JP2006222683A - Adapter for diversity reception used for wired communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform diversity reception at a receiving terminal for an information transmission signal used for wired communication by using a current and a voltage. <P>SOLUTION: An adapter 21 for diversity reception is equipped with a load terminal 22 for connecting an original load such as household electrical appliances and telephone sets, and a voltage detecting terminal 24 and a current detecting terminal 23. Voltage and current signals are taken out from those voltage detecting terminal 24 and current detecting terminal 23 and diversity reception processing is performed, so that improvement effect on reception quality can be expected by using complementary relationship between the current and voltage. Thus, the adapter for connecting the original loads such as the household electrical appliances and telephone sets is equipped with the voltage detecting terminal 24 and current detecting terminal 23, so that the loads can be connected and the information transmission signal can be input by the one adapter. A narrow adapter installation space can effectively be used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a diversity reception technique for realizing improvement in reception quality, which is used when communication is performed using a line such as a power line and a telephone line as a transmission line.

The diversity reception method is a method for improving reception quality by receiving a plurality of reception signals having the same content and combining them or selecting a higher quality signal.
Diversity reception methods are conventionally used in the field of wireless communication for signals received by different antennas, signals with different polarizations, signals with different radio wave arrival angles (diversity target signals are called diversity branches), etc. This has been done to improve the quality of the received signal.

The idea of diversity reception is also adopted in wired communication (see Patent Documents 1 and 2).
Patent Documents 1 and 2 propose a method for diversity reception of a communication signal at a receiving end via a plurality of power lines through which the same communication signal is transmitted.
JP 2004-64405 A Japanese Patent Laid-Open No. 11-205201

However, the diversity reception methods described in Patent Documents 1 and 2 use a plurality of lines.
For this reason, it is necessary to lay a plurality of lines between the transmission end and the reception end, and there is a problem that the cost for constructing the communication system increases.
Generally, in order to obtain the reception quality improvement effect by diversity, it is necessary that the correlation between the diversity branches is small. That is, it is necessary to have a complementary relationship in which one is in a bad state (eg, the amplitude is small) and the other is not bad (eg, the amplitude is large).

The inventor has noted that the relationship between the current flowing through the pair of lines and the voltage is complementary.
That is, when the impedance of the load connected to the line is large, the voltage of the load increases and the current decreases. When the load impedance is small, the load voltage decreases and the current increases.

Therefore, since the current and the voltage have a complementary relationship at the receiving end of the information transmission signal, if these are selected as the diversity branch, an effect of improving the reception quality can be expected.
Therefore, if the voltage detection terminal and the current detection terminal for diversity reception are attached to the power receiving end of the line such as the power line, the telephone line, etc., the adapter for connecting the original load such as a home appliance or a telephone, the whole fits in a compact, Convenient.

  The present invention provides a diversity receiving adapter that can connect an original load at the receiving end of an information transmission signal used for wired communication and can extract a complementary current and voltage. With the goal.

  The diversity reception adapter according to the present invention includes a voltage detection unit that detects an information transmission signal (referred to as a voltage signal) included in a voltage detected at a receiving end of a line, a voltage detection terminal thereof, and a detection at the receiving end of the line. A current detection unit for detecting an information transmission signal (referred to as a current signal) included in the current and its current detection terminal, and a load terminal for connecting a load to the line (claim 1).

  According to this diversity receiving adapter, it has not only a load terminal for connecting an original load such as a home appliance or a telephone, but also a voltage detection terminal and a current detection terminal. Diversity reception processing can be performed by taking out the voltage signal and the current signal from the terminal and the current detection terminal. This diversity reception can be expected to improve reception quality by utilizing a complementary relationship between current and voltage.

And since the adapter which connects original load, such as household appliances and a telephone, is provided with a voltage detection terminal and a current detection terminal, it can connect a load and take in an information transmission signal with one adapter. Therefore, a narrow adapter installation space can be effectively used compared to preparing a dedicated adapter having a voltage detection terminal and a current detection terminal.
Further, it is not necessary to install a current detection unit and a voltage detection unit in the reception device, and the reception device can be reduced in size. In particular, when the line is a power line, there is no need to draw a high-voltage power line into the receiving device, so that a small diameter wire can be used for the receiving device and the safety is improved.

When the line is a power line, the load terminal is an AC outlet (Claim 2). When the line is a telephone line, the load terminal is a telephone outlet (Claim 3).
When a power line is used as a line, the load impedance of an electric device connected as a load varies with time depending on the power on / off of the device. Even when the line is a telephone line, the load impedance fluctuates due to the on-hook and off-hook of the telephone connected as a load. It can be applied effectively.

The diversity reception may employ so-called combining diversity, in which the detected current signal and voltage signal are weighted and combined so as to obtain the best reception quality, and the voltage signal and current signal may be employed. Of these, so-called selection diversity, which selects the one having the better reception quality, may be employed.
In the combining process, the detected voltage signal and current signal may be subjected to Fourier transform, and the frequency domain signals subjected to Fourier transform may be combined with weights. In particular, when transmitting a broadband information transmission signal, the frequency characteristics of the load impedance are generally not uniform, and large and small fluctuations occur within the signal band. According to this method, in the frequency domain, the complementary current signal and voltage signal can be combined to improve the non-uniformity of the signal spectrum within the band.

In particular, if one of the voltage signal and the current signal is a real part and the other is an imaginary part and a complex time signal is created and Fourier transformed, the voltage signal and the current signal are individually Fourier transformed. In comparison, the number of Fourier transform circuits is halved, and there is an advantage that the circuit configuration of the Fourier transform circuit is simplified.
As a transmission method of the information transmission signal related to the Fourier transform, there are an OFDM method and a single carrier block transmission method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram illustrating a detection circuit for an information transmission signal at a power receiving end of a power line or a telephone line when communication is performed by superimposing the information transmission signal on a pair of power lines or a telephone line.
The power line may be a transmission / distribution line that supplies commercial power to a home or office, or an in-vehicle wiring that supplies DC power to the vehicle.

The information transmission signal may be either a baseband encoded signal such as an RZ code or a Manchester code, or a band signal obtained by performing digital modulation such as PSK, FSK, or QAM.
The information transmission signal is detected as a current signal by the current component detection circuit 1 and detected as a voltage signal by the voltage component detection circuit 2.

For example, a current signal can be easily detected as the voltage across a resistor inserted in series with the line, but if a resistor is inserted, a loss occurs, so a coil (current transformer) surrounding the line is generally inserted. . Here, as one type of current transformer, a current probe is used that detects the voltage generated in the winding by inserting a power line into the magnetic circuit of the transformer.
The voltage signal only needs to detect the voltage generated between the lines at the power receiving end, and the circuit configuration for the detection is arbitrary.

It should be noted that the current signal itself does not necessarily have to be expressed as a current change, and may be converted into a voltage by a resistor or the like. Hereinafter, in the embodiment of the present invention, description will be made assuming that both the current signal and the voltage signal are signals represented by voltage changes.
In the diversity reception method using the adapter according to the present invention, these current signals and voltage signals are handled as diversity branches, and these voltage signals and current signals are combined or selected, so that the reception quality is improved. To improve.

FIG. 2 is a block diagram showing the diversity receiving adapter 21 of the present invention.
The diversity receiving adapter 21 includes the current component detection circuit 1 and its current detection terminal 23, the voltage component detection circuit 2 and its voltage detection terminal 24, and a load terminal 22 for connecting a load to a power line or a telephone line. It consists of one housing | casing containing.
The material of the housing may be metal or synthetic resin. The housing may be a wall-mounted or wall-mounted fixed type, or a movable type (so-called table tap type) attached to the end of the track.

The current detection terminal 23 and the voltage detection terminal 24 supply a current signal and a voltage signal to a diversity receiver (described later), respectively, and their terminal types are arbitrary.
Here, the `` terminal '' includes, for example, a connector, a terminal, a terminal fitting, a screw-type terminal block for fastening a conductive wire with a screw, a so-called screwless terminal block for connecting only by inserting a conductive wire, a so-called lead terminal from which a lead wire is drawn out, etc. Various embodiments can be employed.

