JPS60227534A - Interference wave detecting system - Google Patents

Abstract

PURPOSE:To clear the counting content of pulse signals at every specific time to evade automatically interference by detecting from a received signal that a communication signal is modulated at a carrier wave and counting pulse signals during the period other than the period during which the communication signal is modulated by using the detecting output. CONSTITUTION:A received signal from an input terminal (in) is made into pulse form at a pulsing circuit 1 and the output of the circuit 1 is inputted in one side of an AND circuit 3. A clock signal fM is inputted in one side of another AND circuit 12 and a signal indicating that a communication signal detected at a line- engagement detecting circuit 8 is modulated is inputted in the other side of the circuit 3. Outputs of the circuit 3 and 12 are respectively inputted in counters 5 and 13 and the output of the counter is inputted in an FF7. The FF7 is cleared with the output of the counter 13 and, at the same time, the output of the counter 13 is inputted in an FF14. By clearing the counter 13 by means of the FF14 and the content of the counter 5 at every specific time, the interference of an input signal is automatically evaded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting that a beat of two carrier waves is included in a received signal of a radio receiver. In particular, the present invention relates to an interference wave detection method suitable for a mobile radio communication system that performs multi-frequency switching connections without providing a central control station.

An example of this type of mobile radio communication system is the cordless telephone system. As illustrated in FIG. 1, MuII! Connector A
, B, Oh are each connected to the telephone, and each corresponds to the corresponding Mu Ili! It is connected to telephones A', B/, and cl via a wireless line. If individual frequencies are assigned to each of these wireless lines, mutual interference will not occur in principle, but in order to make effective use of frequencies, it is necessary to use a small number of frequencies in common. .

Karitrap, now for these three sets of wireless connection devices and wireless telephones, two sets of transmitting and receiving frequencies (f, f1' and f2, f2')
It is assumed that the configuration is such that all the devices are configured to be able to use these two sets of frequencies. While wireless connection device A and wireless telephone A' are using frequencies f, , f, ', when wireless connection device B and wireless telephone B' are about to start using frequencies f4. When f,' is found to be used, another frequency f2, f2' is automatically set.
Switch to and set up the wireless line.

At this time, when the wireless connection device C and the wireless telephone C' try to start using it, it is detected that the image frequencies f1, t, I and f2, f2' are in use, and the line connection becomes impossible. You will have to wait until one becomes available.

If a large number of such systems are installed on public communication network terminals,
Wireless connection device belonging to another group and wireless telephone D'
However, a line may be set up using frequencies f1, r, and I. There is no problem if this is a faraway place where it does not cause interference, but if the wireless telephone A' moves and approaches the wireless connection device, mutual interference will occur. At this time, it is desirable that the wireless connection device automatically detect interference and switch to another available frequency. This requires a method for automatically and accurately detecting the occurrence of interference.

The present invention was made against this background, and an object of the present invention is to provide a method that can automatically detect the occurrence of interference from the reception output of a radio receiving device.

Generally, when two carrier waves designated with the same frequency cause interference, the difference between the two carrier wave frequencies appears as a beat in the received signal. Since this becomes an envelope signal of the carrier wave, this beat can be detected by demodulating the received signal of the radio receiver.

Generally, when a received signal is demodulated and the received signal is not receiving a communication signal (for example, during a call), noise appears in the received signal. This noise is, for example, background noise on the transmitting side, and as another example, noise generated in a wireless device or a wireless line. Therefore, it is not possible to distinguish between noise and the beat by simply measuring the level of this received signal, but from the demodulated signal of this received signal,
By providing a short time lag and detecting the correlation between signals during that time, noise and beats can be distinguished. That is, since a beat is basically a continuous signal of a sine wave, the same state continues before and after a short period of time, but since noise is random, there is no correlation before and after a short period of time.

The present invention detects beats by detecting this correlation, and detects that carrier frequencies are causing interference.

The demodulation of the received signal here is amplitude demodulation, which can clearly obtain the envelope signal of the carrier wave as its output.
Even if the type of demodulation circuit of the receiver is frequency modulation (FM) demodulation or phase modulation (PM) demodulation, beats of interference waves are often obtained in the demodulation output, and even if this is used, Can detect interference.

That is, the present invention provides means for obtaining a pulse signal corresponding to an envelope signal of a carrier wave detected from a received signal, means for detecting that a communication signal is modulated from the received signal to the carrier wave, and a detection output of this means. means for counting the pulse signals at a time other than the time when the communication signal is modulated using the means; means for clearing the counting contents of this means at specific time intervals; The present invention is characterized by comprising means for determining that the count content of the counting means is below a certain value.

Preferably, the specific time is a time when the accumulation of time other than the time during which the communication signal is modulated reaches a certain value.

Hereinafter, the present invention will be explained in more detail using embodiment drawings.

FIG. 2 is a circuit configuration diagram of an embodiment according to the method of the present invention. The signal given to the leftmost button in the diagram is received by the radio receiver,
This is a demodulated audio frequency band signal. This input signal is applied to a pulse forming circuit 1 to be pulsed, and its output is applied to an input N of a counter 5 via an AND circuit 3. Since this output OUT is fed back to its own inhibit input CI, when the - output rises, the output is maintained until a signal is input to the clear input OL. This output is given to the input of the D-type flip-flop 70, and its inverted output page becomes the interference detection output out.

On the other hand, the signal of the input in is branched and given to the busy detection circuit 8. This busy detection circuit 8 is composed of a peak detection circuit 9 and a comparison circuit 11 that compares the output level with a reference value given from a resistor voltage divider circuit 10, and the peak level of the signal in the audio frequency band is When the value exceeds a certain value, it is considered busy.

The output of this busy detection circuit 8 is output from AND circuits 3 and 12.
Given to 0 input. A clock signal f8 is applied to the other input of the AND circuit 12. This output is input to the input IN K4 of the counter 13, and its output is applied to the clock input OF of the flip-flop 7 and the input D of the flip-flop 14.

The clock signal of this flip-flop 14 is applied to each clear input CTJ of cxK#t counters 5 and 13. ``If this configuration corresponds to the claims, the means for obtaining the pulse signal is the pulsing circuit 1, the means for detecting that the communication signal is modulated is the busy detection circuit 8, and the means for obtaining the pulse signal is the busy detection circuit 8. The gate circuit 3 and the counter 5 are the means for clearing the data, and the counter 13 and the flip-flop 14 are the means for clearing the data at specific time intervals. Further, the means for determining is a 7-rig flag 7 which inputs the carry output of the counter 5.

The operation of the circuit configured as described above will be explained with reference to the operation waveform diagrams shown in FIGS. 5 and 4. The leftmost symbols in FIGS. 6 and 4 are waveform diagrams of points with corresponding symbols marked with an X in FIG. 2. FIG. 3 shows a case where no interference occurs, and FIG. 4 shows a case where interference occurs.

First, in the case of Fig. 3, when there is no interference, the input in signal (0) contains background noise and noise from the communication device,
When this is compared with the zero level from the pulse generator IK, fine random pulses are obtained as shown in FIG. 5(1). In Fig. 5, from Pl to P2, the call voice is modulated, and the output (8) of the busy detection circuit 8 (at the time of detection,
0”, becomes “1” when not detected), the AND circuit 3
Station 12 is out of service. Therefore, from Pl to P2
However, the output (1) of the pulsing circuit 1 is counted by the input counter 5, counted up to P3, and the output signal (5) is sent out.

On the other hand, the counter 13 similarly counts the clock signal fH over a period of time 'r, 10T2, and when it counts up, the output signal (13
) is sent. At this time, if the flip-flop 7 determines the presence or absence of the signal (5) and finds that the counter 5 has already counted up, the output QK changes to the signal (5).
7) is not sent.

Next, when interference occurs in the case of Fig. 4, the input i
The signal (0) of n has a periodic beat, which is pulsed by the pulse generator 1 and becomes a signal with a long period as shown in FIG. M4 (1). Even if this is counted by the counter 5 over the time T, +T4, it will take a considerable time for KFi to count up, and the counter 13 will count up first and send out the output ()3). At this time, since there is no DKFi signal input to the flip-flop 7, the flip-flop 7 is inverted and output enabled, and sends out a signal (7) to notify that there has been interference.

As described above, according to the present invention, it is possible to obtain a method that can automatically detect the occurrence of interference from the reception output of a radio receiving device. This method has a relatively simple configuration and is suitable for implementation in mobile devices. If automatic frequency switching is controlled by the detection method according to the present invention, a mobile radio system that can automatically avoid interference can be obtained.

The system of the present invention is particularly effective when implemented in combination with an automatic frequency switching device in a cordless telephone.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a cordless telephone system. FIG. 2 is a circuit configuration diagram of an embodiment of the present invention. FIGS. 6 and 4 are operational waveform diagrams. 1...Pulsing circuit (means for obtaining a pulse signal) 5...
- Counter (means for counting) 7... Flip-flop (means for determining) 8... Busy detection circuit (means for detecting that the communication signal is modulated) 13... Counter, 14... Flip-flop (means of clearing). Patent applicant's representative patent attorney outing Circular x 8゜Figure 1

Claims (1)

[Scope of Claims] (Li) In a method for detecting that interference has occurred in a carrier wave by detecting that a received signal of a radio receiver includes a beat due to two carrier frequencies, means for obtaining a pulse signal corresponding to an envelope signal of a carrier wave; means for detecting that a communication signal is modulated from the received signal to the carrier wave; and means for detecting that the communication signal is modulated using the detection method of the means. means for counting the pulse signal at a time other than the time when the pulse signal is counted; means for clearing the counting contents of the means at specific time intervals; and means for clearing the counting contents of the counting means at a certain time when the clearing signal is sent from the means. (2) An interference wave detection method comprising means for determining whether the specific time is the time when the accumulation of time other than the time when the communication signal is modulated reaches a certain value 1). (3) An interference wave detection method according to claim 1, wherein the envelope signal is an envelope signal of an intermediate frequency signal. (4) An interference wave detection method according to claim 1, wherein the envelope signal is an envelope signal of an intermediate frequency signal. An interference wave detection method according to claim (1), wherein the interference wave detection method is an audio signal.