JP2007134809A - Wireless system, wireless transmitter, wireless receiver and wireless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless system having a small and simple block configuration which cancels a phase noise by using a transmission local signal as a reception local signal. <P>SOLUTION: A wireless transmitter 101 transmits a multiplexed signal in which an information signal having no sub-carrier arranged on the center frequency of a carrier wave and the transmission local signal for frequency conversion are multiplexed as a carrier wave. In a wireless receiver 151, a signal distributor 154 separates and extracts the information signal and the transmission local signal from the multiplexed signal transmitted from the wireless transmitter 101, and distributes the separated signals. A local signal extracting filter 158 uses the extracted transmission local signal as the reception local signal for frequency conversion. On the other hand, an information signal branch 155 extracts the information signal distributed in the signal distributor 154. Further, a reception frequency converter 156 applies frequency conversion to the extracted information signal based on the reception local signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radio system or the like that transmits an information signal using subcarriers, and more particularly to a radio system, radio transmitter, and radio that transmit an information signal with high communication quality by canceling phase noise using a pilot signal. The present invention relates to a receiving device and a wireless communication device.

  Generally, when information with a large amount of information such as moving images is transmitted wirelessly, a wide bandwidth is required. As a method of transmitting a signal having such a wide bandwidth, for example, there is a method of collecting subcarriers and converting them into multicarriers. In such multi-carrier transmission, the transmission characteristics deteriorate due to the phase noise between the wireless transmission device and the wireless reception device, so it is necessary to cancel the phase noise between the wireless transmission device and the wireless reception device using some method. become.

  Conventionally, as a wireless communication apparatus that cancels phase noise, an information signal having an appropriate bandwidth collected by a plurality of subcarriers and a pilot signal for removing phase noise are superimposed, and the information signal and the pilot signal are combined. One configured to transmit a superimposed signal is known (for example, see Patent Document 1). According to the wireless communication device according to this patent document, in the wireless transmission device, an oscillation signal oscillated by the transmission local oscillation unit in the wireless transmission device is multiplied to generate a transmission local signal, and the oscillation signal oscillated by the transmission local oscillation unit Is divided to generate a pilot signal. Then, the OFDM (Orthogonal Frequency Division Multiplex) information signal and the pilot signal are superimposed, the superimposed signal is frequency-converted with a transmission local signal, a carrier wave is generated, and the carrier wave is transmitted. ing. According to such a configuration, since the transmission local signal and the pilot signal are generated by multiplying or dividing the oscillation signal oscillated by the same transmission local oscillation unit, the pilot signal and the transmission local signal have a certain frequency relationship. Can be held.

Further, the wireless reception device receives the carrier wave transmitted by the wireless transmission device as a reception signal. At this time, a reception local signal is generated by multiplying the oscillation signal oscillated by the reception local oscillation unit in the wireless reception device, and the frequency of the reception signal is converted by the reception local signal. Furthermore, the frequency-converted signal is multiplied, the phase of the multiplied signal is compared with the phase of the oscillation signal oscillated by the reception local oscillation unit, and the reception local oscillation is performed so that the phase difference between the two becomes zero. The phase of the oscillation signal that oscillates is controlled. According to such a configuration, the reception signal and the oscillation signal oscillated by the reception local oscillation unit can maintain a constant frequency relationship. Therefore, with the above-described configuration, the wireless transmission device and the wireless reception device can maintain a certain frequency relationship, so that a wireless communication device that cancels phase noise can be realized.
JP-A-11-205280

  However, the wireless communication device described in Patent Document 1 uses a pilot signal to cancel phase noise between the wireless transmission device and the wireless reception device. When this pilot signal is superimposed on an information signal that has been converted to OFDM by the wireless transmission device, the pilot signal is located on the upper side or the lower side of the information signal and has a frequency arrangement slightly away from the information signal that has been converted to OFDM. Superposed with the information signal. Therefore, since pilot signals arranged at a frequency slightly apart from the bandwidth of the information signal converted to OFDM are transmitted, a wider transmission bandwidth is required than the information signal converted to OFDM that should be originally transmitted.

