Source: https://patents.google.com/patent/EP1039644B1/en
Timestamp: 2019-07-18 08:12:09
Document Index: 418411966

Matched Legal Cases: ['art 22', 'art 22', 'art 2', 'art 2', 'art 2', 'art 2', 'art 2', 'art 2', 'art 81', 'art 81', 'art 11', 'art 11', 'art 11', 'art 11']

EP1039644B1 - Multi-level signal discriminator - Google Patents
Multi-level signal discriminator Download PDF
EP1039644B1
EP1039644B1 EP20000105384 EP00105384A EP1039644B1 EP 1039644 B1 EP1039644 B1 EP 1039644B1 EP 20000105384 EP20000105384 EP 20000105384 EP 00105384 A EP00105384 A EP 00105384A EP 1039644 B1 EP1039644 B1 EP 1039644B1
EP20000105384
EP1039644A2 (en
EP1039644A3 (en
1999-03-26 Priority to JP8331199 priority Critical
1999-03-26 Priority to JP8331199 priority
2000-03-21 Application filed by Panasonic Corp filed Critical Panasonic Corp
2000-09-27 Publication of EP1039644A2 publication Critical patent/EP1039644A2/en
2004-04-07 Publication of EP1039644A3 publication Critical patent/EP1039644A3/en
2006-01-04 Publication of EP1039644B1 publication Critical patent/EP1039644B1/en
Furthermore, in a transmission system of a binary signal indicative of "Hi" or "Lo", the receiving side may perform amplitude discrimination with a discriminator CD as shown in FIG. 12. In FIG. 12, the discriminator CD is adapted to automatically generate a threshold that is appropriate for amplitude discrimination (so-called automatic threshold control) even if the amplitude of the received binary signal may fluctuate. The discriminator CD includes an input terminal 21, a branching part 22, a peak detector 23, a base level generator 24, a threshold generator 25, and a comparator 26.
The branching part 22 branches a binary signal fed through the input terminal 21 into two, outputting one to the peak detector 23 and the other to the comparator 26. The peak detector 23 detects and holds a peak value of the received binary signal. The detected peak value is equal in electric potential to "Hi" of the binary signal which may fluctuate, and fed to the threshold generator 25. The base level generator 24 generates a base level equal in electric potential to "Lo" of the binary signal, and outputs the base level to the threshold generator 25. The threshold generator 25 generates a threshold having a mid-level between the received peak level and base level, and outputs the threshold to the comparator 26. The comparator 26 compares the amplitude of the branched binary signal with the threshold, and outputs the comparison result. As such, the peak detector 23 detects the peak value of the binary signal, enabling the threshold generator 25 to automatically generate the threshold even with fluctuations in amplitude of the binary signal.
An example of such an amplitude discriminator is described in JP 06-310967, in which a peak level detection latch circuit and a bottom level detection latch circuit are utilized to extract a peak and a bottom level of an input signal. The median of the peak and bottom level is then given as a threshold level of an amplitude limit amplifier circuit
A first aspect of the present invention is directed to a discriminator discriminating a multi-level signal varying in amplitude among three or more values, comprising: a first branching part branching the multi-level signal externally inputted thereto into two; a wave-shaping circuit shaping a waveform of the multi-level signal branched by the first branching part a detector detecting a first reference level based on an output signal from the wave-shaping circuit; a reference level generator generating a second reference level of the multi-level signal externally inputted; a threshold generator generating a required number of thresholds according to the first and second reference levels; a comparing circuit comparing the amplitude of the multi-level signal branched by the first branching part with the thresholds generated by the threshold generator; and a control signal generator generating a control signal indicative of a time interval in which one or more specific amplitude values of the multi- level signal are excessively distributed according to a comparison result by the comparing circuit, and wherein the wave-shaping circuit shaping the waveform of the multi-level signal inputted thereto according to the control signal outputted from the control signal generator so that the detector can correctly detect the first reference level.
According to a second aspect, in the first aspect, the threshold generator generates (the number of amplitude values - 1) different thresholds according to the first and second reference levels, the comparing circuit comprises: a second branching part branching the multi-level signal inputted thereto into (the number of amplitude values - 1); and (the number of amplitude values - 1) comparators each receiving different one of the thresholds generated by the threshold generator and the multi-level signal branched by the second branching part, and each of the comparators compares the amplitude of the received multi-level signal with the received threshold.
According to a third aspect, in the first aspect, the reference level generator generates the second reference level having an electric potential while the multi-level signal having a base level is sent.
In the third aspect, the second reference level can be easily generated.
According to a fourth aspect, in the first aspect, the control signal defines a time interval during which one or more predetermined amplitude values are excessively distributed in the multi-level signal, and the wave-shaping circuit shapes the waveform of the multi-level signal inputted thereto so that one of the predetermined amplitude values becomes equal to the second reference level during the time interval defined by the control signal.
In the fourth aspect, the control signal generator generates a control signal that defines a time interval during which one or more predetermined amplitude values are excessively distributed in the multi-level signal, according to the comparison result from the comparing circuit, and feeds-back the control signal to the wave-shaping circuit. Therefore, the wave-shaping circuit can appropriately shapes the waveform of the multi-level signal currently being received by the discriminator.
A fift aspect is directed to a discriminator discriminating a multi-level signal varying in amplitude among three or more values, comprising: a first branching part branching the multi-level signal externally inputted thereto into three and outputting first to third multi-level signals; a first wave-shaping circuit shaping a waveform of the first multi-level signal outputted from the first branching part a first detector detecting a first reference level from an output signal from the first wave-shaping circuit; a second wave-shaping circuit shaping a waveform of the second multi-level signal outputted from the first branching part under a predetermined condition; a second detector detecting a second reference level from a signal outputted from the second wave-shaping circuit; a threshold generator generating a required number of thresholds according to the first and second reference levels; a comparing circuit comparing the amplitude of the third multi-level signal outputted from the first branching part with the thresholds generated by the threshold generator; and a control signal generator generating a control signal indicative of a time interval in which one or more specific amplitude values of the multi-level signal are excessively distributed according to a comparison result by the comparing circuit, and wherein the first wave-shaping circuit shaping the waveform of the first multi-level signal inputted thereto according to the control signal outputted from the control signal generator so that the first detector can correctly detect the first reference level, and the second wave-shaping circuit shaping the waveform of the second multi-level signal inputted thereto according to the control signal outputted from the control signal generator so that the second detector can correctly detect the second reference level.
According to a sixth aspect, in the sixth aspect, the threshold generator generates (the number of amplitude values - 1) different thresholds according to the first and second reference levels, the comparing circuit comprises: a second branching part branching the third multi-level signal inputted thereto into (the number of amplitude values - 1) ; and (the number of amplitude values - 1) comparators each receiving different one of the thresholds generated by the threshold generator and the third multi-level signal branched by the second branching part, and each of the comparators compares the amplitude of the received third multi-level signal with the received threshold.
In the fifth and sixth aspects, even when the discriminator receives a multi-level signal in which one or more specific amplitude values are excessively distributed during a time interval, the first and second wave-shaping circuits can perform wave-shaping according to the control signal. Therefore, the comparing circuit can discriminate the amplitude of the multi-level signal using correct thresholds. This amplitude discrimination enables generation of the multi-level signal in the transmitting side with less restrictions.
According to a seventh aspect, in the fifth aspect, the control signal defines a time interval during which one or more predetermined amplitude values are excessively distributed in the multi-level signal, and the first and second wave-shaping circuits shape the waveforms of the first and second multi-level signals inputted thereto so that one of the predetermined amplitude value becomes equal to the first and second reference levels, respectively, during the time interval defined by the control signal.
An eight aspect is directed to a discriminator discriminating a multi-level signal varying in amplitude among three or more values, comprising: a first branching part branching the multi-level signal externally inputted thereto into two; a first wave-shaping circuit shaping a waveform of the multi-level signal outputted from the first branching part a second wave-shaping circuit shaping a waveform of an output signal from the first wave-shaping circuit a first detector detecting a first reference level based on an output signal from the second wave-shaping circuit; a second detector detecting a second reference level based on the output signal from the second wave-shaping circuit; a threshold generator generating a required number of thresholds according to the first and second reference levels, a comparing circuit comparing the amplitude level of the multi-level signal branched by the first branching part with the thresholds generated by the threshold generator; and a control signal generator generating a control signal indicative of a time interval in which one or more specific amplitude values of the multi-level signal are excessively distributed according to a comparison result by the comparing circuit, and wherein the first wave-shaping circuit shaping the waveform of the multi-level signal inputted thereto according to the control signal outputted from the control signal generator so that the first detector can correctly detect the first reference level, and the second wave-shaping circuit shaping the waveform of the output signal from the first wave-shaping circuit according to the control signal outputted from the control signal generator so that the second detector can correctly detect the second reference level.
According to a ninth aspect, in the eighth aspect, the threshold generator generates (the number of amplitude values - 1) different thresholds according to the first and second reference levels, the comparing circuit comprises: a second branching part branching the multi-level signal inputted thereto into (the number of amplitude values - 1); and (the number of amplitude values - 1) comparators each receiving different one of the thresholds generated by the threshold generator and the multi-level signal branched by the second branching part, and each of the comparators compares the amplitude of the received multi-level signal with the received threshold.
In the eighth and ninth aspects, even when the discriminator receives a multi-level signal in which one or more specific amplitude values are excessively distributed during a time interval, the first and second wave-shaping circuits can perform wave-shaping according to the control signal. Therefore, the comparing circuit can discriminate the amplitude of the multi-level signal using correct thresholds. This amplitude discrimination enables generation of the multi-level signal in the transmitting side with less restrictions.
According to a tenth aspect, in the eighth aspect, the control signal defines a time interval during which one or more predetermined amplitude values are excessively distributed in the multi-level signal, and the first and second wave-shaping circuits shape the waveform of respective received signal so that one of the predetermined amplitude values become equal to the first and second reference levels, respectively, during the time interval defined by the control signal.
FIG. 3a is a diagram showing values of thresholds Th1, Th2, and Th3 ;
With reference to FIG. 1a, described first is a multi-level signal MS to be inputted to a discriminator D1 according to a first embodiment of the present invention. The multi-level signal MS is a signal in which each symbol is represented by any one of n amplitude values (n is a natural number not less than 3). In FIG. 1a , a case where n = 4 is exemplarily shown. Here, by way of explanation only, assume that the multi-level signal MS is represented by amplitude values "W", "X" , "Y" , and "Z" (W > X > Y > Z). Further, assume that |W - X| = |X - Y| = |Y - Z| = ΔV.
The multi-level signal MS is generated at a transmitting side in a transmission system. The multi-level signal MS does not have to be a signal with moderately-mixed amplitude values, but may be a signal with one or more specific amplitude values excessively distributed. In the multi-level signal MS of FIG. 1a, the amplitude value "W" is not present in time intervals T1 and T3, but is excessively distributed in a time interval T2.
