JP3977131B2 - Propagation path characteristic measuring method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a propagation path characteristic measuring method and apparatus, and more particularly to a propagation path characteristic measuring method and apparatus for accurately measuring frequency characteristics and delay profiles of propagation paths for digital broadcasting and digital transmission.
[0002]
[Prior art]
In a conventional propagation path characteristic measuring apparatus, a wideband reference signal generated by a signal generator is supplied to a system to be measured and passed through the system to be measured, and a reference signal directly supplied from the signal generator Are measured simultaneously, and the frequency characteristics of the signal measured through the system under test are divided by the frequency characteristics of the reference signal from the signal generator measured simultaneously. Propagation path characteristics such as profiles are calculated. For this reason, the propagation path characteristic measuring apparatus is configured to simultaneously measure two systems of signals, that is, a reference signal and a signal that has passed through the measurement target system.
[0003]
In addition, when a signal having a known wideband training signal inserted, such as an OFDM (orthogonal frequency division multiplexing) signal, is used as a reference signal, the propagation path characteristics can be calculated simply by measuring one system signal that has passed through the system under test. There is a way to do.
[0004]
[Problems to be solved by the invention]
However, in the method of measuring propagation path characteristics using a training signal by measuring only one system signal that has passed through the system under measurement, there is no absolute reference because the reference signal is not measured, and the measured signal When only the propagation path characteristic relative to the main wave can be calculated and there is a time variation of the entire system under measurement, there is a problem that the time variation of the entire system under measurement cannot be measured.
[0005]
For this reason, in order to measure the time variation of the entire system under measurement, it is necessary to simultaneously measure two systems of the reference signal and the signal that has passed through the system under measurement. In order to measure these signals simultaneously, it is necessary to have two measuring units, and there is a problem that the circuit configuration becomes complicated and large-scale.
[0006]
The present invention has been made in view of the above points, and provides a propagation path characteristic measuring method and apparatus capable of accurately measuring the propagation path characteristic of a system to be measured only by measuring one system of signals. With the goal.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 generates and outputs a broadband reference signal,
Level-adjusting one of the signals branched from the reference signal and outputting it,
Supplying the other signal branched from the reference signal to the system under test;
Adding a signal supplied through the system to be measured and a signal supplied by adjusting the level;
The frequency characteristic measured from the addition signal, said calibrated with the measured frequency characteristic while terminating remove the system under measurement, by calculating the frequency characteristic or the delay profile of the system under measurement,
It is possible to accurately measure the propagation path characteristics of the system under measurement simply by measuring one system of signals.
[0008]
According to the second aspect of the present invention, the level adjustment of one signal branched from the reference signal is performed by adjusting the level of the signal power supplied from the system under measurement in the addition to the signal power supplied by adjusting the level. By doing it higher,
A reference signal is taken out as a main wave component, and signal processing is performed using this reference signal as a reference, whereby time fluctuations in the propagation path characteristics of the system under measurement can be measured.
[0009]
The invention according to claim 3 is a signal generator for generating and outputting a broadband reference signal;
A gain adjusting circuit that is supplied and adjusts the level of one of the signals branched from the reference signal,
An adder for adding the signal supplied from the gain adjustment circuit and the signal supplied through the system under test to which the other signal branched from the reference signal is supplied;
By having a propagation path characteristic calculation circuit that calculates the frequency characteristic or delay profile of the measured system from the signal added by the adder,
It is possible to accurately measure the propagation path characteristics of the system under measurement simply by measuring one system of signals.
[0010]
According to a fourth aspect of the present invention, the gain adjustment circuit performs gain adjustment in the adder so that the signal power supplied from the gain adjustment circuit is higher than the signal power supplied from the system under measurement. By
A reference signal is taken out as a main wave component, and signal processing is performed using this reference signal as a reference, whereby time fluctuations in the propagation path characteristics of the system under measurement can be measured.
[0011]
In the invention described in claim 5, the channel characteristic calculation circuit, the frequency characteristic of the state of connecting the system under measurement, by calibrating the frequency characteristics calculated while terminating remove the system under measurement, the By calculating the frequency characteristics or delay profile of the system under test,
It is possible to obtain the propagation path characteristic of only the system under measurement from which the distortion of the frequency characteristic of the measuring apparatus is removed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a block diagram of an embodiment of a propagation path characteristic measuring apparatus of the present invention. In the figure, a propagation path characteristic measuring apparatus 10 includes a signal generator 1, a divider 2, a gain adjustment circuit 3, an adder 4, and a propagation path characteristic calculation circuit 5, to which a system under test 6 is connected.
[0013]
The signal generator 1 generates a broadband reference signal and supplies it to the distributor 2. This signal can be, for example, an OFDM signal, a CDMA (Code Division Multiple Access) signal, or the like. The distributor 2 divides the reference signal from the signal generator 1 into two and distributes it to the gain adjusting circuit 3 and the system under test 6. The gain adjustment circuit 3 adjusts the gain with respect to the reference signal from the distributor 2 and outputs it to the adder 4. Here, the gain adjusting circuit 3 is configured so as to adjust only the gain for the entire signal and other frequency characteristics are not changed.
[0014]
The gain adjustment circuit 3 adjusts the gain so that the reference signal power supplied to the adder 4 is about 3 to 10 dB higher than the signal power supplied to the adder 4 through the system under test 6. This is because the reference signal from the gain adjustment circuit 3 is extracted as a main wave component and used as a reference in the propagation path characteristic calculation circuit 5 described later.
[0015]
The adder 4 adds the signal from the gain adjustment circuit 3 and the signal from the system under measurement 6 and outputs the sum to the propagation path characteristic calculation circuit 5. The propagation path characteristic calculation circuit 5 analyzes the signal supplied from the adder 4, obtains the frequency characteristic of the signal, and processes the frequency characteristic to propagate the frequency characteristic and delay profile of the measured system 6 Calculate and output road characteristics.
[0016]
In the following, the part for processing the frequency characteristic is included in the propagation path characteristic calculation circuit 5, but this may be processed by an external general-purpose computer or the like. In this specification, the frequency characteristic is information on complex numbers including amplitude and phase information with respect to frequency. A method for calculating the propagation path characteristic in the propagation path characteristic calculation circuit 5 will be described later.
[0017]
FIG. 2 is a block diagram when measuring a calibration value for correcting distortion of the frequency characteristics of the signal generator 1. In the figure, the same parts as those in FIG.
[0018]
In FIG. 2, each of the terminator 7 and the terminator 8 is a resistor serving as a characteristic impedance of the propagation path characteristic measuring apparatus 10. The terminator 7 is terminated so that the reference signal supplied to the measured system 6 at the time of measurement is not reflected because the measured system 6 is removed. Since the terminator 8 is removed from the system 6 to be measured, the input terminal of the adder 4 is opened, and is attached to prevent a mismatch that occurs for this purpose.
[0019]
Calibration value measurement and propagation path characteristic measurement according to the present invention are performed according to the procedure shown in the flowcharts shown in FIGS. Uppercase letters represent complex numbers, and lowercase letters represent real numbers.
[0020]
FIG. 3 shows a flowchart of a calibration value measurement process executed by the propagation path characteristic calculation circuit 5 with the configuration shown in FIG. In step S1 shown in FIG. 3, a calibration value for correcting distortion of the frequency characteristics of the reference signal from the signal generator 1 is measured. Here, the gain G of the gain adjusting circuit 3 is set to G = 1 (0 dB), and the frequency characteristic for calibration measured by the propagation path characteristic calculating circuit 5 is R (ω). Here, ω is an angular frequency. The calculation method of the frequency characteristic R (ω) for calibration will be described using an example using a training signal. The frequency spectrum of the training signal added by the signal generator 1 is Tr (ω), and the propagation path characteristic calculation circuit 5 If the frequency spectrum measured in (1) is Ir (ω), R (ω) is obtained as R (ω) = Ir (ω) / Tr (ω).
[0021]
Note that the calibration value measurement process shown in FIG. 3 does not have to be executed every time the propagation path characteristic measurement is performed, but only needs to be executed once when the propagation path characteristic measurement apparatus 10 is used for the first time.
[0022]
FIG. 4 shows a flowchart of a propagation path characteristic measurement process executed by the propagation path characteristic calculation circuit 5 with the configuration shown in FIG. In step S2 shown in FIG. 4, the propagation path characteristics of the measured system 6 are measured. At this time, the frequency characteristic observed at the input terminal of the propagation path characteristic calculation circuit 5 is defined as F (ω). The frequency characteristic F (ω) is calculated by using a method using a wide-band training signal inserted by the signal generator 1 or a method of calculating by removing the modulation component by averaging observation signals.
[0023]
In the method using the training signal, if the frequency spectrum of the known training signal is T (ω) and the frequency spectrum observed by the propagation path characteristic calculation circuit 5 is I (ω), the frequency characteristic F (ω) is It is obtained as F (ω) = I (ω) / T (ω).
[0024]
In step S3, a frequency characteristic C (ω) obtained by calibrating the frequency characteristic F (ω) with the frequency characteristic R (ω) of the signal generator 1 is obtained from the equation (1).
[0025]
C (ω) = F (ω) / R (ω) (1)
Next, in step S4, a vector D indicating the signal level of the reference signal from the gain adjustment circuit 3 included in the frequency characteristic C (ω) is calculated. Since the reference signal from the gain adjustment circuit 3 is gain-adjusted so as to be about 3 to 10 dB higher than the signal power passing through the system 6 to be measured, that is, to become the main wave of the observation signal, the frequency characteristic C The vector D of the main wave component can be calculated by calculating a complex average of (ω) with respect to the frequency axis.
[0026]
This is equivalent to extracting the component of delay 0 on the delay profile on the frequency axis. When the number of data of the frequency characteristic C (ω) is n, the vector D is obtained from the equation (2).
[0027]
D = {ΣC (ω)} / n (2)
Next, in step S5, the frequency characteristic C (ω) is divided by the vector D that becomes the signal level of the reference signal, and the frequency characteristic S (ω) calibrated so that the level of the reference signal becomes 1 is expressed by the equation (3). Calculate from
[0028]
S (ω) = C (ω) / D (3)
In step S6, the main wave component, that is, the reference signal component is removed from the frequency characteristic S (ω). Here, since the calibration is performed so that the level of the reference signal becomes 1 in the equation (3), the frequency characteristic X (ω) after the removal of the reference signal is calculated from the equation (4).
[0029]
X (ω) = S (ω) −1 (4)
Here, the reference signal from the gain adjustment circuit 3 added to the signal from the system under test 6 is gain-adjusted with the reference signal from the signal generation circuit 1, and therefore compared with the signal supplied to the system under test 6. Only the gain G is different. In order to calculate the frequency characteristic H (ω) including the gain of only the system under test 6 by calibrating the gain, in step S7, the frequency characteristic X (ω) after removing the reference signal is calculated using the equation (5). Calibrate.
[0030]
H (ω) = G · X (ω) (5)
In step S8, H (ω) is inverse Fourier transformed using equation (6) to obtain a delay profile P (t) of the system under measurement.
[0031]
P (t) = IFFT [H (ω)] (6)
However, t represents time and IFFT represents an inverse Fourier transform function. The frequency characteristic H (ω) and delay profile P (t) calculated in this way indicate only the propagation path characteristics of the system under measurement 6.
[0032]
In the present invention, the signal to be measured is only one system of the output signal of the adder 4. However, the adder 4 adds the reference signal, and the propagation path characteristic calculation circuit 5 performs signal processing based on the reference signal (step By performing S5 to S7), it is possible to accurately measure the time variation of the system under test with respect to the reference signal. Moreover, since only one signal is measured, the measurement time can be shortened.
[0033]
Moreover, since the reference signal component added by the adder 4 can be removed by using the expression (4), the propagation path characteristic measuring apparatus 10 can obtain the frequency characteristic and delay profile of the system under measurement 6. Of course, only one of the frequency characteristic and the delay profile may be obtained as necessary.
[0034]
By using this propagation path characteristic measuring apparatus 10, it is possible to accurately measure the time variation of the propagation path in the measured system 6. In addition, even if an existing propagation path characteristic measuring device of the type that observes only the signal that has passed through the system to be measured is used for the propagation path characteristic calculation circuit 5 in the configuration of FIG. In addition, by performing calculations from Equations (1) to (6) to the measurement result, it is possible to accurately measure the fluctuation of the propagation path of the system under measurement 6. The propagation path characteristic measuring apparatus 10 of the present invention is particularly effective for measuring reflected wave fluctuations and wraparound propagation path fluctuations.
[0035]
In the present specification, “and / or” means “and” or “or”.
[0036]
【The invention's effect】
As described above, the invention according to claim 1 generates and outputs a wideband reference signal, adjusts the level of one signal branched from the reference signal, and outputs the other signal branched from the reference signal. Supplied to the measurement system, the signal supplied through the system to be measured and the signal supplied after level adjustment are added, and the frequency characteristics measured from the added signal are measured with the system to be measured removed and terminated. was calibrated with a frequency characteristic, by calculating the frequency characteristic or the delay profile of the measurement system, it is possible to accurately measure the channel characteristics of the measurement system by simply measuring the signal of one system.
[0037]
According to the second aspect of the present invention, in the level adjustment of one signal branched from the reference signal, the signal power supplied by adjusting the level is higher than the signal power supplied from the system under measurement in the addition. By doing so, the reference signal is extracted as the main wave component, and by performing signal processing using this reference signal as a reference, it is possible to measure the time variation of the propagation path characteristic of the system under measurement.
[0038]
According to a third aspect of the present invention, there is provided a signal generator for generating and outputting a wideband reference signal, a gain adjusting circuit for supplying a level-adjusted signal to which one of the reference signals is branched, and branching the reference signal The adder that adds the signal that is supplied to the other system and the signal that is output through the system under test and the signal that is supplied from the gain adjustment circuit, and calculates the frequency characteristics or delay profile of the system under test from the signal added by the adder By having the propagation path characteristic calculation circuit that performs the measurement, it is possible to accurately measure the propagation path characteristic of the system under measurement only by measuring one system of signals.
[0039]
In the invention according to claim 4, the gain adjustment circuit adjusts the gain so that the signal power supplied from the gain adjustment circuit is higher than the signal power supplied from the system under measurement in the adder, A reference signal is taken out as a main wave component, and signal processing is performed using this reference signal as a reference, whereby the time variation of the propagation path characteristic of the system under measurement can be measured.
[0040]
In the invention described in claim 5, the channel characteristic calculation circuit, the frequency characteristic of the state of connecting the system under measurement, by calibrating the frequency characteristics calculated while terminating remove the system under measurement, the measuring system By calculating the frequency characteristic or the delay profile, it is possible to obtain the propagation path characteristic of only the system under measurement from which the distortion of the frequency characteristic of the measuring apparatus is removed.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a propagation path characteristic measuring apparatus according to the present invention.
FIG. 2 is a block diagram when measuring a calibration value for correcting distortion of a frequency characteristic of a signal generator.
FIG. 3 is a flowchart of a calibration value measurement process.
FIG. 4 is a flowchart of a propagation path characteristic measurement process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Signal generator 2 Divider 3 Gain adjustment circuit 4 Adder 5 Propagation path characteristic calculation circuit 6 System to be measured 7, 8 Terminator 10 Propagation path characteristic measuring device

Claims (5)

A propagation path characteristic measuring method for measuring a frequency characteristic or a delay profile of a propagation path of a measured system,
Generate and output a wideband reference signal,
Level-adjusting one of the signals branched from the reference signal and outputting it,
Supplying the other signal branched from the reference signal to the system under test;
Adding a signal supplied through the system to be measured and a signal supplied by adjusting the level;
The frequency characteristic measured from the added signal is calibrated with the frequency characteristic measured with the measured system removed and terminated, and the frequency characteristic or delay profile of the measured system is calculated. A method for measuring propagation path characteristics. In the propagation path characteristic measuring method according to claim 1,
The level adjustment of one signal branched from the reference signal is performed such that the signal power supplied by adjusting the level is higher than the signal power supplied from the system under measurement in the addition. A propagation path characteristic measuring method. A propagation path characteristic measuring apparatus for measuring a frequency characteristic or a delay profile of a propagation path of a measured system,
A signal generator for generating and outputting a broadband reference signal;
A gain adjusting circuit that is supplied and adjusts the level of one of the signals branched from the reference signal,
An adder for adding the signal supplied from the gain adjustment circuit and the signal supplied through the system under test to which the other signal branched from the reference signal is supplied;
A propagation path characteristic measuring apparatus comprising: a propagation path characteristic calculating circuit that calculates a frequency characteristic or a delay profile of the system under measurement from the signals added by the adder. In the propagation path characteristic measuring apparatus according to claim 3,
The gain adjusting circuit adjusts the gain so that the signal power supplied from the gain adjusting circuit is higher than the signal power supplied from the measured system in the adder. measuring device. In the propagation path characteristic measuring apparatus according to claim 3 or 4,
The channel characteristic calculation circuit, the frequency characteristic of the state of connecting the system under measurement, said by calibrating the frequency characteristics calculated while terminating remove the system under measurement, frequency characteristics or delay of the system under measurement A propagation path characteristic measuring apparatus characterized by calculating a profile.

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