JP5790886B2 - Wireless transmission device, VSWR measurement device, and VSWR measurement method - Google Patents

Description

  The present invention relates to a wireless transmission device, a VSWR measurement device, and a VSWR measurement method, and more particularly to measurement of a VSWR.

  In LTE (Long Term Evolution), which is a mobile phone communication standard, W-CDMA (Wideband Code Division Multiple Access) and LTE share antennas to improve workability during installation and reduce operating costs. System configuration such as Remote Radio Equipment). When the base station wireless transmission device of the own system and the base station wireless transmission device of another system, which are composed of an OFDM (Orthogonal Frequency Division Multiplexing) system such as LTE, are combined with a shared antenna or the like, the wireless transmission device of the other system Is input to the wireless transmission device of its own system and becomes an interference wave. Even in such an environment, it is important to accurately measure VSWR (Voltage Standing Wave Ratio), reflect the result in the system, and control wireless communication.

  FIG. 5 shows a VSWR measuring apparatus and method according to the related art. The baseband signal generator 2 receives the data signal generated by the MAC1 and converts it into an I / Q axis signal as a modulated baseband signal. The modulator 3 modulates the I / Q axis signal into an RF band modulation downlink signal based on the oscillation signal from the local oscillator 40. The high-power amplifier 4 increases the RF band modulation downlink signal to a predetermined transmission power and outputs it to the filter 5. The filter 5 reduces transmission spurious of the RF band modulation downlink signal. The RF band modulated downlink signal is radiated into space by the antenna 7. At that time, in order to measure the VSWR when the antenna 7 is expected and to confirm that the spatial radiation from the antenna is performed without any problem, a VSWR measurement circuit is provided in the front stage of the antenna 7. Here, a directional coupler 6 is inserted in front of the antenna 7 in order to detect a traveling wave and a reflected wave for VSWR measurement.

  The directional coupler 6 outputs a traveling wave to the traveling wave detector 8. The directional coupler 6 outputs the reflected wave to the reflected wave detector 9. The traveling wave detector 8 detects the detection voltage value of the traveling wave. The reflected wave detector 8 detects the detection voltage value of the reflected wave. The difference detector 10 detects the difference between the traveling wave detection voltage and the reflected wave detection voltage. Based on this difference detection voltage, the VSWR calculator 11 calculates the VSWR, and the VSWR averager 12 smoothes the VSWR. In the first related technique, the VSWR smoothed by the VSWR averager 12 is output and displayed as it is as the final report value. However, a large error occurs in the VSWR measurement in the environment described later.

  Next, I will explain the environmental concerns. FIG. 7 shows a case where the base station wireless transmitter of the own system and the base station wireless transmitter of another system are coupled to each other using an OFDM scheme such as LTE by a shared antenna or the like. In this case, an interference wave from the wireless transmission device of another system is input to the wireless transmission device of the own system.

  FIG. 8 shows a time waveform of the LTE downlink signal. In the test models E-TM1.1 and E-TM2, signals exist densely on the time axis. On the other hand, the shortest broadcast information (Broadcast information) in one frame (= 10 subframes and 10 msec) in the control channel signal that is the sparsest signal in the actual operation signal (no terminal link) Then, the reference signal that becomes a training signal on the terminal side with a shorter duration is sparsely present on the time axis.

  Therefore, a problem when VSWR measurement is performed under various environments will be described using the configuration example of the VSWR measurement apparatus shown in FIG. As shown in FIG. 9, in the case of a dense test signal, the signal level fluctuates, but is within the dynamic range of the detector, so the VSWR measurement is always the correct value (in this case 1.5). Indicates.

  As shown in FIG. 10, in the case of a sparse downlink signal, the signal repeats on and off frequently and falls below the dynamic range of the detector in most of the range, so the VSWR measurement value is a bad value. turn into. On the other hand, since the signal density is high during the period in which the notification information is output, the VSWR is a correct measurement value.

