JPH0228935B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention corrects the detuning deviation caused by the change in the characteristics of the internal resolution bandwidth filter of a heterodyne receiver measuring instrument, and measures the phase error between two channels. This invention relates to a receiving device for position measurement that automatically corrects itself.

(Prior Art) A measuring instrument equipped with a conventional general heterodyne receiver, such as a selective level meter or a spectrum analyzer, employs the circuit configuration shown in FIG.

In FIG. 6, the input signal to be measured inputted from the input terminal 101 is transmitted to the local oscillator 10 inside the receiver.
2 and the mixer 103, and an intermediate frequency signal (IF signal) is generated at the output of the mixer 103. The intermediate frequency signal is passed through a resolution bandwidth filter 10.
4, and further detected by a detector 105. and analog-digital converter 1
06, the signal is converted into a digital signal, and after being subjected to calculation processing in the data processing unit 107, it is displayed on the CRT display device 108.

Furthermore, FIG. 7 shows the circuit configuration of a conventional general network/spectrum analyzer equipped with a heterodyne receiver.

The network/spectrum analyzer has two input terminals, an R channel input terminal 109 and a T channel input terminal 110. The input signals to be measured of both channels inputted from these two terminals are inputted to mixers 112 and 113, respectively, and mixed with the output signal of the common internal local oscillator 111 in the mixers 112 and 113. Then, each signal is band-limited by resolution bandwidth filters 114 and 115, and further detected by wave detectors 116 and 117. The analog-to-digital converter 118 converts the signal into a digital signal, and the data processor 119 converts the signal into a digital signal.
After calculation processing, the data is displayed on the CRT display device 120. In the case of phase measurement, the input signals to be measured of both channels are applied to the phase detector 121 to obtain a phase difference as an analog voltage, which is converted into a digital signal by the analog-digital converter 118. After calculation processing in the data processing unit 119,
It is displayed on the CRT display device 120.

(Problems to be Solved by the Invention) However, in the conventional circuit configuration method, as shown in FIG. There were significant drawbacks to the tone.

When measuring phase characteristics in the circuit configuration of a conventional general network/spectrum analyzer equipped with a heterodyne receiver as shown in FIG.
The disadvantage was that the detuning caused errors in the phase characteristics.

The present invention aims to solve the above-mentioned drawbacks, and includes at least a reference oscillator with a stable frequency inside, and measures the detuning curve of the resolution bandwidth filter with respect to the reference signal by sweeping the frequency of the local oscillator. do. Then, the frequency shift of the level peak point is detected, and the tuning frequency of the resolution bandwidth filter is changed based on the frequency shift to match the intermediate frequency. Provided is a phase measurement receiving device that obtains a standard phase between two channels with respect to the same reference signal under this synchronized state and automatically corrects an error in the measured phase between the two channels using the standard phase. It is intended to.

(Means for Solving the Problem) Therefore, the phase measurement receiving device of the present invention includes a first channel through which a signal to be a reference passes and a second channel through which a signal having a phase difference to be measured passes. A phase measurement receiver comprising: a reference oscillator that generates a predetermined frequency serving as a measurement reference; input switching means that selectively switches and outputs an input signal to be measured and an output signal of the reference oscillator; and a variable local oscillator. a mixer for a first channel and a mixer for a second channel, each of which is provided in each channel and which receives the output signal of the input switching means and the output signal of the local oscillator and outputs an intermediate frequency f ₀ ; Variable tuning bandpass filters for the first channel and the second channel are provided, respectively, and can be tuned to the intermediate frequency f ₀ by receiving the output signal of the mixer for each channel, and the input switching means is connected to the reference oscillator. When the output signal of the bandpass filter for each channel is output, the level peak position of the bandpass filter characteristic is determined by gradually increasing or decreasing the oscillation frequency of the local oscillator and detecting the output signal of the bandpass filter for each channel. The peak level transition characteristics of the bandpass filter for each channel are stored in advance based on the level peak position detection means for the first channel and the second channel to be detected respectively, and the detected peak positions. tracking means for a first channel and a second channel that refers to a tuning curve table and matches the tuning frequency of a bandpass filter for each channel with the intermediate frequency _{f 0 from} the tuning curve table; a phase difference detection means for detecting the phase difference at the peak position of the bandpass filter for each channel when matching the phase difference, a storage means for storing the detected phase difference, and the input switching means output the input signal to be measured. In this case, the present invention is characterized in that it is provided with an automatic detuning correction means comprising a correction means for correcting the phase difference of the output signal of each channel using the phase difference stored in the storage means. The present invention will be described below with reference to the drawings.