  For example, when the bandwidth of the information signal converted to OFDM is 6 MHz and the frequency allocation where the pilot signal is allocated is 1 MHz (that is, frequency allocation 1 MHz away from the information signal converted to OFDM), the transmission bandwidth is 7 MHz. And a wide transmission bandwidth of 10% or more with respect to the bandwidth of 6 MHz of the information signal converted to OFDM. As a result, the frequency utilization efficiency decreases.

  The present invention has been made in view of this point, and can realize communication with high frequency utilization efficiency such that phase noise can be appropriately canceled even if a pilot signal is superimposed on an information signal without widening the transmission bandwidth. An object is to provide a wireless system, a wireless transmission device, a wireless reception device, and a wireless communication device.

  The wireless system of the present invention arranges an information signal in which a subcarrier is not arranged at the center frequency of the carrier wave and a transmission local signal for frequency conversion in the vicinity of the center frequency of the carrier wave, and multiplexes the information signal and the transmission local signal. A wireless transmission device that generates and transmits the multiplexed signal, and receives the multiplexed signal transmitted from the wireless transmission device, separates and extracts the information signal and the transmission local signal from the multiplexed signal, and extracts the extracted transmission local A configuration is provided that includes a wireless reception device that uses a signal as a reception local signal.

  With such a configuration, the transmission local signal of the wireless transmission device can be multiplexed with the information signal and transmitted. As a result, the wireless reception device can receive the carrier wave transmitted from the wireless transmission device, extract a transmission local signal, and use the extracted transmission local signal as a reception local signal for frequency conversion. Phase noise between the transmission device and the wireless reception device can be canceled.

  The radio transmission apparatus according to the present invention is a radio transmission apparatus applied to a radio system that transmits information signals using subcarriers, and generates a modulation signal that generates an information signal in which no subcarrier is arranged at the center frequency of a carrier wave. A generation unit, a transmission local signal generation unit that generates a transmission local signal for frequency conversion based on the information signal generated by the modulation signal generation unit, and the information signal is converted to a carrier frequency and the frequency is converted to the carrier wave. The transmission frequency conversion unit that multiplexes the received information signal and the transmission local signal and the antenna that transmits the multiplexed information signal and the transmission local signal are employed.

  Furthermore, the radio reception apparatus of the present invention is a radio reception apparatus that receives a multiplexed signal in which an information signal in which a subcarrier is not arranged at the center frequency of a carrier wave and a transmission local signal for frequency conversion are multiplexed from the radio transmission apparatus. An amplification unit that receives and amplifies the multiplexed signal transmitted from the wireless transmission device, a signal distribution unit that distributes the multiplexed signal amplified by the amplification unit, and an information signal from the multiplexed signal distributed by the signal distribution unit Information signal branch unit for extracting the local signal from the multiplexed signal distributed by the signal distribution unit to extract the local signal as a reception local signal for frequency conversion, and the information signal based on the received local signal A reception frequency conversion unit that converts the frequency of an information signal transmitted through the branch unit, a signal processing unit that performs signal processing on the information signal, and an information signal branch unit A reception signal level detection unit that detects a signal level of the reception signal by a report signal; and a variable amplification unit that varies the signal level of the reception local signal in accordance with the level of the reception signal detected by the reception signal level detection unit. The composition is taken.

  That is, the radio reception apparatus of the present invention arranges the information signal in which the subcarrier is not arranged at the center frequency of the carrier wave transmitted from the radio transmission apparatus and the transmission local signal for frequency conversion in the radio transmission apparatus at the center frequency of the carrier wave, In addition, the multiplexed signal that has been multiplexed is received and the extracted transmission local signal is used as a reception local signal for frequency conversion. Also, the received signal level is detected by the extracted information signal, and variable according to the detection level. The received local signal level is kept constant by varying the amplifier. In other words, the transmission local signal extracted by the wireless reception device is used as a reception local signal for frequency conversion, the reception signal level is detected by the extracted information signal, and the variable amplifier is operated in accordance with the detection level. . Therefore, even when there is a fluctuation in the level of the received signal due to radio wave propagation, the level of the received local signal can be kept constant.

  In addition to the configuration of the above invention, the wireless reception device of the present invention includes an amplification unit that linearly varies the phase of the received local signal extracted by the local signal extraction filter unit and holds the output level constant. Is adopted.

  With such a configuration, even when there is a fluctuation in the level of the received signal due to radio wave propagation, the phase of the received local signal varies linearly, so that there is no distortion and the level of the received local signal can be kept constant.

  According to the present invention, a wireless communication device can be constructed by the wireless transmission device and the wireless reception device of the invention. That is, the wireless transmission device can multiplex and transmit the transmission local signal and the information signal. The wireless reception device receives the carrier wave transmitted from the wireless transmission device, uses the transmission local signal extracted from the reception signal as the reception local signal for frequency conversion, and detects the reception signal level from the extracted information signal The variable amplifier is operated corresponding to the detection level. This makes it possible to linearly change the phase of the received local signal even when the level of the received signal varies due to radio wave propagation. Therefore, it is possible to construct a wireless communication apparatus that can keep a received local signal without distortion constant.

  According to the wireless system of the present invention, a wireless transmission device transmits a multiplexed signal obtained by multiplexing an information signal in which a subcarrier is not arranged at the center frequency of a carrier wave and a transmission local signal for frequency conversion. Then, the wireless reception device receives the multiplexed signal transmitted from the wireless transmission device, extracts the information signal and the transmission local signal, and uses the transmission local signal as a reception local signal for frequency conversion. As a result, phase noise between the wireless transmission device and the wireless reception device can be canceled, and it is not necessary to provide a reception local signal generation unit on the wireless reception device side, so that the cost of the wireless reception device can be reduced. In addition, the size and weight can be reduced.

<Summary of invention>
In the wireless system of the present invention, a transmission local signal used in a wireless transmission device is arranged at the center frequency of a subcarrier that is subcarrierized and has no information on the center frequency of the carrier. Then, the transmission local signal is extracted by the wireless reception device, and the extracted transmission local signal is used as the reception local signal. Thereby, phase noise can be canceled appropriately. Further, by using the extracted transmission local signal as a reception local signal, a reception local signal generation unit for generating a reception local signal of the wireless reception device is not necessary. As a result, a wireless receiver having a small and simple configuration can be realized.

  Hereinafter, some embodiments of a wireless system according to the present invention will be described in detail with reference to the drawings. In the drawings used in the embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted as much as possible.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of a radio system according to Embodiment 1 of the present invention. A wireless system 100 illustrated in FIG. 1 includes a wireless transmission device 101 and a wireless reception device 151. The radio transmission apparatus 101 generates a modulation signal generation unit 102 that generates an information signal in which a subcarrier is not arranged at the center frequency of a carrier wave, and a transmission local signal for frequency conversion based on the information signal generated by the modulation signal generation unit 102 A transmission local signal generation unit 103 to generate, a transmission frequency conversion unit 104 to convert the information signal into the frequency of the carrier wave, multiplex the frequency-converted information signal and the transmission local signal, and the multiplexed information signal And an antenna 105 for transmitting the transmission local signal.

  The wireless reception device 151 also includes a reception antenna 152 that receives a carrier wave (information signal) radiated from the wireless transmission device 101, an amplification unit 153 that amplifies the carrier wave (information signal) received by the reception antenna 152, and an amplification A signal distribution unit 154 that distributes the carrier wave (information signal) amplified by the unit 153, an information signal branch unit 155 that extracts the information signal distributed by the signal distribution unit 154, and an information signal that is transmitted to the information signal branch unit 155 Frequency conversion unit 156, a signal processing unit 157 that performs signal processing on an information signal, and a local signal extracted from a carrier wave (information signal) distributed by a signal distribution unit 154 to receive a local signal for frequency conversion And a local signal extraction filter unit 158. Thereby, the reception frequency conversion unit 156 can convert the frequency of the information signal transmitted to the information signal branch unit 155 based on the reception local signal.

  Next, the operation of the wireless system in the first embodiment will be described with reference to the waveforms of each part of the wireless system shown in FIG. FIG. 2 is a waveform diagram showing frequency characteristics of each part of the wireless system shown in FIG. 2A to 2I show the waveform of a signal at a location corresponding to the alphabet described in the wireless system of FIG. 1, where the number of subcarriers is two. In each waveform diagram of FIG. 2, the horizontal axis indicates the frequency and the vertical axis indicates the signal level, but the frequency order and the level order are different in each figure.

  The frequency characteristic of the information signal (A) output from the modulation signal generation unit 102 in FIG. 1 is a characteristic in which multicarrier signals are distributed in two frequency bands as shown in the waveform diagram in FIG. . Further, the frequency characteristic of the transmission local signal (B) generated by the transmission local signal generation unit 103 of FIG. 1 is a frequency characteristic including the phase noise φ as shown in the waveform diagram of FIG. Accordingly, the waveform of the signal (C) that is frequency-converted to a carrier wave by the transmission frequency conversion unit 104 of FIG. 1 and transmitted from the transmission antenna 105 is distributed in two frequency bands as shown in the waveform diagram of FIG. The waveform of the frequency characteristic is obtained by superimposing the transmission local signal of the phase noise φ on the center frequency band of the multicarrier signal.

In this case, the frequency of the carrier wave of the signal (C) transmitted from the transmission antenna 105 is expressed by the following equation (1).
f _RF = f _TXLO x f _M-CDMA (1)
Note that f _RF is the frequency of the information signal frequency-converted to a carrier wave, f _TXLO is the frequency of the transmission local signal generated by the transmission local signal generation unit 103, and f _M-CDMA is the frequency of the information signal.

On the other hand, the frequency component of the transmission local signal generated by the transmission local signal generation unit 103 is
_Assuming that _{sinω LO} t and the phase noise component is Φ ₁ , the frequency component f _TXLO of the transmission local signal generated by the transmission local signal generation unit 103 is expressed by the following equation (2).
f _TXLO = sin (ω _LO −Φ ₁ ) t (2)

Further, when the frequency component f _M-CDMA of the information signal is expressed by the following equation (3), the frequency component of the carrier wave transmitted from the transmission antenna 105 is expressed by equations (2) and (3) in equation (1). By substituting, it is expressed as equation (4).
f _M-CDMA = sinω _M-CDMA t (3)
f _RF (Φ) = sin (ω _LO −Φ ₁ ) t × sin ω _M-CDMA t (4)

When this equation (4) is expanded and arranged, it is expressed as the following equation (5).
f _RF (Φ) = α {cos (ω _LO + ω _M-CDMA −Φ ₁ ) t + cos (ω _LO −ω _M-CDMA −Φ ₁ ) t}
(5)

Here, when the sum frequency component is used as the carrier wave, the equation (5) is expressed as the following equation (6).
f _RF (Φ) = αcos (ω _LO + ω _M-CDMA −Φ ₁ ) t (6)
Α is an integer value when the formula is expanded and arranged.

The carrier wave is radiated from the transmitting antenna 105, and noise is also superimposed on the propagation path while being received by the receiving antenna 152. Assuming that the noise component on the propagation path is Φ ₂ , the frequency component f _RF (Φ ′) of the carrier wave received by the receiving antenna 152 is obtained by adding the noise component Φ ₂ on the propagation path to the above equation (6). It is expressed as the following equation (7).
f _RF (Φ ′) = α cos {ω _LO + ω _M-CDMA − (Φ ₁ + Φ ₂ )} t (7)

  This frequency characteristic is the characteristic at the point (D) in FIG. 1, and is a frequency characteristic like the waveform shown in FIG. 2 (D).

