JP3167740B2 - Burst signal measuring circuit and burst signal measuring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burst signal measuring circuit.
For example, the present invention relates to a circuit and a method for measuring a pulse-like intermittent signal (burst signal) which is active for an extremely short period in a spectrum analyzer with high stability and high accuracy. />

[0002]

2. Description of the Related Art For example, a spectrum analyzer is used not only for analyzing the frequency of a continuous waveform but also for analyzing the frequency of a burst signal. However, when such a burst signal is measured in the same manner as a normal continuous wave, the spectrum diagram is difficult to see because, in addition to the frequency component during the active period of the burst signal, the frequency component due to the intermittent burst signal also appears in the measurement. There is a disadvantage that accurate frequency measurement cannot be performed. For this reason, the following are conventionally known as spectrum analyzers used when measuring a burst signal.

For example, in an analyzer as disclosed in Japanese Utility Model Application Laid-Open No. 62-189669, as shown in a circuit diagram of FIG. 3A and a waveform diagram of FIG. The burst signal A is input to the mixer 2. On the other hand, a gate signal B of the burst signal A (a signal that is activated in synchronization with the signal A) B is output to the sweep signal generation circuit 10. The sweep signal generation circuit 10 includes a current source 10a,
Switch 10b and integrator 10c (operational amplifier 10c ')
And a capacitor 10c "), and outputs a sweep signal synchronized with the gate signal B to the local oscillator 1.
Output to 1. The local oscillator 11 outputs a local signal LO having a frequency f _LO according to the input to the mixer 2. In the mixer 2, to synthesize a frequency f _LO of the frequency f _A and the local signal LO input burst signals A, bandpass filter (not shown) signals the synthesized frequency f _IF, via an amplifier or the like sample and hold circuit (S / H circuit) 4
Output to The S / H circuit 4 performs a sample and hold operation at a predetermined cycle, and an analog / digital (A / D) converter 5 digitizes the sampled and held analog input signal and outputs it to the next stage.

A spectrum analyzer using a phase locked loop (PLL) oscillation circuit 6 as a circuit for generating a local signal as shown in a circuit diagram of FIG. 4A is also known. In this analyzer, FIG.
As shown in the figure, the rising edge of the gate signal B is used as a frequency increment signal. When the frequency increment signal is input to the frequency divider 6d, the frequency divider 6d
Is the output of the local oscillator 6c (that is, the local signal LO).
Of frequency f _LO outputs a divide-by-N signal to the phase comparator 6a, a phase comparator 6a is the divide-by-N signal and the basic signal REF
And the signal determined by the phase difference is converted to an integrator 6
b (consisting of an operational amplifier 6b 'and a capacitor 6b ") to the local oscillator 6c.
In the same manner as described in (A), the A / D converter 5 samples and holds the analog input signal (mixer 2).
) Is digitized and output to the next stage.

However, in the above-described spectrum analyzer shown in FIG. 3A, since the frequency divider 6d and the phase comparator 6a as shown in FIG. Although the frequency sweep can be performed without a delay time, the local signal LO with high stability cannot be obtained. For this reason, there is a problem that various measurements with high accuracy cannot be performed. Further, in the spectrum analyzer shown in FIG. 4A, since the PLL oscillation circuit 6 is used for the circuit for generating the sweep signal, high stability and high precision measurement can be performed. 6d
And the response time τ of the PLL oscillation circuit 6 caused by the phase comparator 6a (see FIG. 4B: usually several tens to several hundreds μs).
c) There is a problem that an appropriate measurement cannot be performed for the burst signal A having a shorter active period. Further, in both the analyzers shown in FIGS. 3A and 4A, since the A / D converter 5 is not synchronized with the gate signal B, for example, as shown in FIG. The burst signal A having an active period shorter than the sampling period of the D converter 5 (the operation period of the S / H circuit 4 and the period of the sample trigger C in FIG. 5) cannot be measured with high stability and high accuracy. There is an inconvenience.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above problems. For example, in a spectrum analyzer, a pulse-like intermittent signal (burst signal) which becomes active for an extremely short period of time is provided. Burst signal measurement circuit and burst signal measurement that can measure with high stability and high accuracy
The purpose is to provide a method for determining

[0007]

SUMMARY OF THE INVENTION A burst signal measuring circuit according to the present invention comprises: a local signal generating means having a frequency increment function; a mixer for frequency-converting a burst signal from a signal source to be measured by a local signal from the local signal generating means; Analog-to-digital conversion means for digitizing an intermediate frequency signal based on the frequency-converted signal ( hereinafter referred to as A / D conversion), and exhibiting an active / inactive state in synchronization with the burst signal. Input a gate signal and
A predetermined period during the period when the gate signal is active
The sample trigger to the analog-to-digital conversion
Output to each stage to operate the analog-to-digital conversion means, and after outputting each of the sample triggers
A frequency increment signal is output to the local signal generation means.
Characterized in that it comprises a sample trigger circuit for inputting data. Here, a delay circuit may be provided on the side of the measured signal source of the sample trigger circuit. The burst signal measuring method of the present invention is applied to a burst signal from a signal source under measurement.
Mix the local signal and turn the burst signal into an intermediate frequency signal
Frequency conversion, sample and hold the intermediate frequency signal
A / D conversion is performed after the conversion . (A) The burst signal is synchronized with the burst signal.
During the active period, the intermediate frequency signal is
Perform sample hold, A / D conversion, and
Increments the frequency of the local signal after the hold operation, characterized in that intends make settings of the frequency of the local signal against the next sample-and-hold. In the burst signal measuring circuit of the present invention, a gate signal (usually a burst signal is generated by this gate signal) which exhibits an active / inactive state in synchronization with the burst signal is input. A / D immediately or after a predetermined time has elapsed
By outputting a sample trigger to the conversion means,
/ D conversion means performs sample and hold (that is, performs first sampling). During the period in which the gate signal is in the active state, the sample trigger circuit outputs a sample trigger at a predetermined period following the A / D conversion means, thereby performing a sample hold on the A / D conversion means. While the second, third,... Sampling is performed, a frequency increment signal is output to the local signal generating means after the output of each sample trigger. When the gate signal becomes inactive immediately after the A / D converter performs the first sampling, the sample trigger circuit does not allow the A / D converter to perform the second sampling. Of course.

When the increment signal is input to the local signal generating means, the local signal generating means increments the frequency of the output signal (local signal) by a predetermined value. Therefore, if the active period of the burst signal is long (that is, the width of the gate signal is wide) and sampling is performed a plurality of times during the period, the second
The frequency of the local signal input to the mixer at the time of sampling is generated based on the frequency increment signal already output after the sample trigger circuit causes the A / D converter to perform the first sampling. .
In this case, the frequency of the local signal input to the mixer at the time of the first sampling is such that the sample trigger circuit sends the last signal to the A / D conversion means during the active period of the previous burst signal (the ON period of the gate signal). It is generated based on a frequency increment signal output after sampling is performed.

If the burst signal has a short active period (that is, the width of the gate signal is narrow) and only one sampling is performed during the period, the frequency of the local signal input to the mixer at the time of the sampling is reduced. Is generated based on a frequency increment signal output after the sample trigger circuit causes the A / D converter to perform sampling on the immediately preceding burst signal. in this way,
In the present invention, when the A / D conversion means operates, the frequency setting of the local signal input to the mixer has already been completed, so that the response of the local signal generation means is always several tens to several hundreds of microseconds. Stable measurement is performed. If the intermittent cycle of the burst signal is shorter than the operation time of the A / D converter, and the next burst is input before the A / D conversion operation of a certain burst is completed, the sample / sample conversion is performed. The trigger circuit ignores the next burst signal. Specifically, the sample trigger circuit does not output a sample trigger to the A / D conversion means and does not output a frequency increment signal to the local signal generation means. Needless to say, in such a case, the sweep of the CRT display also stops.

[0010]

FIG. 1 is a basic circuit diagram showing an embodiment of a burst signal measuring circuit according to the present invention. The signal source under test 1 outputs a burst signal A to the mixer 2 and a gate signal B to the sample trigger circuit 3. Here, the gate signal B
Is a signal which exhibits an active / inactive state in synchronization with the burst signal A. The mixer 2 includes a burst signal A and a local signal (a signal of a frequency f _LO from a local oscillator 6c described later).
LO is input and the frequencies f _A , f of both signals A, LO
The signal of frequency f _IF is generated by synthesizing the _LO . When the measurement circuit of the present invention is applied to a spectrum analyzer, the frequency f _IF , f _A , and f _LO generally have f _IF =
There is a relationship of f _LO −f _A , and a band-pass filter, an amplifier and the like (not shown) are provided at the next stage of the mixer 2.

The sample trigger circuit 3 outputs a gate signal B
To output a sample trigger C to the A / D conversion means. Note that this A / D conversion means includes an S / H circuit 4
(In FIG. 1, it is composed of a switch 4a and a parallel capacitor 4b.) And an A / D converter 5. After outputting the sample trigger C, the sample trigger circuit 3 outputs a frequency increment signal D to a local signal generating means (in this embodiment, constituted by the PLL oscillation circuit 5). The PLL oscillation circuit 6 includes a phase comparator 6a, an integrator 6b (composed of an amplifier 6b 'and a capacitor 6b "connected in parallel with the amplifier 6b') to which an output signal of the comparator 6a is input, and an output of the integrator 6b. A voltage-controlled local oscillator 6c for outputting a local signal LO having a frequency f _LO according to a signal; and a frequency divider provided in a loop that feeds back from an output side of the local oscillator 6c to an input side of the phase comparator 6a. The frequency divider 6d receives the frequency increment signal D from the sample / trigger circuit 3, and outputs the output frequency of the local oscillator 6c every time the signal D is input. Is output to the phase comparator 6a, and the phase comparator 6a
a compares the reference signal REF with the phase of the signal from the frequency divider 6d, and outputs a signal corresponding to the phase difference to the integrator 6b.

Hereinafter, the burst signal measuring circuit having the above configuration will be described with reference to FIGS. 2 (A) and 2 (B). FIG. 3A shows a case where the activation period of the burst signal A is short, and FIG. 3B shows a case where the activation period is also long. First, a case where the active period of the burst signal A is short will be described. In this case, a gate signal B synchronized with the burst signal A as shown in FIG. 2A is input to the sample trigger circuit 3 of FIG. Usually, since the gate signal B generates the burst signal A, when the burst signal A is in the active state,
Gate signal B is also active. Sample trigger circuit 3 detects the start of the burst signal A1 shown in FIG. 2 (A) (i.e., rising edge of gate signal B1), S /
A sample trigger C is given to the H circuit 4. This allows
The S / H circuit 4 operates, and the A / D converter 5 converts an analog input signal into a digital signal and outputs it to the next stage. At this time, the frequency f of the local signal LO input to the mixer 2
_{Since L0} is f _L0 (0), the analog signal input to the A / D converter 5 is a signal based on the output signal of the mixer 2 (for example, a bandpass filter, an amplifier or the like in the case of a spectrum analyzer). After passing).

