JP6827878B2 - Timing detector, timing control device, radio signal receiver and radio signal receiver for capsule endoscopy - Google Patents

Description

The present invention relates to a timing detection device, a timing control device, a radio signal receiving device, and a radio signal receiving device for a capsule endoscope.

In order to acquire data from a wireless signal from a transmitting device such as a capsule endoscope in a receiving device with high accuracy, it is important to be able to detect the timing of a part of the data in the received wireless signal with high accuracy. As a method for detecting the timing of such a part of data, a method for generating a clock synchronized with data from a received radio signal is known. For example, the symbol clock generation circuit proposed in Patent Document 1 uses a numerically controlled oscillator (NCO) to generate a clock for acquiring data from a radio signal.

JP-A-2009-033300

The NCO calculates the cumulative addition value at predetermined intervals of the addition value called the frequency adjustment value or the like, detects that the cumulative addition value overflows, and generates a clock based on the timing of this detection. Therefore, in NCO, the phase accuracy of the generated clock can be improved by increasing the operating frequency. However, if the operating frequency is increased, the power consumption will increase. In particular, in a mobile environment, the power that can be supplied by the battery is limited, so it is necessary to keep the power consumption particularly low.

The present invention has been made in view of the above circumstances, and is a timing detection device, a timing control device, a radio signal receiving device, and a capsule endoscopy capable of detecting timing with high accuracy while suppressing an operating frequency. It is an object of the present invention to provide a radio signal receiver for a mirror.

The timing detection device according to the first aspect of the present invention is a difference between the first calculation unit that calculates the cumulative addition value of the digital frequency adjustment value at a predetermined time interval and the threshold value of the cumulative addition value and the cumulative addition value. The cumulative addition value corresponds to the threshold value, and the cumulative addition value corresponds to the threshold value, and is between the predetermined time intervals, based on the second calculation unit for calculating the above, the first time when the cumulative addition value is calculated, and the difference. It is provided with a third calculation unit that calculates an existing second time.

The timing control device according to the second aspect of the present invention includes the timing detection device according to the first aspect and a clock setting unit that sets the second time as a clock reference timing.

The timing control device according to the third aspect of the present invention includes the timing detection device according to the first aspect and a timing setting unit that sets the second time as a reference timing for data acquisition.

The timing control device according to the fourth aspect of the present invention is based on the timing detection device according to the first aspect, the second time, and at least two data obtained at different timings. It includes a data generation unit that generates data that interpolates data between data.

The radio signal receiving device according to the fifth aspect of the present invention includes the timing control device according to any one of the second to fourth aspects, receives the radio signal transmitted from the transmitting device, and receives the radio signal. The frequency adjustment value is calculated from the data included in the signal.

The radio signal receiving device for the capsule endoscopy according to the sixth aspect of the present invention includes the timing control device according to any one of the second to fourth aspects, and is transmitted from the capsule endoscopy. The radio signal is received, and the frequency adjustment value is calculated from the data included in the radio signal.

According to the present invention, a timing detection device, a timing control device, a radio signal receiving device, and a radio signal receiving device for capsule endoscopy capable of detecting timing with high accuracy while suppressing an operating frequency are provided. Can be provided.

