CA2195039A1 - Frequency stabilized communication system - Google Patents
Frequency stabilized communication systemInfo
- Publication number
- CA2195039A1 CA2195039A1 CA002195039A CA2195039A CA2195039A1 CA 2195039 A1 CA2195039 A1 CA 2195039A1 CA 002195039 A CA002195039 A CA 002195039A CA 2195039 A CA2195039 A CA 2195039A CA 2195039 A1 CA2195039 A1 CA 2195039A1
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- signal
- carrier
- station
- receiver
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
- H04B1/40—Circuits
- H04B1/403—Circuits using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
Abstract
A frequency stabilized communication system comprising Doppler -shift detective and corrective unit and dual-carrier radio receiver is employed to decrease a Doppler frequency-shift effect due to relative movement between mobile station and base one, drifts of local oscillation signals of receivers and transmitters. The dual-carrier receiver completes the frequency selection and frequency conversion with utilizing mixture of local oscillation signal of receiver and dual-carrier signal itself so that effect to frequency-drift is reduced, and power consumption of local oscillation generator is controlled. Due to applying the Doppler-shift detective and corrective unit, the frequency of reception and transmission of mobile station will be remotely real-time controlled by base station or be by mobile one itself directly as the movement state of that changes, which avoid the adjacent channel interference from the transmission of mobile station against the receiver of base one and balance from the receiver of mobile one against signal.
Description
SPECIFICATION
The present invention relates to frequency stabilization for radio communication sy~tem. In particular,it relates to mobile communication system for decreasing Doppler effect caused by relative motion between transceivers and for decreasing ~he influence from frequency-shift of the local oscillation signal of the transceivers.
Early radio communication has mainly consisted of fixed point to point communication. Mobile communications are being used increasingly. This creates a number of problems.First,there is Doppler frequency-drift in the signal received by both of the fixed and mobile stations that will make the received signal frequencies exceed channel bandwidth range so as to fall into adjacent channels to generate substantial interferences when the transceivers are in relative motions. This either causes the receivers detune into the received signal frequencies or place the received signal into the adjacent channels of the receivers.Second, previously known super heterodyne receivers have been mainly used in fixed-point reception mode and their operating frequencies have been low enough for the receiver's performances to be satisfactory.But this situation has changed significantly with the appearance of mobile communication and much higher operating frequencies. A signal frequency-shift is difficult to control because:
l.The stability of the local oscillation generators of the transceivers are limited. The higher the frequency,the greater is the drift.The local oscillation frequency of the receiver increases with higher its receiving signal frequency, which is not necessary to signal selection but is necessary to signal frequency conversion; so, the stability of the intermediate signal frequency, which depends upon the balance between the local oscillation stability of two communicating transceivers, become worse and worse.
The present invention relates to frequency stabilization for radio communication sy~tem. In particular,it relates to mobile communication system for decreasing Doppler effect caused by relative motion between transceivers and for decreasing ~he influence from frequency-shift of the local oscillation signal of the transceivers.
Early radio communication has mainly consisted of fixed point to point communication. Mobile communications are being used increasingly. This creates a number of problems.First,there is Doppler frequency-drift in the signal received by both of the fixed and mobile stations that will make the received signal frequencies exceed channel bandwidth range so as to fall into adjacent channels to generate substantial interferences when the transceivers are in relative motions. This either causes the receivers detune into the received signal frequencies or place the received signal into the adjacent channels of the receivers.Second, previously known super heterodyne receivers have been mainly used in fixed-point reception mode and their operating frequencies have been low enough for the receiver's performances to be satisfactory.But this situation has changed significantly with the appearance of mobile communication and much higher operating frequencies. A signal frequency-shift is difficult to control because:
l.The stability of the local oscillation generators of the transceivers are limited. The higher the frequency,the greater is the drift.The local oscillation frequency of the receiver increases with higher its receiving signal frequency, which is not necessary to signal selection but is necessary to signal frequency conversion; so, the stability of the intermediate signal frequency, which depends upon the balance between the local oscillation stability of two communicating transceivers, become worse and worse.