  Furthermore, as shown in FIG. 11, when an interference wave from another system is added to a sparse downlink signal during operation, the error is greatly increased because the interference wave is mistaken as a reflected wave. Expanding. The worst VSWR measurement value is obtained depending on the interference wave level. However, since the signal density is high during the period in which the notification information is output, the VSWR measurement value is correct.

  As described above, in a real environment, when the signal density is sparse and there is a backflow of disturbing waves from another system coupled by a shared antenna, the VSWR measurement value is considerably deteriorated. In addition, there is a concern that the VSWR report when the antenna is expected is misrecognized as a total reflection aspect, so that an erroneous alarm or the like is activated in the monitoring station and the own system stops.

Examples of the prior art document that discloses the configuration of the VSWR measurement circuit according to the related art include the following. These do not describe a solution for VSWR measurement errors caused by external interference wave / jamming wave backflow.
VSWR detection circuit and VSWR detection method (Patent Document 1, FIG. 1)
VSWR measurement circuit (Patent Document 2, FIG. 1)
VSWR monitor circuit (Patent Document 3, FIG. 1)
Antenna port monitoring system and method (Patent Document 4, FIG. 1)

In addition, as a developed type of the above-described related technology, the following is cited as a prior art document in which circuit contrivance or consideration is made regarding a VSWR measurement error caused by an external interference wave / jamming wave backflow.
Antenna monitoring device (Patent Document 5, FIG. 1 and FIG. 2)
・ Standing wave ratio measuring device (Patent Document 6)
-Voltage standing wave ratio measuring device (Patent Document 7)

  A device related to the above three cases is disclosed in FIG. Here, a directional coupler inserted to detect a traveling wave and a reflected wave for VSWR measurement is provided between a filter (bandpass filter) connected to an antenna and a wireless transmission device. . As a result, anti-band attenuation by a filter is expected. In addition, bandpass filters are also inserted between the traveling wave detector and the reflected wave detector branched from the directional coupler to sufficiently suppress out-of-band interference and interference before detection. It corresponds with.

  Moreover, the other structural example put together by said 3 cases is shown by FIG. Here, down-converters are provided in the traveling wave path and the reflected wave path branched by the directional coupler, and the local oscillator frequency is changed. As a result, the baseband or IF frequency after the converter is passed through a narrower band filter while changing the target passband, so that the external out-of-band interference wave / jamming wave is attenuated more steeply. And the error of the VSWR measurement value by these interference waves and interference waves is reduced.

  However, the configuration shown in the above three prior arts is effective when the frequency band of the external interference wave / jamming wave is far from the desired transmission band. On the other hand, when the transmission band of the own system and the interference band from another system are close to each other or overlap in the band, there arises a problem that the frequency selectivity by the filter cannot be expected. In order to obtain the effect, a steep filter characteristic is required, which causes a problem in that the design difficulty is greatly increased, leading to an increase in the shape of the apparatus and the price. In the case of a configuration in which a fixed-band filter is inserted into the detection system, there is a problem that frequency flexibility is lost.

  Patent Document 8 discloses a method for confirming the VSWR normality of the receiving antenna instead of confirming the VSWR normality of the transmitting antenna. In addition, in order to measure the VSWR of the receiving antenna, a separate and dedicated PN (Pseudorandom Noise) spread signal generator and demodulator are required in combination with the main signal receiving system. is there. Furthermore, there is a problem in that a PN spread signal different from the operation transmission signal is radiated as unnecessary radiation from the reception antenna at the time of VSWR measurement. On the other hand, when there is a backflow of interference waves from the outside when the antenna is shared etc., the denominator I and I ′ are different measurement times in the VSWR derivation process of VSWR = S1 / (N + I ′) − S2 / (N + I). Since the voltage is applied, the VSWR error is enlarged. Further, when the denominator becomes large at larger I or I ′, C / N (Carrier to Noise Ratio) cannot be secured and PN demodulation may not be possible.

