JP2018160859A - BMC demodulator and threshold generation method for BMC demodulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a demodulator and a method of a BMC signal capable of setting an appropriate threshold value by a method different from the conventional method.SOLUTION: A preamble including symbols 1 and 0 alternately is received (S100). Then, an edge-to-edge distance (time length) D is measured over a symbol periods Tto Tof 2×n (n≥2) included in the preamble (S102). Then, on the basis of a value obtained by adding and averaging the inter-edge distance Dcorresponding to the symbol 1 and the inter-edge distance Dcorresponding to the symbol 0 with a weight of 1: 2, a threshold value Sis generated (S104).SELECTED DRAWING: Figure 3

Description

  The present invention relates to BMC (Biphase Mark Code) demodulation technology.

  As a digital data encoding method, a BMC (Biphase Mark Code) method is known. BMC is a type of Manchester code, and is conventionally used for audio signal transmission, and recently, for wirelessly powered Qi standards and USB (Universal Serial Bus) PD (Power Delivery) standards.

FIG. 1 is a waveform diagram of a BMC encoded signal (hereinafter referred to as BMC signal). In the BMC signal, a transition always occurs at a symbol boundary. Assuming that the symbol period is T ₀ , when the symbol value is 1, the symbol period T ₀ includes two edges, and thus the distance between the edges becomes 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.

A demodulator that demodulates the BMC signal determines a symbol by measuring the distance between 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 two symbols can be set, and the value of the symbol can be determined based on a comparison result between the measured distance between edges and the threshold value. The threshold value in this 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. When the fluctuation range of the symbol period T ₀ is large, if the threshold value is kept constant, the symbol value is erroneously determined. Therefore, in an application in which the fluctuation of the symbol period T _SYM is large, a preamble having a known symbol value is arranged, and an optimum threshold is set using the preamble.

FIG. 2 is a diagram for explaining a threshold setting method 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 in the preamble period. The histogram is divided into a symbol 1 count group and a symbol 0 count group. 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.

Japanese Patent Laying-Open No. 2006-158025

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

  The present invention has been made in view of these problems, and one of exemplary purposes of an aspect thereof is to generate a BMC signal demodulator capable of setting an appropriate threshold value using a method different from the conventional method and to generate a threshold value. In providing a method.

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

The process 3 for generating the threshold value may include the following processes.
(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) A first intermediate value M ₁ , a second intermediate value M ₂ , and a third intermediate value M _{3 corresponding} to the first addition value S ₁ , the second addition value S ₂ , and the third addition value S ₃ are obtained. Compare.
(Process 3-6) The measurement value group corresponding to the maximum intermediate value is associated with symbol 0, and the two measurement 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 = first measurement value group Symbol 1 = second measurement value group, third measurement value group Pattern 1 Symbol 0 = second measurement value group Symbol 1 = third measurement value group, first measurement value group Pattern 1 Symbol 0 = third measurement value group Symbol 1 = first measurement value group, second measurement value group

Each of the intermediate values M _{1 to} M ₃ may be 1 / n times the corresponding added value S _{1 to} S ₃ .

When the average value of the measurement value group corresponding to symbol 0 is A _SYM0 and the average value of the two measurement 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
Depending on.

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

When the addition value corresponding to symbol 0 is S _SYM0 and the two addition 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)
Depending on.

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

The threshold value determination unit includes a register that holds measurement values of the distance between n × 3 edges measured over 2 × n symbol periods, and 3 × i−2th (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) Are added to a third adder that generates a third added value S ₃ , a first added value S ₁ , a second added value S ₂ , and a third added value S ₃ . A corresponding first intermediate value M ₁ , second intermediate value M ₂ , and third intermediate value M ₃ may be compared, and a maximum value selection circuit that detects the maximum intermediate value may be included.

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

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

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

  Note that any combination of the above-described components, or a conversion of the expression of the present invention between methods, apparatuses, and the like is also effective as an aspect of the present invention. Further, the description of this item (means for solving the problem) does not explain all the essential features of the present invention, and therefore a sub-combination of these described features can also be the present invention. .

  According to the present invention, an appropriate threshold value can be set by a method different from that of the prior art.

