Abstract:
A portable apparatus for upconverting and downconverting the signals used to provide information interchange between terminals in terrestrial or satellite communications systems. The apparatus enables the upconversion and downconversion of electronic signals from baseband to the frequencies of the radio waves used for communications between the terminals. Such frequencies would typically be in the microwave range, i.e. from several GHz upwards. In the preferred embodiment the apparatus comprises two suitcase-sized units. One unit contains the apparatus for the modulation of electronic signals from base band frequencies to a chosen intermediate frequency and microprocessor-based circuitry to provide a centralized interface for overall monitoring and control of the apparatus. In addition, the first unit includes a built-in spectrum analyzer module which enables the visual spectral display of both transmit and receive signals. The second unit contains upconverters and downconverters for upconversion and downconversion of the selected intermediate frequencies to and from the desired air-link frequencies.

Description:
FIELD  
         [0001]    The present invention relates generally to wireless communications systems.  
         BACKGROUND OF THE INVENTION  
         [0002]    Terminals in terrestrial or satellite microwave communications systems contain apparatus for the processing of base band signals, such as voice, video, or data signals, such that these signals can be transmitted and received to and from other terminals. A major constituent of such terminals is the apparatus which upconverts and downconverts the base band signals to or from the frequencies used for the air-link. The prior art does not disclose portable terminals, capable of reception and transmission, that are able to provide in-service terminal monitoring, control, alignment, and commissioning, without the need for specialized external equipment.  
           [0003]    It is also common practice in the prior art to connect various independent base band and unconversion and downconversion components to form an earth terminal. Such earth terminals consist of a number of autonomous units or modules, such as video encoders, encapsulators, modulators, demodulators, receivers, upconverters and downconverters, interconnected by cables and controlled by software. An example of such a system is shown in FIG. 1. The depicted earth terminal  50 , consists of an MPEG-2 Video Encoder  10 , an IP Encapsulator  20 , a DVB-S Receiver  30 , and a Monitor and Computer  40 . However, such previous art implementations suffer from several major drawbacks. Firstly, the overall assembly is large and the individual modules have to be re-assembled and interconnected in the field such that use in a portable mode is not practical. In addition, the re-assemby and interconnection requires time and there is a risk that errors are made. An important requirement for portable earth terminals is that they be capable of rapid on-site deployment and communications, especially in applications such as satellite news gathering. Time lost in re-assembly is costly and inconvenient.  
           [0004]    Also, since the overall earth terminal is controlled by software resident on the computer terminal  40 , each individual device, unit, or module is required to have a common control interface. Since the earth terminal  50  is composed of units obtained from individual manufacturers or suppliers, either each unit would have to be manufactured to a single common specification, which is costly and often impossible; or, alternatively, each unit must have an individual software interface, which greatly increases the complexity of the control and monitor software as well increasing the likelihood of errors.  
           [0005]    In the prior art, there have been attempts to overcome these limitations, through a partial integration of a number of the individual modules. For example, an IP Encapsulator has been integrated with an MPEG-2 Encoder. In addition, an MPEG-2 Encoder has been integrated with a DVB-S Modulator. However, there does not exist any overall integration of all the required earth terminal functions.  
           [0006]    In one example of the prior art, U.S. Pat. No. 5,603,102, issued to Rebec, discloses a portable earth terminal. The apparatus described in Rebec compartmentalizes the transmit and receive functions wherein base band transmit and receive apparatus are physically and electrically separated. Such separation does not permit the combination of like base band functions, nor does it permit the incorporation of a built-in means for spectral display and analysis. Furthermore, Rebec does not disclose means for IP input/output and processing, or means for providing a quality of service.  
           [0007]    U.S. Pat. No. 5,081,703, issued to Lee, discloses an earth terminal which is capable of providing the features and functions of a remote telephony switching office. However, the apparatus described is not portable, nor does it contain means for self-test or alignment.  
           [0008]    In another example of the prior art, U.S. Pat. No. 6,031,878, issued to Tomasz et al., discloses means for the reception of signals from a satellite by a fixed earth terminal. However, no means of transmitting a signal from an earth terminal to a satellite is disclosed, nor is any means of aligning such an apparatus without the need for specialized external test equipment. In addition, the apparatus of Tomasz is limited to digital video reception.  
           [0009]    U.S. Pat. No. 5,915,020, issued to Tilford et al., discloses means for the reception of video signals from a satellite by a portable earth terminal. No means of transmitting a signal from an earth terminal to a satellite is mentioned, nor is any means of built-in spectral display for the purpose of test and alignment.  
