JPS637059B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase synchronization method for modulated signals used in a route diversity method in a mobile radio communication system.

By modulating and emitting the same signal from multiple base stations adjacent to each other using a carrier wave with the same frequency or offset by an appropriate value, the reliability of the received signal of mobile stations in the boundary area of each base station wireless zone is improved. In the so-called route diversity method, which aims to improve the efficiency, the technique related to phase control of the modulated signal plays the most important role in maximizing the effect of this method.

Conventionally, when controlling the phase of a modulated signal to maximize the effect of this route diversity system, a process of transmitting a signal from the base station to the center at an intermediate stage is essential, as will be explained in detail later.
However, the radio waves sent from this base station to the center may not be able to reach the center directly if the distance between the two is too large or if there is an obstacle on the way. It was necessary to install a relay station on the way, and depending on the method, it was also necessary to install another transmission line between the two stations. Furthermore, in order to adjust the phase of a certain base station, it is necessary to stop the transmitters of other base stations or prepare a transmitter with a different frequency, modulate it, and transmit it to the center. The drawback was that it did not.

Therefore, an object of the present invention is to easily adjust the phase of a base station in a route diversity system of a mobile radio communication system without particularly providing a relay station (or transmission path) for phase adjustment. The purpose of this study is to obtain a modulation phase synchronization method that can achieve this goal.

In order to achieve the above object, the present invention receives the radio waves emitted by its own station, takes the beat of radio waves from other stations, and synchronizes the modulation phase using this beat. It is something.

According to the present invention, in a wireless communication system in which radio waves frequency-modulated by the same modulation signal are simultaneously transmitted from a plurality of wireless base stations using the same wireless channel, each wireless base station transmits signals emitted by its own station and other stations. an antenna that receives radio waves from the radio channel; a receiver that demodulates the received radio waves; a wave generator that extracts a beat component by combining the received radio waves from the output of the receiver; and a modulated input signal of the own station. There is obtained a modulation phase synchronization method characterized by comprising means for changing the phase so that the output of the wave generator is minimized.

Next, a detailed explanation will be given with reference to the drawings.

Both FIG. 1 and FIG. 2 are diagrams showing configuration examples of conventional modulation phase synchronization systems. In FIG. 1, the same signal output from a central signal generation source 1 is supplied to a base station 4 through four variable phase circuits 2 and a transmission line 3 arranged in parallel, and is frequency-modulated from here. is emitted as a radio wave. The circled area represents the wireless zone. The emitted radio waves are received and demodulated by the central antenna 5 and receiver 6, and the phase of the demodulated output is compared with the signal from the signal source 1 by the phase comparator 7. This phase-compared signal allows the variable phase to be adjusted. The circuit 2 is controlled to adjust the phase of each base station 4 to a certain constant value. As explained above, this conventional method includes the process of receiving the radio waves of the base station 4 centrally during its operation, but the actual arrangement of the base stations is different from that described above. Furthermore, due to the distance between the two and obstacles along the way, it was sometimes necessary to provide a relay station along the way. Furthermore, as mentioned earlier, the phase adjustment of the base station has become complicated.

In the conventional example shown in FIG.
3 and reaches the base station 14. The base station is equipped with a switch 15, and when adjusting the phase, flip the switch 16 to the second transmission line 16 side.
It is returned to the phase comparator 17 in the center via this transmission line 16, and the phase is compared with the original signal from the signal generation source 11. Based on this result, the phase of the variable phase circuit 12 is changed to obtain a certain desired phase. I was getting it. However, in this method, not only is it necessary to provide the return transmission line 17, but there is also a condition that the phase fluctuations of the transmission lines 13 and 16 must be correlated so that when one changes, the other changes. On the other hand, in reality, there are cases where this correlation does not exist, so this method is problematic from a practical standpoint.

Next, in explaining the apparatus of the present invention, we will first explain what kind of receiver output can be obtained when two radio waves are received simultaneously. Let us now assume that the two radio waves are Aε ^j 〓 ^A (hereinafter referred to as radio wave A) and Bε ^j 〓 ^B (hereinafter referred to as radio wave B). However, both A and B are the amplitudes of radio waves, θ _A and θ _B are the phases of each radio wave, ε is an exponent, and j is an imaginary number. Therefore, the composite wave of both radio waves A and B is Aε ^j 〓 ^A +Bε ^j 〓 ^B = C _R ε ^j 〓 ……(1) However, C _R = {A ² +B ² +2ABcos(θ _A −θ _B )} ^{1 /2} It is expressed as φ in equation (1) indicates the phase of a composite wave of two radio waves, and therefore, when demodulated by a frequency demodulator, an output proportional to dφ/dt (t is time) is obtained.

Focusing on the n=1 component in equation (1), that is, B/Asin(θ _A - θ _B )...(2), we can see that the phase θ _A and the phase θ _B are the carrier angular frequency dθ _A / of the radio wave A. dt=2π From _A and frequency _A Δ
The carrier angular frequency dθ _B /dt = 2π ( _A + Δ) of the radio wave B that differs by the amount of and the respective frequency deviations are ΔF _A and ΔF _B , then
θ _A is the instantaneous frequency expressed by 1/2π・dθ _A /dt= _A ΔF _A and _A −ΔF _A ...(3), and θ _B is 1/2π・dθ _B /dt=( _A +Δ) + ΔF _B and ( _A + ∆) - ∆F _B (4). Therefore, the change in the frequency component, that is, the beat component of radio wave A and radio wave B, shown in equation (2) above is as follows:
The phase term (θ _A −θ _B ) in equation (2) is d(θ _A −θ _B )/dt=(ΔF _A +ΔF _B )−Δ, (−ΔF _A +ΔF _B )−Δ, and (−ΔF _A − ΔF _B )−Δ ……(5) indicates that it takes the following three values.

Figure 3 shows the two radio waves mentioned above and the instantaneous beat frequencies of these two radio _waves . The signal represents the instantaneous frequency of the radio wave B having the carrier wave _A +Δ as shown, and the signal represents the instantaneous frequency of the beat component of both radio waves shown in equation (5). Note that this signal is expressed as d(θ _A −θ _B )/dtΔF _A +ΔF _B or = if the relationship ΔF _A , ΔF _B ≫Δ holds between ΔF _A , ΔF _B and Δ. −ΔF _A +ΔF _B −Δ ...(6) This shows that it has the following frequency components.

Now, if we consider the case where the above equation (2) is frequency demodulated, the output is d/dt {B/A sin (θ _A - θ _B )} = B/A・d (θ _A - θ _B )/dt・cos(θ _A −θ _B )…
...(7), and the output is the amplitude ratio of both radio waves B/A
This shows that it is proportional to the difference in instantaneous frequencies as well as to the difference in instantaneous frequencies.

On the other hand, in FIG. 3, if we consider the case where the signals are synchronized in phase, as can be seen from the signals, the component ΔF _A +ΔF _B in equation (6) does not exist. That is, it shows that the amplitude B/A·d(θ _A −θ _B )/dt in equation (8) is the minimum.

In the above explanation, assuming that radio wave A is the radio wave of the own station and radio wave B is the radio wave of another station, the beat component of the sum of instantaneous frequency deviations F _A + F _B among the output components of the receiver with the frequency demodulator is By detecting this component and controlling the phase of the modulation signal of the own station so that the component is minimized, the phase can be synchronized with the surrounding modulation phases.

The above description has been made for the case where there are two radio waves, A and B, but this concept can be extended to the case where there are three or more radio waves. I will not express this mathematically, but as a result, if we detect the beat component generated by combining all radio waves and control the phase of the modulation signal of the own station so that this detected component is minimized, , the phase can be synchronized to the surrounding modulation phase.

Next, the configuration of the present invention will be explained.

FIG. 4 is a block diagram showing the configuration of an embodiment of the present invention, in which the phase of a modulated signal input via a transmission line 20 is controlled by an external control line 21 (described later).
a phase circuit 22 that can be varied by
, an antenna 24 for emitting the output of this transmitter into the air, an antenna 25 for receiving the output emitted from the own station and the output of the same radio channel emitted from surrounding stations, and demodulating this. and a bandpass filter 27 for extracting the beat component of the instantaneous frequency between each station.
An amplifier 28 for amplifying the component, a detector 29 for detecting the amplified component, and determining whether or not the output of the detector is the minimum, and if not, the phase shift circuit 22 to shift the phase in the direction of minimum, and the output line 21 (described earlier) of this judgment circuit.

Next, to explain the operation of the device shown in FIG. 4, radio waves of the same radio channel emitted from the own station and surrounding stations are simultaneously received by the antenna 25, demodulated by the receiver 26, and then passed through the bandpass filter 27.
The beat component of the instantaneous frequency of the composite wave of all stations, that is, the component of ΔF _A +ΔF _B is extracted, linearly amplified by the amplifier 28, detected by the detector 29,
It is input to the judgment circuit 30 as a DC output.

For example, the judgment circuit 30 applies a slight output fluctuation to the output line 21 so that the phase advances with respect to the phase shift circuit 22, tests whether the beat component output from the detector 29 increases in response to this, and determines whether the beat component output increases or not. If it increases, the phase is controlled to advance further, and if it increases, it is controlled to delay the phase, thereby controlling the output of the detector 29, that is, the beat component, to be minimized.

As mentioned above, with the configuration shown in Figure 4, by constantly adjusting the modulation phase of the own station with respect to the modulation phases of other surrounding stations, it is possible to avoid interfering with the normal operation of the system and to avoid special To provide a system that can synchronize the phase with other transmitting stations without requiring a transmission line.

Furthermore, when implementing the present invention, if all base stations have the above-mentioned phase adjustment function, there is a risk that the entire base station will drift in a phase synchronized state. There is a method of fixing the phase of a base station and synchronizing the phases of surrounding base stations using the phase-fixed base station as a reference.Furthermore, if a plurality of base stations simultaneously perform phase adjustment according to the present invention, Since there is a risk of synchronization with a base station that is in the process of phase synchronization, the implementation of the present invention is made more reliable by having each base station sequentially perform phase adjustment one by one by activation from the center. You can also do that.

[Brief explanation of the drawing]

1 and 2 are diagrams showing schematic examples of conventional wireless communication devices, and FIG. 3 shows two radio waves and the instantaneous frequencies of the beats of these radio waves to explain the principle of the present invention. FIG. 4 is a block diagram showing the configuration of one embodiment of the present invention. Explanation of symbols: 22 is a phase shift circuit, 23 is a transmitter,
26 is a receiver, 27 is a bandpass filter, 28
29 represents an amplifier, 29 represents a detector, and 30 represents a judgment circuit.

Claims (1)

[Claims] 1 In a wireless communication system in which radio waves frequency-modulated by the same modulation signal are transmitted simultaneously from multiple radio base stations using the same radio channel, each radio base station transmits radio waves of the radio channel emitted by its own station and other stations. a receiver that demodulates the received radio waves; a wave generator that extracts a beat component by combining the received radio waves from the output of the receiver; A modulation phase synchronization method characterized by comprising: means for changing the output so that the output thereof is minimized.