It is a wave form 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 production | generation method of the threshold value for the demodulation process of a BMC signal. FIGS. 4A and 4B are diagrams illustrating threshold value generation based on the flowchart of FIG. It is a figure which shows the relationship between the timing which starts the measurement of the distance between edges in a preamble period, and the distance between edges measured. It is a flowchart of the process which determines the correspondence of the measured distance between edges, and the symbols 1 and 0. It is a block diagram of a demodulator. It is a circuit diagram of the demodulator according to the first embodiment. It is a circuit diagram of the demodulator according to the second embodiment. FIG. 6 is a circuit diagram of a demodulator according to a third embodiment.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this 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. Including the case of being indirectly connected through other members that do not substantially affect the state of connection, or do not impair the functions and effects achieved by the combination thereof.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  FIG. 3 is a flowchart showing a method for generating a threshold for demodulating a BMC signal. Note that the flowcharts referred to in this specification do not limit the order of each process, and a plurality of processes can be appropriately switched as long as there is no problem.

A preamble including alternating symbols 1 and 0 is received (S100). Such a preamble is completely DC balanced. The inter-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).

FIGS. 4A and 4B are diagrams illustrating threshold value generation based on the flowchart of FIG. It is a wave form diagram which shows the production _| generation process of threshold value _STH . S _RX represents a received signal in the preamble period. 2 × n inter-edge distances D ₁ corresponding to symbol 1 are included in 2 × n symbol periods, and n inter-edge distances D ₀ corresponding to symbol 0 are included.

2 × n pieces of the mean value _{D 1AVE} edge distance _{D 1} is represented by the formula (1a), the average value _{D 0AVE} of n edge distance _{D 0} is expressed by formula (1b).
D _1AVE = ΣD ₁ / (2n) (1a)
D _0AVE = ΣD ₀ / n (1b)
In the present embodiment, the threshold value S _TH to be _obtained is defined according to the average value D _AVE of the average value D _1AVE of the edge distance D _{1 and} the average value D _0AVE of the edge distance D ₀ . Here, for simplicity of explanation, the threshold value S _TH is assumed to be equal to the average value D _AVE , but is not limited thereto as will be described later.
S _{TH ≈D AVE} = (D _1AVE + D _0AVE ) / 2 (2)

When the expressions (1a) and (1b) are substituted into the expression (2), the expression (3) is obtained.
S _TH = {ΣD ₁ / (2n) + ΣD ₀ / n} / 2
= (ΣD ₁ + 2ΣD 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 It shows that it is responding.

FIG. 4B is a histogram of the measured distance between edges. The left mountain represents the distribution of the edge distance D ₁ corresponding to the symbol 1, and the right mountain represents the distribution of the edge distance D ₀ corresponding to the symbol 0. The threshold value S _TH is set near the center of the average value D _1AVE of the left mountain and the average value D _0AVE of the right mountain.

The above is the generation method of the threshold value _{STH according} to the embodiment. According to this method, it is possible to generate an appropriate threshold value _STH by a 1: 2 weighted averaging process without requiring complicated processing such as peak search. The simplicity of the process contributes to the simplification of hardware for realizing it as will be described later.

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 relationship between the measured distances between edges and the symbols 1 and 0 changes according to the timing at which the measurement of the distance between edges starts. FIG. 5 is a diagram illustrating the relationship between the timing for starting the measurement of the distance between edges in the preamble period and the measured distance between edges.

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

  Here, processing for determining whether the measured distance between edges 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 distance between edges and the symbols 1 and 0. A measured value of the distance between edges over 2 × n symbol periods T _SYM is held (S200). The first measurement value group (a in FIG. 5) including the measurement values of the 3 × i−2nd (i = 1,... N) edge-to-edge distance is added to generate a first addition 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) edge-to-edge distance is added, and the third added value S _{3 is} added. 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 measurement value group corresponding to the maximum intermediate value is associated with symbol 0, and the two measurement value groups corresponding to the remaining two intermediate values are associated with symbol 1 (S210).

For example, 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 addition values S _{1 to} S ₃ themselves.

  According to this process, it is possible to determine which symbol the measurement value group corresponds to. Further, since the calculations in the processes S202, S204, and S206 are the same as the addition average process S104 in FIG. 2, the addition value or the intermediate value generated in the processes S202, S204, and S206 is used in the process S104 in FIG. Thus, the calculation cost can be reduced.

