JPS6347293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a line coupler that separates and couples transmission signals and reception signals of a power line carrier communication device.

[Conventional technology]

FIG. 1 is a block diagram showing an example of a line coupler of a conventional power line carrier communication device. That is,
A transmission signal FS inputted from an input terminal 1 is amplified to a predetermined transmission level by a transmission amplifier 2 and sent to a line 4 via a transmission band filter 3. On the other hand, the reception signal FS input from the line 4 is output from the terminal 6 via the reception band filter 5. Different frequencies are assigned to the frequency of the transmitted signal FS and the frequency of the received signal FR, and band filters 3 and 5 are set to the frequency of the transmitted signal FS and the frequency of the received signal FR, respectively.

The transmission band filter 3 filters high-level transmission signals.
It is large and expensive because it passes through FS with low loss. This is because the transmission signal needs to be transmitted at a high level and with low loss in order to prevent deterioration of the signal-to-noise ratio due to corona noise generated in the power line, line switching noise on the power side, and the like. On the other hand, since the received signal is at a low level, the reception band filter has an out-of-band attenuation amount to prevent the high-level transmission signal FS from going around.
In other words, it is designed to increase the amount of blocking attenuation. The above-mentioned situation is the same for the transmission band filter and reception band filter on the other end station side.
Furthermore, the bands of the transmitted and received signals are opposite to those described above.

[Problem that the invention seeks to solve]

Therefore, each filter must always be designed with a pass band and a stop band as a set, and when considering one pair of transmitting and receiving end station equipment, there is a drawback that four types of expensive band filters are required. There is. Furthermore, since each filter has fixed characteristics, it is impossible to adjust the impedance matching between the line and the device within the coupling circuit.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks, reduce the number of types of bandpass filters, and provide a low-cost line coupler for a power line carrier communication device that allows easy matching between the line and the device.

[Means for solving problems]

The present invention provides a line coupler for a power line carrier communication device that couples the output of a transmitting amplifier and the input of a receiving band filter whose passband is a frequency different from the output frequency of the transmitting amplifier to a line. is connected to the transmission input terminal, and the input of the reception band filter is connected to the reception output terminal. A balanced bridge type directional coupler is connected between the transmission and reception terminal of this directional coupler and the line. It is characterized by comprising a transmission/reception band filter and a balanced connection network connected to the balanced connection terminals of the directional coupler.

〔Example〕

Next, the present invention will be described in detail with reference to embodiment drawings.

FIG. 2 is a circuit diagram showing one embodiment of the present invention. In the figure, reference numerals 7 and 8 represent first and second three-winding transformers, numeral 9 represents a balanced wire network, and numeral 10 represents a transmitting/receiving band filter.

The output signal of the transmission amplifier 2 is input to the first winding terminal 101 of the first three-winding transformer 7 , and is sent out from the second winding terminal 103 to the line 4 via the transmission/reception band filter 10 . First winding of three-winding transformer 7
The connection point between N ₁ and the second winding N ₂ is connected from the terminal 102 to the third winding terminal 106 of the three-winding transformer 8 . The third winding terminal 104 of the three-winding transformer 7 is connected to the first winding N1 and the second winding _N2 of the second three-winding transformer ₈ .
Connect to connection point 109 with. Three winding transformer 7,
The other ends 105 and 107 of the third winding 8 are both grounded. The second winding terminal 108 of the second three-winding transformer 8 is connected to a balanced network (BN) 9, and the other end of the balanced network 9 is grounded. The first winding terminal 110 of the second three-winding transformer 8 is connected to the receiving band filter 5.
connected to the input of

Here, the transmitting/receiving band filter 10 transmits the transmitting signal
This is a wideband filter that passes both FS and the received signal FR. The same standard applies to the transmitting and receiving band filters used in the line couplers installed at the other party's terminal stations. That is, since only one type of transmitting/receiving band filter is required in common, the number of types of band filters can be reduced. The receiving band filters 5 each use an assigned narrow band filter.