  Then, the signal is amplified by the amplifying unit 153, and the frequency characteristic at the point (E) in FIG. 1 becomes the frequency characteristic as shown in FIG. 2E. The signal distributing unit 154 and the information signal branching unit 155 and the local signal extracting filter unit 158 Distributed to. The frequency characteristic at the point (F) in FIG. 1 distributed to the information signal branch unit 155 becomes the frequency characteristic as shown in FIG. 2 (F), and the point (G) in FIG. 1 distributed to the local signal extraction filter unit 158. The frequency characteristics are as shown in FIG.

Then, the local signal extraction filter unit 158 extracts a local signal. At this time, the local signal (the signal at point (H) in FIG. 1) extracted by the local signal extraction filter unit 158 has frequency characteristics as shown in FIG. 2 (H). The frequency component of the local signal extracted here is expressed as the following equation (8) because the frequency component (sinω _M-CDMA t) of the information signal is removed from the above equation (7).
f _RXLO = α cos {ω _LO − (Φ ₁ + Φ ₂ )} t (8)

  The local signal extraction filter unit 158 has a bandwidth for extracting only the local signal, and the amplitude and group delay characteristics are flat within the band.

The local signal represented by the above equation (8) is input to the reception frequency conversion unit 156 as a reception local signal, and the information signal transmitted through the information signal branch unit 155 is frequency converted. The information signal (signal at point (I) in FIG. 1) frequency-converted by the reception frequency converter 156 has frequency characteristics as shown in FIG. The frequency component f ′ _M-CDMA of the information signal after frequency conversion is expressed by the following equation (9).
f ′ _M-CDMA = f _RF (Φ ′) × f _RXLO (9)

Here, by substituting Equation (7) and Equation (8) into Equation (9), the frequency component f ′ _M-CDMA of the information signal after frequency conversion is expressed as the following Equation (10).
_{f 'M-CDMA = αcos {} ω LO + ω M-CDMA - (Φ 1 + Φ 2)} t × αcos {ω LO - (Φ 1 + Φ 2)} t (10)

Here, when formula (10) is developed and arranged, the frequency component f ′ _M-CDMA of the information signal after frequency conversion is expressed as the following formula (11).
f ′ _M-CDMA = β {cos (2ω _LO + ω _M-CDMA −2 (Φ ₁ + Φ ₂ )) t + cosω _M-CDMA t}
(11)

Furthermore, when the difference frequency component is used as the frequency-converted information signal, the equation (11) is expressed as the equation (12).
f ′ _M-CDMA = βcosω _M-CDMA t (12)
Note that β is an integer value when the formula is expanded and arranged.

As can be seen from Equation (12) above, the information signal after frequency conversion represented by Equation (12) does not include the phase noise component Φ ₁ of the local signal and the noise component Φ ₂ on the propagation path. In other words, the phase noise of the local signal and the noise on the propagation path are canceled. Although the single conversion configuration has been described in the wireless system of the first embodiment, it is needless to say that the present invention is applied even if a direct conversion configuration or the like is used.

  As described above, according to the radio system in the first embodiment, in the radio transmission apparatus, the information signal in which the subcarrier is not arranged at the center frequency of the carrier wave and the transmission local signal for frequency conversion are arranged at the center frequency of the carrier wave. In addition, by generating and transmitting a multiplexed signal obtained by multiplexing these signals, the transmission local signal can be used as the reception local signal without widening the transmission bandwidth, so that phase noise can be canceled. It becomes. Further, since the transmission local signal is used as the reception local signal, it is not necessary to provide a reception local signal generation unit, and as a result, the configuration of the wireless reception device can be reduced in size and simplified.