Subsequently, a specific calculation method of the threshold value _STH will be described.
(First calculation method)
When the average value of the measurement value group corresponding to the symbol 0 is A _SYM0 , and the average value of the two measurement value groups corresponding to the symbol 1 is A _SYM11 and A _SYM12 , the threshold value S _TH is
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
Can be determined according to Since division by 2 or 4 can be realized by bit shift, the operation cost is low.

(Second calculation method)
When the addition value corresponding to the symbol 0 is S _SYM0 and the two addition values corresponding to the symbol 1 are S _SYM11 and S _SYM12 , the threshold value S _TH is given by
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
Can be determined 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 subsequent 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 inter-edge distance D over a plurality of 2 × n symbol periods T _SYM in a preamble period in which symbols 1 and 0 are alternately included. The threshold value determination unit 110 performs an arithmetic operation on the distance obtained by averaging the inter-edge distance D ₁ corresponding to the symbol ₁ and the inter-edge distance D ₀ corresponding to the symbol 0 with a weighting of 1: 2. A threshold value S _TH is generated.

  The present invention is understood as the flowchart of FIG. 3 or the block diagram of FIG. 7 or extends to various methods, devices, and circuits derived from the above description, and is not limited to a specific configuration. In the following, more specific embodiments and modifications will be described in order not to narrow the scope of the present invention but to help understanding the essence and circuit operation of the invention and to clarify them.

(First embodiment)
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 calculator 131 to a sixth calculator 136, and an output circuit 150A.

The register 112 holds the measured values of the n × 3 inter-edge distances D measured over 2 × n symbol periods T _{SYM1 to} T _SYM2n . The register 112 can be a shift register. 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 The measured values b _{1 to} b _n of the −1th (i = 1,... N) edge-to-edge distance are referred to as a second measured value group, and the 3 × ith (i = 1,... N−1) edge. The measured values c _{1 to} c _n of the inter-distance are referred to as a third measured 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 measurement value groups b _{1 to} b _n to generate a second addition value S ₂ . The third adder 123 adds the third measurement value groups c _{1 to} c _n to generate a third addition value S ₃ .

First computing unit 131, a first addition value _{S 1} 1 / n multiplied to generate the first average value _{A 1.} The second computing unit 132, a second addition value _{S 2} 1 / n multiplied to produce a second average value _{A 2.} Third arithmetic unit 133, a third adder value _{S 3} 1 / n multiplied to produce a third average value _{A 3.} When n = 2 ^m , each of the first computing unit 131 to the third computing unit 133 can be configured by a bit shifter that shifts input data by m bits downward.

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} And the maximum intermediate value M _MAX is detected and output. In FIG. 8, a first intermediate value M ₁ , a second intermediate value M ₂ , and a third intermediate value M ₃ are a first average value A ₁ , a second average value A ₂ , and a third average value A ₃ , respectively.

As a result of the comparison by the maximum value selection circuit 130, the measurement value group corresponding to the maximum intermediate value M _MAX is associated with the symbol 0, and the two measurement value groups corresponding to the remaining two intermediate values are associated with the symbol 1. It is done.

The fourth calculator 134 generates a fourth average value _{A 4} of 1 / n times the first addition values _{S 1} and the second average value of the sum _{S 2.} Fifth computing unit 135 generates the 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.} Sixth computing unit 136 generates the sixth mean value _{A 6} of 1 / n times the third adding value _{S 3} average value of the first sum value _{S 1.} The fourth computing unit 134 to the sixth computing unit 136 may include an adder 170 and a computing unit 172, respectively. The adder 170 adds two inputs. The calculator 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 by m + 1 bits in the lower order.

The output circuit 150A generates (i) a threshold value S _TH 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 maximum, when ii) a second average value _{a 2} is a maximum, generates a threshold value _{S TH} in accordance with the second average value _{a 2} mean value of the sixth mean value _{a 6} (iii) third average value _{a 3} Is the maximum, a threshold value S _TH corresponding to the average value of the third average value A ₃ and the fourth average value A ₄ is generated.

For example, 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, when the maximum first average value _{A 1} (i), and select the fifth mean value _{A 5,} (ii) when the second average value _{A 2} is a maximum, the sixth mean value _{A 6} select, (iii) a third average value a ₃ when the maximum, selects the fourth average value a _4. The output average circuit 154 calculates the average value of the output M _MAX of the maximum value selection circuit 130 and the output A _SEL of the selector 152. The output of the output averaging circuit 154 corresponds to the provisional threshold value _STH .