Figure 1 shows the configuration of an embodiment of a phase measurement receiver according to the present invention, Figure 2 shows the circuit configuration of an embodiment of a resolution bandwidth filter that changes the tuning of the filter, and Figure 3 shows the initial variable capacitance diode application. Voltage-frequency tuning curve, FIG. 4 is an explanatory diagram explaining changes in tuning frequency, and FIG. 5 is an example configuration of a network/spectrum analyzer using the phase measurement receiver according to the present invention. It shows.

In FIG. 1, 1 is a reference oscillator, 2a, 2b
3 is an input switching means, 3 is a variable local oscillator, 4a, 4
b is a mixer, 5a and 5b are bandpass filters,
6 is a level peak position detection means, 7 is a tracking means, 8 is a tuning curve table, 10 is a correction calculation means, 12 is a phase detector, 13 is a standard phase storage means, 16 is an analog-digital converter, and 18 is a display means. , 19a, 19b are detectors.

The variable local oscillator 3 is of a synthesizer type with high frequency resolution, for example, and the reference oscillator 1 is an oscillator whose phase is synchronized with the variable local oscillator 3 to stabilize its frequency.

The bandpass filters 5a and 5b are resolution bandwidth filters, that is, RBW filters, and a variable capacitance diode 61 is used as a constituent element of the resolution bandwidth filter, as shown in FIG. The peak position of the tuning frequency of the filter changes depending on the voltage applied to the variable capacitance diode. In addition, in FIG. 2, 62 is a crystal.

The tracking means 7 includes a bandpass filter 5
It plays the role of matching the tuning frequency at which the output level of each of mixers a and 5b reaches its peak with the intermediate frequency f ₀ of mixers 4 a and 4 b, and as a means for matching the intermediate frequency f ₀ as described above, the variable A voltage to be applied to the capacitor diode 61 is supplied.

The level peak position detection means 6 includes the reference oscillator 1
When performing mixing by slightly changing the sweep frequency of the variable local oscillator 3 with respect to the reference level and reference frequency signals of the bandpass filter 5a (5a will be explained below),
The same is true for b)) and detects the position of the sweep frequency where the peak of the level outputted from is the maximum. In order to detect the position of the sweep frequency where the peak of this level is maximum, for example, the center frequency fc is set in the variable local oscillator 3, and the output of the bandpass filter 5a at that time, that is, the analog
The output _M0 of the digital converter 16 and the sweep frequency of the variable local oscillator 3 are set to a frequency that is one step larger (or smaller) than the center frequency fc, and the output of the bandpass filter 5a at that time, that is, the analog-digital converter This is done by comparing the output _M1 of No. 16. In this case, M ₁ −M ₀ >0
Then, it is found that the maximum value is on the frequency side that is one step larger (or smaller) than the center frequency fc, and the sweep frequency of the local oscillator 3 is set to a frequency that is two steps larger (or smaller) than the center frequency fc.
When Mi + ₁ - Mi < 0 (i = 1, 2, 3, ...), this is the position where the output level of the bandpass filter 5a is maximum at the sweep frequency of the previous step. I understand that. This is obvious since the crystal filter of the bandpass filter 5a has a single peak characteristic. Also, M ₁ −M ₀ <
In the case of 0, the level peak position detecting means 6 can detect the position of the sweep frequency at which the output level of the bandpass filter 5a is maximum in exactly the same manner.