It is a block diagram which shows the structural example of the communication system which includes the radio signal receiving apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the 1st example of NCO. It is a figure which shows the operation of the 1st calculation part. It is a figure which shows the deviation between the timing of detection of overflow and the timing when the cumulative addition value y actually reaches the threshold value y'. It is a figure for demonstrating the condition which can make a slope a constant. It is a figure which shows the process which determines the phase of a clock from a time t'. It is a block diagram which shows the structure of the 2nd example of NCO. It is a figure which shows the process of determining the phase of data from time t'. It is a figure which shows the example of the table which associated Δt and Δy. It is a block diagram which shows the structure of the modification 3 which concerns on NCO. It is a figure which shows the example of linear interpolation of data. It is a figure which shows the example of the interpolation by the digital filter of data. It is a figure which shows the impulse response and the filter coefficient of the digital filter which has the characteristic which does not consider Δt. It is a figure which shows the relationship between the input data D _IN and the output data D _OUT when interpolated by the digital filter of the characteristic of FIG. 12A. It is a figure which shows the impulse response and the filter coefficient of the digital filter which has the characteristic which considered Δt. It is a figure which shows the relationship between the input data D _IN and the output data D _OUT when interpolated by the digital filter of the characteristic of FIG. 13A. It is a figure for demonstrating the process of obtaining the slope a from the cumulative addition value at arbitrary two times.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a communication system including a radio signal receiving device according to an embodiment of the present invention. Here, FIG. 1 is an example of application of a capsule endoscope to a communication system. The communication system 1 shown in FIG. 1 has a capsule endoscope 10, a receiving device 20, and a display 30.

The capsule endoscope 10 is a transmission device in the communication system 1. The capsule endoscope 10 has a capsule-shaped housing. An image sensor is provided inside the housing. Such a capsule endoscope 10 is introduced into a human body, for example, and acquires digital data (hereinafter, simply referred to as data) of an image in the body. Then, the capsule endoscope 10 modulates the acquired data to generate a radio signal, and transmits this radio signal to the receiving device 20.

The receiving device 20 receives the radio signal transmitted from the capsule endoscope 10 and demodulates the received radio signal. Then, the receiving device 20 outputs the demodulated data to the display 30. The receiving device 20 has an antenna 21, a demodulation unit 22, and a processing unit 23.

The antenna 21 is an element for receiving a radio signal transmitted from the capsule endoscope 10. The demodulation unit 22 restores the data acquired by the capsule endoscope 10 by demodulating the radio signal received via the antenna 21.

The processing unit 23 transfers the demodulated data obtained by the demodulation unit 22 to the display 30. At this time, the processing unit 23 transfers the demodulated data output from the demodulated unit 22 to the display 30 in synchronization with the clock generated based on the demodulated data. Alternatively, the processing unit 23 acquires the demodulated data from the demodulation unit 22 based on the signal indicating the acquisition timing of the data generated based on the demodulated data, and transfers the demodulated data to the display 30. The processing unit 23 includes a threshold value generation unit 24, a frequency adjustment value generation unit 25, an NCO 26, a data acquisition unit 27, a first clock generation unit 28, and a second clock generation unit 29. The processing unit 23 is composed of, for example, an FPGA. The processing unit 23 may be composed of a CPU, an ASIC, or the like. Further, the processing unit 23 may be configured by a dedicated electric circuit that realizes the function of each block of the processing unit 23.

The threshold generation unit 24 generates the threshold value used in the NCO 26. This threshold value is a threshold value for determining the overflow of the cumulative addition value in NCO26. In the example of this embodiment, the NCO 26 outputs a clock synchronized with the demodulated data obtained by the demodulation unit 22 or a signal indicating the acquisition timing of individual data included in the demodulated data obtained by the demodulation unit 22. In order to generate a signal indicating such a clock or acquisition timing, the threshold value is generated based on the width of individual data included in the demodulated data obtained by the demodulation unit 22. For example, the threshold generation unit 24 estimates the phase of the center of each group of data included in the input demodulated data, and specifies the width of each data from the phase of the center of the estimated data. Then, the threshold value generation unit 24 generates a threshold value based on the width of the specified data (or its average value). Hereinafter, the threshold value will be referred to as a threshold value y'.

The frequency adjustment value generation unit 25 generates a frequency adjustment value. The frequency adjustment value determines the addition value in the cumulative adder used in the NCO 26. For example, the frequency adjustment value generation unit 25 includes the frequency of the demodulated data obtained by the demodulation unit 22, the bit width of the cumulative adder used in the NCO 26, and the frequency of the first clock which is the operating clock of the cumulative adder. Generates a frequency adjustment value based on. F the frequency of the to be generated clock (frequency demodulated data) in NCO26, the bit width of the accumulator N, when the frequency of the first clock and the f _clk, FCW that satisfies the conditions of the following (Equation 1) Is the frequency adjustment value. As the addition value to be input to the cumulative adder, it is desirable to input ΔF, which is an integer value of FCW. Further, ΔF / 2 ^N obtained by normalizing ΔF with 2 ^N may be input to the cumulative adder.
f = (FCW × f _clk ) / 2 ^N (Equation 1)

The NCO 26 is included in the clock or demodulation data synchronized with the demodulation data obtained by the demodulation unit 22 based on the threshold generated by the threshold generation unit 24 and the frequency adjustment value generated by the frequency adjustment value generation unit 25. Generates a signal indicating the acquisition timing of individual data. Therefore, the NCO 26 in this embodiment functions as a timing detection device or a timing control device. Details of NCO26 will be described later.

The data acquisition unit 27 acquires (samples) the demodulated data acquired by the demodulation unit 22 in units of individual data based on the clock generated by the NCO 26 or the signal indicating the data acquisition timing, and obtains the acquired data. The data is sequentially transferred to the display 30.

The first clock generation unit 28 includes, for example, a crystal oscillator and generates a first clock having a first frequency. The second clock generation unit 29 includes, for example, a crystal oscillator, and generates a second clock having a second frequency higher than the first frequency. The first clock is input to the NCO 26. The second clock is input to the NCO 26 and the data acquisition unit 27.

The display 30 is a display device such as a liquid crystal display and an organic EL display. The display 30 displays various images such as an image of the inside of the body obtained by the capsule endoscope 10 based on the data input from the receiving device 20.

FIG. 2 is a block diagram showing a configuration of a first example of NCO26 according to the present embodiment. The NCO 26 of the first example has a configuration in which a clock synchronized with the demodulated data obtained by the demodulation unit 22 is output to the data acquisition unit 27. The NCO 26 of the first example has a first calculation unit 101, a detection unit 102, a Δt generation unit 103, and a clock setting unit 104.

The first calculation unit 101 includes a cumulative adder. This cumulative adder operates in synchronization with the first clock CLK1 input from the first clock generation unit 28. This cumulative adder digitally adds the frequency adjustment value FCW each time the first clock CLK1 is input. That is, the first calculation unit 101 calculates the cumulative addition value y of the frequency adjustment value FCW at each predetermined time interval (first time interval) in which the first clock CLK1 is input.

The detection unit 102 operates in synchronization with the first clock CLK1 input from the first clock generation unit 28. The detection unit 102 compares the cumulative addition value y calculated by the first calculation unit 101 with the threshold value y'generated by the threshold value generation unit 24 each time the first clock CLK1 is input. Then, when the detection unit 102 detects that the cumulative adder of the first calculation unit 101 overflows (or the cumulative addition value y exceeds the threshold value y'), the time t _n and the time t immediately before that are detected. and outputs the accumulated value _{y n} at _n. The time output by the detection unit 102 may be the time t _{n + 1} when the overflow is detected, not the time t _n immediately before the overflow is detected.

The Δt generation unit 103 operates in synchronization with the first clock CLK1 input from the first clock generation unit 28. Based on the difference between the cumulative addition value y _n and the threshold value y'generated by the threshold value generation unit 24 and the time t _n , the time t'in which the cumulative addition value y corresponds to the threshold value y'is calculated. Here, the time when the cumulative addition value y becomes the value corresponding to the threshold value y'is, for example, the time when the cumulative addition value y coincides with the threshold value y'. The Δt generation unit 103 has a second calculation unit 201 and a third calculation unit 202. The second calculation unit 201 calculates the difference Δy between the cumulative addition value y _n and the threshold value y ′. The third calculation unit 202 calculates the time t'based on the difference Δy, and outputs the calculated time t'to the clock setting unit 104. Δt is the time difference between the time t ′ and the time t _n . The third calculation unit 202 has a conversion unit 301 and a correction unit 302. The conversion unit 301 converts the difference Δy of the cumulative addition value into the time difference Δt. The correction unit 302 calculates the time t ′, which is the second time, according to the time t _n and Δt, which are the first time.

The clock setting unit 104 sets the digital clock CLK synchronized with the demodulated data using t'as a reference timing for clock generation.

Hereinafter, the operation of the communication system 1 of the present embodiment will be described. First, the capsule endoscope 10 is introduced into the human body which is a subject. The capsule endoscope 10 acquires image data while moving inside an organ such as the stomach or small intestine according to its peristaltic movement. Then, the capsule endoscope 10 transmits the acquired data such as image data to the receiving device 20 as a wireless signal.

The demodulation unit 22 of the receiving device 20 demodulates the radio signal received from the capsule endoscope 10. The demodulated data is input to each of the threshold value generation unit 24, the frequency adjustment value generation unit 25, and the data acquisition unit 27. The threshold value generation unit 24 generates the threshold value y'by detecting the reference phase in the input demodulation data. The reference phase is, for example, the phase of the center of the data. The threshold value y'is input to the detection unit 102 and the second calculation unit 201. The frequency adjustment value generation unit 25 generates the frequency adjustment value FCW based on the frequency of the demodulated data. The frequency adjustment value FCW is input to the first calculation unit 101.

The first calculation unit 101 outputs the cumulative addition value y of the frequency adjustment value FCW in synchronization with the input of the first clock. FIG. 3 is a diagram showing the operation of the first calculation unit 101. The horizontal axis of FIG. 3 indicates the time t, and the horizontal axis of FIG. 3 indicates the cumulative addition value y. The first calculation unit 101 calculates the cumulative addition value y of the frequency adjustment value FCW according to the input of the first clock CLK1. Therefore, the cumulative addition value y increases discretely and linearly with respect to the change in time t. Therefore, the cumulative addition value y can be approximated by the approximate expression shown in the following (Equation 2).
y = at + b (Equation 2)

The detection unit 102 compares the cumulative addition value y calculated by the first calculation unit 101 with the threshold value y'. Then, when the detection unit 102 detects that the first calculation unit 101 has overflowed, it outputs the time t _n immediately before that and the cumulative addition value y _{n at the} time t _n .

Here, the detection unit 102 operates in synchronization with the first clock CLK1. Therefore, the timing at which the detection unit 102 can detect the overflow is also limited to the timing that coincides with the first time interval, which is the input interval of the first clock CLK1. Therefore, the time t _n is not always the time when the cumulative addition value y becomes the threshold value y'.

In FIG. 4, when the first clock CLK1 having a frequency of f _clk (MHz) is input to the cumulative adder, the detection unit 102 detects the overflow at t ₃₂ , which is the time corresponding to the 32nd clock. .. However, in reality, the cumulative addition value y reaches the threshold value y'at the time t ₃₁ + Δt between t ₃₁ which is the time corresponding to the 31st clock and t ₃₂ which is the time corresponding to the 32nd clock. .. The time t ₃₁ + Δt corresponds to the reference phase in generating the threshold value in the demodulated data, for example, the phase at the center of the data. Therefore, if Δt can be calculated, the phase at the center of the data can be detected with high accuracy. Such calculation of Δt is performed by the Δt generation unit 103. Hereinafter, the calculation of Δt will be described.

As described above, the cumulative addition value y can be represented by y = at + b. Therefore, the time t'can be calculated from the relationship of the following (Equation 3).
t'= (y'-b) / a (Equation 3)
Therefore, Δt can be calculated by the following (Equation 4).
Δt = t'-t _n = (y'-b) / a- (y _n- b) / a = Δy / a (Equation 4)
Here, a represents the slope of a straight line represented by (Equation 2). This slope a can be regarded as a constant when the frequency width required by the NCO 26 is not large. That is, as shown in FIG. 5, the difference between the slope a _H of the straight line when the required frequency is on the highest frequency side and the slope a _L of the straight line when the required frequency is on the lowest frequency side. If is small, a can be regarded as a constant. For example, in the communication system 1 of the present embodiment, the frequency required by the NCO 26 is determined by the clock used in the capsule endoscope 10 and the clock used in the receiving device 20. It can be considered that these clocks are determined by the design of the capsule endoscope 10 and the receiving device 20 and do not vary greatly. Therefore, in the communication system 1, a can be regarded as a constant.

