JP3231819B2 - Antenna 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 antenna switching system for a mobile-mounted antenna device for performing satellite communication by a direct spread spectrum multiplexing communication system (DS-SSMA).

[0002]

2. Description of the Related Art FIG. 2 is a diagram for explaining an antenna switching method of a conventional mobile-mounted antenna device for performing satellite communication. For simplicity, an example of switching between a pair of antennas and one transmitter will be described. In the figure, reference numeral 1 denotes a direction in which a mobile onboard antenna tracks a communication satellite, 2a,
2b is a pair of antennas, 3 is a radio wave shield on a moving body, 4
Reference numerals a and 4b denote transmission / reception separators, reference numerals 5a and 5b denote reception units, reference numeral 6 denotes a transmission unit, reference numeral 7 denotes an antenna directional angle calculation unit, reference numeral 8 denotes a switching timing determination unit, and reference numeral 9 denotes a transmission switching unit.

Next, the operation will be described. When the radio wave shield 3 is present on the moving object in the direction 1 for tracking the communication satellite of the moving object mounted antenna that changes every moment according to the movement of the moving object, normal reception is performed without being affected by the shielding. Have a pair of antennas 2a, 2a,
2b and transmission / reception separators 4a, 4b connected to each other
And the configurations of the receiving units 5a and 5b are usually used. Since the transmitting unit 6 normally has one configuration due to restrictions on the number of line channels, power consumption, and the like, transmission to a satellite is obstructed by transmission waves radiated from an antenna due to the radio wave shield 3 on the mobile body. It is used by switching to one of the antennas so that there is no such antenna. The transmission wave radiated from the pair of antennas 2a or 2b has a relative radio path difference ΔR shown in Expression 1. ΔR = nλ + Δr (1) That is, the relative phase between the transmission waves radiated from the pair of antennas 2a or 2b can be expressed by Expression 2. (ΔR / λ) · 2π = {n + (Δr / λ)} · 2π (2) where n: integer, λ: radio wave wavelength, and Δr <λ.

In the case of the DS-SSMA communication system, the timing when the relative phases of the transmission waves from both antennas are aligned, that is, (ΔR / λ) · 2π = 0 (3) or (Δr / λ) · 2π = 0 ( 4) Since it is necessary to drive the transmission switch 9 at a timing satisfying the following condition, the switching timing determination unit 8 calculates ΔR based on the signal from the antenna directivity angle calculation unit 7 and calculates ΔR =
The transmission switch 9 is driven by determining a timing of 0 or a timing of Δr = 0 at which a transmission wave from one antenna is applied to the radio wave shield 3.

[0005]

In order that the receiver of the other party in communication does not lose synchronization of carrier recovery due to antenna switching on the transmitting side, the switching timing determination accuracy is determined by the azimuth / posture reference accuracy of the moving object, Including mechanical accuracy, calculation accuracy, and electrical wavelength accuracy, the following values are required. λ · (± 30 ° / 360 °) = ± λ / 12 (5) According to Equation 5, when the wavelength of the radio wave used for communication is short, it is more difficult to maintain and maintain the accuracy, and the synchronization is lost during communication. Is more likely to occur. In the conventional antenna switching method, there is a problem that the probability of occurrence of bit loss or communication interruption due to loss of synchronization with the receiver of the communication partner during antenna switching is high due to the difficulty in securing the accuracy of switching timing determination as described above. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an antenna switching system which eliminates bit loss and communication interruption due to loss of synchronization of a receiver of a communication partner due to switching of a transmitting antenna. The purpose is.

[0007]

In order to achieve the above object, an antenna switching method according to the present invention is directed to a mobile-mounted antenna device for performing satellite communication, comprising: a plurality of antennas constituting space diversity; And a phase difference detector for measuring a relative phase between received carrier waves corresponding to the antenna, and an antenna for calculating an antenna directional angle for tracking the communication satellite based on information on the position of the communication satellite and the azimuth / posture of the moving object. A directivity angle calculation unit, and determines the timing at which the phases of the transmission radio waves between the antennas are aligned based on the output of the phase difference detector and the output of the antenna directivity angle calculation unit, and determines the timing between the antenna and the transmission unit based on the timing. Is switched.

[0008]

In the antenna switching system according to the present invention configured as described above, the condition of the relative phase of the carrier received by a plurality of antennas from the communication satellite, and the information on the position of the communication satellite and the azimuth / posture of the moving object are stored. The condition of the calculated radio path difference alone is determined by determining the switching timing of the transmitting antenna, together with the radio path difference condition between a plurality of antennas, based on the antenna directivity angle for tracking the communication satellite calculated based on the calculation. In this case, the timing determination accuracy can be increased as compared with the case of (1).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a view for explaining an embodiment 1 of an antenna switching system of a mobile-mounted antenna device according to the present invention. In the figure, reference numeral 1 denotes a direction in which a mobile satellite mounted on a mobile object changes with the movement of the mobile object to track a communication satellite, and 2a, 2b
Is a pair of antennas mounted on the moving body, 3 is a radio wave shield on the moving body, 4a and 4b are transmission / reception separators, 5a and 5b are reception sections,
6 is a transmitting unit, 7 is an antenna directivity angle calculating unit, 8 is a coarse / switching timing determining unit, 9 is a transmission switch, 10 is a phase difference detecting unit, 11 is a fine / switching timing determining unit, and 12 is an AND circuit. .

Here, the pair of antennas 2a and 2b and the corresponding receivers 5a and 5b constituting the space diversity of the mobile-mounted antenna apparatus are not affected by the radio wave shield 3 before switching the antennas. It is assumed that received waves from communication satellites are received and carrier waves are reproduced. Based on the signal from the antenna directivity calculator 7 for calculating the antenna directivity for tracking the communication satellite based on the information on the position of the communication satellite and the direction and attitude of the mobile unit, the coarse / switch timing determiner 8 The relative radio path difference ΔR of the antenna is calculated. When (ΔR / λ) <1, the timing condition signal is output to the AND circuit 1.
Send to 2. On the other hand, the respective reproduced carrier phases detected by the receivers 5a and 5b are sent to the phase difference detector 10, where the relative phase difference between them is detected, and then the phase difference (Δr / λ) · 2π is sent to the AND circuit 12 with a timing condition signal that is zero.

The AND circuit 12 enters the range of antenna switching under the condition of (ΔR / λ) <1 (coarse status), and within the range, one wavelength under the condition of (Δr / λ) · 2π = 0. Is zero (fine status), and the transmission switch 9 can be driven with accurate timing. Note that the refinement / switching timing decision unit 11 uses the reproduced carrier of both receivers, that is, the phase of the intermediate frequency obtained by heterodyne detection of the received radio wave, to obtain the condition of (Δr / λ) · 2π = 0. This is possible because the phase of the radio wave received from the antenna is maintained. The same applies to the reverse case where the intermediate frequency is converted into the transmission radio wave.

Furthermore, the permissible accuracy of calculation of the radio path difference ΔR is about the same as one wavelength (λ) of the radio wave to be used, and only about 12 times the conventional value, so that the reference accuracy of the azimuth / posture of the moving object and the mechanical accuracy are sufficient. There is an advantage that the calculation accuracy and the like can be reduced.

In the first embodiment, switching between a pair of antennas and one transmitting unit constituting space diversity has been described. However, the present invention is not limited to a pair of antennas, and switching between a plurality of antennas and a transmitting unit is not limited. The same applies to switching.

In the first embodiment, the antenna switching timing is determined by using both the condition of the calculated radio path difference and the condition of the relative phase of the received carrier, but the relative phase difference condition of the received carrier is determined. Instead, the phase of one or both of the transmission signals is corrected by the phase shifter using the detected phase, and the phases of the transmission waves from both antennas are aligned in advance. The same effect as that of the first embodiment can be obtained even if the switching is performed by using.

[0015]

As described above, according to the present invention, in a mobile-mounted antenna apparatus for performing satellite communication, a relative phase between a plurality of antennas constituting space diversity and a reception carrier corresponding to the antenna from a communication satellite is obtained. And a phase difference detector for measuring an antenna directional angle for tracking a communication satellite based on information on the position of the communication satellite and the azimuth / posture of the moving object, and the phase difference detector By the output and the antenna directivity angle calculation unit output, the timing at which the phases of the transmission radio waves between the antennas are accurately determined,
By switching between the antenna and the transmitting unit based on the timing, it is possible to obtain an antenna switching method that eliminates bit loss or communication interruption due to loss of synchronization of a communication partner receiver due to antenna switching.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of an antenna switching system of a mobile-mounted antenna device according to the present invention;

FIG. 2 is a diagram illustrating an antenna switching method of a conventional mobile-mounted antenna device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Communication satellite tracking direction 2a, 2b Antenna 3 Radio wave shield 4a, 4b Transmitter / receiver separator 5a, 5b Receiver 6 Transmitter 7 Antenna directivity angle calculator 8 Coarse / switching timing determiner 9 Transmission switcher 10 Phase difference detector 11 Fine / switching timing decision unit 12 AND circuit

Claims (1)

(57) [Claims] 1. A mobile-mounted antenna device for performing satellite communication, comprising: a plurality of antennas constituting space diversity; a phase difference detector for measuring a relative phase between received carrier waves corresponding to the antenna from a communication satellite; An antenna pointing angle calculation unit that calculates an antenna pointing angle for tracking a communication satellite based on information on the position of the satellite and the direction and attitude of the moving object,
The output of the phase difference detector and the output of the antenna directivity angle calculation unit determine the timing at which the phases of the transmission radio waves between the antennas are aligned, and switch between the antenna and the transmission unit based on the timing. Antenna switching method.