JP6923331B2 - BMC demodulator and threshold generation method for BMC demodulation - Google Patents

Description

The present invention relates to a demodulation technique of BMC (Biphase Mark Code).

As a digital data encoding method, a BMC (Biphase Mark Code) method is known. BMC is a type of Manchester code, and has been adopted in the transmission of audio signals in the past, and in recent years in the Qi standard for wireless power supply and the USB (Universal Serial Bus) PD (Power Delivery) standard.

FIG. 1 is a waveform diagram of a BMC-encoded signal (hereinafter referred to as a BMC signal). In the BMC signal, a transition always occurs at the boundary of the symbol. Assuming that the period of the symbol is T ₀ , when the value of the symbol is 1, the symbol period T ₀ includes two edges, and therefore the distance between the edges is T _0/2 . When the value of the symbol is 0, _{one edge is included in the symbol period T 0} , and therefore the distance between the edges is T ₀ . The high level and low level of the BMC signal are switched according to the initial state.

The demodulator that demodulates the BMC signal determines the symbol by measuring the distance between the edges in each symbol period. The judges determined that symbol 1 when the distance between the edges is T _0/2, and the symbol 0 when the distance between the edges is T _0. Specifically, a threshold value for distinguishing the two symbols can be set, and the value of the symbol can be determined based on the comparison result between the measured edge-to-edge distance and the threshold value. The threshold value in the present specification is a general term for an upper threshold value for determining symbol 0 and a lower threshold value for determining symbol 1.

In the demodulation of the BMC signal, _{the fluctuation of the symbol period T SYM} (symbol frequency f _SYM ) becomes a problem. If the threshold value is kept constant when the fluctuation range of the symbol period T _{0 is large, the symbol value is erroneously determined.} Therefore, in an _{application in which the symbol period T SYM} fluctuates greatly, a preamble whose symbol value is known is arranged, and an optimum threshold value is set by using the preamble.

FIG. 2 is a diagram illustrating a method of setting a threshold value using a preamble. FIG. 2 is a histogram in which the horizontal axis represents the count value of the distance between edges and the vertical axis represents the frequency of occurrence of each count value during the preamble period. The histogram is divided into a count group of symbol 1 and a count group of symbol 0. The threshold value may be set near the center of the two count groups. For example, the count value PEAK ₁ occurrence frequency count group G ₁ symbol 1 reaches a peak, the count value PEAK ₀ occurrence frequency count group G ₀ symbols 0 reaches a peak, the calculated and the average of these It can be a threshold value.

Japanese Unexamined Patent Publication No. 2016-158025

In the threshold value setting method using the above-mentioned histogram, it is necessary to detect the peak of the occurrence frequency, and the amount of arithmetic processing increases, so that the circuit scale of the demodulator becomes large and a high-speed clock is required.

The present invention has been made in view of these problems, and one of the exemplary purposes of the embodiment is to generate a BMC signal demodulator and a threshold value that can set an appropriate threshold value by a method different from the conventional method. It is in the provision of methods.

One aspect of the present invention relates to a method of generating a threshold value for demodulation processing of a BMC signal modulated by a BMC (Biphase Mark Code) method. This generation method includes the following processing.
(Process 1) Receive a preamble containing symbols 1 and 0 alternately.
(Process 2) The edge-to-edge distance is measured over a plurality of symbol periods included in the preamble.
(Processing 3) A threshold value is generated based on a value obtained by adding and averaging the inter-edge distance corresponding to symbol 1 and the inter-edge distance corresponding to symbol 0 with a weighting of 1: 2.
According to this method, complicated processing such as peak search is not required, so that the optimum threshold value can be determined with simple hardware.

The process 3 for generating the threshold value may include the following process.
(Process 3-1) The measured value of the distance between edges over 2 × n symbol periods is held.
(Process 3-2) 3 × i-2 th (i = 1, ... n) by adding the first measurement value group including measurements of distance between the edges of, for generating a first sum value _{S 1.}
(Process 3-3) 3 × i-1 th (i = 1, ... n) by adding the second measurement value group including measurements of distance between the edges of, for generating a second sum value _{S 2.}
(Process 3-4) 3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of, generating a third adding value _{S 3.}
(Process 3-5) first addition value _{S 1,} the second addition value _{S 2,} the first intermediate value _{M 1} corresponding to the third adding value _{S 3,} the second intermediate value _{M 2,} a third intermediate value _{M 3} compare.
(Process 3-6) The measured value group corresponding to the maximum intermediate value is associated with symbol 0, and the two measured value groups corresponding to the remaining two intermediate values are associated with symbol 1.
According to this aspect, an appropriate one can be selected from the following three patterns.
Pattern 1 Symbol 0 = 1st measured value group Symbol 1 = 2nd measured value group, 3rd measured value group Pattern 1 Symbol 0 = 2nd measured value group Symbol 1 = 3rd measured value group, 1st measured value group Pattern 1 Symbol 0 = 3rd measured value group Symbol 1 = 1st measured value group, 2nd measured value group

The intermediate values M _{1 to} M ₃ may be 1 / n times the corresponding added values S _{1 to} S _{3, respectively.}

When the average value of the measured value group corresponding to symbol 0 is A _SYM0 and the average value of the two measured value groups corresponding to symbol 1 is A _SYM11 and A _SYM12 , the threshold value is
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
You may respond to.

Each intermediate value M _{1 to} M ₃ may be the corresponding added value S _{1 to} S ₃ itself.

When the added value corresponding to symbol 0 is S _SYM0 and the two added values corresponding to symbol 1 are S _SYM11 and S _SYM12 , the threshold value is
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
You may respond to.

Another aspect of the present invention relates to a demodulator of a BMC signal modulated by a BMC (Biphase Mark Code) method. The demodulator measures the edge-to-edge distance over a plurality of symbol periods during the preamble period in which symbols 1 and 0 are alternately included, and the edge-to-edge distance corresponding to symbol 1 and the edge-to-edge distance corresponding to symbol 0. , A threshold value determining unit that generates a threshold value based on a value obtained by adding and averaging with a weighting of 1: 2.

The threshold determination unit is a register that holds the measured values of n × 3 edge-to-edge distances measured over 2 × n symbol periods, and the 3 × i-2nd (i = 1,… n). of adding the first measurement value group including measurements of the distance between the edges, a first adder for generating a first sum value S _1, 3 × i-1 th (i = 1, ... n) edge adding the second measurement value group including measurements between the distance, and a second adder for generating a second sum value S _2, the distance between the edges of the 3 × i-th (i = 1, ... n- 1) To the third adder that adds the third measurement value group including the measurement values of _{and generates the third addition value S 3} , and the first addition value S ₁ , the second addition value S ₂ , and the third addition value S ₃ . A maximum value selection circuit that compares the corresponding first intermediate value M ₁ , the second intermediate value M ₂ , and the third intermediate value M ₃ and detects the maximum intermediate value may be included.

The threshold value determination unit may associate the measured value group corresponding to the maximum intermediate value with symbol 0 and the two measured value groups corresponding to the remaining two intermediate values with symbol 1.

Threshold value determination unit, when the average value of the measurement value group corresponding to the symbol 0 is _{A SYM0,} the average value of two measurements group corresponding to the symbol 1 is _{A SYM11, A SYM12,}
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
You may generate a threshold value according to.

When the threshold value determination section, the additional value corresponding to the symbol 0 is _{S SYM0,} two additional values corresponding to the symbol 1 is _{S SYM11, S SYM12,}
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
You may generate a threshold value according to.

It should be noted that an arbitrary combination of the above components or a conversion of the expression of the present invention between methods, devices and the like is also effective as an aspect of the present invention. Furthermore, the description of this item (means for solving the problem) does not explain all the essential features of the present invention, and therefore subcombinations of these features described may also be the present invention. ..

According to the present invention, an appropriate threshold value can be set by a method different from the conventional method.

It is a waveform diagram of a BMC signal. It is a figure explaining the setting method of the threshold value using a preamble. It is a flowchart which shows the generation method of the threshold value for demodulation processing of a BMC signal. 4 (a) and 4 (b) are diagrams for explaining the generation of the threshold value based on the flowchart of FIG. It is a figure which shows the relationship between the timing which starts the measurement of the edge-to-edge distance in a preamble period, and the measured edge-to-edge distance. It is a flowchart of the process of determining the correspondence relationship between the measured edge-to-edge distance and symbols 1, 0. It is a block diagram of a demodulator. It is a circuit diagram of the demodulator which concerns on 1st Example. It is a circuit diagram of the demodulator which concerns on 2nd Example. It is a circuit diagram of the demodulator which concerns on 3rd Example.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the embodiment is not limited to the invention but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

In the present specification, the "state in which the member A is connected to the member B" means that the member A and the member B are physically directly connected, or the member A and the member B are electrically connected to each other. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state or does not impair the functions and effects performed by the combination thereof.
Similarly, "a state in which the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and their electricity. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state, or does not impair the functions and effects produced by the combination thereof.

FIG. 3 is a flowchart showing a method of generating a threshold value for demodulation processing of a BMC signal. The flowchart referred to in the present specification does not limit the order of each process, and the plurality of processes can be appropriately replaced as long as there is no problem.

A preamble containing the symbols 1 and 0 alternately is received (S100). Such a preamble is perfectly DC balanced. Then, the edge-to-edge distance (time length) D is measured over a plurality of 2 × n (n ≧ 2) symbol periods T _{SYM1 to} T _{SYM2n included in the preamble (S102).} And an edge distance D ₀ corresponding to the distance between the edges D ₁ and symbol 0 corresponding to the symbol 1, 1: Based on the value obtained by averaging with 2 weighting, to generate a threshold value S _TH (S104).

4 (a) and 4 (b) are diagrams for explaining the generation of the threshold value based on the flowchart of FIG. It is a waveform figure which shows the generation process of the threshold value _STH. S _RX represents a receiving signal in the preamble period. During the 2 × n symbol period, the edge-to-edge distance D ₁ corresponding to the symbol 1 is included by 2 × n, and the edge-to-edge distance D ₀ corresponding to the symbol 0 is included by n.