The load terminal 22 for connecting the load is an AC outlet when the line is a power line. Insert the plug of the power cord of the home appliance that is the original load into this outlet. In addition to the above, a load terminal having an arbitrary shape can be applied.
A terminal may be provided on the line side to which a power line or the like is connected. For example, if an AC plug terminal is provided on the line side, the adapter can be directly plugged into an AC outlet.

When the line is a telephone line, the load terminal 22 for connecting the load is a telephone outlet. Insert a modular plug such as a telephone or computer into this telephone outlet.
Since the frequency band of the detected voltage signal and current signal is higher than the power line power frequency of the power line and the telephone signal frequency of the telephone line, in order to remove the low frequency power supply voltage / current and telephone signal. It is desirable to pass through the high-pass filter F.

Therefore, a high-pass filter F is inserted in each of the current component detection circuit 1 and the voltage component detection circuit 2 of the diversity reception adapter 21. The form of the high-pass filter F is arbitrary such as a circuit using a resistor and a capacitor and a circuit using a coil and a capacitor.
In FIG. 2, the current detection terminal 23 and the voltage detection terminal 24 are configured by separate two circuit connectors, but may be combined into one four circuit connector. If one connector is used, the connection with the diversity receiver can be performed at one time, which is beneficial for labor saving. Further, in order to reduce the number of connections, it is possible to share one end of the current detection terminal 23 and one end of the voltage detection terminal 24.

  The diversity method includes “combined diversity” in which a predetermined weighting factor is added to each of the current signal ir (t) and the voltage signal vr (t) so as to optimize the communication quality, and the current signal ir (t), There is “selection diversity” in which one of the voltage signals vr (t) having the better communication quality is selected. “Communication quality is good” means, for example, a higher received power, a higher SN ratio, or a lower transmission distortion. In addition, there is a type of selection diversity in which the selection switching circuit is installed in the pre-demodulation stage or the post-demodulation stage.

The following embodiments will be described in detail by taking synthetic diversity as an example.
FIG. 3 is a block diagram illustrating an OFDM (Orthogonal Frequency Division Multiplex) scheme combining diversity receiver.
The combined diversity receiver inputs a current signal ir (t) and a voltage signal vr (t). The current signal ir (t) is converted into 2N parallel signals through the serial-parallel conversion circuit 4a that parallelizes the serialized signal every N symbols (N is 256, for example). The voltage signal vr (t) also passes through the N symbol serial / parallel conversion circuit 4b and becomes 2N parallel signals. “2” is added because the input / output of the IFFT (Inverse Fourier Transform) circuit is a complex number, and thus has an imaginary part as well as a real part. However, since the current signal ir (t) and the voltage signal vr (t) are real signals, the values of the imaginary part are all zero.

Each parallel signal is Fourier transformed by FFT circuits 5a and 5b. The Fourier-transformed signal is expressed as Ir (k), Vr (k). Here, “k” is a variable representing a discrete frequency, and k = 0, 1, 2,..., N−1.
On the other hand, the transmission path characteristics of the current signal ir (t) and the voltage signal vr (t) are estimated by the transmission path characteristics estimation sections 8a and 8b, respectively. The transmission path characteristic is a transfer function from the transmission end to the reception end of the line. For example, it can be obtained by extracting a pilot signal inserted in advance in the information transmission signal with a filter and measuring its strength and phase.

The transmission path characteristic estimators 8a and 8b output the transfer function in the frequency domain for the current signal Ir (k) and the voltage signal Vr (k). These signals are a total of 2N parallel signals of a real part and an imaginary part expressed by the same discrete frequency as the discrete frequency k, and are represented as hi (k) and hv (k), respectively.
The synthesis equalization unit 6 multiplies the weighted coefficients gi (k) and gv (k) by the signals Ir (k) and Vr (k) after each Fourier transform and adds them. The added signal R (k) is expressed as follows.

R (k) = gi (k) Ir (k) + gv (k) Vr (k)
The synthesis equalization unit 6 determines the weighting factors gi (k) and gv (k) so as to maximize the SN ratio of the signal R (k) after the addition. The weighting factors gi (k) and gv (k) are calculated using the hi (k) and hv (k).
gi (k) = h ^* i (k) / (| h ^* i (k) | ² + | h ^* v (k) | ² )
gv (k) = h ^* v (k) / (| h ^* i (k) | ² + | h ^* v (k) | ² )
Can be calculated. “*” Represents a complex conjugate.

Note that details of how to obtain the weighting factors gi (k) and gv (k) are examples of antenna diversity, but the Trikes Planning Department, "~ OFDM modulation technology for digital broadcasting / mobile communications" p.115. -See p.120, Trikes, Inc., issued March 6, 2000.
As a result, the error rate of the demodulated signal can be minimized.
Although the above transmission path characteristic estimation units 8a and 8b have determined the transmission path characteristics hi (k) and hv (k) using the pilot signal, other transmission path characteristics may be used. For example, a known symbol instead of a transmitted data symbol that inserts a known signal (such as a chirp signal or PN sequence) at appropriate intervals and measures the distortion at the receiver to estimate the channel characteristics. There is a method of estimating the transmission line characteristics by transmitting the signal at regular intervals and measuring the distortion. For details, see the above-mentioned document p.102-p.108.

The synthesis equalization unit 6 determines the weighting factors gi (k) and gv (k) so that the signal-to-noise ratio of the signal R (k) is maximized. Can be set, and the determination method is arbitrary.
The signal R (k) added by the synthesis equalization unit 6 enters the demodulator 7 and is converted into the original code string. The code string is parallel-serial converted by the N symbol parallel-serial conversion circuit 10 and extracted as information data.

As described above, this combining diversity receiver detects the current signal and voltage signal at the receiving end of the power line or telephone line, and combines the current signal and voltage signal with a predetermined weight so that the transmission characteristics are the best. Therefore, the best information transmission signal can be restored at any time.
Next, a case of a single carrier block transmission system (Single Carrier Block Transmission, SCBT, hereinafter referred to as SCBT system) will be described.

The SCBT scheme is a block transmission scheme in which a signal block composed of a plurality of information symbols is transmitted and equalization and demodulation processing is performed in units of blocks on the receiving side. GI), and a transmission method for performing discrete frequency domain equalization on the receiving side.
Here, the information transmission signal is a baseband signal for transmitting information symbols in a single frequency band, or a band signal obtained by modulating a single carrier.

As a guard interval, a copy of the transmission block tail part (cyclic prefix) inserted is called SC-CP (Single carrier block transmission with cyclic prefix) method, and it is effective by using discrete Fourier transform on the receiving side. Frequency domain equalization can be performed. For details, see 2004 Microwave Workshop Digest, p.523-532.
FIG. 4 is a block diagram showing an SCBT type combined diversity receiver used for wired communication.

  The difference between the SCBT method and the OFDM method is that in the OFDM method, an information transmission signal is subjected to inverse Fourier transform on the transmission side and sent to the transmission line, and the receiver performs Fourier transform and equalization to use the signal. In the SCBT system, the transmitter sends the signal to the transmission line without performing the inverse Fourier transform, the receiver performs the Fourier transform, equalizes in the frequency domain, and uses the inverse Fourier transform. From the viewpoint of the transmission signal spectrum, OFDM is a multi-carrier and SCBT is a single carrier.

Since the reception time signal is subjected to discrete Fourier transform on the SCBT receiver side, the contents of the present invention described above can be applied. Therefore, the SCBT type N-symbol serial / parallel conversion circuits 4a and 4b, the FFT circuit 5, the transmission path characteristic estimation units 8a and 8b, and the synthesis equalization unit 6 are substantially the same circuits as the OFDM type circuits.
In FIG. 4, the signal R (k) synthesized by the synthesis equalization unit 6 is inverse Fourier transformed by the IFFT circuit 9 and transformed into a symbol string on the time axis. The symbol string is serially converted into N symbols, demodulated by a demodulator 7, and extracted as information data.

