JP4486008B2 - Receiver - Google Patents

Description

  The present invention relates to a receiving technique, and more particularly to a receiving apparatus that receives signals using a plurality of antennas.

  An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. In order to receive an OFDM-modulated signal with diversity, the following processing is executed. The receiving apparatus performs FFT (Fast Fourier Transform) on each of the signals received by the plurality of antennas, and outputs a frequency domain signal, that is, a signal using a plurality of subcarriers. The receiving apparatus synthesizes signals received by a plurality of antennas while performing weighting in units of subcarriers. In general, AGC (Automatic Gain Control) is executed before the FFT.

The AGC performs control so that the intensity of a signal obtained by synthesizing the received signal and the thermal noise component generated by the receiving device is constant. For this reason, when the signal received by any one of the plurality of antennas has a low intensity, if the AGC amplifies the signal, the thermal noise component may increase. As a result, the thermal noise component of the synthesized signal is also increased, and there is a possibility that the characteristics are deteriorated as compared with the case where the synthesis is not performed. In order to solve this, the thermal noise component of the entire band is measured for the signals received at each of the plurality of antennas, and the values of the measured thermal noise components are reflected to be received by the plurality of antennas. Techniques for synthesizing signals have been proposed (see, for example, Patent Document 1).
JP 2004-112155 A

  However, when the receiving apparatus receives a wideband signal, there may be a portion where the signal strength is large and a portion where the signal strength is small due to the influence of frequency selective fading. That is, if there are subcarriers with high signal strength, there are also subcarriers with low signal strength. Therefore, when measuring the thermal noise component of the signal received by each of the plurality of antennas, even if the thermal noise component in the entire band is measured, the thermal noise component suitable for synthesis of the broadband signal is not obtained.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a receiving apparatus that improves diversity gain for a multicarrier signal whose signal strength is not constant within a band.

  In order to solve the above problems, a receiving apparatus according to an aspect of the present invention includes a plurality of multicarrier signals respectively received by a plurality of antennas, and a plurality of known signals each included in at least one carrier. An input unit for inputting a multicarrier signal, an amplification unit for adjusting a gain for each of a plurality of multicarrier signals input at the input unit, and amplifying a plurality of multicarrier signals by each adjusted gain; From a known signal included in each of a plurality of amplified multicarrier signals, a first estimation unit that estimates a transmission path characteristic for a carrier including the known signal, and a transmission path characteristic estimated in the first estimation unit, A second estimation unit for estimating a noise component for each carrier including a known signal; A third estimator for estimating a noise component corresponding to each carrier in the multicarrier signal from the noise component estimated in step 3, and a plurality of multicarrier signals on the basis of the noise component estimated in the third estimator. And a synthesis unit that synthesizes the unit.

  According to this aspect, the noise component is derived in units of carriers, and the signals are synthesized while using the derived noise components, so that the influence of noise during synthesis can be suppressed in units of carriers and reception characteristics are improved. it can.

  A second estimation unit that generates a reference signal for a carrier including a known signal by performing statistical processing on at least a part of the transmission path characteristics estimated by the first estimation unit; A derivation unit for deriving a noise component for a carrier including a known signal based on a difference between the reference signal generated in the generation unit and the transmission path characteristic estimated in the first estimation unit while associating the carrier; May be provided. In this case, since the reference signal is derived in units of one carrier, the reference signal corresponding to the transmission path characteristics can be derived.

  The third estimation unit may estimate the noise component corresponding to each carrier in the multicarrier signal by interpolating the noise component for the carrier including the known signal. In this case, since the noise component derived from a predetermined subcarrier is expanded into a multicarrier signal, the noise component for each of the multicarrier signals can be derived even when a known signal is included in some carriers. .

  The synthesizer derives a channel coefficient corresponding to each carrier in the multicarrier signal from the channel characteristics estimated in the first estimator, and thereby sets a weight coefficient for each of the plurality of multicarrier signals in units of carriers. The weighting coefficient is corrected with the noise component while associating the calculating unit to be calculated, the weighting factor of the carrier unit calculated by the calculating unit with the noise component estimated by the third estimating unit, and based on the corrected weighting factor In addition, an execution unit that combines a plurality of multicarrier signals in units of carriers may be provided. In this case, when synthesizing a plurality of multicarrier signals, the synthesis is performed while reflecting the noise component, so that the influence of noise at the time of synthesis can be reduced.

