JPS6080328A - Frequency synchronization system - Google Patents

Abstract

PURPOSE:To prevent frequency shift of a base band signal without using any highly accurate frequency reference by transmitting a pilot signal for frequency synchronization from the transmission side and forming the phase synchronization at the reception side with the said pilot signal. CONSTITUTION:A signal of a frequency f1 outputted from a pilot transmitter 2 is converted into a signal of frequency f2=(n/m)f1 at a frequency divider 3 in a single side band radio transmission line, generated into a frequency synchronization pilot signal having both-side bands of frequencies f1+ or -f2 at a modulator 4 by taking the frequency f1 as a center, the signals are synthesized with the base band signal and the result is transmitted. A signal of frequency f2 outputted via a prescribed demodulation means and a specific signal of frequency f1' corresponding to the frequency f1 outputted via a carrier regenerating means are referenced at the reception side and the phase locked loop is operated by using the relation that the frequencies f1, f2 is m:n so that the frequency f1' is equal to the f1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to frequency synchronization systems, and more particularly to improvements in frequency synchronization systems used in single sideband wireless transmission lines.

Conventionally, in single-sideband wireless transmission lines, because the carrier wave is removed and does not exist, the frequency that occurs between the frequency of the baseband signal demodulated on the receiving side and the original frequency of the baseband signal on the transmitting side. In order to reduce the deviation, for example, fully independent synchronization method, semi-independent synchronization method (
Various frequency synchronization methods are used, such as a one-frequency pilot transmission method and a carrier wave transmission method.

One of the technical problems in single sideband wireless transmission system is
There is a problem in how far the frequency shift between the baseband signals on the transmitting side and the receiving side can be reduced. Normally, this frequency shift is suppressed to about 1, for example, 0.03 Hz (hertz) within the range of the wireless transmission path. However, in the above-mentioned conventional frequency synchronization method, for example, in the case of the completely independent synchronization method, each of the transmitting/receiving terminal station and each relay station has

It is necessary to have a highly accurate frequency reference related to the frequency conversion function, and in the case of the semi-independent synchronization method, a similarly highly accurate frequency reference is required for a predetermined pilot signal that is combined into a baseband signal at the transmitting end station. Furthermore, in the case of the carrier wave transmission method, it is necessary to provide a frequency reference for a newly added baseband carrier wave. Due to the feasibility of filtering, the baseband frequency band has expanded, which is a significant negative factor from the perspective of effective frequency utilization, which is the original purpose of the single-sided wave transmission method. Each has its own drawbacks.

The object of the present invention is to eliminate the above-mentioned drawbacks and to form a pilot signal for one frequency cycle from three signals generated from a predetermined pilot oscillator through a predetermined modulation effect, thereby providing a highly accurate frequency signal. An object of the present invention is to provide a frequency synchronization method that can configure a single sideband wireless transmission line that can fully expect effective frequency utilization without requiring standards.

The frequency synchronization method of the present invention is a frequency synchronization method for a single sideband wireless transmission line, in which a frequency of 12-11 (m) is generated from a first signal of frequency f1.

n is a positive integer, m>n), and the second signal modulates the first signal by a predetermined modulation means, and the double-side band of the frequency f1±12 is generated with the frequency 11 of the first signal as the center. a pilot signal generating means for generating a third signal having a predetermined pilot signal as a predetermined pilot signal on the transmitting side;
In order to make the frequency of the baseband signal after reception demodulation equal to the frequency of the original baseband signal on the transmission side, predetermined demodulation is performed from the pilot signal having both side bands included in the baseband signal after reception demodulation. With reference to the second signal of frequency 12 outputted through the means and the specific signal of frequency G corresponding to the first signal outputted through the predetermined carrier regeneration means, The receiving side is provided with a phase synchronization means that operates so that the frequency 11' of the specific signal becomes equal to the frequency 11 of the first signal using the frequency ratio m:n of the two signals.

The present invention will be explained in detail below with reference to all the drawings.

FIG. 1 is a block diagram showing the main parts of both transmitting and receiving end stations in a single sideband wireless transmission line to which an embodiment of the present invention is applied. In general, not only single-sideband wireless transmission lines but also wireless transmission lines include a plurality of relay stations between both end stations corresponding to a predetermined transmission span. Relay stations are omitted to the extent necessary for explanation.

In FIG. 1, both transmitting and receiving terminal stations in a single sideband wireless transmission line to which the present invention is applied include a combiner l, a pilot oscillator 2, a frequency divider 3, and a modulator 4 on the transmitting terminal side.
, a mixer 5, a first transmission local oscillator 6, a single sideband filter 7, a mixer 8, a second transmission local oscillator 9,
It includes a bandpass filter 10, an amplifier 11, and a transmitting antenna 12.

