JP2023132551A - Receiving device and channel determination method - Google Patents

Abstract

To prevent a receiving device for terrestrial digital broadcasting from input detection reacting and malfunctioning even if the receiving device receives a signal of an interfering channel separated by a predetermined number of channels from a receiving channel set as a processing target.SOLUTION: A receiving device performs a process of detecting signal power by, after frequency-shifting a signal input to an FPGA 15 by an amount obtained by subtracting a first adjustment shift amount related to a first interference channel from a frequency shift amount for main line processing, passing the signal through a LPF 34, which limits it to a band for main line processing, and a process of detecting signal power by, after frequency-shifting the input signal by an amount obtained by adding a second frequency shift amount related to a second interference channel to an adjustment shift amount for main line processing, passing the signal through a LPF 44 which limits it to the band for main line processing band. The receiving device determines that the signal is from a receiving channel if the signal power is detected in both of those processes, and determines that the signal is from an interfering channel if not.SELECTED DRAWING: Figure 5

Description

The present invention relates to a receiving device that receives terrestrial digital broadcasting signals.

In systems that provide terrestrial digital broadcasting, relay stations are installed to relay broadcast signals. For example, the relay station converts a broadcast signal received on reception channel A to transmission channel B, which is different from reception channel A, and retransmits it. An overview of signal processing in a receiving device included in such a relay station will be explained using FIG. 1. Here, explanations of components that adjust the signal level, such as amplifiers, automatic gain controls (AGC), and attenuators, will be omitted since the positions and number of components to be inserted differ depending on the components used in the receiving circuit. In the following description, the modulation signal is OFDM (Orthogonal Frequency Division Multiplexing) adopted in terrestrial digital broadcasting, and the band is approximately 5.57 MHz (6 MHz x 13/14 to be exact).

FIG. 1 shows a partial configuration example of a receiving device included in a conventional relay station. The receiving device shown in the figure inputs an input received signal (R) to a mixer 11 and mixes it with a local signal generated by a local signal generating circuit 12 to generate an IF (Intermediate Frequency) signal (Ire ). To explain using a specific numerical example in digital terrestrial broadcasting, when there are 13 reception channels, the center frequency of the 13 channels is (473+1/7) [MHz]. In this case, the frequency of the local signal generated by the local signal generation circuit 12 is (510.15+1/7) which is higher than the center frequency of the 13 channels by 37.15 [MHz] which is the frequency of the IF signal. MHz]. Therefore, the output of the mixer 11 is 37.15 [MHz] and 983.44 [MHz] by multiplying the received signal (473+1/7) [MHz] and the local signal (510.15+1/7) [MHz]. ] are output.

By passing the output signal of the mixer 11 through a SAW (Surface Acoustic Wave) filter 13, it is possible to extract an IF signal (irk') which is a modulation signal centered at a desired frequency of 37.15 [MHz]. . The SAW filter is designed to limit the band of the IF signal corresponding to the reception channel (channel 13 in this case). The IF signal (irk') that has passed through the SAW filter 13 is converted from an analog signal to a digital signal by an A/D converter 14, and then input to an FPGA (Field Programmable Gate Array) 15. Here, as the clock of the A/D converter 14, a clock reproduced from the received signal is used. Since the clock for performing FFT (Fast Fourier Transform) processing specified in terrestrial digital television is (512/63) [MHz], here the frequency is (512/63 x 16), which is 16 times the FFT clock. [MHz] (hereinafter referred to as "130 MHz clock") is reproduced from the received signal and used as the sampling clock of the A/D converter 14.

In the FPGA 15, the captured signal is input to the orthogonal demodulation circuit 20. FIG. 2 shows a configuration example of an orthogonal demodulation circuit 20 in a conventional receiving device. The signal input to the orthogonal demodulation circuit 20 is input to the IQ separation circuit 21 which separates it into an I (In-phase) signal and a Q (Quadrature-phase) signal, and is converted into an I signal and a Q signal. Ru. In FIG. 2, the I signal and Q signal are collectively expressed as a complex signal by a thick black arrow.

The output signal of the IQ separation circuit 21 is input to a DDS (Direct Digital Synthesizer) 22. The DDS 22 shifts the frequency of the input signal by -37.15 [MHz] and converts it into a baseband signal. The output signal of the DDS 22 is clock-converted to a 32 MHz clock, which is 1/4 of the 130 MHz clock, through an LPF (Low Pass Filter) 23 and a 4-sample decimation circuit 24, and is further converted to a 32 MHz clock, which is 1/4 of the 130 MHz clock, and then converted to a 32 MHz clock, which is 1/4 of the 130 MHz clock. 26, the clock is converted to an 8 MHz clock, which is 1/4 of the 32 MHz clock.

In this way, by converting the input signal into an 8 MHz clock signal, it is possible to convert the input signal into an FFT clock signal specified by digital terrestrial television. The FFT clock signal is output from the orthogonal demodulation circuit 20 and transmitted to a subsequent digital processing circuit such as an equalizer. Since the digital processing circuit is not the essence of the present invention, which will be described later, a description thereof will be omitted. In other words, the present invention can be combined with any digital processing circuit.

Conventional techniques in the technical field related to the present invention include the following. For example, Patent Document 1 discloses a technique for removing loop waves (circuit signals) that cause a transmission signal to interfere with a reception antenna in a relay device for digital terrestrial broadcasting.

Japanese Patent Application Publication No. 2012-039300

Here, when the receiving channel set to be processed by the receiving device is channel 13, the received signal (R) is a channel 13 channels away from the receiving channel (channel 13), that is, a signal of channel 26. Consider the case. Since the center frequency of the 26 channels is (551+1/7) [MHz], this signal is input to the mixer 11. On the other hand, since the receiving device is operated to receive signals of 13 channels, a local signal of (510.15+1/7) [MHz] is output from the local signal generation circuit 12, as described above. In this case, the mixer 11 multiplies the received signal (551 + 1/7) [MHz] and the local signal (510.15 + 1/7) [MHz] to generate the signals of 40.85 [MHz] and 1061.44 [MHz]. A modulated signal centered on each is output, and these modulated signals are input to the SAW filter 13.

The SAW filter 13 is normally selected to be designed to pass only the band that is desired to be received as much as possible. If a filter with almost ideal characteristics could be used, the characteristics of the SAW filter 13 would be such that only the IF signal band of 37.15 [MHz] ±3 [MHz] passes. When the output signal from the mixer 11 is passed through the SAW filter 13 having this characteristic, a spectrum as shown in FIG. 3 is obtained.

In FIG. 3, the horizontal axis represents frequency, and the vertical axis represents signal level. Furthermore, the broken line in FIG. 3 indicates the pass band of the SAW filter 13, which corresponds to the region through which the signal to be received is passed. On the other hand, the hatched area in the figure shows the spectrum of the signal output from the mixer 11. As can be seen from Figure 3, if the receiving device receives a received signal 13 channels away from the receiving channel, part of the received signal will be captured even though it is a channel that is not originally used. . For this reason, there is a problem in that the receiving device mistakenly judges that the received signal that it wants to receive has arrived, and the input detection of the receiving device reacts and malfunctions.

Although the above explanation concerns a signal 13 channels away from the receiving channel, a similar problem of malfunction occurs with a signal 12 channels away from the receiving channel. Specifically, suppose that when the reception channel of the receiving device is channel 13, a signal of channel 25, which is 12 channels away from that channel, is received. In this case, the center frequency (545+1/7) of the received 25 channels and the local frequency (510.15+1/7) [MHz] for receiving the 13th channel are input to the mixer 11. The mixer 11 multiplies these signals to output modulated signals centered at 34.85 [MHz] and 1055.44 [MHz], respectively. The relationship between this output signal and the spectrum of the SAW filter 13 is shown in FIG. In FIG. 4 as well, since the hatched signal (output signal of the mixer 11) overlaps the region indicated by the broken line (the passband of the SAW filter 13), the input detection of the receiving device reacts and malfunctions.

The present invention has been made in view of the above-mentioned conventional circumstances, and allows a digital terrestrial broadcasting receiving device to receive signals of interfering channels that are separated by a predetermined number of channels from a receiving channel set to be processed. The purpose is to prevent input detection from reacting and malfunctioning even when received.

In order to achieve the above object, a receiving device according to one aspect of the present invention is configured as follows. That is, as an example, in a receiving device that receives terrestrial digital broadcasting signals, the received signal is mixed with a local signal for the receiving channel, frequency converted, and then the signal is passed through a filter that limits the band to an intermediate frequency. includes a signal processing unit input as a processing target, and the signal processing unit includes a channel determination unit that determines whether the received signal is a signal of the reception channel or a signal of an interfering channel different from the reception channel. The signal of the interfering channel is a signal of a channel whose part of the band passes through the filter when mixed with the local signal and subjected to frequency conversion; An adjustment shift amount that is larger than the width of the band and smaller than the width of the passband of the filter is set in advance, and the adjustment shift amount is used to convert the signal input to the signal processing section into a frequency shift amount for main line processing. After shifting the frequency by the amount of addition or subtraction, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and if the signal power is detected in the processing, the signal of the receiving channel If not, it is determined that the signal is from the interfering channel.

As another example, in a receiving device that receives terrestrial digital broadcasting signals, frequency conversion is performed by mixing the received signal with a local signal for the receiving channel. The signal processing unit is provided with a signal processing unit into which a signal passed through a filter that later limits the band to an intermediate frequency band is input as a processing target, and the signal processing unit is configured to determine whether the received signal is a signal of the reception channel or not. includes a channel determining unit that determines whether the signal of the interfering channel is a signal of a different interfering channel, and when the signal of the interfering channel is mixed with the local signal and subjected to frequency conversion, a part of the band exceeds the low frequency side of the filter. The signal of the first interfering channel that passes through, or the signal of the second interfering channel that passes through the high frequency side of the filter, and the channel determination unit is configured to detect the first interfering channel that is related to the first interfering channel. a first adjustment shift amount that is larger than the width of the partial band related to the second interference channel and smaller than the width of the pass band of the filter; A small second adjustment shift amount is set in advance, and after frequency-shifting the signal input to the signal processing unit by an amount obtained by subtracting the first adjustment shift amount from the frequency shift amount for main line processing, A process of detecting the signal power by passing it through a filter that limits the band to the main line processing band, and a process of detecting the signal power by passing the signal input to the signal processing section by adding the second adjustment shift amount to the frequency shift amount for the main line processing. After the signal is shifted in frequency by 100%, the signal is passed through a filter that limits the band for main line processing to detect the signal power, and if the signal power is detected in both of these processes, it is determined that the signal is from the receiving channel. , otherwise, it is determined that the signal is the first interfering channel or the second interfering channel.

Further, a channel determination method according to another aspect of the present invention is configured as follows. That is, in a channel determination method performed by a receiving device that receives a digital terrestrial broadcasting signal, the receiving device mixes the received signal with a local signal for the receiving channel, performs frequency conversion, and then converts the received signal into an intermediate frequency band. The signal processing unit includes a signal processing unit into which a signal passed through a filter that limits the signal is input as a processing target, and the signal processing unit is configured to determine whether the received signal is a signal of the reception channel or an interfering channel different from the reception channel. the signal of the interfering channel is a signal of a channel whose part of the band passes through the filter when mixed with the local signal and subjected to frequency conversion; The channel determination section has an adjustment shift amount set in advance that is larger than the width of the partial band and smaller than the width of the passband of the filter, and converts the signal input to the signal processing section into a frequency for main line processing. After the frequency is shifted by the amount obtained by adding or subtracting the adjustment shift amount to the shift amount, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and the signal power is detected by this processing. If so, the signal is determined to be the signal of the receiving channel, and if not, the signal is determined to be the signal of the interfering channel.

As another example, in a channel determination method performed by a receiving device that receives a digital terrestrial broadcasting signal, the receiving device performs frequency conversion by mixing the received signal with a local signal for the receiving channel. The signal processing unit is provided with a signal processing unit into which a signal passed through a filter that later limits the band to an intermediate frequency band is input as a processing target, and the signal processing unit is configured to determine whether the received signal is a signal of the reception channel or not. includes a channel determining unit that determines whether the signal of the interfering channel is a signal of a different interfering channel, and when the signal of the interfering channel is mixed with the local signal and subjected to frequency conversion, a part of the band exceeds the low frequency side of the filter. The signal of the first interfering channel that passes through, or the signal of the second interfering channel that passes through the high frequency side of the filter, and the channel determination unit is configured to detect the first interfering channel that is related to the first interfering channel. a first adjustment shift amount that is larger than the width of the partial band related to the second interference channel and smaller than the width of the pass band of the filter; A small second adjustment shift amount is set in advance, and after frequency-shifting the signal input to the signal processing unit by an amount obtained by subtracting the first adjustment shift amount from the frequency shift amount for main line processing, A process of detecting the signal power by passing it through a filter that limits the band to the main line processing band, and a process of detecting the signal power by passing the signal input to the signal processing section by adding the second adjustment shift amount to the frequency shift amount for the main line processing. After the signal is shifted in frequency by 100%, the signal is passed through a filter that limits the band for main line processing to detect the signal power, and if the signal power is detected in both of these processes, it is determined that the signal is from the receiving channel. , otherwise, it is determined that the signal is the first interfering channel or the second interfering channel.

