JPH0687543B2 - Interference signal elimination method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an interference signal canceling method in a diversity receiving system, and in particular, it can restore normal operation when interference signal canceling control becomes impossible. The present invention relates to an interference signal cancellation method that is made possible.

[Prior Art] In a diversity receiving system, N (usually N = 2) receiving antennas are spatially spaced apart from each other, and interference among received signals including interference signals from these antennas occurs. There is an interference signal elimination method in which the interference signals are canceled by canceling the interference signals by performing signal coupling after equalizing the levels (amplitudes) and making the phases opposite to each other. In this method, for example, when the received signal is a PSK (Phase Shift Keying) wave, an error signal (reference signal) is obtained by taking the difference between the demodulated signal and the judgment value, and the error signal is divided into the signal wave and the interference wave. It is general to control the level and the phase of the signal including the interference signal of the receiving system for each antenna independently by using the fact that the difference signal is used to minimize the error signal.

FIG. 2 is a system block diagram for implementing a conventional interference signal canceling method in this type of diversity receiving system.

In FIG. 2, signals with the same signal source and combined interference waves during propagation are received by the first and second receiving antennas 1 and 2, respectively, and the first and second frequency conversion circuits 11 and 12 are received. At 12 each intermediate frequency (IF) is always converted.

After that, the first and second amplitude / phase control circuits 13 and 14 control the amplitude and phase of the received signal in the IF band using the error signal 21 from the demodulator 16, and the combiner 15 controls both. Combine the system signals. After this combination, demodulator 16 demodulates. Further, the demodulator 16 is adapted to generate the error signal 21 corresponding to the difference between the signal wave and the interference wave, as described above.

[Problems to be Solved] In the above-described conventional method, when the error signal corresponds to the interference signal, the first and second amplitude / phase controllers 1
Control is performed to cancel the interference signal at 3,14, but once the interference wave becomes large at one time, once,
If the control is lost and the correspondence between the error signal and the interference signal is lost, the control by the first and second amplitude / phase controllers 13 and 14 becomes impossible, and the output cannot be obtained.

Therefore, an object of the present invention is to provide an interference signal canceling method that can obtain stable reception operation without disabling control of interference signal canceling even when the interference condition becomes large.

[Means for Solving the Problems] In order to solve the above problems and achieve the object, the present invention arranges N (2 or more or more) transmission signals including interference signals spatially arranged at a distance from each other. (Natural number) Diversity method that receives signals with more than two receiving antennas and cancels the interference signals by canceling out the interference signals by using the difference in the amplitude and phase of the transmission signal and the interference signal between these receiving antennas. In step 1, the reference signal is obtained based on the demodulated signal after the interference signal is removed, and it is detected by this reference signal that the interference signal removal control cannot be performed. It is characterized in that it is prevented from being introduced into the device for a predetermined time and then released.

[Embodiment] An embodiment of an interference signal removing method according to the present invention will be described below.
Description will be made with reference to the system block diagram shown in FIG. 1 in which the same parts as those in FIG.

FIG. 1 is a system block diagram for implementing the method of the present embodiment, for example, in the case of a PSK wave as a form of a received signal, showing a diversity receiving system using two receiving antennas.

In FIG. 1, reference numerals 1 and 2 denote first and second receiving antennas that constitute a diversity receiving system.
The received signal including the interference signal received in 2 is converted to the IF band by the first and second frequency converters 11 and 12, respectively, and is converted to the IF band by the first and second amplitude / phase controllers 13 and 14, respectively. The signal is combined by the combiner 15 after the amplitude and the phase are adjusted. The combined signal is demodulated to PSK by the SPK demodulator 16,
The demodulated signal is output from the terminal 3 to the outside.

Here, the PSK demodulator 16 outputs an error signal as a reference signal indicating the difference between the interference signal component and the original signal component, which is given to the first and second amplitude / phase controllers 13 and 14. Adjust the amplitude of the interference signal to cancel the interference signal,
And the phase is adjusted. Further, this error signal is input to the level detector 17 for level detection,
When the level exceeds a predetermined level (when the interference temporarily increases and the control to cancel the interference signal becomes impossible)
Then, the timer circuit 18 is started and a command is given to the PS (power supply) controller 19 so that the first and second frequency converters 11 and 12 are simultaneously supplied with power O
Control is performed such that the power is turned on again when the operation of the timer circuit 18 is completed (timer off) by turning off N and off. That is, if the error signal exceeds a predetermined level, the IF output is disconnected and connected.

The above-described structure operates as follows.

That is, when the interference temporarily increases and the control for canceling the interference signal by the reference signal 21 to the first and second amplitude / phase controllers 13 and 14 becomes impossible, the level detector 17 is Operate. As a result, the timer circuit 18 is activated, and the first and second frequency converters are passed through the PS (power supply) controller 19.
11.12 and 12 are turned on and off at the same time, and IF output is disconnected and connected. That is, the two receiving antennas 1, 2
When the vector sum of the signals passed through is larger than the vector sum of the interference wave, the error signal corresponding to the interference wave appears, and the error signal can be used to restore the normal operation.

The above-described operation is performed not only once but until the level detector 17 becomes normal (the detection level is lower than the predetermined level).

Although the diversity receiving system using two receiving antennas is described in the above embodiment, the interference signal of the reception signal for each antenna is also applied to the diversity receiving system using three or more receiving antennas. It is possible to carry out the same operation as above by detecting the level.

Further, in the above embodiment, the timer circuit 18 is activated by using the error signal level, but it is also possible to use an out-of-frame alarm signal, a check bit alarm signal or the like of the demodulated data instead of the error signal.

Furthermore, in the above-mentioned embodiment, the method of controlling the PS (power supply) controller 19 for connecting and disconnecting the signal is adopted.
It can be replaced by a coaxial switch.

[Advantages of the Invention] As described above, the interference signal elimination method according to the present invention detects the level of a reference signal such as an error signal and connects / disconnects the signal when the level is equal to or higher than a predetermined level. There is an effect that the interference removal circuit can be stably operated by adding the circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example. 1,2: Receiving antenna 11,12: Frequency converter 13,14: Amplitude and phase controller 15: Combiner, 16: PSK demodulator 17: Level detector, 18: Timer circuit 19: PS (power supply) controller

Claims (1)

[Claims] 1. A transmission signal including an interference signal is received by at least N (natural number of 2 or more) receiving antennas spatially spaced from each other, and the transmitting signal and the interference signal between these receiving antennas are received. In the interference signal elimination method in the diversity reception system that cancels the interference signal by canceling out the interference signal by using the difference in the amplitude and the phase, the reference signal is obtained based on the demodulated signal after the interference signal is removed. It is characterized by detecting that the control of the interference signal removal is disabled by the signal, and by this detection, the signal before the interference signal removal is prevented from being introduced to the subsequent stage for a predetermined time and then released. Interference signal elimination method.