JP3650334B2 - Digital broadcast receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital broadcast receiving apparatus that receives a transmission wave transmitted by an orthogonal frequency division multiplexing system, and more particularly to a digital broadcast that is suitable for application when receiving a digital transmission wave in a bad reception environment such as mobile reception. The present invention relates to a broadcast receiving apparatus.
[0002]
[Prior art]
In terrestrial broadcasting, digitization is performed in order to realize effective use of SFN (Single Frequency Network), MFN (Multi Frequency Network) and bands. According to this, it is possible to broadcast one program for HDTV and three programs for SDTV using a band of 6 MHz. At the same time, high-quality sound broadcasting and data broadcasting will be realized.
[0003]
In digital broadcasting, video / audio information is compressed by MPEG2, and the compressed video information, audio information, and data information are multiplexed to generate a transport stream (TS). The generated TS signal is transmitted by a digital modulation method.
[0004]
In the case of terrestrial digital broadcasting, COFDM (Coded Orthogonal Frequency Division Multiplexing) is adopted as a transmission method in Europe, and BST-OFDM (Band Segmented Transmission-Orthogonal Frequency Division Multiplexing) method is adopted in Japan. Both are orthogonal frequency division multiplexing methods. (OFDM system) is the basis. The OFDM scheme is a multi-carrier transmission scheme that uses a plurality of carriers at the same time. The carriers are orthogonal to each other and modulated by DQPSK, QPSK, 16QAM, and 64QAM. The number of carriers used is about 1400 to 5600 in domestic terrestrial digital broadcasting, and OFDM modulation and OFDM demodulation are performed by inverse Fourier transform and Fourier transform, respectively. In actual transmitters and receivers, 2K to 8K points of I-DFT (Inverse-Discrete Fourier Transformation) processing and DFT (Discrete Fourier Transformation) processing are used.
[0005]
Unlike satellite broadcasting, terrestrial digital broadcasting generates reflected waves due to obstacles such as buildings and mountains, resulting in ghosts and causing errors in digital modulation signals. For this reason, in the receiver, video and audio signals are broken, and reception quality is significantly deteriorated. In general, signal degradation due to noise can be corrected by error correction if the received signal satisfies the required C / N, and the receiver can reproduce video / audio without error.
[0006]
As described above, in order to absorb the influence of interference caused by ghosts and multipaths, the OFDM system is devised so that a buffer area is provided so that information is not corrupted even if a delayed wave exists. This buffer area is called a guard interval (GI). Since the intersymbol interference does not occur unless the delay time of the delay wave of the received signal exceeds the guard interval time, the error correction circuit can correct it. When the guard interval is exceeded, intersymbol interference occurs and causes an error. The guard interval length is set to 1/4, 1/8, 1/16, 1/32 of the total transmission signal length, which corresponds to about 8 to 250 microseconds.
[0007]
In general, in portable reception and mobile reception in terrestrial broadcasting, a signal digitally modulated by multipath fading or the like deteriorates and an error occurs. The OFDM system adopted for digital broadcasting uses a concatenated code together and incorporates time interleaving to make it a system that is strong against mobile reception and mobile reception. However, the signal may not be corrected even if the above method is used due to severe selective fading.
[0008]
[Problems to be solved by the invention]
As described above, mobile reception or mobile reception has a problem that reception signals deteriorate due to multipath fading or selective fading and cannot be received by mobile reception or mobile reception. Further, even in fixed reception, a signal deteriorates due to multipath, and a problem that reception is impossible occurs.
[0009]
In digital broadcasting, a system having high error correction characteristics is employed in order to effectively use the band. For this reason, in domestic terrestrial digital broadcasting, a transmission rate exceeding 20 Mbps is achieved while being 5.7 MHz. However, if the received signal deteriorates due to interference and the threshold of the reception limit is interrupted, there is a cliff effect that suddenly disappears video and audio. For this reason, even in a reception area that has conventionally been made receivable, sudden reception may be impossible due to the influence of the multipath.
[0010]
For such a problem, antenna diversity receiving by a plurality of antennas has been proposed. FIG. 2 is a configuration diagram of a conventional space diversity system using two antennas.