As described above, the SCBT system diversity receiver can restore the best information transmission signal at any point in time as in the case of the OFDM system diversity receiver.
Next, a simplified combining diversity system will be described in which one of the current signal ir (t) and the voltage signal vr (t) is regarded as a real part and the other is regarded as an imaginary part.

In the circuits of FIGS. 3 and 4, the current signal ir (t) is represented by 2N parallel complex signals, of which N in the imaginary part is 0, and actually, N in the real part are required. . The voltage signal vr (t) is also expressed by 2N parallel complex signals, of which N in the imaginary part is 0, and what is actually required is N in the real part. Therefore, the FFT circuits 5a and 5b have redundant circuit configurations.
The simplified combining diversity type FFT circuit 5 is shown in FIG. The FFT circuit 5 includes a real part of a current signal ir (t) that is N parallel signals and a real part of a voltage signal vr (t) that is N parallel signals multiplied by an imaginary unit j. Sum u (t) = ir (t) + jvr (t)
Is the input signal. The input signal u (t) is Fourier-transformed, and a frequency domain signal U (k) = X (k) + jZ (k) is obtained at the output of the FFT circuit 5. Here, X (k) and Z (k) are the real part and imaginary part of U (k), respectively. Since X (k) and Z (k) are not Fourier transform values of desired current and voltage signals, they are converted into Fourier transform values Ir (k) and Vr (k) of current and voltage signals by the following calculation.

Ir (k) = [X (k) / 2 + X (Nk) / 2] + j [Z (k) / 2−Z (nk) / 2] (1)
Vr (k) = [Z (k) / 2 + Z (Nk) / 2] -j [X (k) / 2-X (nk) / 2] (2)
Where N is the number of samples in the time domain, that is, the number of FFT points, n = 0,..., N−1 (Miyakawa, Imai “Fast Fourier Transform” p.185-p.187, Science and Technology Publishers Issued December 15, 1978).
By this calculation, the Fourier transform value Ir (k) of the current signal and the Fourier transform value Vr (k) of the voltage signal can be separated from the output value of the FFT circuit 5.

Ir (k) and Vr (k) thus separated are input to the synthesis equalization unit 6. The following processing is the same as that described in FIG.
This simplified combining diversity system has an advantage that only one FFT circuit 5 is required unlike the circuits of FIGS. That is, in the circuits shown in FIGS. 3 and 4, only two FFT circuits are actually processed while using two FFT circuits 5a and 5b. However, in the circuit shown in FIG. 5, one complex time signal is composed of the N parallel signals, ie, the current signal ir (t) and the voltage signal vr (t). Can be used to process. The separation of the Fourier transform value Ir (k) of the current signal and the Fourier transform value Vr (k) of the voltage signal from the output of the FFT circuit 5 can be realized by simple four arithmetic operations. Therefore, the circuit scale of the entire FFT can be halved, the receiving apparatus can be simplified, and the same diversity effect as when the two FFT circuits are used can be obtained.

FIG. 6 is a block diagram showing a simplified combining diversity receiving apparatus of the OFDM method.
The difference between the simplified combining diversity receiving apparatus and the combining diversity receiving apparatus of FIG. 3 is that the current signal ir (t) passes through the N-symbol serial / parallel conversion circuit 14a and the N imaginary part 0 is omitted. The voltage signal vr (t) also becomes N parallel signals through the N symbol serial / parallel conversion circuit 14b. "2" is not attached.

Unlike FIG. 3, the FFT circuit 5 includes a complexing unit 51, an FFT unit 52, and a calculation unit 53.
The complexing unit 51 uses the N parallel real signals corresponding to the current signal ir (t) and the N parallel real signals corresponding to the voltage signal vr (t) to generate a complex time signal u ( t) = ir (t) + jvr (t)
make.

The FFT unit 52 performs a Fourier transform on this signal, and outputs a complex signal U (k) in the frequency domain.
The calculation unit 53 obtains Ir (k) and Vr (k) using the above-described equations (1) and (2).
As described above, the synthesis equalization unit 6 determines the weighting factors gi (k) and gv (k), multiplies the signals Ir (k) and Vr (k) after each Fourier transform, and adds them. The added signal R (k) is expressed as follows.

R (k) = gi (k) Ir (k) + gv (k) Vr (k)
The synthesis equalization unit 6 determines the weighting factors gi (k) and gv (k) so as to maximize the SN ratio of the signal R (k) after the addition. The demodulator 7 converts the signal R (k) into the original code string, and the code string is N-serial converted in parallel and extracted as information data.
FIG. 7 is a block diagram showing a simplified combining diversity receiver of the SCBT method.

The difference from the SCBT system diversity receiver of FIG. 4 is that the current signal ir (t) passes through the N symbol serial / parallel conversion circuit 14a to become N parallel signals with the imaginary part 0 omitted, and the voltage signal vr (t) also means that N parallel signals pass through the N symbol serial / parallel conversion circuit 14b.
Unlike FIG. 4, the FFT circuit 5 includes a complexing unit 51, an FFT unit 52, and a calculation unit 53.

The complexing unit 51 uses the N parallel real signals corresponding to the current signal ir (t) and the N parallel real signals corresponding to the voltage signal vr (t) to generate a complex time signal u (t). = Ir (t) + jvr (t)
The FFT unit 52 performs Fourier transform on this function, and the calculation unit 53 obtains Ir (k) and Vr (k) using the above-described equations (1) and (2). The functions of the other synthesis equalization unit 6 and IFFT circuit 9 are the same as those in FIG. As described above, even with the simplified combining diversity receiving apparatus of the OFDM system and the SCBT system, it is possible to obtain the same diversity effect as in the case where the two FFT circuits are used.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

It is a block diagram which shows the detection circuit of the information transmission signal in a power receiving end in the case of communicating by superimposing an information transmission signal on a pair of power lines or telephone lines. It is a block diagram which shows the adapter for diversity reception of this invention. It is a block diagram which shows the synthetic | combination diversity receiver of an OFDM system. It is a block diagram which shows the synthetic | combination diversity receiver of a SCBT system. FIG. 5 is a block diagram showing a simplified combining diversity type FFT circuit 5; It is a block diagram which shows the simplification synthetic | combination diversity receiver of an OFDM system. It is a block diagram which shows the simplification synthetic | combination diversity reception apparatus of a SCBT system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Current component detection circuit 2 Voltage component detection circuit 3 Load 4a, 4b N symbol serial / parallel conversion circuit 5, 5a, 5b FFT circuit 6 Synthesis | combination equalization part 7 Demodulator 8a, 8b Transmission path characteristic estimation part 9 IFFT circuit 10 N symbol Parallel-serial conversion circuits 14a and 14b N-symbol parallel-serial conversion circuit 21 Diversity reception adapter 22 Load terminal 23 Current detection terminal 24 Voltage detection terminal 51 Complexation unit 52 FFT unit 53 Operation unit

Claims (3)

A diversity reception adapter used for wired communication in which an information transmission signal is communicated by being superimposed on a pair of lines,
A voltage detection unit for detecting an information transmission signal (referred to as a voltage signal) included in the voltage detected at the receiving end of the line and its voltage detection terminal;
A current detection unit for detecting an information transmission signal (referred to as a current signal) included in the current detected at the receiving end of the line and its current detection terminal;
A load terminal for connecting a load to the line;
A diversity reception adapter for use in wired communication.   The diversity receiving adapter used for wired communication according to claim 1, wherein the line is a power line, and a load terminal for connecting the load is an AC outlet.   The diversity receiving adapter used for wired communication according to claim 1, wherein the line is a telephone line, and a load terminal for connecting the load is a telephone outlet.

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