  A selection unit configured to input a plurality of multicarrier signals respectively received by a plurality of antennas, select at least two of the plurality of multicarrier signals, and output the selected at least two multicarrier signals to the input unit; Further, it may be provided. In this case, since at least two of the plurality of multicarrier signals received by the plurality of antennas are processed, the circuit scale can be reduced.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the diversity gain with respect to the multicarrier signal whose intensity | strength is not constant within a band can be improved.

  Before describing the present invention in detail, an outline will be described. An embodiment of the present invention relates to a receiving apparatus compatible with the ISDB-T system which is one of terrestrial digital television standards. The ISDB-T method uses an OFDM (Orthogonal Frequency Division Multiplexing) modulation method which is one of multicarrier modulations. Here, “5617” subcarriers are used. The receiving apparatus synthesizes the signals received by a plurality of antennas while weighting them. That is, maximum ratio combining diversity is performed. At this time, the receiving apparatus amplifies the received signal by AGC before the synthesis. As described above, the thermal noise component included in the received signal is also amplified by the AGC amplification. The receiving apparatus according to the present embodiment operates as follows in order to suppress the influence of the thermal noise component when executing the maximum ratio combining diversity.

  The receiving device converts signals received by a plurality of antennas into a frequency domain. The receiving apparatus extracts the subcarrier signal in which the pilot signal is arranged from the subcarrier signals included in the signal converted to the frequency domain, and performs subcarrier unit based on the extracted subcarrier signal. The transmission path characteristics are estimated (hereinafter, the transmission path characteristics estimated for each subcarrier are referred to as “transmission path coefficients”). Further, statistical processing, for example, filtering processing is performed on the transmission path coefficient in the frequency direction. That is, the noise component of the subcarrier on which the pilot signal is arranged is suppressed. Here, the number of subcarriers used in the statistical processing is determined to be a small value in consideration of frequency selective fading. This is because, generally, under a frequency selective fading environment, the transmission path characteristics greatly fluctuate even at a short frequency interval.

  The receiving apparatus estimates the thermal noise component for the subcarrier by calculating the difference between the statistically processed transmission path coefficient and the estimated transmission path coefficient for one subcarrier. The thermal noise component thus estimated is interpolated in the frequency direction, and thermal noise components for all subcarriers are derived. Moreover, the above process is performed also on the signal received by the other antenna. The receiving apparatus performs maximum ratio combining diversity on signals received by a plurality of antennas while reflecting a thermal noise component.

  FIG. 1 shows a configuration of a receiving apparatus 100 according to an embodiment of the present invention. The receiving apparatus 100 includes a first antenna 10a, a second antenna 10b, an Nth antenna 10n, a selection unit 12, and an RF unit 14 that are collectively referred to as an antenna 10, a first RF unit 14a, a second RF unit 14b, and an AGC unit 16. A first AGC unit 16a, a second AGC unit 16b, a first FFT unit 18a, a second FFT unit 18b, and a first transmission line characteristic estimation unit 20a, A second transmission line characteristic estimation unit 20b, a first interpolation unit 22a collectively referred to as an interpolation unit 22, a second interpolation unit 22b, a first weighting unit 24a and a second weighting unit 24b collectively referred to as a weighting unit 24; A first multiplier 26a, a second multiplier 26b, collectively referred to as a multiplier 26, a first power calculator 28a, a second power calculator 28b, collectively referred to as a power calculator 28, and a first, collectively referred to as a multiplier 30. Multiplication unit 3 a, a second multiplier 30b, an adder 32, an adder 34, a divider 36, a noise estimator 38, and a first noise estimator 38a, a second noise estimator 38b, and a correction value calculator 40. A first correction value calculation unit 40a, a second correction value calculation unit 40b, and a control unit 42. The noise estimation unit 38 includes a time direction interpolation unit 44, a frequency direction filter unit 46, a derivation unit 48, a frequency direction interpolation unit 50, a coefficient holding unit 52, and a multiplication unit 54.