Adder 156 subtracts 1 from provisional threshold value S _TH to generate threshold value S _TH1 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, when the measured distance between edges is shorter than the threshold value S _TH1, it is determined as symbol 1, and when the measured distance between edges is longer than the threshold value S _TH0 , it is determined as symbol 0. it can.

The output M _MAX of the maximum value selection circuit 130 represents the average value A _SYM0 of the measurement value group corresponding to the symbol 0. When the average value of the two measurement value groups corresponding to 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 value S _TH 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 in FIG. 8 generates a threshold value based on the above-described first calculation method.

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

Seventh computing unit 137 generates the seventh average value _{A 7} representing the first average value _{A 1} and the average value of the second average value _{A 2.} Eighth computing unit 138 generates an eighth average value _{A 8} representing the second average value _{A 2} and the average value of the third average value _{A 3.} Ninth computing unit 139 generates the ninth mean value _{A 9} representing a third average value _{A 3} mean value of the first average value _{A 1.} The seventh computing unit 137 to the ninth computing unit 139 can be configured in the same manner as the fourth computing unit 134 to the sixth computing 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 determined according to the detection result of the maximum value selection circuit 130. When it is maximum, threshold values S _TH1 and S _TH0 corresponding to the average value of the first average value A ₁ and the eighth average value A ₈ are generated, and (ii) when the second average value A ₂ is maximum Threshold values S _TH1 and S _TH0 corresponding to the average value of the second average value A ₂ and the ninth average value A ₉ are generated. (Iii) When the third average value A ₃ is the maximum, the third average value Threshold values S _TH1 and S _TH0 corresponding to the average value of A ₃ and the seventh average value A ₇ are generated. The configuration of the output circuit 150B is the same as that of the output circuit 150A in FIG.

Also in this demodulator 100B, the provisional threshold value S _TH that 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 can be understood that the demodulator 100B in FIG. 9 generates a threshold value based on the above-described first calculation method.

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

10 calculator 140 generates the tenth addition value _{S 10} representing the first sum values _{S 1} and the second sum value of the sum _{S 2.} 11 calculator 141 generates an eleventh summation value _{S 11} representing the second addition value of the sum _{S 2} and the third adding value _{S 3.} 12th calculator 142 generates a twelfth summation value _{S 12} representing the third adding value _{S 3} a first addition value of the sum _{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, 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 Is the maximum, threshold values 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 maximum. Then, threshold values S _TH1 and S _TH0 corresponding to S ₃ / (2 × n) + S ₁₀ / (4 × n) are generated.

The selector 160 receives the tenth addition value S ₁₀ , the eleventh addition value S ₁₁ , and the twelfth 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 bit shifters. The output of the calculator 166 represents the provisional threshold value _STH .

The output of the maximum value selection circuit 130C represents the added value S _SYM0 corresponding to the symbol 0. The output of the selector 160 is a sum S _SYM11 + S _SYM12 of two addition values S _SYM11 and S _SYM12 corresponding to the symbol 1. Therefore, the provisional threshold value S _TH that is the output of the calculator 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-described second calculation method.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there. Hereinafter, such modifications will be described.

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

DESCRIPTION OF SYMBOLS 100 ... Demodulator, 102 ... Counter, 110 ... Threshold value determination part, 112 ... Register, 121 ... 1st adder, 122 ... 2nd adder, 123 ... 3rd adder, 130 ... Maximum value selection circuit, 131 ... 1st calculator, 132 ... 2nd calculator, 133 ... 3rd calculator, 134 ... 4th calculator, 135 ... 5th calculator, 136 ... 6th calculator, 137 ... 7th calculator, 138 ... 8th arithmetic unit, 139 ... 9th arithmetic unit, 140 ... 10th arithmetic unit, 141 ... 11th arithmetic unit, 142 ... 12th arithmetic unit, 150 ... output circuit, 152 ... selector, 154 ... output averaging circuit, 156 158... Adder, 160... Selector, 162... Operator, 164.