  In Patent Document 9, in the antenna (ANT) VSWR measurement, when the electrical length between the antenna (ANT) load and the coupling port (CPL) is different, and the traveling wave component leaks to the reflected wave port due to poor CPL directivity. Then, an error occurs as a combined vector of reflected waves, and a VSWR error occurs. Then, by inserting a phase shifter between the antenna and the coupling port and changing the electrical length, the traveling wave leakage component is removed from the calculation of the maximum reflected wave vector and the minimum reflected vector, and the VSWR accuracy is improved. Therefore, the example shown in Patent Document 9 provides an improvement in VSWR accuracy in the absence of an external interference wave, and does not show consideration for the sparse density of the traveling wave and the external interference wave.

  In Patent Document 10, VSWR measurement is performed by installing a traveling wave / reflected wave acquisition coupler for an antenna (ANT) VSWR monitor in an antenna front end under a configuration limited to a time division duplex (TDD) system. The purpose is to avoid the impact caused by the increase in transmission loss. Furthermore, an object is to avoid an increase in transmission power consumption due to coupler loss. In order to achieve such an object, Patent Document 10 utilizes a transmission / reception coupling circulator in the TDD antenna portion and devise them by routing.

  During VSWR measurement (measured during reception), the traveling wave monitors the PA input, and the reflected wave from the antenna due to the traveling wave bypassing the PA branches from the middle of the receiving unit and is monitored before proceeding. This is a mechanism for calculating the VSWR from the difference between the wave and the reflected wave. Patent Document 10 does not show that the interference wave component is removed from the reflected wave for VSWR measurement to improve the VSWR accuracy. The configuration described in Patent Document 10 is a configuration in which the VSWR measurement circuit itself is limited to TDD, and has a problem that it cannot be used in a frequency division duplex (FDD) system.

  In Patent Document 11, the OFDM system receiving side (especially digital broadcasting reception) in which a CP (Cyclic Prefix) copy is arranged in the GI (Guard Interval) section is used to identify the effective FFT length for GI removal and FFT implementation with low power consumption. It is intended to be performed easily. In Patent Document 11, after detecting autocorrelation with an OFDM symbol delay wave, a spectrum enhancement filter that passes only harmonics of the symbol frequency is mounted for noise removal, and an effective FFT length is identified. And in patent document 11, it raises as a problem which should solve the power consumption increase by these functions. Further, Patent Document 11 shows that the effective FFT length is determined by the period of the autocorrelation peak by taking the delay / autocorrelation focusing on the periodicity of CP / GI.

Japanese Patent No. 4379034 Japanese Patent Laid-Open No. 03-051772 JP 2004-286632 A Japanese Patent No. 4062023 Japanese Patent Laid-Open No. 04-357471 Japanese Patent No. 3271277 Japanese Patent No. 2697342 JP2011-010185A JP 2005-0117138 A JP 2011-114417 A JP 2005-0664615 A

As described above, there is a problem that the VSWR measurement value is deteriorated depending on the transmission state (transparency of transmission signal density).
The present invention has been made to solve such a problem, and an object of the present invention is to provide a wireless transmission device, a VSWR measurement device, and a VSWR measurement method that can accurately determine the reliability of a VSWR measurement value.

The wireless transmission device according to one aspect includes a VSWR measurement unit that measures VSWR, and a VSWR determination unit that determines reliability of a measurement value of the VSWR measured by the VSWR measurement unit, wherein the VSWR determination unit includes:
Reflected wave baseband conversion means for converting the reflected wave into a baseband signal;
About the baseband signal converted by the reflected wave baseband conversion means, autocorrelation means for taking the autocorrelation between the delayed wave and the main wave added with a predetermined delay amount;
Determination means for determining that the possibility of estimating the desired reflected wave is high if the same value included in one symbol is detected when the autocorrelation means is equal to or greater than a predetermined value.

A VSWR determination apparatus according to one aspect is a VSWR determination apparatus that determines the reliability of a measured value of VSWR,
Reflected wave baseband conversion means for converting the reflected wave into a baseband signal;
About the baseband signal converted by the reflected wave baseband conversion means, autocorrelation means for taking the autocorrelation between the delayed wave and the main wave added with a predetermined delay amount;
Determination means for determining that the possibility of estimating the desired reflected wave is high if the same value included in one symbol is detected when the autocorrelation means is equal to or greater than a predetermined value.

A VSWR determination method according to one aspect is a VSWR determination method for determining reliability of a measured value of VSWR,
Converting the reflected wave into a baseband signal;
About the converted baseband signal, taking the autocorrelation between the delayed wave with a predetermined delay amount and the main wave,
And determining that the possibility of estimating the desired reflected wave is high when the same value included in one symbol is detected when the autocorrelation is equal to or greater than a predetermined value.

  According to the present invention, it is possible to provide a wireless transmission device, a VSWR measurement device, and a VSWR measurement method that can accurately determine the reliability of a measured value of VSWR.

It is a figure of the radio transmitter concerning an embodiment of the invention. It is a figure of the radio transmitter concerning an embodiment of the invention. It is a figure of the radio transmitter concerning an embodiment of the invention. It is a figure of an OFDM symbol format. It is a figure of the internal structure of an autocorrelator. It is a figure of the correlation value versus CIR estimation characteristic previously stored in the correlation value versus CIR estimator. It is a figure of the VSWR measuring apparatus and method concerning a prior art. It is a block diagram of the wireless transmission device concerning this invention. It is a figure in case the base station type | system | group radio | wireless transmitter of an own system and the base station type | system | group radio | wireless transmitter of another system are couple | bonded with a shared antenna. It is a figure of the time waveform of a LTE downlink signal. It is a figure in the case of a test signal with a density by VSWR measurement. It is a figure in the case of the sparse downlink signal at the time of communication operation by VSWR measurement. It is a figure at the time of the interference wave from other systems adding back flow to the sparse downlink signal at the time of operation by VSWR measurement.

Embodiment 1
Embodiments of the present invention will be described below with reference to the drawings. 1A, 1B, and 1C show the configuration of a wireless transmission device according to the present invention. FIG. 6 is a schematic diagram showing the VSWR determination unit 200 inside the wireless transmission device. The VSWR determination unit 200 includes a traveling wave analysis unit 103, a reflected wave analysis unit 101, a switch 22, an interference wave / reflected wave adjustment unit 102, and is connected to the VSWR measurement unit 104.
The baseband signal generator 2 receives the data signal generated by the MAC1 and converts it into an I / Q axis signal as a modulated baseband signal.

  The modulator 3 modulates the I / Q axis signal into an RF band modulation downlink signal based on the oscillation signal from the local oscillator 40. The high-power amplifier 4 increases the RF band modulation downlink signal to a predetermined transmission power and outputs it to the filter 5. The filter 5 reduces transmission spurious of the RF band modulation downlink signal. The RF band modulated downlink signal is radiated into space by the antenna 7. At that time, in order to measure the VSWR when the antenna 7 is expected and to confirm that the spatial radiation from the antenna is performed without any problem, a VSWR measurement circuit is provided in the front stage of the antenna 7. Here, a directional coupler 6 is inserted in front of the antenna 7 in order to detect a traveling wave and a reflected wave for VSWR measurement.

The directional coupler 6 outputs a traveling wave to the traveling wave analysis unit 103 as shown in FIG. 1C. The traveling wave analysis unit 103 includes a traveling wave down converter 13, an ADC (Analog / Digital Converter) 15, and an averaging circuit 17.
The traveling wave down converter 13 converts the traveling wave into a baseband signal. An ADC (Analog / Digital Converter) 15 is a baseband quantization unit that quantizes a traveling wave converted into a baseband signal. The averaging circuit 17 converts the traveling wave into RMS (Root Mean Square) and outputs a traveling wave RMS value.
Moreover, the directional coupler 6 outputs a reflected wave to the reflected wave analysis part 101 as FIG. 1B shows. The reflected wave analysis unit 101 includes a reflected wave down converter 14, an ADC 16, an averaging circuit 18, an autocorrelator 19, and a determiner 20.

