JP2787091B2 - Phase synchronization receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase synchronization radio receiver required for simultaneous multi-station transmission in a mobile communication system.

(Prior Art) In a mobile communication system, when a large area is covered by using a plurality of small wireless zones, a method of simultaneously transmitting radio waves of the same frequency from a plurality of wireless base stations installed in each small wireless zone is known. is there. It is called multi-station simultaneous transmission,
It is used for a wireless calling system, a car phone system, and the like.
This is described in Document 1 (“Basics of Mobile Communication” published by the Institute of Electronics, Information and Communication Engineers, Section 7.4, pp. 180-185).

At that time, the transmission quality is improved by the diversity effect at a distance from a plurality of radio base stations, that is, at a place where the intensity of the received radio wave is substantially equal, but if the phase shift of the signal transmitted from each radio base station becomes large, on the contrary, Transmission quality deteriorates. Therefore, when performing multi-station simultaneous transmission, it is essential to synchronize the phase of the signal transmitted from each base station.
For example, in a radio paging system, a transmission signal is transmitted from each radio base station via a station that transmits a signal from an exchange (hereinafter, referred to as a "central station"). It is necessary to measure the delay time of the transmission path between each of the base stations and adjust the signal delay so that the delay time is the same for all the wireless base stations. This situation is shown in FIG. 2 and FIG. FIG. 2 shows the line configuration of the radio paging system, and FIG. 3 shows the configuration of the base station.

As a method of delay adjustment, as shown in FIG. 2, the same signal is transmitted from the central station to a plurality of base stations, and the base station is modulated by the signal to be a reference wireless base station (hereinafter referred to as a “reference station”). ) Is transmitted to another wireless base station (hereinafter "peripheral station").
), And compares the phase with the signal sent from the central station via a wired transmission path, and adjusts the variable delay circuit of the base station to have the same phase. is there. In FIG. 2, in the case of a peripheral station that cannot directly receive the radio wave of the reference station, the phase of many base stations is adjusted by repeating the adjustment of the variable delay circuit with the peripheral station having the same phase as the reference station as the reference station. Can be matched. This is described in detail in Document 2 ("Automobile Telephone" published by the Institute of Electronics, Information and Communication Engineers, Section 7.5, pages 150 to 152). In addition,
At this time, the delay time between the central station and the reference station can be adjusted using the delay circuit in the peripheral station so that the delay time between the central station and the other peripheral stations is longer than the delay time between the central station and other peripheral stations. It is necessary to insert a fixed delay circuit between the base station and the reference station.

FIG. 4 (a) shows the configuration of the base station required for this. However, in this configuration, since the variable delay circuit is provided before the transmitter, a transmission phase error due to a variation in delay time of the transmitter of the base station cannot be removed.

To eliminate this, each base station also receives its own transmitted radio wave and adjusts the delay so that it synchronizes with the signal from the reference station. This is FIG. 4 (b), and the details are described in the above-mentioned document 2.

FIG. 4 shows the configuration of the conventional delay adjustment system and the signal transmission method.

FIG. 4 (a) is a configuration example in a case where the reception voltage of the reference station and the reception voltage of the peripheral station in the receiver installed in the peripheral station become equal even if the signal is received by the same antenna. The radio wave is received by one receiver, each radio wave is demodulated, and the delay time difference is measured by comparing the phase difference of the signal of each base station. At this time, since the frequency of the radio wave to be received is the same, while the radio wave of the peripheral station is stopped while the radio wave of the reference station is received as shown in FIG. By measuring the time difference between the special signals (the time difference between the reception of the special signal A and the reception of the special signal B), the ground detection time difference of the transmission line is equivalently measured. In addition,
As a method of stopping the radio wave of the peripheral station, the time difference between the special signal A and the special signal B is set to a fixed time α seconds, so that the peripheral station demodulates and decodes the radio wave transmitted from the own peripheral station and performs special processing. When the signal A is detected, it can be easily realized by stopping the radio wave of the local peripheral station after α seconds from the detection, and starting the transmission of the radio wave after the reception of the special signal B. In addition, the time difference (α−β) between the time difference β and α between the reception of the special signal A and the reception of the special signal B is the phase error.

For measuring the time, a method of obtaining a signal at a fixed time interval obtained by dividing a clock necessary for signal decoding, a method of counting the number of pulses cycled in the decoded signal, and the like are used.

(Problems to be Solved by the Invention) However, when there is a difference between the received voltage of the reference station and the received voltage of the peripheral station in the receiver installed in the peripheral station, it is necessary to make the sensitivity of the receiver different. As shown in FIG. 3 (b), it becomes necessary to provide a receiving antenna and a receiver for the transmitting antenna of each base station. For example, if there is a difference of several tens of dB between the received voltage from the reference station and the received voltage of the own station,
Due to such a large level, there is a disadvantage that accurate reception cannot be performed due to sensitivity suppression or the like.

For example, the conventional AGC receiver has problems in that the dynamic range of gain adjustment is not sufficient and that the response time is short.

An object of the present invention is to provide a phase synchronization receiver that solves these problems.

(Means for Solving the Problems) A feature of the present invention is that in a mobile communication system covering a wide area using a plurality of small radio zones, a signal is transmitted between a plurality of radio base stations installed for each small radio zone. In order to perform phase synchronization, in a receiver installed in a radio base station for receiving a reference station radio wave serving as a phase reference, a receiver decodes a predetermined special signal in the reference station radio wave. And a variable attenuator for attenuating the reference station radio wave, wherein the attenuation of the variable attenuator is switched immediately after the detection of the special signal by the decoding circuit or a predetermined time after the detection. Phase synchronization receiver.

(Operation) In the present invention, a variable attenuator for reducing the received voltage to a standard received voltage when the received voltage is high is inserted into the reception input of the phase synchronization receiver. The attenuation of the variable attenuator is large when the received voltage is high and small (or 0) when the received voltage is low, according to the decoded signal from the decoding circuit.
Is switched to Therefore, a receiver for phase synchronization having a wide dynamic range can be obtained.

(Example) FIG. 1 is a diagram for explaining an example of the present invention. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a receiver, which has a variable attenuation period 10a for attenuating a received radio wave and a receiving unit 10b. 12 is a phase comparator, which has a decoding circuit 12a and a phase comparison circuit 12b for decoding the received signal,
Phase difference information is obtained at the output of the phase comparison circuit 12b. The amount of attenuation of the variable attenuator 10a is determined by the decoding circuit 12a by the special signal A (fourth
After a predetermined time from the reception of the signal, the signal becomes smaller to receive the weak radio wave of the reference station, and when the special signal B is received, the attenuation is controlled to be larger.

The reference station's transmit power is 10W and the transmit / receive antenna gain is 5dB
i, the distance between the reference station and the surrounding stations is 10000 m, within the line of sight,
40dB coupling attenuation between transmitting and receiving antennas in the surrounding station,
Assuming that the wavelength of the radio wave to be used is 0.3 m and the input impedance of the receiver is 50 Ω, the reception voltage of the radio wave from the reference station at the output terminal of the reception antenna of the peripheral station is: 10log (10) + 5-20log (4 * π * 10000) /0.3)+5+10log(4*50)+120=50.5(dBμV) Received voltage due to radio waves from the peripheral station at the output terminal of the receiving antenna of the peripheral station = 10log (10) −40 + 10log (4 * 50) + 120 = 113.0 (dBμV) Therefore, it is necessary to receive a signal having a level difference of 60 dB or more when receiving a signal from a reference station and receiving from a peripheral station. As a method for realizing a receiver having such a wide dynamic range, the gain of the amplifier of the receiver is made variable and its output is made constant according to the reception input.
The AGC method is generally known, but this method has the above-mentioned problems.

In the case of the phase synchronization according to the present invention, as shown in FIG. 4C, the special signal A included in the radio wave from the own peripheral station is used.
The radio wave of the local station stops after a predetermined time α seconds from the reception of the radio signal, and the radio wave of the weak reference station is received.
As shown in the figure, an attenuator 10a for lowering the reception voltage to a standard reception voltage is added to the phase synchronization receiver, and the attenuator is activated α seconds after the detection of the special signal A included in the reception signal. By inserting an attenuator after receiving the special signal B, it is possible to easily obtain an appropriate reception input in synchronization with the transmission of radio waves from the transmitter of the local station.

That is, in FIG. 1, when the radio wave of the local station is normally received, the attenuator operates so that the reception voltage becomes a standard reception voltage. After the elapse of α seconds after the detection of the special signal A, the attenuation of the attenuator is reduced at the timing when the transmission of the radio wave from the local station is stopped, and the voltage level of the radio wave from the reference station is received at the standard voltage. It is to be.

Such a variable attenuator can be easily realized by changing the bias voltage of the PIN diode, and a decoder for detecting the special signal A and the special signal B for phase synchronization is necessary for measuring the phase difference. Since it is provided and does not need to be provided in the present invention, it can be realized economically.

(Effect of the Invention) As described above, the present invention controls the reception for phase synchronization with a wide dynamic range by controlling the attenuation of the attenuator provided in the receiver by the control signal from the originally required decoder. Machine can be realized economically. Accordingly, only one antenna system and one receiver are sufficient, regardless of the difference in the strength of the radio wave to be received.

[Brief description of the drawings]

 FIG. 1 is a block diagram of a phase synchronization receiver according to the present invention, FIGS. 2 and 3 are diagrams for explaining phase synchronization, and FIG. 4 is an explanatory diagram of conventional phase synchronization. 10; receiver, 10a; variable attenuator, 10b; receiving section, 12; phase comparator, 12a; decoding circuit, 12b;

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-52-15201 (JP, A) JP-A-1-300721 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 7/24-7/26 H04Q 7/00-7/38

Claims (1)

(57) [Claims] In a mobile communication system that covers a wide area using a plurality of small radio zones, a phase of a signal is synchronized between a plurality of radio base stations installed in each of the small radio zones. In a receiver installed in a radio base station for receiving a reference station radio wave serving as a reference, the receiver includes a decoding circuit that decodes a predetermined special signal in the reference station radio wave, and attenuates the reference station radio wave A variable attenuator, wherein the variable attenuator is configured to switch the amount of attenuation immediately after the detection of the special signal by the decoding circuit or after a predetermined time has elapsed from the detection. Characteristic receiver for phase synchronization.