           [0010]    Accordingly, it is an object of this invention to provide a highly integrated upconversion/downconversion apparatus suitable for portable implementations, which incorporates built-in overall monitoring and control of all functions, thus eliminating the need for external test and monitoring equipment.  
           [0011]    It is a further object of this invention to provide a portable, integrated base band processing engine which, when operated in conjunction with upconverters and downconverters, can provide all the functions required in a portable satellite earth terminal.  
           [0012]    It is yet a further object of this invention to provide an integrated means for viewing the spectra of both transmit and receive signals. This is in order to assure proper operation, as well as, in the case of satellite systems, to aid in alignment of the earth terminal and to facilitate satellite identification.  
         SUMMARY OF THE INVENTION  
         [0013]    These and other objects have been realized in a portable terminal for terrestrial or satellite wireless communications comprising a baseband unit and an upconversion and downconversion apparatus.  
           [0014]    The baseband unit integrates all the base band functions of an earth terminal and comprises an MPEG-2 Encoder, a Voice Over IP (VOIP) gateway, an IP Encapsulator, a DVB-S Receiver, and an Ethernet Network Interface Connection Module. In the preferred embodiment, the baseband unit includes a computer, a keyboard, a mouse, and a flip-up monitor.  
           [0015]    The input to the baseband unit can be either raw video, voice over IP, or IP data. The baseband unit allows for the input of several standard video formats. The baseband unit encodes this raw video input signal into MPEG-2, Part  2  format. This MPEG-2 encoded data is then sent to the IP encapsulator for further processing. In addition, the baseband unit allows for the input of voice signals, typically emanating from an analog or digital telephone. The voice signals are encoded into IP format and then sent to the IP encapsulator for further processing. Furthermore, IP data can be inputted via an Ethernet connection and forwarded to the IP encapsulator for processing. Independent streams from multiple sources are multiplexed. The resultant stream can then be inputted to a modulator, resident outside of the baseband unit. In the preferred embodiment the baseband unit also provides the capability of displaying on a monitor in real-time, the encoded video that is being transmitted.  
           [0016]    The baseband unit also provides the capability of demodulating, decoding, and receiving IP traffic from a satellite. The baseband unit is capable of demodulating an L-band signal, decoding MPEG-2, Part  1  transport streams into IP packets, and sending these IP packets to the end user.  
           [0017]    The baseband unit also includes a rugged and mobile computer for IP data applications, video monitoring, management functions, and spectral analysis. Computer IP applications, such as Web browsing, telnet, ftp, and email can be run, and a single point user interface is provided. This user interface permits control and monitoring of the earth terminal, including all of the components of the baseband unit as well as associated apparatus, such as upconverters and downconverters.  
           [0018]    The upconversion and downconversion apparatus comprises two units, the RF 1  processing and control unit and the RF 2  processing unit which, when combined with additional processing and powering apparatus, can be used for the reception and transmission of signals to and from terminals in terrestrial or satellite wireless communications systems.  
           [0019]    The RF 1  Processing and Control Unit and the RF 2  Processing Unit are used for upconversion and downconversion of signals to and from the air link frequencies between terrestrial terminals or between earth terminals and a satellite. The RF 1  Processing and Control Unit and the RF 2  Processing Unit are connected by a multi-conductor cable, referred to herein as the Inter Facility Link.  
           [0020]    The RF 1  Processing and Control Unit is used for modulating and upconverting base band signals, which may contain voice, video, or any form of data, to the intermediate frequencies used in the Interfacility Link. The RF 1  Processing and Control Unit comprises a modulator to which the base band signal is applied. The output of this modulator is then upconverted to the intermediate frequency used in the Interfacility Link. In the illustrative embodiment the modulator is a 70 MHz modulator and the frequency of the Interfacility Link is in the 950 MHz to 1450 MHz range of the L-band, however, other L-band frequencies may be used.  
           [0021]    The RF 1  Processing and Control Unit also contains a Spectrum Analyzer Module, which accepts signals from a transmit downconverter and a receive downconverter. These signals are then forwarded to the base band unit.  
           [0022]    The RF 2  Processing Unit provides block upconversion and block downconversion of transmit and receive signals, respectively, between the air interface frequency and the L-band.  