Claims (16)

A threshold generation method for demodulating a BMC signal modulated by a BMC (Biphase Mark Code) method,
Receiving a preamble including alternating symbols 1 and 0;
Measuring an inter-edge distance over a plurality of symbol periods included in the preamble;
Generating the threshold based on a value obtained by averaging the distance between edges corresponding to symbol 1 and the distance between edges corresponding to symbol 0 with a weighting of 1: 2.
A generation method comprising: Generating the threshold comprises:
Holding a measurement of the distance between edges over 2 × n symbol periods;
Adding a first measurement value group including measurement values of 3 × i−2nd (i = 1,... N) edge-to-edge distances to generate a first addition value S ₁ ;
Adding a second measurement value group including measurement values of the 3 × i−1-th (i = 1,... N) edge-to-edge distance to generate a second addition value S ₂ ;
Adding a third measurement value group including measurement values of the 3 × i-th (i = 1,..., N−1) edge-to-edge distance to generate a third addition value S ₃ ;
A step of comparing the first intermediate value M ₁ , the second intermediate value M ₂ , and the third intermediate value M _{3 according} to the first addition value S ₁ , the second addition value S ₂ , and the third addition value S _3. When,
Associating a measurement value group corresponding to a maximum intermediate value with the symbol 0 and associating two measurement value groups corresponding to the remaining two intermediate values with the symbol 1;
The generation method according to claim 1, further comprising: Generating method according to claim 2, wherein each respective intermediate values _M 1 ~M ₃ is 1 / n times the corresponding sum values _S 1 to S _3. When the average value of the measurement value group corresponding to the symbol 0 is A _SYM0 , and the average value of the two measurement value groups corresponding to the symbol 1 are A _SYM11 and A _SYM12 ,
The threshold is
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
The generation method according to claim 3, wherein: Generating method according to claim 2, wherein each intermediate value M ₁ ~M _3, respectively, one whose corresponding addition value S ₁ to S _3. When the addition value corresponding to the symbol 0 is S _SYM0 and the two addition values corresponding to the symbol 1 are S _SYM11 and S _SYM12 ,
The threshold is
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
The generation method according to claim 5, wherein: A BMC signal demodulator modulated by a BMC (Biphase Mark Code) system,
A counter that measures a distance between edges over a plurality of symbol periods in a preamble period in which symbols 1 and 0 are alternately included;
A threshold value determination unit that generates a threshold value based on a value obtained by averaging the distance between edges corresponding to symbol 1 and the distance between edges corresponding to symbol 0 with a weighting of 1: 2;
A demodulator. The threshold determination unit
A register holding measurements of n × 3 inter-edge distances measured over 2 × n symbol periods;
A first adder that adds a first measurement value group including measurement values of the 3 × i−2nd (i = 1,... N) edge-to-edge distance and generates a first addition value S ₁ ;
A second adder that adds a second measurement value group including measurement values of the 3 × i−1th (i = 1,... N) edge-to-edge distance and generates a second addition value S ₂ ;
A third adder that adds a third measurement value group including measurement values of the 3 × i-th (i = 1,..., N−1) edge-to-edge distance and generates a third addition value S ₃ ;
Comparing the first intermediate value M ₁ , the second intermediate value M ₂ , and the third intermediate value M _{3 according} to the first addition value S ₁ , the second addition value S ₂ , and the third addition value S ₃ ; A maximum value selection circuit for detecting the maximum intermediate value;
Including
The demodulation according to claim 7, wherein a measurement value group corresponding to a maximum intermediate value is associated with the symbol 0, and two measurement value groups corresponding to the remaining two intermediate values are associated with the symbol 1. vessel. When the average value of the measurement value group corresponding to the symbol 0 is A _SYM0 , and the average value of the two measurement value groups corresponding to the symbol 1 is A _SYM11 , A _SYM12 ,
A _SYM0 / 2 + A _SYM11 / 4 + A _SYM12 / 4
The demodulator according to claim 8, wherein the threshold value corresponding to the frequency is generated. The threshold value determination unit is configured such that an addition value corresponding to the symbol 0 is S _SYM0 and two addition values corresponding to the symbol 1 are S _SYM11 and S _SYM12 .
S _SYM0 / (2 × n) + S _SYM11 / (4 × n) + S _SYM12 / (4 × n)
The demodulator according to claim 8, wherein the threshold value corresponding to the frequency is generated. The threshold determination unit
The first addition value _{S 1} 1 / n multiplied by a first arithmetic unit for outputting a first average value _{A 1,}
The second addition value _{S 2} to 1 / n multiplied by a second computing unit for outputting a second average value _{A 2,}
Said third adding value _{S 3} to 1 / n multiplied by the third computing unit for outputting a third average value _{A 3,}