<Embodiment 2>
FIG. 3 is a block diagram showing the configuration of the radio reception apparatus according to Embodiment 2 of the present invention. In FIG. 3, elements denoted by the same reference numerals as those in FIG. 1 indicate the same elements as those illustrated in FIG. 1. Therefore, the description of these elements is omitted, and the configuration and operation of the different elements will be described.

  The wireless reception device 351 of the second embodiment shown in FIG. 3 receives the received signal for detecting the signal level of the information signal transmitted through the information signal branch unit 155 to the wireless reception device 151 of the first embodiment shown in FIG. A level detection unit 352 and a variable amplification unit 353 that varies the signal level in accordance with the level of the reception signal detected by the reception signal level detection unit 352 are added.

  In the wireless reception device 351 of FIG. 3, when the reception signal level detection unit 352 detects the signal level of the information signal transmitted through the information signal branch unit 155 whose level has been changed on the propagation path, the reception signal level detection unit 352 detects A level fluctuation follow-up signal corresponding to the signal level is sent to the variable amplifier 353.

  On the other hand, since the received local signal is superimposed on the information signal and propagates through the propagation path as a carrier wave, there is a fluctuation equivalent to the level fluctuation on the propagation path of the information signal transmitted through the information signal branch unit 155. Therefore, the received local signal whose level is changed on the propagation path is input to the variable amplifying unit 353. At this time, the variable amplifying unit 353 adjusts the gain in accordance with the level variation tracking signal that follows the level variation transmitted from the reception signal level detection unit 352.

  As described above, according to the radio reception apparatus in the second embodiment, the level fluctuation received on the propagation path by the carrier wave on which the reception local signal and the information signal are superimposed is detected and corresponds to the level detected by the reception signal level detection unit 352. By changing the signal level by the variable amplification unit 353, the reception local signal level input to the reception frequency conversion unit 156 can be maintained at a constant level.

<Embodiment 3>
FIG. 4 is a block diagram showing the configuration of the radio reception apparatus according to Embodiment 3 of the present invention. The wireless reception device 451 of the fourth embodiment shown in FIG. 4 linearly varies the phase of the received local signal extracted by the local signal extraction filter unit 158 with respect to the wireless reception device 351 of the second embodiment shown in FIG. And an amplifying unit 452 for keeping the output level constant is added. Therefore, only the configuration and operation of that part will be described, and redundant description will be omitted.

  FIG. 5 is a characteristic diagram showing the phase relationship with respect to the received local signal input level of the variable amplifying unit 353 shown in FIG. Therefore, the operation of the radio reception apparatus according to Embodiment 3 will be described with reference to FIGS. 4 and 5.

  When the input level of the received local signal is high, the variable amplifying unit 353 performs linear fluctuation without distortion as in the characteristics in the linear region shown in FIG. However, when the input level of the received local signal is lowered as in the characteristic below point X in FIG. 5, distortion occurs below a certain input level point (see characteristics in the distortion generation region in FIG. 5).

At this time, when the phase noise component generated in the distortion of the X point to [Phi _3, receives the above-mentioned formula is the frequency component f _RXLO of a local signal (8) can be expressed as the following equation (13).
f _RXLO = α cos {ω _LO − (Φ ₁ + Φ ₂ + Φ ₃ )} t (13)

As can be seen from the equation (13), the phase noise component Φ ₃ generated by the distortion cannot be canceled, and as a result, the transmission characteristics deteriorate. Therefore, in radio receiving apparatus 451 according to the third embodiment, an amplification unit 452 is installed on the output side of local signal extraction filter unit 158, and the level of the received local signal input to variable amplification unit 353 is pre-amplified, Is not distorted, that is, is amplified so as to be in the linear region shown by the point X or higher in FIG.

  Thus, according to radio receiving apparatus 451 in the third embodiment, the received local signal level input to variable amplification section 353 is amplified, and variable amplification section 353 is set to an input level that does not cause distortion in the phase. Thus, the phase of the received local signal is linearly varied, and the signal level input to the received frequency converter 156 can be kept constant without distortion.

  In the present invention, the phase noise between the wireless transmission device and the wireless reception device can be canceled by using the transmission local signal for frequency conversion as it is as the reception local signal, so that the versatility is small and low cost. It can be effectively used as a wireless system, a wireless receiving device, and a wireless communication device.

1 is a block diagram showing a configuration of a wireless system according to Embodiment 1 of the present invention. Waveform diagram showing frequency characteristics of each part of the wireless system shown in FIG. FIG. 3 is a block diagram showing a configuration of a radio reception apparatus according to Embodiment 2 of the present invention. FIG. 3 is a block diagram showing a configuration of a wireless reception device according to Embodiment 3 of the present invention. FIG. 4 is a characteristic diagram showing the phase relationship with respect to the received local signal input level of the variable amplifying unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Radio system 101 Radio transmission apparatus 102 Modulation signal generation part 103 Transmission local signal generation part 104 Transmission frequency conversion part 105 Transmission antenna 151,351,451 Wireless reception apparatus 152 Reception antenna 153 Amplification part 154 Signal distribution part 155 Information signal branch part 156 Reception frequency conversion unit 157 Signal processing unit 158 Local signal extraction filter unit 352 Reception signal level detection unit 353 Variable amplification unit 452 Amplification unit

Claims (6)

An information signal in which no subcarrier is arranged at the center frequency of the carrier wave and a transmission local signal for frequency conversion are arranged in the vicinity of the center frequency of the carrier wave, and a multiplexed signal obtained by multiplexing the information signal and the transmission local signal is A wireless transmission device for generating and transmitting;
A radio reception apparatus that receives the multiplexed signal transmitted from the radio transmission apparatus, separates and extracts the information signal and the transmission local signal from the multiplexed signal, and uses the extracted transmission local signal as a reception local signal When,
A wireless system comprising: A wireless transmission device applied to a wireless system that transmits information signals using subcarriers,
A modulated signal generator for generating an information signal in which no subcarrier is arranged at the center frequency of the carrier;
A transmission local signal generation unit that generates a transmission local signal for frequency conversion based on the information signal generated by the modulation signal generation unit;
A transmission frequency converter that converts the information signal into a carrier frequency and multiplexes the information signal frequency-converted into the carrier and the transmission local signal;
A radio transmission apparatus comprising: an antenna that transmits the multiplexed information signal and the transmission local signal. A wireless reception device that receives a multiplexed signal in which an information signal in which a subcarrier is not arranged at the center frequency of a carrier wave and a transmission local signal for frequency conversion are multiplexed from a wireless transmission device,
An amplification unit that receives and amplifies the multiplexed signal transmitted from the wireless transmission device;
A signal distribution unit that distributes the multiplexed signal amplified by the amplification unit;
An information signal branch unit for extracting an information signal from the multiplexed signal distributed by the signal distribution unit;
A local signal extraction filter unit that extracts a local signal from the multiplexed signal distributed by the signal distribution unit to obtain a received local signal for frequency conversion;
A reception frequency converting unit that converts a frequency of an information signal transmitted through the information signal branch unit based on the received local signal;
A signal processing unit for signal processing the information signal;
A radio receiving apparatus comprising: Furthermore, a received signal level detection unit that detects a signal level of the received signal by an information signal transmitted through the information signal branch unit;
A variable amplifying unit that varies the signal level of the received local signal corresponding to the level of the received signal detected by the received signal level detecting unit;
The wireless reception device according to claim 3, further comprising:   The radio reception apparatus according to claim 4, further comprising an amplifying unit that linearly varies the phase of the received local signal extracted by the local signal extraction filter unit and holds the output level constant.   A wireless communication device comprising: the wireless transmission device according to claim 2; and the wireless reception device according to any one of claims 3 to 5.

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