JP2008072214A - Cross-correlation circuit and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily constitute a cross-correlation circuit without greatly increasing the circuit scale. <P>SOLUTION: The cross-correlation circuit 1 includes a correlation value calculating means 2 of calculating a correlation value between an input signal A(nT) and a known comparison signal B(nT), an amplitude information output means 3 of outputting an amplitude information signal R(t) corresponding to an average amplitude of the input signals A(nT), a normalizing means 4 of normalizing the correlation value by using the amplitude information signals R(t), and a cross-correlation value calculating means 5 of calculating a cross-correlation value by using the normalized correlation value. This circuit uses the amplitude information signals R(t) without increasing the circuit scale instead of performing arithmetic processing for calculating the sum of products of squares of the input signals A(nT). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cross-correlation circuit and an electronic device, and more particularly to a cross-correlation circuit that generates a cross-correlation value by digital signal processing and an electronic device including the cross-correlation circuit.

  FIG. 8 shows a basic configuration of a cross-correlation circuit that receives an input signal A (t) and outputs a cross-correlation function C (t). In general, the correlation value can be expressed by multiplication of the input signal A (t) and the comparison signal B (t), that is, the numerator of the equation shown in FIG. However, in order to obtain the correlation value regardless of the level of the input signal, it is necessary to normalize by the square root of the sum of products of the squares of the respective signals (see, for example, Patent Document 1).

が計算される。このとき、比較信号Ｂ（ｔ）は既知であるため、

は予め机上で計算可能である。しかし、それ以外の部分、つまり

については、信号が入力される毎に計算する必要がある。 As shown in FIG. 8, when obtaining the cross-correlation value between the input signal A (t) and the known comparison signal B (t),

Is calculated. At this time, since the comparison signal B (t) is known,

Can be calculated in advance on a desk. But the other part, that is

Must be calculated each time a signal is input.

JP 2005-117199 A

を求める。 A circuit example of the conventional cross-correlation circuit is shown in FIG. (In this circuit example, analog integration is expressed by digital addition Σ). In this circuit the input signal A (nT) is input, the comparison signal _{B n, B n-1,} B n-2, for each of _{·· B 1, A (nT)} , A ((n- 1) Multiply T), A ((n-2) T) ·· A (T) and add them

Ask for.

を計算する。そして、（式９）を（式１０）で除して、その値に

を乗算すると、（式６）に示した相互相関値を得ることができる。 For the input signals A (T), A (2T)... A ((n-1) T), A (nT), the square root of these square sums,

Calculate Then, (Equation 9) is divided by (Equation 10) to obtain the value.

Is multiplied, the cross-correlation value shown in (Expression 6) can be obtained.

  When obtaining the cross-correlation value by the cross-correlation circuit described above, it is not easy to calculate (Equation 10). In particular, a square product-sum calculation process or a square root calculation process requires a large number of gates and is limited in speed. For example, when the input signal is expressed by 8 bits, it is necessary to perform at least 16-bit arithmetic processing by squaring, and when the number of stages for performing this operation is 31 taps, it is necessary to cumulatively add them 31 times. In addition, the square root calculation process requires an enormous number of gates. In this case, since the number of operations that must be processed in one clock increases, speed constraints are also added.

  As described above, when the conventional cross-correlation circuit is configured with a digital signal processing circuit, there are problems that the circuit scale and power consumption increase, and speed restriction occurs. In particular, when the cross-correlation circuit is applied to a frame synchronization circuit of a radio receiver, an increase in circuit scale and an increase in power consumption are serious problems.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cross-correlation circuit and an electronic apparatus that can easily configure the cross-correlation circuit without significantly increasing the circuit scale. That is.

  A cross-correlation circuit according to the present invention includes a correlation value calculation unit that calculates a correlation value between an input signal and a known comparison signal, an amplitude information output unit that outputs an amplitude information signal of the input signal, and the amplitude information signal. And normalizing means for normalizing the correlation value, and cross-correlation value calculating means for calculating a cross-correlation value using the normalized correlation value.

  The electronic apparatus according to the present invention includes a correlation value calculation unit that calculates a correlation value between an input signal and a known comparison signal, an amplitude information output unit that outputs an amplitude information signal of the input signal, and the amplitude information signal And a cross-correlation circuit that includes a normalizing unit that normalizes the correlation value by using and a cross-correlation value calculating unit that calculates a cross-correlation value by using the normalized correlation value. . Other features of the present invention are described in detail below.

  According to the present invention, it is possible to obtain a cross-correlation circuit and an electronic device that can easily configure a cross-correlation circuit without greatly increasing the circuit scale.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

が計算される。ここで、（式１）の分子

については、信号が入力される毎に計算する必要がある。（式１）のＲ（ｔ）は、電圧等として出力される振幅情報信号である。 Embodiment 1 FIG.
FIG. 1 shows a basic configuration of the cross-correlation circuit according to the first embodiment. In this configuration, when the input signal A (t) is input, the cross-correlation function C (t) is used using the known comparison signal B (t).

Is calculated. Where the numerator of (formula 1)

Must be calculated each time a signal is input. R (t) in (Expression 1) is an amplitude information signal output as a voltage or the like.

の項は、入力信号Ａ（ｔ）のエネルギーの累積加算の平方根であり、入力信号Ａ（ｔ）の平均振幅に対応した値となる。本実施の形態１では、この値に相当するものとして、上述した振幅情報信号Ｒ（ｔ）の値を用いる。 Here, of (Formula 6) of the prior art,

Is a square root of the cumulative addition of energy of the input signal A (t) and has a value corresponding to the average amplitude of the input signal A (t). In the first embodiment, the value of the amplitude information signal R (t) described above is used as the value corresponding to this value.

は、予め机上で計算可能である。 Since the comparison signal B (t) is already known as described above,

Can be calculated in advance on a desk.

を求める。 Next, the procedure for obtaining the cross-correlation function C (t) shown in FIG. 1 will be described with reference to the circuit diagram of FIG. The cross-correlation circuit 1 includes an adder 2 as a correlation value calculation unit that calculates a correlation value between the input signal A (nT) and the known comparison signal B (nT). Here, the term of analog integration shown in FIG. 1 is represented by digital addition Σ. In the circuit of FIG. 2, when the input signal A (nT) is input, the adder 2, the comparison signal _{B n, B n-1,} B n-2, for each of · · _{B 1,} A ( nT), A ((n-1) T), A ((n-2) T)... A (T), and adding them to obtain a correlation value

Ask for.

  Further, the cross-correlation circuit 1 has amplitude information output means 3 for outputting an amplitude information signal R (t) corresponding to the average amplitude of the input signal A (nT). The correlation value calculated by the adder 2 is normalized by the normalizing means 4 using the amplitude information signal R (t). Specifically, the normalizing means 4 performs a calculation (division) by dividing the value of (Equation 4) by the amplitude information signal R (t).

を乗算して、（式１）の相互相関関数Ｃ（ｔ）を求める。 The cross-correlation circuit 1 has a cross-correlation value calculation means 5 for calculating a cross-correlation value using the correlation value normalized by the normalization means 4. Specifically, a value obtained by dividing the value of (Equation 4) by the amplitude information signal R (t),

To obtain the cross-correlation function C (t) of (Equation 1).

  As described above, in the first embodiment, when obtaining the cross-correlation function C (t), the amplitude information signal R (t) is assumed to correspond to the square root of the cumulative addition of energy of the input signal A (nT). The value was used. Thereby, the calculation which calculates | requires the denominator of (Formula 8) of a prior art can be skipped. Therefore, the cross-correlation circuit can be easily configured without greatly increasing the circuit scale.

  Next, a modification of the first embodiment will be described. Instead of the amplitude information signal R (t) used in (Equation 1) of the first embodiment, the square root of the amplitude information signal R (t) may be used. In this case, as shown in FIG. 3, the cross-correlation function C (t) is obtained by replacing the R (t) term in (Equation 1) with √R (t).

  Even in the case of this modification, as shown in the circuit diagram of FIG. 4, the calculation for obtaining the denominator of (Formula 8) of the prior art can be omitted. Therefore, as in the case of FIGS. 1 and 2, the cross-correlation circuit can be easily configured without increasing the circuit scale.

Embodiment 2. FIG.
In the second embodiment, an example in which the cross-correlation circuit of the first embodiment is applied to a frame synchronization circuit of a radio receiver will be described. As shown in FIG. 5, the received signal A (t) and the received electric field intensity corresponding to the received electric field intensity display (hereinafter referred to as “RSSI”) are input to the frame synchronization circuit 7 via the RF receiving circuit 6. Is done. The RSSI value is a reception level signal corresponding to the reception level output from the RF reception circuit 6. The frame synchronization circuit 7 includes a synchronization circuit 8 and a cross-correlation circuit 1 and outputs a synchronized reception signal A ′ (t).

  In the second embodiment, the RF receiving circuit 6 is used as the amplitude information output means shown in the first embodiment, and the RSSI value output from the RF receiving circuit 6 is used as the amplitude information signal. In a general radio receiver, the RSSI value is output as a voltage value corresponding to the received electric field level in the RF receiving circuit, that is, an analog signal. Accordingly, with the circuit configuration shown in FIG. 5, the RSSI value can be detected as a value proportional to the amplitude of the received electric field or a value proportional to the energy of the received electric field. Further, by passing through a low-pass filter, it can be detected as an average value for an arbitrary period.

  If the RSSI value is detected as a value proportional to the amplitude of the received electric field, it can be used in place of the amplitude information signal R (t). If the RSSI value is detected as a value proportional to the energy value, it can be used as the square root of the amplitude information signal R (t).

