JPH0142064Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to an information transmission oscillation circuit used as an information transmission device for point information, speed information, etc. in a train control device, and in particular, it is designed to operate at a specific frequency (constant oscillation frequency) at all times. The present invention relates to an information transmission oscillation circuit that oscillates and changes its oscillation frequency from a specific frequency to a frequency corresponding to the ground element when an onboard element such as an antenna is electromagnetically coupled to a ground element having a frequency different from the specific frequency.

Prior Art Information transmission oscillation circuits used in on-board devices such as variable-frequency automatic train stopping devices and automatic train operating devices are connected to an onboard device that is a receiving antenna installed at the head of a train,
This onboard element consists of an oscillator connected as a feedback circuit, which normally oscillates at a specific frequency of 0, and the onboard element is composed of a resonant circuit consisting of a coil and a capacitor provided on the ground side. When the onboard element is electromagnetically coupled with the ground element, the oscillation frequency changes to one of frequencies 1, 2,...n corresponding to the ground element, and when the onboard element is no longer electromagnetically coupled with the ground element, the oscillation frequency changes to the specific frequency 0 again. It's starting to oscillate.

As shown in FIG. 7, a conventional oscillator circuit for information transmission of this type has a transformer provided on the input side and output side of an amplifier to form an oscillator. By providing the input capacitor 30 to form a resonant circuit, the influence of noise input to the onboard element 7 forming a part of the oscillation circuit is removed, and the characteristics of the circuit (especially the SN ratio) are improved.
According to this oscillation circuit, the specific frequency 0 is
The inductance of the secondary coil of the onboard coil 7 and the cable 31 connecting the onboard coil 7 and the input transformer 1
inductance, distributed capacitance, input capacitor 3
0 and the inductance of the input transformer 1.

However, in such an oscillation circuit, the resonant frequency is determined not only by the inductance of the two coils constituting the onboard element 7 and the inductance of the primary coil of the input transformer 1, but also by the inductance and distributed capacitance of the cable 31. It is also influenced by For this reason, in the conventional oscillation circuit, the frequency characteristics change simply by changing the length and characteristics of the cable 31.

For this reason, a bandpass filter is provided on the input side of the amplifier to cut out frequency components on the low and high sides of the frequency band including the specific frequency 0 and each variable frequency frequency 1, 2,...n. An oscillator circuit has been proposed. However, in this oscillation circuit, if a filter element, especially a filter element corresponding to a specific frequency of 0, is missing, the oscillation circuit may oscillate at another frequency and may not be fail-safe.

Purpose of the invention The present invention can ignore the influence of changes in cable length and characteristics on the oscillation frequency, can significantly reduce the influence of noise, and can even be used when a filter element corresponding to a specific frequency is missing. The object of the present invention is to provide an oscillation circuit for information transmission in which oscillation stops.

Structure of the invention According to the invention, the above object is achieved by installing a comb-shaped filter which has a specific frequency and each variable frequency as its center pass band and whose attenuation is larger at each variable frequency than the specific frequency at the rear stage of the input transformer. This makes it possible to ignore the effects of changes in cable length and characteristics, and eliminates various noises.Moreover, when a filter element corresponding to a specific frequency is missing, the degree of coupling is reduced due to the difference in attenuation. This is achieved by causing the oscillation to stop.

Embodiments Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

The oscillation circuit shown in FIG. 1 includes an input transformer 1,
A comb filter 2, a phase shifter 3, a limiter 4, an amplifier 5, and an output transformer 6 are connected in that order to form an oscillator, and an onboard element 7, which is a receiving antenna, is connected to this oscillator as a feedback circuit. There is. In the following description, it is assumed that the relationship between the specific frequency 0 and each variable frequency frequency 1, 2,...n is 0<1<2<...<n.

The comb-shaped filter 2 has a so-called comb-shaped pass band that passes only the frequency components in the vicinity of the specific frequency 0 and each variable frequency frequency 1, 2,...n, and the output level of the specific frequency 0 is different from each other. The output level is configured to be higher than the output level of the variable frequencies 1, 2, . . . n.

As an example of such a comb-shaped filter 2 is shown in FIG. 2, coils L0, L1, L2, . . .
A filter element consisting of a pair of coil L0 and capacitor C0 for a specific frequency of 0 is created by using a filter element in which Ln and a pair of capacitors C0, C1, C2,...Cn are connected in series, and a resistor R that provides a level difference. Coils L1, which are provided between the terminals T1 and T3, respectively correspond to each variable frequency frequency 1, 2,...n.
Each filter element consisting of a pair of L2,...Ln and a capacitor C1, C2,...Cn is connected in parallel, and the filter element is connected in parallel with a filter element consisting of a pair of coil L0 and capacitor C0 via a resistor R. I can do it. The comb-shaped filter 2 configured as described above has terminals T1 and T2 connected to the secondary coil of the input side transformer 1, and terminals T3 and T4 connected to the secondary coil of the input side transformer 1.
may be connected to the input terminal of the phase shifter 3.

The attenuation characteristics of this comb filter 2 can be determined as shown in Fig. 4 by setting the values of each coil L0, L1, L2, ...Ln and each capacitor C0, C1, C2, ...Cn to arbitrary values. It is minimized at frequencies 1, 2, . Furthermore, the attenuation amount is configured to have a difference of N (dB) between the specific frequency 0 and the variable frequency frequencies 1, 2, .

The phase shifter 3 is a known circuit that sets the phase between input and output to zero when the oscillation frequency changes from a specific frequency 0 to variable frequencies 1, 2,...n and when it returns from the variable frequency to the specific frequency. For example, a circuit as shown in FIG. 3 can be used.

The phase shifter 3 shown in FIG. 1
2 and 14, and the collector of the transistor 17 is connected to the terminal 10 through a circuit consisting of a capacitor 19 and a resistor 20, and a circuit consisting of a coil 21, a resistor 22, and a capacitor 23. and terminal 11
An input signal is input to the base of the transistor 17 via the capacitor 25. In the phase shifter 3 configured in this manner, the terminals 11 and 12 may be connected to the output terminal of the comb filter 2, and the terminals 13 and 14 may be connected to the input terminal of the limiter 4.

The limiter 4 is a known circuit that slices the input signal at a constant level, and the amplifier 5, input transformer 1, output transformer 6, and onboard coil 7 are the same as those used in conventional oscillation circuits. .

This oscillation circuit normally oscillates at a specific frequency of 0 using a filter element consisting of a pair of coil L0 and capacitor C0, and when the onboard coil 7 passes over the ground coil, the oscillation frequency changes to the resonance frequency of the ground coil. The frequency changes to one of 1, 2,...n. When the frequency is changed in this way, among the filter elements consisting of the coil and capacitor pair of the comb filter 2,
The passage characteristics of the filter element according to the varied frequency are shown.

In this oscillation circuit, a filter 2 with a comb-shaped pass characteristic is provided before the amplifier 5, that is, after the input transformer 1, so there is no need for an input capacitor, which was conventionally installed in parallel with the primary coil of the input transformer. Therefore, the inductance, distributed capacitance, etc. of the cable become irrelevant to the resonant circuit of the input side transformer 1, and the influence of the length and characteristics of the cable on the oscillation frequency is significantly reduced. In addition, since the resistance R of the comb-shaped filter 2 makes the attenuation amount at each variable frequency frequency 1, 2,...n larger than the attenuation amount at the specific frequency 0, the coil L0, which is the filter element for the specific frequency 0, If the capacitor C0 fails, the oscillation conditions will not be satisfied because sufficient μ cannot be obtained, and the oscillation will therefore stop. Furthermore, the rising stability of the specific frequency 0 when the power is turned on is improved.

The comb filter shown in FIG. 5 has coils L0,
L1, L2,...Ln and capacitors C0, C1, C
2,...Cn pairs of filter elements connected in series are connected in parallel to terminals T1, T2 and T3, T4, and resistors R1, R2 with approximately the same resistance value are connected between adjacent filter elements from the second stage onwards. ,...Fn-1 are provided. In this comb-shaped filter, the resonance frequencies of the constant oscillation frequency 0 and variable frequency frequencies 1, 2, . . . n are determined by adjacent filter elements.
Therefore, in this oscillation circuit, each coil L0, L
1, L2,...Ln and each capacitor C0, C1, C
By setting the value of 2,...Cn to a predetermined value, the vicinity of the specific frequency 0 and each variable frequency frequency 1, 2,
...acts as a filter with comb-shaped transmission characteristics that passes only frequency components in the vicinity of n, and
The amount of attenuation at specific frequency 0 is determined by resistors R1, R2,...
Due to Rn-1, the attenuation characteristic shown in FIG. 4 is smaller than the amount of attenuation at each variable frequency frequency 1, 2, . . . n. Therefore, even when this circuit is used, if the filter element for the specific frequency 0 fails, the oscillation conditions will not be satisfied and oscillation will stop.

The comb filter shown in FIG. 6 is the comb filter shown in FIG. It is constructed in the same way as a filter. Therefore, this filter also has each coil L
0, L1, L2,...Ln, each capacitor C0, C
By setting the values of 1, C2, ...Cn and each resistor R1, R2, ...Rn to predetermined values, a filter having attenuation characteristics as shown in Fig. 4 can be obtained. When a filter element is missing, oscillation stops.

Effects of the invention As described above, this invention has a comb filter installed at the rear of the input transformer that passes only frequency components around a specific frequency and around each variable frequency. The oscillation frequency does not change, and the influence of noise can be significantly reduced. Furthermore, since the output level of the comb filter differs between the specific frequency and each variable frequency, oscillation will stop if the filter element for the specific frequency is missing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of an oscillation circuit according to the present invention, Fig. 2 is a diagram showing an embodiment of a comb filter used in the oscillation circuit, and Fig. 3 is an embodiment of a phase shifter. FIG. 4 is an explanatory diagram of circuit characteristics, FIG. 5 is a diagram showing another embodiment of the comb filter, FIG. 6 is a diagram showing still another embodiment of the comb filter, and FIG. , is a diagram illustrating a conventional oscillation circuit. 1...Input side transformer, 2...Comb filter, 7...Onboard element, 0...Specific frequency, 1,
2,...n...variable frequency.

Claims (1)

[Claims for Utility Model Registration] Constant oscillation at a specific frequency 0, and frequencies 1, 2,...n in which the onboard components are different from the specific frequency.
When electromagnetically coupled with a ground element with a resonant frequency of
The oscillation frequency is set to the resonance frequency 1 of the ground element,
In an information transmission oscillator circuit configured to change frequency to 2,...n, the specific frequency 0 and each variable frequency 1,...n
A comb filter 2 is provided at the rear end of the input side transformer 1, with a center pass band of 2,...n, and a larger attenuation amount for variable frequencies 1, 2,...n than for the specific frequency 0. An oscillator circuit for information transmission characterized by: