JPH10319058A - Frequency measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the frequency measurement precision to short pulse modulation signal by distributing an input signal to a plurality of channels, and delaying the proximity value between the distributed channels by a delay value lower than a specified value. SOLUTION: A first distributor 16 distributes an input signal to two channels, and second distributors 1, 1 further halve the distributed input signal every distributed channels. One of the halved signals distributed by the second distributor 1 is delayed with a delay value not less than 6 times the proximity value between the channels by delay lines 61, 62 of frequency discriminators 17a, 17b. Phase detectors 14a1, 14b1, 14a2, 14b2 phase-detect the other output and delayed output of the second distributor 1 to detect the phase angle every channel. A phase angle frequency converting part 30a having a phase diaphragm determines the frequency from the phase angle of each channel. Thus, the frequency precision is enhanced, and a wide frequency range causing no ambiguity can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ECM (Ele)
tronic Counter Measure),
ESM (Electronic Support Me)
IFM (InstantaneousFrequency) used as a frequency measuring device in an assure) system
cy Measurement) receiver.

[0002]

2. Description of the Related Art FIG. 14 shows, for example, "Microwave Receiver for Electronic Warfare" by Joan Willy, written by James Bao Tsui.
And Sons, Inc. 1986 ("Microwave"
Receivers With Electronic
Warrefare Applications ”b
y James Bao-Yen Tui 1986)
1 is a block diagram of a conventional IFM receiver described in FIG. FIG. 16 shows a frequency discrimination circuit of the IFM receiver. In FIG. 16, reference numeral 1 denotes an in-phase power two-way divider, and 2 denotes an in-phase power two-way input having one end output of the in-phase power two-way divider 1 as an input.
The dividers 3, 4, 5, and 90 are 90-degree directional couplers, 106 is a delay line, 7, 8, 9, and 10 are square detectors, 11 and 12 are differential amplifiers, 13 is a 50Ω terminator, and 114 is 2 A phase detector 30 detects the phase difference between the two input signals a1 and b1, and an encoder 30 calculates the frequency from the two output video signals c1 and d1 of the phase detector 14. In FIG. 14, reference numeral 16 denotes a first divider, 117a denotes a first frequency discriminating circuit, 117b denotes a second frequency discriminating circuit, 117c denotes a third frequency discriminating circuit, and 117d denotes a fourth frequency discriminating circuit. And has delay lines with delay times τ1, τ2, τ3, and τ4, respectively. Reference numeral 30 denotes an encoder for calculating a frequency. Normally, the relationship between these delay times is based on τ1 and the others are powers of two. For example, τ2 = 2τ
1, τ3 = 4τ1, and τ4 = 8τ1. FIG. 15 is a characteristic diagram in which the encoder 30 determines the frequency from the phase angle from each of the frequency discriminating circuits 117a to 117d when the delay time is set.

Next, the operation will be described. Input signal Pi
n is a pulse modulation wave, and the pulse width is T and the carrier frequency is f. The delay line 6 has a propagation delay time from an output of the in-phase power splitter 1 to an input of the in-phase power splitter 2 and a delay time from another output of the in-phase power splitter 1 to an input of the 90-degree directional coupler 3. It is assumed that the delay time is such that the difference from the propagation delay time is τ. Assuming that the input signal of the input signal a1 of the in-phase power splitter 2 is A and the signal of the input signal b1 of the 90-degree directional coupler 3 is B, there is a relation of B = Aexp (jθ). Here, θ = 2πfτ. Also, the signal e
Levels S1, S2, S3, S4 of 1, f1, g1, h1
S1 = (A / 2) [1 + exp {j (θ−π)}] S2 = (A / 2) [exp (−jπ / 2) + exp {j (θ−π / 2)}] S3 = (A / 2) [1 + exp {j (θ−π / 2)}] S4 = (A / 2) [exp {j (−π / 2)} + exp (jθ)] (1)

The output signals i1, j1, k1, and l1 of the square detectors 7, 8, 9, and 10 are represented by V1, V2, and V1, respectively.
3, V4 to the ^{V1 = S1 · S1 * (A} 2/4) (1-cosθ) V2 = S2 · S2 * (A 2/4) (1 + cosθ) V3 = S3 · S3 * (A 2/4) ( 1 + sinθ) V4 = S4 · S4 * (a 2/4) (1-sinθ) to become (2). Further, the output signals c of the differential amplifiers 11 and 12
If the output signal levels of 1, c2 are VI and VQ, then VI = kcos θ VQ = ksin θ (3) Here, k is a gain constant. Therefore, f = (1 / 2π) (1 / τ) θ (5) from θ = 2πfτ = tan ⁻¹ (VQ / VI) (4), and the frequency is obtained from the angle between VI and VQ.

