CA1195747A - Transmitter/receiver circuit for signal transmission over power wiring - Google Patents
Transmitter/receiver circuit for signal transmission over power wiringInfo
- Publication number
- CA1195747A CA1195747A CA000417936A CA417936A CA1195747A CA 1195747 A CA1195747 A CA 1195747A CA 000417936 A CA000417936 A CA 000417936A CA 417936 A CA417936 A CA 417936A CA 1195747 A CA1195747 A CA 1195747A
- Authority
- CA
- Canada
- Prior art keywords
- circuit
- resonance circuit
- transmitter
- distribution line
- output
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Abstract Disclosed is a system of transmitting and receiving control signals for various types of devices using the existing power wiring in houses and buildings. The transmitter section of the power wiring transmission system is provided with a cir-cuit in which the output of a sine wave oscillator is fed to an emitter-follower through a photocoupler and this output is then fed to the power distribution line through a series resonance circuit after stepping down with a transformer; and the receiving section is provided with a circuit in which the signal from the distribution line is fed to a parallel resonance circuit after passing through a series resonance circuit. Moreover, the input and output sections are resistor terminated.
Description
~1~57~7 ~ his invention is in relation to a transmitter/
receiver circuit for signal transmission over power wiring.
In the transmitting section of power wiring transmis-sion, the lower the output impedance the better for effective superposing of signals on the distribution line. However, low impedance loads must be prevented from remaining on the distri-bution line and carrier leakages due to the effects o~ high level noise (thyristor noise etc.) on the input side must also be pre-vented during transmission breaks. On the one hand, in the receiving section, the higher the input impedance the better to prevent drops in signal level at the receiving point and also to prevent loading when a number of receiving units are connected.
According to the present invention is provided a transmitter/receiver circuit for power wiring transmission in which the transmitting section comprises a circuit in which the output of a sine wave oscillator is connected to an emitter-follower through a photocoupler as an isolating analogue switch and output from the emitter coupler is connected to the distribu-tion line through a series resonance circuit after passing through a step-down transformer; and that the receiving section comprises a circuit in which signal from the distribution line is fed to a parallel resonance circuit after passing through a series resonance circuit as a filter and that input and output sections of the filter are resistor terminated.
An embodiment of this invention will now be described by way of example with reference to the drawings, in which:
Figure 1 is a diagram of the electrical circuit of the ~ ' ,~g 5;7~
transmitter circuit in an example of this invention in operation;
Figures 2(a) and (b) are time charts showing examples of various types of noise, Figures 3(a) and (b) are diagrams showing alternatives to photocoupler 2 in Figure 1, Figure 4 is a diagram showing an example of the filter circuit in the receiver unit, Figure 5 is a diagram showing an example of the filter in Figure 4, inductance-coupled to increase the level, and Figure 6 is a block diagram showing the outline of the receiving system.
The electrical circuit of the transmitter shown in Figure 1 includes si.ne wave oscillator circuit 1, photocoupler (2-directional FET type) 2, current limiting resistor 3 for the photocoupler LED, transistor 4 that controls the LED by an ON-OFF
signal from the control section (microcomputer etc.)~ emitter-follower transistors 5 and 6 for lowering the impedance, decoup-ling capacitor 7, step-down transformer 8 (n:l) to lower the impedance even further, series resonance circuits 9 and 10 to isolate the distribution line voltage and feed the carrier to the distribution line at a low impedance, power supply 11, and high level distribution line noise suppression diodes 12 and 13.
Although the output impedance of normal transistor emitter-followers (5 and 6 in the diagram~ is about 15 ohm, this is not satisfactory, as the distribution line impedance is only about 2 to 5 ohm. The step-down transformer 8 is therefore used hetween the emitter-follower and the distribution line and the ii7~'7 desired impedance obtained by setting the output impedance to l/n2 (n is the turns ratio). However, it will be necessary to generate a signal of n times the final level with the sine wave oscillator circuit for -the output voltage to also be l/n. It would serve no useful purpose to lower the impedance by means of the step-down transformer 8 if the impedance at the connection to the distribution line is high. For this reason capacitor ~
and coil 10 are inserted in the form of a series resonance circuit at the connection to the distribution line. In conventional circuitry only a capacitor is usually used at connection to the distributor line.
Although operation during transmission is as explained above, consideration of transmission breaks is also necessary.
As various devices are generally connec-ted to the distribution line, various type of noise will be mixed on the line. The prin-cipal types will be thyristor noise (Fig.2(a)) and motor brush noise (vacuum cleaners etc., Fig. 2(b)). These noise levels reach a maximum of 30V for thyristor and 2V for vacuum PP PP
cleaners. These noise frequencies pass through the series reso nance circuit 9, 10 and are added to the base of emitter-follower 5, 6 after being stepped up through transformer 8.
However, as photocoupler 2 acts as an isolating analog switch, the emitter-follower will be in a completely isolated OFF state and will therefore not load the distribution line as its output impedance is high. Although the secondary impedance of step-down transformer 8 will he the direct load during ~he OFF
state, there will therefore be practically no problem if a suffi-ciently high impedance (over lmH) is selected. Also, as the ~.~
i;7ql~
control of the analog switch is completely isolated from the switch, there will be no adverse e~fects even if there is line noise present on the base.
In conventional circuitry the switch and control parts are not completely isolated in normal analog switches (transistors, FET's, CMOS's etc.), and some carrier leakage to the distribution line will occur for ON commands issued by the control section when the level at point A (base of emitter-follower 5, 6) becomes momentarily high or low. If point A is grounded through a resistor or capacitor in an attempt to prevent this, a low impedance load will be presented to the distribution line as emitter-follower 5, 6 will not be completely isolated.
As each power wiring transmission section is normally made up of a transmittex/receiver pair, load is applied even during OFF
periods of the transmitter. When a large number of units are connected for an answer back service the result is unsatisfactory.
The present invention aims to overcome these problems.
Instead of the 2-way FET shown in Figure 1, photo transistors (2 sets used to obtain 2-way characteristics) con-nected as shown in Figure 3(a) and (b) and CDS can also be used for photocoupler 2. Photothyristors are less suitable as they are turned ON easily but require additional circuitry to turn OFF and switching speed is slow.
In po~ler wiring transmission using an ~M system, data transmission is carried out by turning a special carrier frequency ON and OFF. To block the distribution line voltage and effectively remove the noise elements, the narrower the band ~' i'?
width of the filter used the better the results. The higher the input impedance the better at the receiving point to prevent attenuation of the signal and to prevent loading when a number of receiving circuits are connected. A signal tuning circuit is normally used in this section, but is no-t wholly considering the foregoing problems. As shown in Figure 4, an embodiment of the invention utilises a series resonance circuit composed of capacitor Cl and coil Ll as a filter at the connection to the distribution line and a parallel resonance circuit composed of capacitor C2 and coil L2 on the load side. If the circuit within the dotted lines in Figure 4 satisfies the following condition, it can be treated as a constant-K filter and this simplifies design.
1 1 C2L2 --------------------(13 The various parameters of the filter may be obtained as follows:
Characteristic impedance: ~o = ~ ( = ~ ) -----(2) Center frequency: ~ o = (= ~ -(3) ~ 2 2 Bandwidth: ~ = Cl ( C2~o The characteristic impedance determines the impedance at the input and output sections of the filter and can be arbi-trarily selected by means of Cl, C2, L1 and L2. However, if we select 1 k ohm as the impedance so as to overcome the load effect, the anticipated filter characteristics will not be obtained as there will be a mismatch with a line impedance of only about 2 to 5 ohm. In the described embodiment of this invention, resistors Rl and R2 have been used to match the input/output sections with -the characteristic impedance. I~hen Z0 .. distribution line impe-dance and also Z0 ,, input impedance of the next stage (inputs to emitter-follower, MOS etc.), the following can be selected.
1 R2 = Z0 ~~~~~~~~~~~~~~ (5) ~he receiving level in this condition will be 1/2 the level on the distribution line.
If a coil with ratio l:n is added as shown in Figure 5 to isolate the portion following the output of the filter from the distribution line and also give additional voltage gain, a re-ceiving level of n/2 will be realized. Although R2 may be reposi-tioned in the secondary at this time, its equivalen-t value must be n R2. Demodulation is carried out by means of an amplifier and level detector connected after the filter. In Figure 6, 14 is the filter, 15 the amplifier and 16 the level detector.
receiver circuit for signal transmission over power wiring.
In the transmitting section of power wiring transmis-sion, the lower the output impedance the better for effective superposing of signals on the distribution line. However, low impedance loads must be prevented from remaining on the distri-bution line and carrier leakages due to the effects o~ high level noise (thyristor noise etc.) on the input side must also be pre-vented during transmission breaks. On the one hand, in the receiving section, the higher the input impedance the better to prevent drops in signal level at the receiving point and also to prevent loading when a number of receiving units are connected.
