JP2012204989A - Tdd receiver - Google Patents

Abstract

Deterioration of VSWR of antenna while suppressing secondary emission as compared with a method that enables application to a radio facility consisting only of a reception system circuit and that directly inputs a signal to the antenna and observes the amount of reflected power. Is detected.
A signal processing unit (DSP30) switches a TDD switch 20c to an antenna abnormality detection system circuit unit 20b at a transmission timing, and an oscillator 25 of the antenna abnormality detection system circuit unit 20b has the same frequency as the operating frequency of the antenna 10. When the signal is output, the reflected power of the abnormality detection amplifier 23 detected by the detector 26 is observed to detect an antenna abnormality.
[Selection] Figure 1

Description

  The present invention relates to a TDD receiver that performs antenna abnormality detection using a TDD (Time Division Duplex) system that realizes transmission and reception by dividing a wireless communication path on a time axis and switching between transmission and reception at high speed.

  Conventionally, this type of wireless device uses a VSWR (Voltage Standing Wave Ratio) to detect antenna anomalies. Specifically, the wireless device injects a signal to the antenna side, detects the amount of reflected wave power, and determines that the antenna is abnormal when a reflected power of a predetermined amount or more is detected.

  A radio apparatus 100 shown in FIG. 4 is a configuration example of a TDD radio apparatus including a transmission system 100a and a reception system 100b. Here, only the configuration of the FE (Front End) part of the wireless device 100 is extracted and shown. In FIG. 4, most of the power of the transmission wave transmitted through the PA (Power Amp) 105 at the transmission timing is transmitted from the ANT (110) if the VSWR of the antenna (ANT110) is good. On the other hand, when the VSWR of the ANT (110) is deteriorated, a part of the power is reflected to the ANT (110), and this reflected power is detected by the detector 106 via the directional coupler 104.

  In FIG. 4, a circuit element denoted by reference numeral 101 is a band pass filter (BPF) that passes only a signal of a predetermined band, and a circuit element denoted by reference numeral 103 is a transmission system 100a and a reception system 100b. A TDD switch (SW) for switching between and a circuit element denoted by reference numeral 107 indicates a termination resistor. Similar to the wireless device 100 shown in FIG. 4, a method of detecting an antenna abnormality by monitoring reflected power is disclosed in Patent Document 1, for example.

  Also, a method of detecting an antenna abnormality by observing RSSI (Received Signal Strength Indication) when a signal is received by each of the antennas by using a plurality of antennas is also well known. For example, the radio apparatus 200 illustrated in FIG. 5 is a configuration example of a receiving system 200a (similar to FIG. 4, only the FE unit is illustrated) including a plurality of antennas ANT # 1 (210) and ANT # 2 (220). ANT # 1 (210) and ANT # 2 (220) can be selected by the antenna switch (SW201). A detector 204 is connected to the reception system 200a, and the RSSI of the received radio wave can be detected by the detector 204. Here, radio apparatus 200 receives signals from known fixed stations by ANT # 1 (210) and ANT # 2 (220), and receives the RSSI received by each antenna (ANT # 1, ANT # 2). If there is a large difference, the smaller RSSI is determined as an antenna abnormality.

  In FIG. 5, the circuit element indicated by reference numeral 202 is a BPF, and the circuit element indicated by reference numeral 203 is a low noise amplifier (LNA) that selects and amplifies an input signal. Similar to the wireless device 200 shown in FIG. 5, for example, Patent Literature 2 discloses a method of detecting an abnormality of an antenna by RSSI when signals are received by a plurality of antennas.

JP 2004-96689 A JP 2000-1278226 A

  By the way, the method of detecting the VSWR of the ANT (110) using the transmission signal as in the wireless device 100 of FIG. 4 cannot be adopted for wireless equipment such as a base station provided only with the receiving system. Further, when a local oscillation signal is used instead of a transmission signal, a signal is emitted toward the ANT (110), so that a secondary radio wave is emitted.

  On the other hand, in the method of observing RSSI by switching a plurality of antennas as in the radio apparatus 200 shown in FIG. 5, the spatial positions of the antennas are different for each antenna 210 (ANT # 1) and 220 (ANT # 2). Therefore, even if the RSSI level fluctuates when fading occurs, it cannot be identified. For this reason, an antenna having no abnormality may be erroneously determined to be abnormal.

  The present invention has been made to solve the above-described problems, and is applicable to a method for observing the amount of reflected power by inputting a signal directly to an antenna, enabling application to a radio facility including only a receiving system. In comparison, an object of the present invention is to provide a TDD receiver that detects deterioration of the VSWR of an antenna while suppressing secondary emission.

  In order to solve the above-described problems, a TDD receiver according to the present invention includes a reception system circuit unit including a low noise amplifier that amplifies a signal received by an antenna, an anomaly detection amplifier impedance-matched to the antenna side and the output side, and A directional coupler connected to the output of the anomaly detection amplifier, an oscillator connected to the main line of the directional coupler, and generating a signal having the same frequency as the operating frequency of the antenna, and the directional coupler An anomaly detection system circuit unit including a detector connected to the sub-line side, a TDD switch for switching the reception system circuit unit and the antenna anomaly detection system circuit unit in a time-sharing manner, and transmitting the TDD switch When the signal is output from the oscillator of the antenna abnormality detection system circuit unit at the timing of, and before being detected by the detector By observing the reflected power abnormality detection amplifier and having a signal processing unit for detecting the antenna anomaly, the.

  According to the present invention, the signal processing unit switches the TDD switch to the antenna abnormality detection system circuit unit at the transmission timing, and a signal having the same frequency as the antenna operating frequency is output from the oscillator of the antenna abnormality detection system circuit unit. The antenna abnormality is detected by observing the reflected power of the abnormality detection amplifier detected by the detector. Therefore, antenna anomaly detection can be performed without using a transmission signal, so that it can be applied to a radio facility consisting only of a reception system.

  In the present invention, the signal processing unit monitors the reflection loss of the abnormality detection amplifier by calculation from the reflected power, and changes the voltage standing wave ratio of the reception frequency of the antenna according to the change amount of the reflection loss. The antenna abnormality is detected by identification. According to the present invention, since the signal processing unit detects the deterioration of the voltage standing wave ratio of the antenna using the reflection loss, the signal processing unit generates a secondary signal compared to the method of emitting the signal toward the antenna and observing the reflected power amount. Antenna anomaly detection is possible while suppressing launch.

  According to the present invention, it is possible to apply to a radio facility consisting only of a receiving system, and compared with a method of observing reflected power by directly inputting a signal to the antenna, the VSWR of the antenna is suppressed while suppressing secondary emission. It is possible to provide a TDD receiver that can detect the deterioration of the TDD.

It is a block diagram which shows the structure of the TDD receiver which concerns on embodiment of this invention. It is a figure which shows the S parameter characteristic of the abnormality detection amplifier when the VSWR of an antenna is favorable. It is a figure which shows the S parameter characteristic of the abnormality detection amplifier when the VSWR of an antenna is getting worse. It is a figure which shows the structural example of the conventional radio | wireless apparatus which employ | adopted the TDD system. It is a figure which shows the structural example of the conventional radio | wireless apparatus provided with two or more antennas.

Hereinafter, an embodiment for carrying out the present invention (hereinafter simply referred to as the present embodiment) will be described in detail with reference to the accompanying drawings.
(Configuration of the embodiment)

  FIG. 1 is a block diagram showing a configuration of a TDD receiver according to the present embodiment. In FIG. 1, a TDD receiver 1 according to the present embodiment includes an antenna (ANT10), an FE unit 20, and a signal processing unit (DSP: Digital Signal Processor) 30.

  The FE unit 20 includes a reception system circuit unit 20a, an antenna abnormality detection system circuit unit 20b, and a TDD switch (TDD-SW) 20c. The reception system circuit unit 20a and the antenna abnormality detection system circuit unit 20b are separated by a TDD-SW (20c). The TDD-SW (20c) realizes transmission / reception by switching transmission / reception in a time-sharing manner under the control of the DSP 30, but here it is used for radio equipment such as a base station equipped only with a reception system. It is used as a switch for switching the system circuit unit 20a and the antenna abnormality detection system circuit unit 20b in a time division manner.

  The reception system circuit unit 20 a includes a BPF 21 and an LNA 22. The radio wave received via the ANT (10) is selected through the BPF 21 and the LNA 22 and amplified, and supplied to a demodulator and a decoder (not shown).

  The antenna abnormality detection system circuit unit 20 b includes an abnormality detection amplifier 23, a directional coupler 24, an oscillator 25, a detector 26, and a termination resistor 27. The anomaly detection amplifier 23 is impedance matched between the antenna side and the output side via the TDD switch 20c, and the output side is connected to the main line 24a of the directional coupler 24. An oscillator 25 is further connected to the main line 24a side. The oscillator 25 generates a signal having the same frequency as the operating frequency of the ANT (10). A detector 26 and a terminating resistor 27 are connected in parallel to the sub line 24 b side of the directional coupler 24.

The DSP 30 is connected to the TDD-SW (20c) via the line 30a, and is connected to the detector 26 via the line 30b. The DSP 30 switches the connection of the TDD-SW (20c) from the reception system circuit unit 20a to the antenna abnormality detection system circuit unit 20b at the transmission timing, and operates the ANT (10) from the oscillator 25 of the antenna abnormality detection system circuit unit 20b. When a signal having the same frequency as the frequency is output, the reflected power of the abnormality detection amplifier 23 detected by the detector 26 is observed to detect an antenna abnormality. For example, the DSP 30 monitors the reflection loss of the PA 23 by calculation from the reflected power, and detects an antenna abnormality by identifying a change in the VSWR of a specific reception frequency according to the amount of change in the reflection loss.
(Operation of the embodiment)

  FIG. 2 is a diagram showing the S parameter characteristics of PA 23 when the VSWR of ANT (10) is good, and FIG. 3 is a diagram showing the S parameter characteristics of PA 23 when VSWR is deteriorated.

The S parameter is one of the network parameters used to express the characteristics of the high frequency circuit, and is a scattering matrix having S ₁₁ to S _ij as elements, and expresses the transmission / reflection characteristics. Among these elements, the return loss (S ₁₁ and S ₂₂ ) and the insertion loss (S ₂₁ and S ₁₂ ) can express the gain [dB] in the form of frequency characteristics. Using this, the horizontal axis represents the frequency [Hz] and the vertical axis represents the reflection loss and insertion loss represented by 20 log ₁₀ | S _ij | [dB] as scales and expressed as S parameter characteristics, as shown in FIG. It is a graph shown in FIG.

S ₁₁ is a reflection coefficient representing the ratio of signals reflected to the input side when a signal is input to the abnormality detection amplifier 23, and the level display of the absolute value indicates reflection loss (return loss). S ₂₁ represents the transmission characteristics of a signal that passes when a signal is input to the abnormality detection amplifier 23, and the level display of the absolute value indicates an insertion loss (insertion loss). Further, S ₁₂ is a representation of the transmission characteristics of the signal passing through the input side when the input signal from the output side of the abnormality detection amplifier 23, the level display of the absolute value indicates the reverse losses. Further, S ₂₂ is a reflection coefficient represents the ratio of the signal reflected at the output side when the input signal from the output side of the abnormality detection amplifier 23, the level display of the absolute value indicates the reflection loss.

  In the TDD receiver 1 according to the present embodiment, the DSP 30 supplies a switching signal to the TDD-SW (20c) via the line 30a at the timing of transmission, whereby the reception system is received by the TDD-SW (20c). The connection is switched from the circuit unit 20a to the antenna abnormality detection system circuit unit 20b. At this time, when a signal having the same frequency as the operating frequency of the antenna 10 is output from the oscillator 25 of the antenna abnormality detection system circuit unit 20b, the DSP 30 detects an abnormality detected by the detector 26 via the directional coupler 24. The reflected power from the detection amplifier 23 is acquired via the line 30b.

For this reason, the DSP (30) switches the TDD-SW (20c) to the antenna abnormality detection system circuit unit 20b at the transmission timing, and sets the operating frequency of the antenna from the oscillator 25 toward the abnormality detection amplifier 23 connected in the reverse direction. Control to output signals with the same center frequency. At this time, if it is the abnormality detection amplifier 23 is impedance matched, S ₂₂ characteristics of the anomaly detection amplifier 23 is as shown in FIG. That is, the output-side reflection loss 20 log ₁₀ of the abnormality detection amplifier 23 receiving frequency is at _{f o [Hz] | S 22} | is in the vicinity of -70 [dB], therefore the situation where the reflected power does not almost appear. For this reason, the signal processing unit 30 can determine that the VSWR of the antenna 10 is in a good state.

On the other hand, if there is an antenna abnormal, i.e., when the VSWR of ANT (10) has deteriorated, the impedance matching of the abnormality detection amplifier 23 is lost, _{S 22} characteristics of the anomaly detection amplifier 23, as shown in FIG. 3 become. That is, the reflection loss of the abnormality detection amplifier 23 at the reception frequency f ₀ [Hz] increases from the −70 [dB] state where the impedance is matched to the vicinity of −10 [dB]. For this reason, the DSP 30 can determine that the VSWR of the ANT (10) has deteriorated.

Therefore, the DSP 30 monitors the reflection loss of the abnormality detection amplifier 23 by calculation from the reflected power detected and taken in by the detector 26, and changes the VSWR of the reception frequency of the ANT (10) according to the amount of change of the reflection loss. By identifying, it is possible to detect an antenna abnormality. However, compared this time, the power of the oscillator 25 is directed to the ANT (10) side, the amount of power by _{S 12} characteristics of the anomaly detection amplifier 23 for is suppressed, and when injecting the signal directly to the ANT (10) Thus, secondary firing can be suppressed.
(Effect of embodiment)

  As described above, according to the TDD receiver 1 according to the present embodiment, the DSP 30 switches the TDD-SW (20c) to the antenna abnormality detection system circuit unit 20b at the transmission timing, and the antenna abnormality detection system circuit unit 20b. When a signal having the same frequency as the operating frequency of the ANT (10) is output from the oscillator 25, the reflected power of the anomaly detection amplifier 23 detected by the detector 24 is observed via the directional coupler 24 to detect an antenna abnormality. Detect. Therefore, the antenna abnormality detection can be performed without using the transmission signal, so that it can be applied to a radio facility composed only of the reception system.

Further, according to the TDD receiver 1 according to this embodiment, in order to detect deterioration of VSWR of utilizing _{S 22} characteristics of the high frequency circuit ANT (10), by directly inputting the signal to the ANT (10) thereof Compared to the conventional method of observing the amount of reflected power, the VSWR deterioration of ANT (10) can be detected while suppressing the secondary emission.

  According to the TDD receiver 1 according to the present embodiment, the DSP 30 monitors the reflection loss of the abnormality detection amplifier 23 by calculation, and changes the VSWR of the reception frequency of the ANT (10) according to the change amount of the reflection loss. Although the antenna abnormality is detected by identification, the antenna abnormality may be detected by comparing the reflected power output from the detector 26 with a threshold by an analog circuit.

  Further, when the TDD receiver 1 according to the present embodiment adopts a direct conversion system that directly converts a received signal into a baseband signal, a signal of a local oscillator (local oscillation frequency) that is a component of the reception system circuit unit 20a. ) Can be used as it is as the oscillator 25 of the antenna abnormality detection system circuit unit 20b, so that the cost can be suppressed.

  As mentioned above, although this embodiment was described, it cannot be overemphasized that the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. Further, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  1 ·· TDD receiver, 20 · · FE unit, 20a · · reception circuit unit, 20b · · antenna (ANT), 20c · · TDD switch (TDD-SW), 21 · · band pass filter (BPF), 22 .. Low noise amplifier (LNA), 23 .. Anomaly detection amplifier, 24 .. Directional coupler, 25 .. Oscillator, 26 .. Detector, 27 .. Terminating resistor, 30. DSP)

Claims (2)

A receiving circuit unit including a low noise amplifier for amplifying a signal received by an antenna;
An anomaly detection amplifier impedance-matched on the antenna side and the output side, a directional coupler connected to the output of the anomaly detection amplifier, connected to the main line of the directional coupler, and the same as the operating frequency of the antenna An antenna abnormality detection system circuit unit including an oscillator that generates a signal of a frequency, and a detector connected to a sub-line side of the directional coupler;
A TDD switch for switching the reception system circuit unit and the antenna abnormality detection system circuit unit in a time-sharing manner;
When the TDD switch is switched to the antenna abnormality detection system circuit unit at the transmission timing and the signal is output from the oscillator of the antenna abnormality detection system circuit unit, the reflected power of the abnormality detection amplifier detected by the detector A signal processing unit that detects antenna abnormalities by observing
A TDD receiver comprising: The signal processing unit
Monitoring the reflection loss of the abnormality detection amplifier by calculation from the reflected power, and detecting the antenna abnormality by identifying the change in the voltage standing wave ratio of the reception frequency of the antenna according to the amount of change in the reflection loss. The TDD receiver according to claim 1.

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