According to the present invention, even if a digital terrestrial broadcasting receiving device receives a signal of an interfering channel that is a predetermined number of channels away from the receiving channel set to be processed, the input detection will react and malfunction. This can be prevented.

FIG. 2 is a diagram illustrating a partial configuration example of a receiving device included in a conventional relay station. FIG. 2 is a diagram illustrating a configuration example of an orthogonal demodulation circuit in a conventional receiving device. FIG. 4 is a diagram showing a spectrum when signals separated by 13 channels are received. FIG. 4 is a diagram showing a spectrum when signals separated by 12 channels are received. FIG. 3 is a diagram illustrating a configuration example of an orthogonal demodulation circuit in a receiving device according to an embodiment of the present invention. (a) is the spectrum when the reception channel signal is received, (b) is the spectrum when shifted by -4.0 [MHz], and (c) is the spectrum when shifted by +3.0 [MHz]. FIG. (a) is the spectrum when receiving a signal 12 channels away from the receiving channel, (b) is the spectrum when shifted by -4.0 [MHz], (c) is the spectrum when shifted by +3.0 [MHz] FIG. (a) is the spectrum when receiving a signal 13 channels away from the receiving channel, (b) is the spectrum when shifted by -4.0 [MHz], (c) is the spectrum when shifted by +3.0 [MHz] FIG.

An embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows a configuration example of the orthogonal demodulation circuit 30 in the receiving device according to an embodiment of the present invention. The orthogonal demodulation circuit 30 of this example includes an IQ separation circuit 21, a DDS 22, an LPF 23, a 4-sample decimation circuit 24, an LPF 25, a 4-sample decimation circuit 26, a DDS 31, an LPF 32, and a 4-sample decimation circuit. The circuit 33, the LPF 34, the signal power calculation circuit 35, the DDS 41, the LPF 42, the 4-sample decimation circuit 43, the LPF 44, the signal power calculation circuit 45, the determination circuit 51, and the output ON/OFF circuit 52. has.

The IQ separation circuit 21 to the 4-sample decimation circuit 26 are circuit units constituting a main processing unit for processing a reception channel set as a processing target of the receiving device. Note that the IQ separation circuit 21 to 4-sample decimation circuit 26 have the same configuration as the conventional example shown in FIG. 2, except that the output of the 4-sample decimation circuit 24 is divided into three, so a detailed explanation will not be provided. will be omitted. The DDS 31 to signal power calculation circuit 35 are first detection circuit units for detecting the signal power of a first interfering channel 13 channels away from the reception channel. Further, the DDS 41 to signal power calculation circuit 45 are a second detection circuit section for detecting the signal power of a second interfering channel 12 channels away from the reception channel.

The operation of the orthogonal demodulation circuit 30 of this example will be described below.
The output of the 4-sample decimation circuit 24 is divided into three parts, and one of them (the main signal) is passed through the LPF 25 and the 4-sample decimation circuit 26 and used in the subsequent digital signal processing circuit, as in the conventional case. A signal is generated.

One of the remaining two divided into three is input to the DDS 31 to shift the frequency of the signal by -4.0 [MHz]. The output signal of the DDS 31 is input to the LPF 34 via an LPF 32 and a 4-sample decimation circuit 33, which have the same functions as the LPF 25 and 4-sample decimation circuit 26 on the main line side. As the LPF 34, a filter with frequency characteristics that can take in only the signal of the reception channel set to be processed by the receiving device, that is, a filter that limits the band to the main processing band is used. The output signal of the LPF 34 is input to a signal power calculation circuit 35, and its signal power is calculated. The calculation result by the signal power calculation circuit 35 is input to the determination circuit 51.

Further, the other one of the remaining two divided into three is input to the DDS 41 to shift the frequency of the signal by +3.0 [MHz]. The output signal of the DDS 41 is input to the LPF 44 via an LPF 42 and a 4-sample decimation circuit 43, which have the same functions as the LPF 25 and 4-sample decimation circuit 26 on the main line side. As the LPF 44, a filter similar to the LPF 34 is used. The output signal of the LPF 44 is input to a signal power calculation circuit 45, and its signal power is calculated. The calculation result by the signal power calculation circuit 45 is input to the determination circuit 51.

The determination circuit 51 determines the received signal of the receiving device based on the calculation results of the signal power calculation circuits 35 and 45. Specifically, whether the signal of the receiving channel set to be processed by the receiving device was received, the signal of the first interfering channel 13 channels away from the receiving channel, or the signal of the second interfering channel 12 channels away from the receiving channel. Determine whether

Here, the signal of the first interfering channel, which is 13 channels away from the receiving channel, has a spectrum as shown in FIG. In addition, since the frequency shift of -37.15 [MHz] is performed by DDS22, when inputting to DDS31 or DDS41, the center frequency 37.15 [MHz] related to the receiving channel is shifted to 0 [MHz]. It has been shifted to become In DDS31, the frequency is shifted by -4.0 [MHz], so although the hatched area is shifted by 4.0 [MHz] to the left, it still largely overlaps with the band for processing the received channel, so there are many received signals. It is captured. On the other hand, in the DDS 41, the frequency is shifted by +3.0 [MHz], so that the received signal is removed from the band of the receiving channel.

FIG. 8 shows the spectrum for the signal of the first interfering channel, which is 13 channels away from the receiving channel. In FIG. 8, (a) is the spectrum when the signal of the first interfering channel is received, and (b) is the spectrum when the signal of the first interfering channel is shifted by -4.0 [MHz], (c) is a spectrum when the signal of the first interfering channel is shifted by +3.0 [MHz]. As is clear from FIG. 8, when the signal of the first interfering channel which is 13 channels away from the receiving channel is received, the signal power is observed in the signal power calculation circuit 35, but the signal power is observed in the signal power calculation circuit 45. It will not be observed.

Similarly, the signal on the second interfering channel, which is 12 channels away from the receiving channel, has a spectrum as shown in FIG. Since the DDS 31 shifts the frequency by -4.0 [MHz], the received signal is removed from the band of the receiving channel and disappears. On the other hand, in DDS41, the frequency is shifted by +3.0 [MHz], so although the hatched area is shifted by 3.0 [MHz] to the right, it still largely overlaps with the band for processing the received channel, so the received signal A lot is taken in.

FIG. 7 shows the spectrum for a signal on a second interfering channel 12 channels away from the receiving channel. In FIG. 7, (a) is the spectrum when the signal of the second interfering channel is received, and (b) is the spectrum when the signal of the second interfering channel is shifted by -4.0 [MHz], (c) is a spectrum when the signal of the second interfering channel is shifted by +3.0 [MHz]. As is clear from FIG. 7, when the signal of the second interfering channel which is 12 channels away from the receiving channel is received, the signal power is observed in the signal power calculation circuit 45, but the signal power is observed in the signal power calculation circuit 35. It will not be observed.

On the other hand, in the case of a signal of a receiving channel set to be processed by the receiving device, a signal with a band of ±2.785 [MHz] centered around 0 [MHz] is input to the DDSs 31 and 41. In this case, even if the frequency shift is performed by −4.0 [MHz] or +3.0 [MHz], the band largely overlaps with the reception channel band, so a large amount of the reception signal is captured.

FIG. 6 shows the spectrum of the received channel signal. In FIG. 6, (a) is the spectrum when the reception channel signal is received, (b) is the spectrum when the reception channel signal is shifted by -4.0 [MHz], and (c) is the spectrum when the reception channel signal is shifted by -4.0 [MHz]. This is a spectrum when the reception channel signal is shifted by +3.0 [MHz]. As is clear from FIG. 6, when the signal of the reception channel is received, the signal power is observed by both the signal power calculation circuits 35 and 45.