  The antenna 10 receives a radio frequency signal via a transmission path. Here, the radio frequency signal is a multicarrier signal. In addition, a pilot signal is arranged on at least one subcarrier among the multicarrier signals. The pilot signal is a signal having a known value, and the subcarrier on which the pilot signal is to be arranged is defined in advance. FIG. 2 shows a configuration of a multicarrier signal received by the antenna 10. The horizontal axis in the figure indicates “subcarrier number”, and the vertical axis in the figure indicates “symbol number”.

  The “subcarrier number” is a number assigned to identify a subcarrier. For example, a subcarrier number having a small value is assigned to a subcarrier having a low frequency. The “symbol number” is a number assigned to identify the order of input symbols. For example, a symbol number having a smaller value is assigned to a previously input symbol. “P” in the figure indicates the pilot signal described above, and “D” in the figure indicates a data signal. As shown in the figure, in the symbol number “0”, pilot signals are arranged on discrete subcarriers as in subcarrier numbers “0” and “12”.

  In addition, in the symbol number “1”, pilot signals are arranged like the subcarrier numbers “3” and “15”. That is, if the symbol numbers are different, the subcarrier on which the pilot signal is to be arranged is shifted. Further, in the symbol number “4”, pilot signals are arranged like the subcarrier numbers “0” and “12”. This arrangement is the same as in the case of symbol number “0”, and the subcarriers on which pilot signals are to be arranged periodically become the same subcarriers. Returning to FIG.

  The selection unit 12 receives a plurality of multicarrier signals respectively received by the plurality of antennas 10 and selects two of the plurality of multicarrier signals. Here, the strength of a plurality of multicarrier signals respectively received by the plurality of antennas 10 is measured, and two subcarrier signals are selected according to the measured strength. Further, the selection unit 12 outputs at least two selected multicarrier signals.

  The RF unit 14 converts the frequency of the received signal from a radio frequency to a baseband. Therefore, the RF unit 14 has a tuner function, and by fixing the tuner reception frequency to a predetermined value, the RF unit 14 uses the received signal to program a channel corresponding to the broadcast station to be viewed. Select. Note that “program” refers to a program that is being broadcast, but here the contents thereof are also included. That is, the program may indicate broadcast audio, broadcast video, and combinations thereof.

  The AGC unit 16 adjusts the gain for each of the plurality of multicarrier signals input from the RF unit 14, and amplifies the plurality of multicarrier signals by the adjusted gains. Since the AGC unit 16 may be realized by a known technique, the description thereof is omitted here. Note that the first AGC unit 16a and the second AGC unit 16b perform gain adjustment independently. Therefore, in general, both gains are different.

  The FFT unit 18 performs FFT on the multicarrier signal from the AGC unit 16. As a result, the signal frequency-converted to baseband in the RF unit 14 is converted into a frequency domain signal. As described above, the subcarrier signal “5617” is used for the frequency domain signal.

  The transmission path characteristic estimation unit 20 estimates transmission path coefficients for subcarriers including a pilot signal from pilot signals included in each of a plurality of multicarrier signals. For this purpose, the transmission path characteristic estimation unit 20 extracts subcarriers in which pilot signals are arranged from the multicarrier signal. Here, since the subcarrier in which the pilot signal is arranged is defined in advance, the transmission path characteristic estimation unit 20 performs extraction while using the definition. Further, the channel coefficient estimation is performed using the extracted signal value and the pilot signal value in the subcarrier. Transmission path estimation may be performed by a known technique, for example, by complex multiplication of the inverse value of the pilot signal and the value of the signal at the extracted subcarrier. The transmission line characteristic estimation unit 20 outputs the estimated transmission line coefficient and outputs the input multicarrier signal.

  The noise estimator 38 includes noise included in each of a plurality of multicarrier signals amplified by the AGC unit 16 with respect to the subcarriers including the pilot signal from the channel coefficient estimated by the channel characteristic estimator 20. Estimate components. Although the details of the estimation process will be described later, the first noise estimator 38a performs estimation on the transmission path coefficient from the first transmission path characteristic estimator 20a, and the second noise estimator 38b Estimation is performed on the transmission path coefficient from the characteristic estimation unit 20b. Both processes are the same.

