JPS60126931A - Frequency generation system of radio communication system - Google Patents

Abstract

PURPOSE:To reduce requirements of a modulator demodulator greatly by using a single high-stability original oscillator which is synchronized with a high-stability external clock frequency as a common original oscillator for an earth station and a satellite, and generating plural desired radio frequency signals, an intermediate frequency signal, and a clock signal. CONSTITUTION:The earth station 26 is provided with the original oscillator 27 which is synchronized with the external clock frequency. For example, a high- stability digital clock supply device 20 provided in a ground network 28 supplies the clock signal to the original oscillator 27, which is then synchronized with the clock signal. The original oscillator 27 is a phase locked loop and a phase comparator 32 makes a phase comparison between the output of a VCO31 and the clock signal of the clock supply device 29 and supplies its comparison output to the VCO31 as a control signal. This highly stabilized clock 33 is branched into many signals and one of them is converter into a high-stability frequency signal close to a radio frequency by the phase-locked loop 38 which consists of a phase comparator 34, low-pass filter 35, voltage-controlled oscillator 36, and frequency divider 37.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frequency generation system for generating radio frequency signals, intermediate frequency signals, and baseband processing clock signals required in a wireless communication system.

<Prior Art> Figure 1 shows the configuration of an original oscillator in a conventional satellite communications earth station. A baseband signal processing device 11, a modulation/demodulation device 12, and a radio frequency device 13 are connected in cascade, and an original oscillator for generating a lock necessary for the baseband signal processing device 11 in order to generate frequency signals necessary for these. 14, a source oscillator 15 for obtaining an intermediate frequency signal necessary for the modulation/demodulation device 12, and a source oscillator 16 for generating a radio frequency signal necessary for the radio frequency device 13 are provided, respectively. The output of the original oscillator 14 is a phase-locked loop 17
is converted into a signal with a frequency m times higher. Phase locked loop 1
7 is a voltage controlled oscillator (hereinafter referred to as Vc).

The phase comparison output of
18 as a frequency control signal, an output that is 1n times the output frequency of the original oscillator 14 and is phase-synchronized is VC01.
Obtained from 8. The output of the phase-locked loop 17, that is, V
The output of the CO 18 is divided by n, . . . 01 by the frequency dividers 22, . Supplied as. Also, the original oscillator 15
．． 16 are frequency multipliers 24 and 25, respectively, which convert the signals into intermediate frequency signals and radio frequency signals of desired frequencies, and supply them to the modulation/demodulation device 12 and the radio frequency device 13, respectively.

In this way, in the conventional wireless communication system, the source oscillator 14 for generating the clock to be supplied to the baseband signal processing device 11, the source oscillator 15 for generating the intermediate frequency signal to be supplied to the modulation/demodulation device 12, and the radio frequency The original oscillators 16 for generating radio frequency signals supplied to the device 13 operate independently, and the stability of the clock frequency, intermediate frequency, and radio frequency depends on the stability of the respective original oscillators 14, 15, and 16. depended on.

In addition, the stability of the primary oscillator 16 that generates high frequencies, such as radio frequencies, cannot be very high due to problems with the elements, and the primary oscillator for high frequencies has low stability. was there. Furthermore, the frequency deviation seen from the entire system is the sum of the frequency deviations of the respective original oscillators 14, 15, and 16, resulting in a system with poor frequency stability as a whole. This also has the disadvantage that the requirements for the modulation/demodulation device 12 become stricter.

The above is about satellite communication earth stations, but satellite stations also have a primary oscillator for the clock frequency supplied to the signal processing device on the satellite, a primary oscillator for intermediate frequency signals, and a primary oscillator for radio frequency signals. In the conventional system, the oscillators operate independently, and have the same configuration as the original oscillator at the earth station described above. Furthermore, because the environment on a satellite is much harsher than on the ground, the primary oscillator on a satellite has the disadvantage of being less stable than on an earth station.