The Δt generation unit 103 in the present embodiment calculates Δt based on (Equation 4). Specifically, the second calculation unit 201 of the Δt generation unit 103 calculates the difference Δy between the cumulative addition value y _n and the threshold value y ′. Then, the conversion unit 301 of the third calculation unit 202 converts the difference Δy into the difference Δt based on (Equation 4). After that, the correction unit 302 of the third calculation unit 202 calculates the time t ′ based on the time t _n and Δ t. The time t'is calculated from the following (Equation 5).
t'= t _n + Δt (Equation 5)

Here, when the detection unit 102 has a configuration in which outputs time t _{n + 1} in place of the time t _n, the second calculation unit 201 calculates a difference Δy between the cumulative addition value y _{n + 1} and the threshold value y' To do. Then, the correction unit 302 of the third calculation unit 202 calculates the time t'by subtracting Δt from t _{n + 1} .

After calculating t'in this way, the Δt generation unit 103 inputs the calculated t'to the clock setting unit 104. The clock setting unit 104 generates a digital clock synchronized with the demodulated data based on t'. A general NCO is configured so that a waveform of an arbitrary frequency can be generated by a table in which a cumulative addition value and an amplitude value are associated with each other. Here, if only a digital clock is generated, the amplitude values can only be 0 and 1, so that it is not always necessary to have a table in which the cumulative addition value and the amplitude of the waveform are associated with each other. That is, when generating a digital clock, if a predetermined phase of the demodulated data can be accurately determined, the clock CLK is generated with reference to that phase.

For example, when the phase in which the cumulative addition value y is the threshold value y'corresponds to the phase at the center of the demodulated data, the clock setting unit 104 sets the clock at the center phase, for example, as shown in FIG. The timing of the rising edge of the clock is determined so as to be the timing of. Then, the clock setting unit 104 generates a clock CLK having a frequency of f (MHz) with reference to the rising timing.

The clock setting unit 104 generates a clock CLK according to a second clock CLK2, which is a clock faster than the first clock CLK1. This is because the time t'= t _n + Δt is the time that exists during the first time interval. In the example of FIG. 8, the frequency of the second clock CLK2 is 8f _clk (MHz). In this case, the clock CLK can be generated with a resolution eight times that of the case where the clock CLK is generated based on the first clock CLK1. The higher the frequency of the second clock CLK2, the more accurate the clock CLK can be generated.

The data acquisition unit 27 operates in synchronization with the clock CLK generated by the clock setting unit 104 of the NCO 26. The data acquisition unit 27 recognizes the phase of the boundary of each data of the demodulated data obtained by the demodulation unit 22 based on the clock CLK generated by the clock setting unit 104 of the NCO 26, and acquires the data. Then, the data acquisition unit 27 sequentially transfers the acquired data to the display 30. Based on this data, the display 30 displays an image or the like obtained by the capsule endoscope 10.

FIG. 7 is a block diagram showing a configuration of a second example of the NCO 26 according to the present embodiment. The NCO 26 of the second example outputs a signal indicating the acquisition timing of the demodulated data obtained by the demodulation unit 22 to the data acquisition unit 27. In this case, the NCO 26 may have a first calculation unit 101, a detection unit 102, and a Δt generation unit 103. The configuration and operation of the first calculation unit 101, the detection unit 102, and the Δt generation unit 103 in the second example are the first calculation unit 101, the detection unit 102, and the Δt generation unit 103 in the first example. It is the same as the configuration and operation of. Therefore, the description will be omitted.

In the second example, the data acquisition unit 27 operates in synchronization with the second clock CLK2. The data acquisition unit 27 uses the value of t'input from the NCO 26 as a reference timing for data acquisition, determines the phase of each data of the demodulated data obtained by the demodulation unit 22, and acquires the data. For example, as shown in FIG. 8, the data acquisition unit 27 recognizes the phase of the center of the demodulated data obtained by the demodulation unit 22 from the value of t ′ and acquires the data. After acquiring the data, the data acquisition unit 27 sequentially transfers the acquired data to the display 30. Based on this data, the display 30 displays an image or the like obtained by the capsule endoscope 10. Since the data acquisition unit 27 operates in synchronization with the second clock CLK2, it is possible to acquire data with eight times the accuracy as in the case of operating in synchronization with the first clock CLK1.

As described above, in the present embodiment, the time at which the cumulative addition value y in the NCO 26 becomes the value corresponding to the threshold value y'is calculated by linear interpolation. As a result, even if the operating frequency of the NCO 26 is suppressed, the time at which the cumulative addition value y corresponds to the threshold value y'can be calculated with high accuracy. By suppressing the operating frequency of the NCO 26, it also leads to the suppression of the power consumption of the NCO 26.

Further, the clock setting unit 104 or the data acquisition unit 27 recognizes the timing of t'and acquires the demodulated data with high accuracy by acquiring the data based on the second clock CLK2, which is faster than the operating clock of the NCO 26. Can be done.

[Modification 1]
Hereinafter, a modified example of the present embodiment will be described. For example, when the frequency of the second clock CLK2 is not sufficiently high, it is conceivable that the clock CLK cannot be generated based on the time when the cumulative addition value y coincides with the threshold value y'. In this case, the time t'may be set so that it is near the time when the cumulative addition value y becomes the threshold value y'and is synchronized with the input interval of the second clock CLK2. That is, the time t'does not necessarily coincide with the time when the cumulative addition value y becomes the threshold value y'.

[Modification 2]
In the above-described embodiment, Δt is calculated by dividing the difference Δy of the cumulative addition values by the constant a. Here, if the possible range of frequencies is small, that is, if a can be regarded as a constant, Δt corresponding to various Δy is calculated in advance, and the relationship between Δy and Δt is stored in the conversion unit 301 as a table. You can also keep it.

FIG. 9 is an example of such a table. In the table of FIG. 9, a plurality of Δy (Δy ₁ , Δy ₂ , ..., Δy _M ) are associated with Δt. Here, each Δt is expressed in the form of an integral multiple of T / M. T is the length of the first time interval. M represents the number of divisions in the first time interval, and is set according to, for example, the frequency of the second clock CLK2.

The conversion unit 301 in the second modification converts the input Δy into Δt with reference to the table of FIG. Since Δt corresponding to Δy is calculated in advance, division in the conversion unit 301 becomes unnecessary. Since division is an operation that is likely to be loaded, the load on the conversion unit 301 can be reduced by eliminating the need for division.

[Modification 3]
In the above-described embodiment, the NCO 26 as a timing detection device is used to determine the timing of data acquisition in the data acquisition unit 27. The third modification is an example in which the data at the time t'(= t _n + Δt) output from the NCO 26 is generated by interpolation.

FIG. 10 is a block diagram of the modified example 3. The NCO 26 of the modification 3 is configured to input the time t ′ (= t _n + Δt) to the data calculation unit 27a. The data calculation unit 27a operates in synchronization with the second clock CLK2 generated by the second clock generation unit 29. The data calculation unit 27a generates q-bit (q is an integer larger than p) data from the p-bit (p is an integer of 2 or more) data input from the data input unit 22a.

The data input unit 22a is, for example, a demodulation unit 22, which demodulates a radio signal and inputs p-bit data to the data calculation unit 27a. Here, the data input unit 22a may be configured so that p-bit data can be input, and does not necessarily have to have a function of demodulating the radio signal. For example, the data input unit 22a may be configured to A / D convert an analog signal to generate p-bit data. Further, the data input unit 22a inputs data in synchronization with, for example, the first clock CLK1, but does not necessarily have to input data in synchronization with the first clock CLK1.

The operation of the modified example 3 will be described below. The NCO 26 inputs the time t'(= t _n + Δt) to the data calculation unit 27a in synchronization with the first clock CLK1 in the same manner as in the above-described embodiment. On the other hand, the data input unit 22a inputs data to the data calculation unit 27a in synchronization with the first clock CLK1.

The data calculation unit 27a receives input of at least 2 bits of data acquired at different timings, and interpolates the data between them. Interpolation is performed by linear interpolation or interpolation using an upsampling digital filter.

FIG. 11A is an example of linear interpolation. The horizontal axis of FIG. 11A represents time. The vertical axis of FIG. 11A represents the value of the data. Further, the square plot of FIG. 11A indicates that the data is input from the data input unit 22a, and the circle plot of FIG. 11A indicates that the data is obtained by interpolation. In the linear interpolation, the data D (t _n-1 + Δt) between these two data is interpolated from the linear equation connecting the two adjacent data Dt _n-1 and Dt _n .

FIG. 11B is an example of interpolation by a digital filter. Similar to FIG. 11A, the horizontal axis of FIG. 11B represents time. The vertical axis of FIG. 11B represents the value of the data. Further, the square plot of FIG. 11B indicates that the data is input from the data input unit 22a, and the circle plot of FIG. 11B indicates that the data is obtained by interpolation. In interpolation using digital data, upsampling is performed in which data D (t _n-1 + Δt) having a value of zero is inserted between two adjacent data Dt _n-1 and Dt _n . Then, interpolation is performed by applying a low-pass filter (LPF) process to the upsampled data.

In the third modification, by interpolating the data at the time t'calculated by the NCO 26, the reproducibility of the data can be improved without shortening the data acquisition interval. Therefore, it is not necessary to operate the data input unit 22a at high speed. Further, since it is only necessary to calculate the interpolated data, the frequency of the second clock CLK2 can be slowed down as compared with the configurations of FIGS. 2 and 7 described above.

As is clear from the comparison between FIGS. 11A and 11B, the data reproducibility of the linear interpolation and the interpolation using the digital filter is higher in the interpolation using the digital filter. On the other hand, the computational load is smaller with linear interpolation. Therefore, it is desirable that the data calculation unit 27a decides whether to adopt linear interpolation or interpolation using a digital filter depending on whether the data reproducibility or the calculation load is emphasized.

Also, when obtaining only the data at time t _{n +} Delta] t by interpolation using a digital filter, the data interpolated after interpolation using a digital filter having a characteristic that does not consider Delta] t at time t _{n +} Delta] t It is possible to acquire only the data, or it is possible to directly acquire only the data at time t _n + Δt by performing interpolation using a digital filter having a characteristic considering Δt. A digital filter having both of these characteristics may be generated by the data calculation unit 27a so that it can be used properly as needed.

FIG. 12A shows the impulse response and filter coefficient of a digital filter having characteristics that do not consider Δt. Since Δt is not taken into account, a large number of filter coefficients are set.

FIG. 12B shows the relationship between the input data D _IN and the output data D _OUT when interpolated by the digital filter having the characteristics of FIG. 12A. Since Δt is not taken into account, a large amount of data is interpolated by interpolation. Data at time t _n + Δt is acquired from this.

FIG. 13A shows the impulse response and the filter coefficient of the digital filter having the characteristics considering Δt. The impulse response of FIG. 13A is shifted by Δt with respect to the impulse response of FIG. 12A. Also, only the filter coefficients corresponding to the input data are set.

FIG. 13B shows the relationship between the input data D _IN and the output data D _OUT when interpolated by the digital filter having the characteristics of FIG. 13A. Since Δt is taken into consideration, the data is interpolated only at positions deviated by Δt of each input data.

