JPH11127476A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a local signal with high accuracy without providing an expensive local oscillator on a subscriber station side, to suppress the burden of the subscriber side and to improve reliability by synthesizing a subscriber station side local signal with a base station side local signal by using a phase- locked loop. SOLUTION: A base station 1 side produces a sending wave RF by superimposing a base station side internal local signal CLO and an intermediate frequency signal IF and also takes out the signal IF from the wave RF by using a subscriber station side local signal ALO a subscriber station 2 side. Non- modulation wave of a base station side local signal BLO (having the same frequency as the signal ALO) is simultaneously sent from the station 1 to the station 2 together with the wave RF in a prescribed band or its neighborhoods, and also the signal ALO is synchronized by the signal BLO and a phase-locked loop(PLL) 3. Furthermore, the signal BLO is sent together with the wave RF by using a synthesizer (COMB).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system, and more particularly, to a wireless communication system for providing a local television service or a high-speed data line to a plurality of subscribers using a high frequency band of several GHz or more. The present invention relates to a communication system.

[0002]

2. Description of the Related Art The demand for a high-speed network has been increasing with the rapid spread of the Internet connection and the like in recent years. However, high-speed lines provided by wired networks are still expensive for ordinary consumers, and local wireless communication networks capable of providing lower-cost services are being actively researched and developed. . This local wireless network uses quasi-millimeter waves (3 GHz to 30 GHz).
z), and also in the millimeter wave band (30 GHz to 300 GHz)
Utilizing such a high frequency band, it is used, for example, to provide a high-speed two-way data communication line from a telephone exchange to a plurality of subscribers located in a predetermined area or to provide a local television service. As shown in FIG. 8, in such a local wireless network (wireless communication system), a plurality of subscriber stations 50 installed in a general home or the like include a cell base station 52 having a radially communicable area (cell) 51. Connected via a wireless line. In a high band such as a quasi-millimeter wave band or a millimeter wave band, the line-of-sight distance is limited to about several kilometers, and the size of the cell 51 is also in accordance with it. When covering a relatively large area such as an urban area, the cell base station 5
A plurality 2 is provided for the region. Each cell base station 5
The two are connected via a high-speed line 54 such as an optical fiber to a central office 53 installed in a telephone exchange or the like, and a cell base station 52 and a central office 53 are connected to a subscriber station 50 in another cell 51. It is also possible to carry out communication via the Internet. Generally, a super heterodyne system is used for wireless communication between the cell base station 52 and the plurality of subscriber stations 50.
On the transmitting side of this system (for example, the cell base station 52), transmission is performed after a local oscillation signal (hereinafter, referred to as a local oscillation signal) is superimposed on an intermediate frequency signal. On the other hand, on the receiving side (for example, the subscriber station 50), an intermediate frequency signal is extracted from the signal input from the antenna using a local oscillation signal created in advance by the subscriber station. By converting the carrier frequency in this manner, handling such as amplification becomes easy.
The local oscillation signal is a signal of a predetermined frequency output from the oscillator, and is represented by a sum or a difference between the high frequency signal and the intermediate frequency signal. Here, FIG. 9 shows a conventional example of a front end unit (frequency conversion device) of a transmission / reception device provided in the subscriber station 50 or the cell base station 52.

[0003] As shown in FIG.
00 is the receiving antenna 601 and the receiving antenna 6
01, a low-noise amplifier 602 for amplifying only the necessary band of the signal input from the first input terminal 01, and an output from the low-noise amplifier 602 and a local oscillation signal LO to form a signal IF having an intermediate frequency.
, A band-pass filter 604 for selecting only a required band from the intermediate frequency signal IF output from the mixer 603, and an amplifier 605 for amplifying the output of the band-pass filter 604. An amplifier 607 for amplifying the intermediate-frequency signal IF for transmission; a transmission mixer 608 for mixing the output from the amplifier 607 and the local oscillation signal LO to output a transmission-frequency signal RF; The transmission unit 612 includes a band filter 609 that passes only a required band of the signal RF output from the transmission mixer 608, an amplifier 610 that amplifies the output of the band filter 609, and a transmission antenna 611.

