JP2001296319A - Frequency measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency measuring apparatus, for a pulse-shaped input signal, by which a stable and precise frequency can be found even when pulse widths are different and even when a noise or the like exists. SOLUTION: Measuring pulses c to a DFD (instantaneous frequency detection) circuit 14 and output latch pulses d to a data extraction circuit 8 are generated by a timing controller 15 on the basis of timing pulses b obtained in such a way that the pulse-shaped input signal a is detected by a signal detector 13. The measuring pulses c are sufficiently narrower (high frequency) than the pulse width of the input signal a, and frequency data is measured many times during one pulse period. For example, a frequency which is nearly in the central position of input signal pulses or whose generation frequency is highest is output from the data extraction circuit 18 as output data i.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency measuring device, and more particularly to a frequency measuring device suitable for measuring the frequency of a pulse-like input signal (or received signal) in a radio wave detecting device or the like.

[0002]

2. Description of the Related Art Frequency, along with voltage and current, is one of basic electric quantities. Therefore, a frequency measuring device or circuit (hereinafter, referred to as a frequency measuring device) for accurately measuring such a frequency is required, and the applications of the frequency measuring device are diversified. Further, a frequency measuring device for measuring various signal frequencies has been proposed and put into practical use.

FIG. 7 is a block diagram showing the configuration of one conventional example of a frequency measuring device. This frequency measuring device includes a distribution circuit 1, a signal detector 2, a DFD (Direct Frequency Det
section: an instantaneous frequency detection unit 3, delay lines (delay circuits) 4, 5, and a latch circuit 6. The input signal a is input to the distribution circuit 1, and the output is input to the signal detector 2 and the DFD unit 3. The signal detector 2 outputs a timing pulse b to the delay lines 4 and 5. Delay line 4
The measurement pulse c is output to the DFD unit 3. On the other hand, the delay line 5 outputs an output latch pulse d to the latch circuit 6. The DFD unit 3 outputs the frequency data e to the latch circuit 6. Finally, the latch circuit 6 outputs the output data f.

FIG. 8 is a timing chart for explaining the operation of the conventional frequency measuring device shown in FIG. In FIG. 8, (a) is an input signal a input to the distribution circuit 1. (B) is a timing pulse b output from the signal detector 2. (C) is a delay line 4
This is the measurement pulse c output from. (E) DFD
This is the frequency data e output from the unit 3.
(D) is an output latch pulse d output from the delay line 5 to the latch circuit 6. (F)
Is output data f output from the latch circuit 6.
The timing pulse b shown in FIG. 8B has a pulse width corresponding to the input signal F1 shown in FIG. The measurement pulse c in FIG. 8C is delayed from the timing pulse b in FIG. 8B by a certain time T1. FIG.
The output latch pulse d in (d) is delayed by a certain time T2 from the measurement pulse c in FIG. 8C (accordingly, delayed by T1 + T2 from the timing pulse b in FIG. 8B). This determines the latch timing of the frequency data e shown in FIG.

Next, the operation of the conventional frequency measuring device shown in FIG. 7 will be described with reference to the timing chart of FIG.
The input signal a shown in FIG. 8A is divided into two by the distribution circuit 1, one of which is input to the signal detector 2 and the other is input to the DFD unit 3. The signal detector 2 performs envelope detection on the signal from the distribution circuit 1 to generate a timing pulse b. In the delay line 4 to which the timing pulse b is input, the timing pulse b shown in FIG. 8B is delayed by a certain time (T1) so that the frequency measurement point is located at the center of the minimum pulse width. The pulse is output to the DFD unit 3 as a measurement pulse c shown in FIG. DFD
The unit 3 calculates the conversion time (T2) from the measurement pulse c.
After waiting only for this, frequency data e shown in FIG. 8E is output. For this reason, the output latch pulse d shown in FIG. Then, the data is held in the latch circuit 6 and output as output data f shown in FIG.

[0006]

In the prior art described above, the frequency is always detected at a fixed time point from the rising point of the pulse. Therefore, the pulse width (FIG. 8)
If the width of the pulse F1 in (a) is wide, the measurement point is extremely at the leading edge, and thus cannot always be said to be the optimal measurement point. In particular, when this frequency measuring device is used in a radio wave detecting device or the like, there are the following problems during operation.
First, when a signal source generates a harmonic near a normal rise of a pulse, a frequency to be originally measured may not be measured. The reason is that in the prior art,
This is because the measurement is performed only at a fixed point from the rising point of the pulse, so that a harmonic is applied to the measurement point. Second, in the case of a signal source whose frequency changes in a time series, since the frequency measurement point is one point, it cannot be determined whether the pulse is a single frequency pulse or a pulse in which a plurality of frequency components are synthesized. . The reason is,
As described above, regardless of the length of the pulse width, the frequency is measured only at one point near the rising edge of the pulse, so that the frequency component behind the pulse cannot be measured.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a stable and high-precision frequency measuring apparatus which overcomes the above-mentioned problems in the prior art when measuring the frequency of a pulse-like input signal.

[0008]

A frequency measuring device according to the present invention is a device for measuring the frequency of a pulse-like input signal by a DFD (instantaneous frequency detection) unit, latching it in a latch circuit and outputting output data, The frequency is measured by the DFD unit a plurality of times during one pulse from the rise to the fall of the pulse-like input signal, and the optimum value is selected and output as output data.

According to a preferred embodiment of the present invention, the DFD
The unit is characterized in that frequency measurement is performed at a plurality of points based on a narrow measurement pulse of a fraction of the pulse width of the input signal or less. A timing controller for generating a measurement pulse and an output latch pulse for controlling a latch operation of the latch circuit based on the timing pulse detected from the input signal; In addition, there is provided a data extracting circuit for selecting stable frequency data at a substantially central position of the input signal pulse based on the frequency data latched by the latch circuit and outputting the selected data as output data. The frequency data measured during one pulse period of the input signal is classified for each frequency, and the frequency data having the highest frequency is output as output data. Further, the frequency data is classified by frequency and the maximum frequency is selected by a computer circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of a preferred embodiment of a frequency measuring apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

A frequency measuring device according to the present invention is a frequency measuring device for a pulse-like (or burst-like) input signal suitable for a radio wave detecting device or the like. As described above, in the past, measurement was performed assuming a signal source of one unique frequency,
The frequency was measured only at one fixed sample point. However, due to changes in radio wave propagation conditions and the increase in special signal sources, one pulse may include multiple frequency components, making it difficult to identify the original signal source. I have. Therefore, in the frequency measurement apparatus according to the present invention, the frequency measurement which has been conventionally performed only at one fixed sample point for one pulse is now performed by optimizing the measurement point and performing precise timing control. By performing the measurement at a plurality of sample points, the frequency characteristic of the signal source is more accurately analyzed.

FIG. 1 is a block diagram showing the configuration of a preferred embodiment of a frequency measuring device according to the present invention. 1 includes a distribution circuit 11, a delay line 12, a signal detector 13, a DFD unit 14, a timing controller 15, an oscillator 16, a latch circuit 17, and a data extraction circuit 18.

The distribution circuit 11 receives an input signal a and outputs an output signal to the delay line 12 and the signal detector 13. The signal detector 13 outputs the timing pulse “b” to the timing controller 15. The oscillator 16 includes the timing controller 15 and the data extraction circuit 1
8 to output a sample clock e. The timing controller 15 outputs a measurement pulse c to the DFD unit 14 and outputs an output latch pulse d to the latch circuit 17 and the data extraction circuit 18. Also, the timing controller 1
5 outputs the number h of samples in the pulse to the latch circuit 17. Further, the latch circuit 17 includes the data extraction circuit 1
8, the latched frequency data and the latched pulse sample data g are output. Then, the data extraction circuit 18 outputs the output data i.

In the frequency measuring device shown in FIG. 1, a distribution circuit 11 distributes an input signal (or a received signal) a into two,
One is output to the signal detector 13 and the other is output to the DFD unit 14 via the delay line 12. Signal detector 13
Performs envelope detection on the distributed input signal and generates a timing reference signal. The DFD unit 14 is connected to the delay line 12 and the timing controller 15, and directly converts an input signal from the delay line 12 into digital frequency data f based on the measurement pulse c. Latch circuit 1
7, the timing of the frequency data f from the DFD unit 14 is adjusted by an output latch pulse d from the timing controller 15 and held. The oscillator 16 generates a clock signal that is a reference timing signal for processing,
It is supplied to the timing controller 15 and the data extraction circuit 18. The data extraction circuit 18 extracts the optimum data g from the latch circuit 17 and outputs it.

FIG. 3 is a block diagram showing a detailed configuration of the timing controller 15 shown in FIG. The timing controller 15 includes a synchronization circuit 51, a counter circuit (1)
52, decoder circuit 53 and counter circuit (2) 54
It is composed of The synchronization circuit 51 synchronizes the timing pulse b from the signal detector 13 shown in FIG. 1 with a reference clock (sample clock) e. Counter circuit (1) 5
2 generates a count value for timing generation by the synchronized timing pulse, and generates a timing signal for external control, that is, a measurement pulse and an output latch pulse d by the decoder circuit 53. Counter circuit (2) 54
Then, the number of times of measurement within one pulse is counted and the number of samples h in the pulse is output. In the data extraction circuit 18,
The data g input from the latch circuit 17 is stored internally. Then, an extraction point is generated from the number h of samples in the pulse, and which timing data is used is determined.
The corresponding frequency data is extracted as output data i from the stored data.

Next, referring to FIGS. 1, 2 and 3,
The operation of the preferred embodiment of the frequency measuring device according to the present invention will be described in detail. The input signal a is divided into two by the distribution circuit 11, one of which is subjected to envelope detection by the signal detector 13 to generate a timing pulse b. The frequency detection uses the DFD unit 14. A signal input to the DFD unit 14 is input via the delay line 12 for time adjustment with a measurement timing. Timing pulse b
Is input to the timing controller 15 and is synchronized with the sample clock e input from the oscillator 16 by the synchronization circuit 51 of the timing controller 15. (The following processes are all performed based on the sample clock e. The sample clock e must be sufficiently short or narrow with respect to the pulse width to be processed.) Synchronized timing pulse b (see FIG. 2B) is used as an enable (ENB) signal of the counter circuit (1) 52, and is counted up by a sample clock e (see FIG. 2E). This counter output is input to the decoder circuit 53, and outputs a measurement pulse c (see FIG. 2C) to the DFD unit 14 according to the counter value. The output latch pulse d (see FIG. 2D) is output in consideration of the conversion time of the DFD unit 14. The measurement pulse c and the output latch pulse d are alternately output at high speed, and frequency measurement at a plurality of points is performed in one pulse.

The timing controller 15 counts the measurement pulse c (see FIG. 2C) generated in the timing pulse b by the counter circuit (2) 54, and counts the number of samples in the pulse. h (see FIG. 2 (h)). This signal is output latch pulse d
(See FIG. 2D) DFD unit 14 at the timing shown in FIG.
2 is held in the latch circuit 17 together with the frequency data f (see FIG. 2 (f)). The retained data is
The data is input to the data extraction circuit 18. Data extraction circuit 18
Stores the frequency data in a buffer (not shown), finds the center point of the pulse width from the number of samples h in the pulse (see FIG. 2 (h)), extracts the target data from the buffer,
Output as output data i (see FIG. 2 (i)). FIG.
In the case of the timing chart shown in (1), the number of samples in a pulse h = 7. Therefore, the optimal measurement point is the fourth measurement point near the center of the pulse width, for example, and the frequency of F4 is output from the data extraction circuit 18 as final output data i (see FIG. 2 (i)).

[0018]

Next, another embodiment of the frequency measuring apparatus according to the present invention will be described with reference to FIGS. Note that, for convenience, the same reference numerals are used for components corresponding to the above-described preferred embodiment. FIG. 4 is a block diagram showing a configuration of another embodiment of the frequency measuring device according to the present invention. 4 includes a distribution circuit 11, a delay line 12, a signal detector 13, a DFD unit 14, a timing controller 15,
Oscillator 16, latch circuit 17, and computer circuit 2
It is composed of 0. In other words, the frequency measurement device shown in FIG. 4 is a data extraction circuit 1 of the frequency measurement device shown in FIG.
8 is replaced with a computer circuit 20.
Therefore, the following description focuses on this difference and avoids redundant description of the same components.

The computer circuit 20 includes a memory (storage device), a computer, and a peripheral control circuit. The measured frequency data can be analyzed in detail by software processing. FIG. 5 is a system diagram of software processing executed by the computer circuit 20. That is, the storage unit 21, the frequency data classification 22, the n (plural) detection circuits 23a to 23n, and the maximum frequency detection 24
And the functions of the selector 25. The frequency data and the number of samples in the pulse input from the latch circuit 17 shown in FIG. The fetched data is classified for each frequency by the frequency data classification 22, and the number of times of detection is recorded in the number of detections 23a to 23n. The maximum frequency detection 24 searches the result for the most frequently measured frequency in the pulse. Then, a switching signal is output to the selector 25. here,
If one wave with the maximum frequency cannot be specified, a status code is output according to the situation, and the situation of the processing result is notified to the external device. The selector 25 outputs frequency data corresponding to the selected switching signal as output data. With this method, even if the frequency fluctuates partially due to an external signal or the like inside the pulse, the frequency can be specified with a high probability.

FIG. 6 is a timing chart showing the operation of the frequency measuring device shown in FIG. As shown in FIG. 6, consider a case where extraneous waves F1 and F3 are superimposed on the input signal F2. In this case, since F2 was detected four times during seven measurements, the original signal, F2
Can be detected. The other points are similar to the timing chart of FIG. 2 described above, and thus the detailed description is omitted.

The configuration and operation of the embodiment of the frequency measuring apparatus according to the present invention have been described above in detail. However, it should be noted that such exemplary embodiments are merely examples of the present invention and do not limit the present invention in any way. It will be readily apparent to those skilled in the art that various modifications and changes can be made in accordance with the particular application without departing from the spirit of the invention.

[0022]

As apparent from the above description, the frequency measuring apparatus of the present invention has the following remarkable practical effects. First, since the frequency can always be measured at a point where the frequency in the pulse is stable, regardless of the pulse width, the frequency measurement accuracy can be improved.
The reason is that a timing controller is provided, frequency measurement is performed multiple times within one pulse, and the measurement result near the center point of the pulse whose frequency is most stable in time is extracted from the data extraction circuit, and the output data is output. This is because it is possible to output as

Second, since frequency measurement is performed a plurality of times within one pulse, it is possible to cope with the analysis of a signal whose frequency fluctuates within a pulse. The reason is that a plurality of frequency data measured a number of times within one pulse can be classified by occurrence frequency by computer processing or the like, so that the frequency distribution can be grasped. As a result, it is possible to output the most frequently occurring measurement frequency data as target measurement frequency data.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a preferred embodiment of a frequency measuring device according to the present invention.

FIG. 2 is a timing chart showing the operation of each unit constituting the frequency measuring device of FIG.

FIG. 3 is a block diagram illustrating a detailed configuration of a timing controller included in the frequency measurement device illustrated in FIG. 1;

FIG. 4 is a block diagram showing a configuration of another embodiment of the frequency measuring device according to the present invention.

5 is a functional block diagram of a computer circuit included in the frequency measurement device shown in FIG.

FIG. 6 is a timing chart showing the operation of each unit constituting the frequency measurement device shown in FIG.

FIG. 7 is a block diagram illustrating a configuration of a conventional frequency measurement device.

8 is a timing chart showing the operation of each unit constituting the conventional frequency measurement device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Distribution circuit 12 Delay line (delay circuit) 13 Signal detector 14 DFD unit 15 Timing controller 16 Oscillator 17 Latch circuit 18 Data extraction circuit 20 Computer circuit

Claims (6)

[Claims] 1. A frequency measuring apparatus for measuring the frequency of a pulse-like input signal by a DFD (instantaneous frequency detection) unit and outputting the output data by latching it in a latch circuit, wherein the pulse-like input signal has a rising edge to a falling edge. A frequency measuring unit that measures a frequency a plurality of times during one pulse of the above, and selects an optimum value to output as the output data. 2. The frequency measurement according to claim 1, wherein the DFD unit measures the frequency at a plurality of points based on a narrow measurement pulse of a fraction of the pulse width of the input signal. apparatus. 3. A timing controller according to claim 1, further comprising a timing controller for generating the measurement pulse and an output latch pulse for controlling a latch operation of the latch circuit based on a timing pulse detected from the input signal. The frequency measurement device as described. 4. A data extracting circuit according to claim 1, further comprising a data extracting circuit for selectively outputting output data at a substantially central position of said input signal pulse based on frequency data latched by said latch circuit. 3. The frequency measuring device according to 3. 5. The method according to claim 1, wherein frequency data measured during one pulse period of the input signal is classified for each frequency, and frequency data having a maximum frequency is output as output data. Frequency measuring device. 6. The frequency measuring apparatus according to claim 5, wherein the classification of the frequency data for each frequency and the selection of the maximum frequency are performed by a computer circuit.