JP2582097Y2 - Spectrum analyzer with tracking generator - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrum analyzer, and more particularly to a spectrum analyzer having a tracking generator.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a conventional spectrum analyzer having a tracking generator.

The analysis frequency signal f _RF included in the measurement signal
Frequency converter 201 to which the intermediate frequency signal f _IF
The frequency converter 206, the band-pass filter 207, the detection circuit 209, and the display circuit 210 to which are input are provided in series. The frequency converter 201 has an analysis frequency signal f
A sweep signal output from the signal distributor 202 is input in addition to _RF , and these intermediate frequency signals _fIF are output to the frequency converter 206.

The intermediate frequency signal f
_In addition to the _IF , a signal output from the fixed frequency oscillator 211 is input, and these are mixed to form an intermediate frequency signal which is a detection frequency signal of the detection circuit 209. The intermediate frequency signal is input to the detection circuit 209 via the band-pass filter 207, and the detection output of the detection circuit 209 is input to the display circuit 210 and used as a display signal of a display device (not shown) indicating the measurement result. .

The sweep signal output from the signal distributor 202 is
Generated by the sweep signal generator 208 and the voltage controlled oscillator 204. The sweep signal generator 208 outputs a signal whose voltage value changes, and the voltage control oscillator 204 outputs a frequency signal f _LO according to the output voltage value of the sweep signal generator 208 to the signal distributor 202. The signal distributor 202 converts the input frequency signal f _LO into the frequency
1 and a frequency converter 20 constituting a tracking generator section together with the fixed frequency oscillator 205.
Output to 3.

The frequency oscillator 205 outputs a tracking generator output frequency signal f _TG by mixing the frequency signal f _LO from the signal distributor 202 with the frequency signal f _TGOSC output from the fixed frequency oscillator 205.

By using the fixed frequency oscillator 205 whose output frequency signal f _TGOSC is equal to the intermediate frequency signal f _IF output from the frequency converter 201,
The tracking output frequency signal f _TG output by the frequency converter 103 is equal to the analysis frequency signal f _RF . Also, when using those having a difference, the analysis frequency signal f _RF shall be tuned with a constant difference.

The output of the tracking generator is used as an input to a device under test such as a filter element. In this state, by observing the output of the device under test with a spectrum analyzer, the frequency characteristic of the device under test is measured. And transmission characteristics.

As described above, in the signal shown in FIG. 2, the tracking output frequency signal f _TG is the same as the analysis frequency signal f _RF of the spectrum analyzer or a signal tuned with a certain difference. The same voltage controlled oscillator 204 is shared by the spectrum analyzer unit and the tracking generator unit. In such a configuration, the tracking output frequency signal f _TG can be tuned to the analysis frequency signal f _RF , but the analysis frequency signal f _TG can be tuned.
It cannot be tuned to the Mth harmonic of _RF . Tracking output frequency signal f _{TG of} Mth harmonic and 1 / M frequency
Is required, a voltage controlled oscillator 302 having the same characteristics as the voltage controlled oscillator 204 and a voltage controlled oscillator 302 having the same characteristics as the voltage controlled oscillator 204 are output to the frequency converter 203 which outputs the tracking output frequency signal f _TG as shown in FIG. A voltage generator 301 for outputting a control voltage is provided, and the output of the voltage generator 301 is adjusted so as to output a tracking output frequency signal f _TG having an Mth harmonic and a frequency of 1 / M.

[0010]

[Devised Problems to be Solved] In a spectrum analyzer having a conventional tracking generator described above, the analysis frequency signal f _RF of M-th order harmonics and 1 / M
In order to obtain a tracking output frequency signal f _TG having a frequency of, a voltage controlled oscillator 302 having the same characteristics as the voltage controlled oscillator 204 is provided as shown in FIG. It is necessary to cover the Mth harmonic of the signal f _RF . For this reason, it is required to operate in a wide band, which is extremely expensive and has a problem that the manufacturing cost is increased. Further, it is necessary to determine the output of the voltage generator 301 so that the tracking output frequency signal f _TG becomes the one of the M-order harmonic or 1 / M frequency of the analysis frequency signal f _RF , and the operation is troublesome. is there. Furthermore, even if measurement is performed in advance and the output of the voltage generator 301 is determined, when a wideband signal is output, even a slight temperature change in the operating environment causes a large fluctuation in the output frequency. However, there is a problem that it can be used only in a limited operating environment.

The present invention has been made in view of the above-mentioned problems of the prior art, and has been made in consideration of the M-order harmonics of the signal frequency applied to the device under test and the 1 / M frequency. A device capable of easily observing the characteristics, and a spectrum analyzer having a tracking generator capable of outputting a tracking output frequency signal f _TG having an M-order harmonic of the analysis frequency signal f _RF and a 1 / M frequency. It is intended to be realized at low cost.

[0012]

SUMMARY OF THE INVENTION A spectrum analyzer having a tracking generator according to the present invention has a sweep signal generator for outputting a ramp signal and a frequency changed in accordance with the ramp signal output from the sweep signal generator. First
A first voltage-controlled oscillator that outputs a sweep signal of
A spectrum analyzer having a tracking generator having a signal distributor that outputs a first sweep signal output from the voltage-controlled oscillator to each of a spectrum analyzer unit and a tracking generator unit.
An amplifier circuit that receives a ramp signal output from a sweep signal generator and amplifies the signal at a predetermined magnification, a changeover switch that switches the output state of the amplifier circuit, an offset circuit that generates a predetermined voltage, a changeover switch output and an offset An adder for adding a circuit output, a second voltage-controlled oscillator for outputting a second sweep signal whose frequency is changed in accordance with the output of the adder, a signal distributor output and a second voltage-controlled oscillator output. A tracking generator section is constituted by the frequency converter to be mixed.

In this case, the amplification factor in the amplifier circuit may be variable.

The configuration of the amplifying circuit for performing the above-described variable amplification includes a plurality of amplifiers having different amplification factors and a changeover switch for selecting one of the plurality of amplifiers or selecting none of the plurality of amplifiers. It may be composed of

According to another configuration of the present invention, a sweep signal generator for outputting a ramp signal and a first sweep signal having a frequency changed in accordance with the ramp signal output by the sweep signal generator are output. Spectrum analyzer comprising: a first voltage-controlled oscillator that performs a first sweep operation, and a signal distributor that outputs a first sweep signal output from the first voltage-controlled oscillator to each of a spectrum analyzer unit and a tracking generator unit. , The ramp signal output from the sweep signal generator is compared and input.
A phase comparison unit for inputting as a frequency signal of a force voltage, a changeover switch for switching an output state of the phase comparison unit, an offset circuit for generating a predetermined voltage, and an adder for adding the changeover switch output and the offset circuit output When,
A second sweep whose frequency is changed according to the output of the adder;
And a frequency synth together with the phase comparator.
The tracking generator section may be constituted by a second voltage-controlled oscillator constituting a sizer, and a frequency converter for mixing the output of the signal distributor and the output of the second voltage-controlled oscillator .

[0016]

The output (tracking output frequency signal f _TG ) of the second voltage-controlled oscillator is obtained by mixing the first sweep frequency signal and the second sweep frequency signal. Can be expressed only by the analysis frequency signal and the amplification factor of the amplifier circuit.

Since the above-mentioned signals are obtained from the outputs of the respective voltage-controlled oscillators, the voltage-controlled oscillator provided in the tracking generator section does not require much broadband characteristics.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In this embodiment, the spectrum analyzer section includes the frequency converters 101 and 106 and the signal distributor 10.
2. Voltage-controlled oscillator 10 as first voltage-controlled oscillator
4. Bandpass filter 107, swept signal oscillator 10
8, a detection circuit 109 and a display circuit 110.

Signal distributor 102, voltage controlled oscillator 104
And the sweep signal oscillator 108 is also used as a tracking generator section, and is provided in addition to these.
A tracking generator section is constituted by the frequency converter 103, the 1 / N, N multiplying circuit 121 which is an amplifier circuit, the offset circuit 122, the voltage controlled oscillator 123 which is a second voltage controlled oscillator, the switch 124, and the adder 125. I have.

The frequency converters 101 and 106 to which the analysis frequency signal f _RF is input, the band pass filter 107, the detection circuit 109, and the display circuit 110 are provided in series.
The frequency converter 101 receives a sweep signal output from the signal distributor 102 in addition to the analysis frequency signal f _RF , and outputs the intermediate frequency signal f _IF to the frequency converter 106.

The intermediate frequency signal f
_In addition to the _IF , a signal output from the fixed frequency oscillator 111 is input, and these are mixed to form an intermediate frequency signal which is a detection frequency signal of the detection circuit 109. The intermediate frequency signal is input to the detection circuit 109 via the band pass filter 107, and the detection output of the detection circuit 109 is input to the display circuit 110 and used as a display signal of a display device (not shown) showing the measurement result. .

The sweep signal output from the signal distributor 102 is
Generated by the sweep signal generator 108 and the voltage controlled oscillator 104. The sweep signal generator 108 outputs a signal whose voltage value changes, and the voltage controlled oscillator 104 outputs a frequency signal f _LO according to the output voltage value of the sweep signal generator 108 to the signal distributor 102. The signal distributor 102 converts the input frequency signal f _LO into the frequency
1 and to the frequency converter 103.

The frequency converter 103 has a voltage controlled oscillator 1
The frequency signal f _TGOSC output from the reference _numeral 23 is input.
The frequency converter 103 receives the input frequency signals f _LO , f
Outputs a tracking output frequency signal f _TG is an intermediate frequency signal _TGOSC.

The output of the 1 / N, N multiplying circuit 121 is input to the adder 125 in accordance with the open / close state of the changeover switch 124, and the input and the offset circuit 122 for correcting the output characteristics of the voltage controlled oscillator 123 are added. And the outputs are added.
The voltage controlled oscillator 123 generates a sweep signal whose frequency is changed according to the output voltage of the adder 125, and outputs it to the frequency converter 103.

The 1 / N, N multiplying circuit 121 receives the ramp signal output from the sweep signal generator 108 and amplifies the ramp signal to a slope (amplitude) of the ramp signal applied to the voltage controlled oscillator 123. Is to change. The output of the 1 / N, N-fold circuit 121 is a switch 1
The fixed offset voltage output by the offset circuit 122 when the switch 24 is closed is added by the adder 125 and is added to the voltage controlled oscillator 122.

Next, the operation of this embodiment will be described.

When the changeover switch 124 is open, only a fixed offset voltage output from the offset circuit 122 is applied to the voltage controlled oscillator 123, and the output of the voltage controlled oscillator 123 has a fixed frequency. The signal f _TG is the same as the analysis frequency signal f _RF or a signal tuned with a certain difference as in the conventional example shown in FIG.

When the changeover switch 124 is closed, the offset frequencies of the voltage controlled oscillators 104 and 123 are set to f _offset , f ′ _offset ,
Assuming that a frequency component that changes according to the voltage of 123 is Δf, a control voltage applied to each is V, and an output frequency when the control voltage is 0 is f _START , f _LO , f _RF, f _TG , and f _TGOSC are Each is represented as follows.

Here, each of the above offset frequencies is represented by f
_{Of the offset} and f ' _offset , f' _offset is determined by a fixed offset voltage output from the offset circuit 122, and the analysis frequency signal f _RF and the tracking output frequency signal f _TG are set to a predetermined frequency by the offset voltage. The difference is kept.

F _LO = f _offset + V · Δf... F _RF = f _TG = V · Δf + f _START ... F _TGOSC = f ′ _offset + V / N · Δf. f _TG = f _LO −f _TGOSC ... From the above expressions, the expression relating to f _TG is developed.

F _TG = f _offset + V · Δf−f ′ _offset −V / N · Δf = (V−V / N) · Δf + f _offset −f ′ _offset = [(N−1) / N] · V · Δf + f _offset− f ′ _offset Therefore, by applying a voltage satisfying f _offset −f ′ _offset − [(N−1) / N] · f _START = 0, f _TG = [(N−1) / N] · V .DELTA.f + [(N-1) / N] _.fSTART = [(N-1) / N] _.fRF , and the analysis frequency signal _fRF can be multiplied by an integer or divided. By selecting the amplification factor of the N, N multiplying circuit 121, the tracking output frequency signal f _TG can be a signal of the Mth harmonic or 1 / M frequency of the analysis frequency signal f _RF .

In this embodiment, since the intermediate frequency signal between the voltage controlled oscillator 104 and the voltage controlled oscillator 123 used in the spectrum analyzer section is used as the tracking output frequency signal f _TG , the voltage controlled oscillator 123 has the configuration shown in FIG. Broadband formation was not required as in the conventional example shown, and the apparatus could be constructed at low cost.

In the embodiment described above, 1
The example in which one / N, N multiplying circuit 121 is provided has been described as an example. The 1 / N, N-fold circuit 121 has a variable amplification factor, and the amplification factor may be arbitrarily changed based on a command from a higher-level device for controlling the operation of the device. With such a configuration, various measurements can be continuously performed, and the device can be used efficiently.

As the variable amplification factor 1 / N, N multiplying circuit 121 as described above, the feedback resistor for determining the amplification factor may be constituted as a feedback amplifier having a plurality of resistors having different resistance values, or may be simply amplified. It is conceivable to provide a plurality of 1 / N, N times circuits having different rates. The changeover switch in this case is
Any one of the feedback resistors (1 / N, N-fold circuits) may be selected or none of them may be selected. With such a configuration, it is possible to obtain the tracking output frequency signal f _TG of the M-th harmonic and the 1 / M frequency of the analysis frequency signal f _RF only by the switching state of the switch.

As for the amplifying operation in the 1 / N, N-fold circuit 121, extremely high-precision operation is required, and it is necessary to synchronize with the output of the voltage controlled oscillator 104. A PLL frequency synthesizer that feeds back the voltage control oscillator 123 using the ramp signal output from the comparator 108 as a frequency signal of the comparison input voltage may be configured. With such a configuration, the above requirement can be easily achieved.

[0038]

[Effects of the Invention] Since the present invention is configured as described above, the following effects can be obtained.

[0039] In one described in claim 1 is realized by tracking the output frequency signal f _TG as the analysis frequency signal f _RF of M-th order harmonics and 1 / M inexpensive spectrum analyzer capable of outputting a signal of a frequency of There is an effect that can be.

According to the second or third aspect, in addition to the above effects, the tracking output frequency signal f _TG is converted into the analysis frequency signal f _RF by the switching state of the switch.
There is an effect that it is possible to switch to various M-order harmonics and 1 / M frequencies. According to the present invention, there is an effect that the amplification operation in the amplifier circuit can be performed with high accuracy and in synchronization with the first voltage controlled oscillator.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional example.

FIG. 3 is a block diagram showing a configuration of a conventional example for outputting a tracking output frequency signal f _TG having an M-order harmonic and a frequency of 1 / M.

[Explanation of symbols]

 101, 103, 106 Frequency converter 102 Signal distributor 104, 123 Voltage controlled oscillator 107 Band pass filter 108 Sweep signal generator 109 Detection circuit 110 Display circuit 111 Fixed frequency oscillator 121 1 / N, N times circuit 122 Offset circuit 124 Switching Switch 125 adder

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-296669 (JP, A) JP-A-62-235575 (JP, A) JP-A-57-166554 (JP, A) JP-A-57-166554 64171 (JP, A) JP-A-57-7655 (JP, A) JP-A-1-213006 (JP, A) JP-A-64-35386 (JP, A) JP-A-1-95676 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01R 23/173

Claims (4)

(57) [Scope of request for utility model registration] A sweep signal generator that outputs a ramp signal; a first voltage-controlled oscillator that outputs a first sweep signal whose frequency is changed in accordance with the ramp signal output by the sweep signal generator; The first voltage-controlled oscillator outputs the first
A spectrum analyzer having a tracking generator having a signal distributor that outputs a sweep signal of each of the spectrum analyzer section and the tracking generator section. An amplification circuit for amplifying, a changeover switch for switching an output state of the amplification circuit, an offset circuit for generating a predetermined voltage, an adder for adding the output of the changeover switch and the output of the offset circuit, and according to an output of the adder. A second voltage-controlled oscillator that outputs a second sweep signal whose frequency has been changed, and a frequency converter that mixes the output of the signal distributor and the output of the second voltage-controlled oscillator. Tracking generator Spectrum analyzer to Bei. 2. A spectrum analyzer comprising the tracking generator according to claim 1, wherein the amplification factor in the amplifier circuit is variable. 3. A spectrum analyzer comprising the tracking generator according to claim 2, wherein the amplifier circuit selects a plurality of amplifiers having different amplification factors and one of the plurality of amplifiers. Alternatively, a spectrum analyzer including a tracking generator, comprising a changeover switch that does not select any of them. 4. A sweep signal generator for outputting a ramp signal, a first voltage-controlled oscillator for outputting a first sweep signal having a frequency changed according to the ramp signal output by the sweep signal generator, The first voltage-controlled oscillator outputs the first
A spectrum analyzer having a tracking generator having a signal distributor for outputting the sweep signal of each of the above to a spectrum analyzer section and a tracking generator section, a ramp signal output from the sweep signal generator is compared with a comparison input voltage.
A phase comparison unit input as a pressure frequency signal, a changeover switch for switching an output state of the phase comparison unit, an offset circuit for generating a predetermined voltage, and an adder for adding the changeover switch output and the offset circuit output. , A second sweep whose frequency is changed according to the output of the adder.
And a frequency synth together with the phase comparator.
A tracking generator unit comprising a second voltage-controlled oscillator constituting a sizer, and a frequency converter for mixing the output of the signal distributor and the output of the second voltage-controlled oscillator. Spectrum analyzer.