Resistances R32 and R33 of the resistors 32 and 33, respectively, are determined according to the format of the multi-level signal MS and/or the specifications of the discriminator D1. An example of the resistances R32 and R33 is now described. In the first embodiment, assume that the first reference level RL1 is selected to be substantially equal in electric potential to the amplitude value "X". Also assume that the wave-shaping circuit 3 adjusts the amplitude value "W" to the first reference level RL1 according to the specifications of the discriminator D1. Under these assumptions, the resistances R32 and R33 are selected to be at a ratio of 1:2.
The gate of the transistor 31 is provided with the control signal CS from the control signal generator 10. As will be described in detail, when determining that the amplitude value "W" is excessively distributed in the multi-level signal MS, the control signal generator 10 generates a control signal CS having a "Hi" level. Otherwise, the control signal generator 10 generates a control signal CS having a "Lo" level (refer to FIG. 1b).
"Hi" of the control signal CS brings the transistor 31 out of conduction. In this case, the wave-shaping circuit 3 divides the voltage of the output signal from the first branching part 2 with the resistors 32 and 33, and then outputs the voltage-divided signal to the anode of the diode 41.
"Lo" of the control signal CS brings the transistor 31 into conduction. As a result, the multi-level signal MS from the first branching part 2 is directly fed to the anode of the diode 41.
Described next is one specific example of the operation of the wave-shaping circuit 3. As evident from above, with the multi-level signal MS having a waveform as shown in FIG. 1a fed to the discriminator D1, the control signal generator 10 inputs to the transistor 31 the control signal CS indicative of "Hi" during the time interval T2, and the control signal CS indicative of "Lo" during the time intervals T1 and T3 (refer to FIG. 1b). Therefore, the wave-shaping circuit 3 inputs the multi-level signal MS from the first branching part 2 to the anode of the diode 41 during the time intervals T1 and T3. On the other hand, during the time interval T2, the wave-shaping circuit 3 first divides the voltage of the multi-level signal MS from the first branching part 2, and then outputs a signal OS3 to the anode of the diode 41. Consequently, since the input multi-level signal MS is attenuated to two-thirds during the time interval T2, the waveform of the output signal OS3 from the wave-shaping circuit 3 becomes as such shown in FIG. 1c, with its peak value during the time interval T2 substantially equal in electric potential to the amplitude value "X".
Described next is one specific example of the operation of the detector 4. In the first embodiment, the anode of the diode 41 is provided with the signal shown in FIG. 1c. The capacitor 42 detects and holds the amplitude value "X" as the first reference level RL1. Therefore, as shown in FIG. 1d, the first reference level RL1 from the detector 4 has an electric potential that is constant in time and equal to the amplitude value "X".
The reference level generator 5 generates a second reference level RL2 for the multi-level signal MS. In the preferred embodiment, assume that the second reference level RL2 is selected to be substantially equal in electric potential to a base level of the multi-level signal MS (that is, amplitude value "Z"). Furthermore, in the first embodiment, the optical receiver Rx is placed at front of the discriminator D1. In such case, the reference level generator 5 is preferably constructed of a dummy optical receiver 51. The dummy optical receiver 51 has the same input/output characteristics as those of the optical receiver Rx placed at front of the discriminator D1. An output terminal of the dummy optical receiver 51 is coupled to the resistor 33, a resistor 64 (described later) of the threshold generator 6, and a resistor 72 (described later) of the amplitude adjuster 7. From this output terminal, an electric potential when the multi-level signal MS is not transmitted is outputted as the second reference level RL2.
In the first embodiment, the optical receiver Rx outputs the multi-level signal MS shown in FIG. 1a to the input terminal 1. Therefore, from the output terminal of the dummy optical receiver 51, the base level of the multi-level signal MS (amplitude value "Z") is outputted as the second reference level RL2.
When the optical receiver Rx is not placed at front of the discriminator D1 (that is, in electrical transmission), the reference level generator 5 is preferably constructed of a reference electric potential generator. The reference electric potential generator generates an electric potential equal to the base level of the multi-level signal MS (that is, amplitude value "Z") .
Here, described is an example of resistances R61 to R64 of the resistors 61 to 64 and resistances R71 and R72 of the resistors 71 and 72. The resistances R61 to R64, R71 and R72 are determined according to the format of the multi-level signal MS and/or the specifications of the discriminator D1, and these resistances are related one another. For example, assume that the resistances R61 to R64 are selected to satisfy the relation of R61 : R62 : R63 : R64 = 1 : 2 : 2 : 1. Further, one input terminal of the threshold generator 6 is provided with the first reference level RL1 (which is equal to the amplitude value "X" in electric potential) , while the other input terminal provided with the second reference level RL2 (which is equal to the amplitude value "Z" in electric potential) . In this case, the thresholds Th1, Th2, and Th3 have values of 5X/6, X/2, and X/6, respectively, relative to the second reference level RL2. Here, the amplitude value "X" is 2 Δ V relative to the amplitude value "Z". Therefore, as shown in FIG. 3a, the threshold generator 6 inputs to the comparing circuit 8 thresholds Th1 = 5 ΔV/3, Th2 = ΔV, and Th3 = ΔV/3 through the lead lines 65, 66, and 67, respectively.
In general, it is preferred for amplitude discrimination of the multi-level signal MS shown in FIG. 1a that each of three thresholds Th1', Th2', and Th3' be selected at a center level between one amplitude level and the amplitude level just one level below or above, normally 5ΔV/2, 3ΔV/2, and ΔV/2, respectively, relative to the amplitude value "Z". In this case, the following equation holds: (Th1/Th1') = (Th2/Th2') = (Th3/Th3') = 2/3. Therefore, for correct amplitude discrimination of the multi-level signal MS outputted from the first branching part 2 with the thresholds Th1, Th2, and Th3, the resistances R71 and R72 are preferably selected to be at a ratio of 1 : 2. In such case, the amplitude adjuster 7 divides the voltage of the multi-level signal MS branched by the branching part 2 to generate a signal OS7 with an amplitude equal to 2/3 of that of the branched multi-level signal MS shown in FIG. FIG. 3b. Then, the amplitude adjuster 7 outputs the generated signal OS7 to the comparing circuit 8.
The comparing circuit 8 compares the amplitude of the signal OS7 outputted from the amplitude adjuster 7 with the thresholds Th1, Th2, and Th3 from the threshold generator 6. The comparison result indicates discrimination result of the multi-level signal MS inputted to the discriminator D1. In general, for discrimination of a four-level signal, the comparing circuit 8 includes the second branching part 81 and the three comparators 82 to 84. The second branching part 81 branches the signal OS7 outputted from the amplitude adjuster 7 into three. Each of the comparators 82 to 84 is provided with the branched signal OS7. The comparators 82 to 84 are further provided with the thresholds Th1 to Th3 through the lead lines 65 to 67, respectively. The comparator 82 compares magnitudes between the amplitude of the received signal OS7 and the threshold Th1, and outputs the result represented by "Hi" or "Lo". Similarly, the comparators 83 and 84 compare magnitudes between the amplitude of the received signal OS7 and the thresholds Th2 and Th3, respectively, and output the results represented by "Hi" or "Lo".
With the above described configuration, when the amplitude of the multi-level signal MS inputted to the discriminator D1 is "W", all comparators 82 to 84 output the results indicative of "Hi" through the output terminals 91 to 93 to the external device. When the amplitude value is "X", only the comparators 83 and 84 output the results indicative of "Hi" through the output terminals 92 and 93. When the amplitude value is "Y", only the comparator 84 outputs the result indicative of "Hi" through the output terminal 93. When the amplitude value is "Z", all comparators 82 to 84 output the results indicative of "Lo" through the output terminals 91 to 93.
The above results are also transmitted to the control signal generator 10. By way of example only, a comparison result {Hi, Hi, Hi} indicates that all comparators 82 to 84 output the results indicative of "Hi". a comparison result {Lo, Hi, Hi} indicates that only the comparators 83 and 84 output the results indicative of "Hi". A comparison result {Lo, Lo, Hi} indicates that only the comparator 84 outputs the result indicative of "Hi". A comparison result {Lo, Lo, Lo} indicates that all comparators 82 to 84 output the results indicative of "Lo".
The control signal generator 10 is implemented typically by a CPU (Central Processing Unit) , FPGA (Field Programmable Gate Array) , or a logic circuit. Based on the comparison result from the comparing circuit 8, the control signal generator 10 generates the control signal CS (refer to FIG. 1b), and outputs the control signal CS to the gate of the transistor 31. Described below is an example of methods for generating the control signal CS.
When determining Nw > NREF, the control signal generator 10 assumes that the amplitude value "W" is excessively distributed in the multi-level signal MS that the discriminator D1 currently received, and generates the control signal CS indicative of "Hi".
On the other hand, when determining Nw ≦ NREF, the control signal generator 10 assumes that the amplitude value "W" is not excessively distributed in the multi-level signal MS the discriminator D1 currently received, and generates the control signal CS indicative of "Lo".
The control signal CS is generated as described above. According to this generation method, with the multi-level signal MS of FIG. 1a inputted to the discriminator D1, the control signal CS substantially indicative of "Lo" is generated during the time intervals T1 and T3, and sent to the wave-shaping circuit 3. The control signal CS substantially indicative of "Hi" is generated during the time interval T2, and sent to the wave-shaping circuit 3. Note that the time intervals of the control signals CS indicative of "Hi" and "Lo" of the control signal CS may be slightly shifted depending on NPRE, NW, and NREF selected.
Described next is technical effects of the discriminator D1. When the conventional discriminator CD (refer to FIG. 12) is applied for discrimination of the multi-level signal MS, the peak detector 23 is provided with the multi-level signal MS without wave-shaping. Therefore, the charge electric potential of its capacitor equal to the amplitude value "W" or "X", and becomes unstable. Consequently, the discriminator CD cannot generate correct thresholds and cannot perform correct amplitude discrimination of the multi-level signal MS in which one or more specific amplitude values are excessively distributed during a certain time interval (refer to FIG. 1a). In such case, the transmitting side has to generate a multi-level signal in which its maximum amplitude value appears at predetermined regular intervals and each amplitude value is moderately distributed.
On the other hand, according to the discriminator D1, with the multi-level signal MS as shown in FIG. 1a inputted thereto, the control signal CS indicates "Hi" during the time interval T2, bringing the switch (transistor 31) out of conduction during that time interval. As a result, the wave-shaping circuit 3 divides the voltage of the amplitude of the multi-level signal MS into two-thirds during the time interval in which the amplitude value "W" is excessively distributed in the multi-level signal MS, such as the time interval T2. Therefore, the charge electric potential of the capacitor 42 is not over the first reference level RL1, which becomes constant at the electric potential equal to that of the amplitude value "X". Therefore, the threshold generator 6 can generate constant thresholds Th1, Th2, and Th3, allowing correct discrimination of the multi-level signal MS.
Furthermore, in the first embodiment, the wave-shaping circuit 3 inputs the signal shown in FIG. 1c to the detector 4, and the first reference level RL1 is selected to be equal in electric potential to the amplitude value "X". Therefore, the detector 4 has the structure to detect the peak value of the received signal. The detector 4, however, may have the structure as shown in FIG. 4a, on condition that the voltage-division ratio of the resistances R61 to R64 and/or the resistances R71 and R72 also be appropriately selected since the first reference level RL1 is equal in electric potential to the average value of the input signal to the detector 4.
Still further, in the first embodiment, the wave-shaping circuit 3 is implemented by a voltage-divider. However, the wave-shaping circuit 3 may be implemented by an amplifier capable of varying its amplification factor with the control signal CS as shown in FIG. 4b. For example, assume that the discriminator D1 is provided with a multi-level signal MS as shown in FIG. 5a. In the multi-level signal MS of FIG. 5a, the amplitude value "Z" is not present during time intervals T4 and T6, but the amplitude value "Y" is moderately distributed. Further, the amplitude value "Z" is excessively distributed during a time interval T5. The amplification factor of the amplifier shown in FIG. 4b is set to 2/3 during the time interval T5, amplifying (attenuating) the amplitude of the received multi-level signal MS to two-thirds relative to the amplitude value "W". During the time intervals T4 and T6, the amplification factor is set to 1. As a result, as shown in FIG. 5b, an output signal having a bottom value equal in electric potential to the amplitude value "Y" appears at the output terminal of the amplifier, and inputted to the detector 4.
Still further, a transistor may be coupled to between the detector 4 as shown in FIG. 2, 4a, or 4b and the wave-shaping circuit 3 as shown in FIG. 2 or 4b, to compose a buffer.
The first branching part 11 is provided with a multi-level signal MS as shown in FIG. 7a through the input terminal 1. Here, assume that the multi-level signal MS of FIG. 7a is a signal in which each symbol is represented by any one of four amplitude values "W", "X", "Y", and" Z", similarly to the multi-level signal MS of FIG. 1a. Further, assume that |W - X| = | X - Y| = | Y - Z| = ΔV. Also in the multi-level signal MS of FIG. 7a, one or more specific amplitude values may be concentrated during a certain time interval. In FIG. 7a, the amplitude values "X" and "Y" are excessively distributed in the multi-level signal MS during a time interval T8, while not excessively distributed during time intervals T7 and T9.
To the first amplifier 121, the control signal CS is transmitted from the control signal generator 16. In the second embodiment, the control signal CS is composed of parallel 2 bits. The control signal CS has, as shown in FIG. 8, four patterns. A first control signal CS1 indicates that its 2 bits both represent "Hi" and that the amplitude values "X" and "Y" are excessively distributed in the multi-level signal MS that the discriminator D2 currently received. A second control signal CS2 indicates that its 2 bits represent both "Lo" and that the amplitude values "X" and "Y" are not excessively distributed therein. A third control signal CS3 indicates that the bit on one line of the bus represents "Hi" and the bit on the other represents "Lo", and that the amplitude value "X" is excessively distributed therein. A fourth control signal CS4 indicates that the bit on one line of the bus represents "Lo" and the bit on the other represents "Hi", and that the amplitude value "Y" is excessively distributed therein.
An amplification factor (gain) A121 of the first amplifier 121 is set differently according to the first to fourth control signals CS1 to CS4- The amplification factor A121 is also determined according to the format of the multi-level signal MS and/or the specifications of the discriminator D2. Described below is an example of the amplification factor A121.
When the first amplifier 121 receives the first or third control signal CS1 or CS3' its amplification factor A121 is set to W/X relative to the base level of the multi-level signal MS (amplitude value "Z"). In the second embodiment, W/X is 1.5. On the other hand, when the first amplifier 121 receives the second or fourth control signal CS2 or CS4, its amplification factor A121 is set to 1.
Described next is one specific example of the operation of the first wave-shaping circuit 12 as structured above. With the multi-level signal MS of FIG. 7a inputted to the discriminator D2, the second control signal CS2 is sent to the first amplifier 121 during the time intervals T7 and T9. The amplification factor A121 is thus set to 1 . As a result, the first amplifier 121 directly outputs the received multi-level signal MS to the first diode 131.
As such, the first wave-shaping circuit 12 shapes the waveform of the received multi-level signal MS. Consequently, since the amplitude of the received multi-level signal MS is amplified relative to the base level during the time interval T8, the waveform of an output signal OS12 becomes as such shown in FIG. 7b, with its peak value during the time interval T8 substantially equal in electric potential to the amplitude value "W".
Referring back to FIG. 6, the first detector 13 detects the first reference level RL1 from the signal outputted from the first wave-shaping circuit 12. For this detection, the first detector 13 preferably includes the first diode 131, a first capacitor 132, a first transistor 133, and a first current source 134. Since this circuit structure is similar to that of the detector 4 in FIG. 2, its description of operation is simplified herein.
In the first detector 13, a threshold Vth of the first diode 131 is selected to be substantially equal to the first reference level RL1 in electric potential. The first capacitor 132 is provided with a signal OS12 through the first diode 131, and charged until the input voltage Vi becomes equal to the output voltage Vo. As such, the first capacitor 132 detects the peak value of the output signal OS12, and outputs the peak value to one terminal of the resistor 61 as the first reference level RL1 as shown in FIG. 7c.
Referring back to FIG. 6, the second wave-shaping circuit 14 shapes the waveform of the multi-level signal MS from the first branching part 11 according to the control signal CS from the control signal generator 16 (refer to FIG. 8) so that the second detector 15 can correctly detect the second reference level RL2 (described later). For this purpose, the second wave-shaping circuit 14 exemplarily includes a second amplifier 141 . An input terminal of the second amplifier 141 is coupled to the first branching part 11, while an output terminal thereof is coupled to the cathode of a second diode 151 of the second detector 5. The second amplifier 141 is further coupled to the control signal generator 16 through a 2-bit bus.
When the second amplifier 141 receives the first or fourth control signal CS1 or CS4, the amplification factor A141 is set to Z/Y relative to the amplitude value "W" of the multi-level signal MS. In the second embodiment, Z/Y is 1.5. On the other hand, when the second amplifier 141 receives the second or third control signal CS2 or CS3, the amplification factor A141 is set to 1.
On the other hand, the first control signal CS1 is sent to the second amplifier 141 during the time interval T8. The amplification factor A141 is thus set to 1.5. Consequently, the second amplifier 141 amplifies the amplitude of the received multi-level signal MS by 1.5 times relative to the amplitude value "W", and outputs a signal OS14 to the cathode of second diode 151.
The second wave-shaping circuit 14 performs such wave-shaping as that the amplitude of the received multi-level signal MS is amplified by 1.5 times relative to the amplitude value "W" during the time interval T8. Consequently, the waveform of the output signal OS14 becomes as such shown in FIG. 7d, with its bottom value during the time interval T8 substantially equal in electric potential to the amplitude value "Z".
In the above structured second detector 15, a threshold Vth of the second diode 151 is selected to be substantially equal in electric potential to the second reference level RL2. The second capacitor 152 is provided with the output signal OS14 through the second diode 151, and charged until the input voltage V1 becomes equal to the output voltage Vo. As such, the second capacitor 152 detects the bottom value of the output signal OS14, and outputs the bottom value to one terminal of the resistor 64 as the second reference level RL2.
In the second embodiment, the cathode of the second diode 151 is provided with the signal OS14 having a waveform shown in FIG. 7d. The second reference level RL2 is, as shown in FIG. 9a, constant in time and equal in electric potential to the amplitude value "Z".
The function and structure of the threshold generator 6 and the comparing circuit 8 have been described in the first embodiment, and therefore their description is omitted herein. In the second embodiment, however, the threshold generator 6 is provided with the amplitude value "W" as the first reference level RL1 and the amplitude value "Z" as the second reference level RL2. Thus, three thresholds Th1, Th2, and Th3 to be generated therein are selected as Th1 = 5ΔV/2, Th2 = 3ΔV/2, and Th3 = ΔV/2.
The comparator 82 compares magnitudes between the amplitude of the received multi-level signal MS and the received threshold Th1, and outputs the result represented by "Hi" or "Lo". The comparator 83 compares magnitudes between the amplitude of the received multi-level signal MS and the threshold Th2, and outputs the result represented by "Hi" or "Lo". The comparator 84 compares magnitudes between the amplitude of the received multi-level signal MS and the threshold Th3, and outputs the result represented by "Hi" or "Lo" . The result of each of the comparators 82 to 84 indicates a discrimination result for each symbol of the multi-level signal MS. Through the output terminals 91 to 93 included in the output terminal group 9, these results are outputted to an external device.
These results are further sent to the control signal generator 16. Here, a comparison result {Hi, Hi, Hi} indicates that all comparators 82 to 84 output the results indicative of "Hi". A comparison result {Lo, Hi, Hi} indicates that only the comparators 83 and 84 output the results indicative of "Hi". A comparison result {Lo, Lo, Hi} indicates that only the comparator 84 outputs the result indicative of "Hi". A comparison result {Lo, Lo, Lo} indicates that all comparators 82 to 84 output the results indicative of "Lo".
When determining Nx > NREP1 and NY > NREF2, the control signal generator 16 assumes that the amplitude values "X" and "Y" are excessively distributed in the multi-level signal MS currently being received, and generates the first control signal CS1.
On the other hand, when determining Nx ≦ NREF1 and NY ≦ NREF2, the control signal generator 16 assumes that the amplitude values "X" and "Y" are not excessively distributed therein, and generates the second control signal CS2-
When determining Nx > NREF1 and Ny ≦ NREF2, the control signal generator 16 assumes that the amplitude value "X" is excessively distributed therein, and generates the third control signal CS3.
When determining Nx ≦ NREF1 and NY > NREF2, the control signal generator 16 assumes that the amplitude value "Y" is excessively distributed therein, and generates the fourth control signal CS4.
Described next is a discriminator D3 according to a third embodiment of the present invention. FIG. 10 shows a detailed circuit structure of the discriminator D3. The discriminator D3 has a similar structure to that of the discriminator D2 (refer to FIG. 6) . Therefore, components corresponding to those of FIG. 6 are provided with the same reference numerals in FIG. 10.
When the first amplifier 121 receives the first control signal CS1, the amplification factor A121 is set to W/X relative to the base level of the multi-level signal MS (the amplitude value "Z"). In the third embodiment, W/X is 1.5. On the other hand, when the first amplifier 121 receives the second or fourth control signal CS2 or CS4, the amplification factor A121 is set to 1.
During the time interval T8, the first control signal CS1 is sent to the first amplifier 121, thereby setting the amplification factor A121 to 1.5. Therefore, the first amplifier 121 amplifies the amplitude of the received multi-levels signal MS by 1.5 times relative to the base level. Consequently, since the amplitude of the multi-level signal MS is amplified by 1.5 times during the time interval T8, the waveform of the output signal OS12 becomes as such shown in FIG. 7b, with its peak value during the time interval T8 substantially equal in electric potential to the amplitude value "W".
When the second amplifier 141 receives the first control signal CS1, the amplification factor A141 is set to |W - Z | / |W - 3 · Y / 2| relative to the amplitude value "W" of the multi-level signal MS. In the third embodiment, |W - Z| / |W - 3 · Y / 2| is 2. On the other hand, when the second amplifier 141 receives the second or third control signal CS2 or CS3, the amplification factor A141 is set to 1.
During the time interval T8, the first control signal CS1 is sent to the second amplifier 141, thereby setting the amplification factor A141 to 2. therefore, the second amplifier 141 amplifies the amplitude of the received signal twice relative to the amplitude value "W", and outputs the signal OS14 to the first and second diodes 131 and 151.
As such, the second wave-shaping circuit 14 shapes the waveform of the signal outputted from the first wave-shaping circuit 12. Consequently, since the amplitude of the received signal OS12 (refer to FIG. 7b) is amplified twice during the time interval T8 relative to the amplitude value "W", the waveform of the output signal OS14 becomes as such shown in FIG. 11, with its bottom value during the time interval T8 substantially equal in electric potential to the amplitude value "Z".
Provided with the signal OS14 of FIG. 11, the first and second detectors 13 and 15 can detect constant peak and bottom values, as similarly to the second embodiment. Therefore, as similar to the discriminator D1, the discriminator D3 can correctly discriminate the amplitude of even the multi-level signal MS in which one or more specific amplitude values are excessively distributed during a certain time interval (refer to FIG. 7a). This amplitude discrimination enables generation of the multi-level signal MS in the transmitting side with less restrictions than ever.
Note that the discriminators D2 and D3 do not include the component corresponding to the amplitude adjuster 7 of the discriminator D1. Even without such component, the threshold generator 6 can generate the thresholds Th1, Th2, and Th3 that allow correct amplitude discrimination without pulse-width distortion because the first and second reference levels RL1 and RL2 are selected to be the amplitude values "W" and "Z", respectively.
However, the amplitude adjuster 7 may be required also in the discriminators D2 and D3 depending on the values selected for the first and second reference levels RL1 and RL2. For example, in the discriminator D2, the amplitude adjuster 7 capable of dividing the voltage of an input signal into two-thirds is required to be placed between the first branching part 11 and the comparing circuit 8 when the amplitude values "X" and "Z" are selected for the first and second reference levels RL1 and RL2, respectively.
Still further, in the first to third embodiments, when a multi-level signal MS in which an unnecessary amplitude is excessively distributed is sent to the discriminators D1 to D3 immediately after startup, the detector comprising a diode (or resistor) and a capacitor cannot, in some cases, detect the first or second reference level RL1 or RL2 quickly. For example, when a multi-level signal MS in which the amplitude values "Y" and "Z" are excessively distributed is sent to the discriminator D1 of FIG. 2 immediately after startup, the detector 4 consumes much time in detecting the first reference level RL1 (amplitude value "X"), making it impossible for the threshold generator 6 to generate the thresholds Th1, Th2, and Th3 quickly and correctly.
Still further, prior to the multi-level signal MS, a training signal may be transmitted from the transmitting side to the discriminators D1 to D3 in a predetermined time interval for the above mentioned correct amplitude discrimination. Such training signal has a predetermined amplitude or pattern. For example, if a training signal having the amplitude value "X" is sent to the discriminator D1 at least during a time interval of charging the capacitor 42, the detector 4 can correctly detect the first reference level RL1 from the head of the multi-level signal MS.
A discriminator (D1) discriminating a multi-level signal varying in amplitude, comprising:
a first branching part (2) branching the multi-level signal externally inputted thereto into two;
a wave-shaping circuit (3) shaping a waveform of the multi-level signal branched by said first branching part;
a detector (4) detecting a first reference level based on an output signal from said wave-shaping circuit;
a reference level generator (5) generating a second reference level of the multi-level signal externally inputted;
a threshold generator (6) generating a required number of thresholds according to said first and second reference levels; and
a comparing circuit (8) comparing the amplitude of the multi-level signal branched by said first branching part with the thresholds generated by said threshold generator;
said discriminator characterized in further comprising
a control signal generator (10) generating a control signal indicative of a time interval in which one or more specific amplitude values of the multi-level signal are excessively distributed, according to a comparison result by said comparing circuit, and wherein
said wave-shaping circuit shaping the waveform of the multi-level signal inputted thereto according to the control signal outputted from said control signal generator so that said detector can correctly detect the first reference level, and
said multi-level signal varies in amplitude among three or more values.
A discriminator according to claim 1, wherein
said threshold generator generates the number of amplitude values - 1 different thresholds according to the first and second reference levels, said comparing circuit comprises:
a second branching part (81) branching the multi-level signal inputted thereto into the number of amplitude values - 1; and
the number of amplitude values - 1 comparators (82, 83, 84) each receiving different one of the thresholds generated by said threshold generator and the multi-level signal branched by said second branching part, and each of said comparators compares the amplitude of the received multi-level signal with the received threshold.
The discriminator according to claim 1, wherein
said reference level generator generates the second reference level having an electric potential while the multi-level signal having a base level is sent.
said control signal defines a time interval during which one or more predetermined amplitude values are excessively distributed in the multi-level signal, and
said wave-shaping circuit shapes the waveform of the multi-level signal inputted thereto so that one of the predetermined amplitude values becomes equal to the second reference level during the time interval defined by the control signal.
A discriminator (D2) discriminating a multi-level signal varying in amplitude, comprising:
a first branching part (11) branching the multi-level signal externally inputted thereto into the three and outputting first to third multi-level signals;
a first wave-shaping circuit (12) shaping a waveform of the first multi-level signal outputted from said first branching part;
a first detector (13) detecting a first reference level based on an output signal from said wave-shaping circuit;
a second wave-shaping circuit (14) shaping a waveform of the second multi-level signal outputted from said first branching part:
a second detector (15) detecting a second reference level from a signal outputted from said second wave-shaping circuit;
a threshold generator (6) generating a required number of thresholds according to said first and second reference levels;
a comparing circuit (8) comparing the amplitude of the third multi-level signal outputted by said first branching part with the thresholds generated by said threshold generator;
said discriminator characterized in further comprising a control signal generator (16) generating a control signal indicative of a time interval in which one or more specific amplitude values of the multi-level signal are excessively distributed, according to a comparison result by said comparing circuit, and wherein
said wave-shaping circuit shaping the waveform of the first multi-level signal inputted thereto according to the control signal outputted from said control signal generator so that said detector can correctly detect the first reference level,
said second wave-shaping circuit shaping the waveform of the second multi-level signal inputted thereto according to the control signal outputted from said control signal generator so that said second detector can correctly detect the second reference level, and
The discriminator according to claim 5, wherein
said threshold generator generates the number of amplitude values - 1 different thresholds according to the first and second reference levels,
a second branching part (81) branching the third multi-level signal inputted thereto into the number of amplitude values - 1; and
the number of amplitude values - 1 comparators (82, 83, 84) each receiving different one of the thresholds generated by said threshold generator and the third multi-level signal branched by said second branching part,
each of said comparators compares the amplitude of the received third multi-level signal with the received threshold.
said first and second wave-shaping circuits shape the waveforms of the first and second multi-level signals inputted thereto so that one of the predetermined amplitude values becomes equal to said first and second reference levels, respectively, during the time interval defined by the control signal.
A discriminator (D3) discriminating a multi-level signal varying in amplitude, comprising:
a first branching part (11) branching the multi-level signal externally inputted into two;
a second wave-shaping circuit (14) shaping a waveform of an output signal from said first wave-shaping circuit;
a first detector (13) detecting a first reference level based on an output signal from said second wave-shaping circuit;
a second detector (15) detecting a second reference level based on the output signal from said second wave-shaping circuit;
a comparing circuit (8) comparing the amplitude of the third multi-level signal branched by said first branching part with the thresholds generated by said threshold generator;
said first wave-shaping circuit shaping the waveform of the multi-level signal inputted thereto according to the control signal outputted from said control signal generator so that said first detector can correctly detect the first reference level,
said second wave-shaping circuit shaping the waveform of the output signal from said first wave-shaping circuit according to the control signal outputted from said control signal generator so that said second detector can correctly detect the second reference level, and
The discriminator according to claim 8, wherein
said threshold generator generated the number of amplitude values - 1 different thresholds according to the first and second reference levels,
each of said comparators compares the amplitude of the received multi-level signal with the received threshold.
said first and second wave-shaping circuits shape the waveforms of the respective received signal so that one of the predetermined amplitude values becomes equal to the first and second reference levels, respectively, during the time interval defined by the control signal.
EP20000105384 1999-03-26 2000-03-21 Multi-level signal discriminator Expired - Fee Related EP1039644B1 (en)
JP8331199 1999-03-26
EP1039644A2 EP1039644A2 (en) 2000-09-27
EP1039644A3 EP1039644A3 (en) 2004-04-07
EP1039644B1 true EP1039644B1 (en) 2006-01-04
ID=13798883
EP20000105384 Expired - Fee Related EP1039644B1 (en) 1999-03-26 2000-03-21 Multi-level signal discriminator
US (1) US6271690B1 (en)
EP (1) EP1039644B1 (en)
DE (1) DE60025290T2 (en)
TW (1) TW445718B (en)
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2000-03-21 EP EP20000105384 patent/EP1039644B1/en not_active Expired - Fee Related
2000-03-21 TW TW89105104A patent/TW445718B/en not_active IP Right Cessation
2000-03-21 DE DE2000625290 patent/DE60025290T2/en not_active Expired - Fee Related
2000-03-24 US US09/534,873 patent/US6271690B1/en active Active
DE60025290D1 (en) 2006-03-30
DE60025290T2 (en) 2006-08-31
EP1039644A2 (en) 2000-09-27
KR20010006857A (en) 2001-01-26
US6271690B1 (en) 2001-08-07
TW445718B (en) 2001-07-11
EP1039644A3 (en) 2004-04-07
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EP0844736B1 (en) 2002-06-12 Waveform-Shaping circuit and a data-transmitting apparatus using such a circuit
WO2002005474A1 (en) 2002-01-17 Data communications method
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