[0011]
The broadcast wave transmitted from the broadcast station is received by the reception antenna 11a, and the received signal selected by the channel selection unit (tuner) 14a is converted into a digital signal by the analog-digital conversion circuit (ADC) 15a. The received signal converted into the digital signal is OFDM demodulated by the OFDM demodulator 21a and passed to the subsequent decoder 22a. In the decoding part 22a, the reverse process of the encoding performed on the transmission side is performed and output. This output signal is passed to the error rate calculation unit 23 and the selection circuit 24. Similarly, the signal received by the receiving antenna 11b is also selected by the channel selection unit 14b, converted into a digital signal by the analog-digital conversion circuit 15b, OFDM demodulated by the OFDM demodulation unit 21b, and then transmitted to the subsequent decoding unit 22b. Passed. The decoding unit 22 b performs the same decoding process as described above, and the output signal is passed to the error rate calculation unit 23 and the selection circuit 24.
[0012]
The error rate calculator 23 calculates an error rate from the signals received and demodulated in each branch, and sends a control signal to the selection circuit 24 so as to select a branch with few errors. As a result, the selection circuit 24 selects the one with fewer errors, and this is output from the output terminal 25 as a TS signal.
[0013]
By doing in this way, it is possible to select only a carrier signal having good reception characteristics in each branch, and the reception characteristics can be improved. However, in the conventional diversity system as described above, it is necessary to perform OFDM demodulation on signals received by a plurality of antennas in each branch and synthesize optimal data for each subcarrier. That is, the number of OFDM demodulating units is required as many as the number of antennas (branches), the circuit becomes large, and it is difficult to reduce the size of the receiver. Furthermore, with the increase in the number of branches, there is a problem that the receiving system becomes large and the power consumption of the receiver increases.
[0014]
Therefore, the technical problem to be solved by the present invention is to eliminate the above-mentioned problems of the prior art, and the object is to process signals received by a plurality of antennas with one OFDM demodulator. By doing so, the hardware scale is not increased, and the reception performance is excellent.
[0015]
[Means for Solving the Problems]
  In order to achieve the above-described object, the present invention provides a digital broadcast receiving apparatus having k receiving antennas (k is a positive integer of 2 or more) for receiving transmission waves transmitted by an orthogonal frequency division multiplexing system.
  A phase shifter that is provided in association with at least one of the k reception antennas and changes the phase of a signal received by the corresponding reception antenna; and an output signal from the phase shifter and the phase shifter that does not pass through the phase shifter A synthesizer that synthesizes a received signal from a receiving antenna, a tuning unit that tunes a necessary frequency from an output signal of the synthesizer, an analog-digital conversion circuit that converts the selected signal into a digital signal, and A demodulator that demodulates the output of the analog-digital conversion circuit;A reception state determining means provided in the demodulator;A control unit that controls the change of the phase shifter according to a signal from the demodulation unit,
  Or
  Each of the k reception antennas is provided in one-to-one correspondence, and k phase shifters that change the phase of the signal received by each reception antenna, and an output signal from each phase shifter are combined. A synthesizer, a tuning unit that tunes a necessary frequency from an output signal of the synthesizer, an analog-digital conversion circuit that converts the selected signal into a digital signal, and an output of the analog-digital conversion circuit are demodulated A demodulator;A reception state determining means provided in the demodulator;And a control unit that controls the change of the phase shifter according to a signal from the demodulation unit.
[0016]
  In addition, the control unitA generating unit that generates the phase amount to be output to the phase shifter sequentially, and the demodulating unit when the phase characteristics of the phase shifter are sequentially changed by the sequentially variable phase amount from the generation unit A determination unit that determines a phase amount that provides the best reception state as a phase amount to be set in the phase shifter based on an output of a reception state signal indicating a reception state of the reception signal from the signal, and a sequentially variable phase from the generation unit And a switching unit that switches and outputs the phase amount based on the determination from the determination unit to the phase shifter, the switching unit receiving signal degradation from the reception state determination unit of the demodulation unit When the signal is controlled to be switched so that the phase amount from the generation unit is output to the phase shifter, and the determination processing by the determination unit is completed, the determination is performed based on the determination from the determination unit. It is switching control so as to output the phase of the phase shifter,
  Or
  The control unit is configured to sequentially generate a phase amount to be output to the phase shifter, and a phase characteristic of the phase shifter is sequentially changed by the sequentially variable phase amount from the generation unit. A determination unit for determining a phase amount that provides the best reception state as a phase amount to be set in the phase shifter based on an output of a reception state signal indicating a reception state of the reception signal from the demodulation unit, and The switching unit that switches the phase amount that is sequentially changed and the phase amount based on the determination from the determination unit and outputs the phase amount to the phase shifter, and the switching unit from the reception state determination unit of the demodulation unit When the reception signal deterioration signal arrives, the switching is controlled so that the phase amount from the generation unit is output to the phase shifter, and when the determination process by the determination unit ends, the determination from the determination unit is completed. The phase amount based on the phase shifter is controlled to be output to the phase shifter, and the determination process described above and the phase amount set to the phase shifter based on the determination process are sequentially performed for each phase shifter. Is done.
[0017]
  In addition, the demodulation unit includes a C / N calculation unit that calculates a C / N value that is a ratio of a signal of received signals to noise, and the control unit includes:When the phase characteristics of the phase shifter are sequentially varied by the sequentially variable phase amount from the generation unit, the C / N value that is an output from the C / N calculation unit is sequentially stored; A storage unit that stores a phase amount corresponding to each C / N value at the time, and the determination unit of the control unit has a phase that maximizes the C / N value based on the information stored in the storage unit The amount is determined as the phase amount to be set in the phase shifter.
[0018]
  Further, the demodulation unit includes an error rate calculation unit that calculates a BER value that is an error rate of a received signal, and the control unit includes:When the phase characteristic of the phase shifter is sequentially varied by the sequentially varied phase amount from the generation unit, the BER value that is the output from the error rate calculation unit is sequentially stored, A storage unit that stores a phase amount corresponding to the BER value, and the determination unit of the control unit sets a phase amount that minimizes the BER value in the phase shifter based on the information stored in the storage unit; The phase amount is determined.
[0019]
  The demodulator includes an automatic gain calculator that calculates an AGC value that is a signal strength of a received signal, and the controller includes:When the phase characteristic of the phase shifter is sequentially varied by the sequentially varied phase amount from the generation unit, the AGC value that is the output from the automatic gain calculation unit is sequentially stored, A storage unit that stores a phase amount corresponding to the AGC value, and the determination unit of the control unit sets the phase amount that maximizes the AGC value in the phase shifter based on the information stored in the storage unit The phase amount is determined.
[0020]
  The demodulator includes a C / N calculator that calculates a C / N value that is a ratio of a signal and noise of a received signal, an error rate calculator that calculates a BER value that is an error rate of the received signal, An automatic gain calculation unit that calculates an AGC value that is a signal strength of the signal, and the control unit includes:When the phase characteristic of the phase shifter is sequentially varied by the sequentially varied phase amount from the generation unit, the C / N value that is the output from the C / N calculation unit, from the error rate calculation unit At least two of the output BER value and the AGC value output from the automatic gain calculation unit are sequentially stored, and each C / N value, each BER value, and each AGC value at that time are stored. A storage unit that stores a corresponding phase amount, and the determination unit of the control unit has a minimum C / N value and a minimum BER value based on the information stored in the storage unit The average value of the phase amount, or the average value of the phase amount that maximizes the C / N value and the phase amount that maximizes the AGC value, or the phase amount that minimizes the BER value and the AGC value becomes maximum. The average value with the phase amount or the position where the C / N value is the maximum The average value of the amount of phase the phase amount AGC value amount and BER value is minimized is maximum is determined as the phase amount to be set in the phase shifter.
[0021]
  Also,The reception state determining means of the demodulator constantly monitors the reception state, and outputs the reception signal degradation signal to the control unit when the reception state deteriorates.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to an embodiment of the present invention. The present embodiment is an example applied to a 2-branch diversity reception system.
[0024]
In FIG. 1, 11a and 11b are receiving antennas, 12 is a phase shifter (variable phase shifter), 13 is a combiner, 14 is a tuning unit (tuner), 15 is an analog-digital conversion circuit (hereinafter referred to as ADC), 16 Is an OFDM demodulator / decoder, 17 is a controller, 18 is an output terminal, 19 is a reception state signal, and 20 is a reception state deterioration signal.
[0025]
A signal received by the receiving antenna 11a is input to the phase shifter 12 as an RF signal. The input signal is output after the phase of the signal is rotated by the phase shifter 12. The phase rotation is controlled by inputting a control signal from an external input terminal. The output of the phase shifter 12 is connected to one input terminal of the combiner 13, and the reception antenna 11 b is connected to the other input terminal of the combiner 13. Synthesized. The synthesized signal is input to the channel selection unit 14 at the subsequent stage, and the input signal is selected and output by the channel selection unit 4. The selected signal is converted into a redigital signal by the ADC 15 and demodulated / decoded by the OFDM demodulator / decoder 16 in the subsequent stage. The demodulated / decoded signal is output from the output terminal 18 as a retransport signal.
[0026]
FIG. 3 is a block diagram of the OFDM demodulator / decoder 16. In the figure, 31 is an input terminal, 32 is an IQ demodulator, 33 is a guard interval removal circuit, 34 is an FFT processing circuit, 35 is a demodulation / equalization unit, 36 is a Viterbi decoding unit, 37 is an error correction circuit, and 38 is Synchronization processing circuit, 39 is a C / N calculation unit, 40 is a BER calculation unit, 41 is an AGC calculation unit, 42 is a reception state determination unit, 43 is an output terminal of the reception state degradation signal 20, and 44 is an output of the reception state signal 19 Terminal.
[0027]
The OFDM demodulator / decoder 16 performs OFDM demodulation processing and decoding processing on the received signal. First, the signal input from the input terminal 31 is IQ demodulated by the IQ demodulator 32, and the guard interval removal circuit 33 removes the guard interval from the IQ demodulated signal. The effective symbol from which the guard interval has been removed is subjected to FFT (Fast Fourier Transform) processing in the FFT processing circuit 34. The FFT processing is predetermined according to the transmission mode on the transmission side, and 2K, 4K, and 8K point discrete Fourier transform processing is performed. The signal subjected to the FFT processing is demodulated and equalized by the demodulation / equalization unit 35 and output to the Viterbi decoding unit 36 at the subsequent stage. The demodulated signal is subjected to the encoding and interleaving decoding performed on the transmission side in the Viterbi decoding unit 36. The output of the Viterbi decoding unit 36 is input to the error correction circuit 37 at the subsequent stage. The error correction circuit 37 performs reverse processing of processing performed on the transmission side, and performs error correction (Reed-Solomon decoding processing), despreading, and the like. The processed signal is output from the output terminal 18 as a transport signal. The deinterleave process includes a frequency deinterleave process, a time deinterleave process, a bit deinterleave process, a byte deinterleave process, and the like. Viterbi decoding also includes depuncture processing and the like.
[0028]
The C / N (ratio of received signal to noise) value of the received signal is calculated by the C / N calculator 39. The C / N calculation unit 39 calculates the variance of each signal point from the received signal constellation, and obtains the ratio to the signal level to output it as a C / N value.
[0029]
The BER (received signal error rate) value of the received signal is calculated by the BER calculator 40. The BER calculation unit 40 calculates an error rate before Viterbi decoding and after Viterbi decoding. It is also possible to calculate the error rate after Reed-Solomon. The BER calculation unit 40 outputs these calculated values as BER values.
[0030]
The AGC calculation unit 41 calculates an AGC value of the received signal (a value representing the signal strength of the received signal). The AGC value can be obtained from the square sum of the I signal and Q signal of the input signal or the square root thereof. Further, if it is a method of obtaining corresponding to this, not only this method but also an AGC value may be used. The AGC calculation unit 41 outputs these calculated values as AGC values.
[0031]
FIG. 4 is a block diagram of the control unit 17 that controls the phase shifter 12. In the figure, 50 is an input terminal, 51 is an output terminal, 52 is a storage unit, 53 is a determination unit, 54 is a generation unit, 55 is a switching unit, 56 is a switching control unit, and 59 is a reception state deterioration signal input terminal. .
[0032]
A C / N value (or BER value or AGC value) indicating the reception state of the received signal is input from the input terminal 50, and this value is stored in the storage unit 52. At the same time, it is also passed to the determination unit 53 in the subsequent stage. The determination unit 53 detects the maximum value of the input C / N value, and inputs the phase amount taking the value to the switching unit 55. The switching unit 55 switches the phase amount output from the generation unit 54 and the phase amount output from the determination unit 53 in accordance with an instruction from the switching control unit 56. The switched signal is output from the output terminal 51.