           [0023]    The RF 2  Processing Unit consists of a transmitter, which upconverts the L-band transmit signal, received from the Interfacility Link, to the air-link frequency used for transmission to another terminal or to a satellite. This air-link frequency transmit signal is then amplified to a level suitable for transmission. A sample of the transmitted signal is downconverted to L-band by means of a block downconverter and is used in the RF 1  Processing and Control Unit for monitoring and display purposes.  
           [0024]    The RF 2  Processing Unit also contains a Low Noise Block Downconverter, which downconverts the air-link signal received from another terminal or satellite to L-band frequency for carriage on the Interfacility Link.  
           [0025]    The RF 1  Processing and Control Unit also comprises a stable reference source for providing the reference frequencies needed for modulation, upconversion and downconversion. A microprocessor is used for the control and monitoring of both the RF 1  Processing and Control Unit and the RF 2  Processing Unit.  
           [0026]    The apparatus herein described results in a novel terminal capable of rapid deployment without the need for external specialty test equipment. This is particularly important in the case of portable terminals.  
           [0027]    Other objects, features, aspects and advantages of the present invention will become apparent to those of ordinary skill from the following detailed description of the invention taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    The invention itself both as to organization and method of operation, as well as additional objects and advantages thereof, will become readily apparent from the following detailed description when read in connection with the accompanying drawings, wherein:  
         [0029]    [0029]FIG. 1 illustrates a typical prior art satellite earth terminal base band assembly, illustrating how the separate units are interconnected;  
         [0030]    [0030]FIG. 2 is a block diagram of the earth terminal of the present invention;  
         [0031]    [0031]FIG. 3 is a block diagram of the baseband unit;  
         [0032]    [0032]FIG. 4 is a block diagram of the RF 1  Processing and Control Unit; and  
         [0033]    [0033]FIG. 5 is a block diagram of the RF 2  Processing Unit.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    [0034]FIG. 2 illustrates how the baseband unit  101  can be interconnected with other components to form a complete satellite earth terminal  1 . The satellite earth terminal  1  can be seen to consist of two distinct physical packages, namely suitcase  2 , and suitcase  3 . Suitcase  2  is composed of a baseband unit  101 , which is the subject of the present invention, an AC-DC and DC-AC power supply  103 , and an RF 1  processing and control unit  102 . Suitcase  3  is composed of an RF 2  processing unit  104  and antenna and superstructure  105 .  
         [0035]    Referring to FIG. 2, the preferred embodiment of the terminal  1  of the present invention comprises suitcase-sized units  2  and  3 . Suitcase  2  is composed of a Baseband Processing Unit  101 , an AC-DC and DC-AC Power Supply  103 , and the RF 1  Processing and Control Unit  102 . Suitcase  3  is composed of the RF 2  Processing Unit  104  and an Antenna and Superstructure  105 .  
         [0036]    In FIG. 2, bi-directional interconnecting lines are used to indicate that signal flow is bi-directional. That is, signal flow can be from the customer interface  110  through to the air-link interface  120 , and equally from the air-link interface  120  to the customer interface  110 . The following is a high level view of the signal processing which occurs in satellite earth terminal  1 , with emphasis on the signal processing within baseband unit  101 . The relationship between baseband unit  101  and the other components in the satellite earth terminal  1  are described to better explain the functions of baseband unit  101 .  
         [0037]    In the transmit direction, a base band signal originating at the Customer Interface  110  enters Suitcase  2 . This base band signal first enters Base Band Unit  101 . The base band signal then leaves Base Band Unit  101 , and enters RF 1  Processing and Control Unit  102 . Said RF 1  Processing and Control Unit  102  upconverts the base band signal to an L-band intermediate frequency transmit signal. The frequency of the Interfacility Link  106 , for purposes of illustration only, is at L-band. The AC-DC and DC-DC Power Supply  103  provides the electrical power required for Base Band Unit  101 , RF 1  Processing and Control Unit  102 , and RF 2  Processing Unit  104 . Electrical power for RF 2  Processing Unit  104  is transmitted from the AC-DC and DC-AC Power Supply  103  to RF 2  Processing Unit  104  by means of Interfacility Link  106 .  
         [0038]    The L-band transmit signal from Suitcase  2  is transmitted to Suitcase  3  by means of the multi-conductor Interfacility Link  106 . Said Interfacility Link  106  provides bilateral connection for the L-band transmit and receive signals, as well as all monitoring and control signals, all frequency reference signals, and all electrical power required for Suitcase  3 .  
