JP2007163179A - Detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detector capable of highly precisely detecting the frequency component of input signal. <P>SOLUTION: The detector characteristically includes: a reference oscillator for outputting reference clock; a first local oscillator for outputting a first local signal having the frequency of the first local frequency which is the product of the reference clock and the first dividing ratio of the first divider by dividing the outputting the first local signal with the first divider capable of setting with unit of under decimal point; a first mixer for outputting the first mixed signal which is mixed with input signal and the first local signal; the second local oscillator for outputting the second local signal of previously determined second local frequency from the first local signal; the second mixer for outputting the second mixed signal mixed with the first mixed signal and the second local signal; and the detector part for detecting the frequency component of input signal corresponding to the first local frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a detector. In particular, the present invention relates to a detector that detects a frequency component contained in an input signal.

  2. Description of the Related Art Conventionally, a superheterodyne spectrum analyzer has been known as an apparatus for performing signal spectrum analysis (see, for example, Patent Document 1). The superheterodyne spectrum analyzer changes the frequency to be detected by controlling the oscillation frequency of the first-stage local oscillator. Therefore, the conventional spectrum analyzer can detect the spectrum distribution of the input signal in the frequency range by sweeping and controlling the oscillation frequency of the first-stage oscillator in an arbitrary range.

  An oscillator that generates a second clock obtained by dividing the first clock by a programmable digital frequency divider has been proposed (for example, Patent Document 2). Further, a PLL circuit having a fractional-N frequency divider (see, for example, Patent Document 3) has been proposed. The PLL circuit using the fractional-N frequency divider can set the output frequency to a multiple of the precision below the decimal point of the input frequency.

JP 2001-272425 A US Pat. No. 6,708,026 JP 2004-349735 A

  By the way, in a spectrum analyzer, when a PLL circuit having a fractional-N frequency divider is applied as a first-stage local oscillator, the oscillation frequency changes in detail, so that the frequency to be detected can be controlled in detail. However, a PLL circuit having a fractional-N frequency divider generates spurious and phase noise caused by switching of the frequency division ratio. For this reason, the spectrum analyzer to which the fractional-N frequency divider is applied as the first-stage local oscillator deteriorates the detection accuracy due to spurious and phase noise.

  Then, this invention aims at providing the detector which can solve said subject. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous specific examples of the present invention.

  According to the first aspect of the present invention, a detector for detecting an input signal is a reference oscillator that outputs a reference clock (fref), and a first local signal to be output is set with a division ratio in units of decimals. A first local frequency (flo1) obtained by multiplying the reference clock by the first frequency division ratio in the first frequency divider by dividing the frequency by the first frequency divider possible and adjusting the phase with the reference clock. A first local oscillator that outputs a first local signal; a first mixer that outputs a first mixed signal obtained by mixing the input signal and the first local signal; and a second local that is predetermined based on the first local signal. A second local oscillator that outputs a second local signal having a frequency (flo2); a second mixer that outputs a second mixed signal obtained by mixing the first mixed signal and the second local signal; Based on the second mixed signal is output in accordance with a local frequency, to provide a detector and a detector for detecting the frequency component of the input signal corresponding to the first local frequency.

  The second local oscillator adjusts the phase between the second divided signal obtained by dividing the second local signal by the second divider and the first divided signal output by the first divider, A second local signal having a second local frequency (flo2) obtained by multiplying the first frequency division signal by the second frequency division ratio in the second frequency divider may be output. The first frequency divider may be a fractional frequency divider. The first local frequency may be greater than the second local frequency and less than twice the second local frequency.

  The detector adjusts the phase between the third divided signal obtained by dividing the third local signal to be output by the third divider and the first divided signal, so that the first divided signal is divided into the third divided signal. A third local oscillator that outputs a third local signal having a third local frequency (flo3) multiplied by a third frequency division ratio in the frequency divider, and a third mixed signal obtained by mixing the second mixed signal and the third local signal. And a third mixer for outputting, and the detection unit may detect the spectrum of the input signal based on the third mixed signal output according to the first local frequency.

  The detector adjusts the phase between the third frequency-divided signal obtained by frequency-dividing the third local signal to be output by the third frequency divider and the second frequency-divided signal, so that the second frequency-divided signal is divided into the third frequency-divided signal. A third local oscillator that outputs a third local signal having a third local frequency (flo3) multiplied by a third frequency division ratio in the frequency divider, and a third mixed signal obtained by mixing the second mixed signal and the third local signal. And a third mixer for outputting, and the detection unit may detect the spectrum of the input signal based on the third mixed signal output according to the first local frequency.

  The detector functions as a spectrum analyzer for measuring the spectrum of the input signal, and the detector is configured to detect the first mixed signal output from the first mixed signal output according to the first local frequency. A spectrum of a frequency corresponding to the local frequency may be detected.

  According to a second aspect of the present invention, there is provided a detection method for detecting an input signal, wherein a reference oscillation stage for outputting a reference clock (fref) and a first local signal to be output are divided by a unit of less than 1 time. The first local frequency (flo1) obtained by multiplying the reference clock by the first frequency division ratio in the first frequency divider by dividing the frequency by the first frequency divider that can be set and adjusting the phase with the reference clock. And a first mixer stage for outputting a first mixed signal obtained by mixing the input signal and the first local signal, and a first local signal based on the first local signal. A second local oscillation stage for outputting a second local signal having a second local frequency (flo2), and a second mixer for outputting a second mixed signal obtained by mixing the first mixed signal and the second local signal. And over steps, on the basis of the second mixed signal is output in accordance with the first local frequency, to provide a detection method and a detection step of detecting a frequency component of the input signal corresponding to the first local frequency.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  According to the present invention, a frequency component included in an input signal can be detected with high accuracy.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 shows a configuration of a spectrum analyzer 10 according to the present embodiment. The spectrum analyzer 10 is an example of the detector of the present invention, and measures the spectrum of the input signal with high accuracy by the superheterodyne method. For example, the spectrum analyzer 10 sweeps an input signal in a range of 0 (Hz) to A (GHz) and detects the amplitude and / or phase of each frequency (frf) component. A is a positive value.

The spectrum analyzer 10 includes a reference oscillator 11, a first local oscillator 12, a first mixer 13, a first BPF 14, a second local oscillator 15, a second mixer 16, a second BPF 17, and a third local oscillator 18. The third mixer 19, the third BPF 20, the detection unit 21, the output unit 22, and the setting unit 23 are provided.
The reference oscillator 11 generates a reference clock having a predetermined frequency (fref).

  The first local oscillator 12 is a first local frequency obtained by multiplying the frequency (fref) of the reference clock by a first frequency division ratio (N. F and N. F are N is an integer part and F is a decimal part). A first local signal having a sine wave signal of (flo1 = fref × NF) is output. Further, the first local oscillator 12 divides the output first local signal by the first frequency division ratio (NF) and adjusts the phase with the reference clock.

  For example, the first local oscillator 12 includes a first VCO (Voltage Controlled Oscillators) 31, 1 / N. A PLL (Phase Locked Loop) circuit including an F frequency divider 32, a first phase comparator 33, and a first LPF (Low Pass Filter) 34 may be used. The first VCO 31 outputs a first local signal whose oscillation frequency varies according to the input voltage from the first LPF 34.

  1 / N. The F frequency divider 32 is a frequency divider capable of setting a frequency division ratio in units after the decimal point, and outputs the first local signal to the first frequency division ratio (NF) expressed in units after the decimal point. ). 1 / N. The F divider 32 divides the frequency by a division ratio in units of decimal places (that is, a division ratio having a unit of less than 1) by switching a plurality of division ratios of different integers to a predetermined period, for example. It may be a fractional frequency divider. Note that in this specification, a frequency divider having a frequency dividing ratio X (X is a positive value) is a portion that outputs a clock signal having a frequency (f / X) when a signal having a frequency f is input. Means a divider. 1 / N. The F divider 32 supplies the divided signal to the first phase comparator 33 and the second local oscillator 15 as a first divided signal.

  The first phase comparator 33 detects the phase error amount by comparing the phase of the reference clock and the first divided signal. The first LPF 34 supplies a voltage obtained by averaging the phase error amount detected by the first phase comparator 33 to the first VCO 31. Then, the first VCO 31 changes the first local frequency (flo1) of the first local signal according to the input voltage. That is, the first VCO 31 changes the first local frequency (flo1) so that the first frequency-divided signal and the reference clock are phase-synchronized. Thus, the first local oscillator 12 can adjust the phase of the first local signal with the reference clock.

  The first mixer 13 multiplies the input signal and the first local signal, and adds the signal component included in each frequency of the input signal by the first local frequency (flo1) plus the first local frequency. A signal shifted in frequency to the minus side by the frequency (flo1) is output. The first BPF 14 is a band-pass filter whose center frequency is set to B (GHz), and passes a signal component in a predetermined band centered on B (GHz) in the output signal of the first mixer 13. In this case, B is a positive value larger than A. The first BPF 14 outputs the passed signal as a first mixed signal obtained by mixing the input signal and the first local signal.

  Here, the first local oscillator 12 determines the first local frequency (flo1) of the first local signal to be output in accordance with the first frequency division ratio (NF) being controlled by the setting unit 23. It is changed within the range of (GHz) to A + B (GHz). The setting unit 23 multiplies the input signal and the first local signal by the first mixer 13, so that the signal component included in the detection target frequency (frf) of the input signal is the center frequency of the first BPF 14. The first local frequency (flo1) of the first local signal is set so that the frequency is shifted to (GHz). That is, the setting unit 23 controls the first frequency division ratio (NF) so that the first local frequency (flo1) becomes (frf + B (GHz)).

  Specifically, if a signal component included in 0 (Hz) of the input signal is detected, the setting unit 23 sets the first local frequency (flo1) to be B (GHz). A frequency division ratio (NF) is set. If the signal component included in A (Hz) of the input signal is detected, the setting unit 23 sets the first frequency division ratio so that the first local frequency (flo1) becomes B + A (GHz). (NF) is set.

According to the spectrum analyzer 10, the signal component included in the detection target frequency (frf) of the input signal is set to the fixed frequency (B (GHz)) by controlling the first local frequency (fol1) as described above. Since the frequency can be shifted, the first BPF 14 can have a simple filter configuration in which the pass frequency band is fixed.
The spectrum analyzer 10 may control the center frequency of the first BPF 14 to be A + B (GHz) and the setting unit 23 to set the first local frequency (flo1) to (A + B (GHz) −frf).

  The second local oscillator 15 outputs a second local signal having a sine wave signal having a predetermined second local frequency (flo2) based on the first local signal. Specifically, the second local oscillator 15 is configured to multiply the reference clock (fref) by a predetermined second frequency division ratio (M: M is an integer equal to or greater than 2). flo2) is output. Further, the second local oscillator 15 divides the output second local signal by the second frequency division ratio (M) and adjusts the phase with the first frequency divided signal.

  In this case, flo2 is a value different from flo1, but is set to a relatively close value. More specifically, in the spectrum analyzer 10 of the superheterodyne method, down conversion to a lower frequency is achieved when f1o1 and flo2 are very close to each other and the frequency difference between flo1 and flo2 is small. Since it becomes possible, it is desirable that 1 <(flo1 / flo2) <2. In other words, the first local frequency (flo1) is desirably larger than the second local frequency (flo2) and less than twice the second local frequency (flo2).

  For example, the second local oscillator 15 may be a PLL circuit having a second VCO 41, a 1 / M frequency divider 42, a second phase comparator 43, and a second LPF 44. The second VCO 41 outputs a second local signal whose oscillation frequency varies according to the input voltage. The 1 / M frequency divider 42 divides the output second local signal by a fixed second frequency division ratio M, and supplies it to the second phase comparator 43 as a second frequency division signal.

The second phase comparator 43 detects the phase error amount by comparing the phase of the first divided signal and the second divided signal. The second LPF 44 supplies a voltage obtained by averaging the phase error amount detected by the second phase comparator 43 to the second VCO 41. Then, the second VCO 41 changes the second local frequency (flo2) of the second local signal according to the input voltage. That is, the second VCO 41 changes the second local frequency (flo2) so that the second divided signal and the first divided signal are phase-synchronized. Accordingly, the second local oscillator 15 can adjust the phase of the second local signal with the first frequency-divided signal.
The second mixer 16 multiplies the first mixed signal and the second local signal, and adds the signal component included in each frequency of the first mixed signal by the second local frequency (flo2), and , A signal shifted to the minus side by the second local frequency (flo2) is output. The second BPF 17 is a bandpass filter whose center frequency is set to C (MHz) (= B (GHz) −flo2), and a predetermined band centered on C (MHz) in the output signal of the second mixer 16. Pass through the signal component. The second BPF 17 outputs the passed signal as a second mixed signal obtained by mixing the first mixed signal and the second local signal.

  Here, the frequency (fref ′) of the first frequency-divided signal coincides with the frequency (fref) of the reference clock on average when the synchronization processing by the first local oscillator 12 is stabilized. Therefore, the second local oscillator 15 can set the second local frequency (flo2) to a frequency that is M times the frequency (fref) of the reference clock.

  Further, the second local oscillator 15 has 1 / N. By using the first frequency-divided signal affected by the phase noise and spurious generated by the F frequency divider 32 as a reference signal for synchronization processing, the second local signal including the effects of the phase noise and spurious is included. Is output. The second mixer 16 receives the first mixed signal including the effects of phase noise and spurious and the second local signal including the effects of phase noise and spurious, and therefore multiplies both signals. Thus, phase noise and spurious components can be attenuated.

  Thereby, according to the spectrum analyzer 10 of the present embodiment, 1 / N. By using the first frequency-divided signal output from the F frequency divider 32 as a reference signal for generating the second local signal, the 1 / N. The amount of transmission of phase noise and spurious generated due to the influence of the F frequency divider 32 can be reduced. Note that the second local oscillator 15 may use the output signal of the first VCO 31 as a reference signal for synchronization processing instead of using the first divided signal as a reference signal for synchronization processing.

  The third local oscillator 18 outputs a third local signal having a sine wave signal having a predetermined third local frequency (flo3) based on the first local signal. Specifically, the third local oscillator 18 generates a third local frequency (flo3) having a value obtained by multiplying the reference clock (fref) by a predetermined third fixed frequency division ratio L (L is an integer of 2 or more). ) Is output. Further, the third local oscillator 18 divides the output third local signal by the third division ratio L and adjusts the phase with the first divided signal.

  For example, the third local oscillator 18 may be a PLL circuit having a third VCO 51, a 1 / L frequency divider 52, a third phase comparator 53, and a third LPF 54. The third VCO 51 outputs a third local signal whose oscillation frequency varies according to the input voltage. The 1 / L frequency divider 52 divides the output third local signal by a fixed third frequency division ratio L, and supplies it to the third phase comparator 53 as a third frequency division signal.

  The third phase comparator 53 detects the phase error amount by comparing the phase of the first divided signal and the third divided signal. The third LPF 54 supplies a voltage obtained by averaging the phase error amount detected by the third phase comparator 53 to the third VCO 51. Then, the third VCO 51 changes the third local frequency (flo3) of the third local signal according to the input voltage. That is, the third VCO 51 changes the third local frequency (flo3) so that the third divided signal and the first divided signal are phase-synchronized. Thus, the third local oscillator 18 can adjust the phase of the third local signal with the first frequency-divided signal. The third local oscillator 18 can reduce the amount of transmission of phase noise and spurious generated from the first local oscillator 12 in the same manner as the second local oscillator 15.

  The third mixer 19 multiplies the second mixed signal by the third local signal, and adds the signal component included in each frequency of the second mixed signal to the plus side by the third local frequency (flo3), and , A signal shifted to the minus side by the third local frequency (flo3) is output. The third BPF 20 is a bandpass filter whose center frequency is set to D (KHz) (= C (MHz) −flo3), and has a predetermined band centered on D (KHz) in the output signal of the third mixer 19. Pass through the signal component. The third BPF 20 outputs the passed signal to the detection unit 21 as a third mixed signal obtained by mixing the second mixed signal and the third local signal.

  In the third local oscillator 18, when the third local frequency (flo 3) matches the frequency (f ref) of the reference clock, the third local signal is transferred to the third phase without going through the 1 / L frequency divider 52. It may be supplied to the comparator 53. Further, in the third local oscillator 18, when the third local frequency (flo3) is lower than the frequency (fref) of the reference clock, the third local signal is transmitted to the third phase without going through the 1 / L frequency divider 52. While supplying to the comparator 53, 1 / N. The first frequency division signal output from the F frequency divider 32 is frequency-divided by the 1 / L frequency divider 52 and supplied to the third phase comparator 53 as a reference signal.

  The third local oscillator 18 inputs the first frequency-divided signal of the first local oscillator 12 to the third phase comparator 53 as a reference signal, but instead of this, the second local oscillator 15 The frequency-divided signal may be supplied as a reference signal for the third phase comparator 53. That is, the third local oscillator 18 adjusts the phase between the third divided signal obtained by dividing the third local signal to be output by the third divider 52 and the second divided signal, thereby obtaining the second divided signal. A third local signal having a third local frequency (flo3) obtained by multiplying the frequency signal by the third frequency division ratio in the third frequency divider 52 may be output.

  The detection unit 21 detects the spectrum of the input signal based on the third mixed signal that is output according to the first local frequency (flo1). For example, the detection unit 21 detects energy included in the frequency to be detected in the input signal by amplifying and averaging the third mixed signal passed by the third BPF 20. The output unit 22 converts the detection result of the detection unit 21 from analog to digital and stores it in a memory as digital data. The output unit 22 uses the frequency to be detected (frf) and the energy amount included in the frequency in correspondence with each other. To the user.

  The setting unit 23 is 1 / N. By setting the first frequency dividing ratio (NF) of the F frequency divider 32, the first local frequency (flo1) of the first local signal is controlled. The setting unit 23 has a first frequency division ratio N.P. fixed at a predetermined value. F may be set. In addition, the setting unit 23 sets the dynamic first frequency division ratio N.I. so that the first local frequency (flo1) is repeatedly swept in a predetermined frequency range. By setting F, the spectrum distribution can be measured. Further, the setting unit 23 may change the bandwidth of the pass band of the third BPF 20 in accordance with the change in the frequency range to be measured.

Next, in the spectrum analyzer 10, 1 / N. It shows that the noise component caused by the phase noise and spurious generated in the F frequency divider 32 is reduced. 1 / N. When the jitter component including the phase noise and spurious generated by the F frequency divider 32 is Δfn, the frequency fref ′ of the first frequency-divided signal is as shown in Equation (1), and the first local frequency (flo1) ) Is as shown in equation (2).
fref ′ = fref + Δfn (1)
flo1 = (fref + Δfn) × N. F (2)

The frequency (fif1) of the first mixed signal output from the first BPF 14 is as shown in Expression (3).
fif1 = flo1-frf (3)
Substituting equation (2) into equation (3) yields equation (4).
fif1 = (fref + Δfn) × N. F-frf (4)

The frequency (fif2) of the second mixed signal output from the second BPF 17 is as shown in Expression (5).
fif2 = fif1-flo2 (5)
Substituting equation (4) into equation (5) yields equation (6).
fif2 = (fref + Δfn) × N. F-frf-flo2 (6)

Here, if the second local oscillator 15 generates the second local signal based on the reference clock generated from the reference oscillator 11, the second local frequency (flo2) is divided by the frequency (fref) of the reference clock. Since it is a value obtained by multiplying M, it is as shown in Expression (7).
flo2 = fref × M (7)
Further, when Expression (7) is substituted into Expression (6), Expression (8) is obtained.
fif2 = (fref + Δfn) × N. F-frf-fref × M
= (N.F−M) × fref + N. F × Δfn−frf (8)

On the other hand, the spectrum analyzer 10 of the present embodiment allows 1 / N. Assuming that 15 generates the second local signal based on the first frequency-divided signal of the F frequency divider 32, the second local frequency (flo2) is as shown in Expression (9).
fif2 = fref ′ × M = (fref + Δfn) (9)
Further, when Expression (9) is substituted into Expression (6), Expression (10) is obtained.
fif2 = (fref + Δfn) × N. F−frf− (fref + Δfn) × M
= (N.F−M) × fref + (N.F−M) × Δfn−frf (10)

When comparing the term of Δfn in equation (8) and the term of Δfn in equation (10), M <N. Therefore, the component of the jitter component Δfn in the case of this embodiment is {(N.N.) compared to the component of the jitter component Δfn in the case where the second local signal is generated based on the reference clock generated from the reference oscillator 11. FM) / N. F} is attenuated.
As described above, the spectrum analyzer 10 according to this embodiment has a 1 / N. The amount of phase noise and spurious noise generated by the F divider 32 can be reduced. Thereby, the spectrum analyzer 10 can detect the frequency component contained in the input signal with high accuracy.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

1 shows a configuration of a spectrum analyzer 10 according to the present embodiment.

Explanation of symbols

10 Spectrum Analyzer 11 Reference Oscillator 12 First Local Oscillator 13 First Mixer 14 First BPF
15 Second local oscillator 16 Second mixer 17 Second BPF
18 Third local oscillator 19 Third mixer 20 Third BPF
21 Detection unit 22 Output unit 23 Setting unit 31 First VCO
32 1 / N. F divider 33 first phase comparator 34 first LPF
41 Second VCO
42 1 / M frequency divider 43 Second phase comparator 44 Second LPF
51 3rd VCO
52 1 / L frequency divider 53 3rd phase comparator 54 3rd LPF

Claims (8)

A detector for detecting an input signal,
A reference oscillator for outputting a reference clock (fref);
The first local signal to be output is divided by a first divider capable of setting a division ratio in units of decimals and phase-adjusted with the reference clock, whereby the first clock is added to the first clock. A first local oscillator that outputs the first local signal having a first local frequency (flo1) multiplied by a first frequency division ratio in a frequency divider;
A first mixer that outputs a first mixed signal obtained by mixing the input signal and the first local signal;
A second local oscillator that outputs a second local signal having a predetermined second local frequency (flo2) based on the first local signal;
A second mixer for outputting a second mixed signal obtained by mixing the first mixed signal and the second local signal;
And a detector that detects a frequency component of the input signal corresponding to the first local frequency based on the second mixed signal output in accordance with the first local frequency.   The second local oscillator adjusts a phase between a second divided signal obtained by dividing the second local signal by a second divider and a first divided signal output from the first divider. 2. The detector according to claim 1, wherein the second local signal having a second local frequency (flo 2) obtained by multiplying the first frequency-divided signal by a second frequency division ratio in the second frequency divider is output. .   The detector according to claim 1, wherein the first frequency divider is a fractional frequency divider.   The detector according to claim 1, wherein the first local frequency is greater than the second local frequency and less than twice the second local frequency. By adjusting the phase between the third divided signal obtained by dividing the third local signal to be output by the third divider and the first divided signal, the third divided signal is converted into the third divided signal. A third local oscillator for outputting the third local signal having a third local frequency (flo3) multiplied by a third frequency division ratio in the circuit;
A third mixer for outputting a third mixed signal obtained by mixing the second mixed signal and the third local signal;
The detector according to claim 2, wherein the detection unit detects a spectrum of the input signal based on the third mixed signal output according to the first local frequency. By adjusting the phase between the third divided signal obtained by dividing the third local signal to be output by the third divider and the second divided signal, the second divided signal is divided into the third divided signal. A third local oscillator for outputting the third local signal having a third local frequency (flo3) multiplied by a third frequency division ratio in the circuit;
A third mixer for outputting a third mixed signal obtained by mixing the second mixed signal and the third local signal;
The detector according to claim 2, wherein the detection unit detects a spectrum of the input signal based on the third mixed signal output according to the first local frequency. The detector functions as a spectrum analyzer that measures the spectrum of the input signal.
The said detection part detects the spectrum of the frequency corresponding to the said 1st local frequency in the said input signal based on each of the said 2nd mixed signal output according to the said 1st local frequency. Detector. A detection method for detecting an input signal,
A reference oscillation stage for outputting a reference clock (fref);
The first local signal to be output is frequency-divided by a first frequency divider capable of setting a frequency division ratio in units of less than 1 and phase-adjusted with the reference clock to thereby add the first clock to the reference clock. A first local oscillation stage for outputting the first local signal having a first local frequency (flo1) multiplied by a first frequency division ratio in a frequency divider;
A first mixer stage for outputting a first mixed signal obtained by mixing the input signal and the first local signal;
A second local oscillation stage for outputting a second local signal having a predetermined second local frequency (flo2) based on the first local signal;
A second mixer stage for outputting a second mixed signal obtained by mixing the first mixed signal and the second local signal;
And a detection step of detecting a frequency component of the input signal corresponding to the first local frequency based on the second mixed signal output according to the first local frequency.

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