CA2136443A1 - Method and apparatus for separating channels from a radio frequency transmitter - Google Patents
Method and apparatus for separating channels from a radio frequency transmitterInfo
- Publication number
- CA2136443A1 CA2136443A1 CA002136443A CA2136443A CA2136443A1 CA 2136443 A1 CA2136443 A1 CA 2136443A1 CA 002136443 A CA002136443 A CA 002136443A CA 2136443 A CA2136443 A CA 2136443A CA 2136443 A1 CA2136443 A1 CA 2136443A1
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- CA
- Canada
- Prior art keywords
- port
- signal
- frequency
- circulator
- transfer module
- 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
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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
- H04B1/02—Transmitters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/213—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies
- H01P1/2138—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies using hollow waveguide filters
-
- 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
- H04B1/02—Transmitters
- H04B1/04—Circuits
- H04B1/0483—Transmitters with multiple parallel paths
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Transmitters (AREA)
- Transceivers (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
A method and apparatus are provided for separating spectrally diverse radio frequency signals. The apparatus includes means, within a signal transfer module (23), for transferring an input signal received at a first port of the signal transfer module (23) to a second port of the signal transfer module. At least one frequency selective assembly (37, 24) is included, interconnected with the second port of the signal transfer module, presenting a characteristic impedance to a desired signal of the input signal and reflecting of their signals of the input signal to the second port of the frequency transfer module. A means, within the signal transfer module for transferring a reflected signal received at the second port of the signal transfer module to a third port of the signal transfer module is also included. A first antenna (31) is interconnected with the frequency selective cavity assembly for transmission of the desired signal. A second antenna (30) is interconnected with the third port of the signal transfer module for transmission of the other signals. The method of practising the invention is also provided.
Description
2 21~ 6 ~ PCT/IJ594/03007 }
I
i ,~ .
METHOD AND APPARATUS FOR SEPARATING CHANNEL,S
F~OM A RADIO F~<EQI~NCY TRANSMIl~ER
Field of the lnvention The. field of the invention relates to co~nunication systems and, more particularly, to cellular communication systenns.
Background of the lnvention Cellular systems simultaneously handling a number of traffic channels through each base station are 1 S typically assigned a number of channels (f1-fn) in support of communications with mobile communication uni~s through local base stations. Each base station is, in turn, allotted a subset of ~he channels (fl-fn). Of the subset of channels assigned to a base site at least one 2 0 ~and often more) is designated as a control channel for purposes of access control and channel set-up.
Communication with a cornmunication unit on a traf~lc channel within a service coverage area of the base site is often accomplished through an 2 5 omnidirectional antenna centrally locatecl within the service coverage area. A number of communications may be simultaneously supported through the antenna with each individual communication supported by a transmitter (located at the base site) assigned to the 3 0 traffic channel. Each transmitter includes a modulated transmit signal source~ within the transceiver and a radio frequency (RF) power ampli~ler). Each transmitter thereby provi~es signal generation, modulation and amplification.
3 5 ln contrast to traffic channels, control inforrnation from a base site is often transceived from a number of directional antennas that divide the service coverage area into a number of sectors. Dividing the service 2136A(l~.~
W094/24772 P~T/~JS94/03007 - 2 - , coverage area into sectors for control channel purposes provides a means for the base site ~o determine the relative position of a communication unit for purposes of handoff.
S The simultaneous transmission of a number of traf~lc channel signals from the central antenna requires that trans~mitter output of each active transceiver be combined before application to, and transmission from, the central antenna. In order to avoid interference-- 10 producing intermodulation products, signals must be combined after any non-linear steps within the amplification process. In addition, the combinin~
topology must provide sufficien~ reverse isolation to insure that signals of parallel amplification branches will not be coupled into the output of other power amplifiers, again producing intermodulation products.
Where each transceiver is equipped with its own power ampli~ler (PA), combining must occur after the PA where sigrlal levels, as well as combining losses, are 2 0 high. A cavity combiner, for combining such high level RF signals while providing the necessary isolation, is provided by U.S. Patent No. 4,667,172 assigned to the assignee of the present invention.