[Modification example 4]
In the above-described embodiment and its modification, the slope a is regarded as a constant when obtaining Δt from Δy. As described above, the slope a can be regarded as a constant when the range of frequencies that the NCO 26 can take is small. On the other hand, the modified example 4 is an example of obtaining Δt from Δy when the range of frequencies that the NCO 26 can take is large.

As described above, the relationship of y = at + b is established between the time t and the cumulative addition value y. Therefore, as shown in FIG. 14, the slope a can be calculated by obtaining the cumulative addition value at any two times before the threshold value y'is exceeded. That is, when the cumulative addition value at a certain time t ₁ is y ₁ and the cumulative addition value at another time t ₂ is y ₂ , the slope a can be calculated by the following (Equation 6).
a = (y _2- y ₁ ) / (t _2- t ₁ ) (Equation 6)

In such a modification 4, even if the frequency range that the NCO 26 can take is large, the time t'in which the cumulative addition value becomes the threshold value y'can be calculated accurately.

The present invention is not limited to the above-described embodiment, and can be variously modified at the implementation stage without departing from the gist thereof. In addition, each embodiment may be carried out in combination as appropriate, in which case the combined effect can be obtained. Further, the above-described embodiment includes various inventions, and various inventions can be extracted by a combination selected from a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, if the problem can be solved and the effect is obtained, the configuration in which the constituent requirements are deleted can be extracted as an invention.

1 communication system, 10 capsule endoscope, 20 receiver, 21 antenna, 22 demodulator, 22a data input unit, 23 processing unit, 24 threshold generation unit, 25 frequency adjustment value generation unit, 27 data acquisition unit, 27a data calculation Unit, 28 1st clock generation unit, 29 2nd clock generation unit, 30 display, 101 1st calculation unit, 102 detection unit, 103 Δt generation unit, 104 clock setting unit, 201 2nd calculation unit, 202 3rd calculation unit , 301 conversion unit, 302 correction unit.

Claims (8)

The first calculation unit that calculates the cumulative addition value of digital frequency adjustment values at predetermined time intervals,
A second calculation unit that calculates the difference between the cumulative addition value and the threshold value of the cumulative addition value,
A second time in which the cumulative addition value corresponds to the threshold value and exists between the predetermined time intervals is calculated based on the first time which is the time when the cumulative addition value is calculated and the difference. 3 calculation unit and
A timing detector comprising. The timing detection device according to claim 1 and
A clock setting unit that sets the second time as a clock reference timing.
A timing control device comprising. A first clock generation unit that generates a clock of a first frequency for operating the first calculation unit, the second calculation unit, and the third calculation unit.
A second clock generation unit that generates a clock having a second frequency faster than the first frequency for operating the clock setting unit, and a second clock generation unit.
The timing control device according to claim 2, further comprising. The timing detection device according to claim 1 and
A data acquisition unit that acquires the data with the second time as the reference timing for acquiring the data.
A timing control device comprising. A first clock generation unit that generates a clock of a first frequency for operating the first calculation unit, the second calculation unit, and the third calculation unit.
A second clock generation unit that generates a clock having a second frequency faster than the first frequency for operating the data acquisition unit, and a second clock generation unit.
The timing control device according to claim 4, further comprising. The timing detection device according to claim 1 and
A data calculation unit that calculates data that interpolates data between the at least two data based on the second time and at least two data that are acquired at different timings.
A timing control device comprising. The timing control device according to any one of claims 2 to 6 is provided.
A wireless signal receiving device that receives a wireless signal transmitted from a transmitting device and calculates the frequency adjustment value from the data included in the wireless signal. The timing control device according to any one of claims 2 to 6 is provided.
A device for receiving a radio signal for a capsule endoscope that receives a radio signal transmitted from the capsule endoscopy and calculates the frequency adjustment value from the data included in the radio signal.