JPS6232663B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a wireless communication system that transmits signals from a terminal station through an intermediate relay station, which is widely used in terrestrial microwave communication systems, or an SCPC using a satellite.
The present invention relates to a method of measuring the oscillation frequency of a local oscillator of each intermediate relay station or each slave station in wireless communication such as signal transmission, in which a master station communicates with two or more slave stations.

In the above communication system, the oscillation frequency of the local oscillator of each intermediate relay station or each slave station is highly stable and precisely matches the specified frequency.
At worst, it is required that the frequency deviation between each oscillator is minute.

Therefore, a highly stable crystal oscillator has come to be used as a frequency reference source for each local oscillator, but a frequency counter has generally been used to measure the frequency.

Nowadays, crystal oscillators are used as the frequency reference source for each local oscillator, and have a stability comparable to the crystal oscillators used in frequency counters.A new frequency measurement method is now needed. It's here.

In addition, when measuring by moving the frequency counter, a long warm-up is required in order for the oscillation frequency of the highly stable crystal oscillator, which is the frequency reference source inside the frequency counter, to match the specified frequency and become stable. It was hot.

SUMMARY OF THE INVENTION An object of the present invention is to provide a frequency measurement method that allows highly accurate frequency measurement using a low-cost frequency measurement device and also reduces frequency deviation of the local oscillator of each intermediate relay station or slave station.

In order to achieve the above object, the frequency measurement method according to the present invention transmits signals from a terminal station through an intermediate relay station in a wireless communication system, or from a master station through a common intermediate medium such as a transbonder on a satellite in a satellite communication system. Alternatively, in a method of measuring the oscillation frequency of a local oscillator of the terminal station or slave station using a frequency counter in a wireless communication system in which signals are directly transmitted to two or more slave stations, the transmission signal from the terminal station or master station is A signal with a constant repetition frequency having a center frequency at a distant frequency is subjected to FM modulation and transmitted, and an oscillator output that is phase-synchronized with the modulated wave is used as a signal for creating the time interval of the frequency counter.

According to the above method, the oscillation frequencies of the local oscillators of each intermediate relay station or slave station can be maintained without shifting from each other, and the frequency counter used does not require an oscillator inside it, leading to a low cost range and making it easy for terminal stations etc. By using a highly stable oscillator, the accuracy of the frequency counter of each slave station, etc. can be maintained, and the object of the present invention can be completely achieved.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows an embodiment of the first invention. In the figure, 1 is a radio device located at a terminal station, 2 is a radio device located at an intermediate relay station, and terminals 11 and 12 attached thereto.
are measurement terminals for monitoring the receive and transmit local oscillator frequencies. 3 is a frequency counter, the measurement signal input terminal is 10, and 10 and 1
1 or 12, the frequency of each local oscillator is measured. Another terminal 9 added to the frequency counter 3 is a terminal for inputting an external time interval.

In this embodiment, since a communication method is shown in which signals are continuously transmitted from a terminal station through an intermediate relay station, a similar radio device is connected further from the intermediate relay station radio device 2. In the figure, they are shown with broken lines and arrows and are omitted. Furthermore, although an antenna, a feeder, etc. are inserted between radio devices 1 and 2, they are omitted.

8 is an input terminal of the wireless section in the terminal station,
The transmission signal is input from here. 4 is a reference oscillator that determines the reference frequency of the frequency counter, and 5 is a signal that generates a subcarrier that is FM modulated.
It is an FM modulator. The transmission signal and the FM modulated subcarrier pass through radio 1 and reach radio 2. The signal branched by the radio device 2 is demodulated to a reference frequency by an FM demodulator 6, noise is compressed by a phase-locked loop 7, and the frequency is changed to a desired frequency, which is used as a time interval input to a frequency counter. According to the method of the present invention, since the time interval of the frequency counter 3 is controlled by the frequency of the oscillator 4, an internal oscillator of the frequency counter is not required, and if only the oscillator 4 is made highly stable, the frequency counter of each slave station can be controlled by the frequency of the frequency counter 3. accuracy can be maintained.

Further, there is no need for warm-up due to counter movement, and frequency deviations between local oscillators can be reduced by measuring the frequencies of the local oscillators of each slave station at approximately the same time.

Next, an embodiment of the second invention will be described with reference to FIG. 1, 2, and 3 in the figure are the same as in FIG. 8 is a transmission signal input terminal for the radio section in the terminal station, 9 is a time interval input terminal for the frequency counter, 1
0 is an input terminal for frequency measurement, and 11 is a measurement terminal for frequency monitoring of the receiving local oscillator of the radio device 2.
Terminal 11 is connected to terminal 10 and frequency measurement is performed. 13 is a digital modulator, which has a clock generator inside. 14 is a digital demodulator, which has a clock recovery circuit inside. The recovered clock is connected via terminal 15 to the external time interval input terminal 9 of the frequency counter. Since the present invention does not use a subcarrier for reference frequency transmission, the signal transmission band is more advantageous than the first invention. Since the effects of the present invention are the same as those of the first invention, the explanation thereof will be omitted.

The embodiments of the inventions have been described above in a communication system in which signals are transmitted in series between a terminal station and each intermediate relay station, but in a communication system in which signals are transmitted and received between a master station and two or more slave stations. can also take the same approach.

When transmitting signals from the slave station to the master station using TDMA, the frequency of the signals from each slave station is often synchronized due to the operation of the carrier regeneration circuit of the digital demodulator in the master station. must be in place. Furthermore, when signals are transmitted from the slave station to the master station using SCPC, the relationship between the signals from each slave station must be constant so that the guard band between channels is not exceeded. Therefore, the method of the present invention, which allows maintenance to reduce the deviation of each local oscillator, has high practical value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a terminal station and an intermediate relay station for explaining an embodiment of the first invention, and FIG. 2 is a block diagram of a terminal station and an intermediate relay station for explaining an embodiment of the second invention. FIG. DESCRIPTION OF SYMBOLS 1...Terminal station radio equipment, 2...Intermediate relay station radio equipment, 3...Frequency counter, 4...Reference frequency oscillator, 5...FM modulator, 6...FM demodulator, 7
...Phase synchronized circuit, 8...Transmission signal input terminal, 9
...External time interval input terminal, 10... Frequency measurement signal input terminal, 11... Terminal for frequency monitoring of the receiving local oscillator of the radio device, 12... Terminal for frequency monitoring of the transmitting local oscillator of the radio device, 13...
...Digital modulator of terminal station, 14...Digital demodulator of intermediate relay station, 15...Clock output terminal.

Claims (1)

[Claims] 1. A wireless communication system in which signals are transmitted from a terminal station through an intermediate relay station, or a signal is transmitted from a master station to a satellite communication system through a common intermediate medium such as a transbonder on a satellite, or directly between two or more In a method of measuring the oscillation frequency of a local oscillator of the terminal station or slave station using a frequency counter in a wireless communication system in which signals are transmitted to and from a slave station, a center frequency is set at a frequency distant from the transmission signal from the terminal station or master station. A frequency measuring method characterized by transmitting a signal with a constant repetition frequency with FM modulation, and using an oscillator output that is phase synchronized with the modulated wave as a signal for creating a time interval of the frequency counter. 2 Wireless communication system in which signals are transmitted from a terminal station through an intermediate relay station, or signals are transmitted directly from a master station to two or more slave stations through a common intermediate medium such as a transbonder on a satellite in a satellite communication system. In the method of measuring the oscillation frequency of the local oscillator of the terminal station or slave station using a frequency counter in the wireless communication system, the clock component is transmitted from the terminal station or master station by being included in the transmission signal, and is reproduced. A frequency measuring method characterized in that an oscillator output phase-synchronized with the obtained clock signal is used as a signal for creating a time interval of the frequency counter.