An explanation of the operation of a cavity 2 5 combiner and of the interconnectin~ one-quarter wavelength interconnect facilities follows. A cavity combiner includes a mlmber of frequency selective cavities, each resonant at a tuned frequency, interconnected at a combiner junction by a transmission ~ -3 0 line of a length essentially equal to one-quarter waveiength at the tuned frequency. A number of such frequency selective cavities and one-quarter wavelength cables ~cavity assemblies) interconnected at a combiner junction, provide a means for combining a 3 5 number of RF signals. I
A cavity combiner presents (at the tuned . ' frequency) an impedance equal to that of the characteristic (matched) impedance of the system :~ W094/~77~ 21 3~ PC'rlUS94/03007 (typically 50 Q) to a desired signal frequency from an amplifier through the frequency selective cavity to the combiner junction. A si,,nal presentecl at the cavity combiner, in the reverse direction, from the combiner 5 junction, at other than the tuned frequency~ would be presented with a low impedance. The low impedance is transformed by the one-quarter wavelength cable into a hi~h impedance at the combiner junction. The high impedance at the combiner junction prevents adjacent 10 combiner branches from mutually loading one another, while the cavity selectivity provides an adequate level of si~nal isolation between adjacent branches.
While the process of combining high level RF
signals works well the power loss, in terms of actual 15 power dissipation, is significant. Power loss within a combiner is typically 3 db.
A circulator is known to transfer RF signals received at a first port to a second port and to a load interconnected with the second port. If an impedance 2 0 mismatch is presented at the second port, a proportional amount of the RF signal is reflected back and becomes an input at the second port of the circulator. Since the circulator transfers input signals received at ~ second port to a third port, the reflected RF sicnal is transferred 2 5 to (and dissipated) within a load often interconnected with the ~hird port.
Radio ` frequency (RF) circulators are known in the art of RF communications (see, for example, U~H~F.
Techniques for Lumped Constant Circulators, by J. ..
3 0 Helszajn and F. M. Aitkent, Electronic En~ineering, Nov., 1973) and used for purposes of signal steering, switching, isolatin~, etc. The most cornrnon use of circulators is to protect RF transmitter from damage due to open-circuits between the transmitter and an 3 5 a~sociated load.
In other communication systems, transceivers are not equipped with individual PAs~ instead. a common~
multitone linear PA (LPA) is used for amplification after WO 9412L2~L 3 6 ~ PCT/US94/03007 : ~-i. ..... ~., the RF signals have been combined at relatively low power levels at the output of the transceiver. The use of such common LPA for tra~fic channels in systems using a common antenna has resulted iII considerable 5 simplification of system topology, improvements in system efficiency, and reduction in system size. In other systems, operating under a sector format7 the use of LPAs is not as attrac$ive because of the difficulty in separa~inG RF signals following amplification in the LPA.
10 Because of ~he importance of power efficiency in cornmunication systems a need exists for a method of isolatinc RF channels for sector transmission following amplification in a comrnon LPA.
Summary of ~he lnvention A method and apparatus is provided for separating spectrally diverse radio frequency signals.
2 O The apparatus includes means, within a signal transfer module, for transferring an input signal received at a first port of the signal transfer module to a second port of the signal transfer module. At least one frequency selective assembly is included, in~erconnected with the 2 5 second port of the signal transfer module, presenting a characteristic impedance to a desired signal of the input signal and reflecting other signals of the input signal to the second port of the frequency transfer module. A
means, within the signal transfer module for 3 0 transferring a reflected signal received at the second port of the signal transfer module to a third port of the signal transfer module is also included. The method of practicing the invention is also provided Brief Description of the Drawings :` WO941~4777 ~13fi ~ CT/US~4103007 S
" ' .
FIG. 1 is a block diagram of a communication ~-system base site in accordance with an embodiment of the invention.
Detailed Description of the Preferred Embodiment The solution to the problem of separatin~
previously combined RF~ signals ~following amplification in a common LPA~ lies conceptually in the use of a signal transfer module (e.g., an RF circulator) and a frequency selective cavity assembly interconnected with a second port of the signal transfer module. It has been deterr~ined that the use of a signal transfer module in conjunction with a frequency selective cavity assembly produces the unexpec~ed result of separating a first RF si~,nal, of a ~requency to which the cavity is tuned, for application ~o a first antenna while routing other signals to a second antenna. Such a device has been determined to be useful in cellular system base 2 0 sites (e.g., where traf~lc channels are transmitted frorn a common, omni antenna and control channels are transmitted from sector antennas).
