JPS5887928A - Space diversity system - Google Patents

Abstract

PURPOSE:To avoid the quality of line from being deteriorated even with indefinite spectrum like an SSB signal, by inserting a pilot signal newly and providing the phase modulation only for the pilot signal. CONSTITUTION:An output of a pilot oscillator 13 is branched into two; one is applied to a synthesizer 15 and another is modulated at an output of a sensing oscillator 4 at a phase modulator 3 and applied to a synthesizer 16. A transmission signal is branched into two; one is applied to an antenna 5 and another is applied directly to an antenna 6. A signal received at an antenna 7 is applied to a receiver 8. A pilot signal is picked up at a filter 17 and a level detector 9 detects the envelope of the pilot signal. The phase difference between the envelope detected at a phase detector 10 and a sensing signal through a fixed phase device 11 is detected. Based on the detected phase difference, a variable phase device 2 is controlled to keep the pilot signal at the same phase at the reception antenna 7 at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission diversity system in wireless communication of signals whose spectrum is undefined and which are easily degraded by sensing phase modulation.

FIG. 1 shows a transmission space diversity system that has been conventionally used in microwave band FM systems.

1 is a distributor, 2 is a variable phase shifter, 3 is a phase modulator, 4 is a low frequency oscillator (hereinafter referred to as a sensing oscillator), 5.6 is two spatially separated transmitting antennas, and 7 is a receiving antenna. , 8 is a receiver, 9 is a level detector, 10 is a phase detector, 11 is a fixed phase shifter, and 12 is a control circuit.

Here, among the transmission signals split into two by the divider 1,
One receives phase displacement by a variable phase shifter 2, and the other receives phase modulation by a phase modulator 3 driven by a sensing oscillator 4. The signals are transmitted from antennas 5 and 6, respectively.

Here, as shown in FIG. 2, one side is passed through a phase modulator, so when expressed as a vector, da, db, and dC change in accordance with the phase change caused by the sensing signal. Therefore, two signal receiving antennas 7, 10 receivers 8
As shown in the waveform diagram of FIG. 2, the level detector 9 connected through the sensor detects the envelope component, the sensing signal component, and its harmonic component.

Here, as shown in FIG. 2, when the phases of the two received signals change depending on the amount of phase shift of the variable phase shifter 2 and the propagation conditions between the transmitting antenna 5, 6, and the receiving antenna 7, the level is detected. The polarity and amplitude of the sensing signal component of the sensor 9 fluctuate.

Figure (a) shows the case where the signal that has not undergone phase modulation and the received signal are in phase, and Figure (b) shows the case where the phase of the signal that has not undergone phase modulation is delayed; (c) shows a case where the phase of a signal not subjected to phase modulation is advanced, and (d) of the same figure shows the sensing oscillator output waveform.

This polarity and amplitude are detected by a phase detector 10 connected to the output of the sensing oscillator 4 via a fixed phase shifter 11 that corrects phase shifts due to propagation, so that the two transmitted signals are always the same regardless of changes in the propagation conditions. It becomes possible to control the variable phase shifter 2 via the control circuit 12 so that the signal is received in phase.

FIG. 3 is a diagram showing the frequency spectrum of the transmitted signal. Reference numeral 21 in FIG. 3(a) indicates the spectrum of the FM signal.

23 in the same figure (b) shows the spectrum of the SSB signal,
22 indicates a pilot signal 0 The conventional space diversity method is effective for signals such as the FM signal in Figure 3 (a), where a spectrum always exists and where there is little deterioration in line quality due to phase modulation of the main signal. It is.

However, it has the disadvantage that it is difficult to apply it to a signal such as the SSB signal shown in FIG. 3(b), where the spectrum is unstable and the line quality deteriorates significantly due to level fluctuations. In order to eliminate these drawbacks, the present invention is characterized by inserting a new pilot signal into the signal and applying phase modulation only to the pilot signal.The purpose of this invention is to eliminate deterioration of line quality regardless of the signal spectrum. There is no need to realize a transmit diversity scheme.

FIG. 4 shows an embodiment of the present invention, in which 13 is a pilot oscillator, 14 is a distributor, 15 and 16 are combiners, and 17 is a P-wave generator for selectively extracting pilot signals.

Here, the oscillation frequency of the pilot oscillator 13 is selected in the gap of the signal spectrum, and its output is divided into two by the divider 14.
A phase modulator 3 is inserted into one of them, and the signals split into two by the divider 1 are combined with the same phase relationship by the combiners 15 and 16, and one is passed through the variable phase shifter 2, It is transmitted by antennas 5 and 6.

The signal received by the antenna 7 passes through the receiver 8, a pilot signal is extracted by the Oki waver 17, and the level detector 9 extracts the pilot signal.
The envelope component of the pilot signal is detected. As previously explained using FIG. 2, the envelope component varies depending on the phase shift amount of the variable phase shifter 2 and the propagation conditions between the transmitting antennas 5 and 46 and the receiving antenna 7. Similarly, by performing phase detection on the sensing signal and controlling the variable phase shifter 2 using the detected signal, the pilot signal can be controlled so that it always has the same phase at the receiving antenna 7. Therefore, signals can be received in the same phase by the receiving antenna 7 without applying phase modulation. FIG. 5 shows another embodiment of the present invention, in which 17 is a local oscillator, 18 is a distributor, 19 and 20 is a frequency converter. Similarly to the embodiment shown in FIG. 4, in the intermediate frequency band, the output of the local oscillator 17 is split into two signals by a divider 18 into which a pilot signal has been inserted, and one signal is sent through a variable phase shifter 2. Accordingly, the frequency converter 19 and the frequency converter 20
Since the signals are mixed in the signal path, it is possible to provide a phase change as well as a frequency conversion, and it is possible to obtain the same effect as by inserting the phase shifter 2 in the signal path.

Although the phase modulator 3 and the variable phase shifter 2 are inserted in the path related to one transmitting antenna here, they may be inserted in the path related to both transmitting antennas. Further, although the fixed phase shifter 11 is inserted on the sensing oscillator 4 side of the phase detector 10, it may be inserted on the level detector 9 side.

As explained above, since the pilot signal is inserted into the gap in the signal spectrum, the transmit diversity method can be realized even for signals with uncertain spectra.
Further, since the sensing phase modulation that is not received in the same phase is applied only to the pilot signal, there is an advantage that the signal is not affected by deterioration such as level fluctuation due to phase modulation.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the conventional space diversity system, Figure 2 is a diagram of the principle of in-phase synthesis using sensing phase modulation,
Figure 3 (a) is the spectrum of the FM signal, Figure 3 (b)
is a spectrum of an SSB signal with a pilot signal inserted, FIG. 4 is an embodiment of the space diversity system according to the present invention, and FIG. 5 is a spectrum of another space diper'/according to the present invention.
This is an example of the f method. 1...Distributor, 2...Variable phase shifter, 3...
Fist... Phase iiM [, 4... Sensing oscillator, 5, 6... Transmitting antenna, 7 m5sss
Receiving antenna, 8111+1+11@receiver, 9...
・・Level detector, 10・・・Fist/phase detector, 11・
...Fixed phase shifter, 12Φ...Control circuit, 13 life...Pilot oscillator, 14...eII-divider,
15, 16...Fist/Φ combiner, 17...Local oscillator, 18...Sachi/distributor, 19゜20...Frequency converter, 21...FM signal spectrum, 2
2...Pilot signal, 23...-SSB signal spectrum agent Patent attorney Honma
Diagram Z

Claims (2)

[Claims] (1) The signal to be transmitted is split into two, a pilot signal oscillator is provided, the pilot signal output is split into two, one of which is combined with one of the branched transmission signals, and one of the split pilot signals is combined with the other of the branched transmission signals. The other one is phase modulated with a low frequency signal, the pilot signal subjected to the phase modulation and the other one of the branched transmission signals are combined, and at least one of the two combined outputs is made variable. After the phase is shifted by a phase shifter, the radio waves are guided to separate antennas and radiated from the antennas, the radio waves radiated from the two antennas are received, and the signal at the pilot signal frequency is selectively extracted by a filter. Then, detect the envelope amplitude level, correct the phase shift due to radio wave propagation between the detection signal and the low frequency signal used for the phase modulation, perform phase detection, and use the phase detection output to Space diversity characterized by driving a phase shift control circuit of the variable phase shifter and controlling the variable phase shifter so that the phases of radio waves radiated from the two antennas at a receiving point are equal. method. (2) A local oscillator, a divider that divides the output of the local oscillator into two, and a frequency converter that converts the frequency of two combined signals consisting of a pilot signal and a transmission signal using the local oscillation frequency signal from the divider. Claim (1) characterized in that two variable phase shifters are added, and a variable phase shifter is placed between at least one output end of the distributor and a corresponding frequency converter. Space diversity method described.