For example, the impedance of the transmitting amplifier 2 seen from the terminal 101 and ground of the first three-winding transformer 7 and the transmitting/receiving band filter 10 from the terminal 103 and ground.
Assume that both impedances are well matched and are each 75Ω. It is assumed that the impedance of the second three-winding transformer when looking at the balanced wiring network 9 from the terminal 108 and the ground, and the impedance when looking at the reception band filter 5 from the terminal 110 and the ground are both well matched and are 75Ω.

In this case, the number of turns of the first winding of the three-winding transformers 7 and 8 is N ₁ , the number of turns of the second winding is N ₂ , the number of turns of the third winding is N ₃ , and the turns ratio N ₁ :N ₂ :N ₃ =1:1:6. As a result, the output of the transmission amplifier 2, that is, the passage loss from the terminal 101 to the terminal 103 of the first three-winding transformer 7 is only a small coupling loss generated in the transformer 7, and can be approximately 0.5 dB. . Therefore, if the passing loss of the transmitting/receiving band filter 10 is α, the transmitting signal from the transmitting amplifier 2 is transmitted to the line 4.
The amount of attenuation received before being sent to is [α + 0.5]
dB.

On the other hand, the received signal from the line 4 is affected by the loss α of the transmitting/receiving band filter 10 and the terminal 103 of the first three-winding transformer 7 to the terminal 11 of the second three-winding transformer 8.
Passage loss of about 10dB between 0 and reception band filter 5
Since it is attenuated by the passage loss β of , the total attenuation amount is [α + β + 10] dB. Therefore, terminal 6
Although the level of the received signal output from the
Both the line noise and the received signal level undergo this attenuation, and the line noise outside the receiving band is removed and the SN
The ratio is improving.

The impedances of the balanced wiring network 9, the transmitting/receiving band filter 10, and the receiving band filter 5 are each 75Ω, allowing good matching as a device.
approximately equal to. Therefore, since the bridge consisting of the three-winding transformers 7 and 8 can be set to satisfy the equilibrium condition, the transmitted signal FS from the transmitting amplifier 2
does not go around to the reception band filter 5.
This is because the transmission signal component input from the terminal 106 of the second three-winding transformer is canceled with the component flowing from the terminal 109 and input to the reception band filter 5. Therefore, the amount of out-of-band attenuation of the reception band filter 5 does not need to be so large.

Further, the transmitting/receiving band filter 10 controls the transmitting signal
Since this is a filter that passes both the FS and received signal FR bands, and is not a filter that passes only the transmission band like the conventional transmission band filter 3 shown in Fig. 1, there is an increase in loss at the end of the transmission band. etc., the design is simple and losses are reduced.

Furthermore, since the same transmitting/receiving band filter can be used in the opposite terminal station, the number of filter types can be reduced. By combining these effects, the transmitting/receiving band filter and the receiving band filter can be individually designed, which has a large economical effect.
Furthermore, even if mismatching occurs between the device and the line due to line fluctuations, matching can be easily achieved by adjusting the balanced wiring network.

To explain a balanced bridge type directional coupler that combines two three-winding transformers, the one used in this example is as described in Genzaburo Kuraishi's ``CATV Technology'', published by Dempa Shimbun Publishing, pp. 124-- This is an application of the directional coupler described on page 127. This particularly applies to the case shown in Figure 4.26 described on page 126 of the above-mentioned publication, where the turn ratio is set to 1:1:6 as described above. FIG. 3 shows an equivalent circuit for understanding the above-mentioned circuit as a bridge. The representation in Fig. 3 is equivalent to the circuit shown in Fig. 2 with the same reference numerals, and the portion 2 surrounded by the dashed-dotted line is
0 is a known balanced bridge type directional coupler. Now, the turns ratios of the two transformers 7 and 8 are both N ₁ :N ₂ :N ₃ =1:1:6, and the winding ratio between the four terminals 101, 103, 110 and 108 and the ground is It can be seen that this directional coupler is in the state of a balanced bridge since the impedances connected to it are all equal (75Ω). At this time, the transmission signal input to the transmission input terminal 101 ideally has no attenuation, but in practice it receives a small attenuation (approximately 0.5 dB) and enters the transmission/reception terminal 101.
Appears on 03. Further, the signal input to the transmitting/receiving terminal 103 is subjected to large attenuation (10 dB) and appears at the receiving output terminal 110. However, the transmission input terminal 10
1 signal is received at the receiving output terminal 1 in an ideal balanced state.
It is canceled out and does not appear in 10. That is, between the transmission input terminal 101 and the reception output terminal 110, there are 2
They are connected by two passages. Its first path is the path through which the signal at terminal 104 of winding N ₃ of transformer 7 is connected to the midpoint 109 of transformer 8, and its second path is the path through which the signal at terminal 104 of winding N 3 of transformer 7 is connected to midpoint 109 of transformer 7. is the path connected to winding N ₃ of transformer 8.
The phases of signals transmitted through these two paths are opposite to each other, and in an ideal balanced state, the signals cancel each other out, so that the signal at the transmission input terminal 101 does not appear at the reception output terminal 110.

