Abstract:
A communications device for transmitting RF signals from an external antenna. The device comprises a transceiver that sends signals over a cable to an external active antenna. In one embodiment the signals transmitted over the cable intermediate RF frequency signals. The active antenna receives the intermediate RF signals over the cable and up converts or down converts the respective RF transmit and receive signals. In another embodiment of the invention the signals transmitted over the cable are digital signals. The active antenna is functional to process, and covert the respective RF transmit and receive signals.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an active antenna for a communications transceiver, more particularly, the invention relates to  
           [0003]    2. Description of Related Art  
           [0004]    Wireless communication devices are becoming increasingly popular allowing easier mobility, and not requiring cumbersome connecting cables. This is particularly so in the modern electronic work place where computers and other electronic devices can be linked together utilizing various topologies and different types of networks including advanced peer-to-peer networks (APPN), local area networks (LAN), cellular, PCS, Internet, and TCP/IP or various other types of networks. A radio frequency (RF) wireless communications device provides access such that the data processing terminal may be coupled to a large network utilizing RF communications technology. Thus, an operator utilizing such a computer may initiate communications and transfer data between his or her computer and a distributed data processing system without the necessity of access to either telephone lines or power lines. However, this increasing utilization of portable electronic devices refitted with communications modules has led to problems with the efficiency of radio frequency communication. Communication modules originally designed for use in cellular communications circuitry are typically constructed with internal antenna elements optimized for cellular communications. When used in laptops computers, or palmtop computers, RF interferences or non-ideal reception are often problems because of the noise, interference, obstruction and shielding caused by the various components of the devices. In particular, conventional antennas do not function correctly if they are obstructed or shielded by the housing or other structures of the computer. Therefore, one solution is to utilize external antennas.  
           [0005]    [0005]FIG. 1 shows a conventional transceiver configuration. A transceiver  10  is connected to an radio frequency (RF) cable  11 . The RF cable  11  transfers RF signals to and from the transceiver  10  to the antenna  12 . However, with higher frequencies, the RF cable  11  is increasingly lossy, and its loss directly degrades system performance including sensitivity, transmission range, and hence power consumption. This loss also limits the distance the antenna  12  can be placed from the transceiver  10 . Further high frequency-low loss cables and accompanying connectors are extremely cost prohibitive.  
           [0006]    [0006]FIG. 2 shows a conventional active antenna module. A transceiver  20  is connected to an RF cable  21 . The antenna module  24  consists of an antenna  22  connected to a low noise amplifier (LNA)  23 . The antenna module  24  is connected to the other end of the RF cable  21 . The advantage using a LNA  23  is that it allows the antenna module  24  to be placed far away from the transceiver  20 . However, if a high RF frequency is used, the cost of the RF cable  21  is cost prohibitive. Further, if the antenna module  24  is placed a large distance from the transceiver  20 , a significant transmit signal power loss occurs.  
           [0007]    [0007]FIG. 3 shows a conventional active antenna  40 . A transceiver  30  is connected by an extension RF cable  31  to an active antenna  40 . The active antenna  40  includes a first duplexer  41 , a low noise amplifier (LNA)  42 , a power amplifier (PA)  43 , a second duplexer  44 , and an antenna  45 . Signals are transmitted from the transceiver  30  through the extension RF cable  31  to the active antenna  40 . The first duplexer  41  separates transmitted and received signals based on their frequency difference. A transmitted signal is then amplified by the PA  43  and outputted to the antenna  45 . A received signal through the antenna  45  passes to the second duplexer  44  that separates transmitted and received signals based on their frequency, and then passes a receive signal to the LNA  42  for amplification. The signal then passes through the extension RF cable  31  to the transceiver  30 . The active antenna  40  allows a transceiver antenna to be placed a greater distance from the transceiver  30  than the extension RF cable loss normally allows. However, since the frequencies transmitted over the extension RF cable  31  can be a high frequency, the desired extension RF cable  31  is very expensive. Furthermore, the duplexers  41  and  44  cannot be easily reconfigured to variations in transmitting and receiving frequencies and the duplexers  41  and  44  are extremely costly.  
           [0008]    Therefore, a need exists for a communications antenna apparatus that does not require an expensive RF cable, duplexers, or is distance prohibitive.  
         SUMMARY OF THE INVENTION  
         [0009]    One aspect of the invention is an antenna for a radio frequency (RF) communications system.  
           [0010]    Another aspect of the invention is to provide an antenna for a RF communication system that eliminates the need for expensive RF cable to connect the RF transceiver and an antenna.  
           [0011]    A communications receiver is connected to an active antenna module. A main feature of the invention is the transmission of low frequency signals over a low cost cable, wherein the active antenna module is functional to up convert a transmit frequency for transmission, and a received frequency is down converted for transmission over the connecting cable.  
           [0012]    In one embodiment of the invention a transceiver transmits RF signals at a low intermediate frequency (IF), along with control words, and a DC power supply over a extension IF cable connecting an active antenna module. The control words control switches in the antenna module that connect transmit and receive circuitry to the antenna and IF cable input at specific transmit/receive time periods as specified by a communications protocol. The control word further controls the frequency of a synthesizer in the antenna module. When a transmission signal passes through the IF cable from the transceiver, it passes though a first switching device to a mixer. The signal is then up converted when mixed with a signal from an oscillator and the synthesizer. The up-converted signal is then amplified and passes through a second switching device before going to an antenna. When a signal is received by the antenna is passes through the second switching device to a low noise amplifier. The signal then passes to a mixer where it is down-converted when mixed with a signal from the oscillator/synthesizer. The down-converted received signal then passes through the first switching device and travels via the extension IF cable to the transceiver.  
           [0013]    In a second embodiment of the invention a communications unit is connected to an active antenna module through an extension cable. A transceiver sends digital data containing transmission information to a data framer. Likewise a control word generator sends digital information to the data framer. The data framer packages the information and transmits the data along with a D.C. power supply though an extension cable to active antenna module. A data framer in the antenna module separates the information. The control word data controls the frequency of a synthesizer and a switch functional to connect to transmit/receive circuitry at specific time periods as specified by a communications protocol. Transmit information from the transceiver passes through a digital signal processor, to an digital to analog converter, and then to an mixer where the signal is up converted when mixed with a frequency generated by the frequency synthesizer/oscillator. The signal is then amplified by a power amplifier, and passes through a switch to an antenna. When a signal is received it passes through a low noise amplifier, is down converted by a mixer with a frequency generated from the synthesizer/oscillator. The signal then passes through an intermediate frequency signal processor, to an analog to digital converter, and to a digital signal processor. The data then passes to the antenna module data framer, passes through the extension cable, to the second data framer, and then to the transceiver.  
           [0014]    These and other features, which characterize the invention, are set forth in the claims annexed hereto and forming a further part hereof. However, for a better understanding of the invention, and of the advantages and objectives attained through its use, reference should be made to the Drawings, and to the accompanying descriptive matter, in which there is described exemplary embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    [0015]FIG. 1 shows a conventional external antenna;  
         [0016]    [0016]FIG. 2 shows another conventional active antenna;  
         [0017]    [0017]FIG. 3 shows another conventional active antenna;  
         [0018]    [0018]FIG. 4 shows a communications module of a first embodiment  
         [0019]    [0019]FIG. 5 shows a communication module; and  
         [0020]    [0020]FIG. 6 shows a third embodiment of a communication module. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. The preferred embodiments are described in sufficient detail to enable these skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only be the appended claims.  
         [0022]    In a first embodiment of the invention as shown in FIG. 4, an extension intermediate frequency (IF) cable  125  connects a communications unit  100  to an active antenna module  150 . The extension IF cable  125  in the embodiment is preferably a multi-strand cable for carrying the signals. The communications unit  100  includes a transceiver  101 , a DC supply source  102 , and a control word generator  103 . The active antenna module  150  includes an intermediate frequency (IF) filter  151 , a control word filter  153 , and a DC filter  152 . The IF filter  151  is connected to a switch  154 . The switch  154  is connected to a receiving mixer  156  and a transmitting mixer  158 . A low noise amplifier (LNA)  157  is disposed between the receiving mixer  156  and a switch  155 . A power amplifier  159  is disposed between the transmitting mixer  158  and the switch  155 . The transmitting mixer  158  and the receiving mixer  156  are connected to a low-frequency f_LO synthesizer  160  and oscillator  161 . The input of the LNA  157  and output of the PA  159  are connected to an antenna  162  alternatively through the antenna switch  155 .  
         [0023]    The DC supply  102  provides electrical power for the operation of the active antenna module  150 , and the DC filter  152  is provided in the active antenna module  150  to reduce any fluctuation in the DC supply  102  that occurs during transmission over the extension IF cable  125 . A control word generator  103  generates control signals for the switch  154 , the switch  155  and the f_LO synthesizer  160 . The control word filter  153  is operable to receive signals transmitted from the control word generator  103  over the extension IF cable  125 , and provide the signals to the appropriate device, such as the switch  154 , the switch  155  and the f_LO synthesizer  160 . For example, in an event of a transmission of data in the system, the transceiver  101  transmits data in a proper time slot over the extension IF cable  125  along with the appropriate control words from the control word generator  103 , and DC power to operate the active antenna module  150 . The control word creates a connection path to be made between the IF filter  151 , the transmitting mixer  158  and the PA  159  with the antenna  162 . The control word also instructs the f_LO synthesizer  160  to generate a proper frequency. The data is passed through the IF filter  151 , the switch  154  to the transmitting mixer  158 . After the transmitted data being mixed with a frequency generated by the oscillator  161 , a higher frequency signal will be amplified by the PA  159  and outputted through the antenna  162 .  
         [0024]    When data is received in the appropriate time slot, the control work generator  103  configures the switches  155  and  154  to make a connection between the antenna  162  and the input of the LNA  157 , and the output of the mixer  156  and the IF filter  151 . The control word further sets the frequency generated by the f_LO synthesizer  160 . The data is received by the antenna  162  and amplified by the low noise amplifier  157 . The signal then enters the mixer  156  with the frequency from the oscillator  161  lowering the frequency of the signal. The signal then passes through the IF filter  151 , the extension IF cable  125 , to the input of the transceiver  101 .  
         [0025]    [0025]FIG. 5 shows an embodiment of the invention similar in every way to the apparatus shown in FIG. 4, however the DC supply is provided on a line separate from the Extension IF cable  203  to the DC filter  215  of the active antenna module. That is, an additional line for supplying power is provided in the embodiment.  
         [0026]    [0026]FIG. 6 shows another embodiment of the invention. An extension IF cable  225  connects a communications unit  200  with an active antenna module  250 . A data framer  202  is connected to a transceiver  201  and a control word generator  204 . The data framer  202  and a DC supply source  203  are connected to an extension IF cable  225 . In the active antenna module  250  another data framer  251  and a DC filter  252  are connected to the extension IF cable  225 . The data framer  251  is connected to a control word filter  265 . A data-out portion of the second data framer  251  is connected to a digital signal processor  258 , a digital to analog converter (DAC)  259 , a f_IF signal processor, a mixer  261 , and then a power amplifier  262 . A receiving portion of the data framer is connected to a digital signal processor  253 , an analog to digital converter (ADC)  254 , a f_IF signal processor  255 , a second mixer  256 , and a low noise amplifier  257 . The mixers  261  and  256  are connected to a f_LO synthesizer  263  and an oscillator  264 . The input of the LNA  257  and the output of the PA  262  are connected to a switch  266  and an antenna  267 .  
         [0027]    When a data transmission occurs data from the transmitter  201  is sent to the data framer  202 , along with appropriate control words from the control word generator  204 . The data framer  202  packages the digital data into a data format that can be transmitted over the extension IF cable  225  preferably over a single cable strand. In addition, a DC supply  203  is transmitted over the extension cable to supply the active antenna module  250  with power. The data framer  251  of the active antenna module receives the transmit data along with the control words. The control words pass to the control word filter, and then are used to control elements of the active antenna module  250  such as the frequency generated by the f_LO synthesizer, and the switch  266 . The control words can be further utilized to control the signal processors of the active antenna module  250 . The transmitted digital data is then outputted from the data framer  251  to the digital signal processor  258 . The digital signal processor  258  processes the data and then sends the digital data to the DAC  259 . The outputted analog signal is then passed to the f_IF signal processor for further processor before being mixed with a frequency from the oscillator  264  up-converting the frequency of the signal. The signal is then amplified by the PA  262 , passes through the switch  266  and is outputted from the antenna  267 .  
         [0028]    Signals received by the antenna  267  pass through the switch  266  to the LNA  257 . The amplified signal is then mixed with a signal from the oscillator  264  in the mixer  256  down-converting the frequency of the signal. The down-converted signal is then processed by the f_IF signal processor  255  and is converted to digital signal in the ADC  254 . The digital received signal is processed by the digital signal processor  253  and is passed to the data framer  251 . The data framer packages the received data and transmits it over the extension cable  225 . The data framer  202  in the communications unit  200  retrieves the received digital data and forwards it to the transceiver  201 .  
         [0029]    Various additional modifications may be made to the illustrated embodiments without departing from the spirit and scope of the invention. Therefore, the invention lies in the claims hereinafter appended.