The average value D _1AVE of the 2 × n edge-to-edge distances D ₁ is represented by the equation (1a), and the average value D _{0 AVE} of the n edge-to-edge distances D 0 is represented by the equation (1b).
D _1AVE = ΣD ₁ / (2n) ... (1a)
D _0AVE = ΣD ₀ / n ... (1b)
In this embodiment, the threshold value _{S TH} to be obtained, defined according to the average value _{D AVE} of the average value _{D 0AVE} average value _{D 1AVE} edge distance _{D 0} of the distance between the edges _{D 1.} Note that, although it is assumed equal to the average value D _AVE threshold S _TH for the sake of brevity is not limited thereto as described later.
S _TH ≒ D _AVE = (D ₁ AVE + D ₀ AVE) / 2 ... (2)

By substituting the equations (1a) and (1b) into the equation (2), the equation (3) is obtained.
S _TH = {ΣD ₁ / (2n) + ΣD ₀ / n} / 2
= (ΣD ₁ + 2 _{ΣD 0} ) / n ... (3)

Equation (3), the threshold S _TH is a distance between the edges D ₀ corresponding to the distance between the edges D ₁ and symbol 0 corresponding to the symbol 1 1: a value obtained by averaging with 2 weighting Indicates that you are responding.

FIG. 4B is a histogram of the measured edge-to-edge distances. The mountain on the left represents the distribution of the edge-to-edge distance D ₁ corresponding to symbol 1, and the mountain on the right represents the distribution of the edge-to-edge distance D ₀ corresponding to symbol 0. Threshold _{S TH,} the average value _{D 1AVE} the left angle, is set near the center of the average value _{D 0AVE} the right of the mountain.

The above is the method of generating the _{threshold value STH according to the embodiment. According to this method, an appropriate threshold value STH} can be generated by a 1: 2 weighted addition averaging process without requiring a complicated process such as a peak search. The simplicity of the process contributes to the simplification of the hardware to achieve it, as described below.

Generally demodulator does not know the timing of the received signal S _RX including a preamble is input, unpredictable leading preamble in other words. Therefore, the correspondence between the plurality of measured edge-to-edge distances and the symbols 1 and 0 changes according to the timing at which the measurement of the edge-to-edge distances is started. FIG. 5 is a diagram showing the relationship between the timing at which the measurement of the edge-to-edge distance is started during the preamble period and the measured edge-to-edge distance.

Let the distances between edges measured in order from the start timing be a, b, c, a, b, c ... When measured started at the timing (i), the distance between the edges D ₀ edge distance D ₁ becomes, b corresponds to the symbol 0 and a and c correspond to the symbol 1. When measured started at the timing (ii), b, c is the distance between the edges D ₀ edge distance D ₁ becomes, a corresponding symbol 0 corresponding to the symbol 1. When measured started at the timing (iii), a, b is the distance between the edges D ₀ edge distance D ₁ becomes, c corresponds to the symbol 0 corresponding to the symbol 1.

Here, a process of determining whether the measured edge-to-edge distance corresponds to symbol 1 or symbol 0 will be described.

FIG. 6 is a flowchart of a process for determining the correspondence between the measured edge-to-edge distance and the symbols 1 and 0. Holds measurements of inter-edge distances over 2 × n symbol periods T _{SYM (S200).} 3 × i-2 th (i = 1, ... n) the first measurement value group including measurements of distance between the edges of adding (a in FIG. 5), to produce a first sum value _{S 1} (S202 ). Similarly, 3 × i-1 th (i = 1, ... n) by adding the second measurement value group including measurements of distance between the edges of the (b in FIG. 5), generate a second sum value S ₂ (S204), the third measured value group (c in FIG. 5) including the measured values of the 3 × i th (i = 1, ... n-1) inter-edge distances is added, and the third added value S ₃ Is generated (S206).

The first addition value _{S 1,} the second addition value _{S 2,} the first intermediate value _{M 1} corresponding to the third adding value _{S 3,} the second intermediate value _{M 2,} comparing the third intermediate value _{M 3} (S208). Then, the measured value group corresponding to the maximum intermediate value is associated with the symbol 0, and the two measured value groups corresponding to the remaining two intermediate values are associated with the symbol 1 (S210).

For example, the intermediate values M _{1 to} M ₃ may be 1 / n times the corresponding added values S _{1 to} S _{3, respectively.} Alternatively, the intermediate values M _{1 to} M ₃ may be the corresponding added values S _{1 to} S ₃ themselves, respectively.

According to this process, it is possible to determine which symbol the measured value group corresponds to. Further, since the operations in the processes S202, S204, and S206 are common to the addition averaging process S104 in FIG. 2, the added value or the intermediate value generated in the processes S202, S204, and S206 is used in the process S104 in FIG. Therefore, the calculation cost can be reduced.

Subsequently, a specific calculation method of the threshold value _{STH will be described.}
(First calculation method)
Measurement value group average value _{A SYM0} corresponding to the symbol 0, when the average value of two measurements group corresponding to the symbol 1 is _{A SYM11, A SYM12,} the threshold _{S TH,} the
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
Can be obtained according to. Since division by 2 or 4 can be realized by bit shift, the calculation cost can be low.

(Second calculation method)
Addition value _{S SYM0} corresponding to the symbol 0, when two addition values corresponding to the symbol 1 is _{S SYM11, S SYM12,} the threshold _{S TH,} the
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
Can be obtained according to.

FIG. 7 is a block diagram of the demodulator 100. The demodulator 100 includes a counter 102 and a threshold value determination unit 110. In FIG. 7 and the following figures, _{only the blocks related to the determination of the threshold value STH} are shown in the demodulator 100, and the blocks related to reception in the data period following the preamble period are omitted.

The counter 102 measures the edge-to-edge distance D over _{a plurality of 2 × n symbol periods T SYM} during a preamble period in which symbols 1 and 0 are alternately included. The threshold value determination unit 110 is based on a value obtained by adding and averaging the _{inter-edge distance D 1} corresponding to symbol 1 and the inter-edge distance D _{0 corresponding to symbol 0 with a weighting of 1: 2.} Generate a threshold value _STH.

The present invention extends to various methods, devices, and circuits grasped as the flowchart of FIG. 3 or the block diagram of FIG. 7 or derived from the above description, and is not limited to a specific configuration. Hereinafter, more specific examples and modifications will be described not for narrowing the scope of the present invention but for helping to understand the essence of the invention and circuit operation and clarifying them.

(First Example)
FIG. 8 is a circuit diagram of the demodulator 100A according to the first embodiment. The threshold value determination unit 110A includes a register 112, a first adder 121 to a third adder 123, a maximum value selection circuit 130, a first arithmetic unit 131 to a sixth arithmetic unit 136, and an output circuit 150A.

The register 112 holds the measured values of the n × 3 edge-to-edge distances D measured over 2 × n symbol periods T _{SYM1 to} T _SYM2n. A shift register can be used as the register 112. It is desirable that n = 2 ^m (m is a natural number). For example, m = 2 and n = 4.

Of the measurement values held in the register 112, referred 3 × i-2 th (i = 1, ... n) measured values _a 1 ~a _n edge distance between the first measurement value group, 3 × i -1st (i = 1, ... n) edge-to-edge distance measurement values b _{1 to} b _n are referred to as the second measurement value group, and the 3xith (i = 1, ... n-1) edge. the measured value _c 1 to c _n between distance is referred to as a third measurement value group. First adder 121, first adding the measured value group _a 1 ~a _n, to produce a first sum value _{S 1.} The second adder 122 adds the second measured value groups b _{1 to} b _n to generate the second added value S _2. The third adder 123, a third adds the measured value group _c 1 to c _n, to generate a third sum value _{S 3.}

The first arithmetic unit 131 multiplies the first addition value S ₁ by 1 / n to generate the first average value A _1. The second arithmetic unit 132 multiplies the second addition value S ₂ by 1 / n to generate the second average value A _2. The third arithmetic unit 133 multiplies the third addition value S ₃ by 1 / n to generate the third average value A _3. When n = 2 ^m , each of the first arithmetic unit 131 to the third arithmetic unit 133 can be configured by a bit shifter that shifts the input data downward by m bits.

The maximum value selection circuit 130, first addition value _{S 1,} the second addition value _{S 2,} the first intermediate value corresponding to the third adding value _{S 3 M 1,} the second intermediate value _{M 2,} third intermediate value _{M 3} Are compared, and the maximum intermediate value _MMAX is detected and output. In FIG. 8, the first intermediate value M ₁ , the second intermediate value M ₂ , and the third intermediate value M ₃ are the first average value A ₁ , the second average value A ₂ , and the third average value A ₃ , respectively.

Maximum result of the comparison of the selection circuit 130, the measurement value group corresponding to the maximum intermediate value M _MAX is associated with the symbol 0, associating two measurements group corresponding to the remaining two intermediate values in the symbol 1 Be done.

The fourth arithmetic unit 134 generates a _{fourth average value A 4} which is 1 / n times the average value of _{the first addition value S 1} and the second addition value S _2. The fifth arithmetic unit 135 generates a _{fifth average value A 5} which is 1 / n times the average value of _{the second addition value S 2} and the third addition value S _3. The sixth arithmetic unit 136 generates _{the sixth average value A 6} which is 1 / n times the average value of _{the third addition value S 3} and the first addition value S _1. The fourth arithmetic unit 134 to the sixth arithmetic unit 136 may include an adder 170 and an arithmetic unit 172, respectively. The adder 170 adds two inputs. The arithmetic unit 172 multiplies the output of the adder 170 by 1 / (2n). When n = 2 ^m , the arithmetic unit 172 can be composed of a bit shifter that shifts the input data downward by m + 1 bits.

This output circuit 150A generates _{(i) a threshold value STH} corresponding to the average value of the first average value A ₁ and the fifth average value A ₅ when the first average value A _{1 is the maximum.} ii) When the second average value A _{2 is the maximum, a threshold value STH} corresponding to the average value of the second average value A ₂ and the sixth average value A ₆ is generated (iii) the third average value A ₃ When is the maximum, _{the threshold value STH} corresponding to the average value of _{the third average value A 3} and the fourth average value A ₄ is generated.

