JPH0313002A - Broad band signal fetch circuit - Google Patents

Abstract

PURPOSE:To eliminate distortion of a signal by utilizing a coil forming a tuning filter as a signal fetch transmission line in a low frequency area when the tuning filter is not in use and using the tuning filter to fetch a signal in a high frequency area when the tuning filter is in operation. CONSTITUTION:Semiconductor switches 30, 31 area provided to switch a YIG tuning filter 21 into the active and inactive state. When a sawtooth voltage inputted to a switch control circuit 32 is a reference voltage VC or below as shown in figure, the semiconductor switches 30, 31 are controlled to be in the OFF state. Thus, the YIG tuning filter 21 is controlled to be inactivated and coils 23, 24 simply act like signal transmission sources. When the sawtooth voltage exceeds the reference voltage VC, the switch control circuit 32 outputs a negative voltage as shown in figure B, and the semiconductor switches 30, 31 are controlled to be in the ON state to connect connecting points A, B to a common level with respect to a high frequency. Then the YIG tuning filter 21 is active and each frequency component of a signal inputted to an input terminal 20A is selectively fetched in tuning with the frequency sweep of a spectrum analyzer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a wideband signal acquisition circuit that can be used in an input circuit of a measuring instrument such as a spectrum analyzer.

A spectrum analyzer captures a signal by sweeping the frequency from a low frequency region including a direct current component to a high frequency region where a magnetic resonance element can resonate, and displays the frequency components of the captured signal.

FIG. 4 shows a conventional wideband signal acquisition circuit. In the figure, 10 indicates a spectrum analyzer. As is well known, the spectrum analyzer IO has a frequency mixer 11, a local oscillator 12, and an intermediate frequency amplifier 13 at its input stage, and these three constitute a frequency selection circuit. In other words, a frequency sweep signal is applied from the local oscillator 12 to the frequency mixer ll,
The frequency sweep signal causes the frequency mixer 11 to sweep the mixed frequency, and the intermediate frequency amplifier 13 selects and takes in only the signal having the intermediate frequency.
The signal input to 0A can be frequency swept and captured.

The frequency-swept and captured signal is detected and displayed on the display 14, which depicts the distribution of frequency components contained in the signal. 15 indicates a sawtooth wave generator. The sawtooth wave output from the sawtooth wave generator 15 is applied to the local oscillator 12, and the oscillation frequency of the local oscillator 12 is frequency swept.

Although the spectrum analyzer 10 can operate alone in this way, for example, when measuring spurious characteristics, the frequency selection characteristics are insufficient, so the signal acquisition circuit 20 is connected to the front stage of the spectrum analyzer 10, and this signal acquisition circuit 20 for 2. Selection and incorporation using strict selection characteristics is being carried out.

The signal acquisition circuit 20 is provided with an '/IG tuning filter having a steep selection characteristic. YIC, a tuning filter, uses a small sphere made of a single crystal magnetic material as a magnetic resonance element 22, and includes this magnetic resonance element 22, two coils 2324 magnetically coupled to this magnetic resonance element 22, and the magnetic resonance element 22.
and a magnetic field generator 25 that applies a DC magnetic field to the magnetic field.

The magnetic resonance element 22 has a characteristic of resonating with a small amount of energy when a DC magnetic field is applied thereto, and the resonant frequency changes by changing the DC magnetic field. Therefore, by applying a sawtooth wave to the magnetic field generator 25 and linearly changing the DC magnetic field in an increasing direction, it is possible to sweep the resonant frequency in the frequency axis direction.

For example, 2 coil claws are attached to either one of the two coil claws 23 and 24
By applying a human signal to 3, the magnetic resonance element resonates when the frequency component included in the input signal matches the resonance frequency of the magnetic resonance element, and a signal at the resonant frequency can be extracted to the output coil 24.

Although the YIG tuning filter 21 operates for frequencies of 500 MHz or higher, the magnetic resonance element 22 does not resonate for signals of 500 MIIZ or lower. For this purpose, changeover switches 26 and 27 are provided, and the spectrum analyzer 10
When sweeping the frequency band below 500MHz, switch the selector switches 26 and 27 to contact B, and connect the input terminal 20A.
The structure is such that a signal given to the spectrum analyzer 10 is inputted to the spectrum analyzer 10 through a low-pass filter 28.

The selector switches 26 and 27 are the spectrum analyzer 10
When the sweep frequency is 500 MHz or less, contact B is selected, and when the sweep frequency enters a band of 500 MIIz or more, contact A is selected. In this way, a wide band signal is captured, and for signals with a frequency of 500 Mflz or higher among the captured signals, the signal is selected with a steep selection characteristic by the YIG tuning filter 21, and a highly pure signal is obtained. It is configured in such a way that it can be accessed.

Problems to be Solved by the Invention As has been accomplished, conventionally, the signal acquisition circuit 20 is provided with changeover switches 26 and 27, and the changeover switches 26 and 27 change the band of the acquired signal.

The changeover switches 26 and 27 are coaxial type switches whose impedance is matched to the transmission line for high frequency signals. This coaxial switch uses a mechanical contact switch such as a reed relay as a switching element, so if the switching operation is performed in synchronization with the frequency sweep of the spectrum analyzer 10, there is a limit to its lifespan. This creates the inconvenience of having to replace the switch.

For this reason, it is possible to replace the changeover switches 26 and 27 with semiconductor switches, but it is difficult to match the impedance of the semiconductor switches with the line impedance. Furthermore, it is difficult to construct the changeover switches 26 and 27 using semiconductor switches because there is also the drawback that the waveform of the low-frequency signal is distorted when passing through the semiconductor switch.

The purpose of this invention is to provide a highly reliable wideband signal acquisition circuit using a YIG tuned filter, which has a long service life for the changeover switch and does not cause waveform distortion. be.

"Means for Solving the Problem" In this invention, a semiconductor switch is provided to switch the YIG tuned filter between an operating state and a non-operating state, and when the YIG filter is not operating, the coil constituting the YIG tuning filter is switched to receive a low frequency signal. The YIG tuning filter is used as a transmission line for taking in signals, and when the YIG tuning filter is in operation, it is configured to take in signals in the high frequency range through the tuning filter.

According to the configuration of the present invention, the semiconductor switch is provided to switch the YIG tuning filter between operation and non-operation,
For this reason, the structure does not allow signals to directly pass through the semiconductor switch.

Therefore, according to the present invention, no distortion is imparted to the signal by the semiconductor switch. However, since it is a semiconductor switch, its lifespan is semi-permanent, and a highly reliable wideband signal acquisition circuit can be provided.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In Figure 1,
Parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and redundant explanation thereof will be omitted, but in the present invention, a semiconductor switch 30, 31 is provided for switching the YIG tuning filter 21 between an operating state and a non-operating state.

This example shows a case where diode switches are used as the semiconductor switches 30 and 31. In other words, semiconductor switches 30 and 3 made of diodes are connected between one end of each of the coils 23 and 24 constituting the Y/G tuning filter 21 and the common potential.
1 and a capacitor are connected, and the output terminal of the switch control circuit 32 is connected to the connection point between the semiconductor switches 30 and 31 and the capacitor.

The semiconductor switches 30 and 31 have anodes connected to the coils 23 and 2.
4, and the cathode is connected to a common potential point through a capacitor.

The switch control circuit 32 can be configured by, for example, a voltage comparator. That is, the reference voltage source 33 is connected to one input terminal of the operational amplifier constituting the voltage comparator, and the sawtooth wave output from the sawtooth wave generation circuit 15 is applied to the other input terminal. By selecting a polarity-inverting input terminal as the input terminal that provides this sawtooth wave, the switch control circuit 32 outputs a negative voltage when the sawtooth wave voltage becomes higher than the voltage of the reference voltage source 33, as shown in FIG. Output. The semiconductor switches 30 and 31 are controlled to be in the on state by this negative voltage. By controlling the semiconductor switches 30 and 31 to be in the on state, one end of each of the coils 23 and 24 constituting the YIG tuned filter 21 is connected to a common potential at a high frequency, and the YIG tuned filter 21 is controlled to be in the operating state. .

Coils 23 and 24 forming the YIG tuning filter 21
A low-pass filter 28 is connected between connection points A and B where the semiconductor switches 30 and 31 are connected.

With this configuration, when the sawtooth wave voltage input to the switch control circuit 32 is equal to or less than the reference voltage V shown in FIG. 2, the semiconductor switches 30 and 31 are controlled to be in the OFF state. By turning off the semiconductor switches 30 and 31, the YIG tuning filter 21 is turned off. In this d state, coil 2
3 and 24 simply act as signal transmission sources, and the input terminals 2O
A coil 2 a - contact La B - low pass filter 28
- connection point A - the thread path of the coil 24 is formed, and the input terminal 2
The signal input to the OA is input to the input terminal 10A of the spectrum analyzer 10 through this thread.

The voltage of the sawtooth wave is the reference voltage ■ shown in Figure 2. 2, the switch control circuit 32 outputs a negative voltage as shown in FIG. 2B. This negative voltage turns on the semiconductor switches 30 and 31, connecting the connection points A and B to a common potential for high frequencies.

Therefore, the YIG tuning filter 21 is in an operating state, and can selectively take in each frequency component of the signal input to the input terminal 2OA in tune with the frequency sweep of the spectrum analyzer 10. The frequency position at which the semiconductor switches 30 and 31 switch from the off state to the on state is determined by the reference voltage source 3.
3 voltage■.

It can be arbitrarily selected by adjusting.

Therefore, according to the present invention, the YIG tuned filter 21 can be switched from an inactive state to an active state at any frequency position in the frequency sweep, and can be switched between a state in which signals in the low frequency range are taken in and a state in which signals in the high frequency range are taken in. It is possible to switch to a state where the

In this case, in particular, the semiconductor switches 30 and 31 operate to switch whether or not to connect one end of each of the coils 23 and 24 to a common potential point, and are not structured to pass the signal taken into the spectrum analyzer 10.

As a result, the signal fed to the spectrum analyzer is not distorted and the accuracy is not degraded.

Further, since the semiconductor switches 30 and 31 are used, even if the number of switching operations increases, the initial state can be maintained semi-permanently, and a highly durable signal acquisition circuit can be provided.

FIG. 3 shows a modified embodiment of the invention.

In this embodiment, the spectrum analyzer 10 is provided with a low frequency mixer 11A and a high frequency mixer 11B, and the other end of the coil 23 is connected to the input terminal 20A of the low frequency mixer 11A. A case is shown in which a series circuit consisting of a semiconductor switch 30 and a capacitor is connected between and a common potential point.

When the semiconductor switch 30 is off, the YIG tuning filter 21 is inactive, and the signal input to the input terminal 20A is input to the low frequency mixer 11A provided in the spectrum analyzer 10 through the low pass filter 28.

When the semiconductor switch 30 is on, the YIG tuning filter 21 is in an operating state, and the signals corresponding to each frequency component of the input signal induced in the coil 24 are sent to the high frequency mixer J.
Input to IB.

A switching circuit 40 is provided on the output side of the two frequency mixers 11A and IIB.
The intermediate frequency output from the intermediate frequency amplifier 13 is selected and inputted to the intermediate frequency amplifier 13.

In this case, since the frequency of the input signal is low, the low frequency mixer llA converts the frequency into the sum of the frequency of the local oscillation signal provided from the local oscillator 12 and the frequency of the input signal.

Therefore, the frequency of the signal passing through the switching circuit 40 is
Since the frequency is higher than the frequency of the low-frequency signal input to A, even if a semiconductor switch is used in the switching circuit 40, the signal will not be distorted.

"Effects of the Invention" As described above, according to the present invention, the YIG filter 2
By switching the YIG tuned filter 21 between active and inactive states, the coil constituting the YIG tuned filter 21 is simply used as a signal transmission line for low frequency signals in the inactive state, and high frequency signals are extracted through the YIG tuned filter 21 when in operation. Because of this structure, the semiconductor switch 30 or 31 is not inserted in series in the signal transmission path. Therefore, the low frequency signal can be input to the spectrum analyzer 10 without being distorted.

Further, since the switching is performed by the semiconductor switches 30 and 31, the life is semi-permanent, and a highly efficient wideband signal acquisition circuit can be provided.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram for explaining the invention in detail, Fig. 3 is a connection diagram showing a modified embodiment of the invention, and Fig. 4 is a connection diagram showing an embodiment of the invention. FIG. 2 is a connection diagram for explaining a conventional technique. lO; spectrum analyzer, 11. IIA. 11B two-frequency mixer, 12: local oscillator, 13: intermediate frequency amplifier, 15: sawtooth wave generator, 20: signal acquisition circuit, 21: YIG tuning filter, 2゛2: magnetic resonance element, 23, 24: Coil, 30:31: semiconductor switch.

Claims (1)

[Claims] (1)A. In a wideband signal acquisition circuit that acquires a signal by sweeping the frequency from a low frequency region to a high frequency region where a magnetic resonance element can resonate, B. A semiconductor switch is provided in a tuned filter using a magnetic resonance element, and the tuned filter is operated by turning on and off the semiconductor switch.
When the tuning filter is not in operation, the coil constituting the tuned filter is used as a transmission line for acquiring signals in the low frequency range, and when the tuning filter is in operation, the tuning filter is configured so that it can be switched to a non-operating state. A wideband signal acquisition circuit configured to capture signals in the high frequency range using a filter.