JPH0580848B2 - - Google Patents

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> FIG. 1 shows the configuration of an original oscillator in a conventional satellite communication earth station. Baseband signal processing device 1
1. A modulation/demodulation device 12 and a radio frequency device 13 are connected in series, and an original oscillator 14 and a modulation/demodulation device 12 are used to generate a clock necessary for the baseband signal processing device 11 in order to generate frequency signals necessary for these devices. A source oscillator 15 for obtaining an intermediate frequency signal necessary for the radio frequency device 13 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 converted by the phase locked loop 17 into a signal of m times the frequency. The phase-locked loop 17 is a voltage controlled oscillator (hereinafter referred to as
The output of VCO) 18 is divided by a frequency divider 19,
The phase of the divided output and the output of the original oscillator 14 is compared with the phase comparator 20, and the phase comparison output is supplied as a frequency control signal to the VCO 18 through the reduced pass wave generator 21, and the output frequency of the original oscillator 14 is
A doubled and phase-synchronized output is obtained from the VCO 18. Output of phase-locked loop 17, that is, VCO
The output of 18 is divided by n, . . . n' by frequency dividers 22, . Further, the original oscillators 15 and 16 are frequency multipliers 24 and 2, respectively.
5, the signal is converted into an intermediate frequency signal and a radio frequency signal of required frequencies, respectively, and supplied to a modulation/demodulation device 12 and a radio frequency device 13, respectively.

In this way, in the conventional wireless communication system, the original oscillator 14 for generating a clock to be supplied to the baseband signal processing device 11, and the modulation/demodulation device 1 are used.
A primary oscillator 15 for generating an intermediate frequency signal to be supplied to the clock frequency device 2 and a primary oscillator 16 for generating a radio frequency signal to be supplied to the radio frequency device 13 operate independently, and the clock frequency,
The stability of the intermediate and radio frequencies depended on the stability of the respective original oscillators 14, 15, 16. In addition, the stability of the original oscillator 16, which is used to generate high frequencies such as radio frequencies, cannot be very high due to problems with the elements, etc.
The drawback was that the stability of the original oscillator for high frequencies was low. 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. For this reason, there was also the drawback that the requirements for the modulation/demodulation device 12 became stricter.

The above is about a satellite communication earth station, but a satellite station also has 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 operated independently, and had 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 synchronizes the primary oscillator of the earth station to the highly stable clock frequency of the terrestrial network with a stability of 10 ^-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 a highly stable clock frequency.
A configuration in which a plurality of required radio frequency signals, intermediate frequency signals, and clock signals are generated using a single highly stable source oscillator slave-synchronized to a highly stable external clock frequency as a common source oscillator on the earth station and the satellite, respectively. That is.

<Embodiment> FIG. 2 shows an embodiment in which the present invention is applied to an earth station, and parts corresponding to those in FIG. 1 are given the same reference numerals. The earth station 26 is provided with a source oscillator 27 which is slave-synchronized to an external clock frequency. For example, a highly stable digital clock supply device 29 installed in the terrestrial network 28 (for example,
(8.19 MHz cesium oscillator is used) is supplied to the original oscillator 27, and the original oscillator 27 is synchronized with this. The original oscillator 27 is a phase-locked loop,
The output of the VCO 31 and the clock signal of the clock supply device 29 are phase-compared by a phase comparator 32, and the comparison output is passed through a low-pass waver 30 to the VCO
31 as a control signal. VCO 31 is synchronized to the highly stable clock frequency of clock supply 29. This makes the output clock 33 of the primary oscillator 27 of the earth station 26 highly stable.

This highly stabilized clock 33 is branched into many branches, one of which is a phase comparator 34 and a low frequency filter 34.
5. The signal is converted into a highly stable frequency signal close to a radio frequency by a phase-locked loop 38 composed of a voltage controlled oscillator 36 and a frequency divider 37. The output signal of this phase-locked loop 38 is multiplied by a multiplier 39 and sent to the radio frequency device 13 as a radio frequency signal.
supplied to Similarly, the clock 33 has many branches.
The other one is a phase comparator 41, a low frequency filter 42,
A phase locked loop 45 composed of a voltage controlled oscillator 43 and a frequency divider 44 converts the signal into a highly stable frequency signal close to the intermediate frequency. 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. Also, a relatively low frequency clock supplied to the baseband signal processing device 11 is passed through a clock 33 to a frequency divider 4.
7 or by directly dividing or multiplying the frequency by a multiplier 48.

As explained above, the radio frequency signals, intermediate frequency signals, baseband processing clock signals, etc. required by the earth station 26 are generated from a single highly stable source oscillator 27 that is slave-synchronized to the clock frequency of the terrestrial network. As a result, highly stable radio frequency signals, intermediate frequency signals, and clock signals can be obtained. For example, when the output of the 8.19MHz cesium oscillator in the digital clock supply device 29 is used as an external highly stable clock, the frequency of the output clock 33 of the original oscillator 27 is 8.19MHz, and the output of the phase-locked loop 38 is The frequency is said to be around 1GHz, and the radio frequency signal obtained from this is 30G.
The frequency is around Hz, the output frequency of the phase locked loop 45 is around 70MHz, and the intermediate frequency signal is around 70MHz.
It is said to be around 140MHz, and the frequency of the baseband processing clock is said to be several tens of kilohertz to 20MHz. Direct radio frequency signals and intermediate frequency signals are obtained from each output of the phase-locked loops 38 and 45 and multiplied by 2.
The containers 39 and 46 can also be omitted.

FIG. 3 shows an embodiment of the present invention on a satellite, in which long-term stability is
A highly stable clock of 10 ^-11 is supplied to the primary oscillation period 27 of the earth station 26, and the primary oscillator 27 is slave-synchronized with the highly stable clock from the terrestrial digital network 28 through its phase-locked loop. Furthermore, the original oscillator 2
Using the clock signal, intermediate frequency signal, and radio frequency signal generated based on the output clock 33 of 7, the earth station 26 modulates the signal with the earth station device 49 and transmits the signal from the antenna 50 to the satellite 51. Send out. In the satellite 51, a signal transmitted from the earth station 26 is received by an antenna 52, and a clock 56 is regenerated from the received signal by a modulation/demodulation device 54 via a radio frequency device 53. The regenerated 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 regenerated clock 56 by a phase locked loop composed of a phase comparator 58, a low frequency generator 59, and a voltage controlled oscillator 61. . With such a configuration, the primary oscillator 57 on the satellite is slave-synchronized to the highly stable clock frequency of the terrestrial network via the earth station 26, and the output clock 62 of the primary 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 connected to a phase comparator 63, a low frequency generator 64, and a voltage controlled oscillator 6.
5 and a phase-locked loop 6 composed of a frequency divider 66
7 to generate a signal with a highly stable frequency close to the radio frequency, and the output is sent to a multiplier 68.
The frequency is increased to create a radio frequency signal, which is supplied to the radio frequency device 53. Similarly, the other one of the many branched clocks 62 is the phase comparator 6.
9. It is input to a phase-locked loop 74 composed of a low-frequency wave generator 71, a voltage-controlled oscillator 72, and a frequency divider 73, which generates a signal with a highly stable frequency close to the intermediate frequency, and the signal is sent to a multiplier. 75 increases the frequency to produce an intermediate frequency signal, and this intermediate frequency signal is supplied to the modulation/demodulation device 54. Satellite signal processing device 76 connected to modem 54
A relatively low frequency clock supplied to the clock 62 is generated by multiplying or dividing the frequency of the clock 62 using a multiplier 77 or a frequency divider 78.

As explained above, the primary oscillator 57 on the satellite 51 is synchronized via the earth station 26 to the highly stable clock frequency of the terrestrial network 28, and based on the single highly stable primary oscillator 57, the necessary These frequencies can be stabilized by creating radio frequency signals, intermediate frequency signals, and baseband processing clock signals. The multipliers 68 and 75 may also be omitted in the satellite 51. Although the above description has been made using a 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. from earth stations and satellites,
An advantage is that the requirements for modem equipment such as earth stations and satellites can be significantly reduced. 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 higher than that of the highly stabilized clocks 33 and 62.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a frequency generation system in a conventional satellite communication earth station, Fig. 2 is a block diagram showing an embodiment in which the present invention is applied to an earth station, and Fig. 3 is a block diagram showing the application of this invention to a satellite. FIG. 11, 76: Baseband signal processing device, 1
2, 54: Modulation and demodulation device, 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.

Claims (1)

[Claims] 1. A baseband signal processing device that processes a baseband signal using at least one or more clock signals, a modulation/demodulation device that modulates and demodulates the baseband signal and an intermediate frequency signal, and a In a wireless communication system that uses a wireless communication device that is cascaded with a radio frequency device that performs conversion processing to a frequency signal, a single highly stable clock frequency that is subordinately synchronized to a highly stable clock frequency supplied from an external source means for supplying the intermediate frequency signal to the modulation/demodulation device; and a first phase-locked loop to which the output of the primary oscillator is supplied and which obtains a signal of a higher frequency that is phase-locked with the primary oscillator; , a second phase-locked loop to which the output of the source oscillator is supplied and which obtains a higher frequency signal phase-locked therewith, and means for supplying the radio frequency signal to the radio frequency device; A frequency generation system for a wireless communication system, comprising means to which an output of an oscillator is supplied, and means for generating at least one or more clock signals having at least one period division and different frequencies and supplying the generated clock signals to the baseband signal processing device. 2. The highly stable clock supplied from the outside is a clock existing in a terrestrial network, and the source oscillator is provided in a satellite communication earth station. How it occurs. 3. Frequency generation for the wireless communication system according to claim 2, including means for slave-synchronizing a single source oscillator on the satellite with the source oscillator of the earth station to obtain a signal of a desired frequency for use on the satellite. method.