〔Effect of the invention〕

As explained above, in the present invention, in an ideal balanced state, the transmitted signal is canceled and does not appear at the input of the receiving band filter, so the out-of-band attenuation of the receiving band filter is caused by deviation from the ideal state. It can be small enough to prevent small leaks.
Further, the transmission band filter may be of the same standard for both transmission and reception, and its characteristics may be simple enough to eliminate noise outside the band. That is, the number of types of filters is reduced, and even if the standards are loose, matching can be achieved, so there is an effect that the device can be configured with inexpensive filters.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional line coupler. FIG. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is an equivalent circuit diagram of the circuit shown in FIG. 2. 1... Input terminal, 2... Transmission amplifier, 3... Transmission band filter, 4... Line, 5... Receiving band filter, 6... Terminal, 7, 8... Three-winding transformer,
9...Balanced connection network, 10...Transmission/reception band filter, 20...Directional coupler, 101-110...
Terminals of a three-winding transformer.

Claims (1)

[Claims] 1. In a line coupler of a power line carrier communication device that couples the output of a transmission amplifier 2 and the input of a reception band filter 5 whose passband is a frequency different from the output frequency of this transmission amplifier to a line 4. , a bidirectional transmitting/receiving band filter 10 whose one end is connected to the line and whose passbands include the transmitting band and the receiving band, and a balanced connection network 9; the other end of the transmitting/receiving band filter is a transmitting/receiving terminal 1.
03, the output of the transmission amplifier is connected to the transmission input terminal 101, the input of the reception band filter is connected to the reception output terminal 110, and the balanced connection network 9 is connected to the balanced connection terminal 108. The directional coupler includes a coupler 20, which includes a path for sending the signal of the transmission input terminal 101 to the transmission/reception terminal 103, a path for sending the signal of the transmission/reception terminal 103 to the reception output terminal 110, and a path for sending the signal of the transmission input terminal 101 to the reception output terminal 110. Reception output terminal 1
1. A line coupler for a power line carrier communication device, characterized in that the line coupler includes two paths formed between the power line carrier and the power line communication device 10 and transmitting signals in opposite phases to each other. 2. The directional coupler includes a first three-winding transformer 7 and a second three-winding transformer 8, and one end of the first winding of the first three-winding transformer is connected to the transmission input terminal. 1
01, and one end of the second winding of the first three-winding transformer is connected to the transmitting/receiving terminal 103,
The other ends of the first winding and the second winding of the first three-winding transformer are connected to each other at a first midpoint terminal 102, and the first winding of the second three-winding transformer One end of the second winding of the second three-winding transformer is connected to the receiving output terminal 110, one end of the second winding of the second three-winding transformer is connected to the balanced connection terminal 108, and one end of the second winding of the second three-winding transformer is connected to the balanced connection terminal 108. The other ends of the first winding and the second winding are interconnected at a second midpoint terminal 109, and one end 105 of the third winding of the first three-winding transformer and one end of the third winding of the second three-winding transformer are connected to each other at a second midpoint terminal 109. One end 107 of the third winding of the transformer is connected to each other, the other end 104 of the third winding of the first three-winding transformer is connected to the second midpoint 109, The power line carrier communication device according to claim 1, wherein the other end 106 of the third winding of the winding transformer is a balanced bridge type directional coupler connected to the first midpoint terminal 102. line coupler.