  According to the second embodiment, it is possible to obtain an electronic device in which the cross correlation circuit can be easily configured.

Embodiment 3 FIG.
In the third embodiment, an example in which a reception level from an automatic gain control circuit (hereinafter referred to as an AGC circuit) is used instead of the amplitude information signal R (t) described in the first embodiment will be described. As shown in FIG. 6, an AGC circuit 9 that outputs a gain control signal to the RF receiving circuit 6 and outputs a reception level signal to the frame synchronization circuit 7 is provided. Although not shown, the AGC circuit 9 has a circuit for obtaining an average value of the reception levels of the reception signal A (t), and the value calculated by the circuit is used as the amplitude information signal R (t). be able to.

  In the third embodiment, the AGC circuit 9 is used as the amplitude information output means shown in the first embodiment, and the reception level signal output from the AGC circuit 9 is used as the amplitude information signal. As described above, the AGC circuit 9 of FIG. 6 includes a circuit for calculating the average value of the reception levels. By using this circuit, it is not necessary to mount the average value of the reception level in the cross-correlation circuit. Therefore, according to the third embodiment, it is possible to obtain an electronic device that can easily configure a cross-correlation circuit without significantly increasing the circuit scale.

  FIG. 7 shows another circuit example according to the third embodiment. In the RF receiving circuit 6 of this circuit, an amplifier 10 and a mixer 11 are connected in series, and a baseband signal is output via an A / D converter 12. The reception level is detected via the analog RSSI 13. Even with such a configuration, the same effect as that of the configuration of FIG. 6 can be obtained.

  In the first to third embodiments, the amplitude information signal R (t) or the square root thereof is used instead of the circuit for performing complex calculations in the conventional cross-correlation circuit. Thereby, a circuit scale and power consumption can be reduced. Further, it can be made unnecessary for the square root and cumulative addition, and the speed limit can be relaxed.

  In the first to third embodiments described above, the cross-correlation circuit and the electronic device including the correlation circuit have been described. However, any baseband processing circuit or electronic device that includes these correlation circuits and performs communication may be used. Have the same effect.

2 is a diagram illustrating a basic configuration of a cross-correlation circuit according to Embodiment 1. FIG. 2 is a circuit diagram of a cross-correlation circuit according to Embodiment 1. FIG. FIG. 6 is a diagram showing a basic configuration of a cross-correlation circuit according to a modification example of the first embodiment. FIG. 6 is a circuit diagram of a cross correlation circuit according to a modification of the first embodiment. FIG. 6 is a diagram illustrating a configuration of an electronic device according to a second embodiment. FIG. 6 is a diagram illustrating a configuration of an electronic device according to a third embodiment. FIG. 6 is a diagram illustrating a configuration of an electronic device according to a third embodiment. It is a figure which shows the basic composition of the conventional cross correlation circuit. It is a circuit diagram of the conventional cross correlation circuit.

Explanation of symbols

1 cross-correlation circuit, 2 adder, 3 amplitude information output means, 4 normalization means, 5 cross-correlation value calculation means, 6 RF reception circuit, 7 frame synchronization circuit, 8 synchronization circuit, 9 automatic gain control circuit (AGC circuit) 10 amplifier, 11 mixer, 12 A / D converter, 13 analog RSSI.

Claims (6)

Correlation value calculating means for calculating a correlation value between the input signal and the known comparison signal;
Amplitude information output means for outputting an amplitude information signal of the input signal;
Normalizing means for normalizing the correlation value using the amplitude information signal;
Cross-correlation value calculating means for calculating a cross-correlation value using the normalized correlation value;
A cross-correlation circuit comprising:   2. The cross-correlation circuit according to claim 1, wherein an RF reception circuit is used as the amplitude information output means, and the amplitude information signal is a reception level signal corresponding to a reception level output from the RF reception circuit. .   2. The cross-correlation circuit according to claim 1, wherein an automatic gain control circuit is used as the amplitude information output means, and the amplitude information signal is a reception level signal output from the automatic gain control circuit. Correlation value calculating means for calculating a correlation value between the input signal and the known comparison signal;
Amplitude information output means for outputting an amplitude information signal of the input signal;
Normalizing means for normalizing the correlation value using the amplitude information signal;
Cross-correlation value calculating means for calculating a cross-correlation value using the normalized correlation value;
An electronic device comprising a cross-correlation circuit including:   5. The electronic apparatus according to claim 4, wherein an RF reception circuit is used as the amplitude information output means, and the amplitude information signal is a reception level signal corresponding to a reception level output from the RF reception circuit.   5. The electronic apparatus according to claim 4, wherein an automatic gain control circuit is used as the amplitude information output means, and the amplitude information signal is a reception level signal output from the automatic gain control circuit.

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