For example, the output circuit 150A includes a selector 152, an output averaging circuit 154 and adders 156 and 158. The selector 152 receives the fourth average value A ₄ , the fifth average value A ₅ , and the sixth average value A ₆ . A selection signal SEL indicating the detection result of the maximum value selection circuit 130 is input to the selector 152. The selector 152 selects (i) the fifth average value A _{5 when the first average value A 1} is the maximum, and (ii) the sixth average value A ₆ when the second average value A _{2 is the maximum.} Is selected, and (iii) when the third average value A ₃ is the maximum, the fourth average value A ₄ is selected. The output averaging circuit 154 calculates the average value _{of the output MMAX} of the maximum value selection circuit 130 and the output _ASEL of the selector 152. The output of the output averaging circuit 154 corresponds to the _{provisional threshold STH.}

The adder 156 _{subtracts 1 from the provisional threshold S TH} to generate _{the threshold S TH} 1 for determining symbol 1. The adder 158 adds 1 to the provisional threshold _{S TH,} to generate a threshold _{S TH0} for determining the symbol 0. In the data section, the distance between the measured edge, is shorter than the threshold S _TH1, determines that the symbol 1, the distance between the edges is measured, when longer than the threshold value S _TH0, is possible to determine that the symbol 0 can.

Output _{M MAX} from the maximum value selection circuit 130, represents the average value _{A SYM0} measurement value group corresponding to the symbol 0. _Further , when the average value of the two measured value groups corresponding to the symbol 1 is A _SYM11 and A SYM12, the output of the selector 152 represents the average value of _{A SYM11} and A _{SYM12. Therefore, the provisional threshold STH} , which is the output of the output averaging circuit 154, is
{A _SYM0 + (A _SYM11 + A _SYM12 ) / 2} / 2
= A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
Represents. That is, it is understood that the demodulator 100A of FIG. 8 generates a threshold value based on the above-mentioned first calculation method.

(Second Example)
FIG. 9 is a circuit diagram of the demodulator 100B according to the second embodiment. The threshold value determination unit 110B includes the seventh arithmetic unit 137 to the ninth arithmetic unit 139 in place of the fourth arithmetic unit 134 to the sixth arithmetic unit 136 of the threshold value determination unit 110A in FIG.

The seventh arithmetic unit 137 generates the seventh average value A _{7 representing the average value of the first average value A 1} and the second average value A _2. The eighth arithmetic unit 138 generates an _{eighth average value A 8} representing the average value of _{the second average value A 2} and the third average value A _3. The ninth arithmetic unit 139 generates the ninth average value A _{9 representing the average value of the third average value A 3} and the first average value A _1. The seventh arithmetic unit 137 to the ninth arithmetic unit 139 can be configured in the same manner as the fourth arithmetic unit 134 to the sixth arithmetic unit 136.

The output circuit 150B receives the seventh average value A ₇ , the eighth average value A ₈ , and the ninth average value A _{9 , and (i) the first average value A 1} is set according to the detection result of the maximum value selection circuit 130. when the maximum, the first average value _{a 1} and generates a threshold _{S TH1, S TH0} corresponding to the average value of the 8 averages _{a 8,} (ii) when the second average value _{a 2} is a maximum second when the average value _{a 2} and 9 to generate a threshold _{S TH1, S TH0} corresponding to the average value of the average value _{a 9} (iii) third average value _{a 3} is the maximum, the third average value A ₃ and the 7th average value The _{threshold values S TH1} and S _{TH 0} corresponding to the average value of _{A 7} are generated. The configuration of the output circuit 150B is the same as that of the output circuit 150A of FIG.

_{Even in this demodulator 100B, the provisional threshold value STH} , which is the output of the output averaging circuit 154, is
{A _SYM0 + (A _SYM11 + A _SYM12 ) / 2} / 2
= A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
Represents. That is, it is understood that the demodulator 100B of FIG. 9 generates a threshold value based on the above-mentioned first calculation method.

(Third Example)
FIG. 10 is a circuit diagram of the demodulator 100C according to the third embodiment. In the threshold value determination unit 110C, the maximum value selection circuit 130C receives the first addition value S ₁ to the third addition value S ₃ as _{the first intermediate value M 1} to the third intermediate value M _3.

The tenth arithmetic unit 140 generates a _{tenth addition value S 10} representing an addition value of _{the first addition value S 1} and the second addition value S _2. The eleventh arithmetic unit 141 generates the eleventh addition value S _{11 representing the addition value of the second addition value S 2} and the third addition value S _3. The twelfth arithmetic unit 142 generates the twelfth addition value S _{12 representing the addition value of the third addition value S 3} and the first addition value S _1.