The output of an LPA (containing a control channel to be separated from a number of traffic channels) is applied to a first port of the circulator. An RF input presented to a first port of a circulator, as is known in the art, will be transferred to the second port of the circulator. In a sys~em having a characteristic impedànce (e.~., 50 S2), the frequency selec~ive cavity 3 0 assembly, interconnected with the second port of the '.
circul`ator, presents a~ 50Q path for the control channel, to which it is tuned, to a sector antenna and a high impedance path at the cavity junction for the traffic channels (outside a pass band of the cavity). The high 3 5 irllpedance presented to the traffic channel signals at the cavity junction causes the traffic channel signals to be reflected back into the second port of the circulator.
The circulator, receiving an input RF signal at its second 2 :~ 3 6 ~ l1 3 `~ ~
WO 941~4772 PCT/US94/03007 ^~
~;, port, transfers the reflected RF signal to a third port of the circulator. An omni antenna interconnected with the third port of the circulator presents a load to the circulator and a path for transmission of the traffic 5 signals.
The frequency selective cavity assembly includes a frequency selective cavity and a transmission line interconnecting the frequency selective cavity to the second port of the circulator. The transmission line is l 0 essentially one-quarter wavelength long at the frequency ba~d of the desired control channel. Each frequency selective cavity is tuned to the frequency of one selected control channel.
FIG. 1 is a bloc~ diagram of a cellular base site lO
15 in accordance with an embodiment of the invention.
The base site has a single omni antenna 30 and a number of sector antennas 31-36. The omni antenna is used generally for transmitting traffic channels within a service coverage area (not shown) of the base site 10.
2 0 The sector antenna 31-36 are each used for transmitting control information within a portion (e.g., a 60 degree sector of the service coverage area.
Traffic channel information originating from within a public switch telephone network (PSTN) or 2 5 another base site 10 is routed to appropriate traffic channel transceivers 13-14 by the controller 12.
Control information originating within the controller 12 is also routed to control transceivers 15-20. The low-level output signals of the transceivers 13-20 are 3 0 combined within the combiner 21 through resistive combining techniques for i subsequent amplification within the LPA 22. Within the LPA 22 the combi~ed signals are amplified to a level sufficient for transmission from the omni 30 or sectored 31-36 `
3 5 antennas Following amplification within the LPA 22 the combined signal is applied to port 1 of the circulator 23.
The combined signal is transferred to port 2 of the . ~ .... " . . .. ~ .. . .. .. .
-: WO 94/24772 213 (~ PCT/US94/03007 r circulator 23. At the output of port 2 the signal passes through a splitting junction 43 and a number of transmission lines 37-42 to frequency selective cavi~ies 24-29 .
Each frequency selective cavity 24-29 is tuned to the frequency of a control channel to be transmitted through ~the associated sector antenna 31-36. The interconnec~ed cables 37-42 have a length substantially equal to one-quarter the wavelength at the desired control channel frequency.
The use of the one-quarter wavelength cable (of the typical characteristic impedance of typically 50Q) and frequency selective cavity presents a low loss path to the desired control channel signal for transmission from the associated sector antenna. The characteristic impedance presented by the frequency selective cavity assembly also prevents a reflection of the desired control channel signal back to the junction 43 or to the second port of the circulator 23.
2 0 Traffic channel frequencies reachin~ the junction 43, on the other hand, are presented with a high impedance. Upon reaching the junction 43, the reflected traf~lc channel signals (undesired signals) are reflected back to the second port of the circulator 23. Upon being 2 5 reflected into the the circulator (as an input), the undesired signals are trans~erred to the third port of th circulator 23. The ornni antenna 30 interconnected to the third port of the circulator 23 presents a load for the traf~lc channel signals and a path for transmission of the 3 0 - si~nals.
