JPH01318334A - Double polarized wave transmission system - Google Patents

Abstract

PURPOSE:To eliminate the need for the time division multiplexing of a frame synchronizing signal and a parity detection signal and to decrease the modulation speed by providing a means applying phase synchronization to the modulation speed between both polarized waves. CONSTITUTION:The signal fed to terminal A, B is converted into signals synchronized with each other by using a clock from a master clock generator 1 with stuff synchronization/multiplexer circuits 2, 2' and an overhead bit is multiplexed. The multiplex signal is converted into a signal proper to the radio transmission by modulators 3, 3' at the IF band respectively and converted into a high frequency radio frequency by transmitters 4, 4'. Moreover, the modulation speed of the one of two modulation waves is in the relation of (M/N)Xf0 (M, N are positive integers), where f0 is the modulation speed of other modulation wave. Thus, it is not required to apply multiplexing of a frame synchronizing signal and a parity signal for both polarized channels and the modulation speed is decreased and the efficient transmission is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wireless digital transmission system, and more particularly to a method for controlling modulation rates between polarized waves in a dual polarized wave transmission system that aims to effectively utilize a radio frequency band.

[Conventional technology]

In conventional dual polarization transmission systems, although the nominal values of the modulation rates between the two polarizations may match, phase synchronization with each other is not achieved.

In the dual polarization transmission system, an important issue is how to reduce interference between the two polarizations. This amount of interference depends on the cross-polarization discrimination degree (XPD) of the antenna used. However, it is difficult to ensure a stable and high XPD due to fading that occurs in the radio propagation path. For this reason, in single-polarization transmission, a method is often adopted in which a cross-polarization interference canceller (xpIC) is used to achieve the required XPD and ensure the operating efficiency of the two lines. This πIC is operated by a control signal obtained by mutually transmitting signals demodulated between one and both polarized waves.

[Problem to be solved by the invention]

However, in the conventional system, the control circuit is complicated because the modulation speeds between the eight polarized waves are asynchronous.

It is necessary to time-division multiplex overhead pits (for example, a frame synchronization signal, a noise detection signal) independently on both sides, which has the disadvantage of increasing the modulation rate.

[Means to solve the problem]

The circularly polarized wave transmission system according to the present invention includes means for phase-synchronizing the modulation speeds between both end waves using the same center frequency, and sets one of the modulation speeds to f. When the other modulation speed is NXf
It is characterized by phase synchronization as o (M and N are positive integers).

〔Example〕

Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 shows nine embodiments of the present invention. here.

The structure up to the antenna on the left is the transmitting side, and from the antenna on the right is the receiving side. Terminals A and H are supplied with signals to be transmitted. These signals are asynchronous to each other. These signals are converted into mutually synchronized signals by the stuff synchronization/multiplexing circuits 2, 2' using the clock from the main clock generator 1, and the relative and overhead bits are multiplexed. These multiplexed signals are each IF
After being converted into a signal suitable for wireless transmission by modulators 3, 3' in the 'band, it is converted to a high frequency radio frequency in the transmission 1jA4, 4'. The outputs of the transmitters 4 and 4' are transmitted as V-polarized and H-polarized signals of the transmitting antenna, respectively.

Note that the modulation speed of one of the two modulated waves is f.

When closing, the modulation speed of the other side only needs to have a relationship of NXfo (M and N are positive integers), and is highly versatile.

On the receiving side, these double-ended signals are sent to receivers 5 and 5, respectively.
The signal is converted into an IF frequency by 5', and the interference is removed through cross-polarization interference cancellers 6 and 6'.

The outputs of the cross-polarization interference removers 6 and 6' are reproduced as baseband signals by demodulators 7 and 7', respectively.

Furthermore, by the destuffing/separation circuits 8 and 8', terminal C receives a reproduced signal of the signal supplied to terminal A on the transmitting side, and terminal C receives a reproduced signal of the signal supplied to terminal B on the transmitting side, respectively. Output.

FIG. 2 shows a block configuration of an XPIC (cross-polarization interference canceller) and its control circuit. Here, block BA is
PIC, blocks BB, and BC are demodulators on the H and V polarization sides, respectively, and block BA' is an XPIC control unit. In the H polarization demodulator BB, interference components from the V polarization that interfered with the H polarization are detected as error signals EP, E. XP
The IC control unit BA' converts the error signals EP, E, and demodulated baseband signals DP, D, from the V polarization demodulator BC.
The interfering signal on the H polarization side (V polarization signal) is removed by integrating the results and controlling the variable weight circuits WC, two of which are provided for each tap of the XPIC.

Note that if the modulation speeds on the H polarization side and the V polarization side are asynchronous with each other, the above-mentioned operation to obtain the correlation becomes extremely difficult. This is because the data seen from one side is always moving in time, and there are cases where it is difficult to establish a correlation.
This is because the operation of the PIC may become unstable.

〔Effect of the invention〕

As explained above, in the present invention, the modulation speed (modulation frequency) between one polarized wave is synchronized in phase, so that simple and extremely stable XPIC control is possible. or.

Since there is no need to multiplex the frame synchronization signal and the quality signal into both polarization channels, the modulation rate can be lowered and efficient transmission can be achieved.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a specific example of the XPIC shown in FIG. 1 and its control-related circuits. In the figure, 1: Main clock generator, 2, 2': Stuff synchronization/multiplexing circuit, 3, 3': Modulator, 4, 4
': Transmitter, 5, 5': Receiver, 6, 6-system cross-polarization interference remover, 7, 7': Demodulator, 8, 8':
Destuff/separation circuit.

Claims (1)

[Claims] 1. In a wireless dual-polarization transmission system for transmitting digital signals, there is a means for phase-synchronizing the modulation speeds of both polarizations using the same center frequency, and when one of the modulation speeds is f_0, the other modulation speed is A dual polarization transmission method characterized by phase synchronizing as M/N×f_0 (M, N: positive integers).