JPH0735789A - Device and method for measuring power of spectrum analyzer - Google Patents

Abstract

PURPOSE:To provide a device and method for measuring power which can measure a total power and an average power accurately without any error in measuring noise and spectrum diffusion signal. CONSTITUTION:In a spectrum analyzer, an input signal is converted to a genuine number of PPn=10P<n/10> by providing a genuine number conversion part 11. Then, by providing an average value calculation part 12, an average value of PPa=(PP1+PP2+...+PPN) is obtained. Then. by providing a logarithmic conversion part 13, an average power is obtained by Pavg=10logPPa, thus constituting a power measuring instrument. Also, by providing a total power calculation part 14 and by multiplying an average power per unit by a measurement frequency value, a device for obtaining the total power may be configured. Also, the operation may be realized as a method for measuring power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for measuring power in a spectrum analyzer, which is provided with means for calculating average power by a fixed procedure and calculating total power.

[0002]

2. Description of the Related Art In recent years, spread spectrum wireless systems have been proposed, and it is necessary to measure the output power of these wireless devices. The spread spectrum method is a communication method in which a signal is spread over a wider frequency band than a normal method and power per frequency is reduced to be transmitted. In addition to ordinary modulation, a high-speed code sequence called a spreading code is used to perform modulation for spreading the frequency spectrum of the signal in a wide band. In the spread spectrum communication system, the frequency band is widely used, but since the signal energy is constant, the power per frequency is low.

Hitherto, when measuring power, a power meter, a spectrum analyzer, etc. have been used. However, with a power meter sensor, it is difficult to arbitrarily set the frequency band, and the power measurement width (dynamic range) is +10 dBm-60.
There is a problem that it is narrow at about dBm.

Therefore, in the case of measuring the power using a spectrum analyzer, the following method is adopted.

FIG. 2 is a block diagram showing the structure of a conventional spectrum analyzer.

The input signal is changed to a constant intermediate frequency through the output of the voltage-controlled local oscillator 7 controlled by the sweep signal generator 7 and the mixer 1 and input to the resolution bandwidth filter 2. When a Gaussian filter, for example, is used as the resolution bandwidth filter, the bandwidth (frequency width at the point where 3 dB falls from the peak) is 1/2 of the actual bandwidth.

Further, the resolution bandwidth filter has a plurality of stages of bandwidth switching functions, and enables the frequency analysis, which is the greatest feature of the spectrum analyzer.

Further, the signal is inputted from the resolution band filter 2 to the logarithmic amplifier 3 for expanding the dynamic range of the level, converted into the level versus the frequency, and the output of the detector 4 is converted into an analog signal by the A / D converter 5. Digitally converted. The result is displayed on the CRT by the display 6 controlled by the signal of the sweep signal generator.

In general, the detection method (slope detection method) of a spectrum analyzer is configured so that an average value detection is performed on one sine wave and a fixed conversion is performed so that the display matches the value of the effective value. . Therefore, in the case of an input signal having a spread spectrum, there is a difference from the actual effective value.

Further, it is generally known that an error occurs when a signal having a spectrum spread is detected as an average value through a logarithmic amplifier. For example, the correction for the display is known to reach 1.05 dB in log mode.

Generally, the phase of the spectrum component of random noise is random, and when the measurement bandwidth of the analyzer is doubled, the measurement voltage does not double, but the measurement power doubles. Therefore, the random noise is the noise power per unit bandwidth (dB / Hz or Watt / H
It is usually specified in z).

Further, when the input signal is a random noise signal, the above spectrum analyzer handles the noise that has passed through the resolution bandwidth filter, and assuming that the noise is Rayleigh distributed, these differences are It is known that the error due to compression in the logarithmic amplifier can be calculated to be −2.5 dB. Here, the Rayleigh distribution indicates a distribution state of scattering and means an envelope component of white noise.

[0013]

As described above, when attempting to measure the power of a spread spectrum signal and random noise, it is necessary to measure the entire frequency band of the radio wave to be measured. In this case, since the measurable bandwidth of the power sensor of the measuring instrument cannot cover the entire bandwidth by one, there is a problem that a true value cannot be obtained. Therefore, it is recommended to use a spectrum analyzer that can cover the entire bandwidth. It is advantageous.

However, when attempting to measure the power of the spread spectrum signal and the random noise, the spectrum spreads over a wide band, so that the above-mentioned detection method and logarithmic amplification method have a problem that the error increases.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and when measuring the power of noise or spread spectrum signals, no error is produced and the accuracy is high. An object of the present invention is to provide a power measuring device and method capable of measuring power and measuring average power.

[0016]

According to the present invention, in a spectrum analyzer, an antilogarithm converter 1 for performing antilogarithmic conversion of a signal obtained by analog-digital converting an input signal.
1 is set. This is to get the instantaneous value of the input signal,
This is because the output of the A / D converter 5 is converted to the power antilogarithm.
In addition, the output of the A / D converter 5 is amplified by a video bandwidth having a bandwidth sufficiently wider than the resolution bandwidth (not shown).
The RT display shows the instantaneous value of the signal.

The antilogarithm conversion unit 11 performs the antilogarithmic conversion so that PP _n = 10 ^{Pn / 10} (mW), for example, when the measurement level P _n (dBm) at the sample point X _n is set. Next, the average value calculation unit 12 for calculating the average value is provided. Then, the sum of the values of PP _n is calculated at a point where n is from 1 to N, and is divided by N to obtain PP _a = (PP ₁ + PP ₂ + ... + PP _N ) / N (m
W) is obtained. Next, a logarithmic conversion unit 13 for performing logarithmic conversion is provided. Then, the value of PP _a is logarithmically converted to obtain the average power by P _avg = 10 logPP _a (mW). In this way, the power measuring device for _obtaining P _avg (mW) is configured.

Further, in the above apparatus, a total power calculation unit 14 for calculating the total power is provided, and the resolution bandwidth is 1H.
A power measuring device is configured by adding means for obtaining the total power displayed on the CRT of the spectrum analyzer by multiplying the average power (mW / Hz) converted to z by the measurement frequency width (SPAN). Good.

Further, although the above-mentioned configuration is realized by configuring a hardware device, it is expressed as a software calculation method.

For a calculation that satisfies the following equation, that is, for a signal obtained by analog-digital converting the input signal, the sampling point X
calculates the measured level P _n antilogarithm conversion (dBm) at _n, then calculates the average value, then log-transformed to calculate the average power, by performing the calculation of the average power May be realized as a power measuring method.

[0020]

According to the present invention, in the spectrum analyzer, the antilogarithm conversion unit, the average value calculation unit, and the logarithm conversion unit are provided, so that the average power can be obtained by a series of calculation results. .

Furthermore, it is possible to obtain the total power displayed on the spectrum analyzer by additionally providing the above-mentioned device with a total power calculation section.

Further, although the above-mentioned configuration is realized by configuring a hardware device, it is expressed as a software calculation method.

It is also possible to obtain the average power and the total power by performing a series of calculations that satisfy the following equation.

[0023]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 3 is a conceptual diagram showing the operation of the present invention.

The input signal passes through the A / D converter 5 and undergoes analog-to-digital conversion and is given to the antilogarithm conversion unit 11.

The spectrum analyzer can measure the measurement level P _n at the sample point X _n .

In the antilogarithm conversion unit 11, the antilogarithmic conversion of the measurement level P _n (dBm) is carried out so that PP _n = 10 ^{Pn / 10} (mW).

Next, in the average value calculation unit 12, PP _n
Value is calculated at a point where n is from 1 to N, divided by N, and PP _a = (PP ₁ + PP ₂ + ... + PP _N ) / N (m
W) is obtained.

Next, in the logarithmic converter 13, PP _a
The value of is logarithmically converted, and the average power is obtained by P _avg = 10 logPP _a (mW).

The average power P (mW / Hz) per 1 Hz can be obtained by dividing the average power (mW) by the measured noise power bandwidth (Bn) of the spectrum analyzer.

Further, in the total power calculation unit 14, 1H
Average frequency per z (mW / Hz) and measured frequency width (S
By multiplying it by PAN), the total power displayed on the spectrum analyzer can be obtained.

[0033]

Since the present invention is constructed as described above, it has the following effects.

When measuring the power of noise and spread spectrum signals, the total power and average power can be measured with high accuracy without causing an error.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional spectrum analyzer.

FIG. 3 is a conceptual diagram showing an operation of the present invention.

[Explanation of symbols]

 1 mixer 2 resolution bandwidth filter 3 logarithmic amplifier 4 detector 5 A / D converter 6 display 7 sweep signal generator 11 antilogarithm converter 12 average value calculator 13 logarithmic converter 14 total power calculator

Claims (4)

[Claims] 1. In a spectrum analyzer, an antilogarithm conversion unit (11) for performing antilogarithmic conversion of a signal obtained by analog-digital conversion of an input signal is provided, and a sampling point X is provided.
measuring levels P _n at _n the (dBm) and antilogarithm converter such that ^{_{PP n = 10 Pn / 10 (}} mW), the average value calculating unit for averaging the true number of output (1
2) is provided, the value of PP _n is summed at the point where n is from 1 to N, and is divided by N to obtain PP _a = (PP ₁ + PP ₂ + ... + PP _N ) / N (m
W) to obtain an average value and logarithmically convert the average value output (1)
3) is provided, the value of PP _a is logarithmically converted to obtain an average power of P _avg = 10 logPP _a (mW), and the above-mentioned arithmetic units are provided to configure the power measuring apparatus. 2. The device according to claim 1, further comprising a total power calculation unit (14) for calculating total power, and calculating the average power P _avg = 10 logPP _a (mW) obtained in claim 1. By multiplying the average power per 1 Hz (mW / Hz) divided by the measurement noise power bandwidth by the measurement frequency width (SPAN), the total power displayed on the spectrum analyzer is obtained, and the above calculation unit is provided. A power measuring device characterized by being configured. 3. When measuring an input signal with a spectrum analyzer, the following equation is used. That is, for the signal obtained by analog-digital conversion of the input signal, the arithmetic conversion of the measurement level P _n (dBm) at the sample point X _n is calculated, then the average value is calculated, and then the average value is calculated. A power measuring method characterized by obtaining the average power by performing logarithmic conversion to calculate the average power and performing the above calculation. 4. The method according to claim 3, further comprising: an average power per 1 Hz (mW / Hz) obtained by dividing the average power obtained in claim 3 by a measurement noise power bandwidth (SPAN). ) Is calculated to calculate the total power displayed on the spectrum analyzer, and the total power is obtained by performing the above calculation.