         [0039]    The intermediate frequency transmit signal enters Suitcase  3 , and is connected to the RF 2  Processing Unit  104 . In RF 2  Processing Unit  104 , the intermediate frequency transmit signal is upconverted to the frequency used for the air-link to another terminal or to the satellite, and amplified to the power level required. The air-link frequency transmit signal is then transmitted by means of Antenna and Superstructure  105 .  
         [0040]    Similarly, in the receive direction, the air-link receive signal is received from another terminal or from the satellite by means of the Antenna and Superstructure  105 . The air-link receive signal is then applied to RF 2  Processing Unit  104 , where it is downconverted to the intermediate frequencies used in the Interfacility Link  106 .  
         [0041]    In Suitcase  2 , the intermediate frequency receive signal is connected to RF 1  Processing and Control Unit  102 . In RF 1  Processing and Control Unit  102  the signal is passed through, unchanged in frequency, to Base Band Unit  101 . Base Band Unit  101  outputs to the Customer Interface  110 .  
         [0042]    [0042]FIG. 3 is a block diagram of the baseband unit  101 . Baseband unit  101  is seen to consist of a motherboard  201 , which may incorporate computer functions, and which provides the means for interconnecting the various constituents of baseband unit  101 . Baseband unit  101  also consists of an MPEG-2 encoder  202 , a computer  203 , containing a mouse and a flip-up monitor, an IP encapsulator  204 , an Ethernet network interface connection module  205 , a voice over IP gateway module  206 , and a DVB-S receiver  207 .  
         [0043]    Alternatively, voice is inputted to the VoIP interface module  207  either through the analog or digital interface. The VOIP interface module  207  encodes the voice data into IP packets. The IP formatted voice data is then inputted to the Ethernet network interface module  205  and then inputted to the IP encapsulator  204  for further processing.  
         [0044]    Alternatively, IP data from the customer interface  110  can be inputted to the Ethernet network interface module  205  of the baseband unit  101 . The IP data is then inputted, through motherboard  201 , to the IP encapsulator  204  for further processing.  
         [0045]    The IP encapsulator  204  encapsulates the inputted IP data, MPEG-2, Part  2  encoded video data, and/or IP encoded voice, into MPEG-2, Part  1  Transport Stream packets, and outputs the time division multiplexed signal onto either Asynchronous Serial Interface (ASI) or an Synchronous Serial Interface (SPI) format. The MPEG-2, Part  1  Transport Stream packets are then inputted to the RF 1  processing and control unit  102  where they are modulated onto a 70 MHz carrier. The modulated output is then upconverted to L-band, and applied, through interfacility link  106 , to RF 2  processing unit  104 .  
         [0046]    In RF 2  processing unit  104 , the L-band input signal from RF 1  processing and control Unit  102  is upconverted to the desired transmit frequency which, in this example, is Ku or Ka band. The upconverted signal is then amplified to the power required for transmission to a satellite, and transmitted by means of antenna and superstructure  105 .  
         [0047]    In the receive direction, the air link signal received from the satellite enters suitcase  3 , and is applied to antenna and superstructure  105 . The receive signal is then downconverted to L-band, and connected to RF 1  processing and control unit  102  via interfacility link  106 .  
         [0048]    The L-band receive signal obtained from RF 2  processing unit  104  by means of interfacility link  106  passes through RF 1  processing and control unit  102  unchanged in format and frequency, and is applied to base band unit  101 .  
         [0049]    The L-band receive signal from RF 1  processing and control unit  102  enters base band unit  101  and is applied to DVB-S Receiver  207 . The DVB-S receiver  207  demodulates the L-band receive signal into MPEG-2, Part  1  Transport Stream packets. The DVB-S receiver decodes the MPEG-2, Part  1  Transport Stream packets to base band data, and forwards the base band data to the computer  203  for processing and outputting to the customer interface  110 .  
         [0050]    IP Encapsulator  204  contains a built-in quality of service means. The quality of service means comprises a three-tier system, wherein, in the first tier, individual bundles of Packet Identifiers (PIDs) can be created. Each bundle may be assigned a Constant Bit Rate, Variable Bit Rate, or Uncommitted Bit Rate. The second tier establishes the quality of service of individual PIDs within each bundle. The individual PIDs within each bundle can be assigned a Constant Bit Rate, Variable Bit Rate, or Uncommitted Bit Rate. The third tier establishes the quality of service of IP packets carried by a PID. The IP packets, which are identified by a destination IP address, may be assigned a rate limit, limiting the rate at which said destination IP packets can be transmitted. By such means, a bundle can be configured as a shared or dedicated bundle. Also, a PID within a shared bundle can use available bandwidth from another shared bundle, while a PID within a dedicated bundle is only permitted to share bandwidth within its own dedicated bundle.  