According to the present invention is provided a transmitter/receiver circuit for power wiring transmission in which the transmitting section comprises a circuit in which the output of a sine wave oscillator is connected to an emitter-follower through a photocoupler as an isolating analogue switch and output from the emitter coupler is connected to the distribu-tion line through a series resonance circuit after passing through a step-down transformer; and that the receiving section comprises a circuit in which signal from the distribution line is fed to a parallel resonance circuit after passing through a series resonance circuit as a filter and that input and output sections of the filter are resistor terminated.
An embodiment of this invention will now be described by way of example with reference to the drawings, in which:
Figure 1 is a diagram of the electrical circuit of the ~ ' ,~g 5;7~
transmitter circuit in an example of this invention in operation;
Figures 2(a) and (b) are time charts showing examples of various types of noise, Figures 3(a) and (b) are diagrams showing alternatives to photocoupler 2 in Figure 1, Figure 4 is a diagram showing an example of the filter circuit in the receiver unit, Figure 5 is a diagram showing an example of the filter in Figure 4, inductance-coupled to increase the level, and Figure 6 is a block diagram showing the outline of the receiving system.
The electrical circuit of the transmitter shown in Figure 1 includes si.ne wave oscillator circuit 1, photocoupler (2-directional FET type) 2, current limiting resistor 3 for the photocoupler LED, transistor 4 that controls the LED by an ON-OFF
signal from the control section (microcomputer etc.)~ emitter-follower transistors 5 and 6 for lowering the impedance, decoup-ling capacitor 7, step-down transformer 8 (n:l) to lower the impedance even further, series resonance circuits 9 and 10 to isolate the distribution line voltage and feed the carrier to the distribution line at a low impedance, power supply 11, and high level distribution line noise suppression diodes 12 and 13.
Although the output impedance of normal transistor emitter-followers (5 and 6 in the diagram~ is about 15 ohm, this is not satisfactory, as the distribution line impedance is only about 2 to 5 ohm. The step-down transformer 8 is therefore used hetween the emitter-follower and the distribution line and the ii7~'7 desired impedance obtained by setting the output impedance to l/n2 (n is the turns ratio). However, it will be necessary to generate a signal of n times the final level with the sine wave oscillator circuit for -the output voltage to also be l/n. It would serve no useful purpose to lower the impedance by means of the step-down transformer 8 if the impedance at the connection to the distribution line is high. For this reason capacitor ~
and coil 10 are inserted in the form of a series resonance circuit at the connection to the distribution line. In conventional circuitry only a capacitor is usually used at connection to the distributor line.
Although operation during transmission is as explained above, consideration of transmission breaks is also necessary.
As various devices are generally connec-ted to the distribution line, various type of noise will be mixed on the line. The prin-cipal types will be thyristor noise (Fig.2(a)) and motor brush noise (vacuum cleaners etc., Fig. 2(b)). These noise levels reach a maximum of 30V for thyristor and 2V for vacuum PP PP
cleaners. These noise frequencies pass through the series reso nance circuit 9, 10 and are added to the base of emitter-follower 5, 6 after being stepped up through transformer 8.
However, as photocoupler 2 acts as an isolating analog switch, the emitter-follower will be in a completely isolated OFF state and will therefore not load the distribution line as its output impedance is high. Although the secondary impedance of step-down transformer 8 will he the direct load during ~he OFF
state, there will therefore be practically no problem if a suffi-ciently high impedance (over lmH) is selected. Also, as the ~.~
i;7ql~
control of the analog switch is completely isolated from the switch, there will be no adverse e~fects even if there is line noise present on the base.
In conventional circuitry the switch and control parts are not completely isolated in normal analog switches (transistors, FET's, CMOS's etc.), and some carrier leakage to the distribution line will occur for ON commands issued by the control section when the level at point A (base of emitter-follower 5, 6) becomes momentarily high or low. If point A is grounded through a resistor or capacitor in an attempt to prevent this, a low impedance load will be presented to the distribution line as emitter-follower 5, 6 will not be completely isolated.
As each power wiring transmission section is normally made up of a transmittex/receiver pair, load is applied even during OFF
periods of the transmitter. When a large number of units are connected for an answer back service the result is unsatisfactory.
The present invention aims to overcome these problems.
Instead of the 2-way FET shown in Figure 1, photo transistors (2 sets used to obtain 2-way characteristics) con-nected as shown in Figure 3(a) and (b) and CDS can also be used for photocoupler 2. Photothyristors are less suitable as they are turned ON easily but require additional circuitry to turn OFF and switching speed is slow.
In po~ler wiring transmission using an ~M system, data transmission is carried out by turning a special carrier frequency ON and OFF. To block the distribution line voltage and effectively remove the noise elements, the narrower the band ~' i'?
width of the filter used the better the results. The higher the input impedance the better at the receiving point to prevent attenuation of the signal and to prevent loading when a number of receiving circuits are connected. A signal tuning circuit is normally used in this section, but is no-t wholly considering the foregoing problems. As shown in Figure 4, an embodiment of the invention utilises a series resonance circuit composed of capacitor Cl and coil Ll as a filter at the connection to the distribution line and a parallel resonance circuit composed of capacitor C2 and coil L2 on the load side. If the circuit within the dotted lines in Figure 4 satisfies the following condition, it can be treated as a constant-K filter and this simplifies design.
1 1 C2L2 --------------------(13 The various parameters of the filter may be obtained as follows:
Characteristic impedance: ~o = ~ ( = ~ ) -----(2) Center frequency: ~ o = (= ~ -(3) ~ 2 2 Bandwidth: ~ = Cl ( C2~o The characteristic impedance determines the impedance at the input and output sections of the filter and can be arbi-trarily selected by means of Cl, C2, L1 and L2. However, if we select 1 k ohm as the impedance so as to overcome the load effect, the anticipated filter characteristics will not be obtained as there will be a mismatch with a line impedance of only about 2 to 5 ohm. In the described embodiment of this invention, resistors Rl and R2 have been used to match the input/output sections with -the characteristic impedance. I~hen Z0 .. distribution line impe-dance and also Z0 ,, input impedance of the next stage (inputs to emitter-follower, MOS etc.), the following can be selected.
1 R2 = Z0 ~~~~~~~~~~~~~~ (5) ~he receiving level in this condition will be 1/2 the level on the distribution line.
If a coil with ratio l:n is added as shown in Figure 5 to isolate the portion following the output of the filter from the distribution line and also give additional voltage gain, a re-ceiving level of n/2 will be realized. Although R2 may be reposi-tioned in the secondary at this time, its equivalen-t value must be n R2. Demodulation is carried out by means of an amplifier and level detector connected after the filter. In Figure 6, 14 is the filter, 15 the amplifier and 16 the level detector.
2~
,~ ~
,~ ~
Claims (5)
1. A transmitter/receiver circuit for power wiring transmission in which the transmitting section comprises a circuit in which the output of a sine wave oscillator is connected to an emitter-follower through a photocoupler as an isolating analog switch and output from the emitter coupler is connected to the distribution line through a series resonance circuit after passing through a step-down transformer; and that the receiving section comprises a circuit in which signal from the distribution line is fed to a parallel resonance circuit after passing through a series resonance circuit as a filter and that input and output sections of the filter are resistor terminated.
2. A transmitter receiver circuit as claimed in claim 1 in which the photocoupler comprises a two way field effect transistor.
3. A transmitter/receiver circuit as claimed in claim 1 in which the series resonance circuit of the transmitting section comprises a capacitor and an impedance coil.
4. A transmitter/receiver circuit as claimed in claim 1 in which the series resonance circuit and the parallel resonance circuit of the receiving section filter each comprises a capacitor and an impedance coil.
5. A transmitter/receiver circuit as claimed in claim 4 in which the series resonance circuit and the parallel resonance circuit of the receiving section filter each comprises a terminat-ing resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000417936A CA1195747A (en) | 1982-12-16 | 1982-12-16 | Transmitter/receiver circuit for signal transmission over power wiring |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000417936A CA1195747A (en) | 1982-12-16 | 1982-12-16 | Transmitter/receiver circuit for signal transmission over power wiring |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1195747A true CA1195747A (en) | 1985-10-22 |
Family
ID=4124169
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000417936A Expired CA1195747A (en) | 1982-12-16 | 1982-12-16 | Transmitter/receiver circuit for signal transmission over power wiring |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1195747A (en) |
-
1982
- 1982-12-16 CA CA000417936A patent/CA1195747A/en not_active Expired
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Legal Events
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|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |