CA2220781A1 - Millimeter wave transceiver for point-to-multipoint communications system - Google Patents
Millimeter wave transceiver for point-to-multipoint communications system Download PDFInfo
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Abstract
A directional millimeter wave transceiver for reception and transmission of digital data and direct broadcast (TV/radio) signals in a point-to-multipoint communications system. A polarized receiving antenna and an orthogonally polarized transmitting antenna receive and transmit, respectively, the millimeter wave signals. To provide electrical isolation between the different types of communications signals, received data signals are limited to a first frequency band which is separated by a second frequency band reserved for transmitted data signals from a third frequency band reserved for received direct broadcast signals.
Radio frequency circuitry converts the millimeter wave signals to and from intermediary frequency signals and coding/coding circuitry modulates and demodulates, and codes and decodes, the intermediary frequency signals for output from the transceiver to a local data network and input to the radio frequency circuitry. The antennas, radio frequency circuitry, and the coding/decoding circuitry are comprised in a separate sub-assembly. The antennas and circuit card assemblies are assembled within an external housing.
Radio frequency circuitry converts the millimeter wave signals to and from intermediary frequency signals and coding/coding circuitry modulates and demodulates, and codes and decodes, the intermediary frequency signals for output from the transceiver to a local data network and input to the radio frequency circuitry. The antennas, radio frequency circuitry, and the coding/decoding circuitry are comprised in a separate sub-assembly. The antennas and circuit card assemblies are assembled within an external housing.
Description
MILLIMETER WAVE TRANSCEIVER FOR POINT-TO-MULTIPOINT COMMUNICATIONS SYSTEM
Field of the Invention The invention relates to a low power, directional millimeter wave transceiver for use in a point-to-multipoint two-way communication system.
Backqround Millimeter wave transceivers for use in GHz frequency bands are known in association with a variety of radar applications such as those disclosed in U.S. patent Nos.
4,893,126, 5,201,065, 5,512,901 and 5,493,303.
Millimeter wave transceivers have, more recently, been disclosed for local reception and transmission of television/radio signals and digital data in point-to-multipoint communication systems. For example, U.S. patent No. 4,747,160 discloses a low power multifunction cellular television system in which a subscriber receiver locks to a master oscillator located at a cell node transmitter.
However, the transceiver taught by this patent is costly, complex and is not subject to compact construction because the space diversity provided therein between the reception and transmission antennas requires that those antennas be spaced a longitudinal distance from each other. Furthermore, the transceiver disclosed therein provides limited frequency diversity, through polarization of the reception and transmission functions only, and does not disclose any frequency planning for m;n;m;zing interference or cross-talk between distinct types of reception signals. Also, the subscriber receiver taught by this patent utilizes a manually tuned oscillator and the method of transmitting data is not disclosed.
Consequently, it is desirable to provide for a low cost, integrated-circuit millimeter wave transceiver utilizing frequency planning and having a compact construction including planar reception and transmission antennas and programmable computer-controlled local oscillators.
Summarv of the Invention In accordance with the invention there is provided a directional millimeter wave transceiver for reception and transmission of signals comprising digital data and/or broadcast television/radio signals in a point-to-multipoint communication system. A receiving antenna directionally receives millimeter wave signals having a first predetermined polarity and a transmitting antenna coplanar therewith directionally transmits millimeter wave signals having a second predetermined polarity which is orthogonal to the first polarity. Digital data signals are received by the receiving antenna within a first predetermined frequency band, digital data is transmitted by the transmitting antenna within a second predetermined frequency band and broadcast television/radio signals are received by the receiving antenna within a third predetermined frequency band whereby the second frequency band is between the first and third frequency bands.
Radio frequency circuitry is provided to convert the millimeter wave signals to and from intermediary frequency signals whereby the radio frequency circuitry receives the broadcast television/radio and digital data signals from the receiving antenna, converts the received signals to intermediary frequency signals and separately outputs the radio frequency television/radio and data signals. In addition, the radio frequency circuitry receives intermediary frequency data signals, converts the intermediary frequency data signals to millimeter wave data signals and outputs the millimeter wave data signals to the transmitting antenna.
Coding/decoding circuitry is provided for modulating/demodulating and coding/decoding the intermediary data signals to condition the intermediary signals for output from the transceiver to a local data network and for input to the radio frequency circuitry.
The receiving and transmitting antennas 80, 90 are comprised of separate parabolic antennas. The radio frequency circuitry is comprised in a single circuit card 110 and the coding/decoding circuitry is also comprised in a single circuit card 240. The antennas and circuit cards are assembled together within an external housing 275.
The radio frequency circuitry preferably comprises a high frequency oscillator circuit comprising a low frequency synthesizer and multiplication circuitry for multiplying the low frequency synthesizer to a selected millimeter wave frequency. The radio frequency circuitry also includes mixers, an input of which is the output of the high frequency oscillator circuit, and phase locked loop circuitry. The coding/decoding circuitry preferably comprises microprocessor means for permitting local control of the operating frequency of the transceiver by providing control to the high frequency oscillator circuit and the phase locked loop circuitry. The coding/decoding circuitry also preferably comprises a reference signal generator for input to the high frequency oscillator circuit and the phase locked loop circuitry, and DC
power supply circuitry for use by the radio frequency circuitry and the coding/decoding circuitry.
Brief Description of the Drawinqs Figure 1 is a representational layout of a point-to-multipoint two-way communication system utilizing a transceiver according to the invention at the subscriber end thereof;
Figure 2 is a representational layout of a typical subscriber end in the communication system shown in Figure 1;
Figure 3 is a general block diagram representation of the components of the transceiver according to the invention;
Figure 4 is a graphical representation of the frequency plan of the transceiver according to the invention;
In Figure 5, Figs. 5(A) and 5(B) are block diagram schematic representations of the preferred polarized parabolic reflector receiving and transmitting antennas, resp., and Figs. 5(C) and 5(D) are block diagram schematic representations of alternative polarized, planar, printed patch receiving and transmitting antenna arrays, resp.;
Figure 6 is a block diagram of the radio frequency circuitry of the preferred embodiment of the transceiver according to the invention;
Figure 7 is a block diagram of the coding/decoding circuitry of the preferred embodiment of the transceiver according to the invention;
Figure 8 is a diagrammatic break-out assembly drawing showing the assembly of the subassembly components of the preferred embodiment of the transceiver according to the invention; and, Figure 9 is a perspective view of the assembled transceiver according to the preferred embodiment of the invention.
Detailed DescriPtion of a Preferred Embodiment Referring to Figure 1, the directional transceiver 10 of the invention is used at the subscriber end of a point-to-multipoint communications system as illustrated, the commlln;cations system comprising a head-end 20, a plurality of alternately polarized hub stations 30 and a plurality of subscribers 40 within each area covered by a hub station 30.
The head-end 20 of the communications system includes the usual broadcast equipment plus head-end-to-hub transmission equipment for transmitting both digital data (representing the data link function of the system) and analog television/radio signals (representing the direct broadcast, "DB", function of the system) to the hub stations 30. At the head-end the television/radio broadcast signals are collected from the various sources of those signals and data signals are collected from various digital data sources such as the Internet.
Preferably, as illustrated, the communications services provided include various data links, such as to the Internet and the many services providing access to various databases world-wide, and a broad scope of television/radio broadcast channels. Thus, business subscribers utilizing the data links and home subscribers using either or both of the data links and television/radio channels may benefit from the com~lnications system.
The hub stations 30 are omni-directional transceivers which transmit and receive the communications signals at approximately 28 GHz. By reason of regulatory safety standards which govern the maximum permissible power levels for millimeter wave transmissions, the transmission/reception radii covered by a hub station transceiver 30 or subscribe transceiver 10 is about 5 Km. The maximum power output transmitted by the subscriber transceiver 10 is lOmW. To obtain effective coverage over the area of a city (marked by "A" in Figure 1) a plurality of hub transceivers 30 are positioned so that their areas of coverage overlap with the areas of adjacent transceivers 30 and the polarities of the transmissions/receptions by adjacent hub transceivers 30 are orthogonal as illustrated. Because the overlapping signals in any one area are orthogonal a subscriber transceiver 10 in such area is selected to have polarities matching those of the hub transceiver 30 providing the strongest signals at such location so as to block out the weaker orthogonal signals of the overlapping hub transceiver 30.
At the subscriber end 40 the local transceiver 10 receives digital data signals and analog television/radio signals on the millimeter wave carrier frequency transmitted by the hub transceiver 30 to which it is directionally coupled. The transceiver 10 transforms these signals back into their digital data and analog television/radio components for output from the transceiver 10 to a local data network 50 (which is preferably a Tl interface/switch or an Ethernet interface) and television set-top receiver unit 60, respectively, as illustrated by Figure 2. Two-way data communications are provided by the transceiver 10 which also receives digital data signals from the local data network 50, transforms them into millimeter wave signals and transmits those signals to the hub transceiver 30 associated with the local transceiver 10.
Referring to Figure 3 a general block diagram representation of the components of the transceiver 10 is provided. Directional receiving antenna 80 and transmitting antenna 90 are orthogonally polarized so as to provide electrical isolation between the two antennas. In the embodiment shown by Figure 3 the receiving antenna 80 is vertically polarized whereas the transmitting antenna 90 is horizontally polarized. A transceiver 10 configured accordingly would, therefore, be located in an area covered by a hub transceiver 30 having a vertically polarized transmitting antenna and horizontally polarized receiving antenna. Each of the antennas 80, 90 are highly directional and must be positioned in line with their associated hub transceiver 30 (or a repeater positioned therebetween for directional modification/amplification purposes). This directionality of the antennas 80, 90 assists in the electrical isolation of the antennas 80, 90 and of individual subscriber transceivers 10 located in the subscriber end 40 of the communications system.
The receiving antenna 80 and the transmitting antenna 90 are parabolic reflector antennas with LEXON (a trademark) windows as illustrated in Figures 5(a) and 5(b), the receiving antenna shown in Figure 5(a) being an antenna with a linearly vertically polarized feed element and the transmitting antenna shown in Figure 5(b) having a linearly horizontally polarized feed element. Optionally, the antennas could instead be planar, printed patch antenna arrays as illustrated in Figures S(C) and 5(D) wherein Figure 5(C) shows a receiving array of linearly vertically polarized patch antenna elements and Figure 5(D) shows a transmitting array of linearly horizontally polarized patch antenna elements. The antennas provide highly focused beams whereby very directional reception and transmission is obtained while simultaneously rejecting undesired signals outside of the focused beams. The preferred parabolic reflector antennas are produced by InfoMagnetics Corporation and identified as Part No. 27.85R-30. They allow for a high degree of electrical isolation between the receiving and transmitting antennas, typically in the order of 20 - 30 dB at 28GHz. This isolation allows the transmit signal, which "leaks" into the receive stream, to be suppressed sufficiently so as not to cause distortion of the signals being received and, thereby, allows for simultaneous reception and transmission by the antennas 80,90.
Additional electrical isolation between the different types of communication signals is provided by the frequency plan employed by the transceiver 10 as illustrated in Figure 4. As shown, the operating frequency band for the transmission and reception of signals within the commlln;cations system is about 1 GHz (marked by the dotted lines in Figure 4) and suitable guard bands "C" and "D" at the upper and lower limits of the operating band are provided to avoid "leakage" or cross-talk from outside the allocated operating frequency band. Within the operating band a frequency band 140 of about 200 MHz is reserved for digital data signals and a band 160 of 500 MHz is reserved for analog television/radio signals, with a suitable guard band "E" of 240 MHz provided between the data signal and the television/radio signal bands. Within the digital data signal band 140 a further two distinct frequency bands 142, 144, separated by a guard band "F", are allocated. The first data signal band 142 is reserved for received data signals and the second data signal band 144 is reserved for data signals to be transmitted by the transceiver 10 such that the frequency band 142 allocated for the reception of digital data is separated from the frequency band 160 allocated for the reception of television/radio signals by the band 144 allocated for transmission of data signals. The reception functions for digital data and analog signals are thereby electrically isolated by the frequency bandwidth allocated for transmission of digital data which is itself electrically isolated from both reception functions due to the orthogonal polarities as between the reception and transmission functions. These isolating functions allow for the simultaneous reception and transmission of both digital data signals and analog television/radio signals without need to separate the transmit and receive signals at the RF input frequency.
The radio frequency (RF) circuitry 110 shown by Figure 6 converts the millimeter wave signals (i.e. the RF within the operating frequency band around 28 GHz) to and from intermediary frequency (IF) signals using synthesized local oscillators. The RF circuitry 110 comprises a receive portion 150, a transmit portion 152 and a high frequency local oscillator portion 154 providing input to microwave integrated circuit mixers 156, 158 of the receive and transmit portions 150, 152, respectively. The high frequency local oscillator 154 uses a low frequency synthesizer which is multiplied to a high frequency band around 26.8 Ghz. The low frequency generated by the phase locked loop 160 is amplified by two amplifiers 198. The required harmonic of this signal is extracted by a comb generator 208. A base band filter 206 eliminates unwanted signals and the resultant Ka-band signal is amplified using two monolithic power amplifiers 204 and is divided between the receive portion 150 and the transmit portion 152 using a power divider 202.
The receive portion 150 receives signals from antenna 80, filters the required signals with filter 180, amplifies the resultant signal with two monolithic low noise amplifiers 182 and then down converts the signal to intermediary frequencies ~490 MHz - 1,450 MHz) using a microwave integrated mixer circuit 156 and the Ka-band signal provided by the high frequency local oscillator portion 154. The mixer 156 includes an image notch filter for image suppression in the down conversion. Intermediary frequencies above 1,450 MHz are filtered out by a surface mounted IF band pass filter 186 and amplified 188. A surface mounted power "divider" 190 divides the signal into two paths.
The receive portion 150 provides two output signals, one being an IF television/radio signal (950-1450 MHZ) which is typically (but not necessarily) an analog signal and is fed to a set-top television receiver 60 and the other being a 70MHz IF output comprising digital data which is fed to the coding/decoding circuitry provided by a power supply/coder-decoder circuit card 240. The transmit portion 152 receives modulated, coded IF digital data signals from the coding/decoding circuitry 240 and converts the IF signals to RF (millimeter wave) data signals for output to the transmit antenna 90. Local control at the transceiver 10 is provided to the high frequency local oscillator 154 and the phase-locked loop circuits 160, 162 and 164 of the RF circuitry 110 by a microprocessor 170 having frequency settings for user selection to provide such local control. Particulars of the individual block elements of Figure 6 are provided below under Table 6.1 T~bk 6.1-Rad;OFI~. r~ C-~ ~ CL . OfF;gU~ 6 Referenoe No. Name SD~fic-~ - tDea~ Vendor (if ~llDliC '~) 156 Mixer* Do... ~ t~_lb the incoming Ka-band signals to~ ~ signals 158 Mixer* U~o.. ~_ b the int~ l;at~ signals to Ka-band 160 Low Band Phase Serial input phase-locked-loop ~ ' ~ with Fujitsu and Z-comm Locked Loop** a .~.~ from 10 MHz crystal os~ ll ~ -162, Phase Locked Loop** Serial input phase-locked-loop a~llthc~er Fujitsu 180 RF Band Pass Filter* Eliminates r,., - outside the band of interest 182 2-Stage Low Noise Low noise ~ r~ with a noise figure of 2.8 dB Alpha Amplifier*** Tr' ~~
184 Image Notch Filter* A notch filter to suppress image L~, ~ by 15 dB
186 IF Low Pass Filterr** Low pass filter with cut offfi~ue"~ at the edge LarkF~
of the i. ~ fi~ue~l~ band 188 IF Amplifier ** Amplifies the ~ ~ - ' ~ signals to match input Mini Circuits level ~u,,~ to TV set top box 190 Power Divider** Divides the ~ ~t ~ - y signals into two paths Mini Circuits 192 T ~ from T ~ with lumped elements 50 to 75 o}uns**
194 Mixer** Do.... ,~ll~el~ the ~ ~ ~ signals to 70 MH~ Mini Circuits 196 70MHz Surface Band pass filter with oenter fi-~t .~ at 70 MHz Sawtek Acoustic Wave Filter** to provide istolation between adjaoent cham els 198 ~ FET ~ , 'ifirr used to amplify low phase-locked- Celeritek loop output 200, Voltage Controlled Oscillator in low r,. tt ~ phase-locked-loop Z-Comm 218 o~ill- t~t~
202 Power Divider* In-phaae design, insertion loss is 3 dB +/- 1 dB
T~ble 6.1~ d) Referenoe No. Name S~ific ~finn~De~ io~ Vendor (if e) 204 Two Stage Dnver ~ , ' to boost up the Ka~and local Alpha Amplifier*** o~ill signal 206 Bandpass Filter* Filters the local os~ signal 208 Comb Gi~ Extracts the 13th 1 1 - of the low band Herotek phase-locked signal 210 Power Aml~liliel~t~Amplifies the signal to be ll_ ~1 Alpha ;PS
212 Low Noise Amplifies the signal to be i ' Alpha ~0~l- -- ' . i~s Alllpl~ t 214 Notch Filter* To suppress the LO signal from b~ r by - 30 dB notch ~ LO ~
216 Phase M- ~I la~ A .. - ~ phase shin keying - ' ' Fujitsu *Mic,u.._.e ~,, ~ ~circuit **Surfaoe mount .
***~ m u.. a~ circuit The coding/decoding circuitry 240 shown by Figure 7 modulates and demodulates, and codes and decodes, the local data signals to be transmitted by the transceiver 10 and the IF data signals output from the radio frequency circuitry 110 and thereby conditions those signals for input to the radio frequency circuitry and for output from the transceiver 10 to a local data network, respectively. This circuitry includes a microprocessor 170 which provides local control over various selectable parameters including the operating frequency of the transceiver 10 (via control over the high frequency local oscillator and the phase locked loop circuits of the radio frequency circuitry 110). A lOMHz reference oscillator circuit 220 generates a lOMHz reference signal used by components of the RF and coding/decoding circuitry 110, 240 as illustrated. An in-phase/quadrature (I/Q) demodulator 225 separates the digital data output signal received from the RF
circuitry 110 into quadrature modulated signals and in-phase modulated signals. Phase modulation/demodulation coder/decoder circuitry 228 receives the quadrature modulated signals and in-phase modulated signals from the I/Q
demodulator 225 and converts them to digital data signals which are input to a network interface 234 for output to a T1 interface/switch of the local data network 50. The phase modulation/demodulation coder/decoder circuitry 228 also receives locally generated digital data signals from the network interface (received from a T1 interface/switch of a local data network) and converts those signals to quadrature modulated signals and in-phase modulated signals for output to the RF circuitry 110 (i.e. for input to the phase modulator 216). The symbol clock required for encoding is generated by the phase modulation/demodulation coder/decoder 228. The low and high data is generated by decision circuitry 230. A
digital phase-locked-loop is utilized in clock recovery circuitry 232. A DC power supply unit 236 conditions and sequences all DC power required by the RF and coding/decoding circuitry 110, 240. An external AC-to-DC wall adaptor 120 provides DC power to supply unit 236.
The particulars of the individual block elements of Figure 7 are provided below under Table 7.1.
Table 7.1 - Po~ver Supply/CDd D~ ~ o d Circuit Card Cl . of Figure 7 ReferenoeNo. Name S~fic~tion'D~-i t;--- Vendor(if~r~l ''~) 170 Mi~.-ul~u~u~ Reoeives li. . ~ setting input for control Philips /
S1 - ' --of phase-locked-loop circuits 220 lOMHz O~ill Referenoe signal for RF circuitly Circuit 225 In-phase/Q ~ c Den~od ' 70MHz data signal output from RF Harris Corp.
demodulator circuitry 228 PhaseIn~ ' ~--' Decodingand~ ~ g of,l,~ andin-phase Altera d-~ coder/ o ~ - - of data in field programmable gate decoder array (FPGA) 230 Decision Circuitly G~ - low and high data 232 Clock Recovery Recovers the clock from incoming Circuitry in-phase and; ' ti signals 234 Network Interface I r digital data signals between Tl ~ e~rx/ Lucent T~ - ~'~
Unit switch and phase - ~ -J, - ~ ~ ~ coder/ (for Ethernetinter-decoder (optional interface - F - t) face - National Semi-236 DC Supply Unit Cr- ~ ' ~ and . ~ all DC power required by RF and coding/dec~~ v circuitry As indicated by the dotted lines "B" in Figure 3 and the assembly diagram, Figure 8, the antennas 80 and 90 are attached to a single frame (the housing lid) 275 with the associated outputs connected to the RF circuit card 110 at the indicated connectors with low loss cables. The top surface of the card 110 is covered with polytetrafluroethylene, a product sold under the trademark DUROID being used for this. The RF
circuit 110 includes MMIC sub-assembly 100 which together combine conventional microwave integrated circuitry, surface mount components and monolithic microwave integrated circuitry (MMIC) as identified in table 6.1 herein.
The coding/decoding circuitry 110 is realized as a surface mount circuit card 250 and is bonded directly to the back of the RF circuit card 110 as illustrated by Figure 8.
The RF circuit card 110 is attached to an RF cavity 260 as shown. A base 270 and lid 275 provide the housing for the transceiver 10 to which a bracket 280 is attached for mounting the antenna in position for use by a subscriber. Input/output cables 290 of the transceiver 10 are provided for connection to the local data network 50 and television set-top receiver 60.
The preferred embodiment described herein is provided as a specific example of the circuitry of the invention and is not intended to limit the scope or definition of the invention which is defined by the appended claims.
Field of the Invention The invention relates to a low power, directional millimeter wave transceiver for use in a point-to-multipoint two-way communication system.
Backqround Millimeter wave transceivers for use in GHz frequency bands are known in association with a variety of radar applications such as those disclosed in U.S. patent Nos.
4,893,126, 5,201,065, 5,512,901 and 5,493,303.
Millimeter wave transceivers have, more recently, been disclosed for local reception and transmission of television/radio signals and digital data in point-to-multipoint communication systems. For example, U.S. patent No. 4,747,160 discloses a low power multifunction cellular television system in which a subscriber receiver locks to a master oscillator located at a cell node transmitter.
However, the transceiver taught by this patent is costly, complex and is not subject to compact construction because the space diversity provided therein between the reception and transmission antennas requires that those antennas be spaced a longitudinal distance from each other. Furthermore, the transceiver disclosed therein provides limited frequency diversity, through polarization of the reception and transmission functions only, and does not disclose any frequency planning for m;n;m;zing interference or cross-talk between distinct types of reception signals. Also, the subscriber receiver taught by this patent utilizes a manually tuned oscillator and the method of transmitting data is not disclosed.
Consequently, it is desirable to provide for a low cost, integrated-circuit millimeter wave transceiver utilizing frequency planning and having a compact construction including planar reception and transmission antennas and programmable computer-controlled local oscillators.
Summarv of the Invention In accordance with the invention there is provided a directional millimeter wave transceiver for reception and transmission of signals comprising digital data and/or broadcast television/radio signals in a point-to-multipoint communication system. A receiving antenna directionally receives millimeter wave signals having a first predetermined polarity and a transmitting antenna coplanar therewith directionally transmits millimeter wave signals having a second predetermined polarity which is orthogonal to the first polarity. Digital data signals are received by the receiving antenna within a first predetermined frequency band, digital data is transmitted by the transmitting antenna within a second predetermined frequency band and broadcast television/radio signals are received by the receiving antenna within a third predetermined frequency band whereby the second frequency band is between the first and third frequency bands.
Radio frequency circuitry is provided to convert the millimeter wave signals to and from intermediary frequency signals whereby the radio frequency circuitry receives the broadcast television/radio and digital data signals from the receiving antenna, converts the received signals to intermediary frequency signals and separately outputs the radio frequency television/radio and data signals. In addition, the radio frequency circuitry receives intermediary frequency data signals, converts the intermediary frequency data signals to millimeter wave data signals and outputs the millimeter wave data signals to the transmitting antenna.
Coding/decoding circuitry is provided for modulating/demodulating and coding/decoding the intermediary data signals to condition the intermediary signals for output from the transceiver to a local data network and for input to the radio frequency circuitry.
The receiving and transmitting antennas 80, 90 are comprised of separate parabolic antennas. The radio frequency circuitry is comprised in a single circuit card 110 and the coding/decoding circuitry is also comprised in a single circuit card 240. The antennas and circuit cards are assembled together within an external housing 275.
The radio frequency circuitry preferably comprises a high frequency oscillator circuit comprising a low frequency synthesizer and multiplication circuitry for multiplying the low frequency synthesizer to a selected millimeter wave frequency. The radio frequency circuitry also includes mixers, an input of which is the output of the high frequency oscillator circuit, and phase locked loop circuitry. The coding/decoding circuitry preferably comprises microprocessor means for permitting local control of the operating frequency of the transceiver by providing control to the high frequency oscillator circuit and the phase locked loop circuitry. The coding/decoding circuitry also preferably comprises a reference signal generator for input to the high frequency oscillator circuit and the phase locked loop circuitry, and DC
power supply circuitry for use by the radio frequency circuitry and the coding/decoding circuitry.
Brief Description of the Drawinqs Figure 1 is a representational layout of a point-to-multipoint two-way communication system utilizing a transceiver according to the invention at the subscriber end thereof;
Figure 2 is a representational layout of a typical subscriber end in the communication system shown in Figure 1;
Figure 3 is a general block diagram representation of the components of the transceiver according to the invention;
Figure 4 is a graphical representation of the frequency plan of the transceiver according to the invention;
In Figure 5, Figs. 5(A) and 5(B) are block diagram schematic representations of the preferred polarized parabolic reflector receiving and transmitting antennas, resp., and Figs. 5(C) and 5(D) are block diagram schematic representations of alternative polarized, planar, printed patch receiving and transmitting antenna arrays, resp.;
Figure 6 is a block diagram of the radio frequency circuitry of the preferred embodiment of the transceiver according to the invention;
Figure 7 is a block diagram of the coding/decoding circuitry of the preferred embodiment of the transceiver according to the invention;
Figure 8 is a diagrammatic break-out assembly drawing showing the assembly of the subassembly components of the preferred embodiment of the transceiver according to the invention; and, Figure 9 is a perspective view of the assembled transceiver according to the preferred embodiment of the invention.
Detailed DescriPtion of a Preferred Embodiment Referring to Figure 1, the directional transceiver 10 of the invention is used at the subscriber end of a point-to-multipoint communications system as illustrated, the commlln;cations system comprising a head-end 20, a plurality of alternately polarized hub stations 30 and a plurality of subscribers 40 within each area covered by a hub station 30.
The head-end 20 of the communications system includes the usual broadcast equipment plus head-end-to-hub transmission equipment for transmitting both digital data (representing the data link function of the system) and analog television/radio signals (representing the direct broadcast, "DB", function of the system) to the hub stations 30. At the head-end the television/radio broadcast signals are collected from the various sources of those signals and data signals are collected from various digital data sources such as the Internet.
Preferably, as illustrated, the communications services provided include various data links, such as to the Internet and the many services providing access to various databases world-wide, and a broad scope of television/radio broadcast channels. Thus, business subscribers utilizing the data links and home subscribers using either or both of the data links and television/radio channels may benefit from the com~lnications system.
The hub stations 30 are omni-directional transceivers which transmit and receive the communications signals at approximately 28 GHz. By reason of regulatory safety standards which govern the maximum permissible power levels for millimeter wave transmissions, the transmission/reception radii covered by a hub station transceiver 30 or subscribe transceiver 10 is about 5 Km. The maximum power output transmitted by the subscriber transceiver 10 is lOmW. To obtain effective coverage over the area of a city (marked by "A" in Figure 1) a plurality of hub transceivers 30 are positioned so that their areas of coverage overlap with the areas of adjacent transceivers 30 and the polarities of the transmissions/receptions by adjacent hub transceivers 30 are orthogonal as illustrated. Because the overlapping signals in any one area are orthogonal a subscriber transceiver 10 in such area is selected to have polarities matching those of the hub transceiver 30 providing the strongest signals at such location so as to block out the weaker orthogonal signals of the overlapping hub transceiver 30.
At the subscriber end 40 the local transceiver 10 receives digital data signals and analog television/radio signals on the millimeter wave carrier frequency transmitted by the hub transceiver 30 to which it is directionally coupled. The transceiver 10 transforms these signals back into their digital data and analog television/radio components for output from the transceiver 10 to a local data network 50 (which is preferably a Tl interface/switch or an Ethernet interface) and television set-top receiver unit 60, respectively, as illustrated by Figure 2. Two-way data communications are provided by the transceiver 10 which also receives digital data signals from the local data network 50, transforms them into millimeter wave signals and transmits those signals to the hub transceiver 30 associated with the local transceiver 10.
Referring to Figure 3 a general block diagram representation of the components of the transceiver 10 is provided. Directional receiving antenna 80 and transmitting antenna 90 are orthogonally polarized so as to provide electrical isolation between the two antennas. In the embodiment shown by Figure 3 the receiving antenna 80 is vertically polarized whereas the transmitting antenna 90 is horizontally polarized. A transceiver 10 configured accordingly would, therefore, be located in an area covered by a hub transceiver 30 having a vertically polarized transmitting antenna and horizontally polarized receiving antenna. Each of the antennas 80, 90 are highly directional and must be positioned in line with their associated hub transceiver 30 (or a repeater positioned therebetween for directional modification/amplification purposes). This directionality of the antennas 80, 90 assists in the electrical isolation of the antennas 80, 90 and of individual subscriber transceivers 10 located in the subscriber end 40 of the communications system.
The receiving antenna 80 and the transmitting antenna 90 are parabolic reflector antennas with LEXON (a trademark) windows as illustrated in Figures 5(a) and 5(b), the receiving antenna shown in Figure 5(a) being an antenna with a linearly vertically polarized feed element and the transmitting antenna shown in Figure 5(b) having a linearly horizontally polarized feed element. Optionally, the antennas could instead be planar, printed patch antenna arrays as illustrated in Figures S(C) and 5(D) wherein Figure 5(C) shows a receiving array of linearly vertically polarized patch antenna elements and Figure 5(D) shows a transmitting array of linearly horizontally polarized patch antenna elements. The antennas provide highly focused beams whereby very directional reception and transmission is obtained while simultaneously rejecting undesired signals outside of the focused beams. The preferred parabolic reflector antennas are produced by InfoMagnetics Corporation and identified as Part No. 27.85R-30. They allow for a high degree of electrical isolation between the receiving and transmitting antennas, typically in the order of 20 - 30 dB at 28GHz. This isolation allows the transmit signal, which "leaks" into the receive stream, to be suppressed sufficiently so as not to cause distortion of the signals being received and, thereby, allows for simultaneous reception and transmission by the antennas 80,90.
Additional electrical isolation between the different types of communication signals is provided by the frequency plan employed by the transceiver 10 as illustrated in Figure 4. As shown, the operating frequency band for the transmission and reception of signals within the commlln;cations system is about 1 GHz (marked by the dotted lines in Figure 4) and suitable guard bands "C" and "D" at the upper and lower limits of the operating band are provided to avoid "leakage" or cross-talk from outside the allocated operating frequency band. Within the operating band a frequency band 140 of about 200 MHz is reserved for digital data signals and a band 160 of 500 MHz is reserved for analog television/radio signals, with a suitable guard band "E" of 240 MHz provided between the data signal and the television/radio signal bands. Within the digital data signal band 140 a further two distinct frequency bands 142, 144, separated by a guard band "F", are allocated. The first data signal band 142 is reserved for received data signals and the second data signal band 144 is reserved for data signals to be transmitted by the transceiver 10 such that the frequency band 142 allocated for the reception of digital data is separated from the frequency band 160 allocated for the reception of television/radio signals by the band 144 allocated for transmission of data signals. The reception functions for digital data and analog signals are thereby electrically isolated by the frequency bandwidth allocated for transmission of digital data which is itself electrically isolated from both reception functions due to the orthogonal polarities as between the reception and transmission functions. These isolating functions allow for the simultaneous reception and transmission of both digital data signals and analog television/radio signals without need to separate the transmit and receive signals at the RF input frequency.
The radio frequency (RF) circuitry 110 shown by Figure 6 converts the millimeter wave signals (i.e. the RF within the operating frequency band around 28 GHz) to and from intermediary frequency (IF) signals using synthesized local oscillators. The RF circuitry 110 comprises a receive portion 150, a transmit portion 152 and a high frequency local oscillator portion 154 providing input to microwave integrated circuit mixers 156, 158 of the receive and transmit portions 150, 152, respectively. The high frequency local oscillator 154 uses a low frequency synthesizer which is multiplied to a high frequency band around 26.8 Ghz. The low frequency generated by the phase locked loop 160 is amplified by two amplifiers 198. The required harmonic of this signal is extracted by a comb generator 208. A base band filter 206 eliminates unwanted signals and the resultant Ka-band signal is amplified using two monolithic power amplifiers 204 and is divided between the receive portion 150 and the transmit portion 152 using a power divider 202.
The receive portion 150 receives signals from antenna 80, filters the required signals with filter 180, amplifies the resultant signal with two monolithic low noise amplifiers 182 and then down converts the signal to intermediary frequencies ~490 MHz - 1,450 MHz) using a microwave integrated mixer circuit 156 and the Ka-band signal provided by the high frequency local oscillator portion 154. The mixer 156 includes an image notch filter for image suppression in the down conversion. Intermediary frequencies above 1,450 MHz are filtered out by a surface mounted IF band pass filter 186 and amplified 188. A surface mounted power "divider" 190 divides the signal into two paths.
The receive portion 150 provides two output signals, one being an IF television/radio signal (950-1450 MHZ) which is typically (but not necessarily) an analog signal and is fed to a set-top television receiver 60 and the other being a 70MHz IF output comprising digital data which is fed to the coding/decoding circuitry provided by a power supply/coder-decoder circuit card 240. The transmit portion 152 receives modulated, coded IF digital data signals from the coding/decoding circuitry 240 and converts the IF signals to RF (millimeter wave) data signals for output to the transmit antenna 90. Local control at the transceiver 10 is provided to the high frequency local oscillator 154 and the phase-locked loop circuits 160, 162 and 164 of the RF circuitry 110 by a microprocessor 170 having frequency settings for user selection to provide such local control. Particulars of the individual block elements of Figure 6 are provided below under Table 6.1 T~bk 6.1-Rad;OFI~. r~ C-~ ~ CL . OfF;gU~ 6 Referenoe No. Name SD~fic-~ - tDea~ Vendor (if ~llDliC '~) 156 Mixer* Do... ~ t~_lb the incoming Ka-band signals to~ ~ signals 158 Mixer* U~o.. ~_ b the int~ l;at~ signals to Ka-band 160 Low Band Phase Serial input phase-locked-loop ~ ' ~ with Fujitsu and Z-comm Locked Loop** a .~.~ from 10 MHz crystal os~ ll ~ -162, Phase Locked Loop** Serial input phase-locked-loop a~llthc~er Fujitsu 180 RF Band Pass Filter* Eliminates r,., - outside the band of interest 182 2-Stage Low Noise Low noise ~ r~ with a noise figure of 2.8 dB Alpha Amplifier*** Tr' ~~
184 Image Notch Filter* A notch filter to suppress image L~, ~ by 15 dB
186 IF Low Pass Filterr** Low pass filter with cut offfi~ue"~ at the edge LarkF~
of the i. ~ fi~ue~l~ band 188 IF Amplifier ** Amplifies the ~ ~ - ' ~ signals to match input Mini Circuits level ~u,,~ to TV set top box 190 Power Divider** Divides the ~ ~t ~ - y signals into two paths Mini Circuits 192 T ~ from T ~ with lumped elements 50 to 75 o}uns**
194 Mixer** Do.... ,~ll~el~ the ~ ~ ~ signals to 70 MH~ Mini Circuits 196 70MHz Surface Band pass filter with oenter fi-~t .~ at 70 MHz Sawtek Acoustic Wave Filter** to provide istolation between adjaoent cham els 198 ~ FET ~ , 'ifirr used to amplify low phase-locked- Celeritek loop output 200, Voltage Controlled Oscillator in low r,. tt ~ phase-locked-loop Z-Comm 218 o~ill- t~t~
202 Power Divider* In-phaae design, insertion loss is 3 dB +/- 1 dB
T~ble 6.1~ d) Referenoe No. Name S~ific ~finn~De~ io~ Vendor (if e) 204 Two Stage Dnver ~ , ' to boost up the Ka~and local Alpha Amplifier*** o~ill signal 206 Bandpass Filter* Filters the local os~ signal 208 Comb Gi~ Extracts the 13th 1 1 - of the low band Herotek phase-locked signal 210 Power Aml~liliel~t~Amplifies the signal to be ll_ ~1 Alpha ;PS
212 Low Noise Amplifies the signal to be i ' Alpha ~0~l- -- ' . i~s Alllpl~ t 214 Notch Filter* To suppress the LO signal from b~ r by - 30 dB notch ~ LO ~
216 Phase M- ~I la~ A .. - ~ phase shin keying - ' ' Fujitsu *Mic,u.._.e ~,, ~ ~circuit **Surfaoe mount .
***~ m u.. a~ circuit The coding/decoding circuitry 240 shown by Figure 7 modulates and demodulates, and codes and decodes, the local data signals to be transmitted by the transceiver 10 and the IF data signals output from the radio frequency circuitry 110 and thereby conditions those signals for input to the radio frequency circuitry and for output from the transceiver 10 to a local data network, respectively. This circuitry includes a microprocessor 170 which provides local control over various selectable parameters including the operating frequency of the transceiver 10 (via control over the high frequency local oscillator and the phase locked loop circuits of the radio frequency circuitry 110). A lOMHz reference oscillator circuit 220 generates a lOMHz reference signal used by components of the RF and coding/decoding circuitry 110, 240 as illustrated. An in-phase/quadrature (I/Q) demodulator 225 separates the digital data output signal received from the RF
circuitry 110 into quadrature modulated signals and in-phase modulated signals. Phase modulation/demodulation coder/decoder circuitry 228 receives the quadrature modulated signals and in-phase modulated signals from the I/Q
demodulator 225 and converts them to digital data signals which are input to a network interface 234 for output to a T1 interface/switch of the local data network 50. The phase modulation/demodulation coder/decoder circuitry 228 also receives locally generated digital data signals from the network interface (received from a T1 interface/switch of a local data network) and converts those signals to quadrature modulated signals and in-phase modulated signals for output to the RF circuitry 110 (i.e. for input to the phase modulator 216). The symbol clock required for encoding is generated by the phase modulation/demodulation coder/decoder 228. The low and high data is generated by decision circuitry 230. A
digital phase-locked-loop is utilized in clock recovery circuitry 232. A DC power supply unit 236 conditions and sequences all DC power required by the RF and coding/decoding circuitry 110, 240. An external AC-to-DC wall adaptor 120 provides DC power to supply unit 236.
The particulars of the individual block elements of Figure 7 are provided below under Table 7.1.
Table 7.1 - Po~ver Supply/CDd D~ ~ o d Circuit Card Cl . of Figure 7 ReferenoeNo. Name S~fic~tion'D~-i t;--- Vendor(if~r~l ''~) 170 Mi~.-ul~u~u~ Reoeives li. . ~ setting input for control Philips /
S1 - ' --of phase-locked-loop circuits 220 lOMHz O~ill Referenoe signal for RF circuitly Circuit 225 In-phase/Q ~ c Den~od ' 70MHz data signal output from RF Harris Corp.
demodulator circuitry 228 PhaseIn~ ' ~--' Decodingand~ ~ g of,l,~ andin-phase Altera d-~ coder/ o ~ - - of data in field programmable gate decoder array (FPGA) 230 Decision Circuitly G~ - low and high data 232 Clock Recovery Recovers the clock from incoming Circuitry in-phase and; ' ti signals 234 Network Interface I r digital data signals between Tl ~ e~rx/ Lucent T~ - ~'~
Unit switch and phase - ~ -J, - ~ ~ ~ coder/ (for Ethernetinter-decoder (optional interface - F - t) face - National Semi-236 DC Supply Unit Cr- ~ ' ~ and . ~ all DC power required by RF and coding/dec~~ v circuitry As indicated by the dotted lines "B" in Figure 3 and the assembly diagram, Figure 8, the antennas 80 and 90 are attached to a single frame (the housing lid) 275 with the associated outputs connected to the RF circuit card 110 at the indicated connectors with low loss cables. The top surface of the card 110 is covered with polytetrafluroethylene, a product sold under the trademark DUROID being used for this. The RF
circuit 110 includes MMIC sub-assembly 100 which together combine conventional microwave integrated circuitry, surface mount components and monolithic microwave integrated circuitry (MMIC) as identified in table 6.1 herein.
The coding/decoding circuitry 110 is realized as a surface mount circuit card 250 and is bonded directly to the back of the RF circuit card 110 as illustrated by Figure 8.
The RF circuit card 110 is attached to an RF cavity 260 as shown. A base 270 and lid 275 provide the housing for the transceiver 10 to which a bracket 280 is attached for mounting the antenna in position for use by a subscriber. Input/output cables 290 of the transceiver 10 are provided for connection to the local data network 50 and television set-top receiver 60.
The preferred embodiment described herein is provided as a specific example of the circuitry of the invention and is not intended to limit the scope or definition of the invention which is defined by the appended claims.
Claims (10)
1. A directional millimeter wave transceiver for reception and transmission of signals comprising digital data and/or broadcast television/radio signals in a point-to-multipoint communication system comprising:
(a) a receiving antenna for directional reception of millimeter wave signals having a first predetermined polarity and a transmitting antenna for directional transmission of millimeter wave signals having a second predetermined polarity which is orthogonal to said first polarity, wherein digital data signals are received by said receiving antenna within a first predetermined frequency band, digital data is transmitted by said transmitting antenna within a second predetermined frequency band and broadcast television/radio signals are received by said receiving antenna within a third predetermined frequency band, said second frequency band being between said first and third frequency bands;
(b) radio frequency circuitry for converting said millimeter wave signals to and from intermediary frequency signals wherein said radio frequency circuitry receives said broadcast television/radio and digital data signals from said receiving antenna, converts said received signals to intermediary frequency signals and separately outputs said radio frequency television/radio and data signals and said radio frequency circuitry receives intermediary frequency data signals, converts said intermediary frequency data signals to millimeter wave data signals and outputs said millimeter wave data signals to said transmitting antenna; and, (c) coding/decoding circuitry for modulating/demodulating and coding/decoding said intermediary data signals to condition said intermediary signals for output from said transceiver to a local data network and for input to said radio frequency circuitry.
(a) a receiving antenna for directional reception of millimeter wave signals having a first predetermined polarity and a transmitting antenna for directional transmission of millimeter wave signals having a second predetermined polarity which is orthogonal to said first polarity, wherein digital data signals are received by said receiving antenna within a first predetermined frequency band, digital data is transmitted by said transmitting antenna within a second predetermined frequency band and broadcast television/radio signals are received by said receiving antenna within a third predetermined frequency band, said second frequency band being between said first and third frequency bands;
(b) radio frequency circuitry for converting said millimeter wave signals to and from intermediary frequency signals wherein said radio frequency circuitry receives said broadcast television/radio and digital data signals from said receiving antenna, converts said received signals to intermediary frequency signals and separately outputs said radio frequency television/radio and data signals and said radio frequency circuitry receives intermediary frequency data signals, converts said intermediary frequency data signals to millimeter wave data signals and outputs said millimeter wave data signals to said transmitting antenna; and, (c) coding/decoding circuitry for modulating/demodulating and coding/decoding said intermediary data signals to condition said intermediary signals for output from said transceiver to a local data network and for input to said radio frequency circuitry.
2. A transceiver according to claim 1 wherein said radio frequency circuitry is comprised in a single circuit card.
3. A transceiver according to claim 2 wherein said coding/decoding circuitry is comprised in a single circuit card.
4. A transceiver according to claim 3 wherein said circuit cards are assembled within an external housing and said antennas are mounted on said housing.
5. A transceiver according to claim 1 wherein said radio frequency circuitry comprises a high frequency oscillator circuit, said high frequency oscillator circuit comprising a low frequency synthesizer and multiplication circuitry for multiplying said low frequency synthesizer to a selected millimeter wave frequency.
6. A transceiver according to claim 5 wherein said radio frequency circuitry comprises mixers, an input of which is the output of said high frequency oscillator circuit, and phase locked loop circuitry and said coding/decoding circuitry comprises microprocessor means for permitting local control of the operating frequency of said transceiver by providing control to said high frequency oscillator circuit and said phase locked loop circuitry.
7. A transceiver according to claim 6 wherein said coding/decoding circuitry comprises a reference signal generator for input to said high frequency oscillator circuit and said phase locked loop circuitry, and DC power supply circuitry for use by said radio frequency circuitry and said coding/decoding circuitry.
8. A transceiver according to claim 4 wherein said radio frequency circuitry comprises a high frequency oscillator circuit, said high frequency oscillator circuit comprising a low frequency synthesizer and multiplication circuitry for multiplying said low frequency synthesizer to a selected millimeter wave frequency.
9. A transceiver according to claim 8 wherein said radio frequency circuitry comprises mixers, an input of which is the output of said high frequency oscillator circuit, and phase locked loop circuitry and said coding/decoding circuitry comprises microprocessor means for permitting local control of the operating frequency of said transceiver by providing control to said high frequency oscillator circuit and said phase locked loop circuitry.
10. A transceiver according to claim 9 wherein said coding/decoding circuitry comprises a reference signal generator for input to said high frequency oscillator circuit and said phase locked loop circuitry, and DC power supply circuitry for use by said radio frequency circuitry and said coding/decoding circuitry.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US96210197A | 1997-10-31 | 1997-10-31 | |
| US08/962,101 | 1997-10-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2220781A1 true CA2220781A1 (en) | 1999-04-30 |
Family
ID=29401933
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2220781 Abandoned CA2220781A1 (en) | 1997-10-31 | 1997-11-12 | Millimeter wave transceiver for point-to-multipoint communications system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2220781A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2253076A4 (en) * | 2008-03-11 | 2017-07-26 | Intel Corporation | Wireless antenna array system architecture and methods to achieve 3d beam coverage |
| US11575406B1 (en) * | 2019-07-12 | 2023-02-07 | Cable Television Laboratories, Inc. | Systems and methods for broadband signal equalization |
-
1997
- 1997-11-12 CA CA 2220781 patent/CA2220781A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2253076A4 (en) * | 2008-03-11 | 2017-07-26 | Intel Corporation | Wireless antenna array system architecture and methods to achieve 3d beam coverage |
| US10096891B2 (en) | 2008-03-11 | 2018-10-09 | Intel Corporation | Wireless antenna array system architecture and methods to achieve 3D beam coverage |
| US10693217B2 (en) | 2008-03-11 | 2020-06-23 | Intel Corporation | Wireless antenna array system architecture and methods to achieve 3D beam coverage |
| US11276918B2 (en) | 2008-03-11 | 2022-03-15 | Intel Corporation | Wireless antenna array system architecture and methods to achieve 3D beam coverage |
| US11575406B1 (en) * | 2019-07-12 | 2023-02-07 | Cable Television Laboratories, Inc. | Systems and methods for broadband signal equalization |
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