JPS594297Y2 - Oscillation circuit for information transmission in trains and other vehicles - Google Patents

Description

[Detailed description of the invention] This invention relates to an oscillator circuit for information transmission in vehicles such as trains that uses a filter with phase linearity characteristics, and the length of the cable between the receiving antenna on the train and the oscillation circuit can be changed. The purpose is to prevent effects on the characteristics of the oscillation circuit.

The so-called frequency-variable automatic train stop (ATS) device is a device that loosely couples a part of the output of an amplifier AP to two on-board receiving antennas, as shown in Figures 1 and 2. An oscillation circuit that constantly oscillates at a constant oscillation frequency is configured by positive feedback to the input side through the coils 11 and 12, and a receiver circuit (not shown) that monitors changes in the oscillation frequency of the oscillation circuit is provided. It is mounted on a train, and furthermore, a resonant circuit RC, which is a ground element with a frequency different from the above-mentioned constant oscillation frequency, is arranged at a desired point on the track, so that the receiving antenna of the running train runs on this resonant circuit RC. When passing the vehicle, when the constant oscillation frequency of the oscillation circuit on the vehicle changes in the direction of the resonant frequency of the resonant circuit RC, the receiving circuit detects this change in frequency, thereby detecting the frequency change point and automatically This is a device that applies train braking to the train.

Therefore, an oscillation circuit for information transmission that changes the oscillation frequency in the direction of the resonance frequency of such a resonance circuit RC is an ATS.
It is widely used to detect not only the type of vehicle but also the state of the location where the vehicle is traveling.

In the oscillator circuit for information transmission of vehicles such as trains as described above,
Conventionally, in order to improve the characteristics of the circuit by eliminating the influence of noise received by the receiving antenna that forms part of the oscillation circuit, a circuit such as the one shown in the broken line block in Figure 1 has been used as part of the oscillation circuit. An input transformer T coupled to an amplifier AP of the configuration
A resonant circuit was constructed by connecting a capacitor C8 in parallel to the capacitor C8.

By the way, as shown in FIG. 2, this capacitor C8 is connected to two coils l1. l 2 inductance Ll, L2, a cable Cb connecting the receiving antenna to the input quadrature T and the amplifier AP.

Inductance L of C.

, L′. , the distributed capacitance of the cable △Co, △C′o,
Furthermore, it is related to the inductance L3°L4 of the primary coil and secondary coil of the human quadrangle T.

Therefore, when installing an automatic train stop device having the above-mentioned oscillation circuit on a train, the lengths of cables cb and c'b are may be significantly changed.

When the lengths of cables cb and c'b change, their inductance L.

, L'o and distributed capacitances ΔCo, ΔC'o, etc. change, and the resonant frequency of the resonant circuit with the capacitor C6 in the input capacitor T shown in FIG. 1 or 2 changes.

Therefore, the phase and amplitude characteristics of the oscillation circuit change, causing a constant change in the oscillation frequency and station shift sensitivity.

Therefore, in the past, the length of the cable was kept constant regardless of the type of train.

This means that the cable length must be matched to the vehicle type, which requires the maximum length, which generally results in surplus cables, and there is a problem in securing a place to accommodate the surplus cables.

In the present invention, the capacitor C6 is
This eliminates the effects of changes in cable length on the oscillation circuit, making it possible to almost ignore the effects on the oscillation circuit caused by changes in cable length.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a passband filter BPF, whose configuration is shown in FIG. FIG. 2 is a block diagram of a variable frequency oscillation circuit according to the present invention.

As illustrated in FIG. 4, the filter BPF includes resistive attenuators ATT1. to improve mismatched impedance. A.T.
It is configured by combining T2, a bypass filter HPF, and a low-pass filter LPF.

FIG. 5 is a characteristic curve diagram of the filter BPF, in which curve a shows the amplitude attenuation characteristic with respect to human frequency, and curve 2 shows the phase change characteristic with respect to frequency.

This phase characteristic is the cutoff frequency fC of the filter BPF.
1 and fC2, a linear phase change is shown, but at other times, the phase changes rapidly.

In the circuit of FIG. 3, the conventional resonant capacitor C6 connected to the input cadence T is removed and the above-mentioned filter BPF is connected, so that the cable Cb.

Inductance L of C'b.

, L'o and distributed capacitances △Co, △C'o, etc. are no longer directly related to the resonant circuit of the input quadrature T, which has already been eliminated, and moreover, compared to the phase rotation between the input and output of the filter BPF, the cable Since the phase change between the input and output of the cable due to changes in the length of cb and c'b is very small,
The phase characteristics of the oscillation circuit shown in FIG. 3 are approximately determined by the phase characteristics of the filter BPF.

Further, the variable frequency frequency band is a frequency band whose phase is within 90' on the Nyquist diagram of the oscillation circuit.

That is, to explain this using the characteristic diagram in Figure 5, if the cutoff frequency fC1 is the constant oscillation frequency of the oscillation circuit in Figure 3, the maximum variable frequency in this circuit is fC.
It is 2.

If the filter is designed to have phase linear characteristics, the frequency fc1
The phase difference θ between ~fC2 can be made small, and the entire passband can be made into a variable frequency band.

Therefore, when using a filter that does not have phase linear characteristics as shown in Figure 5, the phase change between input and output is large near the cutoff frequency, so only a part of the center of the passband can be used, resulting in noise. This cannot be practical from the viewpoint of improving characteristics.

As described in the above embodiments, the present invention removes the resonant capacitor conventionally connected to the input capacitor of the variable frequency oscillation circuit, and creates a phase linear characteristic between the frequencies that define the frequency band. By inserting a bandpass filter with a phase characteristic that approximately determines the phase characteristics of Furthermore, it has many effects such as contributing to improvement of noise rejection characteristics.

[Brief explanation of drawings]

Figure 1 is a partial circuit diagram of a conventional information transmission oscillation circuit with a resonant circuit installed in the input quadrature, Figure 2 is a conventional information transmission oscillation circuit diagram including an on-board receiving antenna and connection cable, and Figure 3 4 is a block diagram of an oscillation circuit for transmitting information in a vehicle such as a train, which is an embodiment of the present invention; FIG. 4 is an example of a bandpass filter configuration in the oscillation circuit; and FIG. 5 is a characteristic curve diagram of the filter. T...Input transformer, BPF...pass band filter, AP...amplifier.

Claims (1)

[Scope of utility model registration request] Constructing an oscillation circuit that constantly oscillates at a constant oscillation frequency by positively feeding a part of the output of the amplifier to the human quadrature of the amplifier via two loosely coupled coils of the on-board receiving antenna; In a variable frequency oscillation circuit, wherein when the receiving antenna faces a resonant circuit serving as a ground element having a frequency different from the constantly oscillating frequency, the constantly oscillating frequency changes in the direction of the resonant frequency of the resonant circuit. , removing the resonant capacitor connected in parallel to the human cadence of the amplifier, and providing a frequency band between the human cadence and the amplifier that includes at least the constant oscillation frequency and the resonant frequency, and a frequency shift in this band. An oscillation circuit for transmitting information in a vehicle such as a train, characterized in that a passband filter having a linear phase characteristic between input and output is inserted.