal synchronized with the clock signal of △f
It is a signal generator and outputs a PN signal with the same code sequence (eg, 511 bit sequence) as the PN signal on the transmitting side.

A modulator 18 performs spread modulation on the carrier signal of frequency f2 output from the signal generator 17 using a PN signal.

Therefore, P N Ni on the sending side and PN on the receiving side
The relative phases of the signals will shift at a speed corresponding to the clock frequency difference ΔI' in A, and within one frame (511 bits) of the PN code, the phases of the PN signals of the direct wave and the reflected wave will be different from that of the receiving side PN. When the phase of the signal coincides with the time difference T, the deducer 15 outputs correlation signals JA and B that change in the form of triangular waves, as shown in FIG.

By observing this output with an oscilloscope, etc., it is possible to obtain the time difference T between the correlation output A of the direct wave and the correlation output B of the anti-01 wave, and from this time difference, the propagation delay time of the reflected wave with respect to the direct wave can be calculated. It can be measured.

The correlation output becomes maximum when the code phase of the PN signal of the received wave and the PN signal from the PN signal generator 16 match, and the correlation output at this time is input to the phase shifter 12. It is proportional to the signal strength.

Therefore, if the correlation output is calibrated with the absolute level of the signal input to the phase shifter 12, the input level of the received wave can be accurately determined from the correlation output along with the propagation delay time.

<Problem to be solved by the invention> However, no highly accurate level calibration method has been proposed for this type of measuring device, and the reliability of level measurement is insufficient, making it difficult to realize a highly accurate level calibration method. was desired.

・Means for Solving the Problem> In order to solve the above problem, the level calibration method of the propagation delay time measuring device of the present invention includes the following steps: Then, the code phase of the PN signal of the propagation delay time measuring device and the PN signal modulating the input signal for calibration is avoided, and the input signal for calibration is adjusted to a frequency difference within the range where the correlation output is 1q. Correlation detection is performed in a state where the signal is detuned by I am trying to calibrate it. .

<Operation> Therefore, an 8" force corresponding to the level of the calibration input/output signal is obtained as the correlation detection output, and the level calibration of the propagation delay time measuring device can be performed by changing the level of the input signal for calibration. Ru.

<Embodiments of the present invention> (Figures 1 to 3) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a transmitter 20 and a propagation delay time measuring device (hereinafter referred to as
Connect the measuring device and approximately J) 30 via an attenuator 50,
4 is a block diagram showing connections for level calibration in which correlation output is measured with an oscilloscope 40. FIG.

In FIG. 1, a transmitter 20 causes a PN signal generator 21 to output a PN signal synchronized with a clock signal of frequency f1 to a modulator 22, and spread-modulates a carrier signal 8 of frequency f2 (for example, 140 MHz) with the PN signal ( (hereinafter referred to as PN modulation), and the frequency converter 23 converts this PN modulated signal into a local oscillator signal having a frequency of 3, for example, to a GHz band.

Note that the clock signal, carrier signal, and local oscillator signal are output from a PLL type signal generator 24 that uses a rubidium oscillator as a reference source, and the frequency of each signal is determined by the frequency required for high-precision delay time measurement. It has excellent accuracy.

The measuring device 30 that receives radio waves from the transmitter ta20 and performs correlation detection converts the input signal into an intermediate frequency signal (for example, 140 MHz band) using a local oscillation signal of frequency f3 in the frequency converter 31, and converts this intermediate frequency signal into an intermediate frequency signal. The phase shifter 32 branches the signal into two signals (1) and (Q) having a phase difference of 90 degrees, and the first and second correlation detectors 33 and 34 perform correlation detection on each signal.

Note that this local oscillator signal, a carrier signal and a clock signal to be described later are outputted from a signal generator 35 which uses a rubidicoum oscillator as a reference source, similar to the signal generator 24 of the transmitter 20.

The first and second correlation detectors 33.3/I include a distributor 36.
The carrier signal outputted from the modulator 37.38 is subjected to PN modulation, and the PN modulated signal is output from the first and second correlation detectors 33.34.
The correlation output '%Q with Q is input to the arithmetic unit 39, and the arithmetic and synthesized output e is displayed on the oscilloscope/IO.

Note that the calculator 39 performs the calculation e=F〒=17. Here, generally 1=Acosθ, q=
It is expressed as Bsin (θ”−ψ), and in the optimal case A÷8
1φ is now O.

The carrier signal input to the distributor 36 is switched between the carrier signal of frequency f2 from the signal generator 35 and the carrier signal of frequency f2' (No. 3) output from the crystal oscillation circuit 41 using a switch 42. It is configured so that

Note that this crystal oscillation circuit 41 is used for calibration, and the accuracy of its frequency f2' is usually about 10 2 . This oscillation frequency f2- has a deviation of, for example, from several tens of l-1z to several hundred Hz with respect to the frequency [2 (accuracy is 10) of the -I+ rubidicoum oscillator.

The PN signals input to the modulators 37 and 38 are the PN signal generated from the PN signal generator 43 in synchronization with the clock signal of frequency f1Δf output from the signal generator 35, and the PN signal input from the transmitter 20. PN signal and switch 4
4. This is because by receiving the PN signal from the transmitter 'fm20, correlation can be established quickly and reliably, and it is also possible to operate satisfactorily using the PN signal from the internal PN signal generator 43.

In order to calibrate the level of the measuring device 30 configured in this way using the output of the transmitter 20, the output of the transmitter 20 is connected to the measuring device 30 via an attenuator 50 and a switch 51. The signal from the attenuator 50 can be switched to the measuring device 30 side and the wattmeter 52 side, and the P from the PN signal generator 21 of the transmitter 20
The N signal is connected to the external input side of the switch 4/1 so that the output of the generator 39 can be measured with an oscilloscope 40.

The power meter 52 is used to accurately determine the level of the signal output from the attenuator when performing one-novel calibration of the measuring device 30.

To calibrate the level of the measurement device @30, set the switch 42 to the crystal oscillation circuit/41 side and the switch 44 to the external input side (transmitter 20
(PN signal generator 21 side), switch 51 to measuring device 3
Switch to the 0 side.

At this time, the []N signals on the transmitting Ia 20 side and the measuring device 30 side are completely code-synchronized, but there is a difference in the frequency of the carrier signals and they are slightly detuned.
The correlation output from the second correlation detector 33, 34 is a signal having components of the frequency r2-f2- with a phase difference of 90 degrees, as shown in FIGS. 2(a) and (b). is output.

Note that the frequency of the signal having the r2-f2- component is approximately several 1001-(Z), 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 constant DC signal as shown in FIG. 2(C).

After measuring this output with an oscilloscope 40 and lc, the switch 51 is switched to the wattmeter 52 side and the absolute level of the input signal is measured.

By performing the same measurements as described above while changing the attenuation amount of the attenuator 50, that is, the input level to the measuring device 30,
Calibration data of input level versus correlation output as shown in FIG. 3 is obtained.

Also, the first and second correlation detectors 33 for the input level
．． When calibrating the 34 correlation outputs independently, each correlation output may be connected to the oscilloscope 40 and measured.

The A1-140 in the above description is used to measure the peak level, so to speak, and any other measuring device may be used as long as it measures the peak level.

Note that when actually measuring the propagation delay time, antennas are connected to the output of the transmitter 20 and the input of the measuring device 30, and the transmitter 20 and the measuring device 30 are connected to both ends of the propagation path to be measured. and connect the switch 42 of the measuring device 30 to the generator 35 side, set the switch 44 to PN.
Switch to the signal generator/13 side and measure propagation delay time, etc. in a tuned state.

At this time, by measuring the height of the correlation output waveform appearing on the oscilloscope 40 and calibrating this measured value using calibration data, it is possible to accurately know the input signal level of the direct wave or reflected wave.

Other Embodiments of the Present Invention (FIGS. 4 and 5) In the embodiment described above, a crystal oscillation circuit 41 is provided in the measuring device 30, and its output is switched by a switch 44 during level calibration. However, the present invention is not limited to this example,
For example, this oscillation circuit may be provided in the transmitter 2o to switch the carrier signal, or this crystal oscillation circuit 41 may be provided separately from the measuring device 30 as an oscillator for level calibration, and the measuring device 30 may be
0 or the carrier signal on the transmitter 20 side may be switched to the output of this oscillator.

Also, the signal generator 24 of the transmitter 20 or the measuring device 3
The Iζζ crystal oscillation circuit 41 used in the above embodiment can be omitted by configuring the signal generator 35 of 0 to output a signal with a frequency f2− that is slightly different from the frequency f2. .

Furthermore, in the above embodiment, the signal from the transmitter 20 that frequency-converts the PN modulated signal to the GHZ band and transmits the signal is subjected to reverse frequency conversion on the measuring device 30 side and input to the phase shifter 32. However, the present invention is not limited to this embodiment, and can be applied in exactly the same manner to the measuring device shown in FIG. 6 described above.

Further, in the above embodiment, the carrier signal of frequency f2' is
For example, as shown in FIG. 4, the signal 1.Q from the phase shifter 32
are converted into intermediate frequency signals of frequency f4 by correlation multipliers 60 and 70, and the levels of the signals from bandpass filters 61 and 71 are logarithmically converted by logarithmic compressors 62 and 72, respectively, and then converted to intermediate frequency signals of frequency f4 by correlation multipliers 60 and 70. Detection circuit consisting of .73, Onibi LPF (low pass filter) 64.7/I 65.7
In the case of a measuring device that detects a signal with a frequency of ``4'' in 5, the carrier signal with a frequency of f2'±``4 is spread-modulated with the PN signal on the transmitting side and inputted to the correlation multiplier 60.70. Level calibration can be performed.

Furthermore, in the embodiment described above, the configuration was such that the transmitter used to measure the propagation delay time and the calibration signal source also functioned.
As shown in FIG. 5, the calibration signal source 53 may be integrated with the measurement device 30 described above to form a propagation delay time measuring device 60 with a calibration function.

In this case, the calibration signal source 53 may be arranged to receive each signal from the signal generator 35 instead of the signal generator 24 included in the transmitter 20. Among these, the PN signal generator 43 can also serve as the PN signal generator 21.

In this case, the switch 44 is installed in front of the PN signal generator 21 to set the clock input to the PN signal generator 21 at frequencies f1-Δf (during propagation delay time measurement) and [1 (during calibration). It may be possible to switch.

Moreover, the calibration signal source 53 can also be structured as an independent calibration signal source.

<Effects of the Present Invention> As described above, the level calibration method of the present invention, with the code phases of the PN signals matched, inputs the calibration input signal to
Since the level is calibrated while receiving detuned signals with a frequency difference within the correlation range, it is possible to continuously obtain a correlation output of a magnitude corresponding to the level of the input signal, resulting in a stable and high level signal. Accurate level calibration can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing connections for level calibration in an embodiment of the present invention; FIGS. 2(a), (b), and (C) are signal diagrams showing correlation horns during level calibration; FIG. 3 is a diagram showing an example of calibration data obtained by level calibration. FIGS. 4 and 5 are block diagrams for explaining other embodiments of the present invention. FIG. 6 is a block diagram showing the basic configuration of a propagation delay time measuring device and a transmitter, and FIG. 7 is an output waveform diagram showing the measurement operation of the configuration shown in 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 circuit, 42.44 ...・・・Switch, 50・
...Attenuator, 51...Switch, 52...
...Electric power products (. Patent applicant: Anritsu Corporation Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] A correlation device that receives a spread modulated wave modulated with a pseudo noise signal of a predetermined code string, and is spread modulated with a pseudo noise signal of the same code string whose code phase changes with respect to the pseudo noise signal. A level calibration method for a propagation delay time measuring device that measures a propagation delay time by correlation detection of the spread modulated wave using a signal, the method comprising: receiving the same calibration input signal as the spread modulated wave; The code phase of the pseudo noise signal modulating the input signal and the pseudo noise signal of the propagation delay time measuring device are made to match, and the input signal for calibration is detuned by a predetermined frequency difference from the spread modulated wave. Perform correlation detection with the correlation signal, detect the level of the signal corresponding to the frequency difference output when the correlation detection is performed, and based on the level, determine the level of the spread modulated wave received when measuring the propagation delay time. A level calibration method for a propagation delay time measuring device.