JP4076977B2 - Spread spectrum communication apparatus and opposite station receiver - Google Patents

Description

  The present invention relates to a spread spectrum communication apparatus that communicates using a spread spectrum system and an opposite station reception apparatus thereof, and more particularly to an apparatus that switches between a plurality of antennas.

For example, in a mobile satellite communication system that communicates with a mobile station on the ground from a fixed station via a communication satellite, a directional antenna is often used as the antenna on the mobile station side in order to increase the gain. In this case, the directivity of the directional antenna must always be controlled in the direction of the communication satellite according to the movement of the satellite and the movement of the mobile station. Such an antenna directing device requires a large mechanism part, or an array antenna that electronically controls the directing direction requires a large area, and requires advanced control technology for directing control. It is quite difficult to control the vehicle while traveling on it, and simplification is desired.
As one method of such simplification, Patent Document 1 includes a plurality of semi-fixed antennas that partially overlap their directivity ranges and irradiate different airspaces, and communicate by switching these appropriately. Is disclosed. In this case, when the communication satellite is only in the airspace of one antenna, the demodulated signal of the reception system connected to the antenna on which the directivity is effective is sent to the output terminal, and the modulation output from the terminal is When the effective antenna is changed according to the movement of the satellite or the moving body, the antenna is switched to the antenna with the effective directing to perform transmission and reception.

The operation when the communication satellite moves to the boundary (overlapping part) between two adjacent airspaces will be described. First, the reception will be explained. Equipped with two receiving systems corresponding to the two antennas on both sides of the boundary, the phase of the signal obtained from the receiving system on the use side will be the same as that of the receiving system currently in use. The phase is compensated based on the path difference between the two antennas and the satellite so as to match the signal phase, and the antenna is switched after the two phases match. As a result, bit errors due to signal phase shifts do not occur before and after switching when switching.
Also, for transmission, two transmission systems are provided, and phase compensation corresponding to the amount of phase shift due to the difference between both paths obtained by the reception is corrected by adjusting the chip phase of the transmission system, and the carrier phase For the difference between the two, the phase is shifted before and after switching when receiving on the satellite side by performing compensation after re-synchronization and switching after compensating the transmission system on the side used for future transmission. Since there is no bit error, no bit error occurs.

Patent Document 2 discloses a bit spread Aloha system. This is a known technique used in Embodiment 1 of the present application.
JP-A-3-52336, a mobile station of a mobile satellite communication system using a spread spectrum communication system. Japanese Patent Laid-Open No. 3-150940, Bit spread Aloha system.

In the conventional system, when switching a plurality of antennas on the mobile station side, the reception has a partially overlapping part in the directivity area of each antenna, and after matching the phases of the received signals simultaneously received by the two antennas Switch.
In transmission, switching is performed after correcting the difference in chip phase and carrier phase caused by the transmission distance difference between the two antennas due to switching of the transmission system.
In this case, a bit error occurs unless the antenna switching time is made extremely short and carrier phase shift correction is performed at high speed. However, speeding up antenna switching is not easy. In addition, the phase of the transmission system / reception system changes every moment due to the movement of the mobile station (change in the antenna position), so that the correction is not easy, and a phase difference occurs and the bit error rate is not improved as expected. was there.

  The present invention provides a spread spectrum communication apparatus that solves the above-described problems and improves the bit error rate by facilitating phase correction performed for each antenna of a mobile station, particularly in spread spectrum communication.

The spread spectrum communication apparatus of the present invention includes a first antenna and a second antenna that are arranged such that part of the directivity areas overlap each other and the arrival time difference of radio waves to the other station is equal to or less than a predetermined time difference. Antenna,
Two power amplifiers for supplying carrier power to each of the first and second antennas;
One spread Aloha modulator for supplying a modulated signal generated by separating one code signal to each of the two power amplifiers;
A delay inserted between the spread Aloha modulator and the first antenna, and the sum of the delay time and the arrival time difference from the two antennas to the counterpart station is greater than one chip time of the spreading code Means are provided.

  The spread spectrum communication apparatus of the present invention includes one transmission system for each of a plurality of antennas, and does not cause a bit error when switching antennas. Therefore, the configuration of the apparatus can be reduced in size and cost. The effect that it can be obtained.

Embodiment 1 FIG.
Hereinafter, a spread spectrum communication apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals indicate the same or corresponding parts, and therefore detailed description thereof will not be repeated for each drawing. For convenience of explanation, the description will be made assuming communication between a mobile station and a fixed station via a communication satellite. However, the present invention is not limited to such a case, and the mobile station and the mobile station are fixed. It can also be used between stations and fixed stations. The mobile station 100 is a communication device that is mounted on a mobile unit 50 and uses a spread spectrum system, and has a plurality of antennas (first antenna 1 and second antenna 2 in FIG. 1) that are directed to different regions. As shown in FIG. 2, both antennas are installed such that part of the directivity area 101 of the first antenna 1 and part of the directivity area 102 of the second antenna 2 overlap each other. In transmission from the mobile station 100 to, for example, a fixed station 200 (hereinafter referred to as a partner station) via a communication satellite, a signal from a terminal 15 as an input / output device is converted into a spread Aloha modulator / demodulator 13 (hereinafter referred to as S / A-MODEM). The details will be described later) to obtain a spread spectrum signal. The signal from the S / A-MODEM 13 is divided by the hybrid 11 (hereinafter referred to as H), converted into a transmission carrier frequency by the up-converters 5 and 6 (hereinafter referred to as U / C), and then the high power amplifiers 3 and 4 ( Hereinafter, the signals are sent to the first antenna 1 and the second antenna 2 via the HPA), and are adjusted so as to be output from each antenna at substantially the same output level.
FIG. 4 is a diagram for explaining a difference in path length between each antenna and a partner station. Here, the path length to the modulator / demodulator incorporated in the partner station via the antenna 1 (the path 30a in FIG. 4 and the internal circuit length in FIG. 1 combined) and the opposite station via the antenna 2 The phase difference of the transmission signal based on the difference between the path length to the built-in modulator / demodulator (the path 30b in FIG. 4 and the internal circuit length in FIG. 1) is made larger than one chip time of the spreading code. As described below, the S / A-MODEM 13 and the antenna 1 or 2 of both systems are installed with a necessary transmission distance difference.

  That is, as shown in FIG. 1, a redundant transmission path 90 is inserted between the second antenna 2 (or the first antenna 1) and the mobile station device 100. The redundant transmission path 90 sets the physical arrangement distance difference between the two antennas so that the transmission data has a transmission path difference equal to or longer than the distance that the transmission data travels in one chip time. Specifically, the chip rate is 20 MHz. In this case, the necessary distance difference needs to be larger than 15 m. At this time, it is also necessary to take into account the path distance difference (60 in FIG. 4) from the facing satellite to the antenna. In addition, since the satellite is sufficiently far away, there is almost no influence of the actual distance between the antennas to be switched, so in practice, the transmission path difference within the mobile station is increased by about 30% of the above required distance difference, for example, about 20 m. Just do it.

Next, reception of radio waves from the fixed station 200 having the configuration shown in FIG. 1 will be described. Although not specifically illustrated, it is assumed that one signal is transmitted from one antenna from a communication satellite.
This one signal is received from the first and second antennas of FIG. Since the transmission path difference in the transmission system and the transmission path difference in the reception system are the same, the phase difference in the reception system of the mobile station is larger than the phase of one chip. Then, it is input to the S / A-MODEM 13 through the low noise amplifiers 7 and 8, the down converters 9 and 10, and the hybrid 12. At this time, the phase of the signal received from the second antenna 2 by the redundant transmission path 90 is delayed more than one chip time of the spreading code as compared with the phase of the signal received from the first antenna 1.
The S / A-MODEM 13 is disclosed in Patent Document 2 and, as will be described later, is a modem that can individually receive two signals having different chip phases of the same spreading code, so that these two signals are demodulated separately. Can be output as two received signals.
Further, the PN code generator 14 (hereinafter referred to as Pngen) compares and synchronizes two received signals, so that even if one of the signals is lost due to antenna switching of the transmitting mobile station, the received data is interrupted. Bit errors do not occur.
HPA is called a power amplifier. S / A-MODEM is called a spread Aloha modulator when used as a modulator, and a spread Aloha demodulator when used as a demodulator. The redundant transmission line is a delay means in the present invention.

Embodiment 2. FIG.
Next, a receiving circuit for receiving a signal transmitted from the transmission system of FIG. 1 at another place (especially when the direction of the other station does not change so much and the antenna does not need to be switched, such as a receiving device of a fixed station). A simplified counter station receiver will be described. The receiving circuit may have the same configuration as the receiving system of the circuit shown in FIG. 1, but it can be simplified by the following.
FIG. 3 is a block diagram for explaining the configuration of the opposite station communication apparatus 200 mounted on, for example, a fixed station using a simplified receiving circuit. The receiving system portion (LNA 7 to D / C 9 to S / A-MODEM 13) in the figure corresponds to the opposite station receiving apparatus referred to in the present invention. When the two antennas 1 and 2 of the mobile station 100 of FIG. 1 are outputting signals, the output signal from the S / A-MODEM 13 of the mobile station 100 is two signals at the partner station 200 as shown in FIG. Is input to the S / A-MODEM 13 of the partner station 200 with a phase difference of one chip or more. The S / A-MODEM 13 is disclosed in Patent Document 2 and, as will be described later, is a modem that can individually receive two signals having different chip phases of the same spreading code, so that these two signals are demodulated separately. Can be output as two received signals. By using a spread Aloha demodulator, the receiving system can be made into one system as shown in FIG.

Further, the PN code generator 14 (hereinafter referred to as Pngen) compares and synchronizes two received signals, so that even if one of the signals is lost due to antenna switching of the transmitting mobile station, the received data is interrupted. Bit errors do not occur.
The spread Aloha modulator / demodulator 13 (S / A-MODEM) will be described. Patent Document 2 discloses a spread Aloha system. The spread Aloha demodulator can individually demodulate two signals having the same spreading code when they are input with a phase difference larger than one chip.

Embodiment 3 FIG.
Hereinafter, the configuration of satellite communication mobile station apparatus 300 according to the third embodiment of the present invention will be described with reference to FIG. The mobile station 300 is a mobile communication system using a spread spectrum system. As described with reference to FIG. 2 of the first embodiment, mobile station 300 has a plurality of antennas that are directed to different areas, and is set so that a part of the directional areas overlaps. In transmission from the mobile station 300 to the partner station, the signal from the S / A-MODEM 13 (Spread Aloha Modulator / Demodulator) is divided by H11 (hybrid), and U / C5, U / C6 (upconverter), HPA3, The signals are sent to the first antenna 1 and the second antenna 2 via the HPA 4 (high power amplifier) and adjusted so as to be output from each antenna at substantially the same output level.
At this time, the S / A-MODEM 13 and the antennas of the two systems are set in advance so that the transmission path length between the modem and the built-in modem in the opposite station is larger than the one-chip time of the spread code. A delay device 39 (shown as D in the figure) is installed between the two. The delay device 39 delays the signal of one path and sets a necessary chip phase difference. Specifically, when the chip rate is 20 MHz, the delay amount of one chip is 50 ns. Considering the fluctuation of the path difference, it is increased by 30%, for example, a mobile station transmission line delay of 66 ns or more may be set.
The counterpart station side is the same as that in FIG. 4 of the second embodiment. By comparing the two received signals and synchronizing with the PN code generator 14, one of the signals is lost by switching the antenna of the transmitting mobile station. However, no bit error such as disconnection of received data occurs.

In FIG. 5, the delay device 39 on the transmission side is inserted between U / C 6 and H 11, but may be between HPA 4 and U / C 6 or between HPA 4 and the second antenna 2. Moreover, you may insert in the said position of the 1st antenna 1 side, without inserting in the 2nd antenna 2 side.
Similarly, on the receiving side, a delay device 40 having the same performance as that of the delay device 39 is inserted between the D / C 10 and H12. This may be between the LNA 8 and the D / C 10 or between the LNA 8 and the second antenna 2. Moreover, you may insert in the said position of the 1st antenna 1 side, without inserting in the 2nd antenna 2 side. The delay devices 39 and 40 are delay means according to the present invention.

Embodiment 4 FIG.
The techniques of the embodiments described above can be used in appropriate combination. Here, the transmission system using the transmission system portion of the circuit configuration of FIG. 1 of the first embodiment and the reception system using the reception system portion of the circuit configuration of FIG. 3 of the second embodiment are shown in FIG. Show.
In FIG. 6, the receiving system mixes and extracts the signal received from the first antenna 1 and the signal received from the second antenna 2 and delayed in the redundant transmission path 90 by the mixer 23. In the present embodiment, the receiving system does not switch antennas in terms of circuit, but radio waves from the other station (two signals transmitted in the transmitting system in FIG. 1 having different phases) are sensed by either antenna. In order to do so, it is substantially switched. Although not shown, a directional coupler is used as appropriate so that the transmission power of HPA3 and HPA4 is not mixed into the reception system, but detailed description thereof is omitted because it is a known technique.

Embodiment 5. FIG.
In Embodiments 1 to 4, it has been described that there are two antennas. Here, a case where there are three or more antennas will be described. Even if there are three or more antennas, switching is performed between two antennas having adjacent directivity areas among the three antennas. Therefore, the two transmission systems shown in FIG. 1 are sequentially switched to the antenna to be switched next by the first antenna switching circuit 20 and the second antenna switching circuit 21 as shown in FIG. Switching by the antenna switching circuits 20 and 21 requires special explanation because the partner station is in the area of one antenna and has not yet reached the boundary area, that is, switching is performed for an antenna that is not currently communicating. No explanation is given.
7, A, B, C, D... Schematically show a plurality of antennas, and a, b, c, d. FIG. 8 shows an antenna switching procedure to be switched when the partner station moves in the order of a, b, c, and d. The switching circuit 20 of the first antenna is switched in the order of A, C, E, and the second antenna 21 is switched in the order of B, D,.

  The spread spectrum communication apparatus according to the present invention is not limited to the one installed in the mobile station, but can be used for a station that operates by switching antennas, such as a fixed station that has other stations in a plurality of directions.

1 is a configuration diagram of a spread spectrum communication apparatus according to Embodiment 1 of the present invention. It is area | region explanatory drawing of the antenna of FIG. 6 is a configuration explanatory diagram of a simplified receiving system according to Embodiment 2. FIG. It is explanatory drawing of the path | route difference of the antenna of FIG. FIG. 6 is a configuration diagram of a spread spectrum communication apparatus according to a third embodiment. FIG. 6 is a configuration diagram of a spread spectrum communication apparatus according to a fourth embodiment. FIG. 10 is a configuration diagram of a spread spectrum communication apparatus according to a fifth embodiment. It is a figure explaining the operation | movement of FIG.

Explanation of symbols

1 First antenna, 2 Second antenna, 3, 4 High power amplifier (HPA)
5, 6 Upconverter (U / C) 7, 8 Low noise amplifier (LNA)
9, 10 Down converter (D / C) 11, 12 Hybrid (H)
13 Spread Aloha Modulator / Demodulator (S / A-MODEM),
14 PN code generator (PNgen)
15 terminals,
20 first antenna switching circuit, 21 second antenna switching circuit,
30 Communication satellite antenna,
30a The path between the communication satellite and the first antenna of the mobile station,
30b The path between the communication satellite and the second antenna of the mobile station,
39, 40 Delay (D), 50 mobile, 60 path difference,
90 redundant transmission lines, 100 mobile stations, 190 simplified reception system,
200 fixed stations, 300 mobile stations.

Claims (6)

A first antenna and a second antenna arranged so that a part of the directivity area overlaps each other and a difference in arrival time of radio waves to the communication partner station is equal to or less than a predetermined time difference;
Two power amplifiers for supplying carrier power to each of the first and second antennas;
A spread Aloha modulator that generates a spread code signal from one code signal and supplies it to each of the two power amplifiers;
A delay inserted between the spread Aloha modulator and the first antenna, and the sum of the delay time and the arrival time difference from the two antennas to the communication satellite is greater than one chip time of the code signal A spread spectrum communication apparatus comprising means.   2. The spread spectrum communication according to claim 1, wherein the delay means is a redundant transmission line inserted between the first antenna and the power amplifier that supplies the carrier power to the antenna. apparatus.   The delay unit is a delay circuit inserted between the power amplification unit that supplies the carrier power to the first antenna and the spread Aloha modulator. Spread spectrum communication device. A counter-station receiving apparatus that receives two signals transmitted from the spread spectrum communication apparatus according to claim 1 and whose phase difference is larger than one chip time of the code,
One antenna,
One spread ALOHA demodulator capable of individually demodulating two signals received with a phase difference of one chip or more received by the one antenna as two signals;
A counter-station receiving apparatus comprising a PN code generator that compares the demodulated two signals to synchronize received data and reproduces one original code signal. A first antenna and a second antenna arranged such that a part of the pointing area overlaps each other and a difference in arrival time of radio waves to the communication satellite is equal to or smaller than a predetermined time difference;
Two power amplifiers for supplying carrier power to each of the first and second antennas;
One spread Aloha modulator for supplying a modulated signal generated by separating one code signal to each of the two power amplifiers;
A delay inserted between the spread Aloha modulator and the first antenna, and the sum of the delay time and the arrival time difference from the two antennas to the communication satellite is greater than one chip time of the code signal means,
One spread aloha demodulator capable of individually demodulating two signals received by the two antennas and having a phase difference of one chip or more by the delay means as two signals;
A spread spectrum communication apparatus comprising a PN code generator that compares the two demodulated signals to synchronize received data and reproduces one original code signal.   The spread spectrum communication apparatus according to any one of claims 1, 2, 3, and 5, wherein the spread spectrum communication apparatus is mounted on a mobile body and performs communication with a communication satellite.

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