  The time direction interpolation unit 44 interpolates periodically appearing transmission path coefficients in units of one subcarrier. Here, details of the processing will be described with reference to FIG. Note that the subcarriers to be processed are subcarriers in which pilot signals are arranged at any timing. That is, subcarrier numbers “0”, “3”, “6”, “9”, “12”, and the like. Other subcarriers are not processed in the time direction interpolation unit 44. The processing on the subcarrier of the subcarrier number “0” is performed by, for example, interpolating the transmission path coefficient at the symbol number “0” and the transmission path coefficient at the symbol number “4”, thereby performing the symbol number “1”. To derive the transmission line characteristic at “3”.

  Here, linear interpolation is used for interpolation, but is not limited thereto, and a predetermined approximate expression may be used. Further, the time direction interpolation unit 44 may perform extrapolation while using transmission path coefficients with other symbol numbers. Further, the time direction interpolation unit 44 may use the transmission path coefficient at the symbol number “0” as it is for the transmission path coefficient at the symbol number “1” or the like. With the above processing, continuous transmission path coefficients are derived in the time direction for the subcarriers in which pilot signals are arranged. Returning to FIG.

  The frequency direction filter unit 46 performs statistical processing on the transmission path coefficient while processing the subcarriers processed in the time direction interpolation unit 44 as processing targets. Note that the statistical processing is executed for transmission line coefficients at the same timing. Here, details of the processing will be described with reference to FIG. For a predetermined symbol number, for example, the symbol number “4”, the channel coefficients for the subcarrier numbers “0”, “3”, “6”, “9”, “12” have already been derived. The frequency direction filter unit 46 performs statistical processing with the three transmission path coefficients as one combination.

  That is, subcarrier numbers “0”, “3”, and “6” are combined into one combination, subcarrier numbers “3”, “6”, and “9” are combined into one combination, and subcarrier number “6” is combined. , “9”, “12” are one combination. In the statistical process, the transmission path coefficients with three subcarrier numbers are added while being weighted. Here, the statistically processed channel coefficient is used as a reference signal for the channel coefficient at the center subcarrier number among the three subcarrier numbers. For example, the reference signal for the subcarrier number “3” is generated by statistical processing on the transmission path coefficients with the subcarrier numbers “0”, “3”, and “6”. Through the above processing, reference signals for subcarriers in which pilot signals are arranged are generated.

  The deriving unit 48 calculates the difference between the transmission path coefficient from the time direction interpolation unit 44 and the reference signal from the frequency direction filter unit 46 in units of subcarriers. Furthermore, the deriving unit 48 calculates the absolute value of the calculated difference. Finally, the deriving unit 48 derives the calculated absolute value as a noise component for the carrier including the pilot signal. Here, the absolute value is called a “noise component”.

  The frequency direction interpolation unit 50 derives a noise component corresponding to each subcarrier in the multicarrier signal from the noise component derived by the deriving unit 48. Specifically, the frequency direction interpolation unit 50 derives a noise component for each subcarrier included in the multicarrier signal by interpolating the noise component for the subcarrier including the pilot signal. The interpolation is performed in the same manner as the interpolation in the time direction interpolation unit 44. Here, the noise component generated by the interpolation is also referred to as “noise component”.

  The multiplication unit 54 multiplies the noise component by the coefficient held in the coefficient holding unit 52. In general, such a coefficient is defined as a value between “0” and “1”. The correction value calculator 40 calculates the square of the multiplication result in the multiplier 54 and calculates the reciprocal of the square value. Here, the reciprocal of the square value is the correction value.

  The interpolation unit 22 interpolates transmission path coefficients that should appear periodically, with one subcarrier as a unit. Similar to the time direction interpolation unit 44, the interpolation unit 22 interpolates the transmission path coefficient in the time direction. Through the above processing, continuous channel coefficients are derived in the subcarriers in which pilot signals are arranged. Further, the interpolation unit 22 interpolates the transmission path coefficient in the frequency direction, similarly to the frequency direction interpolation unit 50. The above processing corresponds to deriving transmission path coefficients corresponding to the respective subcarriers included in the multicarrier signal from the transmission path coefficients derived by the transmission path characteristic estimation unit 20. Also, this is to calculate the transmission path coefficient for each of a plurality of multicarrier signals in units of subcarriers.

  The weighting unit 24 weights the multicarrier signal from the FFT unit 18 using the transmission path coefficient from the interpolation unit 22. The weighting unit 24 performs weighting in units of subcarriers. Note that the complex conjugate value of the transmission path coefficient is used for weighting. Here, the weighting unit 24 performs complex multiplication for weighting.

  The multiplication unit 26 multiplies the multiplication result in the weighting unit 24 and the correction value from the correction value calculation unit 40 in units of subcarriers. The above processing corresponds to correcting the transmission path coefficient with the noise component while associating the transmission path coefficient from the interpolation unit 22 with the correction value. The adder 32 adds the multiplication results from the multiplier 26 in units of subcarriers. This is equivalent to synthesizing a plurality of multicarrier signals in units of subcarriers based on the transmission path coefficient corrected by the multiplier 26.

  The power calculation unit 28 calculates the power of the transmission path coefficient from the interpolation unit 22 in units of subcarriers. The multiplier 30 multiplies the power value from the power calculator 28 and the correction value from the correction value calculator 40 in units of subcarriers. This corresponds to correcting the power value by the noise component. The adder 34 adds the multiplication results from the multiplier 30 in units of subcarriers. The division unit 36 divides the addition result from the addition unit 32 by the multiplication result from the addition unit 34 in units of subcarriers. Here, the processing from the weighting unit 24 to the dividing unit 36 corresponds to maximum ratio combining diversity. In the above processing, a plurality of multicarrier signals are synthesized in units of subcarriers based on the noise component.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a reception function loaded in the memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIGS. 3A to 3D illustrate operations that are comparison targets of operations in the receiving apparatus 100. FIG. 3A shows the waveform of a signal received by the antenna 10. The horizontal axis indicates time, and the vertical axis indicates signal intensity. As shown, in addition to the waveform of the received signal, the waveform of the noise component is also shown. The intensity of the received signal varies with time. FIG. 3B shows the signal strength at a predetermined timing in the waveform shown in FIG. Here, the first antenna 10a and the second antenna 10b are indicated as “antenna 1” and “antenna 2”, the intensity of the received signal is indicated as “signal level”, and the intensity of the noise component is indicated as “noise level”. The vertical axis represents the signal strength, and the longer the length of the arrow, the stronger the signal strength.

  FIG. 3C shows the intensity of the signal amplified by the AGC unit 16. In FIG. 3B, the signal level at the antenna 2 is smaller than the signal level at the antenna 1. However, since the gain of the AGC unit 16 for the antenna 2 is larger than the gain of the AGC unit 16 for the antenna 1, the signal levels of both are equal in FIG. However, since the gain as described above is set, the noise level at the antenna 2 is larger than the noise level at the antenna 1.

  FIG. 3D shows the intensity of the signal when the two signals in FIG. 3C are combined. Here, as shown in FIG. 1, the synthesis is performed without considering the influence of the noise component. The synthesis of the two signals increases the signal level but also increases the noise level. Depending on the increased noise level, the reception characteristics may be deteriorated. In order to solve such a problem, the present invention considers the influence of noise on a subcarrier basis.

  FIG. 4 shows the configuration of the first transmission line characteristic estimation unit 20a. The first transmission path characteristic estimation unit 20 a includes a pilot signal extraction unit 60 and a complex division unit 62. The pilot signal extraction unit 60 extracts a pilot signal from the multicarrier signal. The extraction process corresponds to selecting “P” from the multicarrier signal of FIG. The complex division unit 62 divides the pilot signal extracted in the pilot signal extraction unit 60 by the internally generated pilot symbol. The result of division corresponds to the transmission path coefficient in the subcarrier in which the pilot signal is arranged. The complex division unit 62 outputs the derived transmission line coefficient.

  FIG. 5 shows the configuration of the frequency direction filter unit 46. The frequency direction filter unit 46 includes a first delay unit 64a, a second delay unit 64b, which are collectively referred to as a delay unit 64, and a first multiplier unit 66a, a second multiplier unit 66b, and a third multiplier unit 66c, which are collectively referred to as a multiplier unit 66. , A first coefficient holding unit 68a, a second coefficient holding unit 68b, a third coefficient holding unit 68c, an adding unit 70, and a reset unit 72, which are collectively referred to as a coefficient holding unit 68.