         [0051]    Using the quality of service means, priorities can be assigned to the PIDs within a bundle as well as to the bundles themselves. Thus, the shared bundle with the highest priority will gain access to the available bandwidth. Also, when two shared-bundle PIDs contend for available bandwidth, the PID with the highest priority is assigned the bandwidth.  
         [0052]    The operation of Baseband unit  101  is explained by describing the main signal flow, firstly for the transmit direction. The input from the customer interface  110  can be in the form of raw video, voice, (e.g. from a telephone) or IP data (e.g. from an IP network).  
         [0053]    Raw video is inputted to MPEG-2 encoder  202  through either the serial digital interface (SDI), the S-Video, or the composite video input/output. MPEG-2 encoder  202  encodes the inputted video data from either the SDI, S-Video, or composite video inputs, into MPEG-2 Part  2  format encoded data. The MPEG-2 format encoded data is then inputted to the IP encapsulator  204  for further processing.  
         [0054]    The invention is further explained by reference to FIG. 4, which is a block diagram of the RF 1  Processing and Control  
         [0055]    Unit  102 . RF 1  Processing and Control Unit  102  is seen to consist of a Monitor and Control Unit  201 , which incorporates means for microprocessor control and monitoring, DC-DC power supply, and a reference frequency source. RF 1  Processing and Control Unit  102  also consists of a Modulator  202 , a 70 MHz to L-band Upconverter  203 , a Transmit Downconverter  204 , a Receive Downconverter  205 , a Rx Splitter  206 , and a Spectrum Analyzer Module  207 .  
         [0056]    Referring to FIGS. 2 and 4, the operation of RF 1  Processing and Control Unit  102  is explained by describing the main signal flow, firstly for the transmit direction. The base band signal from Base Band Unit  101  is applied to Modulator  402  to modulate a 70 MHz Oscillator.  
         [0057]    Modulator  402  can be fully controlled and monitored by the user through a user interface provided in Base Band Unit  101 . The base band signal comprises a transport stream containing the audio, video, and data packets from Base Band Unit  101 , is processed by the Modulator  402  as defined in ETS  300 - 421 .  
         [0058]    The transport stream is randomized in Modulator  402  by combination with a pseudo random binary sequence. The randomizing is performed to ensure sufficient binary transitions and to meet ITU transmitted power requirements. The process encompasses eight frames and then is re-initialized. Sync bytes are not randomized and every eighth sync bit is inverted to provide an initialization signal for the descrambler.  
         [0059]    Following randomization, each packet of the transport stream (including the sync byte) is block coded using a RS (204, 188, 8). Each encoded packet is made up of 1 sync byte, 187 data bytes and 16 bytes of redundancy.  
         [0060]    After block coding, the packets are convolutional-interleaved, creating interleaved frames. The convolutional interleaver maintains periodicity of the coded packet (204 bytes). Interleaving is performed to spread burst errors over many frames and thus improve the performance of the RS code.  
         [0061]    The interleaved frame is then convolutional coded and then punctured to provide inner code rates of ½, ⅔, ¾, ⅚ and ⅞. The base convolutional code is a K=7, rate ½ code. Thus rate ½ inner code does not use puncturing. The outputs of the convolutional coder are applied to I and Q signals.  
         [0062]    The I and Q signals are square root raised cosine filtered. The roll off factor is 0.35. The shaped I and Q signals are QPSK modulated. The mapping of I and Q uses Gray coding and absolute mapping. Modulator  402  may also spectrally invert the QPSK signal if required.  
         [0063]    The modulated 70 MHz output of Modulator  402  is then applied to 70 MHz to L-band Upconverter  403 . Said 70 MHz to L-Band Upconverter  403  utilizes a signal obtained from a reference frequency source in the Monitor and Control Unit  401  to lock its Local Oscillator to be able to accurately upconvert the modulated 70 MHz output from Modulator  402  to the required intermediate frequency range for application to the Interfacility Link  106 .  
         [0064]    In the receive direction, the intermediate frequency receive signal from the Interfacility Link  106  enters the RF 1  Processing and Control Unit  102  and is applied to the Rx Splitter  406 . The Rx Splitter  406  provides two output paths. The main path contains the intermediate frequency receive signal, which passes unmodified to the Baseband Unit  101 . In addition, the Rx Splitter  406  provides an output which is applied to the Rx Downconverter  405 .  
         [0065]    The Rx Downconverter  405  downconverts the incoming intermediate frequency receive signal to receive 25 MHz signal, and forwards the receive 25 MHz signal to the Spectrum Analyzer Module  407 . The reference frequency for this downconversion process is obtained from the Monitor and Control Unit  401 .  
         [0066]    The RF 1  Processing and Control Unit  102  also contains the Tx Downconverter  404 , which receives a sample of the intermediate frequency transmit signal from the Solid-State Power Amplifier  303  (see FIG. 5). Tx Downconverter  404  receives a reference signal from Monitor and Control Unit  401 , to lock its Local Oscillator, which is used to further downconvert the sample of the intermediate frequency transmit signal to produce a transmit 25 MHz signal. This transmit 25 MHz signal is then applied to one input of Spectrum Analyzer Module  407 .  
         [0067]    The Spectrum Analyzer Module  407 , accepts transmit and receive 25 Mhz signals from the transmit downconverter  404  and receive downconverter  405 , respectively. These 25 MHz signals are then forwarded to a Base Band Unit  101  for display on a computer screen (not shown). In the preferred embodiment the following images may be displayed:  
         [0068]    a) a depiction of the received spectrum of a beacon signal, or any other forward link signal capable of providing an indication of the relative power of such a signal (this information can be utilized for the accurate alignment of an associated antenna system);  
         [0069]    b) a depiction of the spectrum of a satellite spectral signature received from a satellite accessed by the apparatus of this invention (this information can be used for verifying the antenna alignment to the desired satellite); and  
         [0070]    c) a depiction of the spectrum of the transmitted signals (this information can be used for the provision of signal level and spectrum sideband information).  
         [0071]    The operation of RF 2  Processing Unit  104  can be explained by reference to FIGS. 2 and 5. In the transmit direction, the intermediate frequency transmit signal from the Interfacility Link  106  enters the Junction/Indicator Box  301 . The output from Junction/Indicator Box  301  is applied to Transmitter  302 A. Transmitter  302 A upconverts the intermediate frequency transmit signal to the desired transmit frequency. The reference frequency for the upconversion is obtained from RF 1  Processing and Control Unit  102  by means of Interfacility Link  106 . The transmit frequency output from Transmitter  302 A is amplified in Solid-State Power Amplifier  303  to a level required for transmission to another terminal or satellite. The output from Solid-State Power Amplifier  303  is applied to OMT/FEED  304 , and thence to the Antenna and Superstructure  105 , by means of which it is transmitted to another terminal or satellite.  
         [0072]    In the receive direction, the receive air-link signal enters the OMT/Feed  304  from the Antenna and Superstructure  105 . The receive air-link signal is then applied to the Low Noise Block Downconverter  305 , where it is downconverted to a intermediate frequency receive signal by means of a Local Oscillator locked to the reference signal obtained from RF 1  Processing and Control Unit  102  via Interfacility Link  106 . The intermediate frequency receive signal output by Low Noise Block Downconverter  305  is connected to the Interfacility Link  106  through the Junction/Indicator Box  301 .  
         [0073]    RF 2  Processing Unit  104  contains additional monitoring and controlling apparatus. A sample of the output of Solid-State Power Amplifier  303  is downconverted to L-band in Block Downconverter  302 B. This L-band signal, known as the Transmit Monitor Signal, is connected to the Interfacility Link  106  and thence to RF 1  Processing and Control Unit  102 , through Junction/Indicator Box  301 .  
         [0074]    It will be apparent that many modifications and variations could be effected by one skilled in the art without departing from the spirit or scope of the novel concepts of the present invention, so that the scope of the invention should be determined by the appended claims only. In the embodiment described, certain frequencies and frequency bands have been used for purposes of illustration. In practise, any frequency or frequency ranges may be utilized, with no departure from the generality of this invention.  
         [0075]    It will be appreciated that the particular type or construction of the various components constituting the apparatus described in this invention are not critical or limiting to either the scope or practice of the present invention. As such, since the hardware implementation of these various components of the present invention will be easily and readily accessible to those skilled in the art of communications systems, these various components have only been referred to generically in the description of the present invention. In this regard, it will become apparent that the novelty of the present invention resides primarily in a unique combination and architectural configuration of these various components in order to create a novel apparatus for transmitting, receiving, monitoring, and controlling the transmit and receive signals required in a terminal used for communications with other terminals in a terrestrial or satellite communications system.  
         [0076]    Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.