KR100256699B1 - The spectrum division multiplexing and demultiplexing apparatus - Google Patents

Abstract

PURPOSE: A spectrum divisional multiplexing transmission apparatus is provided to increase the quantity of transmitting data by limiting a spectrum of base band signal to Nyquist spectrum. CONSTITUTION: The spectrum divisional multiplexing transmission apparatus includes a transmitting part and a receiving part. The transmitting part includes the first and second encoders(21,22), a low pass filter(23), a high pass filter(24) and a signal matching part(25). The first and second encoders(21,22) divide the first and second signals by the three-bits, respectively and add one bit to each three bits to cause the spectrum of each four bits to be Nyquist spectrum. The low pass filter(23) removes high frequency components from a signal from the first encoder(21) and the high pass filter(24) removes low frequency components from a signal from the second encoder(22). The signal matching part(25) combines the signals outputted from the low and high pass filters(23,24).

Description

Spectrum Division Multiplexer

The present invention encodes one baseband signal in a high frequency state to limit the signal spectrum to less than or equal to Nyquist frequency, 1 / 2T (where T is one period of the signal), and encode another input signal. The present invention relates to a spectrum division multiplexing apparatus for increasing the amount of information transmitted by multiplexing at 1 / 2T to 1 / T interval twice the coding rate.

Conventionally, in transmitting a baseband signal, the maximum capacity capable of transmitting a baseband signal in a transmission path by transmitting a non-zero return (NRZ) signal and a zero return (RZ) signal as it is is It is half of the transmission band or the same value.

1 is a power spectral characteristic diagram of a conventional baseband signal. When the baseband signal to be transmitted is an NRZ signal, the signal power components are distributed up to the maximum frequency of the signal frequency. It is distributed up to twice the maximum frequency contained in the signal. Thus, the band of the baseband signal consists of only one signal component to be transmitted.

Such a conventional transmission device has a high transmission cost due to a small transmission capacity in the same channel, and there is a problem that the transmission device and the line need to be replaced or additionally installed when the transmission band required for one transmission path increases.

In order to solve the above problems, the present invention encodes one baseband signal to limit the signal spectrum to below the Nyquist frequency, encodes another input signal, and multiplexes the remaining signal to transmit the transmission capacity. It is an object of the present invention to provide a spectrum division multiplexing device for increasing.

1 is a power spectral characteristic diagram of a conventional baseband signal.

2 is a configuration diagram of an embodiment of a transmitter of a spectrum division multiplexing apparatus according to the present invention.

3 is a configuration diagram of an embodiment of a receiver of a spectrum division multiplexing apparatus according to the present invention.

4 is a spectral characteristic diagram of a signal encoded according to the present invention.

5 is a spectral characteristic diagram of a spectral division multiplexed signal according to the present invention.

* Explanation of symbols for the main parts of the drawings

21,22 Encoder 23,31 Low pass filter

24,32: high pass filter 25: signal matcher

33,34: demodulator

In order to achieve the above object, the present invention provides a method for encoding a first baseband signal with a line code having a minimum bandwidth, thereby limiting a main signal spectrum having a signal spectrum below a Nyquist frequency and a second baseband signal. Signal transmitting means for transmitting a spectral division multiplex signal by multiplexing a spectral signal distributed over a Nyquist frequency of a signal encoded by a line code having a minimum bandwidth and restricting the signal spectrum below the Nyquist frequency by section; And signal receiving means for obtaining the first and second baseband signals by extracting the spectral divided multiple signals received from the signal transmitting means according to frequency components and demodulating the respective signals.

For better understanding of the present invention, a technique of limiting the spectrum below the Nyquist frequency by using encoding to output binary data in an actual system will be described in more detail.

The Nyquist frequency defines 1 / 2T as the Nyquist frequency when the symbol rate of the signal is 1 / T (T is a symbol period).

Coding methods for limiting the spectrum of one baseband signal below the Nyquist frequency include the "Duo-bianry coding method" using partial response and the minimum bandwidth line coding method using "block coding". .

"Duo-bainary" is output as a ternary signal rather than binary at the output level, which is not suitable for general binary digital transmission.

The minimum bandwidth line code using the block coding technique is encoded by restricting the system parameters of the line code, ASV (Alternate Sum Variation) and DSV (Digital Sum Variation). You can make it as it exists. In this case, the main lobe and the first side lobe have the same power and contain the same information. Therefore, the main lobe and the first side lobe may transmit the main lobe or only the first side lobe. .

Theoretically, in order to limit the spectrum of a binary digital signal to within the Nyquist frequency, the transmit data shaping filter must be shaped into a "sinc pulse" in the time domain, which is an infinite tail in the time domain. Tail) As a way of eliminating this infinite tail, the "Raised Cosine Pulse" is used, which limits the spectrum to exactly below the Nyquist frequency when the "Roll-off factor" is zero.

In practice, however, it is impossible to implement. In general, binary data of an implementation wave is applied to a transmission channel through a band-limited device (finally low pass filtering effect). In this case, the spectrum of the signal has a band spread up to 1 / T (ie twice the Nyquist frequency), and the signal adjacent to the spectral null point for Inter-Symbol Interference (ISI) free communication. This results in multiplexing of signals at 1 / T intervals.

For multiplexing, multiplexing is done so that more than the baseband bandwidth falls, and cannot be defined as the Nyquist frequency. Theoretically, when pulse shaping the input data with the Sinc function, the spectrum becomes less than the Nyquist frequency, so it can be said that it is multiplexed above or above. Scrambled NRZ). 4 times (RZ. Or manchester codiing).

Thus, in a practical implementation, the baseband signal is sent to the channel by pulse shaping using a simple low pass filter as described above, where the spectrum is null at twice the Nyquist frequency. do.

In the present invention, even when the same pulse shaping is used, a technique of encoding the spectrum of the signal such that null exists at the Nyquist frequency is used.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

According to the present invention, a spectrum division multiplex transmission apparatus encodes one binary digital baseband signal (first baseband signal) with a line code having a minimum bandwidth and outputs the signal spectrum as a binary digital signal while outputting the Nyquist frequency. Limit the signal spectrum below the Nyquist frequency while encoding the main signal spectrum limited below and other binary digital baseband signal (second baseband signal) with a line code having the minimum bandwidth and outputting it as a binary digital signal. A transmitter (see FIG. 2 below) which multiplexes a spectral signal distributed over the Nyquist frequency of one signal and transmits a spectral division multiplex signal, and extracts a spectral division multiplex signal received from the transmitter according to a frequency component. Demodulating the respective signals to obtain the first and second baseband signals (see FIG. 3 below). It is.

First, the transmitter of the spectrum division multiplexing apparatus will be described in more detail with reference to FIG. 2.

2 is a block diagram of an embodiment of a transmitter of a spectrum division multiplexing apparatus according to the present invention. In the drawing, "21" is a first encoder, "22" is a second encoder, "23" is a low pass filter, and "24". Is a high pass filter and "25" is a signal matcher, respectively.

The first and second encoders 21 and 22 divide the first and second signals into three bit units, add one extra bit, and convert the 4-bit code into zero bits of the encoded signal spectrum. ) Is encoded to exist at 1 / 2T, the Nyquist frequency.

The low pass filter 23 removes a high frequency component from the signal received from the first encoder 21 and passes a signal having a pass band from a direct current (frequency of 0) to a 1 / 2T frequency, and a high pass filter 24. Removes the low frequency component from the signal received from the second encoder 22 and passes only the high frequency signal of 1 / 2T or more.

The signal matcher 25 receives the encoded signal of the first signal composed of the low frequency spectrum received from the low pass filter 23 and the encoded signal of the second signal composed of the high frequency spectrum received from the high pass filter 24. Match signals so that they can be applied to one transmission path.

The operation of the transmitter of the spectrum division multiplexing apparatus will be described below.

First, a first signal, which is an input baseband signal, is divided in units of 3 bits, and 1 bit is added by the first encoder 21, so that the spectral component is zero at 1 / 2T, which is the Nyquist frequency. Encode with the lowest bandwidth possible.

As such, the result of encoding the minimum bandwidth by the first encoder 21 is shown in FIG. 4 (4a). As can be seen in FIG. 4, the spectrum of the encoded signal is symmetric with respect to 1 / 2T on the frequency axis, and the spectral component becomes zero at the 1 / 2T point.

Then, when the signal encoded by the encoder 21 is applied to the low pass filter 23, the low pass filter 23 removes the frequency component of 1 / 2T or more of the spectral components of the signal and 1 to zero (0). The signal passing only the band component up to / 2T is applied to the signal matcher 25.

On the other hand, the second signal is divided into units of 3 bits like the first signal, and the second encoder 22 adds 1 bit and encodes the signal with the minimum bandwidth such that the spectral component becomes zero at 1 / 2T.

Then, when the signal encoded by the encoder 22 is applied to the high pass filter 24, the high pass filter 24 removes frequency components of 1 / 2T or less of the spectral components of the signal, and at 1 / 2T Passes signals up to 1 / T and applies them to the signal matcher 25.

As such, the result of encoding the minimum bandwidth by the first and second encoders 21 and 22 is shown in FIG. As can be seen in FIG. 4, the spectra 4a and 4b of the encoded signal are symmetrically about 1 / 2T on the frequency axis, and the spectral component becomes zero at the 1 / 2T point.

Meanwhile, the encoded signal of the first signal composed of the low frequency spectrum received from the low pass filter 23 by the signal matcher 25 and the second signal composed of the high frequency spectrum received from the high pass filter 24 are encoded. The result of matching the signal is shown in FIG. As can be seen in FIG. 5, since the first signal exists in the 1 / 2T section at DC (frequency is 0) (5a), and the second signal exists in the 1 / T section at 1 / 2T (5b). It can be applied by applying to one transmission path.

Now, the receiver of the spectrum division multiplexing apparatus will be described in more detail with reference to FIG. 3.

3 is a block diagram of a receiver of a spectral division multiplexing apparatus according to the present invention, in which "31" is a low pass filter, "32" is a high pass filter, "33" is a first demodulator, and "34" is Each second demodulator is shown.

In the spectrum division multiplex signal received from the transmitter of the spectrum division multiplexing apparatus of FIG. 2, the first signal is present in a section where the frequency is DC (frequency is 0) to 1 / 2T, and the section is 1 / 2T to 1 / T. There is a second signal.

The low pass filter 31 extracts low frequency components by passing a band from DC to 1 / 2T in the received spectral division multiplexed signal, and the high pass filter 32 selects 1 / 2T to 1 in the received spectral division multiplexed signal. Pass the band up to / T to extract the high frequency components.

The first demodulator 33 demodulates the first signal from the signal output from the low pass filter 31, and the second demodulator 34 demodulates the second signal from the signal output from the high pass filter 32.

The operation of the receiver of the spectrum division multiplexing apparatus will be described below.

When the spectral division multiplexing signal is received at the receiver of the spectral division multiplexing device, the received spectral division multiplexing signal is applied to the low pass filter 31 and the high pass filter 32, where the low pass filter 31 is received. Only the frequency component corresponding to the 1 / 2T section is extracted from the DC signal (frequency is 0) and transmitted to the first demodulator 33, and the first demodulator 33 receives the original 3-bit data from the received 4-bit signal. Demodulate and extract the first signal.

Meanwhile, the high pass filter 32 extracts only a component corresponding to the 1 / T section at 1 / 2T from the received spectral division multiplexed signal and transmits the component to the first demodulator 34, and the second demodulator 34 receives the received signal. The second signal is extracted by demodulating the original 3-bit data from the 4-bit signal.

As described above, the present invention encodes the baseband signal at a high coding rate so that the frequency spectrum of the signal is limited to 1/2 of the maximum signal frequency in order to increase the transmission capacity of the transmission path and the system used in the conventional transmission system. The low pass filter removes the high frequency components and inserts the spectrum of other signals into the empty 1/2 channel band so that the signal capacity can be applied as much as twice the coding rate to the channel of the same transmission band as before. By increasing, the transmission rate can be reduced. That is, the transmission efficiency is increased by " (coder input data / coder output data) × 2 " compared with the conventional baseband transmission system.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

In the present invention as described above, the baseband signal is encoded at a high coding rate such that the frequency spectrum of the signal is limited to 1/2 of the maximum signal frequency, and after removing the high frequency component, the spectrum of another signal is inserted into the remaining empty band. The transmission cost can be reduced by increasing the signal capacity by increasing the signal capacity by twice the coding rate in the channel of the same transmission band as in the related art.

Claims (3)

The first baseband signal is encoded with a line code having a minimum bandwidth and the signal spectrum is limited to a Nyquist frequency or less, and the second baseband signal is encoded with a line code having a minimum bandwidth. Signal transmission means for multiplexing the spectral signal distributed over the Nyquist frequency of the signal whose spectrum is limited below the Nyquist frequency for each section to transmit the spectral division multiplexed signal; And signal reception means for demodulating respective signals by extracting the spectral division multiplex signals received from the signal transmission means according to frequency components, thereby obtaining the first and second baseband signals. 2. The apparatus of claim 1, wherein the signal transmitting means comprises: first encoding means for encoding with a minimum bandwidth so that zero of the encoded signal spectrum is present at the Nyquist frequency by adding an extra bit to the first baseband signal. ; Second encoding means for encoding with a minimum bandwidth so that an extra bit is added to the second baseband signal so that a zero point of an encoded signal spectrum exists at the Nyquist frequency; First filtering means for filtering such that a passband of the signal applied from the first encoding means exists from a direct current to a Nyquist frequency; Second filtering means for filtering such that a passband of the signal applied from the second encoding means exists above the Nyquist frequency; And signal matching means for combining a signal consisting of a low frequency spectrum received from the first filtering means and a signal consisting of a high frequency spectrum received from the second filtering means to be applied to one transmission path. Multiple transmission device. 3. The apparatus of claim 1 or 2, wherein the receiving means comprises: third filtering means for extracting low frequency components from the spectral divided multiplex signals transmitted from the signal transmitting means; Fourth filtering means for extracting high frequency components from the spectral divided multiplex signals transmitted from the signal transmitting means; First demodulation means for demodulating the first baseband signal in a signal output from the third filtering means; And second demodulation means for demodulating the second baseband signal in a signal output from the fourth filtering means.

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