[0033]
FIG. 5 is a diagram showing the structure of the element of the typical phase shifter 12 in FIG. In the figure, 60 is an input terminal, 61 is a variable phase shifter, 62 is a strip line, and 63 is an output terminal.
[0034]
A signal input from the input terminal 60 is transmitted from a strip line 62 formed above the substrate 61 and output from an output terminal 63.
[0035]
The phase shifter 12 has a structure in which a dielectric 68 using BST (oxide of Ba, Sr, Ti) or liquid crystal is sandwiched between an upper electrode 66 and a lower electrode 67, and a control voltage is input from the control unit 17 as a voltage. By providing the terminals 65a and 65b, the dielectric constant of the dielectric element 68 is changed, and the rotation of the signal phase amount of the phase shifter 12 is controlled. The element is formed on the substrate 69.
[0036]
FIG. 6 is a diagram showing the reception sensitivity of the antenna unit in the present embodiment. The reception sensitivity of the antenna unit 71 (the reception antenna 11a and the phase shifter 12) is changed by setting the phase amount. Here, the arrival direction 72 shows the maximum sensitivity, and the arrival directions 73 and 74 show a decrease in reception sensitivity. Represents.
[0037]
FIG. 7 is a graph illustrating an example of the amount of phase rotation and reception characteristics. When the phase rotation amount is changed by the phase shifter 12 shown in FIG. 1, the C / N value also changes. Here, an example of operation when the maximum value is taken at point 80 and the minimum value is taken at point 81 is shown. When the phase rotation amount is changed by the phase shifter 12, the reception characteristics of the antenna unit 71 change as shown in FIG. 6, and the reception state changes according to the phase amount depending on the place where the receiving device is installed. . When the phase amount is changed, the C / N value of the received signal repeats strength depending on the reception state. When the C / N value output from the C / N calculator 39 in FIG. 3 fluctuates, this maximum point is detected, and the phase amount giving the maximum point is determined and output.
[0038]
The storage unit 52 of the control unit 17 shown in FIG. 4 stores the C / N value, and the determination unit 53 determines the maximum point of the C / N value. When the maximum point is detected, a signal indicating this is output from the determination unit 53 to the switching control unit 56, and in response to this, the switching control unit 56 sends a switching signal to the switching unit 55, and the output from the switching unit 55 is The phase amount generated by the generation unit 54 is switched to the phase amount giving the maximum point output from the determination unit 53, and this is sent to the phase shifter 12. As a result, an antenna unit capable of obtaining the maximum reception characteristic is formed, and the state with the best reception state is set.
[0039]
Similar processing can be performed by using a BER value in addition to the C / N value as a signal for outputting the reception state. As described above, when the phase rotation amount is changed by the phase shifter 12, the reception characteristics of the antenna unit 71 change, and the reception state changes according to the phase amount depending on the place where the receiving device is installed. become. When the phase amount is changed in this way, the BER value of the received signal repeats strength depending on the reception state, and the BER value output from the BER calculation unit 40 in FIG. 3 to the control unit 17 varies. . The control unit 17 detects the minimum point with the fewest errors from the BER value output from the BER calculation unit 40, determines the phase amount that gives the minimum point, and outputs it. That is, the storage unit 52 of the control unit 17 shown in FIG. 4 stores the re-BER value, and the determination unit 53 determines the minimum point of the BER value. When the minimum point is detected, a signal indicating this is output from the determination unit 53 to the switching control unit 56, and in response to this, the switching control unit 56 sends a switching signal to the switching unit 55, and the output from the switching unit 55 is The phase amount generated by the generation unit 54 is switched to the phase amount giving the minimum point output from the determination unit 53, and this is sent to the phase shifter 12. As a result, an antenna unit capable of obtaining the maximum reception characteristic is formed, and the state with the best reception state is set.
[0040]
Similarly, similar processing can be performed by using an AGC value in addition to the C / N value and the BER value as a signal for outputting the reception state. As described above, when the phase rotation amount is changed by the phase shifter 12, the reception characteristics of the antenna unit 71 change, and the reception state changes according to the phase amount depending on the place where the receiving device is installed. become. When the phase amount is changed in this way, the AGC value of the received signal repeats the strength depending on the reception state, and the AGC value output from the AGC calculation unit 41 in FIG. 3 to the control unit 17 varies. . The control unit 17 detects the maximum point with the largest received signal from the AGC value output from the AGC calculation unit 41, determines the phase amount that gives the maximum point, and outputs it. That is, the storage unit 52 of the control unit 17 shown in FIG. 4 stores the re-AGC value, and the determination unit 53 determines the maximum point of the AGC value. When the maximum point is detected, a signal indicating this is output from the determination unit 53 to the switching control unit 56, and in response to this, the switching control unit 56 sends a switching signal to the switching unit 55, and the output from the switching unit 55 is The phase amount generated by the generation unit 54 is switched to the phase amount giving the maximum point output from the determination unit 53, and this is sent to the phase shifter 12. As a result, an antenna unit capable of obtaining the maximum reception characteristic is formed, and the state with the best reception state is set.
[0041]
It is also possible to use the C / N value, the BER value, and the AGC value described above to determine the reception state. In this case, the C / N value, the BER value, and the AGC value can be used. An average value of the phase amounts obtained from the respective values is taken, or a phase amount obtained from any one of the C / N value, the BER value, and the AGC value is preferentially selected according to the viewer's selection. Is done.
[0042]
Here, in the present embodiment, the reception state determination unit 42 in the OFDM demodulator 16 always monitors the state of the received signal. When the reception state deteriorates, the reception state determination unit 42 returns to the control unit 17. Received signal degradation signal 20 is output. The received signal degradation signal 20 is input to the switching control unit 56 from the control input terminal 59 of the control unit 17 shown in FIG. 4, whereby the switching control unit 56 performs the determination of the reception state again. Is switched to the phase amount from the generation unit 54, and a predetermined signal is output to the generation unit 54, and the phase amount generated by the generation unit 55 is sequentially varied to execute the above-described determination operation. Thus, the point with the best reception state is determined, and the phase amount is set in the phase shifter 12. By such an operation, a state with the best characteristics of the receiving apparatus is automatically set, and a good receiving state can be achieved.
[0043]
Although the present invention has been described with reference to the illustrated embodiment, it goes without saying that various modifications can be made without departing from the spirit of the present invention. For example, FIG. 5 shows a structure of a typical phase shifter of the present invention. The phase shifter is not limited to this structure, and any other device or device having the same function and characteristics can be used. It can be used.
[0044]
In the above description, an example in which the phase shifter 12 is attached to only one of the two reception antennas has been shown. However, a phase shifter is individually attached to each of the two reception antennas, and each reception antenna (each You may make it set individually the phase amount with the best receiving state for every antenna unit. In this case, a switching circuit is provided between the control unit 17 and each phase shifter, and the above-described determination operation and phase amount setting may be sequentially performed for each antenna unit (note that the phase amount setting is not performed). Therefore, one antenna unit must be additionally provided with variable control voltage output means (phase amount output means). With such a configuration, the reception performance is further improved.
[0045]
In the above explanation, the case where the number of antennas in the antenna unit is two is taken as an example. However, it is possible to adopt a configuration in which the number of antennas is three or more, and the effect increases as the number of antennas increases. Become. In this case, a phase shifter may be selectively attached to only some of the reception antennas, or a phase shifter may be individually attached to all the reception antennas.
[0046]
【The invention's effect】
As described above, the present invention is characterized in that a signal received by a plurality of antennas is processed by one OFDM demodulator, and a receiving apparatus with high receiving performance is constructed without increasing the hardware scale. Can do. This also makes it possible to easily realize a portable receiving device, a mobile receiving device, etc. with high receiving performance without hindering downsizing. Furthermore, even in fixed reception, the influence of multipath can be reduced, and reception performance can be improved.
[0047]
In other words, unlike conventional antenna diversity, the hardware is not complicated, and it is possible to overcome the effects of multipath that occurs during mobile reception and mobile reception, and high-speed digital broadcasting and broadband communication that are expected in the future. Mobile reception can be realized very efficiently, and thus a small reception system with low power consumption can be realized. In particular, by using two or more antennas in a digital broadcast receiving apparatus incorporating a small antenna, the reception state can be improved while reducing the influence of multipath.
[0048]
In domestic terrestrial digital broadcasting, transmission power can be reduced to about one-tenth of the conventional transmission, and the same service area can be covered. However, even in a reception area that can be received conventionally, the reception may suddenly be impossible due to the cliff effect due to the influence of the multipath. According to the present invention, this problem can also be solved, the influence of multipath can be reduced, and reception can be achieved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a digital broadcast receiving apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a conventional diversity receiving device.
3 is a block diagram showing a configuration of an OFDM demodulator / decoder in FIG. 1. FIG.
4 is a block diagram showing a configuration of a control unit in FIG. 1. FIG.
FIG. 5 is an explanatory diagram showing a configuration of a typical variable phase shifter in an embodiment of the present invention.
FIG. 6 is an explanatory diagram showing reception characteristics of an antenna unit.
FIG. 7 is an explanatory diagram showing reception sensitivity characteristics of an antenna unit.
[Explanation of symbols]
11a, 11b Receiving antenna
12 Phaser (variable phaser)
13 Synthesizer
14, 14a, 14b Tuning section
15, 15a, 15b Analog-digital conversion circuit (ADC)
16 OFDM demodulator / decoder
17 Control unit
18 Output terminal
19 Reception status signal
20 Reception state deterioration signal
21a, 21b OFDM demodulator
22a, 22b decoding unit
23 Error rate calculator
24 selection circuit
25 Output terminal
31 Input terminal
32 IQ demodulator
33 Guard interval removal circuit
34 FFT processing circuit
35 Demodulator / Equalizer
36 Viterbi decoding unit
37 Error correction circuit
38 Synchronization processing circuit
39 C / N calculator
40 BER calculator
41 AGC calculator
42 Reception state determination unit
43 Output terminal for reception status deterioration signal
44 Output terminal for reception status signal
50 input terminals
51 Output terminal
52 Memory unit
53 Judgment part
54 Generator
55 switching part
56 Switching control unit
59 Reception state deterioration signal input terminal
60 input terminals
61 Variable phase shifter
62 Stripline
63 Output terminal
65a, 65b Voltage input terminal
66 Upper electrode
67 Lower electrode
68 Dielectric
69 substrates
71 Antenna unit
Maximum reception point of 80 C / N value or AGC value
Minimum reception point of 81 C / N value or AGC value
82 Minimum reception point of BER value
83 Maximum receiving point of BER value

Claims (7)

In a digital broadcast receiving apparatus having k receiving antennas (k is a positive integer of 2 or more) for receiving transmission waves transmitted by an orthogonal frequency division multiplexing system,
A phase shifter provided in association with at least one of the k reception antennas, and changing a phase of a signal received by the corresponding reception antenna;
A combiner that combines an output signal from the phase shifter and a reception signal from the reception antenna not passing through the phase shifter;
A tuning unit that selects a necessary frequency from the output signal of the synthesizer;
An analog-digital conversion circuit for converting the selected signal into a digital signal;
A demodulator that demodulates the output of the analog-digital conversion circuit;
A reception state determination means provided in the demodulation unit;
A control unit that controls phase characteristics of the phase shifter according to a signal from the demodulation unit;
Equipped,
The controller is
A generation unit that sequentially varies the amount of phase to be output to the phase shifter; and
Based on the output of the reception state signal indicating the reception state of the reception signal from the demodulation unit when the phase characteristic of the phase shifter is sequentially varied by the sequentially variable phase amount from the generation unit, the phase A determination unit that determines a phase amount that provides the best reception state as a phase amount to be set in the device;
A switching unit that switches the phase amount sequentially changed from the generation unit and the phase amount based on the determination from the determination unit and outputs the phase amount to the phase shifter;
The switching unit is controlled to switch to output the phase amount from the generation unit to the phase shifter upon arrival of a reception signal degradation signal from the reception state determination unit of the demodulation unit, and the determination process by the determination unit is performed. Upon completion, the digital broadcast receiving apparatus is controlled so as to output a phase amount based on the determination from the determination unit to the phase shifter. In a digital broadcast receiving apparatus having k receiving antennas (k is a positive integer of 2 or more) for receiving transmission waves transmitted by an orthogonal frequency division multiplexing system,
K phase shifters which are respectively provided in a one-to-one correspondence with the k reception antennas and change the phase of a signal received by each reception antenna;
A synthesizer for synthesizing output signals from the phase shifters;
A tuning unit that selects a necessary frequency from the output signal of the synthesizer;
An analog-digital conversion circuit for converting the selected signal into a digital signal;
A demodulator that demodulates the output of the analog-digital conversion circuit;
A reception state determination means provided in the demodulation unit;
A control unit for individually controlling the phase characteristics of each of the phase shifters by a signal from the demodulation unit;
Equipped,
The controller is
A generation unit that sequentially varies the amount of phase to be output to the phase shifter; and
Based on the output of the reception state signal indicating the reception state of the reception signal from the demodulation unit when the phase characteristic of the phase shifter is sequentially varied by the sequentially variable phase amount from the generation unit, the phase A determination unit that determines a phase amount that provides the best reception state as a phase amount to be set in the device;
A switching unit that switches the phase amount sequentially changed from the generation unit and the phase amount based on the determination from the determination unit and outputs the phase amount to the phase shifter;
The switching unit is controlled to switch to output the phase amount from the generation unit to the phase shifter upon arrival of a reception signal degradation signal from the reception state determination unit of the demodulation unit, and the determination process by the determination unit is performed. When finished, the switching is controlled so as to output the phase amount based on the determination from the determination unit to the phase shifter,
The digital broadcast receiving apparatus, wherein the determination process and the phase amount set to the phase shifter based on the determination process are sequentially performed for each phase shifter. In Claim 1 or 2,
The demodulator includes a C / N calculator that calculates a C / N value that is a ratio of a signal of a received signal to noise.
The controller sequentially outputs a C / N value, which is an output from the C / N calculator, when the phase characteristics of the phase shifter are sequentially varied by the sequentially varied phase amounts from the generator. A storage unit that stores the phase amount corresponding to each C / N value at that time,
The determination unit of the control unit determines, based on the information stored in the storage unit, a phase amount having a maximum C / N value as a phase amount to be set in the phase shifter. apparatus. In Claim 1 or 2,
The demodulator includes an error rate calculator that calculates a BER value that is an error rate of a received signal,
The control unit sequentially stores a BER value that is an output from the error rate calculation unit when the phase characteristic of the phase shifter is sequentially varied by the sequentially varied phase amount from the generation unit. And a storage unit for storing a phase amount corresponding to each BER value at that time,
The determination unit of the control unit determines, based on information stored in the storage unit, a phase amount with a minimum BER value as a phase amount to be set in the phase shifter. In Claim 1 or 2,
The demodulator includes an automatic gain calculator that calculates an AGC value that is a signal strength of a received signal,
The control unit sequentially stores the AGC value that is the output from the automatic gain calculation unit when the phase characteristics of the phase shifter are sequentially varied by the sequentially variable phase amount from the generation unit. And a storage unit for storing the phase amount corresponding to each AGC value at that time,
The determination unit of the control unit determines, based on information stored in the storage unit, a phase amount with a maximum AGC value as a phase amount to be set in the phase shifter. In Claim 1 or 2,
The demodulator includes a C / N calculator that calculates a C / N value that is a ratio of a signal and noise of a received signal, an error rate calculator that calculates a BER value that is an error rate of the received signal, and a received signal An automatic gain calculator for calculating an AGC value that is a signal strength,
The control unit has a C / N value that is an output from the C / N calculation unit when the phase characteristics of the phase shifter are sequentially varied by the sequentially varied phase amount from the generation unit, At least two or more of the BER value output from the error rate calculation unit and the AGC value output from the automatic gain calculation unit are sequentially stored, and each C / N value and each BER value at that time are stored. A storage unit that stores a phase amount corresponding to each AGC value;
Based on the information stored in the storage unit, the determination unit of the control unit is an average value of the phase amount with the maximum C / N value and the phase amount with the minimum BER value, or the C / N value. The average value of the phase amount with the maximum AGC value and the phase amount with the maximum AGC value, or the average value of the phase amount with the minimum BER value and the phase amount with the maximum AGC value, or the C / N value A digital broadcast receiving apparatus characterized in that an average value of a phase amount with a maximum BER value and a phase amount with a maximum BER value AGC value is determined as a phase amount set in the phase shifter. In Claim 1 or 2,
The digital broadcast receiving apparatus according to claim 1, wherein the reception state determining means of the demodulator constantly monitors the reception state and outputs the reception signal degradation signal to the control unit when the reception state deteriorates.

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