The output circuit 150C is 10 addition value _{S 10,} 11th addition value _{S 11,} receives a twelfth summation value _{S 12,} in response to the selection signal SEL indicating the detection result of the maximum value selection circuit 130C, (i) first When the added value S ₁ is the maximum, _{the threshold values S TH1} and S _{TH0 corresponding to S 1} / (2 × n) + S ₁₁ / (4 × n) are generated, and (ii) the second added value S ₂ When is the maximum, _{the thresholds S TH1} and S _{TH0 corresponding to S 2} / (2 × n) + S ₁₂ / (4 × n) are generated, and (iii) the third addition value S ₃ is the maximum. Then, _{the threshold values S TH1} and S _{TH 0 corresponding to S 3} / (2 × n) + S ₁₀ / (4 × n) are generated.

The selector 160 receives the 10th addition value S ₁₀ , the 11th addition value S ₁₁ , and the 12th addition value S ₁₂ , and selects one according to the selection signal SEL. The arithmetic unit 162 doubles the output of the maximum value selection circuit 130C. The adder 164 adds the output of the arithmetic unit 162 and the output of the selector 160. The arithmetic unit 166 multiplies the output of the output averaging circuit 154 by 1 / (4n). The arithmetic unit 162 and the arithmetic unit 166 can be configured by a bit shifter. The output of the calculator 166 represents the _{provisional threshold STH.}

The output of the maximum value selection circuit 130C represents the _{added value S SYM0 corresponding to symbol 0.} The output of the selector 160 is _{S SYM11} + S _SYM12, which is the sum of the _{two added values S SYM11} and S _{SYM12 corresponding to the symbol 1. Therefore, the provisional threshold value STH} , which is the output of the arithmetic unit 166, is
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
Represents. That is, it is understood that the demodulator 100C of FIG. 10 generates a threshold value based on the above-mentioned second calculation method.

The present invention has been described above based on the embodiments. This embodiment is an example, and it is understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. be. Hereinafter, such a modification will be described.

The first to third examples are merely examples, and many other modifications may exist. For example, the bit shift (2 times, 4 times ... or 1/2 times, 1/4 times ...) processing may be performed at any position as long as the same calculation result can be obtained.

100 ... demodulator, 102 ... counter, 110 ... threshold value determination unit, 112 ... register, 121 ... first adder, 122 ... second adder, 123 ... third adder, 130 ... maximum value selection circuit, 131 ... 1st adder, 132 ... 2nd adder, 133 ... 3rd adder, 134 ... 4th adder, 135 ... 5th adder, 136 ... 6th adder, 137 ... 7th adder, 138 ... 8th adder, 139 ... 9th adder, 140 ... 10th adder, 141 ... 11th adder, 142 ... 12th adder, 150 ... output circuit, 152 ... selector, 154 ... output average circuit, 156, 158 ... adder, 160 ... selector, 162 ... calculator, 164 ... adder, 166 ... calculator.

Claims (6)

