A phase adjusting system for a radio communication system

Abstract: The system comprises a central station including a CPU (21), a memory (23) a delay time detecting circuit (25) and delay time setting circuits (26) for corresponding transmitters connected to the central station. A plurality of receivers are arranged to receive signals from corresponding transmitters. A target number is assigned to each of the transmitters, whereby they can be designated one by one. The memory (23) stores the sequential order of the target numbers to perform the phase adjustment of the transmitters in the sequential order. In the memory (23) the sequential order of the target numbers can be changed by an external terminal (22), so that the sequential order of the transmitters is changed in phase adjustment without changing the target numbers. Phase adjustments are carried out in known manner by comparing detected delay times with reference delay times, the latter preferably being each established by the preceding transmitter in the adjustment sequence.

Description: The invention relates to a phase adjusting system for a radio communication system, and more particularly to a phase adjusting system for a radio communication system such as a paging system. One type of known phase adjusting system for a radio communication system such as a paging system is described in German Patent Specification DE-A-30 35 679 and comprises a plurality of transmitters each connected to a central station, and a plurality of receivers each connected for phase adjustment to the central station and positioned between corresponding pairs of the transmitters. The central station controls the system, and comprises a plurality of delay time setting circuits each provided on a line connected to a corresponding one of the transmitters. Among the transmitters, the sequential order of the phase adjustment is fixed beforehand, wherein a transmitter which plays a role for a standard in the phase adjustment is called "a reference", and a transmitter which is adjusted in phase is called "a target". In one way in which such a known system may be operated, a transmitter which is No. 1 in the sequential order of the phase adjustment is regarded as a reference for the first phase adjustment, and a transmitter which is No. 2 therein is the target, so that a signal is transmitted from the central station through the delay time setting circuit to the transmitter No. 2, then from the transmitter No. 2 to the corresponding receiver, and from the receiver back to the central station, and a further signal is transmitted from the central station through the delay time setting circuit to the transmitter No. 1, then from the transmitter No. 1 to the corresponding receiver, and from the receiver back to the central station. In the central station, delay times are detected in the signals transmitted through the transmitters Nos. 1 and 2 for the reference and target. The difference of the delay times is calculated, so that a value corresponding to the difference is set in the delay time setting circuit for the target transmitter No. 2 to decrease the difference to a sufficient extent. In the second phase adjustment, the transmitter No. 2 is the reference, and a transmitter which is No. 3 in the sequential order is selected for the target, so that the same phase adjustment operation as in the first phase adjustment is performed between the transmitters Nos. 2 and 3. In this manner, all the transmitters are adjusted and brought into phase. In one known phase adjusting system, each of the transmitters comprises a memory for storing its own sequential order for the phase adjustment, so that one of the transmitters is turned on in accordance with the designation of the number in the sequential order from the central station, and turned off in accordance with ceasing of the designation thereof. Therefore, the phase adjustment can be repeated sequentially only by designating the numbers in the sequential order. In the known phase adjusting system, however, we have appreciated that there is a disadvantage in that it is difficult to change the sequential order of the phase adjustment, because it is inconvenient to change the content of the memory for each of the transmitters, since almost all of the transmitters are installed in stations having no staff for maintaining the stations. Even if the content of the memory is changed in the station by dispatching staff thereto, considerable time is consumed. During this time, therefore, the phase adjustment operation must cease, so that changes of delay times are not corrected. United Kingdom Patent Application GB-A-2 001 230 describes a simultaneous broadcast (simulcast) transmission system, which uses several spaced transmitters which may be fed from a central station by different possible paths. The different path lengths lead to different phase delays. The central station stores the phase delays appropriate to the different paths in a memory, and invokes the required delays dependent upon the paths currently in use. The invention is defined in claim 1 below, to which reference should now be made. The sequential order of the plural transmitters can be changed in the phase adjustment simply by changing the sequential order in the memory. This means that it is not necessary to change the target numbers assigned to the plural transmitters. Preferably, the reference transmitter to be used for each target transmitter is also stored in memory at the central station. The invention will be described in more detail, by way of example, in conjunction with appended drawings wherein, Fig. 1 is a block diagram showing a paging system which includes a phase adjusting system, Fig. 2 is a block diagram showing a phase adjusting system for a paging system in an embodiment according to the invention, Fig. 3 is a block diagram showing a delay time detecting circuit in the phase adjusting system shown in Fig. 2, Figs. 4A and 4B are tables storing relations between target number and reference number, and between sequence number and the target number, Fig. 5 is an explanatory diagram showing a phase adjusting signal to be transmitted to transmitters, Fig. 6 is an explanatory diagram showing a control signal for turning on the transmitting output of the transmitter, Fig. 7 is an explanatory diagram showing a control signal for turning off the transmitting output of the transmitter, Fig. 8 is a chart for explaining the detection of delay time in the delay time detecting circuit in Fig. 3, Fig. 9 is the table for changing the sequential order of target transmitters, and Fig. 10 is an explanatory diagram showing a phase adjusting signal to be transmitted to transmitters in accordance with the table in Fig. 9. Fig. 1 shows a paging system which comprises a central station 10 including a phase adjusting system to be described later, transmitters (Nos. 1 to 4) 11, 13, 15 and 17 receiving signals from the central station 10, and receivers 12, 14 and 16 positioned between the transmitters 11 and 13, 13 and 15, and 15 and 17. Fig. 2 shows a phase adjusting system in an embodiment according to the invention which is included in the central station 10 as shown in Fig. 1. The phase adjusting system comprising a CPU 21 for controlling the whole system, an input/output terminal 22 for input of commands, parameters etc. for the phase adjustment and for output of control results, a memory 23 for storing the parameters etc., a serial/parallel converter 24 for conversion between a serial signal and a parallel signal, a delay time detecting circuit 25 for detecting the delay time of signal from one of the receivers 12, 14 and 16, and delay time setting circuits 26, each setting the delay time of the signal for a corresponding one of the transmitters 11, 13, 15 and 17. In the phase adjusting system, the CPU 21 is connected through a signal line 20 to the delay time detecting circuit 25 which is also connected through signal lines 20 to the delay time setting circuits 26. The delay time detecting circuit 25 is connected through signal lines 28 to the respective receivers 12, 14 and 16, and each of the delay time setting circuits 26 is connected through a signal line 27 to a corresponding one of the transmitters 11, 13, 15 and 17. Further, the memory 23 and the delay time setting circuits 26 are connected by address/data buses 29. Fig. 3 shows the delay time detecting circuit shown in Fig. 2 which comprises an oscillator 30 for generating pulse signal, a bit array comparator 31 for supplying "1" signal to a terminal S of a flip-flop circuit 33 when the comparators 31 detects specified bit array signal in signal from the CPU 21, a bit array comparator 32 for supplying "1" signal to a terminal R of the flip-flop circuit 33 when the comparator 32 detects the specified bit array signal in signal from one of the receivers 12, 14 and 16, an AND circuit 34 for passing the pulse signal dependent on output of a terminal Q of the flip-flop circuit 33, and a counter 35 for counting the pulse signal and connected through an address/data bus 36 to the CPU 21. Figs. 4A and 4B show tables stored in the memory 23, wherein the first table of Fig. 4A stores a corresponding relation between a target transmitter and a reference transmitter as designated by the aforementioned numbers 1 to 4 of the transmitters 1 1 13, 15 and 17, and the second table of Fig. 4B stores the aforementioned sequential order of the target transmitter which is subject to the phase adjustment as also designated by the same transmitter numbers 1 to 4. In operation, phase adjusting signal is supplied in addition to radio calling signal from the CPU 21 in the central station 10. The phase adjusting signal is serial signal including several blocks of signal as shown in Fig. 5. That is, the phase adjusting signal is composed of a first control signal portion A including the number of a transmitter to be designated and control code for turning on transmitting output of a designated transmitter, a delay time detecting signal portion B including specified bit array, and a second control signal portion C including control code for turning off the transmitting output. The first control signal portion A includes bit synchronous signal 61 of eight bits and plural frames, for instance, four frames of control signal 62 as shown in Fig. 6. The control signal 62 is of twenty-four bits wherein bits C are for turning on a target transmitter, a reference transmitter, or the both transmitters dependent on content thereof, bits N are for indicating the number of a target or reference transmitter to be designated, and bits P are for odd parity. The control code for turning off the transmitting output in the portion C includes plural frames, for instance, four frames of control signal 71 as shown in Fig. 7. The reason why the control signals 62 and 71 are of plural frames is that one of the plural frames is surely received in a corresponding transmitter even if one of the remaining frames fails to be received therein due to error induced in some trouble. On the other hand, nine stage PN (Pseudo Noise)signal is used in one example for the delay time detecting signal portion B. The nine stage PN signal is characterized in that specified nine bit array, for instance, "010010111" appears in one period only by one time. The character of the nine stage PN signal is utilized in the bit array comparators 31 and 32 in which specified nine bit arrays are set, so that the bit array comparators 31 and 32 detect the specified bit arrays among bit arrays from the CPU 21 and the receivers 12, 14 and 16. Serial data from the CPU 21 are monitored in the bit array comparator 31, so that signal "1" is supplied from the bit array comparator 31 to the terminal 5 of the flip-flop 33 when specified bit array is detected from the delay time detecting signal portion B of the phase adjusting signal. As a result, the output Q of the flip-flop 33 becomes "1" as shown in Fig. 8, so that the pulse signal from the oscillator 30 is passed through the AND circuit 34 to the counter 35 in which the pulse signal is counted. Simultaneously, serial data received through the signal line 28 from one of the receivers 12, 14 and 16 are monitored in the bit array comparator 32, so that signal "1" is supplied from the bit array comparator 32 to the terminal R of the flip-flop 33 when the specified bit array is detected. As a result, the output Q of the flip-flop 33 becomes "0" as shown in Fig. 8, so that the pulse signal is not passed through the AND circuit 34. At this moment, the counted value is kept in the counter 35, and then read therefrom through the address/data bus 29 to the CPU 21. Therefore, the counter 35 is reset to be ready for following counting operation, while delay time is calculated in the CPU 21 in accordance with the counted value of the counter 35. The phase adjustment is performed by decreasing the difference, between delay time of a signal line connected to a reference transmitter and delay time of a signal line connected to a target transmitter, down to a sufficiently small value. Therefore, the delay time of the both target and reference transmitters is necessary to be detected. For this purpose, one of the transmitters 11, 13, 15 and 17 is designated as "reference", and the other is as "target". At first, the target number "2" corresponding to the sequence number "1" is read from the table (Fig. 4B) in the memory 23, so that the aforementioned phase adjusting signal, by the control signal portion A of which the transmitter (No. 2) 13 is designated, is produced in the CPU 21 as shown in Fig. 5. Thus, delay time of the transmitter (No. 2) 13 is detected in the delay time detecting circuit 25. Secondly, the reference number "3" corresponding to the target number "2" is read from the table (Fig. 4A) in the memory 23, so that the phase adjusting signal, by the control signal portion A of which the transmitter (No. 3) 15 is designated, is produced as also shown in Fig. 5. In the same manner, delay time of the transmitter (No. 3) 15 is detected in the delay time detecting circuit 25. Thereafter, predetermined delay time is calculated dependent on the difference of delay time between the transmitters (Nos. 2 and 3) 13 and 15, and is newly set into the delay time setting circuit 26 corresponding to the target transmitter (No. 2) 13, so that the delay time difference is sufficiently decreased down to a sufficiently small value, whereby the phase adjustment of the transmitter (No. 2) 13 is completed. Thirdly, the target number "1" corresponding to the sequence number "2" is read from the table (Fig. 4B), so that the detection of delay time is performed for the target transmitter (No. 1) 11. Fourthly, the reference number "2" corresponding to the target number "1" is read from the table (Fig. 4A), so that delay time of the reference transmitter (No. 2) 13 is detected. As a result, further predetermined delay time is set into the delay time setting circuit 26 corresponding to the target transmitter (No. 1) 11. The other transmitters are adjusted in phase by the phase adjusting signal of Fig. 5 produced in accordance with the tables of Figs. 4A and 4B in the same manner as described above. In a case where the sequential order of transmitters to be adjusted in phase is changed, command having parameter of sequence number and target number is supplied from the input/output terminal 22 to the CPU 21, so that the command is analized in the CPU 21. Where the command is determined in the CPU 21 that the command is for changing relation between target number and sequence number, content of the table is changed from Fig. 4B to Fig. 9 as ordered by an operator of the input/output terminal 22. In accordance with the table of Fig. 9, the phase adjusting signal including the first control signal portion A, the delay time detecting signal portion B, and the second control signal portion C is produced as shown in Fig. 10. As clearly understood from Figs. 9 and 10, the transmitters (Nos. 4, 2 and 1) 17, 13 and 11 are sequentially adjusted in phase in the same manner as described before, Therefore, the sequential order can be changed among plural transmitters without changing the number assigned to the transmitters.

Claims: A phase adjustment system for a radio communications system of the type comprising a plurality of transmitters (11,13,15,17) and a plurality of receivers (12,14,16), and in which signals transmitted by a target one of the transmitters and a reference one of the transmitters are received by a receiver, the phase adjustment system comprising: a delay time detecting circuit (25) for detecting the transmission time difference for transmissions received by a receiver from a target transmitter and a reference transmitter; delay time setting circuits (26) associated with respective ones of the transmitters (11,13,15,17); a controller (21) coupled to the delay time detecting circuit to receive the transmission time difference and to the delay time setting circuits to adjust the respective delay time setting circuit for the target transmitter in dependence thereon; a memory (23) for storing sequential numbers representing a sequential order for the transmitters, the memory being coupled to the controller to control the sequential order in which the transmitters become the target transmitter for phase adjustment; and an input/output terminal (22) for receiving a sequential order changing signal for changing the sequential order stored in the memory, whereby a new sequential order can be stored in the memory without changing the target numbers allocated to the transmitters. A phase adjustment system according to claim 1, in which the controller (21) selects a predetermined reference transmitter (e.g. No. 1) for use with each selected target transmitter (e.g. No. 2). A phase adjustment system according to claim 2, in which the memory (23) stores an indication of the reference transmitter associated with each target transmitter.

Inventors: NAKAHARA KENJI, NAKAHARA, KENJI
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1989
Main classification: H04H3
IPC codes: H04H3, H04B7, H04Q7, H04H20