2.The higher the frequencies, the worse the Doppler effects become.This causes the $tability of the intermediate-frequency signal of the receiver to decrease.
3.The power consumption of the local oscillation generator increase heavily as the loca' oscillation frequency raises.
In order to solve the above adjacent interference, a means has been previously employed to set a guard band on a channel;
however, this occupies more bandwidth and therefore, reduces the frequency utilization ratio.Especially,in the cases of SSB
communications,this will become a big concern since the guard bandwidth will occupy considerable part of the each channe " s bandwidth.
In order to solve the above frequency-drift problem, some methods have been invented,including one of inbound pilot tone , etc..Nevertheless,the common ground of those methods are the device performance is restricted by its frequency response and the local oscillation frequency is still related to operating band frequency.For these reasons, it is limited to the applied range and condition of those methods.
In order to solve the above power consumption problem, an intermittent duty mode of receiver local oscillation has been employed but it may slow down the response of the system and makes no difference once in normal operation.
Therefore, the above problems have not been solved or entirely solved by known methods and much more effective communication appl_ances are required to respond to the needs of the developing communication industry and market. Existing radio appliances and the single carrier way of radio communication have exposed obvious defects and problems, which have impeded the development of the industry.
It is the object of the invention to provide improved methods, appliances and communication systems. It provide an improved communication system which can maintain the received signal carrier-frequency of the base station and get the receiver of the mobile station into the tuning state regardless of the movement of the mobile station. It also provides an improved receiver which is not influenced by the movement and the variance of operating frequency and limits the effect of Doppler frequency-shift and local oscillation frequency-shift without depending upon t~e improvement of device performance.
Furthermore, it enables the power consumption of the receiver' s local oscillation signal generator not to change as the frequency band of the received signal changes.
In a first aspect it provides a frequency stabilized communi-cation system which has, in combination,some receivers and /or transmitters of base station and mobile stations whose charac-teristic is that the frequency of reception and transmission assigned by the base station can be real-time modified ~y mobile station itself or according to the received signaling from base station as responsing to Doppler-shift caused by the movement of the mobile one so that the received carrier fre-quency of base that maintain always in a permissible range;and the receiver of mobile that is in accord with its signal throughout.
The radio receiver may be a dual carrier type and select the ~I the frequency of reception of the dual-carrier signals by mix-ing the signals with a local oscillation signal and frequency conversion of the dual-carrier signals is finished by the dual carrier signal mixed itself.
The dual-carrier receiver may have the feature that frequency difference between signal frequencies of the first local osci-lation and the dual-carrier frequencies are neither equal to the first intermediate frequency.
The dual-carrier may has the feature that said frequency-shift characteristics of the two carriers corresponds, but said carriers are different in frequency and modulated content.
The transceiver of mobile station and dual-carrier signals may have the feature that the unmodulated carrier signal, which is one of the dual-carrier,can be employed as part of the carrier signal of the transmitter.
In a second aspect the invention provides a frequency stabili-zed communication system with mobile stations and base station A Doppler frequency detective and corrective signal generation unit may be employed to the transceiver either of the mobile station or the base station. In the first case, the mobile station first receive the carrier signal from the base station and then, detect the amount of Doppler-shift in the received carrier signal. A transmitting and receiving frequency correc-ting signal will be generated by the unit then according to the detected amount of Doppler-shift and be used for real-time adjusting the transmitting and receiving frequencies of mobile transceiver so that the received carrier frequency of the base station that maintain always in a permissible range; and the receiver of the mobile that is in accord with its signal throughout. In the second case, instead of applying the unit to each mobile station, the unit is only employed to the bese station for real-time adjusting of the transmitting and recie-ving frequencies of all mobile transceivers which belong to ~I the same base station according to their states of movement . The unit applied to the transceiver of base station works in the same way as it is in the mobile transceiver and for the same purpose and effect besides that the Doppler-shift correc-ting signal is transmitted to each mobile transceiver by radio as command in signaling form. After ~he signaling is received, the mobile transceiver will make corresponding adjustments to their transmitting and receiving frequencies in the same way as if communication channel changes.
For a better understanding of the present invention and to more clearly how it may be carried into effect, reference will 219503g now be made by way of example to the accompanying drawings, which show the preferred embodiments of the prèsent invention and in which:
~igure 1 is a block diagram of mobile station transceiver with a Doppler shift detecting & correcting signal generative unit for automatic real-time control of transmitting and receiving frequencies.
~igure 2 is a block diagram of base station transceiver with a Doppler shift detecting & correcting signal generative unit for remote real-time control of transmitting and receiving frequencies of mobile transceivers.
~igure 3 is a block diagram of a dual-carrer receiver.
~igure 4 is an illustration of frequency stabilized mobile radio~communication system in which Doppler shift lS automatically corrected by mobile station.
~igure 5 is an illustration of frequency stabilized mobile radio communication system in wh~ch Doppler shift is remotely real-t~me corrected by base station.
Referring to FIG.1, a transceiver of mobile station works at frequencies set by base station initially. The mobile station receiver receives the signal from the base station and passes it to the transmitting carrier generator and to the Doppler shift detecting & correcting signal generative unit then. In the transmitting carrier generator, transmitting frequency is set initially according to the signaling from base station and a transmitting carrier signal is generated and provided to the modulator. Meanwhile, in the Doppler shift detecting &
correcting signal unit, carrier frequency of received signal is compared with a preset receiving frequency and if there is any difference between them, a frequency offset signal ~ F1 will be generated and passed to both the frequency selective unit of receiver and the modulation unit of transmitter to adjust their presetting frequencies and makes the frequency value deviate from the original value so that carrier signal received by base station is still equal to the presetting frequency value and meanwhile,the mobile station reception is always in signal-tuning condition despite the exist of rela-tive movement between mobile station and base station.
Referring to FIG.2, a transceiver of base station works at frequencies set by itself. A Doppler shift detecting & corre-cting signal generative unit in the transceiver works in the same way as it is in the mobile transceiver but the frequency offset signal ~ F2 is transferred by radio wave to the mobile stations as signaling form to remotely real-time control and correct the transmitting and receiving frequency of mobile transceiver. The effect of such an arrangement will be the same as that of FIG.1 but it prevents the Doppler-shift unit from being installed in every mobile transceivers which be-long to the same base station.
Referring to FIG.4, since the Doppler-shift unit is installed in mobile transceiver, supposing the mobile station is appro-aching the base station, the frequency received by the mobile station will be increased by Doppler-shift ~F.Thus,the mobile receiver need to adjust its receiving frequency by adding an offset value of ~F so that the signal-tuning condition can be maintained and meanwhile,to adjust its transmitting frequency by subtracting an offset value of ~ F so that the frequency of signal received by the base station will still be equal to its presetting value. So, the transmitting and receiving fre-quencies will always be as what are preset initially.
Referring to FIG.5, since the Doppler-shift unit is installed only in base station, signaling ~F2 is added as information signal by the base station and transferred to mobile stations . At mobile station,~F~2 is interpreted and transferred to a corresponding frequency offset value to correct transmitting .
and receiving frequencies. Supposing the mobile station is moving away from the base station, the actual signal frequency of received signal will be decreased by ~F owing to the exist of Doppler-shift.Therefore, the receiving frequency of mobile receiver need to be subtracted by an offset value ~F and mean-while, the transmitting frequency of the mobile transmitter need to be added by an offset value ~ F1 to get the equal affect as that of FIG.4 Referring to FIG.3, the receiver is a dual-carrier type. It receives two adjacent carrier signals which come from the same source when working.The carrier signals have different carrier frequency. One is a modulated carrier signal for the transfer of information; the other is an unmodulated signal for freque-ncy conversion and signal processing.
The first local oscillation signal of the ~eceiver is only employed to select frequency,and the unmodulated carrier is employed to change frequency. The receiver mixs a local osci-llation signal,whose frequency is much lower than the dual carrier frequency with the dual-carrier signal, then the mixed signal frequency is inserted into the range of two different parallel bandpass filters.The signals are separated from pass-ing through the respective filter to obtain the aim of freque-ncy selection and signal separation.
~I
The separated signal is transferred to another mixer.The mixed signal is an intermediate-frequency signal to implement the frequency conversion of modulated carrier signal. The interme-diate-frequency signal has subtracted the local oscillation drift component of receiver because of frequency difference.
Similarly, Doppler frequency-drift in the modulated carrier and the local oscillation signal drift of transmitter are mostly subtracted by the unmodulated carrier. Moreover, the local oscillation frequency range depends upon the received passband width as local oscillation signal is used for freque-ncy selection.Thus the frequency of local oscillation can be chosen much lower than the dual-carrier signal frequency, .he change of receiving signal frequency band has no influence on the local oscillation frequency. The power consumption of the local oscillation generator dose not change as the ~receiving frequency-band changes.
The receiver resolves some technical key problems of the pre-sent appliances entirely with conventional devices. The single sideband communication now is possible to be applied at any radio frequency band in mobile communication. Mobile communi-cation of stabilized frequency is provided for preferred embo-diment oï the receiver.
In FIG.3,the first local oscillation signal VO(t) is only used for selective frequency,the second local oscillation signal VO'(t) is applied to synchronous demodulation. Vl(t) is an un-modulated carrier signal. V2(t) is a modulated carrier signal.
Assuming that the frequency difference between two carrier frequencies is a defined value which has the same frequency as VO'(t),and narrow-band filter A and B has its fixed frequency and bandwidth.
_, signal Vl(t) and V2(t) are amplified by a pre-amplifier. The amplified signal transfers to mixer O to mix with the first local oscillation signal VO(t) so that dual-carrier signal out put from the mixer match respectively with the passbands of narrow-band filter A and B. Wlth this manner, the signal that passes through filter A and B is chosen and separated.There is only V2(t) component,in filter A output. There is only Vl(t) component in filter B output. The frequency selection process is finished until now.
Then, the output signal Vll(t) of filter B is transferred to a wa~-eform shaper B to eliminate an amplitude modulation genera-ted from Vl(t) because of radio transmission.V12(t) from wave-form shaper B are transferred respecti~ely to mixer A and C.
The frequency conversion is implemented in mixer A where the carrier signal V21(t) and V12(t),which are separated by narrow Z19~39 band filter A and B, are mixed to generate an IF signal V22(t) whose frequency is equal to the frequency difference between V12(t) and V21(t),which has no effect of frequency-drift VO(t) Most of Doppler frequency-shift in V21(t) and frequency-drift transmitter local oscillation are also offset by the same signal at Vll(t). The frequency-conversion process finished.
Signal V22(t) is conveyed to an IF amplifier for amplifying, thereafter mixed with the second local oscillation signal VO'(t) at mixer B to implement sync-demodulation of V22(t). At the same time,signal Vll(t) at mixer C mixes with V12(t) to demodulate amplitude modulation signal due to radio transmi-ssion. An output signal V13(t) of mixer C,which is filtered by lowpass filter C and amplified by amplifier B, has employed to control the amplification times of amplifier; A real-time to eliminate the amplitude modulation component in V2(t) because of radio transmission. Finally,the amplifier A output is fed to a synchronization unit whose output signal can enable VOl'(t) to maintain synchronization with signal V22(t) strict-ly for implementing to syn-demodulation of V23(t).
By applying a Doppler frequency detective & corrective signal generation unit to the transceiver equipment of either the base station or mobile station, a frequency stabilized commu-nication system can monitor the frequency-shift quantity of received signal,and give a corrective signal that enables the receiving and transmitting frequencies of mobile station to be changed as the mobile station state changes. So the received signal of base station maintains always in the signal channel width,the mobile receiver is in tuning condition.
By providing an improved receiver, a dual-carrier receiver, Doppler-shift and transceiver local oscillation signal drift can be extremely decreased without depending upon the device performance and the power consumption of mobile transceiver local oscillation signal generators will not change as the the operating band changes.
By applying the frequency stabilized communication system in mobile SSB communication, SSB mobile communication may be applicable at any radio frequency band and therefore,the each channel's bandwidth may be narrowed to 5KHz from 25KHz now, and power consumption of mobile transceiver may be reduced by 80%.
It will be understood that this description is made with reference to the prefer.red embodiments of the invention.
However, it is possible to make other embodiments that employ the principles of the invention and that fall within its spirit and scope as defined by the following claims.
.
In order to solve the above adjacent interference, a means has been previously employed to set a guard band on a channel;
however, this occupies more bandwidth and therefore, reduces the frequency utilization ratio.Especially,in the cases of SSB
communications,this will become a big concern since the guard bandwidth will occupy considerable part of the each channe " s bandwidth.
In order to solve the above frequency-drift problem, some methods have been invented,including one of inbound pilot tone , etc..Nevertheless,the common ground of those methods are the device performance is restricted by its frequency response and the local oscillation frequency is still related to operating band frequency.For these reasons, it is limited to the applied range and condition of those methods.
In order to solve the above power consumption problem, an intermittent duty mode of receiver local oscillation has been employed but it may slow down the response of the system and makes no difference once in normal operation.
Therefore, the above problems have not been solved or entirely solved by known methods and much more effective communication appl_ances are required to respond to the needs of the developing communication industry and market. Existing radio appliances and the single carrier way of radio communication have exposed obvious defects and problems, which have impeded the development of the industry.
It is the object of the invention to provide improved methods, appliances and communication systems. It provide an improved communication system which can maintain the received signal carrier-frequency of the base station and get the receiver of the mobile station into the tuning state regardless of the movement of the mobile station. It also provides an improved receiver which is not influenced by the movement and the variance of operating frequency and limits the effect of Doppler frequency-shift and local oscillation frequency-shift without depending upon t~e improvement of device performance.
Furthermore, it enables the power consumption of the receiver' s local oscillation signal generator not to change as the frequency band of the received signal changes.
In a first aspect it provides a frequency stabilized communi-cation system which has, in combination,some receivers and /or transmitters of base station and mobile stations whose charac-teristic is that the frequency of reception and transmission assigned by the base station can be real-time modified ~y mobile station itself or according to the received signaling from base station as responsing to Doppler-shift caused by the movement of the mobile one so that the received carrier fre-quency of base that maintain always in a permissible range;and the receiver of mobile that is in accord with its signal throughout.
The radio receiver may be a dual carrier type and select the ~I the frequency of reception of the dual-carrier signals by mix-ing the signals with a local oscillation signal and frequency conversion of the dual-carrier signals is finished by the dual carrier signal mixed itself.
The dual-carrier receiver may have the feature that frequency difference between signal frequencies of the first local osci-lation and the dual-carrier frequencies are neither equal to the first intermediate frequency.
The dual-carrier may has the feature that said frequency-shift characteristics of the two carriers corresponds, but said carriers are different in frequency and modulated content.
The transceiver of mobile station and dual-carrier signals may have the feature that the unmodulated carrier signal, which is one of the dual-carrier,can be employed as part of the carrier signal of the transmitter.
In a second aspect the invention provides a frequency stabili-zed communication system with mobile stations and base station A Doppler frequency detective and corrective signal generation unit may be employed to the transceiver either of the mobile station or the base station. In the first case, the mobile station first receive the carrier signal from the base station and then, detect the amount of Doppler-shift in the received carrier signal. A transmitting and receiving frequency correc-ting signal will be generated by the unit then according to the detected amount of Doppler-shift and be used for real-time adjusting the transmitting and receiving frequencies of mobile transceiver so that the received carrier frequency of the base station that maintain always in a permissible range; and the receiver of the mobile that is in accord with its signal throughout. In the second case, instead of applying the unit to each mobile station, the unit is only employed to the bese station for real-time adjusting of the transmitting and recie-ving frequencies of all mobile transceivers which belong to ~I the same base station according to their states of movement . The unit applied to the transceiver of base station works in the same way as it is in the mobile transceiver and for the same purpose and effect besides that the Doppler-shift correc-ting signal is transmitted to each mobile transceiver by radio as command in signaling form. After ~he signaling is received, the mobile transceiver will make corresponding adjustments to their transmitting and receiving frequencies in the same way as if communication channel changes.
For a better understanding of the present invention and to more clearly how it may be carried into effect, reference will 219503g now be made by way of example to the accompanying drawings, which show the preferred embodiments of the prèsent invention and in which:
~igure 1 is a block diagram of mobile station transceiver with a Doppler shift detecting & correcting signal generative unit for automatic real-time control of transmitting and receiving frequencies.
~igure 2 is a block diagram of base station transceiver with a Doppler shift detecting & correcting signal generative unit for remote real-time control of transmitting and receiving frequencies of mobile transceivers.
~igure 3 is a block diagram of a dual-carrer receiver.
~igure 4 is an illustration of frequency stabilized mobile radio~communication system in which Doppler shift lS automatically corrected by mobile station.
~igure 5 is an illustration of frequency stabilized mobile radio communication system in wh~ch Doppler shift is remotely real-t~me corrected by base station.
Referring to FIG.1, a transceiver of mobile station works at frequencies set by base station initially. The mobile station receiver receives the signal from the base station and passes it to the transmitting carrier generator and to the Doppler shift detecting & correcting signal generative unit then. In the transmitting carrier generator, transmitting frequency is set initially according to the signaling from base station and a transmitting carrier signal is generated and provided to the modulator. Meanwhile, in the Doppler shift detecting &
correcting signal unit, carrier frequency of received signal is compared with a preset receiving frequency and if there is any difference between them, a frequency offset signal ~ F1 will be generated and passed to both the frequency selective unit of receiver and the modulation unit of transmitter to adjust their presetting frequencies and makes the frequency value deviate from the original value so that carrier signal received by base station is still equal to the presetting frequency value and meanwhile,the mobile station reception is always in signal-tuning condition despite the exist of rela-tive movement between mobile station and base station.
Referring to FIG.2, a transceiver of base station works at frequencies set by itself. A Doppler shift detecting & corre-cting signal generative unit in the transceiver works in the same way as it is in the mobile transceiver but the frequency offset signal ~ F2 is transferred by radio wave to the mobile stations as signaling form to remotely real-time control and correct the transmitting and receiving frequency of mobile transceiver. The effect of such an arrangement will be the same as that of FIG.1 but it prevents the Doppler-shift unit from being installed in every mobile transceivers which be-long to the same base station.
Referring to FIG.4, since the Doppler-shift unit is installed in mobile transceiver, supposing the mobile station is appro-aching the base station, the frequency received by the mobile station will be increased by Doppler-shift ~F.Thus,the mobile receiver need to adjust its receiving frequency by adding an offset value of ~F so that the signal-tuning condition can be maintained and meanwhile,to adjust its transmitting frequency by subtracting an offset value of ~ F so that the frequency of signal received by the base station will still be equal to its presetting value. So, the transmitting and receiving fre-quencies will always be as what are preset initially.
Referring to FIG.5, since the Doppler-shift unit is installed only in base station, signaling ~F2 is added as information signal by the base station and transferred to mobile stations . At mobile station,~F~2 is interpreted and transferred to a corresponding frequency offset value to correct transmitting .
and receiving frequencies. Supposing the mobile station is moving away from the base station, the actual signal frequency of received signal will be decreased by ~F owing to the exist of Doppler-shift.Therefore, the receiving frequency of mobile receiver need to be subtracted by an offset value ~F and mean-while, the transmitting frequency of the mobile transmitter need to be added by an offset value ~ F1 to get the equal affect as that of FIG.4 Referring to FIG.3, the receiver is a dual-carrier type. It receives two adjacent carrier signals which come from the same source when working.The carrier signals have different carrier frequency. One is a modulated carrier signal for the transfer of information; the other is an unmodulated signal for freque-ncy conversion and signal processing.
The first local oscillation signal of the ~eceiver is only employed to select frequency,and the unmodulated carrier is employed to change frequency. The receiver mixs a local osci-llation signal,whose frequency is much lower than the dual carrier frequency with the dual-carrier signal, then the mixed signal frequency is inserted into the range of two different parallel bandpass filters.The signals are separated from pass-ing through the respective filter to obtain the aim of freque-ncy selection and signal separation.
~I
The separated signal is transferred to another mixer.The mixed signal is an intermediate-frequency signal to implement the frequency conversion of modulated carrier signal. The interme-diate-frequency signal has subtracted the local oscillation drift component of receiver because of frequency difference.
Similarly, Doppler frequency-drift in the modulated carrier and the local oscillation signal drift of transmitter are mostly subtracted by the unmodulated carrier. Moreover, the local oscillation frequency range depends upon the received passband width as local oscillation signal is used for freque-ncy selection.Thus the frequency of local oscillation can be chosen much lower than the dual-carrier signal frequency, .he change of receiving signal frequency band has no influence on the local oscillation frequency. The power consumption of the local oscillation generator dose not change as the ~receiving frequency-band changes.
The receiver resolves some technical key problems of the pre-sent appliances entirely with conventional devices. The single sideband communication now is possible to be applied at any radio frequency band in mobile communication. Mobile communi-cation of stabilized frequency is provided for preferred embo-diment oï the receiver.
In FIG.3,the first local oscillation signal VO(t) is only used for selective frequency,the second local oscillation signal VO'(t) is applied to synchronous demodulation. Vl(t) is an un-modulated carrier signal. V2(t) is a modulated carrier signal.
Assuming that the frequency difference between two carrier frequencies is a defined value which has the same frequency as VO'(t),and narrow-band filter A and B has its fixed frequency and bandwidth.
_, signal Vl(t) and V2(t) are amplified by a pre-amplifier. The amplified signal transfers to mixer O to mix with the first local oscillation signal VO(t) so that dual-carrier signal out put from the mixer match respectively with the passbands of narrow-band filter A and B. Wlth this manner, the signal that passes through filter A and B is chosen and separated.There is only V2(t) component,in filter A output. There is only Vl(t) component in filter B output. The frequency selection process is finished until now.
Then, the output signal Vll(t) of filter B is transferred to a wa~-eform shaper B to eliminate an amplitude modulation genera-ted from Vl(t) because of radio transmission.V12(t) from wave-form shaper B are transferred respecti~ely to mixer A and C.
The frequency conversion is implemented in mixer A where the carrier signal V21(t) and V12(t),which are separated by narrow Z19~39 band filter A and B, are mixed to generate an IF signal V22(t) whose frequency is equal to the frequency difference between V12(t) and V21(t),which has no effect of frequency-drift VO(t) Most of Doppler frequency-shift in V21(t) and frequency-drift transmitter local oscillation are also offset by the same signal at Vll(t). The frequency-conversion process finished.
Signal V22(t) is conveyed to an IF amplifier for amplifying, thereafter mixed with the second local oscillation signal VO'(t) at mixer B to implement sync-demodulation of V22(t). At the same time,signal Vll(t) at mixer C mixes with V12(t) to demodulate amplitude modulation signal due to radio transmi-ssion. An output signal V13(t) of mixer C,which is filtered by lowpass filter C and amplified by amplifier B, has employed to control the amplification times of amplifier; A real-time to eliminate the amplitude modulation component in V2(t) because of radio transmission. Finally,the amplifier A output is fed to a synchronization unit whose output signal can enable VOl'(t) to maintain synchronization with signal V22(t) strict-ly for implementing to syn-demodulation of V23(t).
By applying a Doppler frequency detective & corrective signal generation unit to the transceiver equipment of either the base station or mobile station, a frequency stabilized commu-nication system can monitor the frequency-shift quantity of received signal,and give a corrective signal that enables the receiving and transmitting frequencies of mobile station to be changed as the mobile station state changes. So the received signal of base station maintains always in the signal channel width,the mobile receiver is in tuning condition.
By providing an improved receiver, a dual-carrier receiver, Doppler-shift and transceiver local oscillation signal drift can be extremely decreased without depending upon the device performance and the power consumption of mobile transceiver local oscillation signal generators will not change as the the operating band changes.
By applying the frequency stabilized communication system in mobile SSB communication, SSB mobile communication may be applicable at any radio frequency band and therefore,the each channel's bandwidth may be narrowed to 5KHz from 25KHz now, and power consumption of mobile transceiver may be reduced by 80%.
It will be understood that this description is made with reference to the prefer.red embodiments of the invention.
However, it is possible to make other embodiments that employ the principles of the invention and that fall within its spirit and scope as defined by the following claims.
.
Claims (6)
- The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
l.A frequency stabilized communication system, comprising some receivers and transmitters in a first station and a second station, whose characteristics are that the frequencies of reception and transmission initially assigned to the first station by the second station can be real-time modified by the first station or by the second station through signaling according to the moving state of the first station and the receivers may be dual-carrier receiver so that the received carrier frequency of the second station that maintain always in a pre-determined range; the receiver of the first station that is in accord with the signal throughout and the IF signal of the receiver is less affected by signal Doppler-shift and local oscillation frequency-drifts of both receiver and transmitter. - 2.A system according to claim 1, wherein: the dual-carrier receiver selects the frequency of reception of the dual-carrier signal by mixing a first local oscillation signal with the dual -carrier signal and accomplishes signal frequency conversion by the dual-carrier signal mixed itself.
- 3.The combination defined in claim 2 wherein:the receiver whose feature is that frequency difference between signal frequency of the first local oscillation and carrier frequency of dual carrier signal is not equal to the first intermediate frequency
- 4.The combination defined in claim 2 wherein:the receiver whose feature is that said frequency-drift characteristic of two carriers corresponds,but said frequency and modulated content dose not correspond.
- 5.A frequency stabilized communication system defined in claim 1 wherein: the transceiver also comprising a Doppler frequency detective and corrective signal generation unit in either the first station or the second station, whose characteristics are to detect Doppler-shft by comparing the frequency difference between the carrier frequency of received signal and the preset frequency of reception and to generate a corrective signal accordingly in the form of either a frequency offset value or a signaling to directly modify the transmitting and receiving carrier frequencies of the first station or through radiowave remotely controlled by the second station.
- 6.The combination defined in claim 1,2 wherein said transmitter and receiver of the first station and dual-carrier signal whose feature is that unmodulated carrier, which is one of the dual-carrier, can be employed to comprise part of the carrier signal of the transmitter.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96204043.6 | 1996-02-05 | ||
| CN96204043 | 1996-02-05 | ||
| CN96111894.6 | 1996-08-28 | ||
| CN96111894 | 1996-08-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2195039A1 true CA2195039A1 (en) | 1997-08-06 |
Family
ID=25743995
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002195039A Abandoned CA2195039A1 (en) | 1996-02-05 | 1997-01-14 | Frequency stabilized communication system |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2195039A1 (en) |
| WO (1) | WO1997029599A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4689806A (en) * | 1983-11-07 | 1987-08-25 | Hughes Aircraft Company | Receiver mode control for acquiring and tracking a signal |
| US4726069A (en) * | 1984-05-18 | 1988-02-16 | Stevenson Carl R | A muiti-mode modulation and demodulation system and method |
| DE3729586A1 (en) * | 1987-09-04 | 1989-03-16 | Ant Nachrichtentech | METHOD FOR COMPENSATING DURING DURATION OF THE BURSTS Caused by the DOPPLER EFFECT IN A TDMA FRAME, AND ARRANGEMENT |
| US5095538A (en) * | 1989-09-29 | 1992-03-10 | Motorola, Inc. | Calibrated method and device for narrow band Doppler compensation |
-
1997
- 1997-01-14 CA CA002195039A patent/CA2195039A1/en not_active Abandoned
- 1997-02-04 WO PCT/CN1997/000008 patent/WO1997029599A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO1997029599A1 (en) | 1997-08-14 |
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| Date | Code | Title | Description |
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| FZDE | Dead |