JP2009182441A - Communication device and calibration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a communication device which achieves calibration of high accuracy on the reception side by transmitting a test signal while an influence of transmission power dependence of amplifies is suppressed. <P>SOLUTION: The communication device employing a TDD system includes a plurality of antennas and performs calibrations of the plurality of antennas by transmission/reception of the test signal between the antennas and includes amplifiers (12<SB>1</SB>to 12<SB>M</SB>) for amplifying input signals, attenuators (13<SB>1</SB>to 13<SB>M</SB>) with variable attenuation factors for attenuating signals output from the amplifiers (12<SB>1</SB>to 12<SB>M</SB>), and a control part (15) for controlling the attenuation factors, as a configuration for adjusting powers of signals transmitted from the antennas. When attenuators (13<SB>1</SB>to 13<SB>M</SB>) attenuate the test signal, the control part (15) controls the attenuation factors so that the test signal after attenuation becomes signals of power available in calibration processing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication apparatus and a calibration method that include a plurality of antennas and compensate for the difference in analog characteristics for each antenna with high accuracy.

  The demand for high-speed wireless communication is high, and high-speed wireless communication transmission technology is required. Therefore, recently, a technique in which a transmitting-side radio (transmitter) and a receiving-side radio (receiver) perform high-speed signal transmission using a plurality of antennas has been widely studied. In future mobile communications, an environment in which the base station simultaneously performs spatial multiplexing transmission using a transmission beam to a plurality of wireless terminals is also assumed. In addition, the transmission power required for communication can be reduced by performing appropriate transmission beam forming in the wireless terminal. Therefore, high-accuracy transmission beam forming technology is considered as an important issue in the future.

  Among them, in the TDD (Time Division Duplex) method in which the same frequency is alternately used in the uplink and the downlink, there is an expectation for an advantage that the channel reversibility can be used when forming a transmission beam. Usually, channel information is required at the transmitter to properly control the transmit beam. At this time, when the ideal channel reversibility is obtained in the TDD scheme, the transmitter can easily perform channel measurement using a pilot signal transmitted from the receiver to the transmitter (that is, on the reverse link). It is possible to grasp the channel state from the transmitter to the receiver.

  However, in reality, reversibility is established in the actual propagation path from the antenna end of the transmitter to the antenna end of the receiver, but it is measured in the digital domain due to the characteristic difference between the analog devices in the transmitter and receiver circuits. Complete reversibility does not hold in the propagation path (hereinafter referred to as measurement propagation path).

  For this reason, a radio that performs propagation path measurement in the digital domain usually requires calibration that can compensate for the difference in transmission / reception analog characteristics in order to use reversibility. Patent Document 1 below describes a calibration apparatus that realizes such calibration for compensating for an analog characteristic difference. Specifically, a method is described in which a test signal for calibration is exchanged between a plurality of antennas in a wireless device, and calibration (compensation for analog characteristic difference) is performed based on a channel measurement result.

JP 2006-279668 A

  Here, in a general calibration method including the method using the calibration device described in Patent Document 1, a test signal is transmitted with a transmission power smaller than that in actual communication (when communication is performed in an actual environment), Perform calibration. This is because a plurality of antennas in the wireless device are in a close positional relationship, and it is necessary to suppress transmission power in order to obtain appropriate reception power. That is, if the received power is too large, the receiving amplifier may be saturated and appropriate channel measurement may not be performed.

  On the other hand, during actual communication, the signal is transmitted with a transmission power larger than that of the test signal. However, the characteristics of the transmission amplifier in the radio have transmission power dependence, and if the amplification factor or transmission power changes greatly, transmission is performed accordingly. The phase of the signal changes. Therefore, even if calibration is performed using test signals and the phase relationship between the antennas is matched, the characteristics of the amplifier change depending on the power dependence during transmission of the communication signal during actual communication, and the phase relationship between the antennas There was a problem that could not be held. That is, when calibration is performed by adjusting the transmission power of the test signal by keeping the amplification factor of the transmission amplifier low, there is a problem that the compensation accuracy deteriorates.

  The present invention has been made in view of the above, and obtains a communication device and a calibration method for performing antenna calibration with high accuracy while minimizing the influence of amplifier characteristic fluctuation caused by power dependency. For the purpose.

  In order to solve the above-described problems and achieve the object, the present invention provides a TDD system that has a plurality of antennas and performs calibration of the plurality of antennas by transmitting and receiving test signals between the plurality of antennas. In the communication device, as a configuration for adjusting the power of a signal transmitted from the antenna, an amplification unit that amplifies an input signal, an attenuation unit that attenuates a signal output from the amplification unit, and a variable attenuation factor; Control means for controlling the attenuation rate of the attenuation means, and when the attenuation means attenuates the test signal, the control means becomes a signal of power that can be used in the calibration process when the attenuated test signal is attenuated. Thus, the attenuation rate is controlled.

  According to the present invention, when transmitting a test signal for performing calibration between antennas, the power of a signal transmitted during normal operation by performing predetermined analog signal processing on the test signal after analog conversion The transmission power is temporarily amplified until it reaches the same level as that, and further, the amplified signal is attenuated and transmitted until the transmission power reaches a level at which calibration can be performed. The test signal can be transmitted in a state where the influence is suppressed, and the test signal receiving side has an effect that calibration can be performed with high accuracy.

  Embodiments of a communication apparatus and a calibration method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

First, the necessity of calibration in the TDD method will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of a signal transmission model between communication apparatuses # 1 and # 2 in a real environment. 1, T ₁ , T ₂ ,..., T _M indicate RF analog characteristics of the transmission system corresponding to the antennas # 1, # 2,..., #M, and R ₁ , R ₂ ,. _M indicates the RF analog characteristics of the receiving system corresponding to the antennas # 1, # 2,. Further, DAC indicates a digital / analog converter that converts a digital signal into an analog signal, and ADC indicates an analog / digital converter that converts the analog signal into a digital signal. The RF analog characteristics of the transmission system include characteristics such as a transmission amplifier, an analog path, and an analog filter, and the RF analog characteristics of the reception system include characteristics of a reception amplifier, an analog path, and an analog filter.

In TDD communication, there is an expectation that the communication device can use propagation path reversibility when performing transmission beam formation using a plurality of antennas. In the TDD scheme with reversibility, the channel state of the downlink (uplink) can be grasped by measuring the channel of the uplink (downlink). As a result, even if the receiving communication apparatus does not feed back the channel measurement result as control information, the transmitting communication apparatus can perform transmission beam control using the channel measurement result on the reverse link. For example, in transmission beam control from a base station to a wireless terminal station, the base station can use the channel measurement result in the uplink from the wireless terminal station to itself. However, in reality, as shown in FIG. 1, although reversibility in the actual propagation path is established, there is a characteristic difference between each transmission / reception system analog device. Therefore, different phase noises are added to the transmission and reception signals in the uplink and the downlink, and the propagation path measured in the digital domain differs between the uplink and the downlink. Therefore, in order to use the propagation path reversibility (reverse link channel measurement result), calibration to compensate for the difference between transmission and reception analog characteristics is required. Here, when the RF analog characteristics T ₁ , T ₂ ,..., T _M or the transmission power change greatly, the characteristics of the transmission amplifier also change accordingly. That is, the characteristics of the transmission amplifier generally have transmission power dependency.

  Therefore, in the communication apparatus according to the present invention, calibration is executed according to the procedure shown in the following embodiments.

Embodiment 1 FIG.
FIG. 2 is a diagram illustrating a configuration example of the communication apparatus according to the present embodiment, and illustrates a minimum configuration example necessary for performing calibration. As shown in FIG. 2, the communication device 1 according to the present embodiment includes DACs 11 _{1 to} 11 _M , amplifiers 12 _{1 to} 12 _M , attenuators 13 _{1 to} 13 _M , ADCs 14 _{1 to} 14 _M and a control unit 15. . In addition, antennas are connected to the attenuators 13 _{1 to} 13 _M , respectively. The amplification factor of each amplifier and the attenuation factor of each attenuator are variable. The present embodiment is characterized in that a test signal transmitted during calibration is attenuated by an attenuator.

The DAC 11 _m (m = 1, 2,..., M) is a digital / analog converter, and converts an input digital signal into an analog signal. The amplifier 12 _m amplifies the input signal. The attenuator 13 _m attenuates the input signal. The ADC 14 _m is an analog / digital converter and converts an input analog signal into a digital signal. The control unit 15 individually determines an amplification factor when the amplifier 12 _m performs an amplification process and an attenuation factor when the attenuator 13 _m performs an attenuation process, and executes each of the amplifiers so as to execute a process according to the determination result. And control the attenuator.

The signal (transmission signal) output from the DAC 11 _m is input to the attenuator 13 _m after performing predetermined processing including amplification processing and filtering processing by the amplifier 12 _m . Then, after the attenuator 13 _m adjusts the power value to a desired value, it is transmitted via the corresponding antenna. The RF analog characteristic in the system (transmission system) from the DAC 11 _m to the attenuator 13 _m at this time is indicated by “T _m ” in FIG. In addition, signals received by the respective antennas are output from the corresponding attenuators 13 _m , are subjected to predetermined processing, and are then input to the ADC. Shows the RF analog characteristics in FIG. 2 "R _m" in the attenuator 13 system to be input to the output ADC 14 _m from _m of the time (reception system).

  Subsequently, the operation of the communication apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing an example of the operation of the communication apparatus 1 and shows a control procedure when communicating with another communication apparatus after executing calibration.

(Control # 1) In performing calibration, the control unit 15 determines the amplification factor of each amplifier and the attenuation factor of the attenuator, and sets the determined amplification factor and attenuation factor to each amplifier and each attenuator ( Step S31). Here, the signal (test signal) after attenuation by each attenuator so that the amplification factor used by each amplifier is as close as possible to the value used during normal operation (when communicating with other communication devices) ) Is set to be close to the power (desired power) of the test signal transmitted during the existing calibration process (so that it becomes a power test signal that can be used for calibration). In other words, in the conventional (existing) calibration process, only the amplifier is controlled, and the amplification factor is adjusted to a value different from that during normal operation so that the power of the test signal is adjusted to a desired value. On the other hand, the communication device 1 controls the amplification factor and the attenuation factor, the power of the signal (communication signal) output from the amplifier 12 _m during normal operation, and the signal (test signal) output from the amplifier 12 _m during calibration processing. The received power of the test signal on the receiving side is adjusted to a desired value while maintaining the same power as the above.

(Control # 2) Next, calibration is performed to compensate for the analog characteristic difference (step S32). Specifically, the test signal is exchanged between the antennas provided in itself to compensate for the analog characteristic difference between the antennas. There are various conventional calibration methods, and any existing method may be used.

(Control # 3) When transmitting / receiving a communication signal to / from another communication device, the control unit 15 performs control to reduce the attenuation rate of each attenuator (attenuators 13 _{1 to} 13 _M ), Communication signals are transmitted and received (step S33). As a special case, the attenuation rate may be set to 0 and no attenuation may be performed. The amplification factor is controlled so as to be the amplification factor used during normal operation. In addition, a communication signal reflecting the calibration result executed in (Control # 2) is transmitted.

  As described above, the communication apparatus 1 includes the attenuator. In the above (control # 1), setting is performed so as to increase the attenuation rate of the attenuator at the time of executing calibration (decrease the power of the input signal). The amplification factor is set to a larger value than when the conventional calibration method is executed. That is, the calibration test signal is amplified once and then transmitted after being attenuated. As a result, the test signal can be received at the receiving side (receiving system) with the same level of power as when the conventional calibration method is executed. Therefore, the difference in the transmission power or amplification factor of the transmission amplifier between the calibration test signal transmission and the communication signal transmission can be made smaller than in the prior art, and the power dependency problem of the transmission amplifier can be alleviated. As a result, in the conventional calibration method, even if calibration is performed, a change in amplifier characteristics due to a difference in transmission power during calibration and during communication becomes a problem. In the communication apparatus 1 according to the present embodiment, this problem is eliminated. Can be reduced.

  In particular, as a desirable configuration, in (Control # 1), the amplification factor of the amplifier is set to be the same as that during transmission of the communication signal, and the attenuation factor of the attenuator is greatly adjusted so that the reception system can receive the test signal for calibration. In this case, since the amplifier is set in the same power state during communication (during normal operation) and during calibration, calibration can be performed in the same state as during communication. As a result, it is possible to completely eliminate the problem of the difference in amplifier characteristics caused by the difference in transmission power between the test signal transmitted during calibration and the communication signal transmitted during communication.

  Here, in the present embodiment, calibration is performed including the attenuator characteristics in (Control # 1) and (Control # 2) described above, whereas in (Control # 3), the attenuation rate is adjusted during calibration. The transmission / reception of the communication signal is performed as a value different from the above, but it will be described that the reversibility of the up / down link can be maintained also in this case.

  First, in the setting state of the attenuators of (control # 1) and (control # 2), a state is established in which the uplink / downlink propagation path reversibility can be used by calibration. Next, focusing on the fact that the attenuators generally have the same characteristics in the upper and lower links, even if the attenuation factor is changed, the attenuation factors of the upper and lower links are set to be the same. That is, as the attenuation factor changes in the downlink (or uplink), the attenuation factor also changes in the uplink (downlink), and the reversibility between the uplink and downlink is maintained even after the attenuation factor is changed. Thus, even if the attenuation rate of the attenuator is changed between calibration and normal operation (when transmitting a communication signal), the channel reversibility in the TDD scheme can be maintained.

  In summary, the present embodiment is characterized in that an attenuator is inserted in a portion common to the transmission / reception system of the antenna that transmits the test signal at the time of calibration, and the transmission amplification factor in this system is increased. The amplifier is brought into a state close to that at the time of communication signal transmission to solve the problem of power dependency of the transmission amplifier. In normal operation (when transmitting a communication signal), the attenuation factor of the attenuator is set to 0 or small, and the transmission power radiated from the antenna is reduced while maintaining the channel reversibility. The value required for communication. By performing calibration according to the procedure shown in the present embodiment, the problem of the power dependency of the transmission amplifier, which has been a problem in the conventional calibration, can be solved.

  Further, although the communication apparatus shown in FIG. 2 is configured to include the same number of attenuators as the number of antennas for convenience of explanation, only a system corresponding to some antennas may be configured to include attenuators. . That is, it is only necessary that at least one antenna system includes an attenuator. For example, in the calibration of two antennas, if an attenuator is inserted only into the system of one antenna (reference antenna), the calibration in the procedure shown in (Control # 1) and (Control # 2) is performed. realizable. At this time, the attenuated test signal is transmitted from the reference antenna. On the other hand, an unattenuated test signal is transmitted from an antenna other than the reference antenna, and this signal is attenuated after being received by the reference antenna.

In the above description, the attenuation rate of each attenuator included in the communication apparatus 1 shown in FIG. In this example, the attenuation rate of each attenuator need not be variable. For example, as shown in FIG. 4, if the changeover switch 21 _m for selecting the presence / absence of the attenuator is provided, each attenuator attenuation factor may not be variable. In this case, “no attenuator” corresponds to a state of “attenuation rate 0”. Controller 15a of the communication device 1a, instead of the control of the attenuation factor of the attenuator 13 _m to the control unit 15 of the communication apparatus 1 performs, controls the selector switch 21 _m. Note that the changeover switch 21 _m and the control unit 15a operate as signal selection means.

Embodiment 2. FIG.
Next, the second embodiment will be described. In the first embodiment, it has been described that the existing method can be used as the calibration method executed in the above (Control # 2). However, in the present embodiment, as an example of the existing method, the above-mentioned patent document The case where the technique described in 1 is used will be described.

  FIG. 5 is a diagram illustrating a configuration example of the communication apparatus according to the second embodiment. The communication device 1b according to the present embodiment has a configuration in which a channel measurement / correction coefficient control unit 31 and a correction unit 32 are added to the communication device 1 according to the first embodiment (see FIG. 2). Since the other parts are the same as those of the communication device 1 described in the first embodiment, the same reference numerals are given and description thereof is omitted.

  The channel measurement / correction coefficient control unit 31 performs calibration for each antenna, and calculates a correction coefficient used when the correction unit 32 corrects a signal transmitted from each antenna. That is, an operation as a calibration unit is performed. The correction unit 32 corrects the signal transmitted from each antenna using the correction coefficient calculated by the channel measurement / correction coefficient control unit 31.

  The calibration (phase difference detection method) by the calibration apparatus described in Patent Document 1 can be applied when there are three or more antennas, but it can be applied as it is as (Control # 2). In this case, the communication device 1b holds data on the distance between antennas or phase difference in advance. For example, the data is stored in the channel measurement / correction coefficient control unit 31.

  In calibration, first, a pilot signal (test signal) is transmitted from antennas # 1 and # 2 to antenna #M (M ≧ 3), and channel measurement / correction coefficient control unit 31 performs channel measurement at antenna #M ( Next, a pilot signal is transmitted from the antenna #M to the antennas # 1 and # 2, and the channel measurement / correction coefficient control unit 31 performs channel measurement at the antenna # 1 and the antenna # 2 (S53, S54). ).

  Next, the channel measurement / correction coefficient control unit 31 corrects the correction coefficient based on each channel measurement value obtained by executing the channel measurement and the stored distance or phase difference data between the antennas. The correction unit 32 corrects the phase of the transmission signal for each antenna. The details of the correction method are the same as the procedure described in Patent Document 1. That is, the correction unit 32 performs phase correction by multiplying each input transmission signal by a corresponding correction coefficient.

  Thus, as a calibration method in the above-described (Control # 2), calibration by the calibration device described in Patent Document 1 can be applied.

  In the present embodiment, the case where the communication device 1b is realized by adding the channel measurement / correction coefficient control unit 31 and the correction unit 32 to the communication device 1 has been described. However, the communication device 1a (see FIG. 4). However, it is also possible to add a channel measurement / correction coefficient control unit 31 and a correction unit 32.

Embodiment 3 FIG.
Next, Embodiment 3 will be described. In the present embodiment, a case will be described in which a method different from the method shown in the second embodiment is used as the calibration method in (Control # 2).

FIG. 6 is a diagram illustrating an example of a signal transmission model by the communication device according to the third embodiment, and illustrates a transmission model between one antenna of a base station that is a TDD communication device and antenna #m of a wireless terminal. ing. The configuration of the communication device (wireless terminal) of the present embodiment shown in FIG. 6 is the same as that of communication device 1b shown in the second embodiment, and the same parts are denoted by the same reference numerals. The correction unit 32 includes a plurality of correction coefficient multiplication units 32 _m (m = 1,..., M) that multiply the input signal by a correction coefficient (u _m ). Hereinafter, the transmission analog gain of antenna #m of the base station and the wireless terminal will be described as T _BS and T _m , and the reception analog gain will be described as R _BS and R _m , respectively. Usually, in a wireless communication system, T _BS , T _m , R _BS , and R _m vary according to the temperature characteristics of the analog device in a time unit t _RF (for example, 10 seconds or more) that is sufficiently longer than the fading period.

At this time, each of the uplink measurement channel gain h _m ^(UL) and downlink measurement channel gain h _m ^(DL) by the following equation which is measured in the digital domain between the antenna #m of the base station and the wireless terminal It is represented by (1).
h _m ^(UL) = T _m · g _m ^(UL) · R _BS
h _m ^(DL) = T _BS · g _m ^(DL) · R _m (1)

Here, g _m ^(UL) and g _m ^(DL) are gains of the actual propagation path between the base station and the antenna #m of the wireless terminal in the uplink and the downlink, respectively. According to the radio wave propagation theory, reversibility occurs in an actual propagation path without fluctuation, and g _m ^(UL) = g _m ^(DL) . This relationship holds in a wireless communication environment with antenna coupling and various reflections.

Here, as shown in FIG. 6, complex correction coefficients u _m (m = 1,..., M) are transmitted in the digital domain of antenna #m of the wireless terminal (digital signal processing unit corresponding to each antenna of the wireless terminal). Multiply the signal to calibrate. Specifically, the correction coefficient multiplication unit 32 _m multiplies the complex correction coefficient u _m . In this case, the uplink measurement channel performing the correction between the antenna #m of the base station and the wireless terminal u _m h _m ^(UL), measuring the channel downlink subjected to correction and h _m ^(DL) expressed. Therefore, in order to maintain reversibility between the antenna #m (m = 1,..., M) of the wireless terminal and the base station, the condition of the following equation (2) is required.

  Using equation (1), equation (2) can be written in the form of equation (3) below.

Here, if u ₁ = 1 is set and u _m (m = 2,..., M) is set to the following equation (4), the above equation (3) is satisfied.

Here, h _m ^{self, F} is the gain of the measurement propagation path from antenna #m to antenna # 1 of the wireless terminal ^, and h _m ^{self, R} is the gain of the measurement propagation path from antenna # 1 to antenna #m of the wireless terminal. These are each represented by the following equation (5).
h _m ^{self, F} = (L _m T _m ) · g _m ^{self, F} · (L ₁ R ₁ )
h _m ^{self, R} = (L ₁ T _l ) · g _m ^{self, R} · (L _m R _m ) (5)

Here, L _m is the gain of the attenuator corresponding to the antenna #m of the wireless terminal, g _m ^{self, F} is the gain of the actual propagation path from the antenna #m of the wireless terminal to the antenna # 1, and g _m ^{self, R} is This is the gain of the actual propagation path from antenna # 1 to antenna #m of the wireless terminal, and reversibility (g _m ^{self, R} = g _m ^{self, F} ) is established in the actual propagation path. The above equation (5) includes the attenuator influence L _m for each antenna during calibration.

  Therefore, calibration can be performed by setting the coefficient of the above equation (4) in the presence of an attenuator. The procedure of calibration (calibration in (control # 2) shown in the first embodiment) in the communication apparatus of the present embodiment will be described below. A flowchart of this procedure is shown in FIG.

(Procedure # 2-1) A pilot signal (test signal) is transmitted from each antenna #m, and further, these pilot signals are received by the antenna # 1, and the antenna #m (m = 2, 2) is received using the received pilot signal. ..., M) channel corresponding to the pilot signal from the (gain measurement channel) h _m ^self, to measure ^F (step S71). Channel measurement is performed by the channel measurement / correction coefficient control unit 31.
(Procedure # 2-2) A pilot signal is transmitted from the antenna # 1, and further, this pilot signal is received by the antenna #m (M = 2,..., M), and is received from the antenna # 1 using the received pilot signal. Each channel h _m ^{self, R} corresponding to the pilot signal is measured (step S72). Channel measurement is performed by the channel measurement / correction coefficient control unit 31.
(Step # 2-3) channel measurement and the correction coefficient control unit 31, the above procedure (2-1) and (2-2) Run-obtained measured channel information ^{_{h m self, F, h m}} self, ^{R (m = 2, ...,} M) using a correction coefficient of the antenna ^{_{#m u m = h m self,}} R / h m self, calculates the ^F (step S73).

  As described above, in the calibration according to the present embodiment, the channel measurement / correction coefficient control unit 31 transmits a signal from a specific one antenna, measures the channel at the mth antenna, and further, the mth antenna. Since the signal is transmitted from and the channel is measured by the specific antenna, the amplitude phase (amplitude and phase) or the phase of the transmission signal or the reception signal is corrected using the ratio of the two channel measurement values. Reversibility can be maintained in the measurement propagation path. The ability to maintain the propagation path reversibility is also proved as a theoretical development in the above formulas (1) to (5).

  Note that the method described in the present embodiment, unlike the calibration described in the second embodiment, does not need to store data such as antenna intervals in advance (without using data such as antenna intervals). Calibration can be performed). Further, the calibration shown in the second embodiment is applicable when there are three or more antennas, but the calibration according to the present embodiment is applicable when there are two or more antennas (M ≧ 2).

Embodiment 4 FIG.
Next, the fourth embodiment will be described. In this embodiment, a method for determining the amplification factor of the amplifier and the attenuation factor of the attenuator in (control # 1) shown in the first embodiment will be described.

The received power of the test signal when performing calibration needs to be within the allowable range of the receiving amplifier. Therefore, first, a weak test signal is once transmitted from the target transmitting antenna and received by the target receiving antenna. After increasing the amplification factor of the transmission amplifier (corresponding to the amplifier 12 _m of the communication apparatus 1 shown in FIG. 2) so that the received power level is within an allowable range, the attenuator (FIG. 2) is used based on that state. The attenuation factor of the attenuator 13 _m of the communication apparatus 1 and the amplification factor of the transmission amplifier shown in FIG. For example, if the amplification factor is increased by 10 dB, the attenuation factor is also increased by 10 dB at the same time. This operation is repeated many times until the amplification factor of the transmission amplifier becomes comparable to the communication signal transmission state.

  By simultaneously changing the amplification factor of the transmission amplifier and the attenuation factor of the corresponding attenuator at the same rate, the antenna receiving the test signal can maintain the same reception power state. In addition, the transmission amplifier can be brought close to the same state as during communication while maintaining the state where the reception power on the reception side is within the allowable range of the reception amplifier.

  Thus, it is also one of the features of the present invention that the amplification factor of the transmission amplifier and the attenuation factor of the attenuator are changed many times at the same rate.

  As described above, the communication device and the calibration method according to the present invention are useful when performing calibration of a plurality of antennas, and in particular, a communication device that performs calibration by transmitting and receiving test signals between adjacent antennas, and Suitable for calibration method.

It is a figure which shows an example of the signal transmission model in a real environment. It is a figure which shows the structural example of Embodiment 1 of the communication apparatus concerning this invention. It is a flowchart of control in Embodiment 1 of the communication apparatus concerning this invention. It is a figure which shows the other structural example of Embodiment 1 of the communication apparatus concerning this invention. It is a figure which shows the structural example of Embodiment 2 of the communication apparatus concerning this invention. FIG. 11 is a diagram illustrating an example of a signal transmission model by the communication device according to the third embodiment. 10 is a flowchart illustrating an example of a calibration procedure executed by the communication apparatus according to the third embodiment.

Explanation of symbols

1, 1a, 1b Communication device 11 _{1 to} 11 _M DAC
12 _{1 to} 12 _M amplifier 13 _{1 to} 13 _M attenuator 14 _{1 to} 14 _M ADC
15, 15a Control unit 21 _{1 to} 21 _M changeover switch 31 Channel measurement / correction coefficient control unit 32 Correction unit 32 _{1 to} 32 _M correction coefficient multiplication unit

Claims (10)

A TDD communication apparatus that has a plurality of antennas and calibrates the plurality of antennas by transmitting and receiving test signals between the plurality of antennas,
As a configuration for adjusting the power of the signal transmitted from the antenna,
Amplifying means for amplifying the input signal;
Attenuating means for attenuating the signal output from the amplifying means, and a variable attenuation factor;
Control means for controlling the attenuation rate of the attenuation means;
With
When the attenuation means attenuates a test signal, the control means controls the attenuation rate so that the attenuated test signal becomes a power signal that can be used in calibration processing. .   The control unit controls the attenuation rate so that an attenuation rate when the attenuation unit attenuates a signal transmitted to another communication device is lower than an attenuation rate when the test signal is attenuated. The communication device according to claim 1.   3. The control unit according to claim 1, wherein the control unit controls the attenuation rate so that the attenuation rate when the attenuation unit attenuates a signal transmitted to another communication apparatus is “0”. 4. The communication device described. The amplification factor of the amplification means is variable,
4. The communication apparatus according to claim 1, wherein the control unit changes the amplification factor by the same change amount as the change amount of the attenuation factor when changing the attenuation factor. 5. further,
Calibration for performing calibration based on a test signal transmitted via a first antenna that is a part of the plurality of antennas and received via a second antenna different from the first antenna Means,
Correction means for correcting the phase of a signal to be transmitted to another communication device based on a calibration result by the calibration means;
The communication apparatus according to any one of claims 1 to 4, further comprising: A TDD communication apparatus that has a plurality of antennas and calibrates the plurality of antennas by transmitting and receiving test signals between the plurality of antennas,
As a configuration for adjusting the power of the signal transmitted from the antenna,
Amplifying means for amplifying the input signal;
Attenuating means for attenuating the signal output from the amplifying means;
Select one of the first signal output from the amplifying means and the second signal obtained by attenuating the first signal by the attenuating means, and select all of the plurality of antennas. Or a signal selection means for transmitting via a part;
With
The signal selection means, when transmitting a test signal, selects the second signal.   The communication apparatus according to claim 6, wherein the signal selection unit selects the first signal when transmitting a signal to another communication apparatus. further,
Calibration for performing calibration based on a test signal transmitted via a first antenna that is a part of the plurality of antennas and received via a second antenna different from the first antenna Means,
Correction means for correcting the phase of a signal to be transmitted to another communication device based on a calibration result by the calibration means;
The communication apparatus according to claim 6, further comprising: In a TDD communication apparatus having a plurality of antennas, a calibration method for compensating for an analog characteristic difference for each antenna,
An amplification step for amplifying the test signal;
An attenuation step for attenuating the test signal after being amplified in the amplification step to generate a test signal of desired power;
A calibration step for calibrating the plurality of antennas based on a test signal of desired power generated in the attenuation step;
A calibration method comprising:   The calibration method according to claim 9, wherein in the amplification step, the test signal is amplified at an amplification factor equivalent to that when a signal transmitted to another communication apparatus is amplified.

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