<Summary of the Invention> In order to solve this drawback, the present invention sub-synchronizes the primary oscillator of the earth station to the highly stable lock frequency of the terrestrial network with a stability of 1o-11 in the earth station, and The primary oscillator on the satellite is slave-synchronized to the clock generated by the earth station's primary oscillator, which is slave-synchronized to the highly stable lock frequency. The configuration is such that a plurality of required radio frequency signals, intermediate frequency signals, and clock signals are generated using a common source oscillator.

<Embodiment> Figure 2 shows an embodiment in which this invention is applied to an earth station.
Components corresponding to those in FIG. 1 are given the same reference numerals. The earth station 26 is provided with an original oscillator 27 which is slave-synchronized to an external clock frequency. For example, a highly stable digital clock supply device 29 (for example, an 8.19 MH2 cesium oscillator is used) provided in the terrestrial network 28 is supplied to the primary oscillator 27, and the primary oscillator 27 is synchronized with this. The original oscillator 27 is a phase-locked loop, and the VC
The output of O31 and the clock signal of clock supply device 29 are phase-compared by phase comparator 32, and the comparison output is supplied to VCO'31 as a control signal through low-pass P-wave device 30. The VCO 31 is slave-synchronized to the highly stable lock frequency of the clock supply device 29. As a result, the output clock 33 of the primary oscillator 27 of the earth station 26 becomes highly stable.

This highly stabilized clock 33 is branched into many branches, one of which is a phase-locked loop 38 consisting of a phase comparator 34, a low-frequency P wave generator 35, a voltage controlled oscillator 36, and a frequency divider 37.
It is converted into a highly stable frequency signal close to the radio frequency. The output signal of this phase-locked loop 38 is transmitted to a multiplier 39.
The signal is multiplied and supplied to the radio frequency device 13 as a radio frequency signal. Similarly, the other one of the many branched clocks 33 is generated by a phase-locked loop 45 composed of a phase comparator 41, a low-frequency P wave generator 42, a voltage controlled oscillator 43, and a frequency divider 44. converted into a frequency signal. The output of this phase-locked loop 45 is multiplied by a multiplier 46 and supplied to the modem 12 as an intermediate frequency signal. In addition, a relatively low frequency clock supplied to the baseband signal processing device 11 is transmitted from the tarokk 33 to the frequency divider 4.
7 or by directly dividing or multiplying the frequency by the multiplier 48.

As explained above, the radio frequency signals, intermediate frequency signals, baseband processing clock signals, etc. required by the earth station 26 can be generated from a single highly stable source oscillator 27 that is slave-synchronized to the clock frequency of the terrestrial network. Accordingly, highly stable radio frequency signals, intermediate frequency signals, and clock signals can be obtained. Digital clock supply device 29
For example, when using the output of a cesium oscillator of 8.19 MHz as an external highly stable clock, the frequency of the output clock 33 of the original oscillator 27 is 8.19 MHz, and the output of the phase-locked loop 38 is IGI ( It is considered to be a frequency near Z, and the radio frequency signal obtained from this is 30GH7
The output frequency of the phase-locked loop 45 is set to be around 70 MH2, and the intermediate frequency signal is around 140 MH2.
If the frequency of the baseband processing clock is set to be around H2 and the frequency of the baseband processing clock is several tens of KHz to 20 MH2, the circuit 39.46 can be omitted.

FIG. 3 shows an embodiment of the present invention on a satellite. In this embodiment, a high stability lock with a long-term stability of 1()11 is provided to the earth station 26 from the digital clock supply device 29 of the terrestrial digital network 28. The phase locked loop synchronizes the source oscillator 27 with a high stability lock from the terrestrial digital network 28. Furthermore, using a clock signal, an intermediate frequency signal, and a radio frequency signal generated based on the output clock 33 of the original oscillator 27,
The earth station 26 modulates the signal using the earth station device 49 and transmits the signal from the antenna 50 to the satellite 51. The satellite 51 transmits the signal sent from the earth station 26 to the antenna 52.
The clock signal 56 is received by the radio frequency device 53 and sent to the modem device 54 to reproduce the clock 56 from the received signal. The recovered clock 56 is supplied to the original oscillator 57 on the satellite 51, and the original oscillator 57 on the satellite is slave-synchronized to the recovered clock 56 by a phase-locked loop consisting of a phase comparator 58, a low-frequency P wave generator 59, and a voltage-controlled oscillator 61. let

With this configuration, the original oscillator 57 on the satellite
is slave-synchronized to the highly stable or locked frequency of the terrestrial network via the earth station 26, and the output clock 62 of the original oscillator 57 on the satellite becomes highly stable. The output 62 of the highly stabilized original oscillator 57 is branched into many branches, one of which is sent to a phase comparator 63, a low-frequency VP wave generator 64, and a voltage-controlled oscillator 6.
5 and a frequency divider 66 to generate a signal with a constant high and low frequency close to the radio frequency, and the output is increased in frequency by a multiplier 68 to create a radio frequency signal. 9. Connect this to the radio frequency device 53
supply to Similarly, the other one of the many branched clocks 62 is input to a phase-locked loop 74 composed of a phase comparator 69, a low-frequency F wave generator 71, a voltage-controlled oscillator 72, and a frequency divider 73, from which the intermediate frequency A signal with a highly stable frequency close to is generated, and the frequency of the signal is increased by a multiplier 75 to become an intermediate frequency signal, and this intermediate frequency signal is supplied to the modulation/demodulation device 54. A relatively low frequency clock supplied to the on-satellite signal processing device 76 connected to the modem device 54 is a clock 62 which is supplied to a multiplier 77 or a frequency divider 7.
8, etc., by multiplying or dividing the frequency.

As explained above, the source oscillator 57 on the satellite 51 is slave-synchronized via the earth station 26 to the highly stable or locked frequency of the ground network 28, and based on the single highly stable source oscillator 57, the necessary By creating a radio frequency signal, an intermediate frequency signal, and a pacebar/card processing clock signal,
It is possible to stabilize these frequencies. satellite 51
Also, the multipliers 68 and 75 may be omitted. Although the above explanation has been given by taking the satellite communication system as an example, the present invention can also be applied to other general wireless communication systems.

As explained above, by highly stabilizing radio frequency signals, intermediate frequency signals, baseband processing clock signals, etc. of earth stations and satellites, the requirements for modulation and demodulation equipment of earth stations and satellites are significantly reduced. The advantage is that it can be done. Further, by using a phase-locked loop, it is possible to easily obtain a radio frequency signal or an intermediate frequency signal having a relatively low frequency but a frequency higher than that of a highly stabilized clock 33.62.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a frequency generation system in a conventional satellite communication earth station, Figure 2 is a block diagram showing an embodiment in which this invention is applied to an earth station, and Figure 3 is a block diagram showing an embodiment in which this invention is applied to a satellite. FIG. 11.76: Baseband signal processing device, 12°54:
Modem/demodulator, 13, 53: Radio frequency device, 26: Earth station, 27: Original oscillator, 28: Terrestrial network, 29: Highly stable digital clock supply device for terrestrial network, 38, 45, 67
．． 74: Phase locked loop, 51: Satellite, 57: Satellite original oscillator. Patent applicant Taku Kusano, representative of Nippon Telegraph and Telephone Public Corporation

Claims (3)

[Claims] (1) A single highly stable source oscillator that is slave-synchronized to a highly stable lock frequency supplied from the outside, and a signal of a higher frequency that is phase-synchronized with the output of that source oscillator. a first phase-locked loop that obtains
means for supplying an intermediate frequency signal from the output of the phase-locked loop to a modulation/demodulation device; a second phase-locked loop to which the output of the original oscillator is supplied and obtains a higher frequency signal phase-locked therewith; means for providing a radio frequency signal from the output of the second phase-locked loop to a radio frequency device;
A frequency generation system for a wireless communication system, the frequency generation system being supplied with the output of the source oscillator, and comprising means for obtaining a plurality of baseband processed clock signals having at least one frequency divider and having different frequencies. (2) The wireless communication system according to claim 1, wherein the highly stable lock supplied from the outside is a clock existing in a terrestrial network, and the source oscillator is provided in a satellite communication earth station. frequency generation method. (3) A frequency generation method for a wireless communication system including means for slave-synchronizing a single source oscillator on a satellite with the source oscillator of the earth station to obtain a signal of a desired frequency for use on the satellite.