Patent Application
20060182190
1. Field of the Invention
The present invention relates to a distribution line carrier transmitting device which supports, for example, frequency division communication and in which a frequency band used for communication is variable.
2. Description of the Related Art
First, a structure of the transmission processing system will be described. Reference numeral 4 denotes a framing circuit to translate digital transmission data from the input/output device into transmission format; and 5, a primary modulator which performs a processing to superimpose the formatted transmission data on a carrier wave. Reference numeral 6 denotes a frequency selector to select the carrier wave; and 7, an inverse fast Fourier transform circuit (IFFT circuit) which carries out inverse Fourier transform of the inputted data and generates transmission data combined with carrier wave number. Reference numeral 8 denotes a parallel/serial conversion circuit (P/S conversion circuit) to rearrange the transmission data in serial; and 9, a digital/analog conversion circuit (D/A conversion circuit) which converts the digital transmission data into analog data. The transmission data converted into the analog data is sent to the distribution line 1 through the coupling circuit 3.
Next, a structure of the reception system will be described. Reference numeral 11 denotes an analog/digital conversion circuit (A/D conversion circuit) to perform digital conversion of analog received data inputted through the coupling circuit 3; and 12, a serial/parallel conversion circuit (S/P conversion circuit) which converts the inputted distribution line carrier signal into parallel data. Reference numeral 13 denotes a fast Fourier transform circuit (FFT circuit) which carries out Fourier transform of the inputted digital data and decomposes it into individual frequency components. Reference numeral 14 denotes a frequency selector which selects an individual frequency of the decomposed received data and transmits the frequency value to the control circuit 2. Reference numeral 15 denotes a primary demodulator which demodulates the data modulated with the carrier frequency selected by the frequency selector 14. Reference numeral 16 denotes a deframing circuit which translates the demodulated data from the primary demodulation circuit 15 into reception format and outputs it as received data to the input/output device.
Next, a filter circuit to attenuate high-level noise will be described. Reference numeral 30 denotes a through circuit, the conduction/non-conduction of which can be controlled from the control circuit 2 and which has no filter function at the time of the conduction and allows all frequencies to pass through as they are. Reference numeral 31 denotes a high pass filter (HPF) to reduce a voltage of frequency of not higher than a lowest frequency f1 among plural distribution line carrier signal frequencies used for the distribution line carrier transmission; 32, a first band elimination filter (BEF) to attenuate a frequency component between the distribution line carrier signal frequency f1 of the lowest frequency and a next distribution line carrier signal frequency f2; 33, a secondband elimination filter (BEF) to attenuate a frequency voltage component between the distribution line carrier signal frequency f2 and a distribution line carrier signal frequency f3 of a next higher frequency; 34, a lowpass filter (LPF) to attenuate a frequency component not lower than a distribution line carrier signal frequency f3 of a highest frequency among the distribution line carrier signal frequencies; and 35, a selector to control the operations of the plural filters 31 to 34 and the through circuit 30 by the control from the control circuit 2. The respective filters 31 to 34 and the through circuit 30 are connected in parallel to each other between the coupling circuit 3 and the A/D conversion circuit 4.
When a signal is received, a conversion width of the A/D conversion circuit 11 is determined by a noise voltage. In the case where the highest signal level is not within the band of signals used for communication and the signal is an external noise, since the conversion width of the A/D conversion circuit 11 is determined by the noise voltage, in order to cut the noise voltage, a filter is provided in front of the A/D conversion circuit 11, and in the case where the maximum level signal is other than the frequency used for signal carrying, the frequency band is filtered, and the decoding processing is performed only when the maximum level signal is a frequency used for signal carrying.
When the highest signal level is the noise voltage, the conversion width of the A/D conversion circuit 11 is controlled by the noise, and the performance deteriorates, and therefore, it is necessary that the original signal has the highest signal level. In the conventional distribution line carrier transmitting device, as shown in
In order to deal with this, it is also possible to use a method in which a filter to attenuate a specific communication band is mounted to the outside of a device, and a filter is exchanged according to a band used for communication to deal with the case where the band used for the communication is variable. However, the installation place of this device is the vicinity of a transformer installed on an electric pole or the vicinity of a transformer buried in the ground, that is, the device is installed at a place where a filter can not be easily changed, and it is difficult to exchange the filter one by one for the installed equipment.
The invention has been made to solve the problems as described above, and has an object to provide a distribution line carrier transmitting device in which even if a frequency band used for communication is variable, a filter to be used is changed according to the frequency band, so that an influence of noise is eliminated, and stable communication is enabled.
According to an aspect of the invention, a distribution line carrier transmitting device, which supports, for example, frequency division communication and in which a frequency band used for communication is variable, includes plural filters to selectively attenuate a signal in a band not used for communication among received signals, and a selection unit to select a specified filter among the plural filters according to an instruction from an external I/F.
According to the distribution line carrier transmitting device of the invention, since the filter of the band used for the communication can be selected fromthe received signals by the instruction from the external I/F, connection to a center is performed by, for example, a distribution line or an optical fiber, and the frequency band of the filter can be changed remotely by using distribution line communication or Ethernet (registered trademark) communication, or the frequency band of the filter can be changed by remote control using a remote or the like from the vicinity of the device.
Hereinafter, embodiment 1 of the invention will be described with reference to
Reference numerals 1 to 16 denote the same parts as those in
Next, an operation will be described. The control circuit 2 receives instructions from the external I/F and determines the band used for communication. At that time, a filter to be used is changed so as to attenuate signals outside the communication band according to the band to be used for the communication. For example, consideration will be given to a case where as shown in
As stated above, according to this embodiment, in the distribution line carrier transmitting device in which the frequency band used for communication is variable, there are provided the plural filters to selectively attenuate a signal in a band not used for the communication among received signals, and the selection unit to select a specified filter among the plural filters, the filter is changed according to the band used for the communication to change the passband and the cut-off band, and accordingly, it is possible to easily deal with the communication in which the frequency is divided. Besides, since the band and the filter to be used for the communication can be changed by the instructions from the external I/F, connection to the center is performed by, for example, a distribution line, an optical fiber or the like, and the frequency band of the filter can be changed using the distribution line communication or Ethernet (registered trademark) communication, or the frequency band of the filter can be changed by remote control using a remote or the like from the vicinity of the device. Thus, since the communication band can be changed without physically exchanging a filter body, even after equipment is installed, the network structure can be flexibly changed.
Incidentally, in this embodiment, although the filter is inserted between the coupling circuit 3 and the A/D conversion circuit 11, even if it is inserted between the coupling circuit 3 and the distribution line 1, a similar effect can be obtained.
In embodiment 1, although the switching of the filter is realized using the distribution line communication, even in a method of using the same distribution line communication, as shown in
In this embodiment, in the case where a filter control signal is received, the signal is processed by the circuit dedicated for the filter control signal, that is, the band pass filter 51 and the demodulation circuit 52, not circuits 11 to 16 to process a normal distribution line communication signal. A signal in a band other than the filter control signal is attenuated by the band pass filter 51, and the signal is demodulated by the demodulation circuit 52. The result is notified to the control circuit 2, and the control of filters 41 to 43 is performed based thereon. By this, even in the case where the voltage level of a signal used for different communication is larger than the voltage level of a signal already used for communication and communication using a normal band can not be performed, the filter can be controlled by the distribution line communication.
In embodiment 1, although one of the low pass filter, the band pass filter, the high pass filter and the through circuit is selected according to the band used for the communication, there is a method in which as a filter, a high pass filter and a low pass filter are combined in a multi-stage configuration. Embodiment 3 using this method will be described with reference to
In this embodiment, a selector 45 is operated based on instructions from an external I/F 50, one kind is selected from the high pass filters 60 to 63, and one kind is selected from the low pass filters 65 to 68. By this, filters corresponding to sixteen kinds of bands can be realized from eight kinds of filters. That is, by this method, filters corresponding to frequency bands of kinds, whose number is not lower than the number of filters mounted on the circuit, can be realized.
In embodiments 1 to 3, although the filter to be used is changed according to the band used for communication, there is a method in which the characteristic of a filter is changed according to a band to be used for communication. Embodiment 4 using this method will be described with reference to
In this embodiment, a selector 45 is operated from an external I/F 50, and a value of the frequency variable filter 70 is changed to obtain a desired filter characteristic. Incidentally, in order to change constants of parts in the frequency variable filter 70, for example, when a variable resistor is used, a motor and a slidac are prepared, and the position of a contact of the resistor has only to be changed by using the motor to move the position of the slidac in accordance with the instruction of the selector. By this method, the communication of plural frequency bands can be dealt with without providing plural filters. In the above example, although the description has been given to the example in which the number of frequency variable filters is one, plural frequency variable filters are prepared, and the filter switching and filter characteristic change may be combined at the same time.
In embodiments 1 to 4, although the filter to be used is changed according to the band used for communication, there is a method in which a frequency band of a signal at the time when it passes through a filter is shifted according to the filter of the device. Embodiment 5 using this method will be described with reference to
In this embodiment, when the device receives a signal from a distribution line 1, the shift width of the frequency of the communication signal is instructed from a control circuit 2 to the signal frequency shift circuit 80 so that the frequency band of the signal is coincident with the passband of the band pass filter 81. In accordance with the instruction, the signal frequency shift circuit 80 performs the frequency shift of the communication signal. In this method, since the communication signal is changed according to the frequency of the filter, a communication signal in an arbitrary frequency band can be made to pass through without preparing plural filters, and a signal of a frequency other than that can be attenuated. Incidentally, in
Incidentally, in embodiments 1 and 3 to 5, even if the external I/F 50 is a manually operated I/F, such as a dip switch, a slide knob, or a volume knob, when the selector 45 is operated according to its movement and the filter is changed, the equivalent effect can be obtained. This is effective in the case where although it is unnecessary that the filter can be remotely operated, it is desired to determine, in the place where the device is installed, not the time of shipment, which filter is used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-040433 | Feb 2005 | JP | national |
| 2005-247954 | Aug 2005 | JP | national |