After giving the sample trigger C1 to the S / H circuit 4 as described above, the sample trigger circuit 3 outputs the frequency increment signal D1 to the frequency divider 6 of the PLL oscillation circuit 6.
d, and the frequency divider 6d feeds back to the phase comparator 6a a signal of a frequency N × f _LO obtained by dividing the frequency f _LO of the output signal LO of the local oscillator 6c by N. Phase comparator 6a
Compares the phase of the reference signal REF with the frequency N × f _LO , the comparison result is integrated by the integrator 6b, and the signal LO having a frequency corresponding to the output voltage of the integrator 6b is output from the local oscillator 6c. You. Then, the output frequency f _LO of the local oscillator 6c is incremented from f _LO (0) by the feedback loop via the frequency divider 6d until the N-divided signal of the output becomes equal to the phase of the reference signal REF. , F _LO (1). In FIG. 2A,
Since the active period of the burst signal A is short, the burst signal A1 becomes inactive before the sample trigger circuit 3 outputs the next sample trigger. Thereafter, the next burst signal A2 is output from the signal source 1 to be measured, the sample trigger circuit 3 detects the rising edge of the gate signal B2 synchronized with the signal A2, and outputs the trigger C2.
/ H circuit 4 is operated, and conversion by the A / D converter 5 is performed. At this time, the frequency f _LO of the local signal LO input to the mixer 2 is the above-mentioned f _LO (1). Similarly, each time the burst signal A3, A4,... Is output from the signal source under measurement 1, the output signal LO of the local oscillator 6c is sequentially output.
The frequency f _{LO of} is incremented. And A / D
The converter 5 converts the signal based on the output signal of the mixer 2 into an A / D signal.
Will be converted. At this time, the frequency f _LO of the local signal LO input to the mixer 2 is a frequency incremented immediately after the immediately preceding sampling. In addition, the intermittent cycle of the burst signal is short, and a certain burst signal (for example,
If the next burst signal (A2 in FIG. 2A) is input before the A / D conversion operation in A1) in FIG. 2A is completed, the sample trigger circuit 3 The next burst signal A2 is ignored. That is, the sample trigger circuit 3 does not output the trigger C2 to the S / H circuit 4 and does not output the frequency increment signal D2 to the frequency divider 6c of the PLL oscillation circuit 6 (that is, increments f _LO . No need to do that). In such a case, of course, the sweep of the CRT display (not shown) for displaying the spectrum or the like is also stopped.

Next, a case where the active period of the burst signal A is long will be described (see FIG. 2B). Again,
The trigger circuit 3 in FIG. 1 detects the start of the burst signal A1 at the rising edge of the gate signal B1 and triggers the S / H circuit 4 in the same manner as in the case where the active period of the burst signal A in FIG. C1, the S / H circuit 4 operates and A / H
The D converter 5 converts the analog input signal into a digital signal and outputs it to the next stage. At this time, the frequency f _LO of the local signal LO input to the mixer 2 is f _LO (0). In addition, the sample trigger circuit 3 operates as in the case of FIG.
After giving the trigger C1 to the / H circuit 4, the frequency increment signal D1 is output to the frequency divider 6d of the PLL oscillation circuit 6, and f _LO (0) is incremented to f _LO (1).
In the case of FIG. 2B, since the active period of the burst signal A is long, the sample trigger circuit 3 sequentially outputs triggers C2, C3,... 5 are performed continuously. At this time, mixer 2
The frequency f _LO of the local signal LO input to the
This is the frequency incremented by the increment signal D output by the trigger circuit 3 after the output of the previous sample trigger C. Therefore, sample trigger C
After the output of 2, C3, ..., the frequency increment signal D
Each time 2, D3,... Are input to the frequency divider 6d, the frequency f _LO of the local signal _LO is sequentially incremented to f _LO (2) and f _LO (3).

Since the burst signals are not stable at the beginning of the active period of each of the burst signals A1, A2,..., The sampling timing of the S / H circuit 4 is too early, and an appropriate A / D In some cases, conversion cannot be performed. In such a case, for example, a delay circuit can be provided on the signal source under measurement 1 side of the sample trigger circuit 3 . In the above embodiment, the local signal generating means
Although the PLL oscillation circuit 6 is used, the local signal generating means is
For example, it may be configured by a sweep signal generation circuit whose voltage changes stepwise every time an increment signal is input, and a voltage controlled oscillator. In particular, when high-precision measurement is required, it is preferable to use the PLL oscillation circuit 6 shown in FIG. 1 as the local signal generating means. Further, the measurement circuit of the present invention is particularly preferably used for a spectrum analyzer, but is also effectively used for measuring a burst signal with a network analyzer or an impedance analyzer.

[0016]

As described above, the present invention has the following advantages. (1) Using the gate signal of the signal source to be measured,
By synchronizing with the trigger, the width of the gate signal, which was conventionally measurable, can be reduced from several tens to several hundreds μsec to 1 to 2 μsec.
Could be shortened to (2) When a PLL oscillation circuit is used as the local signal generating means, highly stable and highly accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a measuring circuit of the present invention.

FIG. 2 is a diagram showing signals in the circuit of FIG. 1;
(A) shows the case where the active period of the burst signal is short, and (B)
Is a diagram showing the same case.

FIG. 3A is a diagram illustrating a conventional measurement circuit that does not use a PLL oscillation circuit, and FIG. 3B is a diagram illustrating signals in the measurement circuit.

FIG. 4A is a diagram illustrating a conventional measurement circuit using a PLL oscillation circuit, and FIG. 4B is a diagram illustrating signals in the measurement circuit.

FIG. 5 is a diagram for explaining a conventional inconvenience in which proper measurement cannot be performed because the timing of A / D conversion does not match a burst signal.

[Explanation of symbols]

Reference Signs List 1 signal source under test 2 mixer 3 sample trigger circuit 4 S / H circuit 5 A / D converter 6 PLL oscillation circuit 6a phase comparator 6b integration circuit 6c local oscillator 6d frequency divider A burst signal B gate signal C sample Trigger D Frequency increment signal f _LO local oscillation frequency LO local signal

Claims (8)

(57) [Claims] 1. A local signal generating means having a frequency increment function, a mixer for frequency-converting a burst signal from a signal source to be measured by a local signal from the local signal generating means, and an intermediate based on the frequency-converted signal. frequency
A burst signal measuring circuit including an analog-to-digital converter for digitizing a signal (hereinafter referred to as A / D conversion) , wherein a gate signal exhibiting an active / inactive state in synchronization with the burst signal is inputted. And when the gate signal is in the active state.
The Ana sample trigger at a predetermined cycle during the between
The analog-to-digital conversion means is operated by outputting to the log-to-digital conversion means,
.After outputting the trigger, the local signal generating means
A burst signal measuring circuit comprising a sample trigger circuit for outputting an increment signal . 2. The method according to claim 1, wherein the sample trigger circuit receives
After the active period of the gate signal ends,
Last frequency corresponding to last generated sample trigger
Outputting a number increment signal to the local signal generating means.
In the next burst signal.
First, the analog-to-digital conversion
The intermediate frequency signal A / D converted by the stage is
Set by the last frequency increment signal
Frequency conversion according to the output frequency of the local signal generating means
2. The burst signal measuring circuit according to claim 1, wherein the signal is an intermediate frequency signal . 3. The gate of the sample trigger circuit.
A delay circuit is provided at the signal input.
3. The burst signal measurement according to claim 1 or 2,
circuit. 4. The sample trigger circuit according to claim 1, wherein
During the current active period of the burst signal
Before the A / D conversion operation of the
When the next active period is input, ignore the next active period
The sample trigger and the frequency increment
And outputting no reset signal.
The burst signal measurement circuit according to claim 3. 5. The method according to claim 1, wherein a burst signal from the signal source under test is
Frequency of 該Ba paste signal into an intermediate frequency signal by mixing the signal
Number conversion, sampled and held the intermediate frequency signal
A method of measuring a burst signal for A / D-converting the burst signal later, wherein: (a) synchronizing with the burst signal,
During the active period, the intermediate frequency signal is
Perform sample hold, A / D conversion, and
Increments the frequency of the local signal after the hold operation, the burst signal measurement method comprising providing a row cormorants step setting of the frequency of the local signal against the next sample-and-hold. 6. An end period of the burst signal is completed.
The sample hole made at the end of the activation period
To set the frequency of the last local signal after
Therefore, the next sample period starts and the first sample
To set the frequency of the local signal for
The method according to claim 5, further comprising a step.
The burst signal measurement method described above. 7. Starting from the start of an active period of said burst signal.
Delay for a predetermined time period before the sample
6. A field operation is started.
The burst signal measuring method according to claim 6. 8. A method according to claim 1, wherein said burst signal has a current activation period.
A / D conversion of the sampled and held signal
If the next activation period is entered before the end, the next
Ignore the signal included in the active period and sample and hold
Do not perform the operation and the frequency increment of the local signal.
8. The method according to claim 5, wherein
The burst signal measurement method according to claim 1.