On the fcS receiving side, a receiving antenna 13, a band filter 14, a mixer 15, a band filter 16, a mixer 17, and a second receiving local oscillator 18.

Baseband filter 19, demultiplexer 20, and demodulator 21
, a 1-phase detector 22 , a carrier recovery circuit 23 , a 1-frequency divider 24 , and a first reception local oscillator 25 .

In FIG. 1, a baseband signal inputted from a terminal 101 is combined with a frequency synchronization pilot signal inputted from a modulator 4 in a synthesizer 1, and outputted to a mixer 5. Figure 2 (al, (bl, (C1゜(d)
) and (f) in a single sideband wireless transmission line to which the present invention is applied. A frequency spectrum diagram of the signal at each stage on both the transmitting and receiving end stations is shown. The composite signal output from the aforementioned combiner l is shown in FIG.
In Figure (al), the frequency spectrum A of the baseband signal is formed by the frequency spectrum B of a plurality of one communication path, which corresponds to the number of lines. In FIG. 1, one of the first signals of frequency 11 output from the pilot oscillator 2 is input to the modulator 4, and the other is input to the divider 3. In the splitter 3, the frequency f1 of the first signal is divided by 1 to give a frequency of 12'' f1(m,
It is converted into a second signal where n is a positive integer (m>n) and sent to the modulator 4. In the modulator 4, the second signal modulates the first signal into AM, FM and P
The frequency 11 is modulated by any modulation means of M.
A third signal having double-side bands of frequencies 11±12 centered at , that is, a frequency synchronization pilot signal, is generated, and as described above, is input to the synthesizer l and combined with the baseband signal. The output signal of synthesizer l is.

It is input to the mixer 5 and mixed with the local oscillation signal of frequency 1 IP output from the first transmitting local oscillator 6 in the mixer 5, and as shown in FIG. A double-sideband signal is generated with frequency spectrum 2m D as the center, in which frequency synchronization pilot signals C-1 and C'-1 and Bebe band signals A-1 and A'-1 are arranged in both sidebands. - As an example, the fTIP is typically 60 MHz (megahertz).
selected according to the degree.

This double sideband signal is input to the single sideband filter 7, which filters the frequency synchronization pilot signal C-1 within the frequency spectrum shown in FIG. 2(b). It has a bandpass characteristic that allows the baseband signal A-1 to pass through, and a single sideband signal is output and input to the mixer 8. In the mixer 8, it is mixed with a local oscillation signal of frequency fTLo output from the second local oscillator 9 for transmission,
As shown in FIG.
A double sideband signal is generated in which the -2 and A/2 are placed in both sidebands. For example, in the case of a single sideband wireless transmission line in the 6 GHz band, the above fTL.

is selected as a predetermined frequency in the 6 GHz band.

This double sideband high frequency signal is input to the bandpass filter 10, similar to the case of the single sideband filter 7 described above.

One frequency synchronization pilot signal C-2 and baseband A-2 in the frequency spectrum shown in FIG. A single sideband high frequency signal formed by the frequency synchronization pilot signal and the baseband signal is amplified to a predetermined level and transmitted via the transmitting antenna 12.

On the receiving side, the single sideband high frequency signal received by the receiving antenna 13 is input to the mixer 15 via the bandpass filter 14 . In the mixer 15, it is mixed with a local oscillation signal of frequency fRLO output from the first receiving local oscillator 25.

FIG. 2 (dl) shows the relative relationship between frequency spectra C-2 and A-2 including the one-frequency synchronization pilot signal and baseband signal input to the mixer 15, and the frequency spectrum F of the local oscillation signal. Relationship is shown.Mixer 15
The output is filtered by a bandpass filter 16, outputted as a single sideband signal in an intermediate frequency band, and inputted to a mixer 17.

The frequency spectrum of this single sideband signal in the intermediate frequency band is shown in FIG. 2(e). In the mixer 17, the frequency f□0 . A predetermined baseband signal is output. In FIG. 2(e), the position of the frequency spectrum G indicated by the dashed line corresponds to the local oscillation signal of the frequency fRIF. Further, the frequency spectrum 2m of the baseband signal output from the mixer 17 is
This is the case as shown in Figure (f). The baseband signal is input to the splitter 20 via the baseband filter 19i, and through a predetermined splitting action, the baseband signal A shown in FIG. 2 (fl) is output via the terminal 102. On the other hand, the pilot signal C for frequency synchronization is sent to the demodulator 21 and the carrier recovery circuit 23. In the demodulator 21, the pilot signal C for frequency synchronization is transmitted to the AM, FM, and PM. It is demodulated in accordance with one of the modulation methods, and a second signal with a frequency of 12 is output and inputted to the phase detector 22.In addition, in the carrier regeneration circuit 23, the carrier wave component of the frequency synchronization pilot signal is is extracted and reproduced and inputted to the 1 frequency divider 24, and the frequency is divided by - and inputted to the phase detector 22.The frequency f1/ of the carrier wave component is 1 originally from the purpose of the 1 frequency synchronization method. , must be equal to the frequency f1 of the first signal at the transmitting side, and f
If the frequency synchronization method functions effectively so that 1'=f1, it would be a technical problem in single sideband wireless transmission lines. The frequency shift between the baseband signals on the transmitting side and the receiving side described above approaches zero. In the phase detector 22, the second
The signal and the frequency -frO frequency divided signal input from the 1 frequency divider 24 are input, phase detection is performed using the second signal as a reference signal, and a 1 phase error signal is outputted to the first receiving local oscillator 25. Sent. The first receiving local oscillator 25 is a voltage controlled oscillator whose oscillation frequency is controlled by the voltage of the S-type phase error signal.

As described above, in the form in which the second signal output from the demodulator 21 is used as the reference signal, the mixer 15° band filter 1
6. Mixer 17. Baseband filter 19. Duplexer 20
．． A phase-locked loop including a carrier regeneration circuit 23, a branching unit 241, a phase detector 22, and a first receiving local oscillator 25 is formed.

When this phase-locked loop is in constant operation, the frequency relationship at each stage in both the transmitting and receiving terminal stations is as shown in Figure 1, where the frequency transmitted from the transmitting terminal is (fTB/fTP ) 10fTIP+ f'rLo
- The frequency fRB of the baseband signal at the receiving terminal station is fRB = (fTB/fTP) + fT11 + fTLo -
fRLO-fRIP becomes O here・fTB and f
RB represents the frequency of the baseband signal at both the transmitting and receiving end stations, and fTP and fRP represent the modulated frequencies of the frequency synchronization pilot signals at both the transmitting and receiving end stations, respectively. Also − (fTB/ fTP) and (f,
B/fRP) indicates a composite frequency of a composite signal of a baseband signal and a frequency synchronization pilot signal at both transmitting and receiving terminal stations.

When the phase-locked loop is in a steady state of operation, on the transmitting side, the frequency composition of the frequency rotation pilot signal is defined as f2=-fl, so *f1'
It is clear that =11. From this, −f
It is also obvious that TB=fRB. That is, by applying the frequency synchronization method of the present invention), the frequencies of the baseband signals at both transmitting and receiving end stations in a single sideband wireless transmission line are maintained equal as described above.

As described above in detail, one aspect of the present invention is to provide a single-sideband wireless transmission line with frequency synchronization pilot signal generation means via a predetermined modulation means on the transmitting end station side, and the above-mentioned frequency synchronization pilot signal generation means on the receiving end station side. By providing phase synchronization means formed via both sideband signals of the pilot signal, there is an effect that the frequency deviation of the baseband signal at both the transmitting and receiving terminal stations can be made almost zero.

[Brief explanation of drawings]

FIG. 1 shows a single sideband wireless transmission line to which an embodiment of the present invention is applied. Block diagram showing the main parts of both transmitting and receiving terminal stations, Fig. 2 (a), (bl, (c), (d))
, (e) and (f) are frequency spectrum diagrams of signals at each stage of the transmitting and receiving terminal stations, respectively. In the figure, 1... combiner, 2... pilot oscillator, 3°24... frequency divider, 4...
. . . Modulator, 5, 8, 15. 17 . . . Mixer, 6 . . . First transmission local oscillator, 7. ...
...Single sideband filter, 9...Second transmission local oscillator. 10.14.16...Band filter, ll...
···amplifier. 12...Transmitting antenna, 13...Receiving antenna. 18...Second reception local oscillator, 19...
・・Baseband filter, 20 ・・・・Brancher, 2
1... Demodulator, 22... Phase detector,
23... Carrier wave regeneration circuit. 25...First receiving local oscillator. l' Agent Patent Attorney Uchihara Disobeys,

Claims (1)

[Claims] In the frequency synchronization system of a single sideband wireless transmission line, through a predetermined modulation means for the first signal by the signal of the frequency box 2 generated from the first signal of one frequency 11, The frequency fl±1 is centered around the frequency fl of the first signal.
A pilot signal generating means for generating a third signal having two sidebands as a predetermined pilot signal is provided on the transmitting side, and the frequency of the baseband signal after reception demodulation is made equal to the frequency of the original baseband signal on the transmitting side. From the pilot signal having both side bands included in the baseband signal after receiving and demodulating. Frequency 1 outputted through predetermined demodulation means, respectively.
2 and a specific signal of frequency f□' corresponding to the first signal outputted via a predetermined carrier wave reproducing means, the first and second signal frequency ratio m is determined.
:n relationship, the frequency f; of the specific signal is the first
A frequency synchronization method characterized in that a receiving side is provided with phase synchronization means that operates so that the frequency of the signal becomes equal to the frequency 11 of the signal.