JPH08146062A - Phase jitter analyzer - Google Patents

Abstract

PURPOSE: To accurately and quickly measure the phase jitter of a signal to be measured without sweeping frequency. CONSTITUTION: A band-pass filter 33 is provided to filter signal in a bandwidth including a phase jitter component by receiving a intermediate frequency fif signal. Further, a cross detection part 11 is provided to generate phase data θby receiving the intermediate frequency fif signal from the band-pass filter 33, mixing it with the same oscillation frequency fosc as the intermediate frequency fif and converting the signal into data X of baseband signal, and mixing the signal with a signal obtained by rotating the same oscillation frequency fosc as the intermediate frequency fif by 90 degrees and converting the signal into data Y of the baseband signal, and receiving both signals, performing arctanY/X operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measurement of a phase jitter component contained in a sine wave signal generated from an oscillator or the like.

[0002]

2. Description of the Related Art As an example of measuring the phase jitter of a conventional oscillation source or the like, a spectrum analyzer is swept to observe a spectrum near the carrier frequency, and the phase jitter is measured from the sideband level. There is an example. This will be described with reference to FIGS. 5 and 6. As shown in FIG. 5, the configuration of this device is a configuration of a general spectrum analyzer, and includes an attenuator 21, a frequency conversion unit 20, a ramp voltage generation unit 30, a detection unit 34, and
It is composed of a D converter 36, an AD buffer memory 38, a display processing unit 80 and a display unit 64.

The signal under test 100 is attenuated to a desired level by an attenuator 21 and then supplied to the frequency converter 20. In the frequency conversion unit 20, the sweeping ramp signal from the ramp voltage generation unit 30 is received, the desired frequency range around the center frequency fc is swept by the variable oscillator 24, mixed by the mixer 22, and converted to a constant intermediate frequency. Then, after converting to the intermediate frequency fif by the mixer 26, the band pass filter (B
After filtering with a desired narrow band characteristic by PF) 32,
It is supplied to the detection unit 34. The spectrum waveform obtained as shown in FIG. 6 is quantized and converted into a digital signal by the AD converter 36, and then data of one sweep unit is stored in the AD buffer memory 38 for storage. Next, the display processing unit 8
0 indicates that after the stored data in the AD buffer memory 38 is sequentially read out and the phase jitter amount is calculated from the level value of the carrier frequency fc and the level values of the sideband frequencies 202 and 204, it is converted into various display forms. , And supplies it to the display unit 64 for display. In this way, measurement is performed for each sweep, and the display of this data is updated.

[0004]

As described above, the frequencies around the carrier frequency fc are swept to measure the carrier frequency level value and the sideband level value, and the phase jitter amount is calculated from this. Is displayed. This is repeatedly executed and displayed. Therefore, it takes several tens to several hundreds of milliseconds to sweep the frequency range of the sideband in a narrow band, and it takes a long time to perform one measurement, which makes it difficult to correctly measure the jitter that changes every moment. Alternatively, in the case of phase jitter adjacent to the carrier frequency fc such as a jitter frequency of several tens to several hundreds Hz, even if it is filtered by a narrow band filter, it is buried in the level of the carrier frequency and the detection error increases. However, there were some cases in which it was difficult to measure correctly and there was inconvenience in use.

Therefore, the problem to be solved by the present invention is to measure the signal under test 1 in a short time without sweeping the frequency.
The purpose is to measure the phase jitter of 00 with high accuracy.

[0006]

FIG. 1 shows a first solution according to the present invention. In order to solve the above-mentioned problem, the configuration of the present invention receives the intermediate frequency fif signal,
A bandpass filter 33 that filters with a bandwidth including a phase jitter component is provided, receives the intermediate frequency fif signal from the bandpass filter 33, mixes at the same oscillation frequency fosc as the intermediate frequency fif, and forms the baseband signal data X. Converted and set the same oscillation frequency fosc as the intermediate frequency fif to 90
The data Y of the baseband signal mixed with the rotated signal
And the signals of these two are subjected to arctan Y / X operation to generate the phase data θ, which serves as a constituent means. As a result, the signal under measurement 100 is transferred to the intermediate frequency fif
The signal to be measured 10 having the frequency conversion unit 20 for converting to
A phase jitter analyzer of 0 is realized. Quadrature detector 11
In the configuration, the intermediate frequency fif signal is received and the intermediate frequency fif is received.
An oscillator 44 that oscillates the same oscillation frequency fosc as if is provided, and a first mixer 41 that receives the intermediate frequency fif signal and mixes at the same oscillation frequency fosc as the intermediate frequency fif to output a baseband signal is provided. A low-pass filter 45 that passes the baseband signal with the output signal component from 41 is provided, receives the intermediate frequency fif signal, and mixes with the signal obtained by rotating the same oscillation frequency fosc as the intermediate frequency fif by 90 degrees to output the baseband signal. Second mixer 42
Is provided, a low-pass filter 46 that passes the baseband signal with the output signal component from the second mixer 42 is provided, and an AD converter 47 that converts the baseband analog signal from the low-pass filter 45 into digital signal data X is provided. , AD converter 48 for converting a baseband analog signal from the low-pass filter 46 into digital signal data Y, receives the baseband signal data X, Y of both, and performs an arctan Y / X operation to perform phase data. The constituent means is provided with the phase calculator 50 that outputs θ.

FIG. 3 shows a second solution according to the present invention. In order to solve the above problems, in the configuration of the present invention, a bandpass filter 33 that receives an intermediate frequency fif signal and filters with a bandwidth including a phase jitter component is provided, and the intermediate frequency fif signal from the bandpass filter 33 is provided. A high-speed AD converter 13 for receiving and converting to a digital signal Dif is provided, and the output digital signal D of the high-speed AD converter 13 is provided.
A buffer memory 14 for storing if is provided, the digital signal Dif is read from the buffer memory 14, and the baseband data X is multiplied by the oscillation frequency fosc data having the same frequency as the intermediate frequency fif, and the oscillation frequency f is the same as the intermediate frequency fif.
A quadrature detection processing unit 12 for converting osc into baseband data Y obtained by multiplying by 90 ° rotated data, and processing the signals of both by arctan Y / X operation to generate phase data θ.
Is provided.

In addition to the above configuration means, there is a configuration means for providing a display processing unit 62 which receives the phase data θ and removes non-baseband components in the phase data θ component by regression line correction. In addition to the above-described configuration means, there is a configuration means for providing a display processing unit 62 that receives the phase data θ, performs an FFT operation process, converts it into the frequency domain, and generates spectrum data of the frequency component of the phase jitter.

[0009]

The quadrature detection unit 11 has the sideband frequency 20
By performing phase detection on the intermediate frequency fif signal having 2,204 components and calculating the phase data θ = arctan (Y / X), there is a function of directly obtaining the phase jitter component. The phase data θ in the case of not being a perfect baseband is a true phase jitter component f (t) in which the deviation frequency Δωc component from the baseband is removed by performing a correction calculation by the least square method.
It has the effect of taking out only. Also, the phase jitter component f
(T) Upon receiving the data, the FFT processing is performed to obtain the spectrum data of the phase jitter converted into the frequency domain. With the configuration of the first embodiment, the phase jitter can be directly obtained by the quadrature detection without sweeping the frequency, the sweep time is unnecessary, and the transition of the phase jitter that changes moment by moment can be easily repeatedly displayed and updated. It will be possible. Further, it is possible to stably and accurately measure even the phase jitter of a low frequency component adjacent to the carrier frequency fc.

[0010]

【Example】

(Embodiment 1) An example of measuring the phase jitter of an oscillation source or the like of the present invention is an example in which a phase jitter component is directly obtained by quadrature phase detection from an intermediate frequency signal including sidebands.
This will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the configuration is such that an attenuator 21 and a frequency converter 2 are provided.
0, the quadrature detection unit 11, the display processing unit 62, and the display unit 6
It is composed of 4 and. In this configuration, the buffer memory 5
This is an example of realizing up to 2 with a circuit.

With this configuration, the attenuator 21, the frequency conversion section 20, and the display section 64 are the same as the conventional ones. The frequency conversion unit 20 converts the carrier frequency fc of the signal under measurement 100 into an intermediate frequency fif and outputs it without sweeping. BPF
33 receives the intermediate frequency fif signal and passes the entire sideband frequencies 202 and 204 components due to the phase jitter, so as to pass the wideband bandpass filter characteristic, for example, a bandwidth of 3 MHz to the quadrature detection unit 11. Supply.

The quadrature detector 11 performs an inverse operation in the case of a quadrature modulator, directly detects a phase jitter component by phase detection at the same frequency as fif, and as shown in FIG. 1 mixer 41, 2nd mixer 42, oscillator 44, phase shifter 43, low-pass filter (LP
F) 45 and 46, AD converters 47 and 48, a phase calculator 50, and a buffer memory 52. The oscillator 44 oscillates the same frequency fosc = fif as the intermediate frequency fif and supplies it to the mixer 41 and the phase shifter 43.
The mixer 41 mixes the frequency fosc of the oscillator 44 with the intermediate frequency fif signal containing the sideband frequency component to convert it into a baseband signal, and after passing only the baseband signal component by the LPF 45, After being quantized by the AD converter 47 and converted into digital data X, the data is supplied to one input end of the phase calculator 50. The mixer 42
The frequency fosc of the oscillator 44 is set to 90 by the phase shifter 43.
The signal whose phase has been rotated by a degree and the intermediate frequency fif signal containing the sideband frequency component are mixed and converted into a baseband signal, and only the baseband signal component is passed by the LPF 46, which is then converted into an AD converter 48. After being quantized by and converted into digital data Y, it is supplied to the other input end of the phase calculation unit 50. The phase calculator 50 receives both signals and calculates them by a θ = arctan (Y / X) calculator to obtain phase data θ. The data string f (t) of the phase data θ is stored in the buffer memory 52. If the phase data θ is in a perfect baseband state, a phase data string f (t) of a phase jitter component that does not include a carrier frequency fc component can be obtained.

The display processing unit 62 includes the buffer memory 5
The phase data θ stored in 2 is read out and the regression line is corrected. That is, the phase data θ may not be in a perfect baseband, and this is corrected and calculated. If the deviation frequency from the perfect baseband is Δωc and the jitter frequency of the phase data θ is f (t), the phase data θ
The expression of the data string of can be expressed as f (t) + Δωct. Here, t is time. The Δωct component is corrected and calculated by the least squares method to obtain only the f (t) component, and the f (t) data is calculated as the effective value and RMS averaged, and then supplied to the display unit 64 for display. Further, in order to display the jitter in the frequency domain subjected to the FFT processing, the f (t) component is subjected to the FFT processing and converted into the frequency domain, and the spectrum data of the frequency component of the phase jitter is supplied to the display unit 64.

The display unit 64 displays the data of the calculation result from the display processing unit 62 as the RMS average value in the form of jitter, or displays the spectrum of the FFT processed jitter in the frequency domain, according to various display modes. Alternatively, f (t) + Δωct, which is phase data, or baseband-corrected f (t) is displayed.

As described above, the sweep time is not necessary because the method of directly obtaining the phase jitter by the quadrature detection without sweeping the oscillation frequency does not require the sweep time. Since the quadrature detection is realized by the circuit, the processing time is reduced. It is possible to update the display of the transition of the phase jitter that is short and changes from moment to moment almost continuously. Further, it is possible to stably and accurately measure even the phase jitter of a low frequency component adjacent to the carrier frequency fc.

(Embodiment 2) The embodiment of the present invention is an example of measuring the phase jitter by quadrature phase detection of the intermediate frequency signal including the side band by the soft processing means. This will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the configuration includes an attenuator 21, a frequency conversion unit 20, and
The high-speed AD converter 13, the AD buffer memory 14, the quadrature detection processing unit 12, the display processing unit 62, and the display unit 64. In this configuration, the AD buffer memory 1
The circuits up to 4 are constituted, and the quadrature detection processing unit 12 thereafter is realized by software processing. With this configuration, the attenuator 21, the frequency conversion unit 20, the display processing unit 62, and the display unit 64 are
This is similar to the case of the first embodiment.

The high-speed AD converter 13 directly quantizes the intermediate frequency fif signal of 5 MHz, for example, at 20 MHz by the high-speed AD converter 13 to convert it into a digital signal, and then stores it in the AD buffer memory 14. After that,
This digital data is read and the quadrature detection processing unit 12 executes the calculation.

The quadrature detection processing unit 12 is a DSP or C
It is calculated by software processing by PU. As shown in FIG. 4, this software processing configuration is for performing phase detection at the same frequency as the intermediate frequency fif to directly extract the phase jitter component. The first mixer 71, the second mixer 72, and the oscillator 7 are used.
4, a phase shifter 73, a low pass filter (LPF)
It is composed of 75 and 76 and a phase calculator 79. The oscillator 74 generates sine waveform data having the same frequency fosc = fif as the intermediate frequency fif and supplies it to the mixer 71 and the phase shifter 73. The mixer 71 processes this oscillator 7
The frequency X fosc data of 4 and the intermediate frequency fif signal data read from the AD buffer memory 14 are multiplied to be converted into a baseband signal, and the data X which has been subjected to the low-pass filter processing in which only the baseband signal component is passed by the LPF 75 , To one of the phase calculators 79. In the processing of the other mixer 72, the data obtained by rotating the frequency fosc data of the oscillator 74 by 90 degrees in the phase shifter 73 and the intermediate frequency fif signal data read from the AD buffer memory 14 are multiplied to form a baseband signal. The data Y that has been converted and subjected to the low-pass filter processing that passes only the baseband signal component in the processing of the LPF 76 is
The signal is supplied to the other of the phase calculator 79. In the phase calculation unit 79 processing, both signals are received, θ = arctan (Y / X) calculation processing is executed to obtain phase data θ, and the phase data θ is supplied to the display processing unit 62. The subsequent steps are the same as in the first embodiment.

As described above, by directly converting the intermediate frequency fif signal into a digital signal and thereafter performing arithmetic processing with software, the phase jitter can be obtained by direct quadrature detection and is adjacent to the carrier frequency fc. The advantage is that stable and accurate measurement is possible even with phase jitter of low frequency components.

[0020]

Since the present invention is configured as described above, it has the following effects. The BPF 33 having a wideband band-pass filter characteristic supplies the quadrature detection unit 11 with the intermediate frequency fif signal that passes the entire sideband frequencies 202 and 204 components, and the quadrature detection unit 11 performs phase detection at the same frequency as fif. By calculating the phase data θ = arctan (Y / X), the effect of directly extracting the phase jitter component of the phase data string f (t) can be obtained. Further, when the phase data θ is not in a perfect baseband, the deviation frequency Δωc is corrected and calculated by the least square method, and the effect of extracting only the true phase jitter component f (t) can be obtained. Also, the phase jitter component f
(T) By receiving the data and performing the FFT process, there is an effect that the spectrum data of the phase jitter converted into the frequency domain can be obtained.

In the first embodiment, since the phase jitter is obtained by the direct quadrature detection, the sweep time is not necessary, and since the quadrature detection is realized by the circuit, the processing time is short and the phase jitter which changes moment by moment. The transition can be continuously displayed and updated. Further, it is possible to stably and accurately measure even the phase jitter of a low frequency component adjacent to the carrier frequency fc. In the second embodiment, the direct intermediate frequency fif
By converting the signal into a digital signal, it is possible to obtain the phase jitter by a software operation thereafter, and it is possible to stably and accurately measure the phase jitter of a low frequency component adjacent to the carrier frequency fc.

[0022]

[Brief description of drawings]

FIG. 1 is a configuration diagram of phase jitter measurement according to the present invention.

FIG. 2 is a configuration diagram of a quadrature detection unit 11 of the present invention.

FIG. 3 is a diagram showing a phase jitter measurement configuration realized by soft processing means after the intermediate frequency fif of the present invention.

FIG. 4 is a configuration diagram of a processing block diagram of a quadrature detection processing unit 12 that performs arithmetic processing by software according to the present invention.

FIG. 5: Sweeping a conventional spectrum analyzer,
It is a block diagram which measures a phase jitter from the level of a sideband.

FIG. 6 is an example of a spectrum waveform of phase jitter.

[Explanation of symbols]

 11 quadrature detection unit 12 quadrature detection processing unit 13 high-speed AD converter 14, 38 AD buffer memory 20 frequency conversion unit 21 attenuator 22, 26, 41, 42, 71, 72 mixer 24 variable oscillator 30 lamp voltage generation unit 32, 33 Band pass filter (BPF) 34 Detection section 36, 47, 48 AD converter 43, 73 Phase shifter 44, 74 Oscillator 45, 46, 75, 76 Low pass filter (LPF) 50, 79 Phase calculation section 52 Buffer memory 62, 80 Display processing unit 64 Display unit 100 Measured signal 202, 204 Sideband frequency fif Intermediate frequency fc Carrier frequency X, Y data

Claims (5)

[Claims] 1. A signal under measurement (100) is fed to an intermediate frequency (f
In a phase jitter analyzing apparatus for a signal under measurement (100) having a frequency converter (20) for converting into a if), the frequency converter (20) receives the signal under measurement (100).
The band pass filter (33) for filtering the intermediate frequency (fif) signal output by the filter is filtered by the bandwidth including the phase jitter component, the intermediate frequency (fif) signal is received, and the intermediate frequency (fif) signal is received.
if) is mixed with the same oscillation frequency (fosc) and converted into baseband signal data (X), and the same oscillation frequency (fosc) as the intermediate frequency (fif) is mixed with a signal rotated by 90 degrees to obtain the baseband signal. Phase data (θ) by converting the two signals to arctan (Y / X).
A phase jitter analysis apparatus comprising a quadrature detection unit (11) for generating a signal and including the above. 2. The quadrature detection unit (11) has a structure of receiving an intermediate frequency (fif) signal and receiving the intermediate frequency (fif).
Oscillator (44) that oscillates the same oscillation frequency (fosc) as
To receive the intermediate frequency (fif) signal and receive the intermediate frequency (fif)
Is provided with a first mixer (41) that mixes at the same oscillation frequency (fosc) and outputs a baseband signal, and a low-pass filter (45) that passes the baseband signal with the output signal component from the first mixer (41) is provided. Provided, receives the intermediate frequency (fif) signal, and receives the intermediate frequency (fif)
A second mixer (42) for outputting a baseband signal by mixing the same oscillation frequency (fosc) with a signal rotated by 90 degrees
And a low-pass filter (46) for passing the baseband signal with the output signal component from the second mixer (42) is provided, and the baseband analog signal from the low-pass filter (45) is converted into digital signal data (X). An AD converter (47) for converting is provided, and an AD converter (48) for converting the baseband analog signal from the low-pass filter (46) into digital signal data (Y) is provided. A phase calculator (50) for receiving data (X, Y) and performing arctan (Y / X) calculation to output phase data (θ) is provided, and the phase calculation unit (50) is provided. The described phase jitter analyzer. 3. The signal under test (100) is fed at an intermediate frequency (f
In a phase jitter analyzing apparatus for a signal under measurement (100) having a frequency converter (20) for converting into a if), the frequency converter (20) receives the signal under measurement (100).
The band pass filter (33) for filtering the intermediate frequency (fif) signal output by the filter is filtered by the bandwidth including the phase jitter component, and the intermediate frequency (f
A high speed AD converter (13) for receiving the if signal and converting it into a digital signal (Dif) is provided, and an output digital signal (Di) of the high speed AD converter (13) is provided.
The buffer memory (14) for storing f) is provided, the digital signal (Dif) is read from the buffer memory (14), and the same oscillation frequency (fos) as the intermediate frequency (fif) is read.
c) Baseband data (X) multiplied by the data,
The same oscillation frequency (fosc) as the intermediate frequency (fif) is set to 90.
Converted to baseband data (Y) multiplied by the rotated data, and the signals of both are arctan (Y / X)
A phase jitter analyzing apparatus comprising a quadrature detection processing unit (12) for performing arithmetic processing to generate phase data (θ), and having the above. 4. In addition to the constituent means according to claim 1 or claim 2, the phase data (θ) is received, and a non-baseband component in the phase data (θ) component is removed by regression line correction. A phase jitter analysis apparatus comprising a display processing unit (62) for performing the above and having the above. 5. In addition to the constituent means according to claim 1 or claim 2, the phase data (θ) is received, FFT arithmetic processing is performed and converted into a frequency domain, and spectrum data of a frequency component of phase jitter is obtained. A phase jitter analyzing apparatus comprising a display processing unit (62) for generating and having the above.