The use of the circulator 23 and frequency selective cavity assemblies improves communication systems by reducin~ the cost and improvin~ the reliability and efficiency of such systems. The use of a ~-3 5 cornmon LPA reduces the cost of transmitters within such a system by reducing the parts required to build such as system and by utilizino the LPA to a higher capacity for a better efficiency. The use of a common 2l3fi4a3 LPA allows for a reduction in the size of such a system by concentrating power amplification to a single area.
The use of a common LPA further allows the dyn~m~c changin(J of system topologies (e.g, the reassignment of S transceiver from one service coverage area to another).
The many features and advanta,~es of this invention are apparent from the detailed specification and thus it is intended by the appended claims tO cover all such features and advanta,~es of the system which fall within the true spirit and scope of the invention.
Further, since numerous modifications and changes will readily occur to those skilled in the art (e.g., use within commercial transmission systems)~ it is not desired to limit the invention to the exact construction and operation illustrated and describe~d~ and accordin~ly all suitable modi~lcations and equivalents (e.g., orn~i-sector, sector-omni, ornni-omni, and sector-sector channel separators) may be resorted to, falling within the scope of the inventian.
?. O An omni-sector separator may be used, for instance, where a separated control channel is transmitted on an omni antenna and reflected traffic channels are transmitted from directional antennas. An omni-sector channel separator may also ~lnd usefulness 2 5 in -cases where geographic obstructions cause poor illumination of a service area from the central omni antenna, which can be remedied by a single channel sector antenna placed in close proximity and powered from the same LPA. An omni-sector channel separator 3 0 may further find usefulness in cases where geo~raphic cond;tions cause interfere;nce to other service areas on selected channels radiated from the central omni antenna by separating those channels and radiatin~
them from sector antennas into specific service areas. A
35 sector-sector channel separator may be useful where directional antenna for traffic and control do not coincide.
WO9S12477~ 2136~ PCTluS94/03007 h~
It is, of course~ to be understood that the present invention is, by no means, limited to the specific showin~ in the drawing, but also comprises any modification within the scope of the appended claims.
t .
: `
I
i ,~ .
METHOD AND APPARATUS FOR SEPARATING CHANNEL,S
F~OM A RADIO F~<EQI~NCY TRANSMIl~ER
Field of the lnvention The. field of the invention relates to co~nunication systems and, more particularly, to cellular communication systenns.
Background of the lnvention Cellular systems simultaneously handling a number of traffic channels through each base station are 1 S typically assigned a number of channels (f1-fn) in support of communications with mobile communication uni~s through local base stations. Each base station is, in turn, allotted a subset of ~he channels (fl-fn). Of the subset of channels assigned to a base site at least one 2 0 ~and often more) is designated as a control channel for purposes of access control and channel set-up.
Communication with a cornmunication unit on a traf~lc channel within a service coverage area of the base site is often accomplished through an 2 5 omnidirectional antenna centrally locatecl within the service coverage area. A number of communications may be simultaneously supported through the antenna with each individual communication supported by a transmitter (located at the base site) assigned to the 3 0 traffic channel. Each transmitter includes a modulated transmit signal source~ within the transceiver and a radio frequency (RF) power ampli~ler). Each transmitter thereby provi~es signal generation, modulation and amplification.
3 5 ln contrast to traffic channels, control inforrnation from a base site is often transceived from a number of directional antennas that divide the service coverage area into a number of sectors. Dividing the service 2136A(l~.~
W094/24772 P~T/~JS94/03007 - 2 - , coverage area into sectors for control channel purposes provides a means for the base site ~o determine the relative position of a communication unit for purposes of handoff.
S The simultaneous transmission of a number of traf~lc channel signals from the central antenna requires that trans~mitter output of each active transceiver be combined before application to, and transmission from, the central antenna. In order to avoid interference-- 10 producing intermodulation products, signals must be combined after any non-linear steps within the amplification process. In addition, the combinin~
topology must provide sufficien~ reverse isolation to insure that signals of parallel amplification branches will not be coupled into the output of other power amplifiers, again producing intermodulation products.
Where each transceiver is equipped with its own power ampli~ler (PA), combining must occur after the PA where sigrlal levels, as well as combining losses, are 2 0 high. A cavity combiner, for combining such high level RF signals while providing the necessary isolation, is provided by U.S. Patent No. 4,667,172 assigned to the assignee of the present invention.
An explanation of the operation of a cavity 2 5 combiner and of the interconnectin~ one-quarter wavelength interconnect facilities follows. A cavity combiner includes a mlmber of frequency selective cavities, each resonant at a tuned frequency, interconnected at a combiner junction by a transmission ~ -3 0 line of a length essentially equal to one-quarter waveiength at the tuned frequency. A number of such frequency selective cavities and one-quarter wavelength cables ~cavity assemblies) interconnected at a combiner junction, provide a means for combining a 3 5 number of RF signals. I
A cavity combiner presents (at the tuned . ' frequency) an impedance equal to that of the characteristic (matched) impedance of the system :~ W094/~77~ 21 3~ PC'rlUS94/03007 (typically 50 Q) to a desired signal frequency from an amplifier through the frequency selective cavity to the combiner junction. A si,,nal presentecl at the cavity combiner, in the reverse direction, from the combiner 5 junction, at other than the tuned frequency~ would be presented with a low impedance. The low impedance is transformed by the one-quarter wavelength cable into a hi~h impedance at the combiner junction. The high impedance at the combiner junction prevents adjacent 10 combiner branches from mutually loading one another, while the cavity selectivity provides an adequate level of si~nal isolation between adjacent branches.
While the process of combining high level RF
signals works well the power loss, in terms of actual 15 power dissipation, is significant. Power loss within a combiner is typically 3 db.
A circulator is known to transfer RF signals received at a first port to a second port and to a load interconnected with the second port. If an impedance 2 0 mismatch is presented at the second port, a proportional amount of the RF signal is reflected back and becomes an input at the second port of the circulator. Since the circulator transfers input signals received at ~ second port to a third port, the reflected RF sicnal is transferred 2 5 to (and dissipated) within a load often interconnected with the ~hird port.
Radio ` frequency (RF) circulators are known in the art of RF communications (see, for example, U~H~F.
Techniques for Lumped Constant Circulators, by J. ..
3 0 Helszajn and F. M. Aitkent, Electronic En~ineering, Nov., 1973) and used for purposes of signal steering, switching, isolatin~, etc. The most cornrnon use of circulators is to protect RF transmitter from damage due to open-circuits between the transmitter and an 3 5 a~sociated load.
In other communication systems, transceivers are not equipped with individual PAs~ instead. a common~
multitone linear PA (LPA) is used for amplification after WO 9412L2~L 3 6 ~ PCT/US94/03007 : ~-i. ..... ~., the RF signals have been combined at relatively low power levels at the output of the transceiver. The use of such common LPA for tra~fic channels in systems using a common antenna has resulted iII considerable 5 simplification of system topology, improvements in system efficiency, and reduction in system size. In other systems, operating under a sector format7 the use of LPAs is not as attrac$ive because of the difficulty in separa~inG RF signals following amplification in the LPA.
10 Because of ~he importance of power efficiency in cornmunication systems a need exists for a method of isolatinc RF channels for sector transmission following amplification in a comrnon LPA.
Summary of ~he lnvention A method and apparatus is provided for separating spectrally diverse radio frequency signals.
2 O The apparatus includes means, within a signal transfer module, for transferring an input signal received at a first port of the signal transfer module to a second port of the signal transfer module. At least one frequency selective assembly is included, in~erconnected with the 2 5 second port of the signal transfer module, presenting a characteristic impedance to a desired signal of the input signal and reflecting other signals of the input signal to the second port of the frequency transfer module. A
means, within the signal transfer module for 3 0 transferring a reflected signal received at the second port of the signal transfer module to a third port of the signal transfer module is also included. The method of practicing the invention is also provided Brief Description of the Drawings :` WO941~4777 ~13fi ~ CT/US~4103007 S
" ' .
FIG. 1 is a block diagram of a communication ~-system base site in accordance with an embodiment of the invention.