  The delay unit 64 delays the input signal. Here, transmission path coefficients with subcarrier numbers “0”, “3”, “6”, “9”, and “12” are sequentially input. When the symbol changes, the reset unit 72 resets the signal input to the delay unit 64. The coefficient holding unit 68 holds a coefficient. Here, it is assumed that the coefficient held in the second coefficient holding unit 68b is larger than the coefficients held in the first coefficient holding unit 68a and the third coefficient holding unit 68c. Multiplier 66 multiplies the transmission path coefficient and the coefficient. The multiplication is assumed to be complex multiplication. The adder 70 adds the multiplication results from the multiplier 66. The addition result corresponds to the aforementioned reference signal. Further, the subcarrier number in the multiplication result in the second multiplication unit 66b is a subcarrier number corresponding to the reference signal. Thus, by reducing the number of transmission path coefficients to be processed, it is possible to cope with changes in transmission path characteristics at short frequency intervals due to frequency selective fading. Moreover, the influence of noise can be reduced by adding a plurality of transmission path coefficients.

  FIG. 6 shows the configuration of the derivation unit 48. The derivation unit 48 includes a subtraction unit 74 and an absolute value calculation unit 76. The subtracting unit 74 subtracts the reference signal from the frequency direction filter unit 46 in FIG. 1 from the transmission path coefficient from the time direction interpolation unit 44 in FIG. 1 while associating the subcarrier numbers. This corresponds to detection of a difference between the transmission path coefficient and the reference signal. Further, since both the channel coefficient and the reference signal are indicated by vectors, the subtraction in the subtracting unit 74 is executed by vector calculation. The absolute value calculator 76 calculates the absolute value of the subtraction result obtained by the subtractor 74. The subtraction result corresponds to a noise component for a carrier including a pilot signal.

  FIG. 7 shows a configuration of the first correction value calculation unit 40a. The first correction value calculation unit 40 a includes a square unit 78 and an inverse number derivation unit 80. The square unit 78 calculates the square of the multiplication result in the multiplication unit 54 of FIG. The square calculation is performed in units of subcarriers. The reciprocal deriving unit 80 derives the reciprocal of the square value calculated by the square unit 78. The reciprocal of the square value corresponds to the correction value.

  FIG. 8 shows the configuration of the first interpolation unit 22a. The first interpolation unit 22a includes a buffer unit 82, a time direction interpolation unit 84, and a frequency direction interpolation unit 86. The buffer unit 82 accumulates the transmission channel coefficient from the transmission channel characteristic estimation unit 20. The accumulation is performed in order to execute interpolation in the time direction in the time direction interpolation unit 84 described later. The time direction interpolation unit 84 performs time direction interpolation on the transmission path coefficients accumulated in the buffer unit 82. Interpolation is performed in the same manner as the time direction interpolation unit 44, and thus the description thereof is omitted here. The frequency direction interpolation unit 86 interpolates the transmission path coefficient interpolated in the time direction by the time direction interpolation unit 84 in the frequency direction. Interpolation is performed in the same manner as the frequency direction interpolation unit 50, and thus description thereof is omitted. Finally, the frequency direction interpolation unit 86 outputs a channel coefficient for each of the plurality of multicarrier signals.

  FIGS. 9A to 9D show signals processed in the receiving apparatus 100. FIG. FIG. 9A shows the transmission path coefficient derived in the transmission path characteristic estimation unit 20 and the transmission path coefficient in the subcarrier corresponding to the pilot signal. The horizontal axis indicates the frequency, and the vertical axis indicates the amplitude. A noise level is also shown together with the transmission path coefficient. FIG. 9B shows transmission line coefficients before and after the frequency direction filter unit 46. The transmission line coefficient before the frequency direction filter unit 46 corresponds to the transmission line coefficient shown in FIG. Further, the transmission path coefficient after the frequency direction filter unit 46 corresponds to the noise component of the transmission path coefficient before the frequency direction filter unit 46 is reduced.

  FIG. 9C shows the noise component output from the derivation unit 48. This corresponds to a value obtained by subtracting the channel coefficient after the frequency direction filter unit 46 from the channel coefficient before the frequency direction filter unit 46 shown in FIG. 9B for each subcarrier. FIG. 9D shows the channel coefficients interpolated in the frequency direction by the frequency direction interpolation unit 50. The value of the channel coefficient in one subcarrier is copied from one subcarrier in which the pilot signal is arranged to an adjacent subcarrier in which the pilot signal is arranged. Here, between the subcarriers in which the two pilot signals are arranged, the value of the transmission path coefficient corresponding to the smaller subcarrier number is used for copying.

  The operation of the receiving apparatus 100 having the above configuration will be described. The selection unit 12 selects two of the antennas 10. The AGC unit 16 amplifies the multicarrier signals input by the two selected antennas 10 respectively. The FFT unit 18 converts the amplified multicarrier signal into a signal in the frequency domain, that is, a subcarrier unit. The transmission path characteristic estimation unit 20 selects a pilot signal from among the multicarrier signals, and estimates a transmission path coefficient for the pilot signal. The time direction interpolation unit 44 interpolates the estimated transmission path coefficient in the time direction. The frequency direction filter unit 46 statistically processes the transmission path coefficient between subcarriers in which pilot signals are arranged, and derives a reference signal.

  The deriving unit 48 derives a noise component from the transmission path coefficient and the reference signal. The frequency direction interpolation unit 50 derives a noise component for each of the multicarrier signals by interpolating the noise component in the frequency direction. The multiplier 54 multiplies the noise component by a coefficient. After calculating the square value of the multiplication result, the correction value calculation unit 40 derives the reciprocal and sets it as the correction value.

  The interpolation unit 22 derives transmission path coefficients corresponding to each of the multicarrier signals by interpolating the transmission path coefficients in the time direction and the frequency direction. The weighting unit 24 weights the multicarrier signal with the complex conjugate value of the transmission path coefficient in units of subcarriers. The multiplication unit 26 corrects the result weighted by the weighting unit 24 with the correction value from the correction value calculation unit 40. The adder 32 adds the results corrected by the multiplier 26.

  The power calculator 28 calculates the power of the transmission path coefficient from the interpolator 22. The multiplier 30 multiplies the power value from the power calculator 28 and the correction value from the correction value calculator 40. The adder 34 adds the multiplication results from the multiplier 30. The division unit 36 divides the addition result from the addition unit 32 by the multiplication result from the addition unit 34.

  According to the embodiment of the present invention, noise components are derived in units of subcarriers, and signals are synthesized while using the derived noise components, so that the influence of noise during synthesis is suppressed in units of subcarriers. it can. Further, since the influence of noise is suppressed in units of subcarriers, reception characteristics can be improved. In addition, since the reference signal is derived in units of one subcarrier, the reference signal corresponding to the transmission path characteristics can be derived. In addition, since the reference signal is derived in units of one subcarrier, the transmission path characteristics can be reflected in detail. In addition, since the noise component derived from a predetermined subcarrier is expanded into a multicarrier signal, the noise component for each of the multicarrier signals can be derived even when a known signal is included in some subcarriers. . Further, when combining a plurality of multi-carrier signals, since the combining is performed while reflecting the noise component, the influence of noise during the combining can be reduced. In addition, since at least two of a plurality of multicarrier signals received by a plurality of antennas are processed, the circuit scale can be reduced.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the receiving apparatus 100 receives a digital television broadcast program. However, the present invention is not limited to this. For example, the receiving apparatus 100 may receive a radio broadcast program, and may further receive a signal in a wireless LAN using an OFDM modulation scheme. An example of the latter is a wireless LAN in the IEEE 802.11a standard. At this time, since the arrangement of pilot signals is different from that in the embodiment, the processing content may be changed according to the arrangement. According to this modification, the receiving device 100 can be applied to various communication systems and broadcast systems. In addition, the effect by this invention becomes large, so that there are many subcarriers. That is, it is sufficient that the OFDM modulation method is used.

  The frequency direction filter unit 46 performs addition of transmission path coefficients while weighting the transmission path coefficients for the three subcarriers to generate a reference signal. However, the present invention is not limited to this. For example, the frequency direction filter unit 46 may generate the reference signal by averaging transmission path coefficients for a plurality of subcarriers. According to this modification, the processing of the frequency direction filter unit 46 can be simplified. That is, it is only necessary to reduce the noise component included in the transmission path coefficient.

  In the embodiment of the present invention, the frequency direction filter unit 46 is described as a 3-tap filter. However, the present invention is not limited to this. For example, the frequency direction filter unit 46 may be a filter other than three taps. An example of a filter other than three taps is a filter having three or more taps. Further, in the frequency direction filter unit 46, the multiplication unit 66 performs complex multiplication. However, the present invention is not limited to this. For example, the phase component of the input signal may be extracted, and the addition / subtraction operation between the phase component and the real coefficient may be executed. Note that an arctangent is derived for extracting the phase component. According to this modification, various types of filters can be used as the frequency direction filter unit 46. That is, it is only necessary to reduce the noise component included in the transmission path coefficient.

It is a figure which shows the structure of the receiver which concerns on the Example of this invention. It is a figure which shows the structure of the multicarrier signal received with the antenna of FIG. FIGS. 3A to 3D are diagrams illustrating operations to be compared with the operations in the receiving apparatus in FIG. It is a figure which shows the structure of the 1st transmission line characteristic estimation part of FIG. It is a figure which shows the structure of the frequency direction filter part of FIG. It is a figure which shows the structure of the derivation | leading-out part of FIG. It is a figure which shows the structure of the 1st correction value calculation part of FIG. It is a figure which shows the structure of the 1st interpolation part of FIG. FIGS. 9A to 9D are diagrams illustrating signals processed in the receiving apparatus of FIG.

Explanation of symbols

  10 antenna, 12 selection unit, 14 RF unit, 16 AGC unit, 18 FFT unit, 20 transmission path characteristic estimation unit, 22 interpolation unit, 24 weighting unit, 26 multiplication unit, 28 power calculation unit, 30 multiplication unit, 32 addition Unit, 34 addition unit, 36 division unit, 38 noise estimation unit, 40 correction value calculation unit, 42 control unit, 44 time direction interpolation unit, 46 frequency direction filter unit, 48 derivation unit, 50 frequency direction interpolation unit, 52 coefficient holding Part, 54 multiplication part, 100 receiving apparatus.

Claims (5)

In the receiving apparatus that performs weighting by performing interpolation at least in the frequency direction using the transmission path coefficient estimated by the transmission path characteristic estimation unit,
An input unit for inputting a plurality of multicarrier signals each of which is a plurality of multicarrier signals respectively received by a plurality of antennas, and each including a known signal in at least one carrier;
An amplifying unit for adjusting a gain for each of a plurality of multicarrier signals input at the input unit, and amplifying the plurality of multicarrier signals by each adjusted gain;
A first estimation unit that estimates channel characteristics for a carrier including a known signal from known signals included in each of a plurality of multicarrier signals amplified by the amplification unit, and outputs a channel coefficient ;
A second estimator for estimating a noise component for each carrier including a known signal, using the channel coefficient estimated in the first estimator as an input ;
A third estimator for interpolating the noise component estimated in the second estimator in the frequency direction and estimating a noise component corresponding to each carrier in the multicarrier signal;
A receiving apparatus comprising: a combining unit configured to combine a plurality of multicarrier signals in units of carriers based on the noise component estimated in the third estimating unit. The second estimation unit includes
A generating unit that generates a reference signal for a carrier including a known signal by performing statistical processing on at least a part of the channel characteristics estimated in the first estimating unit;
A derivation unit that derives a noise component for a carrier including a known signal based on a difference between the reference signal generated in the generation unit and the transmission path characteristic estimated in the first estimation unit while associating the carrier When,
The receiving apparatus according to claim 1, further comprising:   The third estimation unit estimates a noise component corresponding to each carrier in a multicarrier signal by interpolating a noise component with respect to a carrier including a known signal. The receiving device described. The synthesis unit is
A calculation for calculating a weighting coefficient for each of a plurality of multicarrier signals in units of carriers by deriving a transmission path coefficient corresponding to each carrier in the multicarrier signal from the transmission path characteristics estimated in the first estimation unit. And
The weighting coefficient is corrected with the noise component while associating the weighting coefficient of the carrier unit calculated by the calculating unit with the noise component estimated by the third estimating unit, and based on the corrected weighting coefficients, An execution unit for synthesizing multicarrier signals in units of carriers;
The receiving apparatus according to claim 1, further comprising:   A selection unit that inputs a plurality of multicarrier signals respectively received by a plurality of antennas, selects at least two of the plurality of multicarrier signals, and outputs the selected at least two multicarrier signals to the input unit. The receiving apparatus according to claim 1, further comprising:

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