Abstract:
A remote mounted RF (radio frequency) bi-directional converter/amplifier device that connects to a half-duplex radio transceiver that converts and amplifies the RF signals to and from that signal to a different radio band. The pole mounted converter senses when the transceiver connected to it goes into the transmit mode and automatically switches the device from converting the received signal to the RF band of the transceiver to converting the RF signal from the transceiver to a different frequency band and amplifying that transmit signal. Refer to FIG.  1.  This invention is an improvement to and continuation of the amplifier system that is disclosed in Utility patent application Ser. No. 09/505,201 filed Feb. 16, 2000.

Description:
BACKGROUND OF THE CURRENT INVENTION  
         [0001]    The 2.4 GHz license-free radio band is widely used for Spread Spectrum Wireless Local Area Network (WLAN) applications. The most commonly used technology in this is bands are devices designed to comply with the IEEE 801.11 and 802.11b standards. This standard specifies half-duplex operation in a Time Division Duplex (TDD) mode. In TDD, each radio can receive and transmit, but not at the same time. Two-way duplex communication takes place by sharing the airwaves based on time slots. One unit transmits and the other listens. Once the first unit goes off the air and switches to receive mode, the other unit is free to use the airwaves and send its data. If for some reason, two devices in communication with each other transmit at the same time, the data packets will be lost and will need to be retransmitted.  
           [0002]    Most of these WLAN devices use the 802.11b standard. This standard defines fourteen Direct Sequence Spread Spectrum (DSSS) channels separated by five MHz, (i.e., 2412 MHz, 2517 MHz, 2422 MHz, etc.). Only the first eleven of which can be used in the United States. Each channel occupies about 22 MHz of bandwidth. Therefore, at any one location (e.g., office, rooftop, or radio tower) a maximum of three 801.11b DSS radio channels can be used—typically channels 1, 6 and 11. If the channels are too close to each other are used (e.g., channels 5 and 7) the sideband noise from the radiated spectrum from one transmitter will interfere with the reception of the remote client signals on other co-located radios. Thus, in most installations, no more then three 802.11b radio channels are used at any one location.  
           [0003]    There are many manufacturers that make WLAN device for this band and many millions of these devices have been sold worldwide. This has reduced the cost of these high-performance radio devices serving to expand their proliferation.  
           [0004]    These WLAN devices were originally designed for indoor use to provide wireless connectivity to PCs and other devices. However, by using external outdoor antennas and amplifiers (like that disclose in Utility patent application Ser. No. 09/505,201) with these devices enable long-range outdoor applications. These have proliferated in recent years crowding the 2.4 GHz license-free radio band.  
           [0005]    Also operating on this band are microwave ovens, cordless telephones, low-power video surveillance cameras, consumer-grade video transmitters, and high power Amateur Radio transmitters stations. The combined interference generated by all these devices is making reliable use of these bands for long-range outdoor use untenable in many urban areas. In the near future, the numbers of locales where interference abounds will increase.  
           [0006]    There is, however, a license-free Spread Spectrum band in the 5.725 to 5.850 GHz range available for use in the United States and other countries. However, the cost for outdoor radio devices that operate in this band can be ten to twenty times more expensive then the low-cost 2.4 GHz radio equipment. The present invention enables any 2.4 GHz TDD Spread Spectrum radio devices to operate in the 5.8 GHz band or any other radio band thereby avoiding all the interference found on the 2.4 GHz band. Further, the present invention can be utilized to convert any TDD radio on any band to operate on any other radio band.  
           [0007]    Still further, the present invention can be utilized to enable TDD radios to operate split-band (i.e., transmitting on one band and receiving on another). By applying the principles of the present invention, the limitation of co-locating only a few 802.11b DSSS radios at any one location can be resolved. In fact, using the present invention discloses how all of the 802.11b radio channels could be utilized at any one location in a properly designed system. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    [0008]FIG. 1 shows a typical installation drawing with Converter Amplifier mounted near the antenna with coax cables connecting it to the DC Injector and radio transceiver  
         [0009]    [0009]FIG. 2 shows a simple block diagram illustrating how the Converter Amplifier module translates radio frequencies  
         [0010]    [0010]FIG. 3 shows the circuit elements found inside the bi-directional Converter Amplifier module  
         [0011]    [0011]FIG. 4 shows the one-way Converter Amplifier module where only the transmitted signal gets translated.  
         [0012]    [0012]FIG. 5 shows the component to FIG. 4 where only the received signal gets translated.  
         [0013]    [0013]FIG. 6 illustrates how complementary pair of one-way Converter Amplifiers communicate over-the-air.  
         [0014]    [0014]FIG. 7 shows an alternate form of the Converter Amplifier where no DC Injector is required when the radio transceiver and antenna are all co-located.  
         [0015]    [0015]FIG. 8 illustrates how a multi-channel system can be deployed using one-way frequency conversions at each end of a link.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Refer to FIG. 2. In transmit mode, radio frequency (RF) signals generated in the radio device connected to Converter Amplifier  1  on frequency band A are converted to frequency band B. Likewise, when Converter Amplifier  1  is in the receive mode, received signals entering Converter Amplifier  1  in frequency band B are converted to frequency band A. Converter Amplifier  1  is a half-duplex device and automatically switches from receive to transmit mode. The device can be built to either up or down convert. In other words, the converted frequencies could be either higher or lower in frequency than the operating frequency of the radio it is connected to.  
         [0017]    [0017]FIG. 1 details the preferred installation of the present invention. Normally, antenna connector  21  is connected via coax cable  3  external antenna  87  tuned to operate on to frequency band B. In the receive mode, RF signals picked up by antenna  87  enter Converter Amplifier  1  at antenna connector  21 . They are then converted to frequency band B, amplified and feed out of Converter Amplifier  1  at radio connector  20  to DC (direct current) Power Injector  2 . The converted RF signal travels down coax cable  4  to DC Power Injector  2  through RF connector  72 . The signal then passes through DC Power Injector  2 , out RF connector  60  and to Transceiver Radio  6  thru the second coax cable  9  attached to Transceiver Radio  6 .  
         [0018]    When Transceiver Radio  6  goes into the transmit mode, RF energy from Transceiver Radio  6  travels the same path. The signal passes from Transceiver Radio  6  through coax cable  9  in RF connector  60  to DC Power Injector  2  on through coax cable  4  to Converter Amplifier  1  through radio connector  20 . They are then converted to frequency band B, amplified and fed out of Converter Amplifier  1  at antenna connector  21  to external antenna  87  via coax cable  3 .  
         [0019]    DC Power Injector  2  serves the primary purpose of injecting DC power onto coax cable  4  to power the electronics in Converter Amplifier  1 . Additionally, DC Power Injector  2  offers lightning and power surge protection as well as LEDs to show the operational status of the system.  
         [0020]    [0020]FIG. 3 shows the circuit components inside Converter Amplifier  1  in the preferred embodiment. In the receive mode, the received RF signal enters Converter Amplifier  1  at antenna connector  21 . The signal is filtered by frequency band B Bandpass Filter  36  via electronic switch  35  and proceeds into noise amplifier (LNA)  30 . This signal is fed into receive RF Mixer  29  where it is mixed with the signal from Local Oscillator (LO)  31 . The resulting signal is converted or translated to RF frequency band A and fed though frequency band A Bandpass Filter  27  and tuned to pass all frequencies in band A. The signal is then passed through input switch  24  and to radio connector  20  where it is ultimately presented to Transceiver Radio  6  from the transmission coax cable  4 , through DC Power Injector  2  and along coax cable  9 .  
         [0021]    When Transceiver Radio  6  is operated in the transmit mode, the RF energy enters Converter Amplifier  1  at the radio connector  20 . The Power Sense circuitry switches the converter module from receive to transmit mode. The transmit signal in frequency band A from Transceiver Radio  6  passes through input switch  24  through attenuator pad  32 . Attenuator pad  32  reduces the transmit signal to a level suitable for the input of transmit mixer  33 . This signal is combined with the output of LO  31  and converted to frequency band B. It is then amplified to the desired power level by power amplifier  34 . The signal then passes through output switch  35  and Frequency Band B Bandpass Filter  36  to antenna connector  21  and antenna  87  shown in FIG. 1.  
         [0022]    The DC voltage to power Converter Amplifier  1  is picked off radio connector  20  through an inductor and fed to power supply  26  to power the circuitry in the converter module.  
         [0023]    Alternate Forms of the Converter Module  
         [0024]    Alternate forms of the converter module include implementations which a converter amplifier module is built to convert either the receive or transmit signals to the other band, but not both. In this case, the signal that is not translated is simply amplified and filtered. This approach enables band-slot operation where one system transmits over-the-air on frequency band A and the other on frequency band B. In this configuration, the Converter Amplifier requires two antenna connectors with each one connected to a separate external antennas. One antenna is tuned to frequency band A and the other frequency band B.  
         [0025]    Referring to FIG. 4, a one-way Converter  40  translates the transmit signal from the radio to frequency band B through input switch  24 , attenuator pad  32  and mixer  33 . The signal is amplified by power amplifier  34  and passes through Bandpass Filter  36  tuned to Frequency Band B. However, in this version of Converter  40 , the receive frequency is not converted, but rather it is just filtered  30 , amplified  28  and sent through an optional attenuate through input switch  24  to Transceiver Radio  6 .  
         [0026]    The complimentary version of this form of the converter module is shown in FIG. 5. One-way Converter  41  converts the receive signal on frequency band B entering the converter on antenna connector  21 . The transmit signal from Transceiver Radio  6  on frequency band B enters Converter  41  at the radio connector  20  and is amplified  37  and filtered  38  without being converted to frequency band B.  
         [0027]    These two implementations of one-way conversion devices work as a complimentary pair to each other. FIG. 6 illustrates two one-way Converters  40 ,  41  in a typical link. One of the primary advantages of this arrangement is that at a base site, multiple transmitters could be all transmitting on different radio channels in frequency band and all the reception on frequency group B. This split-band operation prevents in-band signals from overloading local receivers since the receive signals are found in frequency band B not frequency band A where all the strong transmit signals are located.  
         [0028]    [0028]FIG. 7 illustrates an additional alternate form of the present invention where Converter Amplifier  80  has its DC Power  88  applied directly to it without the use of a DC power injector. This form could be used when Converter Amplifier  80  is located very close to radio transceiver  83 . In this case, the coax cables that run from antenna  84 , Converter Amplifier  80  and radio transceiver  83  are all short. Typically, Converter Amplifier  80  and radio transceiver  83  would both be located in outdoor enclosure  86 . This configuration precludes the need for a DC injector.  
         [0029]    Multi-channel Split-band System  
         [0030]    [0030]FIG. 8 illustrates one of the ways a multi-channel system can be deployed using one-way converter amplifiers. In this system, there are “n” radio transceivers  100 ,  101 ,  102  operating on frequency band A. Each radio has its own DC Injector  105 ,  106 ,  107 , coax cable  108 ,  109 ,  110  and one-way Converter Amplifier  111 ,  112 ,  113 . These converter amplifiers are shown in FIG. 5. They are one-way converters and, on this end of the link, only convert received signals on frequency band B down to frequency band A. The frequency band A signals coming from radio transceivers  100 ,  101 ,  102  are only amplified, not translated, in the Converter Amplifier. The transmit signals from each Converter Amplifier  111 ,  112 ,  113  (still on frequency band A) are fed through an optional RF Isolator  114 ,  115 ,  116  and fed into a transmitter combiner  118  and thence into one or more common transmit antenna  120  and sent to remote units. Signals on frequency B from the remote units are received by antenna  121 , fed through splitter  122  and into Converter Amplifiers  111 ,  112 ,  113 . These signals are converted to frequency band A and sent to radio transceivers  100 ,  101 ,  102 .  
         [0031]    A similar complimentary operation occurs at the remote unit. In this case, the converter amplifier in FIG. 4 is used (i.e., the radio transceivers&#39; transmit frequencies are translated from A to B, but the received signals are not translated since they already are on frequency band A.). The over-the-air frequency used for this system is shown in FIG. 6.