It is a method of generating a threshold value for demodulation processing of a BMC signal modulated by the BMC (Biphase Mark Code) method.
A step of receiving a preamble containing alternating symbols 1 and 0,
A step of measuring the edge-to-edge distance over a plurality of symbol periods included in the preamble,
A step of generating the threshold value based on a value obtained by adding and averaging the inter-edge distance corresponding to symbol 1 and the inter-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The step of generating the threshold is
A step of holding measurements of edge-to-edge distances over 2 x n symbol periods,
3 × i-2 th (i = 1, ... n) comprising the steps of adding the first measurement value group including measurements of distance between the edges of, for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) comprising the steps of adding the second measurement value group including measurements of distance between the edges of, for generating a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of the steps of generating a third adding value S _3,
A step of multiplying the first addition value S ₁ by 1 / n to generate a _{first average value A 1 and}
A step of multiplying the second addition value S ₂ by 1 / n to generate a _{second average value A 2 and}
A step of multiplying the third addition value S ₃ by 1 / n to generate a _{third average value A 3 and}
Among from the first average value A ₁ of the third average value A _3, and determining the largest one,
Generating a fourth average value A ₄ of 1 / n times the first adder values S ₁ and the second average value of the sum S _2,
Generating a fifth mean value A ₅ of 1 / n times the second addition value S ₂ and the average value of the third adding value S _3,
A step of generating a _{sixth average value A 6} which is 1 / n times the average value of the third addition value S ₃ and the first addition value S _1.
(I) When the first average value A ₁ is the maximum, the _{threshold value corresponding to the average value of the first average value A 1} and the fifth average value A ₅ is generated, and (ii) the first. 2 When the average value A ₂ is the maximum, the _{threshold value corresponding to the average value of the second average value A 2} and the sixth average value A ₆ is generated (iii), and the third average value A ₃ is when the maximum, and generating the threshold value corresponding to said third average value a ₃ mean value of the fourth average value a _4,
A generation method characterized by including. It is a method of generating a threshold value for demodulation processing of a BMC signal modulated by the BMC (Biphase Mark Code) method.
A step of receiving a preamble containing alternating symbols 1 and 0,
A step of measuring the edge-to-edge distance over a plurality of symbol periods included in the preamble,
A step of generating the threshold value based on a value obtained by adding and averaging the inter-edge distance corresponding to symbol 1 and the inter-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The step of generating the threshold is
A step of holding measurements of edge-to-edge distances over 2 x n symbol periods,
3 × i-2 th (i = 1, ... n) comprising the steps of adding the first measurement value group including measurements of distance between the edges of, for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) comprising the steps of adding the second measurement value group including measurements of distance between the edges of, for generating a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of the steps of generating a third adding value S _3,
A step of multiplying the first addition value S ₁ by 1 / n to generate a _{first average value A 1 and}
A step of multiplying the second addition value S ₂ by 1 / n to generate a _{second average value A 2 and}
A step of multiplying the third addition value S ₃ by 1 / n to generate a _{third average value A 3 and}
Among from the first average value A ₁ of the third average value A _3, and determining the largest one,
A step of generating a _{seventh average value A 7} representing the average value of the first average value A ₁ and the second average value A _{2;
A step of generating an eighth average value A 8} representing the average value of the second average value A ₂ and the third average value A ₃ , and a step of generating the eighth average value A 8.
A step of generating the ninth average value A ₉ representing the average value of the third average value A ₃ and the first average value A _{1 and}
(I) When the first average value A ₁ is the maximum, the _{threshold value corresponding to the average value of the first average value A 1} and the eighth average value A ₈ is generated, and (ii) the first. 2 When the average value A ₂ is the maximum, the _{threshold value corresponding to the average value of the second average value A 2} and the ninth average value A ₉ is generated (iii), and the third average value A ₃ is when the maximum, and generating the threshold value corresponding to said third average value a ₃ mean value of the seventh average value a _7,
A generation method characterized by including. It is a method of generating a threshold value for demodulation processing of a BMC signal modulated by the BMC (Biphase Mark Code) method.
A step of receiving a preamble containing alternating symbols 1 and 0,
A step of measuring the edge-to-edge distance over a plurality of symbol periods included in the preamble,
A step of generating the threshold value based on a value obtained by adding and averaging the inter-edge distance corresponding to symbol 1 and the inter-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The step of generating the threshold is
A step of holding measurements of edge-to-edge distances over 2 x n symbol periods,
3 × i-2 th (i = 1, ... n) comprising the steps of adding the first measurement value group including measurements of distance between the edges of, for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) comprising the steps of adding the second measurement value group including measurements of distance between the edges of, for generating a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of the steps of generating a third adding value S _3,
Among from the first adder values S ₁ of the third adding value S _3, and determining the largest one,
A step of generating a _{tenth addition value S 10} representing an addition value of the first addition value S ₁ and the second addition value S _{2, and a step of generating the tenth addition value S 10.}
A step of generating an _{eleventh addition value S 11} representing an addition value of the second addition value S ₂ and the third addition value S _{3, and a step of generating the eleventh addition value S 11.}
A step of generating a _{twelfth addition value S 12} representing an addition value of the third addition value S ₃ and the first addition value S _{1 and a step of generating the twelfth addition value S 12.}
(I) When the first addition value S ₁ is the maximum, the _{threshold value corresponding to S 1} / (2 × n) + S ₁₁ / (4 × n) is generated, and (ii) the second addition When the value S ₂ is the maximum, the _{threshold value corresponding to S 2} / (2 × n) + S ₁₂ / (4 × n) is generated, and (iii) the third addition value S ₃ is the maximum. When, the step of generating the threshold value according to _{S 3} / (2 × n) + S _{10 / (4 × n) and}
A generation method characterized by including. A demodulator for BMC signals modulated by the BMC (Biphase Mark Code) method.
A counter that measures the edge-to-edge distance over multiple symbol periods during a preamble period that alternates between symbols 1 and 0.
A threshold value determination unit that generates a threshold value based on a value obtained by adding and averaging the edge-to-edge distance corresponding to symbol 1 and the edge-to-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The threshold value determination unit
A register that holds n x 3 edge-to-edge distance measurements measured over 2 x n symbol periods, and
3 × i-2 th (i = 1, ... n) and adding the first measurement value group including measurements of distance between the edges of the first adder for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) and adding the second measurement value group including measurements of distance between the edges of the second adder to generate a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of a third adder for generating a third adding value S _3,
A first arithmetic unit that multiplies the first addition value S ₁ by 1 / n and outputs the first average value A _{1 and}
A second arithmetic unit that multiplies the second addition value S ₂ by 1 / n and outputs the second average value A _2.
A third arithmetic unit that multiplies the third addition value S ₃ by 1 / n and outputs the third average value A _{3 and}
A maximum value selection circuit that detects the largest of the first average value A ₁ , the second average value A ₂ , and the third average value A _3.
A fourth calculator for generating a fourth average value A ₄ of 1 / n times the first adder values S ₁ and the second average value of the sum S _2,
A fifth calculator for generating a fifth mean value A ₅ of 1 / n times the second addition value S ₂ and the average value of the third adding value S _3,
A sixth calculator for generating a sixth mean value A ₆ of 1 / n times the third adding value S ₃ and the first average value of the sum S _1,
Upon receiving the fourth average value A ₄ , the fifth average value A ₅ , and the sixth average value A _{6 , (i) the first average value A 1} is the maximum according to the detection result of the maximum value selection circuit. When, the threshold value corresponding to the average value of the first average value A ₁ and the fifth average value A ₅ is generated, and (ii) when the second average value A ₂ is the maximum, the said The threshold value corresponding to the average value of the second average value A ₂ and the sixth average value A ₆ is generated (iii), and when the third average value A ₃ is the maximum, the third average value A ₃ an output circuit for generating the threshold value corresponding to the average value of the fourth average value a ₄ and,
A demodulator characterized by including. A demodulator for BMC signals modulated by the BMC (Biphase Mark Code) method.
A counter that measures the edge-to-edge distance over multiple symbol periods during a preamble period that alternates between symbols 1 and 0.
A threshold value determination unit that generates a threshold value based on a value obtained by adding and averaging the edge-to-edge distance corresponding to symbol 1 and the edge-to-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The threshold value determination unit
A register that holds n x 3 edge-to-edge distance measurements measured over 2 x n symbol periods, and
3 × i-2 th (i = 1, ... n) and adding the first measurement value group including measurements of distance between the edges of the first adder for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) and adding the second measurement value group including measurements of distance between the edges of the second adder to generate a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of a third adder for generating a third adding value S _3,
A first arithmetic unit that multiplies the first addition value S ₁ by 1 / n and outputs the first average value A _{1 and}
A second arithmetic unit that multiplies the second addition value S ₂ by 1 / n and outputs the second average value A _2.
A third arithmetic unit that multiplies the third addition value S ₃ by 1 / n and outputs the third average value A _{3 and}
A maximum value selection circuit that detects the largest of the first average value A ₁ , the second average value A ₂ , and the third average value A _3.
A seventh arithmetic unit that generates a _{seventh average value A 7} representing the average value of the first average value A ₁ and the second average value A _2.
An eighth arithmetic unit that generates an _{eighth average value A 8} representing the average value of the second average value A ₂ and the third average value A _3.
A ninth arithmetic unit that generates a _{ninth average value A 9} representing the average value of the third average value A ₃ and the first average value A _{1 and the like.}
Upon receiving the 7th average value A ₇ , the 8th average value A ₈ , and the 9th average value A _{9 , (i) the first average value A 1} is the maximum according to the detection result of the maximum value selection circuit. When, the threshold value corresponding to the average value of the first average value A ₁ and the eighth average value A ₈ is generated, and (ii) when the second average value A ₂ is the maximum, the said The threshold value corresponding to the average value of the second average value A ₂ and the ninth average value A ₉ is generated (iii), and when the third average value A ₃ is the maximum, the third average value A ₃ an output circuit for generating the threshold value corresponding to the average value of the seventh average value a ₇ and,
A demodulator characterized by including. A demodulator for BMC signals modulated by the BMC (Biphase Mark Code) method.
A counter that measures the edge-to-edge distance over multiple symbol periods during a preamble period that alternates between symbols 1 and 0.
A threshold value determination unit that generates a threshold value based on a value obtained by adding and averaging the edge-to-edge distance corresponding to symbol 1 and the edge-to-edge distance corresponding to symbol 0 with a weighting of 1: 2.
With
The threshold value determination unit
A register that holds n x 3 edge-to-edge distance measurements measured over 2 x n symbol periods, and
3 × i-2 th (i = 1, ... n) and adding the first measurement value group including measurements of distance between the edges of the first adder for generating a first sum value S _1,
3 × i-1 th (i = 1, ... n) and adding the second measurement value group including measurements of distance between the edges of the second adder to generate a second sum value S _2,
3 × i-th (i = 1, ... n- 1) by adding the third measurement value group including measurements of distance between the edges of a third adder for generating a third adding value S _3,
A first arithmetic unit that multiplies the first addition value S ₁ by 1 / n and outputs the first average value A _{1 and}
A second arithmetic unit that multiplies the second addition value S ₂ by 1 / n and outputs the second average value A _2.
A third arithmetic unit that multiplies the third addition value S ₃ by 1 / n and outputs the third average value A _{3 and}
A maximum value selection circuit that detects the largest of the first added value S ₁ , the second added value S ₂ , and the third added value S _{3.
A tenth arithmetic unit that generates a tenth addition value S 10} representing an addition value of the first addition value S ₁ and the second addition value S ₂ , and a tenth arithmetic unit.
An eleventh arithmetic unit that generates an _{eleventh addition value S 11} representing an addition value of the second addition value S ₂ and the third addition value S _{3,
A twelfth arithmetic unit that generates a twelfth addition value S 12} representing an addition value of the third addition value S ₃ and the first addition value S ₁ , and a twelfth arithmetic unit.
Upon receiving the tenth addition value S ₁₀ , the eleventh addition value S ₁₁ , and the twelfth addition value S _{12 , (i) the first addition value S 1} is the maximum according to the detection result of the maximum value selection circuit. When, the _{threshold value corresponding to S 1} / (2 × n) + S ₁₁ / (4 × n) is generated, and (ii) when the second addition value S ₂ is maximum, S ₂ /. The threshold value corresponding to (2 × n) + S ₁₂ / (4 × n) is generated, and (iii) when the third addition value S ₃ is the maximum, S ₃ / (2 × n) + S ₁₀ An output circuit that generates the threshold value according to / (4 × n) and
A demodulator characterized by including.

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