The local oscillator signal LO input to the reception mixer 603 and the transmission mixer 608 is output from the local oscillator 613. The local oscillator 613 includes a crystal oscillator 614 for oscillating a reference frequency and the crystal oscillator 61.
Amplifier 615 for amplifying the output from the phase comparator 4 and the phase comparator 6
16, a loop filter 617, and a voltage-controlled oscillator 618 whose oscillation frequency can be finely adjusted according to the input voltage. Local oscillation signal L output from local oscillator 613
O is amplified by the reception amplifier 619 or the transmission amplifier 620, respectively, and then the reception mixer 603 is amplified.
Alternatively, it is input to the transmission mixer 608. For example, the transmission wave RF transmitted from the cell base station 52 to the subscriber station 50 is
As described above, the normal local oscillation signal LO (base station side local oscillation signal) and the intermediate frequency signal IF are superimposed (FIG. 1).
0). The band of the intermediate frequency signal IF is divided into a plurality of bands, and channels having different communication contents are allocated. This transmitted wave RF
Is the frequency converter 60 installed in the subscriber station 50.
0 is received by the receiving antenna 601. Transmission wave RF received by the receiving antenna 601
Is amplified only in the required band by the low noise amplifier 602. The output from the low-noise amplifier 602 is mixed with the local oscillation signal LO (subscriber station local oscillation signal) from the local oscillator 613 by the reception mixer 603, and a frequency-converted intermediate frequency signal IF is output. . The local station signal is set to have the same frequency as the base station signal. Since the crystal oscillator 614 provided in the local oscillator 613 is also used for transmission from the subscriber station 50, it has extremely high frequency accuracy (for example, about 1 ppm to 0.01 ppm) in a temperature-controlled thermostat. Low phase noise. The output from the crystal oscillator 614 is amplified to an appropriate amplitude by the amplifier 615 and supplied to the phase comparator 616. The output of the 1 / N frequency divider 621 is supplied to the phase comparator 616, and a voltage proportional to the phase difference between the output of the amplifier 615 and the output of the frequency divider 621 is output. This output voltage is input to the voltage controlled oscillator 618 after the DC voltage is amplified by the loop filter 617 and the high frequency component is appropriately attenuated. The voltage controlled oscillator 61
The output of the amplifier 619 and 6 is output as a local signal LO.
20 is output. At the same time, the voltage controlled oscillator 61
8 is output to a phase comparator 6 via a 1 / N frequency divider 621.
16 to form a feedback loop. This feedback loop is called a phase locked loop or a phase locked loop (PLL), and is used to obtain N times the frequency while maintaining high frequency accuracy and low phase noise at the same level as the reference frequency. The output of the voltage controlled oscillator 618 is supplied to the receiving mixer 603 via the amplifier 619. The intermediate frequency signal IF output from the receiving mixer 603 is selected only in a required band by the bandpass filter 604, is appropriately amplified by the amplifier 605, and is then transmitted to an indoor set-top box or the like.

[0005] On the other hand, in the transmitting section 612, the intermediate frequency signal IF appropriately amplified by the amplifier 607 and the local oscillation signal LO from the local oscillator 613 are supplied to the transmission mixer 608. The signal corresponding to the transmission frequency is selected by the bandpass filter 609 from the signal whose frequency has been converted by the transmission mixer 608, and
After being amplified to a sufficient level by 0, it is supplied to the transmitting antenna 611 and transmitted as a radio wave. For a two-way wireless communication system having the above-described frequency conversion device 600, in the case of one-way communication that does not require transmission from the subscriber station 50 to the cell base station 52, such as a local television service, for example, The configuration of the receiving device installed in the personal station 50 is simplified as compared with the receiving unit 606. Here, FIG. 11 shows a schematic configuration of a conventional receiving apparatus. As shown in FIG. 11, the receiving apparatus 800 is different from the transmitting apparatus 6 in that the configuration of the local oscillator 801 is simplified.
It has almost the same configuration as the transmitting / receiving device 600 except that there is no twelve. The local oscillator 801 uses a dielectric resonator or the like. The oscillation frequency is
02 is supplied to the receiving mixer 603 as it is.

[0006]

In the conventional frequency converter used for two-way wireless communication, a high-precision local oscillator 613 is provided not only on the cell base station 52 but also on the subscriber station 50 side. Is required. However, a crystal oscillator 614 in a thermostat, for example, used for the local oscillator 613 is generally expensive, consumes large power, and has a large component size. Further, the frequency divider 621 used in the microwave band, the quasi-millimeter wave band, or the millimeter wave band is also a component that is expensive and consumes a lot of power. Further, unnecessary radiation signals of various frequencies leak from the frequency divider 621 to a power supply line and the like, and it is necessary to prevent leakage of spurious signals using various filters, shield plates, and the like. Will also be extremely large. Therefore, when a highly accurate local oscillator is used, there is a problem that the cost of the subscriber station 50, that is, the general consumer increases. In addition, since there is no transmission from the subscriber station in one-way wireless communication such as a local television service, an expensive local oscillator such as a crystal oscillator in a thermostat is not required. However, when the conventional receiver 800 is used in the microwave, quasi-millimeter wave, or millimeter wave band, a problem occurs in frequency accuracy. Local oscillator 80 used in receiving apparatus 800
1 is usually installed outdoors, so it is exposed to a high temperature of 30 ° C. or higher in summer and to a low temperature of 0 ° C. or lower in winter. In this case, the temperature characteristic of the local oscillator 801 is 100 p.
A frequency error of about pm occurs. This frequency error is about 100 Hz for a medium wave of about 1 MHz, which is small and does not pose a problem as compared with, for example, a channel band of 9 kHz of an AM modulated wave. However, for example, in a microwave band of 12 GHz or a quasi-millimeter wave band of 30 GHz, the frequency errors are 1.2 MHz and 3 MHz, respectively. Further, the frequency band of the phase noise is as large as about 3 ppm,
In the case of 2 GHz, the phase noise of 36 kHz is included in the output of the local oscillator. That is, as the frequency used for communication increases, the degree to which the frequency accuracy and phase noise of the local oscillator 801 affect the frequency change of the radio wave also increases, and it is necessary to secure a wide channel band accordingly. This problem is important not only in one-way communication but also in two-way communication.
When a frequency band of 500 MHz is allocated to about 0 subscribers, the frequency bandwidth of one modulated wave channel is limited to about 5 MHz to 500 kHz, but the frequency accuracy of the local oscillator is poor. If the frequency error is as high as 3 MHz as described above, signals of the two channels interfere with each other and reliable communication cannot be performed. An object of the present invention is to provide a highly reliable wireless communication system while improving the wireless communication system and suppressing the load on the receiving side in order to solve the problems in the conventional technology. .

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method of connecting a base station and a plurality of subscriber stations, and transmitting a microwave, quasi-millimeter wave, or transmission wave of a predetermined band in the millimeter wave band. Is transmitted from the base station to each subscriber station, wherein the base station side superimposes a base station side local oscillation signal and an intermediate frequency signal to generate the transmission wave, In a wireless communication system in which the station side extracts the intermediate frequency signal from the transmission wave using the subscriber station side signal, the station signal corresponding to the base station side signal and in the predetermined band or in the vicinity is the same as the base station side signal. The signal transmitted from the base station to the subscriber station, and the signal originating from the subscriber station is synchronized with the signal originating from the base station extracted from the corresponding station signal by a phase locked loop. As a wireless communication system It has been. In the above wireless communication system, the local station signal from the subscriber station is synchronized with the base station local signal using a phase-locked loop, so that the same high frequency accuracy and low phase accuracy as the base station local signal can be obtained. Noise can be obtained. In other words, there is no need to provide a high-precision local oscillator at the subscriber station, and the cost and installation space at the subscriber station can be greatly reduced. In the wireless communication system, the transmission wave transmitted from the subscriber station to the base station includes a subscriber station side signal synchronized with the base station side signal extracted from the corresponding station signal. If a signal obtained by superimposing a signal and an intermediate frequency signal is used, a reliable two-way wireless communication system can be provided while suppressing the cost on the subscriber side.

In addition, a sample reference frequency corresponding to a modulation clock of a digital modulator provided on the base station side is transmitted from the base station to the subscriber station, and a digital demodulation provided on the subscriber station side is provided. If the demodulation clock of the receiver is determined based on the sample reference frequency received by the subscriber station, a circuit for reproducing the symbol clock on the receiving side is not required, so that the configuration can be simplified and the cost can be reduced. Further, the error rate of demodulation due to the phase error of the symbol clock (demodulation clock) and noise can be reduced, and the reliability of communication can be improved. further,
The digital modulator and the demodulator provided on the base station side are driven by the same clock, and the modulation clock of the digital modulator provided on the subscriber station side is adjusted to the sample reference frequency received by the subscriber station. If determined based on this, since the frequency of the entire communication system is synchronized with the local oscillator, modulator, and demodulator on the base station side, interference between signals can be reduced, and frequency design can be made easier. . In the wireless communication system, the signal from the corresponding local station is transmitted to the subscriber station simultaneously with the transmission wave, for example. The base station may continuously transmit to the subscriber station, or the base station may intermittently transmit to the subscriber station. As the equivalent local signal, for example, an unmodulated wave of the base station side local signal or a narrow band modulated wave may be used. Further, if a modulated wave in the audible frequency band is used for the above-mentioned local oscillation signal, the antenna can be adjusted so that the sound quality of the signal can be improved while listening to the ear, and the handling can be facilitated. Also, by including information on the transmitting side in this modulated wave,
For example, it is possible to broadcast the name of a broadcasting station. Also, a signal obtained by multiplying the signal of the oscillator provided in the phase locked loop is used as the signal from the subscriber station, or a harmonic for the transmission and / or reception mixer provided in the subscriber station is used. If a mixer is used, it becomes possible for the subscriber station side to make the local oscillation signal for transmission and the local oscillation signal for reception have different frequencies, so that the transmission frequency band and the reception frequency band are far apart. Can handle cases.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiment is a specific example of the present invention and does not limit the technical scope of the present invention. FIG. 1 is a diagram showing a schematic configuration of a radio communication system according to an embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of a frequency conversion device on a subscriber station side used in the radio communication system. 3 is a frequency chart of a transmission wave of the wireless communication system. As shown in FIG. 1, a wireless communication system according to an embodiment of the present invention connects a base station 1 and a plurality of subscriber stations 2 to each other, and transmits a predetermined band in a microwave, quasi-millimeter wave, or millimeter wave band. Is a wireless communication system that transmits the transmission wave RF from the base station 1 to each subscriber station 2. The base station 1 superimposes the base station-side internal station signal CLO and the intermediate frequency signal IF to generate the transmission wave RF, and the subscriber station 2 side generates the subscriber station side station signal ALO. Is similar to the conventional wireless communication system in that the intermediate frequency signal IF is extracted from the transmission wave RF using the above. Note that the normal base station side internal station signal CLO and the subscriber station side station signal AL
O uses different frequencies that are close to each other, but may be the same frequency. However, in the wireless communication system according to the present embodiment, the unmodulated wave of the base station-side station-originated signal BLO (having the same frequency as the subscriber station-side station-originated signal ALO) in or near the above-mentioned predetermined band. From the above subscriber station 2
In which the signal ALO transmitted from the subscriber station is synchronized with the received signal BLO transmitted from the subscriber station by a phase-locked loop (PLL) 3. And different. In addition, the base station side station signal BL
O is transmitted together with the transmission wave RF using a combiner (COMB) as shown in FIG.

[0010] As shown in FIG. 2, the frequency conversion device 200 on the subscriber station side used in the radio communication system according to the present embodiment includes a receiving antenna 201 and an input signal from the receiving antenna 201. A low-noise amplifier 202 for amplifying only a necessary band of a signal;
02 and local signal (subscriber station side local signal) AL
O and an intermediate frequency signal (intermediate frequency signal) I
F, a reception mixer 203 having a reception mixer 203, a bandpass filter 204 for selecting an intermediate frequency IF signal output from the reception mixer 203, and an amplifier 205 for amplifying the output of the bandpass filter 204.
And an amplifier 2 for amplifying an intermediate frequency IF signal for transmission
07, an output from the amplifier 207 and the local oscillation signal ALO, and a transmission mixer 208 for outputting a signal of a transmission frequency, and a band for passing only a necessary band of the signal output from the transmission mixer 208. It is the same as the conventional one in that it comprises a filter 209, an amplifier 210 for amplifying the output of the bandpass filter 209, and a transmitting unit 212 having a transmitting antenna 211. The point that the above-mentioned subscriber station side frequency converter 200 is different from the conventional one is that the local oscillator 300 comprises a phase locked loop 3 including a low frequency pass filter 301, a loop filter 302 and a voltage controlled oscillator 303. And the voltage-controlled oscillator 303
Is synchronized with the base station side signal BLO input from the receiving antenna 201 to generate the subscriber station side signal ALO.

Hereinafter, the frequency converter 2 on the subscriber station side will be described.
00 will be described in detail. Base station side station signal BL transmitted together with transmission wave RF transmitted from base station 1
O (refer to the frequency chart in FIG. 3) is received by the receiving antenna 201 of the subscriber station similarly to the transmission wave RF. The signal from the receiving antenna 201 is amplified by the low noise amplifier 202 and then supplied to the receiving mixer 203 to output the voltage controlled oscillator 203 (subscriber station side signal ALO).
And a voltage corresponding to the phase difference between the base station side local oscillator signal BLO and the output of the voltage controlled oscillator 303 is output.
The output of the receiving mixer 203 is supplied to the band pass filter 204 and the low frequency pass filter 301.
The signal from which the high frequency has been removed by the low frequency pass filter 301 is appropriately amplified in the DC component by the loop filter 302 and input to the voltage controlled oscillator 303. In the voltage controlled oscillator 303, the output is finely adjusted according to the input voltage. That is, when the phase of the output of the voltage controlled oscillator 303 lags behind the base station side signal BLO, a voltage corresponding to the phase difference is input to the voltage controlled oscillator 303 and the phase is controlled to advance. . Conversely, when the phase is advanced, the phase is controlled to be delayed, and the phase locked loop 3 is configured so that the oscillation frequency of the voltage controlled oscillator 303 is synchronized with the base station side signal BLO. The signal ALO from the subscriber station is synchronized with the signal BLO from the base station by the phase locked loop 3. On the other hand, only the necessary band of the other output of the receiving mixer 203 is selected by the band-pass filter 204, and is appropriately amplified by the amplifier 205, and then output as an intermediate frequency signal IF to an indoor set-top box or the like. The output of the voltage controlled oscillator 303 can also be used as a transmission local oscillation signal ALO for transmitting radio waves from the subscriber station 2 to the base station 1. That is, the transmission IF signal IF is amplified by the amplifier 207, mixed with the output of the voltage controlled oscillator 303 by the transmission mixer 208, and supplied to the bandpass filter 209 as a transmission frequency band signal. The signal in which only the required band is selected by the bandpass filter 209 is appropriately amplified by the amplifier 210 and then transmitted to the base station 1 by the transmission antenna 211. As described above, by using the phase locked loop 3 to synchronize the subscriber station side signal ALO with the received base station side signal BLO, an accurate crystal in a thermostatic chamber is provided on the subscriber station side. A high-precision local signal of about 0.1 ppm can be obtained without having to provide an oscillator. Further, in the above wireless communication system, even if the frequency of the local oscillator on the transmitting (base station) side is slightly shifted, the frequency of the local oscillator on the receiving side (subscriber station) side is also shifted by the same amount. In this case, the frequency shift is canceled, and the accuracy obtained at the intermediate frequency is further increased. If a frequency error of about 0.1 ppm is secured, for example, even in the communication of the 12 GHz band, the frequency error will be within about 1.2 kHz, and
Reliable communication is possible even when the channel frequency bandwidth is limited to about 0 kHz.

Further, the phase noise is reduced at the same time as the frequency accuracy is improved. For example, phase noise is suppressed to about 0.01 ppM. For this reason, QPSK (Quadrature Phase S
hiftKeying) as well as 256QAM (Quadrtutu
Communication using digital modulation methods such as reamplitude modulation) is also possible. For example, in the case of the above 200 kHz channel band, 256 kbps, 16 QA by QPSK modulation
512 kbps for M modulation, 768 kb for 64 QAM modulation
High-speed digital communication of 1024 kbps becomes possible by ps, 256QAM modulation. If the channel band is narrowed down to about 50 kHz while maintaining the speed of 64 kbps by QPSK modulation, 1 band is obtained even in the 500 MHz band.
As many as 0000 channels can be provided. Therefore, a high-speed two-way communication system in which channels are allocated to a large number of subscribers can be constructed while minimizing the burden on the subscribers. Also, the channel frequency band is
When the frequency is reduced from 20 MHz to 200 kHz, the received power per frequency is increased by a factor of 100 even with the same received power, so that the signal-to-noise ratio is improved by about 20 dB. Conversely, if the same signal-to-noise ratio should be satisfied, a received power of 1/100 is sufficient, and a low-cost, small-size receiving antenna and an inexpensive receiving amplifier with a large noise figure are used. Therefore, the size of the receiver can be further reduced, and the cost can be reduced.

[0013]

[Embodiment] In the above embodiment, the base station side station signal BL
The case where the unmodulated wave of O is transmitted from the base station 1 to the subscriber station has been described, but the base station-side station-originated signal BLO is modulated and transmitted in a narrow band that does not interfere with other transmission waves RL. You may make it. If the modulation is performed at a frequency sufficiently higher than the frequency band of the loop filter 302, the operation of the phase locked loop 3 will not be affected. For example, 1k
If a narrow-band FM modulated wave modulated at a modulation frequency of about 1 Hz to 1 MHz is used, a demodulated signal appears at the output of the low frequency pass filter 301, and a demodulated output can be obtained as it is. At the output of 302, the modulation signal is sufficiently attenuated, so that the phase locked loop 3 is not adversely affected. Also, when a modulated wave in the audible frequency band is used, it is possible to adjust the direction of the antenna 201 or the like to improve the sound quality of the signal while listening to the demodulated signal with the ear, It is also possible to broadcast the name of (base station) and the like. Further, in the above embodiment, only the base station-side station-originated signal BLO is transmitted at the same time as the transmission wave RF. A frequency or a modulation clock may be transmitted.
The equivalent local oscillation signal includes an unmodulated wave of the base station side local oscillation signal RF,
The signal includes the base station-side station-originated signal RL itself such as a modulated wave, a signal having a certain relationship, and a reference frequency and a modulation clock transmitted together therewith. FIG. 4 shows a frequency chart of an example in which the symbol clocks Fs1 and Fs2 used in the modulator and the demodulator are transmitted in addition to the base station side signal BLO. By transmitting the symbol clock from the base station in this way, the symbol clock recovery circuit provided on the receiving side can be omitted, not only reducing the cost, but also reducing the phase error and the phase error of the symbol clock recovery circuit. The demodulation error rate due to phase noise can be reduced, and communication reliability can be improved. Also, by synchronizing all the reference frequencies of the local oscillator, modulator, and demodulator between the base station and the subscriber station, interference between the signals can be reduced, and the design of the frequency relationship can be simplified. Become. Such a wireless communication system is also an example of the wireless communication system in the present invention.

In the above embodiment, both the base station 1 and the subscriber station 2 can perform transmission and reception.
If there is no need to transmit to the frequency converter 2,
The configuration can be further simplified by removing the transmission unit 212 from 00. Further, in the above embodiment, the base station-side station-originated signal BLO is transmitted (at the same time) as the transmission wave RF. However, the base station-side station-originating signal BLO may be transmitted continuously or intermittently. May be transmitted. Such a wireless communication system is also an example of the wireless communication system in the present invention. Further, in the above embodiment, the voltage controlled oscillator 303 is used as the oscillator provided in the phase locked loop 3, but the present invention is not limited to this, and a current controlled oscillator such as YIG may be used. Further, in the above embodiment, the reception mixer 203 and the transmission mixer 208 are also used as the mixer of the phase locked loop 3, but a separate mixer may be provided. Such a wireless communication system is also an example of the wireless communication system in the present invention.

In the above embodiment, the same local station signal ALO is used for transmission and reception. However, as in the case of LMDS implemented in the United States, the transmission frequency band and the reception frequency band are used. When the distance between the local oscillator and the local oscillator for transmission is greatly different, it is necessary to make the frequencies of the local oscillator for transmission and the local oscillator for reception different from each other. An embodiment for realizing this will be described with reference to FIGS. The subscriber station-side frequency converter 200 'shown in FIG. 5 uses a voltage-controlled oscillator 303' which transmits at a frequency of 1 / N1 of the frequency of the receiving-side local oscillator 300 and uses the voltage-controlled oscillator 303 '. 303 ′ and the receiving mixer 203,
And the voltage-controlled oscillator 303 'and the transmission mixer 20
8 and × N1 and × N2 frequency multipliers 30 respectively.
7, 308 are provided. That is, the voltage controlled oscillator 3
03 'is 1 / N1 of the received base station side station signal BLO.
= Synchronize with the frequency of LO (com). By using a signal obtained by multiplying this signal by N2 by the frequency multiplier 308 as the transmission-side subscriber station signal ALO, the transmission frequency and the reception frequency can be made different, and the transmission frequency can be made different. It is possible to easily cope with the case where the band and the reception frequency band are far apart. For example, in the case of LMDS in the United States, the frequency band for reception of the subscriber station is 27.5 to 28.35 GHz, but the frequency band for transmission of the subscriber station is 31.0 to 31.3 GHz, which is approximately 3 GHz.
Hz higher frequencies are allowed. In such a case,
The frequency of the voltage controlled oscillator 303 'is set to, for example, 4.4 GHz.
z, N1 = 6, N2 = 7, then BLO = LO (RX) = N1 × LO (com) = 6 ×
4.4 = 26.4 GHz IF (RX) = 1.10-1.95 GHz LO (TX) = N2 × LO (com) = 7 × 4.4 = 3
0.8 GHz IF (TX) = 0.20-0.50 GHz, so that the intermediate frequency signal IF can be set to a frequency that is very easy to use.

The frequency converter 200 "on the subscriber station side shown in FIG. 6 uses harmonic mixers 203 'and 20' instead of using the frequency multipliers 307 and 308.
The same effect as in the above embodiment (FIG. 5) is intended to be obtained by utilizing 8 '. Harmonic mixer 20
Reference numerals 3 'and 208' internally generate a harmonic signal of an integral multiple (× N1, × N2) of the frequency of the local oscillator 300, and mix the harmonic signal with another signal to form a high-frequency local oscillator. This is a mixer that can achieve the same effect as using a mixer. FIG. 7 shows an example of the frequency chart. In this example, the fundamental frequency LO (com) is set to 4. GH
z, and the BLO on the downlink side is 6 of LO (com).
26.4 GHz, which is twice as high, and BLO on the uplink side
Is set to 30.8 GHz, which is seven times the LO (com). FIG. 7A shows the relationship between the frequencies on the downlink side. 26.4 GH is transmitted as BLO from the base station.
z. The signal of the above-mentioned fundamental frequency LO (com) is output from the voltage controlled oscillator 303 '. In the receiving harmonic mixer 203 ', the LO (co
m) is multiplied by 6 and mixed with the output of the low noise amplifier 202. The output of the harmonic mixer 208 'for transmission is
Due to the characteristics of the harmonic mixer, as shown in FIG. 7B, a signal appears every integer multiple of the fundamental frequency LO (com).
RF in frequency band slightly higher than 0.8 GHz BLO
Pass only signals. Although a similar output signal is generated in the harmonic mixer 203 'on the receiving side, unnecessary signals are removed by the next bandpass filter 204 and low-frequency pass filter 301. As described above, according to the embodiments shown in FIGS. 5 and 6, the transmission frequency and the reception frequency can be made different, and the transmission frequency band and the reception frequency band are greatly separated from each other. Can be easily handled.

[0017]

According to the invention described in any one of the first to twelfth aspects, the signal originating from the subscriber station is synchronized with the signal originating from the base station using a phase locked loop. A highly accurate local oscillator signal can be obtained without providing an expensive local oscillator on the subscriber station side, and a reliable wireless communication system with a reduced burden on the subscriber side can be provided. Further, according to the present invention, the transmission frequency and the reception frequency can be made different from each other, and when the transmission frequency band and the reception frequency band are greatly separated from each other. Can be easily handled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a wireless communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a frequency conversion device used in the wireless communication system.

FIG. 3 is a frequency chart of a transmission wave used in the wireless communication system.

FIG. 4 is a frequency chart of a transmission wave used in the wireless communication system according to one embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a frequency conversion device 200 ′ used in a wireless communication system according to one embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of a frequency conversion device 200 ″ used in a wireless communication system according to an embodiment of the present invention.

FIG. 7 is a frequency chart when a harmonic mixer is used (the frequency conversion device 200 ″).

FIG. 8 is a diagram illustrating a local wireless communication network.

FIG. 9 is a diagram showing an example of a frequency conversion device used in a conventional wireless communication system.

FIG. 10 is a frequency chart of a transmission wave used in a conventional wireless communication system.

FIG. 11 is a diagram showing another example of a frequency conversion device used in a conventional wireless communication system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base station 2 ... Subscriber station 3 ... Phase locked loop IF ... Intermediate frequency signal BLO ... Base station side station origination signal CLO ... Base station side internal station origination signal ALO ... Subscriber station side station origination signal RF ... Transmission wave

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichiro Goto 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel, Ltd. Kobe Research Institute

Claims (12)

[Claims] A wireless communication system for connecting a base station to a plurality of subscriber stations and transmitting a microwave, quasi-millimeter wave, or millimeter wave band transmission wave from the base station to each subscriber station. Wherein the base station superimposes the base station side signal and the intermediate frequency signal to generate the transmission wave, and the subscriber station side uses the subscriber station side signal to generate the transmission wave. In a wireless communication system for extracting the intermediate frequency signal from a wave, a signal transmitted from the base station and transmitted from the base station is transmitted from the base station to the subscriber station. A wireless communication system wherein a local station signal is synchronized with a base station signal extracted from the equivalent station signal by a phase locked loop. 2. A transmission signal transmitted from the subscriber station to the base station, wherein the transmission wave transmitted from the subscriber station to the base station is synchronized with the signal transmitted from the base station extracted from the corresponding station signal. The wireless communication system according to claim 1, wherein the signal and the signal are superimposed. 3. A sample reference frequency corresponding to a modulation clock of a digital modulator provided at the base station is transmitted from the base station to the subscriber station, and a digital reference signal provided at the subscriber station is provided. 3. The wireless communication system according to claim 1, wherein a demodulation clock of the demodulator is determined based on a sample reference frequency received by the subscriber station. 4. A digital modulator and a demodulator provided in the base station are driven by the same clock, and a modulated clock of the digital modulator provided in the subscriber station is received by the subscriber station. The wireless communication system according to claim 3, wherein the wireless communication system is determined based on the sampled reference frequency. 5. The wireless communication system according to claim 1, wherein said equivalent local signal is transmitted to said subscriber station simultaneously with said transmission wave. 6. The wireless communication system according to claim 1, wherein said equivalent station-originated signal is continuously transmitted from said base station to said subscriber station. 7. The wireless communication system according to claim 1, wherein said equivalent station signal is intermittently transmitted from said base station to said subscriber station. 8. The wireless communication system according to claim 1, wherein the equivalent local signal is an unmodulated wave of the base station side local signal. 9. The wireless communication system according to claim 1, wherein the equivalent local oscillation signal is a narrow-band modulated wave of the base station side local oscillation signal. 10. The wireless communication system according to claim 9, wherein said local equivalent signal is a modulated wave in an audible frequency band. 11. The radio communication system according to claim 1, wherein said subscriber station signal is a signal obtained by multiplying a signal of an oscillator provided in said phase locked loop. 12. The wireless communication system according to claim 1, wherein a harmonic mixer is used as a transmission and / or reception mixer provided on the subscriber station side.