[0005] The encoder 30 calculates a frequency f from VI and VQ. By the way, generally, the configuration of an IFM receiver is used by combining a plurality of frequency discriminators having different delay times of the delay line as shown in FIG. That is, in each frequency discriminator, the phase difference obtained by the phase detector is θ
₁ θ ₂ θ ₃ θ ₄ gives θ ₁ = 2πfτ ₁ -2N ₁ a _{π θ 2 = 2πfτ 2 -2N 2} π θ 3 = 2πfτ 3 -2N 3 π θ 4 = 2πfτ 4 -2N 4 π (6). Phase angle θ ₁ obtained by the phase detector of each frequency discrimination circuit θ ₂ θ ₃ θ ₄ can only take on values of 0 to 2π, and ambiguity (a situation where the frequency cannot be uniquely specified from the phase detector output) occurs. For example, when τ1 to τ4 are in the above relationship, θ ₁ θ ₂ θ ₃ θ ₄
Corresponds to the thick dotted line, dotted line, thick solid line, and solid line in the characteristic diagram shown in FIG.

In the above, the relationship between the respective delay times is represented by τ ₁ <
Since τ ₂ <τ ₃ <τ ₄ , the change of the phase difference with respect to the change of the frequency is the fourth frequency discrimination circuit 1 having the delay time τ ₄ .
7d is a first frequency discriminating circuit 17 having a delay time τ ₁
Therefore, the frequency discrimination circuit 17d has a small frequency measurement error caused by a certain phase measurement error, and the frequency measurement accuracy is good. In other words, the slope in FIG. 15 becomes steep, and the fluctuation of the phase angle caused by the added noise and the error of the characteristics of the phase detector affects the frequency determination only to a small extent. Conversely, the first frequency discrimination circuit 17a
Since the delay time is small, the slope in FIG. 15 becomes gentle, and the frequency measurement accuracy is not good. On the other hand, however, the first frequency discriminating circuit 17a can broaden a frequency range that can be uniquely measured as compared with the fourth frequency discriminating circuit 17d indicated by a solid line, as indicated by the thick dotted line in FIG. In an actual frequency measuring device, a desired frequency measurement accuracy is obtained by the fourth frequency discriminating circuit 17d, and the first, second, and third frequency discriminating circuits 17a,
17b and 17c are used to remove ambiguity generated in the fourth frequency discrimination circuit 17d. That is, the ambiguity of the fourth frequency discriminating circuit 17d is changed by the third frequency discriminating circuit 17c, and the ambiguity of the third frequency discriminating circuit 17c is changed by the second frequency discriminating circuit 1.
At 7b, the ambiguity of the second frequency discriminating circuit 17b is sequentially removed by the first frequency discriminating circuit 17a. The first frequency discriminating circuit 17a is set so that ambiguity does not occur in the target frequency band.

[0007]

Since the conventional frequency measuring apparatus is constructed as described above, the frequency discriminating circuit needs to be 8 to 64 times as large as the measured frequency range in order to obtain the frequency measuring accuracy. It is necessary to use a delay line having a large delay time. That is, on the contrary, there is a problem that a desired frequency measurement accuracy cannot be obtained for a signal having a pulse width equal to or less than the longest delay time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to obtain a frequency measuring device having high measurement accuracy for a short pulse modulation signal.

[0009]

A frequency measuring apparatus according to the present invention comprises a first divider for dividing an input signal into a plurality of channels, and further dividing the input signal into two for each of the divided channels. A second divider that delays one of the binary signals distributed by the second divider for each channel, and delays the proximity value between channels by a delay value of 6 times or less; And a phase detector for phase-detecting the other output of the second divider and the output of the delay means to obtain a phase angle for each channel. Phase angle frequency conversion means having a phase diagram table for determining a frequency from a phase angle of each output channel.

Further, the number of channels is two, and two frequency discriminating means are provided as a measuring device.

Further, the number of channels is three, and three frequency discriminating means are provided as a measuring device.

Further, the ratio of the delay time of the delay means of each channel is set to a value such that the phase angle relationship between the channels is represented at substantially equal intervals on the phase diagram.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. In order to determine the frequency with a short delay time for the measurement frequency range, concretely, the setting of the delay time is the same as in the past, the frequency discrimination circuit for eliminating ambiguity and the frequency discrimination for improving accuracy The difference between the delay time and the circuit is divided by a different factor, and the ratio of the delay times is no longer a power of two. All frequency discrimination circuits have the same configuration.
In other words, FIG.
, The relationship between the phase angle θ1 and the other phase angles θ is the same as that in FIG. 2 except for the bold dotted line, and the other oblique lines represent the relationship with the pair θ1, and have an eight-fold slope in the diagram. While the frequency is determined using up to θ4, the frequency is determined by the phase angle θ of a smaller number of outputs of the frequency discriminator having a similar slope, that is, having no delay time, as described below, . For this purpose, for the phase angle frequency conversion, a frequency determined in advance from the relationship between the phase angles corresponding to different delay times is stored as a phase diagram table, and the phase angle of each frequency discrimination circuit output is input and the corresponding frequency is determined. Confirm.

The simplest frequency measuring apparatus using a two-channel frequency discriminating circuit based on the above concept will be described. FIG. 1 is a diagram showing a configuration of a frequency measuring apparatus according to the present invention in a first embodiment. In FIG. 1, 16 is a first power divider, 1 is a second power divider, 61 is a delay line with a delay time A ₁ τ, 62 is a delay line with a delay time A ₂ τ, 1
4a1 is a first phase detector, 14a2 is a second phase detector, 14b1 is a first phase angle calculator, 14b2 is a second phase angle calculator, 17a is a frequency discrimination circuit of the first channel, 17b Are frequency discriminating circuits of the second channel, 3
Reference numeral 0 denotes a phase angle frequency conversion unit having a phase diagram table in which a corresponding frequency is set using the output φ1 of the first phase angle calculator 14b1 and the output φ2 of the second phase angle calculator 14b2 as addresses. The ratio between the delay time A ₂ tau delay time A ₁ tau and the delay line 62 of the delay line 61 is not an integer, and 3 are set to the following values.

FIG. 2 shows that the ratio between the delay times τ ₁ and τ ₂ is 40:
7 is a phase diagram for case No. 7. This is stored in a ROM or the like corresponding to the frequency. According to this setting, the output of the first phase angle calculator 14b1 is φ1,
Assuming that the output of the phase angle calculator 14b2 is φ2, the input frequency f corresponds to one point on the φ1-φ2 plane. The locus on the φ1-φ2 plane when the frequency is changed is a straight line. The operation of the frequency measuring device having this configuration is as follows. In FIG. 1, except for the delay time, the basic operation of the frequency discriminating circuits 17a and 17b is a general operation and does not require any particular explanation. Φ is determined from VI and VQ by the phase angle calculator 14b. Each frequency discrimination circuit 17a,
Φ1 and φ2 are obtained as outputs of 17b. The phase angle frequency conversion unit 30 receives these as inputs, refers to the phase diagram table of FIG. 2, and knows and outputs the frequency stored in the ROM. When the frequency is changed, the input frequency can be determined and no ambiguity occurs until the locus overlaps again. As long as the longest delay line is the same as that of the conventional device, a wider range where ambiguity does not occur can be ensured, and on the other hand, the delay time required to obtain the same frequency accuracy can be shortened, and therefore shorter pulse modulation can be achieved. The carrier frequency can be measured for the signal.

In the above embodiment, by setting the ratio of the delay time of the delay line to a prime number ratio other than 40: 7, the trajectory for the frequency change in the φ1-φ2 plane is a fixed distance from the adjacent trajectory. So that As a result, it is possible to secure a margin against so-called “skip”, which is erroneously recognized as an adjacent trajectory due to deviation from the ideal characteristics of the device and noise. The delay time ratio of the delay line is 2: 3,
Phase diagrams for 3: 5, 5: 7 are shown in FIGS. 3, 4, and 5. FIG.

Further, in the above embodiment, even if the ratio of the delay times of the delay lines is set to the irrational ratio, the trajectory for the frequency change in the φ1-φ2 plane is at a constant interval from the adjacent trajectory. Can be. FIG. 6 shows a phase diagram when the ratio of the delay times of the delay lines is √2: √3.

Further, in the above embodiment, even if the delay time ratio of the delay line is set to a circulating decimal which is a ratio of rational numbers, the trajectory for the frequency change in the φ1-φ2 plane is constant with the adjacent trajectory. It can be set to the interval. FIGS. 7 and 8 show phase diagrams when the delay line ratios of the delay lines are 7:11 and 5:11, respectively.

Embodiment 2 In the above embodiment, the frequency information is represented by two pieces of phase information. As shown in FIG. 9, three frequency discriminating circuits having different delay times are used.
When the input frequency is made to correspond to one point in the φ1-φ2-φ3 space, a wider range in which ambiguity does not occur can be secured. On the other hand, the delay time required to obtain the same frequency accuracy can be further reduced. Therefore, the carrier frequency can be measured for a shorter pulse modulation signal.

FIG. 9 is a block diagram of the frequency measuring apparatus according to the present embodiment. In the figure, 14a3 is a third phase detector, 14b3 is a third phase angle calculator, 63 is a delay line with a delay time A ₃ τ, and 17c is a third channel frequency discriminator. Reference numeral 30b denotes a phase angle frequency conversion unit that stores a phase diagram table in which correspondence between three phase angles and frequencies is determined. FIG. 10 is a diagram illustrating an example of a phase diagram stored in the phase angle frequency conversion unit 30b according to the present embodiment, and illustrates a case where the delay time ratio of three channels is 3: 5: 7. Note that φ1−φ2
Displaying the trajectory on the three-dimensional section of −φ3 is complicated, and is shown on a plane.

In the above-described embodiment, three frequency discriminating circuits having different delay times may be configured so that the ratio of each delay time is a prime number ratio. Even when the input frequency is changed, the trajectory in the φ1-φ2-φ3 space can have a constant distance from the adjacent trajectory. As a result, it is possible to secure a margin against so-called “skip”, which is erroneously recognized as an adjacent trajectory due to deviation from the ideal characteristics of the device and noise. Displaying the trajectory in the three-dimensional space of φ1-φ2-φ3 becomes complicated, so
FIGS. 11 (a) and 11 (b) show the case of projecting on the 1-φ2 plane and on the φ1-φ3 plane.

Further, in the above embodiment, even if the frequency discriminating circuits having different delay times from each other are constituted by three and the ratio of each delay time is set to be a circulating minority which is a ratio of rational numbers, the input frequency is not changed. When the distance is changed, the trajectory in the φ1-φ2-φ3 space can be made to have a constant distance from the adjacent trajectory. FIGS. 12 (a) and 12 (b) show the case of projecting on the φ1-φ2 plane and φ1-φ3 plane, respectively, when the delay time ratio is 5: 7: 11.

Embodiment 3 FIG. In the above embodiment, the frequency information is represented by two or three pieces of phase information. However, as shown in FIG. 13, frequency discriminating circuits having different delay times are constituted by N channels, and .. Φ3 correspond to one point in the N-dimensional space, it is possible to further secure a wide range in which ambiguity does not occur, and on the other hand, to obtain the same frequency accuracy. The required delay time can be further reduced.

[0024]

As described above, according to the present invention, a small frequency discriminator is used, and the ratio of the delay time of the delay line of each frequency discriminator is set to an appropriate ratio (prime number ratio, irrational number Ratio, rational number ratio) and frequency information is obtained from a value mapped to a multi-dimensional signal space, so that there is an effect that the frequency accuracy is improved and a wide frequency range where ambiguity does not occur can be secured. Since the delay line used in the frequency discriminator can be shortened in this manner, there is an effect that the carrier frequency of a pulse modulation signal having a short pulse width can also be measured.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a frequency measurement device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a phase diagram table included in the phase angle frequency converter of FIG. 1;

FIG. 3 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 4 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 5 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 6 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 7 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 8 is a diagram showing an example of another phase diagram table of FIG. 1;

FIG. 9 is a configuration block diagram of a frequency measurement device according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating an example of a phase diagram table included in the phase angle frequency converter of FIG. 9;

FIG. 11 is a diagram showing an example of another phase diagram table of FIG. 9;

FIG. 12 is a diagram showing an example of another phase diagram table of FIG. 9;

FIG. 13 is a configuration block diagram of a frequency measurement device according to a third embodiment of the present invention.

FIG. 14 is a configuration block diagram of a conventional frequency measurement device.

FIG. 15 is a phase angle frequency characteristic diagram of a conventional encoder.

FIG. 16 is a configuration block diagram of a conventional frequency discriminator.

[Explanation of symbols]

1 in-phase power divider, 2 in-phase power divider, 3, 4,
5. 90-degree directional coupler, 61, 62, 63, 6N delay line, 7, 8, 9, 10 square detector, 11, 12 differential amplifier, 13 terminator, 14a1, 14a2, 14a
3, 14aN, 14b1, 14b2, 14b3, 14b
N phase angle calculator, 15 frequency encoder, 16 distributor, 17a, 17b, 17c, 17a2, 17aN
Frequency discriminator, 30a, 30b, 30c Phase angle frequency converter.

Claims (4)

[Claims] A first splitter for splitting an input signal into a plurality of channels; a second splitter for splitting the split input signal into two for each of the split channels; and a second splitter for splitting the input signal. Delay means for delaying one of the binary signals distributed by the divider with a delay value which is different for each channel and the proximity value between the channels is 6 times or less, the other output of the second distributor and the output of the delay means And a phase detector that obtains a phase angle for each channel by performing phase detection on the respective channels. The phase determining the frequency from the phase angle of each channel of the output of the frequency discriminator provided for each channel is provided. A frequency measuring device comprising: a phase angle frequency converting means having a diagram table. 2. The frequency measuring apparatus according to claim 1, wherein the number of channels is two, and two frequency discriminating means are provided. 3. The frequency measuring apparatus according to claim 1, wherein the number of channels is three, and three frequency discriminating means are provided. 4. The method according to claim 1, wherein the delay time ratio of the delay means of each channel is set to a value such that the phase angle relationship between the channels is represented at substantially equal intervals on the phase diagram. The frequency measuring device according to claim 1, wherein