The reflected wave down converter 14 converts the reflected wave into a baseband signal. The ADC 16 is a baseband quantizing unit that quantizes the reflected wave converted into the baseband signal. The averaging circuit 18 converts the reflected wave into RMS and outputs the reflected wave RMS value. The switch 22 outputs the reflected wave RMS value output from the averaging circuit 18 to the interference wave removal / reflected wave average level corrector 23 included in the interference wave / reflected wave adjustment unit 102 according to the output of the determiner 20. Select whether to output. The autocorrelator 19, the determiner 20, and the correlation value pair CIR estimator 21 will be described later.
The difference detector 10 shown in FIG. 1C detects the difference between the traveling wave RMS value and the reflected wave RMS value (the level after correction by the interference wave removal / reflected wave average level corrector 23). The VSWR calculator 11 calculates the VSWR based on the detected difference and reports it to the outside as a VSWR output display.

Next, a method for discriminating the reflected wave component of the desired OFDM transmission signal from the reflected wave signal and the interference wave / interfering wave component from the outside and estimating only the desired OFDM reflected wave level will be described.
The reflected wave digital baseband signal converted into a digital signal by the ADC 16 is branched and input to the autocorrelator 19 and the averaging circuit 18.
The autocorrelator 19 pays attention to the GI copy in each symbol included in the OFDM signal of FIG. The internal configuration of the autocorrelator 19 is shown in FIG. The autocorrelator 19 includes a delay unit 24 and an autocorrelation calculator 25 as shown in the figure. The autocorrelator 19 generates a delayed wave by being delayed by the delay unit 24. The autocorrelation calculator 25 calculates the autocorrelation between the delayed wave and the main wave by calculation. The determiner 20 determines whether the autocorrelation value (especially its peak value) is equal to or greater than a predetermined threshold. If the autocorrelation value is equal to or greater than the threshold, the determiner 20 determines that the desired OFDM reflected wave can be estimated sufficiently. On the other hand, if the autocorrelation value is less than the threshold value, it is determined that the desired OFDM reflected wave cannot be estimated.

If the determiner 20 can estimate the desired OFDM reflected wave and can extract it, the switch (SW) 22 is switched to connect to the interference wave removal / reflected wave average level corrector 23. In this case, the reflected wave RMS value converted to RMS by the averaging circuit 18 is output to the interference wave removal / reflected wave average level corrector 23.
Note that the delay amount control is performed from the determiner 20 to the delay device 24, and it is determined by the determiner 20 that the autocorrelation peak has exceeded the determination threshold value, and the delay amount of the delay device 24 is held during the time exceeding the threshold value. Control to do. The autocorrelation peak value in the autocorrelator 19 that has passed through the determiner 20 is input to the correlation value pair CIR estimator 21. The correlation value pair CIR estimator 21 estimates the CIR based on the correlation value pair CIR estimation characteristic (see FIG. 4) of FIG. 4 set in advance.

The correlation value pair CIR estimator 21 outputs the estimated CIR estimated value to the interference wave removal / reflected wave average level corrector 23.
The interference wave removal / reflected wave average level corrector 23 finally obtains the reflected wave level of the desired transmission signal according to the following equation (1) based on the reflected wave level from the averaging circuit 18 and the CIR estimated value.
Reflected wave level of desired transmission signal [dBm] = Reflected wave level RMS value [dBm]-10Log (1 + 10 ^ (-CIR [dB] / 10)) (1)
The obtained reflected wave level of the desired transmission signal is input to the difference detector 10 so as to take a difference from the traveling wave RMS value converted into the RMS by the averaging circuit 17. Based on this difference detection level, the VSWR calculator 11 calculates the VSWR, and after subtracting the external system interference wave / interference wave level from the outside, the true VSWR output display conforming to the transmission signal is reported to the outside. be able to.

  When the correlation peak value of the autocorrelator 19 is determined to be equal to or less than the threshold value by the determiner 20, there is a concern that the interference wave from the other system from the outside is too strong, and it is expected that the VSWR report cannot be accurately performed. Therefore, SW22 is switched to the VSWR invalid display direction, and the VSWR report to the outside is invalidated.

  As described above, according to the configuration of the present embodiment, even if there is an interference wave from the base station radio transmitter of another system coupled by the shared antenna, the interference wave / interference included in the reflected wave is present. A sufficient VSWR measurement accuracy can be obtained by estimating the wave level by autocorrelation focusing on the GI copy for each OFDM symbol and removing it by calculation. Accordingly, a VSWR alarm or the like due to a malfunction does not occur, and a problem occurs in the antenna itself or connection, and the alarm is activated only when the VSWR deteriorates.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. In the above embodiment, LTE has been described. However, for example, the present invention may be applied to a communication system related to communication standards (e.g. LTE-Advanced, IMT-Advanced, WiMAX2) of the fourth generation or higher.

  Although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2012-211229 for which it applied on September 25, 2012, and takes in those the indications of all here.

  The present invention can be used in the field of wireless communication.

1 MAC
2 Baseband generator 3 Modulator 4 High power amplifier 5 Filter 6 Directional coupler 7 Antenna 8 Traveling wave detector 9 Reflected wave detector 10 Difference detector 11 VSWR calculator 12 VSWR averager 13 Traveling wave downconverter 14 Reflected wave down converter 15 A / D converter 16 A / D converter 17 Averaging circuit 18 Averaging circuit 19 Autocorrelator 20 Determinator 21 Correlation value vs. CIR estimator 22 Switch 23 Interference wave removal, reflected wave average level corrector 24 Delay unit 25 Autocorrelation calculator 40 Local oscillator 101 Reflected wave analysis unit 102 Interference wave / reflected wave adjustment unit 103 Traveling wave analysis unit 104 VSWR measurement unit 200 VSWR determination unit

Claims (9)

VSWR measuring means for measuring VSWR;
VSWR determination means for determining the reliability of the measured value of VSWR measured by the VSWR measurement means;
With
The VSWR determination means includes
Reflected wave baseband conversion means for converting the reflected wave into a baseband signal;
About the baseband signal converted by the reflected wave baseband conversion means, autocorrelation means for taking the autocorrelation between the delayed wave and the main wave added with a predetermined delay amount;
A radio transmission apparatus comprising: a determination unit that determines that the possibility of estimating a desired reflected wave is high if the same value included in one symbol is detected when the autocorrelation unit is equal to or greater than a predetermined value.   The radio transmission apparatus according to claim 1, wherein the autocorrelation unit adjusts a delay amount so that a GI copy within each OFDM symbol can be correlated with a GI. It said determining means, if it is not judged to have a high estimated probability of desired reflected wave, the radio transmitting apparatus according to claim 1 or 2, wherein limiting the output of the VSWR.   The wireless transmission device according to any one of claims 1 to 3, wherein the determination unit executes control to hold the delay amount when it is determined that the autocorrelation peak is equal to or greater than a predetermined value.   5. The radio transmission apparatus according to claim 1, further comprising: a correlation value pair CIR estimation unit that estimates a CIR based on an autocorrelation peak value in the autocorrelation unit.   The wireless transmission device according to claim 1, wherein the wireless transmission device shares an antenna with a base station wireless transmission device of a different system.   7. The radio transmission apparatus according to claim 1, wherein an LTE OFDM base station radio transmission apparatus and another base station radio transmission apparatus are combined to share an antenna. The wireless transmission device described in 1. A VSWR determination device for determining reliability of a measured value of VSWR,
Reflected wave baseband conversion means for converting the reflected wave into a baseband signal;
About the baseband signal converted by the reflected wave baseband conversion means, autocorrelation means for taking the autocorrelation between the delayed wave and the main wave added with a predetermined delay amount;
A VSWR determination apparatus comprising: determination means for determining that the possibility of estimating a desired reflected wave is high when the same value included in one symbol is detected when the autocorrelation is equal to or greater than a predetermined value by the autocorrelation means. A VSWR determination method for determining reliability of a measured value of VSWR,
Converting the reflected wave into a baseband signal;
About the converted baseband signal, taking the autocorrelation between the delayed wave with a predetermined delay amount and the main wave,
A step of determining that the possibility of estimating the desired reflected wave is high when the same value included in one symbol is detected when the autocorrelation is equal to or greater than a predetermined value.

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