JP2007116621A - Wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication apparatus which obtains high-performance AGC at a low cost with a simple constitution and ensures stable receiving condition under various environments. <P>SOLUTION: An apparatus for UWB communication using a pulse signal, which is otherwise very difficult to attain AGC, comprises a correlator 130 that outputs a correlation signal by despreading the output signal of a variable gain amplifier, a voltage comparator 140 that outputs a pulse signal by comparing the voltage of the correlation signal with a predetermined threshold voltage, and a signal processing unit 150 that outputs digital data based on the pulse signal and feedbacks the threshold voltage to the voltage comparator. The signal processing unit 150 controls to decrease the threshold voltage when the pulse signal is not detected, and controls to increase the threshold voltage when erroneous detection of the pulse signal occurs. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus that performs wireless communication using a pulse wave between communication apparatuses, and more particularly to a wireless communication apparatus that performs wireless communication using a UWB (Ultra_Wide_Band) method between communication apparatuses.

In wireless communication, an electromagnetic wave transmitted from an antenna has a loss due to spatial propagation before being received. This spatial propagation loss is expressed as (4πd / λ) ² when the distance is d and the wavelength is λ. However, in an actual usage environment, the complex shape and position of a mountain, building, ceiling, wall, etc. It takes various values depending on the relationship and material. Moreover, it is constantly changing due to changes in weather, movement of surrounding cars and people, movement of communication equipment itself, and the like. In order to maintain a stable communication state, the gain of a low noise amplifier (Low Noise Amplifier: LNA) is changed in accordance with the received electric field level, and the AGC (Automatic_Gain_control) that makes the input level of the A / D conversion circuit and demodulation circuit constant. It is necessary to use a circuit (for example, refer to Patent Document 1).

  FIG. 8 shows a general wireless communication apparatus. The wireless communication apparatus 300 performs frequency mixing of an antenna 310 that receives a signal, a variable gain amplifier 320 that variably amplifies the gain of the received signal, and a frequency generated by the local oscillator 330 and an output signal of the variable gain amplifier 320. Mixer 340, IF amplifier 350 that amplifies the output signal from mixer 340, signal processing unit 360 that performs A / D conversion on the output signal of IF amplifier 350, and detection that detects the output signal of IF amplifier 350 And a feedback circuit 380 that feeds back a gain control voltage to the variable gain amplifier 320.

  In such a general wireless communication apparatus 300, a continuous wave (Continuos_wave) is used for a carrier wave, and the frequency band after modulation is also a relatively narrow band. By extracting with a filter and detecting with a diode or the like, the received electric field level can be detected with high accuracy. The AGC circuit is realized by feeding back the value to the variable gain amplifier 320.

JP-A-11-98055

  However, in the UWB system that uses extremely short pulses of 1 nanosecond or less (several hundreds of picoseconds) and modulates the position of the pulse or the amplitude of the pulse according to the transmission data, the detection of the received electric field level by the conventional system is very difficult. The reason is that there is no carrier wave and power is dispersed over time, and the detection error of the received electric field level due to the presence and arrangement of transmission data increases. In addition, the FCC (Federal_Communication_commission) spectrum mask specification is very low at -41.3 dBm / MHz or less, and the frequency band is 3.1 GHz to 10.6 GHz, so it is very wide. Being easily affected by the communication system is a factor that increases the detection error.

  The present invention has been made in view of the above-described problems of conventional wireless communication apparatuses, and an object of the present invention is to provide a simple configuration in a UWB communication apparatus using pulses that are very difficult to realize AGC. Therefore, it is possible to provide a new and improved wireless communication apparatus that can realize an inexpensive and high-performance AGC and can ensure a stable reception state in various environments.

  In order to solve the above problems, according to a first aspect of the present invention, a wireless communication device is provided. A radio communication apparatus according to the present invention includes a gain amplifier that amplifies a gain of a received signal, a correlator that despreads the output signal of the gain amplifier and outputs a correlation signal, and compares the correlation signal with a predetermined threshold voltage. A voltage comparator that outputs a pulse signal; and a signal processing unit that outputs digital data based on the pulse signal and that feeds back a threshold voltage to the voltage comparator, the signal processing unit comprising: The threshold voltage is changed when an abnormal communication state is detected based on the pulse signal.

  According to such a wireless communication device, feedback control is performed so as to change the threshold voltage of the voltage comparator when an abnormality in the communication state is detected based on the pulse signal. For example, the threshold voltage can be controlled to be lowered when the pulse signal is not detected (missed), and the threshold voltage is raised when the pulse signal is erroneously detected. Can be controlled. As a result, even if an abnormality occurs in the communication state, digital data can be accurately output from the pulse signal. In this way, in a UWB communication device using pulses that are very difficult to realize AGC, an inexpensive and high-performance AGC can be realized with a simple configuration, and a stable reception state in various environments. It can be secured.

  In the wireless communication apparatus, the correlator may adjust and select the spreading code so that the autocorrelation side lobe or the point with poor cross-correlation is between the autocorrelation value and the autocorrelation value. According to such a configuration, it is possible to cause undetected (missing) of a pulse signal or erroneous detection of a pulse signal to occur as a pilot signal in the middle of a normal pulse signal. In this way, a normal pulse signal and an abnormal signal can be clearly distinguished.

  The voltage comparator may digitally integrate the correlation signal. In UWB communication, power is temporally dispersed, so that the error increases when the correlation signal is integrated in an analog manner. Therefore, it is possible to reduce the error by digitally integrating the correlation signal.

  The signal processing unit can also feed back a gain amplification voltage to the gain amplifier based on the pulse signal. By controlling not only the threshold voltage but also the gain of the amplifier, it is possible to cope with a UWB communication system that needs to ensure a wider dynamic range.

  As described above, according to the present invention, an inexpensive and high-performance AGC can be realized with a simple configuration in a UWB communication apparatus using a pulse that is very difficult to realize AGC. Thus, a stable reception state can be ensured. In this way, in a radio receiver using UWB (Ultra_Wide_Band) technology, AGC (Automatic_Gain_Control) for maintaining a stable communication state against a constantly changing spatial propagation loss can be performed with high accuracy and simplicity. The basic performance of the UWB receiver can be greatly improved.

  Exemplary embodiments of a wireless communication apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 is an explanatory diagram illustrating a configuration of a wireless communication apparatus according to the first embodiment.

  As shown in FIG. 1, the radio communication apparatus 100 according to the present embodiment includes an antenna 100 that receives a signal, a variable gain amplifier 120 that variably amplifies the gain of the received signal, and a correlation that outputs a correlation signal from the received signal. A comparator 130, a voltage comparator (A / D converter) 140 that compares the correlation signal with a predetermined threshold voltage and outputs a pulse signal, and a signal processor 150 that processes the pulse signal and outputs data. It is prepared for. In FIG. 1, the receiving side, which is a characteristic part of the present embodiment, is mainly shown, and it goes without saying that not all the components of the wireless communication device 100 are shown.

  The correlator 130, the voltage converter 140, and the signal processing unit 150, which are characteristic components of this embodiment, will be described in further detail.

(Correlator 130)
In this embodiment, as will be described later, it is necessary to perform control so that erroneous detection occurs in the vicinity of the middle between the autocorrelation value and the next autocorrelation value even if an erroneous detection of the received signal occurs. This is because, depending on the timing at which the erroneous detection occurs, it becomes impossible for the signal processing unit 150 in the subsequent stage to determine whether or not the erroneous detection has occurred. Therefore, in the present embodiment, the correlator 130 adjusts and selects the spread code so that the autocorrelation side lobe or the point with poor cross-correlation is in the vicinity of the middle of the autocorrelation value and the autocorrelation value, so Is controlled to occur in the middle. The advantages of performing such control will be further described later.

(Voltage converter 140)
In the present embodiment, the detection method of the voltage converter 140 has a remarkable feature. FIG. 2 is an explanatory diagram showing the difference between the conventional general detection method and the detection method according to the present embodiment as an image.

  In the general wireless communication system using the carrier wave shown in FIG. 2A, since a current always flows, the received power can be integrated with high accuracy by a simple analog detection circuit. On the other hand, in the UWB communication shown in FIG. 2B, the power is temporally dispersed, so that the error increases when integrated in an analog manner. Therefore, in this embodiment, the voltage converter 140 detects the received power by digitally integrating the output after conversion from analog to digital.

(Signal processing unit 150)
The signal processing unit 150 changes the threshold voltage when detecting an abnormality in the communication state based on the pulse signal. That is, the signal processing unit 150 feeds back the threshold voltage to the voltage comparator 140 when an abnormality in the communication state is detected.

  Next, output signals of the above components will be described.

(1) Stable communication state (Fig. 3)
In FIG. 1, symbols (a), (b), and (c) indicate output signals of the variable gain amplifier 120, the correlator 130, and the voltage comparator 140, respectively. FIG. 3 is an explanatory diagram showing an example of output signals at the points (a), (b), and (c) shown in FIG. 1, and particularly shows the case of a stable communication state.

  As shown in FIG. 3, in a stable communication state, the received signal (a) received by the antenna 110 is variably amplified by the variable gain amplifier 120 and then input to the correlator 130, and the correlation output (b). Is obtained. The correlation output (b) is input to the voltage comparator 140, and only a desired bit is converted from an analog signal to a digital signal with an optimum threshold voltage without excess or deficiency.

  In FIG. 3, a threshold voltage T0 indicates a threshold voltage used in the voltage comparator 140. In the example of FIG. 3, the correlation output (b) exceeds the threshold voltage T0 at each of the times t11 to t15. The digital signal (c) is obtained by forming a pulse signal corresponding to the correlation output at times t11 to t15.

(2) Unstable communication status (Fig. 4)
FIG. 4 is an explanatory diagram showing another example of the output signal at the points (a), (b), and (c) shown in FIG. 1. In particular, the communication state is unstable and a communication error occurs. Shows the case.

  In FIG. 4, if the communication state is stable, a pulse signal is output at times t21, t23, t24, t25, and t27. However, since the communication state is unstable, the threshold voltage (1) T1 is high. For this reason, a pulse signal cannot be output at times t24 and t27, and a desired bit is missing (broken line portion).

  On the other hand, the voltage is low at the threshold voltage (2) T2. For this reason, at times t22 and t26, a pulse signal is output at the time when the pulse signal should not be output (dashed line portion). This is due to erroneous detection of noise and cross-correlation values.

  In the present embodiment, an AGC circuit capable of ensuring a stable reception state even if the communication state is unstable is realized by actively utilizing the characteristics of these communication errors. That is, when the signal processing unit 150 detects the state of the digital output (1), the threshold voltage is lowered by one step. When the state of the digital output (2) is detected, the threshold voltage is increased by one step. By repeating this basic operation, it is possible to realize an AGC circuit that converges to the stable communication state of FIG. 3 at any received electric field level.

  The configuration of this embodiment has been described above. Next, the operation of this embodiment will be described.

(Operation of the first embodiment)
FIG. 5 is a flowchart showing an algorithm for controlling the threshold voltage according to the present embodiment. The operation of this embodiment will be described below with reference to FIG.

  First, an initial threshold voltage (Vth) and a threshold voltage increment (ΔV) are set (step S102). Thereafter, the control loop of the following threshold voltage is entered.

  First, error determination is performed in the signal processing unit 150 (step S104). When data loss is detected in the signal processing unit 150, that is, when the state of the digital output (1) in FIG. 4C is detected, the threshold voltage is lowered by one level (step S106). At this time, Vth = Vth−ΔV is executed.

  On the other hand, when the signal processing unit 150 erroneously detects data, that is, when the state of the digital output (2) in FIG. 4C is detected, the threshold voltage is increased by one step (step S108). At this time, Vth = Vth + ΔV is executed.

  By repeating the above basic operation, it is possible to realize an AGC circuit that converges to the stable communication state of FIG. 3 at any received electric field level.

(Effects of the first embodiment)
As described above, according to this embodiment, it is possible to realize an AGC circuit that converges to a stable communication state at any received electric field level, such as in an unstable communication state.

(Second Embodiment)
FIG. 6 is an explanatory diagram illustrating a configuration of the wireless communication apparatus according to the first embodiment.

  As shown in FIG. 6, the radio communication apparatus 200 according to the present embodiment includes an antenna 210 that receives a signal, a variable gain amplifier 220 that variably amplifies the gain of the received signal, and a correlation that outputs a correlation signal from the received signal. 230, a voltage comparator (A / D converter) 240 that compares the correlation signal with a predetermined threshold voltage and outputs a pulse signal, and a signal processing unit 250 that processes the pulse signal and outputs data. It is prepared for.

  This embodiment is characterized by the function of the signal processing unit 250. This point will be described below. The other antenna 210, variable gain amplifier 220, correlator 230, and voltage comparator (A / D converter) 240 are the antenna 110, variable gain amplifier 120, and correlator according to the first embodiment (FIG. 1). 130 and the voltage comparator (A / D converter) 140 are substantially the same as those in FIG.

  In the present embodiment, the signal processing unit 250 feeds back a gain control voltage to the variable gain amplifier 220 as shown in FIG. That is, not only the threshold voltage but also the gain control of the variable gain amplifier 220 is performed, so that it is possible to cope with a UWB communication system that needs to ensure a wider dynamic range. In the AGC based on the threshold voltage control, when the threshold voltage reaches the lower limit, the gain control voltage is changed by one step to increase the gain. When the threshold voltage reaches the upper limit, the gain control voltage is changed by one step to lower the gain. After the gain change, error detection is performed again so that the threshold voltage becomes optimum.

  The configuration of this embodiment has been described above. Next, the operation of this embodiment will be described.

(Operation of Second Embodiment)
FIG. 7 is a flowchart showing an algorithm for controlling the threshold voltage according to the present embodiment. The operation of this embodiment will be described below with reference to FIG. In FIG. 7, for simplification of description, it is assumed that the gain of the variable gain amplifier 220 can be controlled in three stages of high, medium, and low.

  First, an initial threshold voltage (Vth) and a threshold voltage increment (ΔV) are set (step S202). Thereafter, the control loop of the following threshold voltage is entered.

  First, error determination is performed in the signal processing unit 150 (step S204). When the signal processor 250 detects missing data, that is, when the state of the digital output (1) in FIG. 4C is detected, the threshold voltage is lowered by one level (step S206). At this time, Vth = Vth−ΔV is executed.

  Furthermore, in this embodiment, it is determined whether the threshold voltage Vth has reached the lower limit (step S208). If the threshold voltage Vth has not reached the lower limit, the process returns to the error determination (step S204) again as in the first embodiment. On the other hand, when the threshold voltage Vth reaches the lower limit, the gain is adjusted as follows.

  If the current gain is low (step S210), the gain is increased by one level and the gain is set to medium (step S212). If the current gain is medium (step S214), the gain is increased by one step and the gain is set high (step S214). If the current gain is not medium in step S214, that is, if the current gain is high, the process returns to error determination (step S204) again without adjusting the gain.

  The case where data loss is detected in the signal processing unit 250 has been described above. On the other hand, when false detection is detected in the signal processing unit 250, that is, when the state of the digital output (2) in FIG. 4C is detected, the threshold voltage is increased by one step (step S218). At this time, Vth = Vth + ΔV is executed.

  Furthermore, in the present embodiment, it is determined whether the threshold voltage Vth has reached the upper limit (step S220). If the threshold voltage Vth has not reached the upper limit, the process returns to the error determination (step S204) again as in the first embodiment. On the other hand, when the threshold voltage Vth reaches the upper limit, the gain is adjusted as follows.

  If the current gain is high (step S222), the gain is lowered by one step and the gain is set to medium (step S224). If the current gain is medium (step S226), the gain is lowered by one step to make the gain = low (step S228). If the current gain is not medium in step S226, that is, if the current gain is low, the process returns to error determination (step S204) again without adjusting the gain.

  By repeating the above basic operation, it is possible to realize an AGC circuit that converges to the stable communication state of FIG. 3 at any received electric field level. Further, by adjusting the gain further in accordance with the adjustment of the threshold voltage, an AGC circuit having a wide dynamic range and a high completeness can be obtained.

(Effect of 2nd Embodiment)
As described above, according to the present embodiment, by incorporating these algorithms shown in FIG. 7 into the signal processing unit 250, an AGC circuit having a wide dynamic range and a high degree of completeness can be obtained. In the present embodiment, the gain of the variable gain amplifier 220 is considerably roughened to high, medium, and low, but a stable reception state can be sufficiently ensured by making the threshold voltage change step fine. This greatly contributes to cost reduction because the variable gain function of the variable gain amplifier 220 is simplified.

  The preferred embodiments of the wireless communication apparatus according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be obvious to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  For example, the following application examples can be considered.

(Application 1)
Although the case where both the threshold voltage and the gain are controlled has been described in the above embodiment, the present invention is not limited to this. Depending on the system requirements, a method may be considered in which the AGC is configured only by controlling the gain by fixing the threshold voltage.

(Application example 2)
In the UWB system configuration disclosed in Japanese Patent Laid-Open No. 2004-104403, there are a plurality of correlators for data modulation / demodulation. Even in such a case, AGC can be easily realized by applying the present invention to each correlator. Since the threshold voltage is optimum for the output of each correlator, variations between the correlators can be ignored, and there is an advantage that good characteristics can be obtained.

(Application 3)
In the case of data modulation such as OOK (On_Off_Keying), since the digital output is not output at a constant period, the AGC circuit of the present invention cannot be used as it is. In this case, the present invention can be applied by inserting a repeated fixed pattern such as “1111” into the preamble pattern and converging the AGC within that period.

(Application 4)
In the case of a system with a higher transmission speed, it is conceivable that erroneous detection between desired bits such as the digital output (b) in FIG. In such a case, erroneous detection can be detected by inserting a repetitive fixed pattern such as “1010” into the preamble pattern and reducing the apparent speed.

(Application example 5)
In the second embodiment, the case where the signal processing unit 250 feeds back the gain control voltage to the variable gain amplifier 220 has been described (FIG. 6). The present invention is not limited to such a configuration. Depending on the system configuration, the gain can be varied by adding an attenuator using a PIN diode or the like before or after the gain-fixed amplifier.

  The present invention relates to a wireless communication apparatus that performs wireless communication using a pulse wave between communication apparatuses, and more particularly to a wireless communication apparatus that performs wireless communication using a UWB (Ultra_Wide_Band) method between communication apparatuses.

It is explanatory drawing which shows the structure of the radio | wireless communication apparatus concerning 1st Embodiment. It is explanatory drawing which shows contrast with the conventional detection method. It is explanatory drawing which shows the voltage waveform at the time of the stable communication state. It is explanatory drawing which shows the voltage waveform at the time of error detection. It is a flowchart which shows the algorithm of the threshold value adjustment concerning 1st Embodiment. It is explanatory drawing which shows the structure of the radio | wireless communication apparatus concerning 2nd Embodiment. It is a flowchart which shows the algorithm of the threshold value adjustment concerning 2nd Embodiment. It is explanatory drawing which shows the structure of the conventional radio | wireless communication apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Wireless communication apparatus 110 Antenna 120 Variable gain amplifier 130 Correlator 140 Voltage comparator (A / D converter)
150 Signal Processing Unit 200 Wireless Communication Device 210 Antenna 220 Variable Gain Amplifier 230 Correlator 240 Voltage Comparator (A / D Converter)
250 Signal processor T0, T1, T2 Threshold voltage

Claims (6)

A gain amplifier for amplifying the gain of the received signal;
A correlator that despreads the output signal of the gain amplifier and outputs a correlation signal;
A voltage comparator that compares the correlation signal with a predetermined threshold voltage and outputs a pulse signal;
A signal processing unit for outputting digital data based on the pulse signal and feeding back a threshold voltage to the voltage comparator;
With
The wireless communication device, wherein the signal processing unit changes the threshold voltage when detecting an abnormality in a communication state based on the pulse signal.   The wireless communication apparatus according to claim 1, wherein the signal processing unit lowers the threshold voltage when the pulse signal is not detected.   The wireless communication apparatus according to claim 1, wherein the signal processing unit increases the threshold voltage when an erroneous detection of the pulse signal occurs.   The correlator adjusts and selects a spreading code so that an autocorrelation side lobe or a point having a poor cross-correlation is between the autocorrelation value and the autocorrelation value. The wireless communication device described. The radio communication apparatus according to claim 1, wherein the voltage comparator outputs a pulse signal by digitally integrating the correlation signal.
Received power is detected.   The wireless communication apparatus according to claim 1, wherein the signal processing unit feeds back a gain amplification voltage to the gain amplifier based on the pulse signal.

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