JPH0212061B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a noise detection device for a vehicle that accurately detects reception interference noise emitted from a vehicle to prevent reception interference in a radio or the like.

As a conventional vehicle noise detection device, for example,
There is one shown in Fig. 1, which includes a detection antenna 1 that is installed near the engine 8 and detects noise emitted by the own vehicle, and a wide band that amplifies the noise signal of the detection antenna 1 and outputs it as a gate pulse signal 7. An amplifier 2, a receiving antenna 3 provided outside the vehicle, a receiving circuit 4 that processes the received signal from the receiving antenna 3 and outputs an audio signal, a speaker 6 that emits audio based on the audio signal, and a gate. It has a noise removal circuit 5 that holds the received signal when the pulse signal 7 is input to prevent noise from being mixed into the audio signal.

In the above configuration, when ignition system noise is generated, the wideband amplifier 2 outputs the gate pulse signal 7 upon detection by the detection antenna 1, so the noise removal circuit 5 holds the received signal, and the received signal with superimposed noise is block the passage of Therefore, since it is possible to prevent noise from being mixed into the audio signal, reception interference due to ignition system noise can be prevented.

However, according to the conventional vehicle noise detection device, since the detection antenna 1 is only provided near the engine 8, the spark voltage is approximately
Although it is possible to detect ignition system noise with a high field strength that occurs during ignition that reaches up to 10kV, for example, switching noise generated from the voltage regulator that controls the battery charging current,
As with the noise generated when various electrical components are turned on and off, the voltage change is as small as about 12V, and the distance to the detection antenna 1 is relatively large, so the amount of radiation to the antenna 3 is small. There is a risk that it may not be possible to completely prevent reception interference by detecting this type of noise (to completely detect this type of noise, multiple detection antennas must be installed, which may result in high costs) ).

The present invention has been made in view of the above,
To provide a vehicle noise detection device which inputs a noise signal from a vehicle harness in order to prevent reception interference by accurately detecting reception interference noise emitted from a vehicle without increasing costs.

The vehicle noise detection device according to the present invention will be explained in detail below.

FIG. 2 shows a noise detection section according to an embodiment of the present invention, which includes a high-pass filter 30 having a capacitor 10 and a resistor 11, and a detection diode 12.
and a time constant circuit 40 having a resistor 13 and a capacitor 14, and is connected to the vehicle harness by an input terminal 9 (which may be connected to the power supply terminal of the receiver) electrically connected to the vehicle harness. The superimposed noise is detected and a noise signal is output from the output terminal 15. Capacitor 1 of high pass filter 30
0 and resistor 11 are for noise that does not interfere with reception, for example, noise with a long cycle of 10 μS (for example,
The cutoff frequency is set to sufficiently attenuate the spike noise that occurs when switching phases when rectifying the three-phase output of the alternator, and the resistance value of the resistor 11 is set to be equal to the impedance of the power supply harness at frequencies above the cutoff frequency. set to the value. The capacitance value of the capacitor 10 is set based on the cutoff frequency set in this way and the resistance value of the resistor 11. For example, the frequency of noise that does not cause reception interference is approximately
If the frequency is 100 kHz, the cutoff frequency of the high-pass filter 30 will be approximately 10 MHz in order to sufficiently attenuate this to, for example, 40 dB or more. Therefore, 10M
Since the high frequency impedance of the power harness at frequencies higher than Hz is about 100Ω, the resistance 1
1 is set to about 100Ω, and capacitor 10 is set to C
= 1/2π _c R ( _c is the cutoff frequency), which gives 150pF. Furthermore, the values of the resistor 13 and capacitor 14 of the time constant circuit 40 determine the rise and fall times of the noise signal output from the output terminal 15. This rise time is set so that it can respond sufficiently to the rise of input noise, and
The fall time is set according to the input conditions of the amplifier, comparator, etc. connected to the output terminal 15.

In the above configuration, the operation will be explained with reference to FIG. 3A, B, and C as follows. Figure 3A shows the noises 16 to 25 superimposed on the power supply harness and the noise signal 15 output to the output terminal 15.
6 is a battery voltage of approximately 12V, which fluctuates in a square wave shape according to the current change accompanying the opening and closing of points on the primary side of the ignition system, and 17 is a ripple voltage when rectifying the three-phase AC output of the alternator, which ranges from several 100 μS to several It has a period of mS, 18 is the spike noise that occurs when the phase changes when the three-phase AC output of the alternator is rectified, and has a relatively long period of about 10 μS (Figure 3 B), and 19 to 25 are the voltages. This is spike noise that occurs irregularly when switching regulators and turning on and off various electrical components.
Numerals 6 and 27 are spike noises generated by sparks on the secondary side of the ignition system, and the noises 19 to 27 have frequencies of several 100 kHz to several 100 MHz (FIG. 3C) and cause reception interference. Noise 16~
18 does not cause reception interference and is sufficiently attenuated by the high-pass filter 30, but noise 1
After signals 9 to 27 are rectified by the detection diode 12, the rise and fall times are determined by the time constant circuit 40 and outputted from the output terminal 15 as the noise signal 15. The noise removal circuit 5 (FIG. 1) is activated by the noise signal 15, and when the noise signal 15 is output, the reception signal of the reception circuit 4 (FIG. 1) is held to prevent reception interference. Note that "on" and "off" in FIG. 3A indicate on and off of the primary side point of the ignition system.

As explained above, according to the vehicle noise detection device according to the present invention, since the noise signal is inputted from the vehicle harness, it is possible to accurately detect reception interference noise emitted from the host vehicle without incurring high costs. Reception interference can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional vehicle noise detection device. Figure 2 is a circuit diagram showing an embodiment of the present invention, Figure 3A shows noise superimposed on a vehicle harness, Figure 3B shows noise that does not interfere with reception, and Figure 3C shows reception. Indicates disturbing noise. Explanation of symbols, 1...Antenna for noise detection, 2...
Wideband amplifier, 3... Receiving antenna, 4... Receiving circuit, 5... Noise removal circuit, 6... Speaker, 30...
High-pass filter, 40...time constant circuit.

Claims (1)

[Scope of Claims] 1. A device that holds the signal level of a received signal when a noise detection unit detects noise and blocks passage of a reception signal mixed with noise, wherein the noise detection unit is configured to superimpose a signal on a vehicle harness. 1. A noise detection device for a vehicle, characterized in that the noise is directly input from the harness, and the noise in a frequency band that causes reception interference is output as a noise signal. 2. The detection unit according to claim 1, wherein the detection unit includes a high-pass filter that passes noise in a frequency band that causes reception interference, and a time constant circuit that determines the rise and fall times of the output of the high-pass filter. Vehicle noise detection device.