Detailed Description of the Preferred Embodiment The solution to the problem of separatin~
previously combined RF~ signals ~following amplification in a common LPA~ lies conceptually in the use of a signal transfer module (e.g., an RF circulator) and a frequency selective cavity assembly interconnected with a second port of the signal transfer module. It has been deterr~ined that the use of a signal transfer module in conjunction with a frequency selective cavity assembly produces the unexpec~ed result of separating a first RF si~,nal, of a ~requency to which the cavity is tuned, for application ~o a first antenna while routing other signals to a second antenna. Such a device has been determined to be useful in cellular system base 2 0 sites (e.g., where traf~lc channels are transmitted frorn a common, omni antenna and control channels are transmitted from sector antennas).
The output of an LPA (containing a control channel to be separated from a number of traffic channels) is applied to a first port of the circulator. An RF input presented to a first port of a circulator, as is known in the art, will be transferred to the second port of the circulator. In a sys~em having a characteristic impedànce (e.~., 50 S2), the frequency selec~ive cavity 3 0 assembly, interconnected with the second port of the '.
circul`ator, presents a~ 50Q path for the control channel, to which it is tuned, to a sector antenna and a high impedance path at the cavity junction for the traffic channels (outside a pass band of the cavity). The high 3 5 irllpedance presented to the traffic channel signals at the cavity junction causes the traffic channel signals to be reflected back into the second port of the circulator.
The circulator, receiving an input RF signal at its second 2 :~ 3 6 ~ l1 3 `~ ~
WO 941~4772 PCT/US94/03007 ^~
~;, port, transfers the reflected RF signal to a third port of the circulator. An omni antenna interconnected with the third port of the circulator presents a load to the circulator and a path for transmission of the traffic 5 signals.
The frequency selective cavity assembly includes a frequency selective cavity and a transmission line interconnecting the frequency selective cavity to the second port of the circulator. The transmission line is l 0 essentially one-quarter wavelength long at the frequency ba~d of the desired control channel. Each frequency selective cavity is tuned to the frequency of one selected control channel.
FIG. 1 is a bloc~ diagram of a cellular base site lO
15 in accordance with an embodiment of the invention.
The base site has a single omni antenna 30 and a number of sector antennas 31-36. The omni antenna is used generally for transmitting traffic channels within a service coverage area (not shown) of the base site 10.
2 0 The sector antenna 31-36 are each used for transmitting control information within a portion (e.g., a 60 degree sector of the service coverage area.
Traffic channel information originating from within a public switch telephone network (PSTN) or 2 5 another base site 10 is routed to appropriate traffic channel transceivers 13-14 by the controller 12.
Control information originating within the controller 12 is also routed to control transceivers 15-20. The low-level output signals of the transceivers 13-20 are 3 0 combined within the combiner 21 through resistive combining techniques for i subsequent amplification within the LPA 22. Within the LPA 22 the combi~ed signals are amplified to a level sufficient for transmission from the omni 30 or sectored 31-36 `
3 5 antennas Following amplification within the LPA 22 the combined signal is applied to port 1 of the circulator 23.
The combined signal is transferred to port 2 of the . ~ .... " . . .. ~ .. . .. .. .
-: WO 94/24772 213 (~ PCT/US94/03007 r circulator 23. At the output of port 2 the signal passes through a splitting junction 43 and a number of transmission lines 37-42 to frequency selective cavi~ies 24-29 .
Each frequency selective cavity 24-29 is tuned to the frequency of a control channel to be transmitted through ~the associated sector antenna 31-36. The interconnec~ed cables 37-42 have a length substantially equal to one-quarter the wavelength at the desired control channel frequency.
The use of the one-quarter wavelength cable (of the typical characteristic impedance of typically 50Q) and frequency selective cavity presents a low loss path to the desired control channel signal for transmission from the associated sector antenna. The characteristic impedance presented by the frequency selective cavity assembly also prevents a reflection of the desired control channel signal back to the junction 43 or to the second port of the circulator 23.
2 0 Traffic channel frequencies reachin~ the junction 43, on the other hand, are presented with a high impedance. Upon reaching the junction 43, the reflected traf~lc channel signals (undesired signals) are reflected back to the second port of the circulator 23. Upon being 2 5 reflected into the the circulator (as an input), the undesired signals are trans~erred to the third port of th circulator 23. The ornni antenna 30 interconnected to the third port of the circulator 23 presents a load for the traf~lc channel signals and a path for transmission of the 3 0 - si~nals.
The use of the circulator 23 and frequency selective cavity assemblies improves communication systems by reducin~ the cost and improvin~ the reliability and efficiency of such systems. The use of a ~-3 5 cornmon LPA reduces the cost of transmitters within such a system by reducing the parts required to build such as system and by utilizino the LPA to a higher capacity for a better efficiency. The use of a common 2l3fi4a3 LPA allows for a reduction in the size of such a system by concentrating power amplification to a single area.
The use of a common LPA further allows the dyn~m~c changin(J of system topologies (e.g, the reassignment of S transceiver from one service coverage area to another).
The many features and advanta,~es of this invention are apparent from the detailed specification and thus it is intended by the appended claims tO cover all such features and advanta,~es of the system which fall within the true spirit and scope of the invention.
Further, since numerous modifications and changes will readily occur to those skilled in the art (e.g., use within commercial transmission systems)~ it is not desired to limit the invention to the exact construction and operation illustrated and describe~d~ and accordin~ly all suitable modi~lcations and equivalents (e.g., orn~i-sector, sector-omni, ornni-omni, and sector-sector channel separators) may be resorted to, falling within the scope of the inventian.
?. O An omni-sector separator may be used, for instance, where a separated control channel is transmitted on an omni antenna and reflected traffic channels are transmitted from directional antennas. An omni-sector channel separator may also ~lnd usefulness 2 5 in -cases where geographic obstructions cause poor illumination of a service area from the central omni antenna, which can be remedied by a single channel sector antenna placed in close proximity and powered from the same LPA. An omni-sector channel separator 3 0 may further find usefulness in cases where geo~raphic cond;tions cause interfere;nce to other service areas on selected channels radiated from the central omni antenna by separating those channels and radiatin~
them from sector antennas into specific service areas. A
35 sector-sector channel separator may be useful where directional antenna for traffic and control do not coincide.
WO9S12477~ 2136~ PCTluS94/03007 h~
It is, of course~ to be understood that the present invention is, by no means, limited to the specific showin~ in the drawing, but also comprises any modification within the scope of the appended claims.
t .
: `
Claims (10)
1. An apparatus for separating spectrally diverse radio frequency signals comprising: means, within a signal transfer module, for transferring an input signal received at a first port of the signal transfer module to a second port of the signal transfer module; at least one frequency selective assembly interconnected with the second port of the signal transfer module, presenting a characteristic impedance to a desired signal of the input signal and reflecting other signals of the input signal to the second port of the frequency transfer module;
means, within the signal transfer module for transferring a reflected signal received at the second port of the signal transfer module to a third port of the signal transfer module.
means, within the signal transfer module for transferring a reflected signal received at the second port of the signal transfer module to a third port of the signal transfer module.
2. The apparatus as in claim 1 wherein the signal transfer module further comprises a radio frequency circulator.
3. The apparatus as in claim 1 wherein the at least one frequency selective assembly comprises a frequency selective cavity, resonant at a frequency of the desired signal, interconnected with the second port of the signal transfer module with a cable of a length substantially equal to one-quarter wavelength of the frequency of the desired signal.
4. An apparatus for separating a first radio channel and an at least second channel within a high power radio signal, such apparatus comprising: a circulator receiving the high power radio signal at a first port; and a frequency selective cavity, selective of the first frequency, interconnected with the circulator through a first terminal of the frequency selective cavity and a second port of the circulator, through a transmission line of a length substantially equal to one-quarter wavelength of a frequency of the first channel.
5. The apparatus as in claim 4 further comprising at least a second frequency selective cavity, selective of at least a second frequency, interconnected with the circulator through a first terminal of the at least second frequency selective cavity and the second port of the circulator, through a transmission line of a length substantially equal to one-quarter wavelength of a frequency of the at least second channel and with an at least third antenna through a second terminal of the at least second frequency selective cavity.
6. In a high power radio signal from a radio frequency transmitter producing a combined signal containing a signal of a first radio channel for transmission through a first antenna and at least a signal of a second radio channel for transmission through a second antenna, a method for separating the signals for transmission through respective antennas comprising the steps of: applying the combined signal to a circulator at a first port; outputting the combined signal to a first frequency selective cavity, selective of the first frequency, at a second port of the circulator through a conductor of a length substantially equal to one-quarter wavelength of a frequency of the first channel; coupling an output of the first frequency selective cavity to the first antenna; and transmitting the first channel through the first antenna.
7. The method as in claim 6 further including the step of outputting at a third port the portion of the combined signal received as an input at the second port and transmitting the portion of the combined signal from a second antenna interconnected with the third port of the circulator.
8. In a high power radio signal from a radio frequency transmitter producing a combined signal containing a signal of a first control channel for transmission through a first directional antenna and a signal of an at least a first traffic channel for transmission through an omni antenna, an apparatus for separating the first control channel from the at least first traffic channel comprising: a circulator receiving the combined signal at a first port; a frequency selective cavity, selective of the first control channel, interconnected with the circulator through a first terminal of the frequency selective cavity and a second port of the circulator, through a transmission line of a length substantially equal to one-quarter wavelength of a frequency of the first control channel and with the first antenna through a second terminal of the frequency selective cavity; and an interconnection with the omni antenna at a third port of the circulator.
9. The apparatus as in claim 8 further comprising at least a second frequency selective cavity, selective of at least a second control channel, interconnected with the circulator through a first terminal of the at least second frequency selective cavity and a second port of the circulator, through a transmission line of a length substantially equal to one-quarter wavelength of the at least second control channel and with an at least second directional antenna through a second terminal of the at least second frequency selective cavity.
10. The apparatus as in claim 8 wherein the radio frequency transmitter further comprises a base station in a cellular communication system.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5110193A | 1993-04-21 | 1993-04-21 | |
| US08/051,101 | 1993-04-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2136443A1 true CA2136443A1 (en) | 1994-10-27 |
Family
ID=21969350
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002136443A Abandoned CA2136443A1 (en) | 1993-04-21 | 1994-03-22 | Method and apparatus for separating channels from a radio frequency transmitter |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0660983A4 (en) |
| JP (1) | JPH07508391A (en) |
| KR (1) | KR950702355A (en) |
| CA (1) | CA2136443A1 (en) |
| WO (1) | WO1994024772A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2809551B1 (en) * | 2000-05-25 | 2002-07-19 | Bruker Sa | MULTI-FREQUENCY RF SIGNAL GENERATOR DEVICE |
| US7342508B2 (en) | 2003-12-26 | 2008-03-11 | Medtronic Minimed, Inc. | Telemetry system and method with variable parameters |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4128740A (en) * | 1977-02-14 | 1978-12-05 | Motorola, Inc. | Antenna array for a cellular RF communications system |
| US4661993A (en) * | 1984-10-12 | 1987-04-28 | At&T Company | Technique for improving radio system performance during fading |
| US4688259A (en) * | 1985-12-11 | 1987-08-18 | Ford Aerospace & Communications Corporation | Reconfigurable multiplexer |
| US4667172A (en) * | 1986-04-07 | 1987-05-19 | Motorola, Inc. | Ceramic transmitter combiner with variable electrical length tuning stub and coupling loop interface |
| US5048116A (en) * | 1989-05-24 | 1991-09-10 | Motorola, Inc. | Signal routing system |
-
1994
- 1994-03-22 CA CA002136443A patent/CA2136443A1/en not_active Abandoned
- 1994-03-22 WO PCT/US1994/003007 patent/WO1994024772A1/en not_active Application Discontinuation
- 1994-03-22 JP JP6523193A patent/JPH07508391A/en active Pending
- 1994-03-22 EP EP94913925A patent/EP0660983A4/en not_active Withdrawn
- 1994-12-21 KR KR1019940704671A patent/KR950702355A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| WO1994024772A1 (en) | 1994-10-27 |
| EP0660983A1 (en) | 1995-07-05 |
| EP0660983A4 (en) | 2000-09-13 |
| JPH07508391A (en) | 1995-09-14 |
| KR950702355A (en) | 1995-06-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |