JP3034116B2 - Working spare switching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active / standby switching method for switching between an active transmitting circuit and a standby transmitting circuit.

[0002]

2. Description of the Related Art FIG. 6 shows an arrangement of a set-standby system of, for example, a microwave band digital radio apparatus. The set standby method is, as shown in this figure, a working standby switching method in which the outputs of the active transmitting circuit 10 and the standby transmitting circuit 12 are directly switched at high speed by a switch 14 such as a diode switch and transmitted to a wireless line. However, in this method, the quality of the wireless line cannot be often secured at the moment of switching.

[0003] For this reason, the set standby system has been improved so as to minimize the instantaneous interruption caused by switching. This is based on social demands that digital radio lines often carry data communication networks. As a method that is often adopted as a method of minimizing instantaneous interruption of transmission data, there is a method of making the active standby switching operation sufficiently shorter than the 1-bit length of data.

[0006] In the circuit shown in FIG.
0 and the spare transmission circuit 12 have basically the same configuration. Therefore, the transmission waves output from the active transmission circuit 10 and the standby transmission circuit 12 by inputting the same transmission data are those subjected to the same modulation. Switch 1
Reference numeral 4 switches between the transmission wave output from the active transmission circuit 10 and the transmission wave output from the standby transmission circuit 12, and causes the transmission wave to be transmitted to the wireless line. The working spare switching method mentioned above is a method for performing this switching at a sufficiently high speed. For example, in a system for transmitting data at a mega rate, the switch 14 may be switched in about nsec. Such switching can be realized by using a diode switch as the switch 14.

FIG. 7 shows the operation of the active / standby switching in such a system. Although FIG. 7 assumes multi-level PSK, the following description is the same for other modulation schemes that transmit data by phase, such as multi-level QAM. As shown in this figure, when the transmission data D1, D2, D3, D4,... Are sequentially input to the active transmission circuit 10 and the standby transmission circuit 12, the active transmission circuit 10 causes the corresponding phases θ1, θ2, A transmission wave PSK-modulated by θ3, θ4... is output. Similarly, the preliminary transmission circuit 12 also transmits the transmission data D
Phase corresponding to 1, D2, D3, D4,...
′, Θ3 ′, θ4 ′,.

In the example shown in FIG. 1, the working spare switching is performed at the moment when the transmission data D2 and D3 are exchanged according to the switching signal. Switching at such timing is based on the assumption that the center of each data is sampled when identifying transmission data transmitted on the receiving side. Usually, in order to suppress the spread of spectrum in radio wave propagation in the atmosphere, a band is limited on the transmission side.
Therefore, to obtain the true value of the data on the receiving side,
Sampling should be performed at the timing of the center of the data. Therefore, the above assumption is reasonable.

[0007] Under these assumptions, if switching is performed at the transmission data exchange timing, the identification timing (data center timing) on the receiving side is not affected at all. That is, the receiving side can obtain θ3 ′ next to θ2.

[0008]

Incidentally, since the same configuration is used for the active transmission circuit 10 and the standby transmission circuit 12, the following is obtained: θ1−θ2 = θ1′−θ2 ′ θ2−θ3 = θ2′−θ3 ′: The relationship holds. Assuming that the local oscillation signals (from the transmitting station) are also synchronized, θi = θi ′. However, in general, synchronization is not ensured, and θi ≠ θi ′. For this reason, for example, when switching from θ2 to θ3 ′, the state of the demodulator on the receiving side is changed (acquisition
ition), θ3 ′ must be read as θ3. If the time required for this transition can be made sufficiently short, it is possible to prevent identification errors on the receiving side without strictly securing the synchronization of the transmitting stations of the active transmission circuit 10 and the standby transmission circuit 12, and to prevent the so-called active standby hit. Switching can be realized.

[0009] However, in recent digital radio channels, modulation schemes have been multi-valued in order to improve frequency use efficiency. Along with this, an extraordinary improvement in the operational accuracy of the modem has been required. Therefore, in the synchronous demodulator, the C / N of the reproduced carrier must be large, and as a result, the synchronous PLL (Phase Locked Lo) of the demodulator is required.
op) loop response must be slow. That is,
There is a limit to shortening the time required for the transition (transition time), and it is difficult to prevent identification errors on the receiving side only by shortening the transition time.

Conversely, taking into account that there is a limit to the reduction of the transition time, the time required for the active standby switching (the time required for switching the switch 14) is shortened to realize the active standby hitless switching. If switch 1
4 must be sufficiently fast. However, when the data transmission rate is high, such high-speed operation becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to suppress an output phase difference between an active transmission circuit and a backup transmission circuit, and to eliminate instantaneous interruption caused by switching of a switch. It is an object of the present invention to surely perform active spare hitless switching and to realize an active spare switching method suitable for a high transmission rate.

[0012]

In order to achieve the above object, the present invention relates to a method of switching a working spare according to claim 1 of the present invention.
The method uses one of the two transmission circuits as a working transmission circuit that outputs a transmission wave to a line, uses the other transmission circuit as a standby transmission circuit, and uses a switch to transmit a transmission wave related to the line output to the working transmission circuit. In the set standby method in which the transmission output is switched to the transmission output of the standby transmission circuit, the transmission output of each of the active transmission circuit and the standby transmission circuit is extracted and the phases are compared, and the standby transmission circuit is switched to the active transmission circuit based on the phase comparison result. Phase-synchronized, in the process of switching from the working transmission circuit to the protection transmission circuit by the switch,
The transmission output of the active transmission circuit and the transmission output of the standby transmission circuit are combined so that the output amplitude does not decrease, and output to the line.

According to a second aspect of the present invention, there is provided a working spare switching method , wherein two of the three transmitting circuits are used as working transmitting circuits for outputting transmission waves to different lines, respectively. In the 2 + 1 set standby system, the transmission wave associated with one line output is switched from the transmission output of the corresponding active transmission circuit to the transmission output of the standby transmission circuit by using a switch as a backup transmission circuit of two current transmission circuits. Extracting the transmission output of each of the active transmission circuit and the standby transmission circuit to be switched and comparing the phases, and synchronizing the standby transmission circuit with the active transmission circuit to be switched based on the phase comparison result, In the switching process, the transmission output of the working transmission circuit to be switched and the transmission output of the standby transmission circuit are matched so that the output amplitude does not decrease. And, characterized in that the output to the line.

According to a third aspect of the present invention, there is provided an active / standby switching method according to the first or second aspect, wherein the transmission outputs of the active / standby transmission circuit are extracted by the active / standby transmission circuit. Performed by a plurality of directional couplers provided on the output side of the preliminary transmission circuit, and phase comparison was performed by a phase comparator that inputs the transmission output extracted by the directional coupler, and phase shift was performed according to the output of the phase comparator. The phase of the local oscillation signal of the backup transmission circuit is shifted by the
The phase synchronization is performed.

[0015]

According to the first aspect of the present invention, a phase locked loop for synchronizing the phases of the active transmission circuit and the standby transmission circuit in the set standby system is formed. This loop is
For example, as described in claim 3, it comprises a directional coupler, a phase comparator, a phase shifter and the like. In this phase locked loop, first, the transmission outputs of the working transmission circuit and the backup transmission circuit are extracted, and the extraction results are compared in phase. The phase comparison result indicates the phase difference between the transmission outputs of the working transmission circuit and the protection transmission circuit. In the present invention, the preliminary transmission is performed so that the phase difference is eliminated, that is, the protection transmission circuit is phase-synchronized with the current transmission circuit. The circuit is controlled. Thereby, the output phase difference between the working transmission circuit and the backup transmission circuit is suppressed, and synchronization is ensured.

In addition, in conjunction with this, the working spare switching
This is performed such that the transmission output of the active transmission circuit is output from the line, and the transmission output of the backup transmission circuit is gradually shifted to the state where the transmission output is output from the line (Fade Transition).
That is, a combined output of the transmission output of the active transmission circuit and the transmission output of the standby transmission circuit is output to the line during the active / standby switching so that the amplitude of the line output does not decrease and the demodulation side does not receive a phase shock. Switch so that As a result, so-called hitless switching in which no phase impact occurs and no identification error occurs is reliably realized. Also, the imperfections of the above-described phase locked loop are absorbed.

According to the second aspect of the present invention, the above operation is realized in a 2 + 1 set standby system in which two active transmitting circuits are protected by one spare transmitting circuit. Further, the phase locked loop according to the present invention can be realized by the configuration of the third embodiment.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIGS. 6 and 7 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows a configuration of a transmitting apparatus according to a first embodiment of the present invention. The first feature of this embodiment is that a phase locked loop of the working transmission circuit 10 and the protection transmission circuit 12 is provided.

In the configuration shown in this figure, the directional coupler 16- is added to the configuration of the set standby system shown in FIG.
1 and 16-2 are added. Directional coupler 16-1
Extracts the output of the working transmission circuit 10 and outputs the directional coupler 16
-2 extracts the output of the preliminary transmission circuit 12. If the working transmission circuit 10 and the backup transmission circuit 12 are adjusted to have the same configuration, the directional couplers 16-1 and 16-1
The output of -2 is obtained stably at almost the same level.

The outputs of the directional couplers 16-1 and 16-2 are input to a phase comparator 20 where the phases are compared. In this embodiment, the output of the directional coupler 16-1 is directly input to the phase comparator 20 via the π / 2 fixed phase shifter 18, and the output of the directional coupler 16-2 is input to the phase comparator 20. The π / 2 fixed phase shifter 18 is used in order to make the output of the phase comparator 20 zero-cross when the output phase of the active transmission circuit 10 and the output phase of the standby transmission circuit 12 match. It is. As a result, the polarity information is stored in the output of the phase comparator 20.

The output of the phase comparator 20 is input to the phase shifter 24 inside the preliminary transmission circuit 12 via the LPF 22.
The phase shifter 24 shifts the phase of the oscillation output from the transmitting station 26 of the standby transmitting circuit 12. That is, in this embodiment, a phase locked loop between the active and standby transmitting stations is formed. Here, the LPF 22 determines the response speed of the phase locked loop. Since the device of this embodiment performs phase modulation, the response characteristic of the LPF 22 is set to a sufficiently low speed so as not to affect the phase modulation operation. Phase shifter 24
Calculates the oscillation output of the transmitting local oscillator 26 so that the output of the phase comparator 20 input via the LPF 22 becomes zero, that is, the phase difference between the output of the active transmitting circuit 10 and the output of the standby transmitting circuit 12 disappears. Phase shift. As a result,
The control logic of the phase locked loop between the backup transmitting stations is closed.

In FIG. 1, a fade transition switch (Fade Transit switch) which is a second feature of this embodiment is shown.
An ion switch (hereinafter FTS) 28 is used as a switch for working / standby switching, which will be described later.

FIG. 2 shows a specific configuration of the phase shifter 24. In this embodiment, a linear phase shifter is used instead of an infinite phase shifter. That is, since it is considered that the phase difference between the working spares does not change infinitely, a linear phase shifter is sufficient in this embodiment.

In the example shown in the figure, the phase shifter 24 is configured as a part of a local oscillation stabilizing PLL circuit. That is,
The output (reference signal) of the high stability crystal oscillator 30 is compared in phase with the output of the frequency divider 32 by the phase comparator 34. The reason why the high-stable crystal oscillator 30 is used as a reference signal oscillation source is to improve the frequency stability of the transmitting local oscillator 26 and the purity of the local oscillator output. In this embodiment, the output of the phase comparison circuit 34 is an LPF 36 which is a loop filter.
, And is transmitted to the loop amplifier 38, and the transmission local oscillator 26 as an RFVCO oscillates at a frequency corresponding to the output voltage of the loop amplifier 38. The output of the transmitting local oscillator 26 becomes the local oscillation frequency of the standby transmitting circuit 12, and is divided by the frequency dividing circuit 32 and input to the phase comparing circuit 34.

The loop amplifier 38 used in this embodiment is an amplifier with a DC offset input. That is, the phase comparator 20 supplied via the LPF 22
Is input to the loop amplifier 38 of the phase shifter 24 as a phase shifter control input, and this phase shifter control input causes the output of the loop amplifier 38 to be DC offset. As a result, the PLL circuit controls the output of the phase comparator 20 in a direction to cancel the offset amount. As a result, the output phase of the transmitting station oscillator 26 can be controlled by the phase shifter control input, and the phase shifter 24 can be controlled. Can be easily configured.

As described above, by providing the phase locked loop of the active transmission circuit 10 and the standby transmission circuit 12, the input to the FTS 28 is substantially in phase in this embodiment.

Next, the FTS according to the second feature of the present embodiment is described.
28 will be described. FIG. 3 shows F in this embodiment.
FIG. 4 shows the configuration of the TS 28 and its operation.

Now, for the sake of explanation, the FT from the working transmitting circuit 10 will be described.
The transmission wave input to S28 is represented as input 1 and that from the preliminary transmission circuit 12 is represented as input 2. FTS 28 has variable ATTs 40-1 and 4 that take input 1 or 2, respectively.
0-2. Variable ATT40-1 and 40-2
Are both driven by the ATT drive circuit 42. The ATT drive circuit 42 operates as follows according to the switching signal.

For example, when switching from working to standby is performed, a switching signal rises as shown in FIG. In response, the ATT drive circuit 42 controls the variable ATT 40
-2 is driven to reduce the attenuation factor, and the output response of the FTS 28 to the input 2 is faded on. Thereafter, the ATT drive circuit 42 drives the variable ATT 40-1 to increase its attenuation rate and fades off the output response of the FTS 28 to the input 1. Then, the output of the FTS 28 is in a combined state of the inputs 1 and 2 for a predetermined time after the rise of the switching signal.

In general, when switching the two remaining inputs within a range in which the phase difference does not become out of phase, the FTS relaxes the phase impact at the time of switching and causes the switching to be performed gently. The FTS 28 in FIG. 3 performs switching stably without lowering the amplitude in order to secure the combined state of the inputs 1 and 2 at the time of switching. Therefore, even when data transmission is to be performed at a high rate, in this embodiment, the influence of the switching time hardly affects the demodulation system on the receiving side. That is, according to this embodiment, the active spare hitless switching (switching without a bit error) can be reliably performed. (For details of the FTS, refer to Japanese Patent Application Laid-Open Publication No. Hei. -681
No. 88).

Further, according to the FTS 28, it is possible to switch between two inputs having a residual phase difference without generating a phase shock. Therefore, there is no problem even if a control residual occurs in the phase locked loop between the active standby stations shown in FIG. Therefore, the loop gain of the phase locked loop may be reduced. When the loop gain of the phase-locked loop is lowered, the phase control oscillation generated by the loop itself can be sufficiently suppressed, which is preferable. In addition, precision is not required for the adjustment of the phase locked loop between the working backup stations, and from this point of view,
Hitless switching of the working spare can be realized relatively easily.

FIG. 5 shows the configuration of the second embodiment of the present invention. This embodiment is an example in which the present invention is applied to a 2 + 1 set standby system. The 2 + 1 set standby method uses two (for example, differently-polarized) active transmitting circuits 10-1 and 10-2 and one standby transmitting circuit 12, and uses the standby transmitting circuit 12 as a standby for any of the active transmitting circuits. This is a method that can be used also for. The transmission data to be supplied to the backup transmission circuit 12 is switched to switch the backup transmission circuit 12 between the backup of the working transmission circuit 10-1 and the backup of the working transmission circuit 10-2.
-1 or the current transmission circuit 10-2
Switch 44 for switching whether to use the same transmission data 2 as
And a switch 46 for switching between transmitting the transmission wave related to the output of the standby transmission circuit 12 to the FTS 28-1 of the active transmission circuit 10-1 and outputting the transmission wave to the FTS 28-2 of the active transmission circuit 10-2. Is provided.

In this embodiment, the phase-locked loop between the active backup transmitting stations includes a switch 48. This switch 48 is used when the standby transmission circuit 12 is used as a standby for the active transmission circuit 10-1.
It is connected to the directional coupler 16-1 that extracts the output of 0-1. Conversely, the spare transmitting circuit 12 is replaced with the working transmitting circuit 10-
In the case of setting the spare to 2, the directional coupler 16-3 is connected to the directional coupler 16-3 for extracting the output of the working transmission circuit 10-2. As a result, the phase of the standby transmission circuit 12 is changed to the current transmission circuit (10-2 or 10-2) of the partner to be switched.
The phase is synchronized with the phase of -2).

Also in this embodiment, since the FTS is used, it is possible to realize the active spare hitless switching.
And the FTSs correspond to the two working sets, 28-1 and 28-
2 is provided, the effect is the transmission output 1
And 2 can be obtained.

[0036]

As described above, according to the first aspect of the present invention,
According to the active / standby switching method according to the first aspect, a phase-locked loop for performing phase synchronization between the active and standby transmission circuits in the set standby mode is provided, and the active / standby switching is performed by F
Since the transmission is performed by the TS, synchronization between the active transmission circuit and the standby transmission circuit is ensured, and the active standby hitless switching is reliably realized even at a high transmission rate. Also,
Since the FTS allows the phase control residual of two inputs within a certain range, it is possible to set the response speed of the phase locked loop to be slow so that the phase control oscillation is suppressed, and to adjust the phase locked loop. However, since precise adjustment is not required, it is possible to relatively easily perform the active spare hitless switching.

According to the second aspect, the same effect as the first aspect can be obtained in the 2 + 1 set standby system.

According to the third aspect, the phase locked loop can be simply and suitably realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a transmitting-side device of a set standby system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a local oscillation output phase shifter in this embodiment.

FIG. 3 is a diagram showing a configuration of an FTS in the embodiment.

FIG. 4 is a diagram showing the operation of the FTS in this embodiment.

FIG. 5 is a diagram showing a configuration of a transmission-side device of a 2 + 1 set standby system according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the configuration of a set-standby transmission apparatus according to a conventional example.

FIG. 7 is a diagram showing a switching image of a PSK transmission wave in a conventional example.

[Explanation of symbols]

 10, 10-1, 10-2 Working transmitting circuit 12 Preliminary transmitting circuit 16-1, 16-2, 16-3 Directional coupler 20 Phase comparator 24 Phase shifter 28 Fade transition switch (FTS) 44, 46, 48 switches

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadayuki Kitamura 5-1-1 Shimorenjaku, Mitaka City, Tokyo Inside Japan Radio Co., Ltd. (72) Inventor Hirofumi Hoshino 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Telegraph and Telephone Co., Ltd. Examiner Yasushi Shimizu (56) References JP-A-4-200038 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/20

Claims (3)

(57) [Claims] 1. One of two transmitting circuits is used as a working transmitting circuit for outputting a transmitting wave to a line, the other transmitting circuit is used as a spare transmitting circuit, and a transmitting wave related to the line output is used for a working transmission by a switch. In the set-standby mode in which the transmission output of the circuit is switched to the transmission output of the standby transmission circuit, the transmission outputs of the active transmission circuit and the standby transmission circuit are extracted, the phases are compared, and the standby transmission circuit is transmitted based on the phase comparison result. In the process of switching from the working transmission circuit to the protection transmission circuit by the switch, the transmission output of the working transmission circuit and the transmission output of the protection transmission circuit are combined so that the output amplitude does not decrease, and output to the line. Active spare switching
How . 2. Two transmission circuits of the three transmission circuits are used as active transmission circuits for outputting transmission waves to different lines, respectively, and the other one is used as a standby transmission circuit of the two active transmission circuits. In a 2 + 1 set standby system in which a transmission wave related to one line output is switched from a transmission output of a corresponding active transmission circuit to a transmission output of a standby transmission circuit by a switch, the active transmission circuit and the standby transmission circuit to be switched are each The transmission output is extracted, the two are compared in phase, the backup transmission circuit is phase-synchronized with the working transmission circuit to be switched based on the phase comparison result, and in the switching process, the working transmission circuit to be switched is Active spare switching characterized in that the transmission output and the transmission output of the standby transmission circuit are combined so that the output amplitude does not decrease and output to the line. Method. 3. The working standby switch according to claim 1 or 2.
In the method , the transmission outputs of the active transmission circuit and the standby transmission circuit are extracted by a plurality of directional couplers provided on the output side of the active transmission circuit and the standby transmission circuit, and the phase comparison is extracted by the directional coupler. A phase comparator that inputs the transmission output that has been input, and a phase shifter that shifts the phase of the local oscillation signal of the standby transmission circuit according to the output of the phase comparator to perform the phase synchronization.
How .