JPH1096751A - Transmitting system characteristic measuring method for digital modulation signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitting system characteristic measuring method for a digital modulation signal in which a time for measuring the occupied zone width of transmitting system characteristic of the digital modulation signal and leakage electric power of an adjoining channel can be shortened without spoiling measuring accuracy. SOLUTION: The spectrum distribution data D11 of a signal to be tested Sin of digital modulation signal is seeked by a spectrum distribution measuring part 11, occupied zone width is seeked from the spectrum distribution data D11 by an occupied zone width detecting part 12 so as to obtain an occupied zone width measured result S12, and simultaneously adjoining channel leakage electric power is seeked from the spectrum distribution data D11 by an adjoining channel leakage electric power detecting part 13, so as to obtain an adjoining channel leakage electric power measured result S13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the occupied bandwidth of a digital modulation signal and the adjacent channel leakage power when measuring the occupied bandwidth of a digital modulation signal and adjacent channel leakage power. By sharing the spectrum distribution measurement unit that calculates
The present invention relates to a method for measuring a transmission characteristic of a digital modulation signal, which shortens a measurement time for measuring a transmission characteristic of a digital modulation signal.

[0002]

2. Description of the Related Art In a π / 4 shift QPSK modulation system employed in digital mobile communication such as a digital car telephone system and a second generation cordless telephone system, the occupied bandwidth of a digital modulation signal and adjacent channel leakage power are reduced. At the time of measurement, a digital modulation signal transmission system measuring device having an occupied bandwidth measuring device and an adjacent channel leakage power measuring device as shown in FIG. 3 is used.

[0003] The digital modulation signal transmission system characteristic measuring device shown in FIG. 3 comprises an occupied bandwidth measuring device 15 for measuring the occupied bandwidth of the digital modulated signal, and an adjacent channel leakage power measuring device 16. The signal under test Sin of the digital modulation signal is input to the spectrum distribution measuring unit 11A in the occupied bandwidth measuring device 15 and the spectrum distribution measuring unit 11B in the adjacent channel leakage power measuring device 16.

The output of the spectrum distribution measuring unit 11A is sent to an occupied bandwidth detecting unit 12, and the output of the spectrum distribution measuring unit 11B is sent to an adjacent channel leakage power detecting unit 13.

Next, a description will be given of a conventional method for measuring the transmission system characteristics of a digitally modulated signal using the digitally modulated signal transmission system measuring apparatus of FIG.

In the spectrum distribution measuring section 11A,
When the digitally modulated signal under test Sin is input, a single sweep is performed with the test frequency set value ft as the center frequency, and the spectrum distribution is measured.

The sweep frequency width is set to about 3.5 times the occupied bandwidth, and all sample points within the sweep frequency width centered on the test frequency set value ft are taken into the occupied bandwidth detector 12 as spectrum distribution data D11A.

The test frequency set value (ft)-(sweep frequency width / 2) is the lowest frequency (f1), and the test frequency set value (ft) + (sweep frequency width / 2) is the highest frequency (f4).
And the sample points from the lowest frequency f1 to the highest frequency f4 are all sample points.

The occupied bandwidth detector 12 calculates the total sum of all sample points Din of the acquired spectrum distribution data D11A of the sweep frequency width, and sets the sum as the total power.

Next, power addition is performed sequentially from the lowest frequency f1 to obtain a limit sampling point at which 0.5% of the total power is obtained, converted to a frequency, and a lower limit frequency f2 is obtained.

Similarly, power addition is sequentially performed downward from the highest frequency f4, a limit sampling point at which 0.5% of the total power is obtained is obtained, and converted to a frequency to obtain an upper limit frequency f3. Here, the occupied bandwidth is the upper limit frequency (f3) -the lower limit frequency (f2).

Next, measurement of adjacent channel leakage power will be described. The digitally modulated signal under test Sin is input to the spectrum distribution measuring unit 11B in the adjacent channel leakage power measuring device 16, and a single sweep is performed with the test frequency set value ft as the center frequency, and the spectrum distribution is measured. The distribution data D11B is sent to the adjacent channel leakage power detection unit 13.

The adjacent channel leakage power detector 13 calculates the total power at sample points of a specified bandwidth centered on the test frequency set value ft and stores it as the total power Pc.

Next, the center frequency is set to a test frequency set value ft.
The sum of powers is obtained for sample points of a specified bandwidth where + detuning frequency = f, and stored as upper adjacent channel leakage power Pu.

The center frequency is set to a test frequency set value ft.
-A power sum is calculated for sample points of a specified bandwidth where detuning frequency = f, and stored as lower adjacent channel leakage power Pl. The upper adjacent channel leakage power ratio is 10 × log
(Pc / Pu), the lower adjacent channel leakage power ratio is 10 ×
log (Pc / Pl).

[0016]

When the transmission characteristics of a digital modulation signal are measured by such a conventional method for measuring the transmission characteristics of a digital modulation signal, the occupied bandwidth measurement and the adjacent channel leakage power measurement are measured together. Often done.

The measurement of the occupied bandwidth and the measurement of the adjacent channel leakage power are measurement items after spectrum analysis, and the same processing is repeated in one transmission characteristic test. Become.

That is, the conventional measurement of the occupied bandwidth and the measurement of the adjacent channel leakage power are independent of each other as individual measurement items, so that the spectrum distribution is measured in each measurement.

Since the measurement of the occupied bandwidth and the measurement of the adjacent channel leakage power are always performed in the measurement of the characteristics of the transmission system, the spectrum distribution measurement is performed twice in one measurement of the transmission system characteristics. The measurement time becomes longer as shown in FIG.

[0020]

In order to solve the above-mentioned conventional problems, a method for measuring the transmission system characteristics of a digitally modulated signal according to the present invention comprises the steps of: Data D1
1; measuring the occupied bandwidth of the digital modulation signal from the spectrum distribution data D11 obtained by the spectrum distribution measurement unit 11 by the occupied bandwidth detection unit 12; and measuring the occupied bandwidth of the digital modulation signal. And measuring the adjacent channel leakage power from the spectrum distribution by the adjacent channel leakage power detection unit 13 at the same time.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the transmission characteristic measurement method for digitally modulated signals of the present invention, a signal under test Sin of a digitally modulated signal is input to a spectrum distribution measuring section 11;
A single sweep is performed with the test frequency as the center frequency, the spectrum distribution is measured, and the spectrum distribution data D11 is transmitted to the occupied bandwidth detection unit 12 and the adjacent channel leakage power detection unit 13, and the occupied bandwidth detection unit 12 transmits the spectrum distribution data D11. Data D
11 and the adjacent channel leakage power detection unit 13 simultaneously calculates the adjacent channel leakage power from the spectrum distribution data D11.

Next, an embodiment of the method of measuring the transmission system characteristics of a digital modulation signal according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a digital modulation signal transmission system characteristic measuring apparatus applied to an embodiment of the present invention.

The digital modulation signal transmission system characteristic measuring apparatus 14 shown in FIG. 1 inputs the signal under test Sin of the digital modulation signal to the spectrum distribution measuring section 11 and performs a single sweep using the test frequency set value ft as the center frequency. To measure the spectral distribution and obtain the spectral distribution data D1.
1 to the occupied bandwidth detector 12 and the adjacent channel leakage power detector 13 at the same time.

The occupied bandwidth detector 12 obtains the occupied bandwidth from the spectrum distribution data D11 and outputs the occupied bandwidth measurement result S12. At the same time, the adjacent channel leakage power detector 13 outputs the occupied bandwidth power D11.
, The adjacent channel leakage power is obtained, and the adjacent channel leakage power measurement result S13 is output.

Next, a description will be given of a method for measuring the transmission system characteristics of a digital modulation signal by applying the digital modulation signal transmission system characteristic measuring device 14 having such a configuration to one embodiment of the present invention.

The digitally modulated signal is used as the signal under test Sin and is input to the spectrum distribution measuring unit 11. The spectrum distribution measurement unit 11 performs a single sweep using the test frequency set value ft as a center frequency, measures the spectrum distribution, and obtains spectrum distribution data D11.

The spectrum distribution data D11 is simultaneously sent to the occupied bandwidth detector 12 and the adjacent channel leakage power detector 13, where the occupied bandwidth and the adjacent channel leakage power are obtained.

The occupied bandwidth detecting section 12 sets the sweep frequency width of the spectrum distribution data D11 to 3 times the occupied bandwidth.
A sample point having a sweep frequency width centered on the test frequency set value ft is taken as about five times.

Test frequency set value ft−sweep frequency width / 2
Is the lowest frequency f1, the test frequency set value ft + sweep frequency width / 2 is the highest frequency f4, and sample points from the lowest frequency f1 to the highest frequency f4 are all sample points.

The occupied bandwidth detector 12 calculates the total sum of all sample points of the acquired sweep frequency width and sets the sum as the total power Pb. Next, power addition is performed sequentially from the lowest frequency f1 to obtain a limit sample point at which 0.5% of the total power Pb is obtained, and the frequency is converted into a frequency to obtain a lower limit frequency f2.

Similarly, power addition is sequentially performed downward from the highest frequency f4, a limit sample point at which 0.5% of the total power is obtained is obtained, and converted to a frequency to obtain an upper limit frequency f3. Here, the upper limit frequency f3 and the lower limit frequency f2 are output as the occupied bandwidth measurement result S12.

Further, the adjacent channel leakage power detection unit 13 obtains the power sum at sample points of a specified bandwidth centered on the test frequency set value ft in the spectrum distribution data D11 and stores the sum as the total power Pc. Next, the sum of the powers is obtained for the sample points of the specified bandwidth where the center frequency is the test frequency set value ft + the detuning frequency = f, and stored as the upper adjacent channel leakage power Pu.

The center frequency is set to a test frequency set value ft.
-A power sum is calculated for sample points of a specified bandwidth where detuning frequency = f, and stored as lower adjacent channel leakage power Pl. The upper adjacent channel leakage power ratio is 10 × log
(Pc / Pu), the lower adjacent channel leakage power ratio is 10 ×
log (Pc / Pl).

As is apparent from the above, in the measurement of the transmission characteristics of the digital modulation signal, the spectrum distribution measurement is performed twice by individually measuring the occupied bandwidth measurement and the adjacent channel leakage power measurement as in the related art. In contrast to the fact that the measurement time required to be unavoidable was 700 ms, in one embodiment of the present invention, the spectrum distribution measurement is performed by simultaneously performing the occupied bandwidth measurement and the adjacent channel leakage power measurement. Is performed only once, and the occupied bandwidth measurement and the adjacent channel leakage power measurement are performed using the same spectrum distribution data D11. Therefore, the measurement time is reduced to 400 ms.

Next, an example of applying the method of measuring the transmission system characteristics of the digital modulation signal of the present invention to the specification (RCR-STD28) of the second generation cordless telephone system will be described with reference to FIG.

FIG. 2 shows a π / 4 QPSK modulated signal in the second generation cordless telephone system as a signal under test Sin, and a digital signal for simultaneously measuring the occupied bandwidth of the signal under test Sin and adjacent channel leakage power. FIG. 3 is a block diagram illustrating a configuration of a transmission signal measurement device for a modulated signal.

In FIG. 2, a signal subjected to π / 4 QPSK modulation is input to an A / D (analog / digital) converter 17 as a signal under test Sin.
7 is output to a digital signal processor (hereinafter referred to as DSP).
18).

The DSP 18 has the same internal configuration as the digital modulation signal transmission system measuring apparatus 14 shown in FIG. Therefore, in the following description, the DSP 18
In the description of the internal configuration of FIG. 1, the same parts as those in FIG.

Now, the test frequency set value ft is set to the intermediate frequency 2.5 MHz, the π / 4 QPSK-modulated signal is used as the signal under test Sin, and the signal under test Sin is input to the A / D converter 17.

The A / D converter 17 converts the signal under test Sin into
Time-series data is obtained by sampling at 10 MHz. At this time, 32,768 pieces of time-series data are input to the DSP 18, and D
The spectrum distribution measuring unit 11 realized by software on the SP performs a fast Fourier transform of 32,768 data items to obtain a spectrum distribution D11.

The processing time in the fast Fourier transform processing is about 250 ms, and the processing time of the occupied bandwidth is about 300 ms.
occupies 5/6 ms. The sweep frequency width of the occupied bandwidth is
Standard of occupied bandwidth by RCR-STD28 (288kHz)
It is set to 1 MHz which is about 3.5 times.

The sweep frequency of the adjacent channel leakage power measurement is such that the detuning frequency f is ± 900 kHz, and the specified bandwidth is ± 900 kHz.
Since it is 96 kHz, ± (900 kHz +
96 kHz) becomes the sweep frequency, and 2 MHz or more is required.

From the above, the spectrum distribution measuring section 1
In the case of 1, if the spectrum distribution data D11 having a sweep frequency width of 2 MHz is output, the conditions of the occupied bandwidth measurement and the adjacent channel leakage power are satisfied.

Next, in the occupied bandwidth detecting section 12, data having a sweep frequency width of 1 MHz (± 500%) with the test frequency set value ft as the center frequency among the spectrum distribution data D11.
kHz) into the array.

Since the test frequency set value ft is 2.5 MHz, the lowest frequency f1 is 2 MHz and the highest frequency f4
Is 3 MHz, and the sum of the spectrum arrangement from 2 MHz to 3 MHz is obtained as the total power Pb.

The lower limit frequency f2 is the lowest frequency f1 = 2 MH
The power is added in order from z upward to find a point at which 0.5% of the total power Pb is obtained, and frequency conversion is performed. The power is added to the upper limit frequency f3 in order from the highest frequency f4 = 3 MHz and a point at which 0.5% of the total power is obtained is converted. The occupied bandwidth measurement result S12 is obtained by lower limit frequency + upper limit frequency / 2.

Next, the adjacent channel leakage power detector 13 takes in data of a specified bandwidth (± 96 kHz) with the test frequency set value ft as the center frequency from the spectrum distribution data D11. Test frequency set value ft is 2.5
Since the frequency is MHz, the sum of the spectrum arrangement from 2.404 MHz to 2.596 MHz is obtained, and is set as the total power Pc.

Next, since the detuning frequency f is 900 MHz,
The center frequency is set to 2.5 MHz + 900 MHz = 3.4 MHz, and data of a specified bandwidth (± 96 kHz) is taken into the array.

The sum of the spectrum arrangement from 3.304 MHz to 3.496 kHz is obtained and stored as the upper adjacent channel leakage power Pu. In the lower adjacent channel leakage power measurement, the center frequency is set to 2.5 MHz-900 MHz = 1.6 MHz, and data having a specified bandwidth (± 96 kHz) is taken into an array.

The sum of the spectrum arrangement from 1.504 MHz to 1.696 kHz is obtained and stored as the lower adjacent channel leakage power Pl. Upper adjacent channel leakage power ratio is 10 × lo
g (Pc / Pu), the lower adjacent channel leakage power ratio is 10
× log (Pc / Pl) As a result, the processing time for one spectrum distribution measurement can be reduced to 250 ms.

[0051]

As described above, according to the method for measuring the transmission characteristics of a digitally modulated signal according to the present invention, the spectrum distribution data of the signal under test of the digitally modulated signal is obtained once by the spectrum distribution measuring section. The occupied bandwidth detector detects the occupied bandwidth of the digital modulation signal from the data, and the adjacent channel leakage power detector calculates the adjacent channel leakage power from the same spectrum distribution data. Meanwhile, the measurement time can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a digital modulation signal transmission system characteristic measuring apparatus applied to an embodiment of a digital modulation signal transmission system characteristic measuring method according to an embodiment of the present invention.

FIG. 2 shows a method of measuring transmission system characteristics of a digitally modulated signal according to the present invention using an RCR-S of a second generation cordless telephone system.
FIG. 3 is a block diagram showing a configuration of a digital modulation signal transmission system characteristic measuring apparatus applied when measuring an occupied bandwidth of a signal under measurement and adjacent channel leakage power that have been subjected to π / 4 QPSK modulation based on the TD28 specification.

FIG. 3 is a block diagram showing a configuration of a digital modulation signal transmission system characteristic measuring apparatus applied to a conventional digital modulation signal transmission system characteristic measuring method.

[Explanation of symbols]

 11 Spectrum Distribution Measurement Unit 12 Occupied Bandwidth Detection Unit 13 Adjacent Channel Leakage Power Detection Unit 14 Digital Modulation Signal Transmission System Characteristics Measurement Device 17 A / D Converter 18 DSP (Digital Signal Processor) Sin Signal Under Test S12 Occupied Bandwidth Measurement Result S13 Adjacent channel leakage power measurement result Din sampling data D11 Spectrum distribution data

Claims (2)

[Claims] A step of obtaining spectrum distribution data (D11) of a signal under test (Sin) of a digitally modulated signal by a spectrum distribution measuring section (11); and a step of measuring said spectrum distribution measuring section by an occupied bandwidth detecting section (12).
Measuring the occupied bandwidth of the digital modulation signal from the spectrum distribution data (D11) obtained in (11), and measuring the occupied bandwidth of the digital modulation signal and simultaneously measuring the occupied bandwidth of the digital modulation signal by the adjacent channel leakage power detection unit (13). Measuring the adjacent channel leakage power from the distribution; and measuring the transmission characteristic of the digital modulation signal. 2. The method according to claim 1, wherein the spectrum distribution measuring section (11) converts the signal under test (Sin) modulated by π / 4 QPSK to an analog / digital converter.
A method for measuring transmission system characteristics of a digitally modulated signal, characterized by obtaining spectrum distribution data of the signal digitally converted in (17).