JP2997165B2 - Apparatus and method for measuring adjacent channel leakage power - Google Patents

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 leakage power, which makes it possible to measure the transition of time-domain power in an adjacent channel of a transmitter.

[0002]

2. Description of the Related Art Conventionally, when measuring leakage power in a channel adjacent to a transmitter, a steady evaluation is performed in the frequency domain.

FIG. 7 is a waveform example of a transmission channel and an adjacent channel. As shown in FIG. 7A, in a transmission channel, information is transmitted in a burst for a certain period of time by a time division method. This burst-on period is called one slot. The repetition time of the burst pulse is called one frame. For example, in the digital MCA, one frame is composed of six slots. Thus, in the transmission channel, the TDMA
(Time-division multiplexing) When an instantaneous change occurs, such as a burst signal, an interference wave is generally induced in an adjacent channel assigned along with the frequency.

[0004] FIG. 7B shows the relationship between adjacent channels.
4 shows an example of a leakage power waveform. Adjacent to the top or bottom,
Leakage power is generated in the secondary, tertiary, etc. channels. The maximum value in the adjacent channel is the peak power.

FIG. 8 shows a conventional example of measuring leakage power. First, an average value is measured for all of the burst-on section and the burst-off section using a power meter. Next, the average power in the burst-on section is calculated in consideration of the duty ratio of the burst-on section in the entire section. Thus, the value obtained by the power meter is an average value, and the peak power as shown in FIG. 7B cannot be known.

As a conventional measurement example, there is a measurement method using a spectrum analyzer. In this method, after measuring in a time domain using a commercially available spectrum analyzer, an average power is calculated by calculation in a burst-on section. However, when using a spectrum analyzer, sampling is inevitably involved,
Generally, in order to reliably capture and measure the maximum power, sampling of one point or more per frame is required. Thus, the sweep time, for example, one slot is 15 ms, one frame in six slots and is configured, 90 ms is needed to pair 1 point. If the spectrum analyzer has a frequency axis of 500 points, one measurement requires 45 seconds. Therefore, it takes a long time for the measurement.

[0007]

In recent years, it has become necessary to measure instantaneous phenomena such as interference waves at the rise and fall of a burst wave in TDMA communication. However, even with the use of the above power meter,
Even by using a spectrum analyzer, only the average value of adjacent leakage power of one frame can be measured, and an instantaneous phenomenon such as a TDMA burst signal cannot be measured.

[0008] The object of the present invention is to eliminate these disadvantages,
Measurement method of adjacent channel leakage power (ADJACENT CHANNNL P
OWER), using digital signal processing technology, ACP of time domain power in adjacent channel of transmitter
An object of the present invention is to provide an apparatus and a method for measuring adjacent channel leakage power, which can measure the transition.

[0009]

SUMMARY OF THE INVENTION In a measuring apparatus such as a transmitter for measuring adjacent channel leakage power from an object to be measured 1, an output of a local oscillator 6 and the output of the object to be measured 1 are measured.
And a mixer 8 for mixing the signal with the signal from the mixer. The A / D converter 3 converts the output signal of the mixer 8 from analog to digital by the output of the sampling frequency oscillator 7.
Is provided. Then, a Hilbert converter 403 for converting the digital data into a complex signal is provided. And
A low-pass filter 404 for removing unnecessary frequency components from the output signal of the Hilbert transformer is provided. Then, a band-pass filter 406 for converting the low-pass filter output signal into characteristics according to the communication system is provided. Then, a power calculation unit 407 for calculating the power of the complex signal from the band-pass filter is provided to configure an adjacent channel leakage power measurement device.

In the above-described measuring apparatus, a decimation section 405 for thinning out the output data of the low-pass filter 404 at a constant rate is provided. May be configured.

As a measuring method, in a measuring method for measuring adjacent channel leakage power from an object to be measured such as a transmitter, a local oscillator output is mixed with a signal from the object to be measured by a mixer. The mixer frequency is changed to an intermediate frequency (step 110), the mixer output signal is converted from analog to digital by an A / D converter by the sampling frequency oscillator output (step 130), and the digital data is converted to a complex signal by a Hilbert converter. (Step 150), removes unnecessary frequency components from the output signal of the Hilbert transformer by a low-pass filter (Step 160), and converts the output signal of the low-pass filter into characteristics according to the communication system by a band-pass filter. (Step 180), and the power calculation unit
The power calculation of the complex signal from the band-pass filter is performed (step 190), and the adjacent channel leakage power measuring method may be configured in such a procedure.

In the above-mentioned measuring method, the output data of the low-pass filter is thinned out by a decimation unit by a predetermined amount (step 170), and the output signal of the decimation unit is converted to the band-pass filter (step 1).
80), a method of measuring adjacent channel leakage power may be configured.

[0013]

According to the present invention, the A / D conversion frequency is 220
Since the frequency is about kHz, analog-digital conversion can be sufficiently performed in real time. Then, real-time processing can be performed on the real number signal and the imaginary number signal that have been subjected to the Hilbert transform. Also, if necessary, to perform decimation,
No excessive burden on processing time. Then, since the characteristics of the band-pass filter conform to the standard of each communication system, data with good reproducibility can be obtained. The band-pass filters are provided for a carrier channel, an upper adjacent channel, a lower adjacent channel, and the like. Then, the power calculation unit calculates the sum of squares of the real part and the imaginary part to obtain the adjacent channel leakage power. Since the calculation result is obtained in real time, instantaneous changes and accompanying bus <br/> over be sampled signal, the transition of the power of the time domain obtained accurately.

[0014]

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

FIG. 1 is a block diagram showing one embodiment of the present invention. As shown in FIG. 1, a signal to be measured from the DUT 1 is converted by a mixer 8 into a frequency fL from a local oscillator 6.
To convert to the intermediate frequency fIF. Next, of the intermediate frequencies, only the signal of interest out of the sum signal or the difference signal is extracted by the low-pass filter LPF2. Next, the A / D converter 3 converts the analog signal into a digital signal using the frequency fSP from the sampling frequency oscillator 7 and performs digitization.

Here, the selection of the intermediate frequency fIF is set to a low frequency at which analog / digital conversion is possible.
Set to about 20 kHz. For this reason, the mixer 8 may be composed of a plurality of stages if necessary, and the frequency may be reduced stepwise.

The data digitized by the A / D converter 3 is subjected to a constant signal processing as described in detail below by a signal processing operation unit (DSP) 4 to obtain adjacent channel leakage power, and a display unit is provided. 5 is displayed.

FIG. 2 shows a block diagram in a DSP according to the present invention. FIG. 4 shows how the frequency conversion is performed in the measuring device and the measuring method according to the present invention. As shown in FIG. 2, in the signal processing arithmetic unit (DSP) 4, first,
Intermediate frequency f quantified by sampling frequency fSP
A second LPF 402 removes a high frequency signal component in an unnecessary band from the IF signal 401. As shown in FIG. 4B, the second LPF is configured to remove a signal component having a frequency higher than fSP / 4.

Next, the Hilbert converter 4
03, the input signal is vectorized and converted into a complex number, and two signals (I, Q) of a real number signal and an imaginary number signal are output. Two signals generated by this Hilbert transform pair, (f
H ± fIF), only the signal of interest is transferred to the third LPF 40
Remove with 4. For example, the (fH + fIF) component is removed by the third LPF. Thereafter, the data is decimated (decimated) by the decimation unit 405 as necessary. This is to reduce the number of processed data to the extent that the amount of information included in the data is not impaired in order to shorten the subsequent processing time. That is, the sampling rate is adjusted to the minimum necessary so as not to be excessive in the subsequent processing. For example, decimation is performed on 1/4.

Next, a band pass filter having the same characteristics as those used for the communication device is applied by the BPF 406. The filter characteristics are prepared in accordance with various standards such as D-MCA, by di-di Tal type,
It may be configured by an analog type. This filter prepares and measures a required number of carrier channels and adjacent channels. For example, a band pass filter is applied to three frequencies of a carrier channel, an upper adjacent channel, and a lower adjacent channel.

Next, the power calculator 407 obtains the sum of squares of the real part and the imaginary part, (I2 + Q2). This is the required adjacent channel leakage power. And it is also a time transition of the instantaneous value. FIG. 5 shows the signal processing operation in three dimensions of frequency, time, and power. In FIG. 5, three channels are processed at the same time, but the number of channels may be increased to five channels, if necessary. The calculation result can be subjected to an averaging process or the like as necessary. For example, the average A within the TDMA slot
CP, average ACP within TDMA frame, peak ACP,
It is possible to obtain a calculation result such as the digital modulation unit average ACP.

The calculation result by the DSP 4 is displayed on the display unit 5. FIG. 6 shows a display example of the leakage power of the adjacent channel. FIG. 6A shows a carrier channel, and FIG.
(B) is the upper adjacent channel (+25 kHz), FIG.
(C) shows the lower adjacent channel (−25 kHz).

In the block diagram of the present invention, the primary AC
Although the measurement is performed only up to the measurement of P, in order to enable the measurement of the second, third,..., The center frequency of the local oscillation frequency fL is appropriately shifted or the like, which is obtained by performing the signal processing a plurality of times. Good. Also, if the filter characteristics of the BPF 406 are changed to characteristics according to the communication system, such as PDC, PHS, NADC, etc., A
CP can be measured accurately. Further, the APC measurement and the modulation analysis may be performed on the same data, and the time axis of the measurement result may be observed in synchronization with the demodulated data.

In the above, the configuration has been described as an adjacent channel leakage power measuring device. However, an adjacent channel leakage power measuring method in which a series of procedures are executed to perform measurement may be used. FIG. 3 is a flowchart showing the measurement procedure.

[0025]

[0026]

[0027]

[0028]

Since the present invention is configured as described above, the following effects can be obtained. An apparatus and a method for measuring adjacent channel leakage power that can measure the ACP transition of the power in the time domain in the adjacent channel of the transmitter can be provided. .

[Brief description of the drawings]

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

FIG. 2 shows a block diagram in a DSP according to the invention.

FIG. 3 is a flowchart showing a measurement procedure.

FIG. 4 shows how frequency conversion is performed in signal processing according to the present invention.

FIG. 5 shows the operation of signal processing in three dimensions: frequency, time, and power.

FIG. 6 shows a display example of leakage power of an adjacent channel. (A) shows a carrier channel, (b) shows an upper adjacent channel (+25 kHz), and (c) shows a lower adjacent channel (−25 kHz).

FIG. 7 is a waveform example of a transmission channel and an adjacent channel.

FIG. 8 is a conventional example of measuring leakage power.

[Explanation of symbols]

 Reference Signs List 1 DUT 2 LPF 3 A / D converter 4 DSP 5 Display unit 6 Local oscillator 7 Sampling frequency oscillator 8 Mixer 401 Digital signal 402 Second LPF 403 Hilbert converter 404 Third LPF 405 Decimation unit 406 BPF 407 Power calculation unit

Claims (4)

(57) [Claims] An apparatus for measuring adjacent channel leakage power from a device under test (1), such as a transmitter, comprising: an output of a local oscillator (6);
And a mixer (8) for mixing the output signal from the mixer (8) with an output from the sampling frequency oscillator (7).
A D converter (3); a Hilbert converter (403) for converting the digital data into a complex signal; a low-pass filter (404) for removing unnecessary frequency components from the Hilbert converter output signal; A band-pass filter (406) for converting the output signal of the low-pass filter into a characteristic corresponding to the communication system; a power calculator (407) for calculating the power of a complex signal from the band-pass filter; A device for measuring adjacent channel leakage power. 2. The measuring apparatus according to claim 1, further comprising: a decimation section (405) for thinning out the output data of the low-pass filter (404) at a constant rate. And a measuring device for measuring adjacent channel leakage power. 3. A measuring method for measuring adjacent channel leakage power from an object to be measured such as a transmitter, wherein a local oscillator output and a signal from the object to be measured are mixed by a mixer and changed to an intermediate frequency. Then, the mixer output signal is converted from analog to digital by an A / D converter (step 130) according to the sampling frequency oscillator output (step 130), and the digital data is converted to a complex signal by a Hilbert converter (step 110). Step 150) Unnecessary frequency components are removed from the output signal of the Hilbert transformer by a low-pass filter (Step 160), and the output signal of the low-pass filter is converted into characteristics according to the communication system by a band-pass filter (Step 1).
80) A power calculation unit performs power calculation of the complex signal from the band-pass filter (step 190), and the method for measuring adjacent channel leakage power as described above. 4. The measuring method according to claim 3, wherein the output data of the low-pass filter is thinned out by a decimation unit by a predetermined amount (step 170), and the output signal of the decimation unit is transmitted to the band-pass filter (step 180). A method for measuring adjacent channel leakage power.