Due to changes in ambient temperature or changes over time,
It is assumed that the frequency at which the maximum output level of the bandpass filter 5a is reached is a frequency _f1 , which is a deviation of _Δf from the intermediate frequency f0 output by the mixer 4a. In order to eliminate this detuned frequency deviation Δf, the tuning frequency f ₀ is determined from the initial variable capacitance diode applied voltage-frequency tuning curve shown in FIG. 3 for the bandpass filter 5a, which has been determined in advance. Voltage difference of voltage applied to variable capacitance diode −
Find ₀ . Then, this voltage difference − ₀ is subtracted from the original voltage applied to the variable capacitance diode ₀ , which is V ₀ −
Find the voltage (V-V ₀ )=2V ₀ -V. This variable capacitance diode applied voltage ₀ is applied to the variable capacitance diode 61 of the bandpass filter 5a. As a result, the tuning frequency of the bandpass filter 5a becomes f ₀ of the curve K ₂ shown in FIG. 4. That is, the curve moves from the curve _K1 shown in FIG. ₄ to the curve K2, and the tuning frequency of the bandpass filter 5a matches the intermediate frequency _f0 output from the mixer 4a.

In exactly the same way, the tuning frequency of the bandpass filter 5b of the other channel can be made to match the intermediate frequency f ₀ output from the mixer 4b.

In this way, with the tuning frequencies of the bandpass filters 5a and 5b of both channels matching the intermediate frequency _f0 , the input switching means 2a of the R channel and the input switching means 2 of the T channel
b are both connected to the reference oscillator 1 side, and the same signal from the reference oscillator 1 is sent to the mixers 4a and 4 of each channel.
supply to b. The standard phase φ ₁ obtained from the phase detector 12 at this time is digitized by the analog-digital converter 16, and the standard phase φ 1
3 is stored.

Next, the input switching means 2a, 2b of both channels are both switched to the input signal to be measured side, and the phase difference between the input signals to be measured that are input to both channels is measured. As is clear from the above explanation, when measuring the input signal under test, the bandpass filter 5 is used.
It goes without saying that the tuning frequencies of a and 5b match and are tuned to the intermediate frequency f ₀ output from each mixer. When measuring the phase of the input signals to be measured that are input to both channels, the phase φ _M output from the analog-digital converter 16 is input to the correction calculation means 10. The correction calculation means 10 reads out the standard phase φ ₁ stored in the standard phase storage means 13 , and the correction calculation of φ _M −φ ₁ is performed by the correction calculation means 10 .
is executed. The phase φ _M −φ ₁ corrected by the correction calculation means 10 is sent to the display device 18 and displayed on a CRT display device or the like. At this time, as described above, since the tuning frequency of the bandpass filters 5a and 5b is made to match the intermediate frequency of each mixer 4a and 4b, the detuning error caused by the detuning of the bandpass filters 5a and 5b is completely corrected. Ru. and φ _M
-φ ₁ is input switching means 2a, 2b for each channel
This value is used to relatively correct the phase error caused by each circuit from the to the analog-to-digital converter 16.

FIG. 5 shows the configuration of an embodiment of a network/spectrum analyzer in which the phase measurement receiver according to the present invention is used.

In Figure 5, 1, 2a, 2b, 6, 7, 1
2, 13, 16, 18, 19a, and 19b correspond to those in FIG. Mixers 4a, 4'a, 4''a and 4'b, which constitute a triple superheterodyne system, correspond to those in FIG.
4'b, 4''b and variable local oscillator 3, and local oscillators 3', 3'' correspond to 4 and 3, respectively. Resolution bandwidth (RBW) filter 5a, 5'a, 5''a
corresponds to resolution bandwidth filter 5b,
5'b and 5''b correspond to 5b. Also, the phase correction calculation means 10c corresponds to 10. 9 corresponds to 5b.
RBW peak value storage means, 10a is R channel level correction calculation means, 10b is T channel level correction calculation means, 15a, 15'a, 15b, 1
5'b is a switching means, 20 is a measurement/calibration control means,
21 is an arithmetic control means, 22 is a sweep signal control means,
23 is an input means. In addition, tracking means 7
are voltage code table storage means 71, RBW tracking voltage code storage means 72, tracking control means 73 during calibration, tracking control means 74 during measurement, and digital-to-analog converters 75, 7.
It consists of 6.

As is clear from Figure 5, in the case of phase measurement, R
Measurement is performed using two channels, a channel system and a T channel system, and in the case of level measurement, measurement can be performed using either the R channel or the T channel.

The voltage code table storage means 71 of the tracking means 7 stores a table obtained as follows. That is, for example, if the resolution bandwidth filter 5a of the R channel system is explained as a representative example, the mixer 4'' is added to the resolution bandwidth filter 5a.
f ₀ −ΔF centered on the intermediate frequency f ₀ of a to f ₀ +
Apply a sweep frequency of approximately 1/300 steps up to ΔF using another measuring device. For each sweep frequency of about 1/300 steps, change the voltage applied to the variable capacitance diode of the resolution bandwidth filter 5a, and apply the voltage to the variable capacitance diode when the output level from the resolution bandwidth filter 5a reaches its peak. Read each voltage. In other words, the variable capacitance diode applied voltage-frequency tuning curve shown in FIG. 3 is obtained.
A table is created by coding the voltage applied to each variable capacitance diode with respect to the sweep frequency in 1/300 steps from f ₀ −ΔF to f ₀ +ΔF. The table obtained in this way is stored in advance in the voltage code table storage means 71 as a table for the resolution bandwidth filter 5a. Similarly, the R channel resolution bandwidth filter 5'
For the resolution bandwidth filters 5b, 5'b, and 5''b of the T channels, the tables described above are created and stored in the voltage code table storage means 71 in advance. The number of resolution bandwidth filters is not limited to that shown in FIG. Furthermore, the respective bandwidths of the R channel resolution bandwidth filters 5a, 5'a, 5''a are the same as those of the T channel resolution bandwidth filters 5b, 5'b,
Needless to say, they are provided corresponding to each of the 5''b bandwidths.

Next, it is assumed that the calibration mode is input by specifying the resolution bandwidth filter 5a of the R channel and the resolution bandwidth filter 5b of the T channel from the input means 23. In order to first calibrate the resolution bandwidth filter 5a of the R channel, the measurement/calibration control means 20 connects the input switching means 2a to the reference oscillator 1 side, and switches between the switching means 15a and 15b.
operates to select the resolution bandwidth filter 5a of the R channel. Measurement/calibration control means 20
accesses the voltage code table storage means 71 via the calibration time tracking control means 73 and reads out the code of the variable capacitance diode applied voltage ₀ for the intermediate frequency f ₀ of the resolution bandwidth filter 5a. The digital-to-analog converter 75 converts the voltage into voltage ₀ , and the voltage ₀ is applied to the variable capacitance diode of the resolution bandwidth filter 5a.

On the other hand, the measurement/calibration control means 20 sends a control signal to the variable local oscillator 3 via the sweep signal control means 22, so that the intermediate frequency output from the mixer 4''a is f ₀ -
The variable local oscillator 3 oscillates an oscillation frequency that changes in 1/300 steps from ΔF to f ₀ +ΔF. First, the variable local oscillator 3 is set so that the intermediate frequency output from the mixer 4''a is _f0 , and the output level _M0 obtained by the analog-digital converter 16 at that time is detected by the level peak position detecting means 6. Store.Next, set the intermediate frequency output from mixer 4″a to 1.
The variable local oscillator 3 is set by the sweep signal control means 22 so as to obtain f ₀ +ΔF/150, which is a step-advanced value. The output level _M1 obtained by the analog-to-digital converter 16 at this time is input to the level peak position detection means 6, and compared with the previously stored output level _M0 to see which one is larger. _M1−
If M ₀ > 0, the variable local oscillator 3 controls the sweep signal control means 22 so that the intermediate frequency output from the mixer 4''a is further advanced by one step to f ₀ +2ΔF/150.
The output level _M2 at this time is obtained. Then, the level peak position detecting means 6 compares the currently input output level _M2 with the previously input output level _M1 . By repeating these processes, the level peak position detecting means 6 detects at what step from the intermediate frequency _f0 the position of the sweep frequency at which the output level is maximum occurs, as explained in FIG. Using the number N of steps at which the output level is maximum as an address, the tracking control means 73 during calibration accesses the voltage code table storage means 71, and performs the calibration with respect to the resolution bandwidth filter 5a stored in advance in the voltage code table storage means 71. Read the code of the voltage applied to the variable capacitance diode. This code is used as a tracking code for the resolution bandwidth filter 5a in the RBW tracking voltage code storage means 72.
is memorized. Next, the measurement/calibration control means 20 sets the variable local oscillator 3 via the sweep signal control means 22 so that the intermediate frequency output from the mixer 4''a becomes _f0 . The tracking code of the resolution bandwidth filter 5a is read out from the RBW tracking voltage code storage means 72, and the variable capacitance diode applied voltage V ₀ currently applied to the variable capacitance diode 61 of the resolution bandwidth filter 5a is read out. RBW from double the code of
A value obtained by subtracting the tracking code stored in the tracking voltage code storage means 72, that is, a code value corresponding to 2V ₀ -V explained in FIG. 1 is converted into an analog signal by the digital-to-analog converter 75. This analog signal is applied to the variable capacitance diode for the resolution bandwidth filter 5a. As a result, the resolution bandwidth filter 5a
The tuning frequency coincides with the intermediate frequency f ₀ output from the mixer 4''a.
is input. The analog-digital converter 1
The output level _l11 digitized in step 6 is stored in the RBW peak value storage means 9.

In this way, the calibration of the resolution bandwidth filter 5a of the R channel is completed. Similarly, the measurement/calibration control means 20 calibrates the resolution bandwidth filter 5b of the T channel. Next, the measurement/calibration control means 20 connects both the B channel and T channel input switching means 2a and 2b to the reference oscillator 1 side. The same oscillation signal from the reference oscillator 1 is simultaneously applied to mixers 4a and 4b. The standard phase φ ₁₁ for the resolution bandwidth filters 5 a and 5 b obtained from the phase detector 12 at this time is digitized by the analog-digital converter 16 and stored in the standard phase storage means 13 . Similarly, resolution bandwidth filters 5'a,
5′b, the standard phases φ ₂₁ and φ ₃₁ for the resolution bandwidth filters 5″a and 5″b are the standard phase storage means 13
is memorized.

Next, the resolution bandwidth and phase are designated from the input means 23, and the measurement mode is input.

The measurement/calibration control means 20 includes input switching means 2a,
2b is the R channel input on the input signal side under test, T
Connect to each channel input. At the same time, the switching means 15a selects a resolution bandwidth filter corresponding to the designated resolution bandwidth from the R channel and the T channel in a paired form;
15b, 15'a and 15'b are activated. Subsequently, tracking of the resolution bandwidth filters selected in pairs from the R channel and the T channel is performed by the tracking control means 74 at the time of measurement. That is, the tracking codes for the resolution bandwidth filters are read out from the RBW tracking voltage code storage means 72, the value of the code corresponding to 2V ₀ -V described above is determined, and the digital-to-analog converter 75 calculates the tracking code for each resolution bandwidth filter. An analogized voltage is applied to each variable capacitance diode of the resolution bandwidth filter. Then, assuming that the standard phase for the pair of resolution bandwidth filters is selected from the standard phase storage means 13, for example, a pair of resolution bandwidth filters 5a and 5b, the arithmetic control means 21 calculates φ ₁₁ . Read out this standard phase φ ₁₁ and apply it to the phase correction calculation means 10
Transfer to c.

Under such conditions, the R channel input and T
The phase difference of the input signals under test respectively connected to the channel inputs is measured. The measured phase difference of the input signal to be measured is digitized by the analog-digital converter 16, and the phase difference is digitized by the analog-digital converter 16.
Sent to 0c. Now, if the phase difference of the measured input signal is φ _M , then the phase correction calculation means 10
At c, a correction calculation of φ _M -φ ₁₁ is performed, and the calculation result is displayed on the CRT display device 18.

The above operation is the same even if other pairs of resolution bandwidth filters are selected.

(Effects of the Invention) As described above, according to the present invention, the phase difference of the input signal to be measured is measured while the resolution bandwidth filter used is always automatically matched to the intermediate frequency. Since the phase is corrected by calculation from this measured value and the previously stored standard phase of the resolution bandwidth filter, it is possible to measure the phase with high accuracy. In addition, since the standard phase and measurement phase are measured using the same circuit, the phase error of each circuit is relatively corrected.
This has the effect of being able to measure the phase with high accuracy.

[Brief explanation of drawings]

Figure 1 shows the configuration of an embodiment of a phase measurement receiver according to the present invention, Figure 2 shows the circuit configuration of an embodiment of a resolution bandwidth filter that changes the tuning of the filter, and Figure 3 shows the initial variable capacitance diode application. Voltage-frequency tuning curve, FIG. 4 is an explanatory diagram explaining changes in tuning frequency, and FIG. 5 is an example configuration of a network/spectrum analyzer using the phase measurement receiver according to the present invention. , Figure 6 shows an example of the configuration of a conventional general heterodyne receiver, Figure 7 shows the circuit configuration of a conventional general network/spectrum analyzer equipped with a heterodyne receiver, and Figure 8 shows the resolution band filter used. FIG. 3 is an explanatory diagram of a level error due to detuning of. In the figure, 1 is a reference oscillator, 2a and 2b are input switching means, 3 is a variable local oscillator, 4a and 4b are mixers, 5a and 5b are bandpass filters, 6 is a level peak position detection means, 7 is a tracking means,
10 is a correction calculating means, 12 is a phase detector, 13 is a standard phase storage means, 16 is an analog-digital converter, and 19a and 19b are detectors.

Claims (1)

[Claims] 1. A receiving device for phase measurement comprising a first channel through which a signal to be a reference passes and a second channel through which a signal having a phase difference to be measured passes, which serves as a measurement reference. a reference oscillator 1 that generates a predetermined frequency; input switching means 2a that selectively switches and outputs the input signal to be measured and the output signal of the reference oscillator;
2b, a variable local oscillator 3, and a first channel and a second channel respectively provided in each channel and receiving the output signal of the input switching means and the output of the variable local oscillator and outputting an intermediate frequency _f0 . mixers 4a and 4b for each channel, and variable tuning type bandpass filters for the first channel and the second channel that are provided in each channel and can be tuned to the intermediate frequency f ₀ by receiving the output signal of the mixer for each channel. 5a, 5
(b) When the input switching means outputs the output signal of the reference oscillator, the oscillation frequency of the variable local oscillator is gradually increased or decreased to change the output signal of the bandpass filter for each channel, respectively. Level peak position detecting means 6 for the first channel and for the second channel each detecting the level peak position of the bandpass filter characteristic by detection, and based on the detected respective peak positions,
The tuning curve table 8 in which the peak level transition characteristics of the band pass filter for each channel are stored in advance is referred to, and the tuning frequency of the band pass filter for each channel is made to match the intermediate frequency f ₀ from the tuning curve table. Tracking means 7 for the first channel and for the second channel
and a phase difference detection means 12 for detecting the phase difference in the peak value of the bandpass filter for each channel when matched with the intermediate frequency f ₀ , and a standard phase storage means 13 for storing the detected phase difference. , when the input switching means outputs the input signal to be measured, an automatic correction calculation means for correcting the phase difference of the output signal of each channel based on the phase difference stored in the standard phase storage means; A phase measurement receiving device characterized by comprising a detuning correction receiving device.