The determination circuit 51 uses the above characteristics to determine the received signal of the receiving device. Specifically, if the signal power can be detected by both of the two signal power calculation circuits 35 and 45, the determination circuit 51 determines that the signal of the reception channel has been received. In this case, the determination circuit 51 outputs a high level signal to the output ON/OFF circuit 52. The output ON/OFF circuit 52 outputs the main signal input via the LPF 25 and the 4-sample decimation circuit 26 from the orthogonal demodulation circuit 30 when a high level signal is input.

On the other hand, if the signal power cannot be detected in either of the two signal power calculation circuits 35, 45, the determination circuit 51 detects the signal of the first interfering channel which is 13 channels away from the receiving channel or the signal of the first interfering channel which is 12 channels away from the receiving channel. It is determined that the signal of the 2nd interference channel has been received. In this case, the determination circuit 51 outputs a Low level signal to the output ON/OFF circuit 52. The output ON/OFF circuit 52 cuts off the output of the orthogonal demodulation circuit 30 (that is, does not output the main signal) when a low level signal is input.

Further, if the signal power cannot be detected by both of the two signal power calculation circuits 35 and 45, the determination circuit 51 determines that the signal of the receiving channel is not received, and that the signal of the first interfering channel or the second interfering channel is not received. It is determined that no signal is being received. Also in this case, the determination circuit 51 outputs a Low level signal to the output ON/OFF circuit 52. The output ON/OFF circuit 52 cuts off the output of the orthogonal demodulation circuit 30 (that is, does not output the main signal) when a low level signal is input.

Here, in the determination circuit 51 of this example, it is determined that the signal power is detected when the calculation result by the signal power calculation circuits 35 and 45 is larger than 0, but the present invention is not limited to this. For example, a threshold value greater than 0 may be set in advance in consideration of noise, etc., and it may be determined that the signal power has been detected when the calculation result by the signal power calculation circuits 35 and 45 is greater than the threshold value.

As described above, the receiving device of this example mixes the received signal with the local signal for the receiving channel, performs frequency conversion, and then passes the signal through the filter SAW filter 13 that limits the band to an intermediate frequency. It includes an FPGA 15 (an example of a signal processing unit according to the present invention) that is input as a processing target. The FPGA 15 includes an orthogonal demodulation circuit 30 (an example of a circuit including a channel determination section according to the present invention) that determines whether a received signal is a signal of a reception channel or a signal of an interfering channel different from the reception channel. Here, the interference channel signal is a first interference channel signal whose part of the band passes through the low frequency side of the SAW filter 13 when mixed with the local signal and frequency converted, or a part of the band is the signal of the second interference channel that passes through the high frequency side of the SAW filter 13. The orthogonal demodulation circuit 30 includes a first adjustment shift amount (4.0 [MHz]) that is larger than the width of a part of the band related to the first interference channel and smaller than the width of the passband of the SAW filter 13; A second adjustment shift amount (3.0 [MHz]) that is larger than the width of a part of the band related to the interference channel and smaller than the width of the passband of the SAW filter 13 is set in advance. The orthogonal demodulation circuit 30 shifts the frequency of the signal input to the FPGA 15 by an amount obtained by subtracting the first adjustment shift amount from the frequency shift amount for main line processing (-4.0 [MHz]), and then converts the signal input to the FPGA 15 into a signal for main line processing. The process of detecting the signal power by passing it through the LPF 34 which limits the band to After shifting the frequency by the same amount, the signal is passed through the LPF 44, which limits the band to the main line processing band, and the signal power is detected. If the signal power is detected in both of these processes, it is determined that the signal is from the receiving channel. , otherwise, it is determined that the signal is the first interfering channel or the second interfering channel.

With such a configuration, a signal other than the receiving channel set to be processed by the receiving device (in this example, the signal of the first interfering channel 13 channels away from the receiving channel or the signal of the second interfering channel 12 channels away from the receiving channel) It is possible to prevent the input detection from reacting and malfunctioning even if the input detection is received.

Note that the above explanation takes into account the case where the receiving device is installed in an environment where there is a possibility of receiving signals from two types of interference channels, but it is assumed that there is only a possibility of receiving signals from one type of interference channel. If the receiving device is installed in an environment where there is no wireless communication, part of the above configuration may be omitted. That is, if there is no possibility of receiving the signal of the first interfering channel 13 channels away from the receiving channel, the DDS 31 to signal power calculation circuit 35 constituting the first detection circuit section can be omitted. Furthermore, if there is no possibility of receiving a signal on a second interfering channel 12 channels away from the receiving channel, the DDS 41 to signal power calculation circuit 45 constituting the second detection circuit section can be omitted.

Further, the arrangement of the output ON/OFF circuit 52 is not limited to the position shown in FIG. 5. For example, it is possible to turn the output ON/OFF at another location by introducing the High/Low signal resulting from the determination of the determination circuit 51 into a subsequent digital processing circuit.

Furthermore, the arrangement of the DDSs 31 and 41 is not limited to the positions shown in FIG. For example, a DDS 22 that shifts the output of the IQ separation circuit 21 by -37.15 [MHz] for the main signal, and a DDS 31' that shifts the output of the IQ separation circuit 21 by -41.15 (=-37.15-4) [MHz]. It is also possible to divide the signal into three parts including the DDS 41' which shifts the frequency by -34.15 (=37.15+3) [MHz]. However, in this case, it is necessary to add an LPF and a 4-sample decimation circuit having the same functions as the LPF 23 and the 4-sample decimation circuit 24 after each of the DDSs 31' and 41'.

Further, the adjustment shift amount of -4.0 [MHz] of the DDS 31 is merely an example, and the shift amount may be further shifted by about -2 MHz. Similarly, the adjustment shift amount of +4.0 [MHz] of the DDS 41 is merely an example, and the shift amount may be further shifted by approximately +2 MHz. The adjustment shift amount of the DDSs 31 and 41 is larger than the width of the band that passes through the SAW filter 13 when the interfering channel is mixed with the local signal for the reception channel and frequency converted, and is within the passband of the SAW filter 13. The shift amount may be smaller than the width of .

Although the embodiments of the present invention have been described above, the above embodiments are merely illustrative and do not limit the technical scope of the present invention. The present invention can take various other embodiments, and various modifications such as omissions and substitutions can be made without departing from the gist of the present invention. These embodiments and their modifications are included within the scope and gist of the invention described in this specification, etc., and are also included within the scope of the invention described in the claims and its equivalents.

Furthermore, the present invention not only can be provided as devices such as those mentioned in the above description or a system configured with these devices, but also methods to be executed by these devices, and functions of these devices can be implemented by a processor. It is also possible to provide a program for realizing the program, a storage medium that stores such a program in a computer-readable manner, and the like.

INDUSTRIAL APPLICATION This invention can be utilized for the receiving apparatus which receives the signal of a terrestrial digital broadcast.

11: Mixer, 12: Local signal generation circuit, 13: SAW filter, 14: A/D converter, 15: FPGA, 20: Orthogonal demodulation circuit, 21: IQ separation circuit, 22: DDS, 23: LPF, 24: 4 samples - decimation circuit, 25: LPF, 26: 4 samples - decimation circuit, 30: Orthogonal demodulation circuit, 31: DDS, 32: LPF, 33: 4 samples - decimation circuit, 34: LPF, 35: Signal power calculation circuit , 41: DDS, 42: LPF, 43: 4 sample-decimation circuit, 44: LPF, 45: Signal power calculation circuit, 51: Judgment circuit, 52: Output ON/OFF circuit

Claims (4)

In a receiving device that receives terrestrial digital broadcasting signals,
A signal processing unit is provided in which a signal obtained by mixing the received signal with a local signal for a receiving channel, performing frequency conversion, and passing through a filter that limits the band to an intermediate frequency band is input as a processing target,
The signal processing unit includes a channel determination unit that determines whether the received signal is a signal of the reception channel or a signal of an interfering channel different from the reception channel,
The signal of the interfering channel is a signal of a channel whose part of the band passes through the filter when mixed with the local signal and subjected to frequency conversion,
The channel determination section has an adjustment shift amount set in advance that is larger than the width of the part of the band and smaller than the width of the passband of the filter, and converts the signal input to the signal processing section into a main line processing one. After the frequency is shifted by the amount obtained by adding or subtracting the adjustment shift amount to the frequency shift amount, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and in this processing, the signal power is A receiving device characterized in that if detected, the signal is determined to be the signal of the receiving channel, and if not, the signal is determined to be the signal of the interfering channel. In a receiving device that receives terrestrial digital broadcasting signals,
A signal processing unit is provided in which a signal obtained by mixing the received signal with a local signal for a receiving channel, performing frequency conversion, and passing through a filter that limits the band to an intermediate frequency band is input as a processing target,
The signal processing unit includes a channel determination unit that determines whether the received signal is a signal of the reception channel or a signal of an interfering channel different from the reception channel,
The signal of the interference channel is a first interference channel signal whose part of the band passes through the low frequency side of the filter when mixed with the local signal and subjected to frequency conversion, or a signal of the first interference channel whose part of the band passes through the low frequency side of the filter. a second interference channel signal passing through the high-frequency side of the filter;
The channel determining unit is configured to determine a first adjustment shift amount that is larger than the width of the part of the band related to the first interfering channel and smaller than the width of the passband of the filter, and a shift amount of the part related to the second interfering channel. A second adjustment shift amount that is larger than the width of the band and smaller than the width of the passband of the filter is set in advance, and the signal input to the signal processing section is adjusted to the frequency shift amount for main line processing. After the frequency is shifted by the amount by which the adjustment shift amount is subtracted, the signal power is detected by passing through a filter that limits the band to the main line processing band, and the signal input to the signal processing section is shifted to the main line processing band. After the frequency is shifted by the sum of the frequency shift amount and the second adjustment shift amount, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and both of these processings A receiving device characterized in that if power is detected, the signal is determined to be the signal of the receiving channel, and if not, the signal is determined to be the signal of the first interfering channel or the second interfering channel. In a channel determination method performed by a receiving device that receives terrestrial digital broadcasting signals,
The receiving device includes a signal processing unit into which a signal that has been mixed with a local signal for a receiving channel, subjected to frequency conversion, and then passed through a filter that limits the band to an intermediate frequency is input as a processing target. Prepare,
The signal processing unit includes a channel determination unit that determines whether the received signal is a signal of the reception channel or a signal of an interfering channel different from the reception channel,
The signal of the interfering channel is a signal of a channel whose part of the band passes through the filter when mixed with the local signal and subjected to frequency conversion,
The channel determination section has an adjustment shift amount set in advance that is larger than the width of the part of the band and smaller than the width of the passband of the filter, and converts the signal input to the signal processing section into a main line processing one. After the frequency is shifted by the amount obtained by adding or subtracting the adjustment shift amount to the frequency shift amount, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and in this processing, the signal power is A channel determination method characterized in that if detected, the signal is determined to be the signal of the receiving channel, and if not, determined to be the signal of the interfering channel. In a channel determination method performed by a receiving device that receives terrestrial digital broadcasting signals,
The receiving device includes a signal processing unit into which a signal that has been mixed with a local signal for a receiving channel, subjected to frequency conversion, and then passed through a filter that limits the band to an intermediate frequency is input as a processing target. Prepare,
The signal processing unit includes a channel determination unit that determines whether the received signal is a signal of the reception channel or a signal of an interfering channel different from the reception channel,
The signal of the interference channel is a first interference channel signal whose part of the band passes through the low frequency side of the filter when mixed with the local signal and subjected to frequency conversion, or a signal of the first interference channel whose part of the band passes through the low frequency side of the filter. a second interference channel signal passing through the high-frequency side of the filter;
The channel determining unit is configured to determine a first adjustment shift amount that is larger than the width of the part of the band related to the first interfering channel and smaller than the width of the passband of the filter, and a shift amount of the part related to the second interfering channel. A second adjustment shift amount that is larger than the width of the band and smaller than the width of the passband of the filter is set in advance, and the signal input to the signal processing section is adjusted to the frequency shift amount for main line processing. After the frequency is shifted by the amount by which the adjustment shift amount is subtracted, the signal power is detected by passing through a filter that limits the band to the main line processing band, and the signal input to the signal processing section is shifted to the main line processing band. After the frequency is shifted by the sum of the frequency shift amount and the second adjustment shift amount, processing is performed to detect the signal power by passing it through a filter that limits the band for main line processing, and both of these processings A channel determination method characterized in that if power is detected, the signal is determined to be the signal of the reception channel, and if not, the signal is determined to be the signal of the first interfering channel or the second interfering channel.

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