The demodulator according to claim 8, further comprising: The threshold determination unit
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,
The fourth average value A ₄ , the fifth average value A ₅ , and the sixth average value A ₆ are received, and (i) the first average value A ₁ is maximum according to the detection result of the maximum value selection circuit. when it is configured to generate the threshold value corresponding to the average value of the first average value a ₁ and the fifth mean value a _5, when (ii) the second average value a ₂ is a maximum, the when generating the threshold value corresponding to said second average value a ₂ mean value of the sixth mean value a ₆ (iii) said third average value a ₃ is 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,
The demodulator according to claim 11, further comprising: The threshold determination unit
A seventh arithmetic unit for generating a seventh average value A ₇ representing the first average value A ₁ and the average value of the second average value A _2,
An eighth computing unit for 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,
A ninth computing unit for generating a ninth average value A ₉ representing the third average value A ₃ and the average value of the first average value A _1,
The seventh average value A ₇ , the eighth average value A ₈ , and the ninth average value A ₉ are received, and (i) the first average value A ₁ is maximum according to the detection result of the maximum value selection circuit. when it is, the above generates a threshold value corresponding to the average value of the first average value a ₁ and the eighth average value a _8, when (ii) the second average value a ₂ is a maximum, the when generating the threshold value corresponding to said second average value a ₂ mean value of the ninth mean value a ₉ (iii) said third average value a ₃ is 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,
The demodulator according to claim 11, further comprising: The threshold determination unit
A tenth arithmetic unit for generating a tenth addition value _{S 10} representing the first sum values _{S 1} and the second addition value of the sum _{S 2,}
A 11th calculator for generating an eleventh addition value _{S 11} representing the sum of the second sum value _{S 2} and the third adding value _{S 3,}
A twelfth calculator for generating a twelfth summation value _{S 12} representing the third adding value _{S 3} and the sum of the first sum value _{S 1,}
The tenth addition value S ₁₀ , the eleventh addition value S ₁₁ , and the twelfth addition value S ₁₂ are received, and (i) the first addition value S ₁ is maximum according to the detection result of the maximum value selection circuit. And 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 for generating the threshold value according to / (4 × n);
The demodulator according to claim 11, further comprising: A threshold generation method for demodulating a BMC signal modulated by a BMC (Biphase Mark Code) method,
Receiving a preamble including alternating symbols 1 and 0;
Measuring an inter-edge distance over a plurality of symbol periods included in the preamble;
A first measured value group including measured values of the 3 × i−2nd (i = 1,... N) edge-to-edge distance measured over 2 × n symbol periods, and the 3 × i−1th A second measurement value group including measurement values of edge distances (i = 1,... N) and a third measurement value including measurement values of edge distances of 3 × i-th (i = 1,... N−1). A group of measurement values, and
Associating one of the first measurement value group, the second measurement value group, and the third measurement value group with the symbol 0 and associating the remaining two with the symbol 1;
When the average value of the measurement value group associated with the symbol 0 is A _SYM0 , and the average value of the two measurement value groups associated with the symbol 1 is A _SYM11 and A _SYM12 , A _SYM0 / 2 + A _SYM11 / Generating the threshold according to 4 + A _SYM12 / 4;
A method comprising the steps of: A threshold generation method for demodulating a BMC signal modulated by a BMC (Biphase Mark Code) method,
Receiving a preamble including alternating symbols 1 and 0;
Measuring an inter-edge distance over a plurality of symbol periods included in the preamble;
A first measured value group including measured values of the 3 × i−2nd (i = 1,... N) edge-to-edge distance measured over 2 × n symbol periods, and the 3 × i−1th A second measurement value group including measurement values of edge distances (i = 1,... N) and a third measurement value including measurement values of edge distances of 3 × i-th (i = 1,... N−1). A group of measurement values, and
Associating one of the first measurement value group, the second measurement value group, and the third measurement value group with the symbol 0 and associating the remaining two with the symbol 1;
When the addition value of the measurement value group associated with the symbol 0 is S _SYM0 , and the addition value of the two measurement value groups associated with the symbol 1 is S _SYM11 and S _SYM12 , S _SYM0 / (2 × n) generating the threshold according to + S _SYM11 / (4 × n) + S _SYM12 / (4 × n);
A method comprising the steps of:

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