Abstract:
A receiver for receiving a broadcast channel comprising a spectrum analyzer physically integrated into the receiver and operative to receive an intermediate frequency signal and process the spectral contents of the receive signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/710,833, filed Aug. 24, 2005, the disclosure of which is hereby incorporated herein by reference. 

   BACKGROUND 
   The frequency band that the broadcasters use for electronic news gathering (ENG) is transitioning from 17 MHz bandwidth channels to 12 MHz bandwidth channels. To maintain a substantially consistent level of quality, the current analog FM modulation scheme will be changed to a digital modulation scheme. The current workflow for establishing and maintaining a link between antennas typically requires aligning a simplex link using verbal feedback from the receive site back to the transmitter site. The feedback is usually provided by having an operator at a transmit site make a voice connection using 2-way radio or cell phone. The operator then performs initial antenna alignment in the analog FM domain using feedback from another operator at a receive antenna. Once antenna alignment is confirmed in the analog domain, a switch is then made to digital modulation. This process works adequately in a static environment. Once in the digital mode it is typically impossible to detect the presence of an adjacent channel transmitter that may cause interference until the picture starts to breakup or the BER deteriorates. By then, however, it is usually too late. When this occurs the user must switch back to analog mode to diagnose the problem. 
   In general, there are no tools currently available to adequately assist the operator in diagnosing link reliability issues in the digital mode. A solution that has been proposed and implemented is to add a spectrum analyzer to the 70 MHz intermediate frequency (IF) output of the receiver. This has proven to be a viable solution for isolating or identifying only a few problems related to on channel or co-channel interference. Such problems are incorrect modulation type of the transmitter or co-channel interference. 
     FIG. 1  is a diagram that illustrates a standard system configuration  100 . As shown, a radio frequency (RF) signal  110  is received and amplified with an amplifier (LNA)  116 . This signal is then down converted from the received RF frequency to a first IF frequency typically using a mixer  118  and synthesizer  122 . The signal is then filtered with a wide band pass filter  126 . The frequency of this first conversion is generally in the 800 MHz range. The specific frequency may vary based on the manufacturer&#39;s architecture. The signal is then further amplified at amplifier  130  and further down converted to a second IF frequency using mixer  134  and synthesizer  138 . This is typically 140 or 70 MHz but not limited to these frequencies. The signal, now at a lower frequency, can be further filtered via filter  142  to remove adjacent channel signals located above and below the desired channel. After the filter  142 , which is typically a narrow band-pass filter, the signal is usually further amplified using amplifier  146 , i.e., automatic gain control (AGC), and applied to a demodulator  150  to recreate the original signal transmitted. Manufacturers of receivers will often provide an auxiliary IF output  156  for monitoring purposes. In this system architecture, a spectrum analyzer  160  can be connected external to the IF monitor point  156 . 
   The system of  FIG. 1  has generally been deployed and used to conduct link reliability analysis. The architecture of  FIG. 1  has not, however, proven to be optimal for diagnosing the majority of link conditions that lead to link failure or reduce link reliability. A reason the aforementioned architecture is flawed is that many problems cannot be detected after filtering and after AGC amplification. Specifically, most interfering signals cannot be detected unless the transmitter is placed into standby mode, which results in the inability to see some types of adjacent or co-channel interference. Furthermore, when the transmitter is placed in standby mode, it is also very difficult to diagnose link problems because the AGC circuit in the receiver brings the noise floor or interference up to a level similar to the desired signal thereby disguising the real problem. This can cause operators or maintenance personnel to become confused and further complicate their job. 
   One place to monitor the link spectrum would be at the RF input. In this way, the full spectrum can be viewed relative the power levels of the channels of interest. But this architecture is relatively expensive as it duplicates the LNA and synthesizer circuitry. This method may also reduce the receiver&#39;s sensitivity because power intended for the receiver will be diverted to the spectrum analyzer. 
   SUMMARY 
   As is further described in detail below, an aspect of the present invention is a receiver for receiving a broadcast channel comprising a spectrum analyzer integrated into the receiver and operative to receive an intermediate frequency signal and process the spectral contents of the receive signal. 
   In accordance with this aspect of the present invention, the intermediate frequency signal comprises a portion of a signal that results from a first down conversion of a radio frequency signal inputted into the receiver. Most preferably, the intermediate frequency signal is at a frequency of 800 MHz. 
   Further in accordance with this aspect of the present invention, the intermediate frequency signal may comprise a portion of a signal that results from a second down conversion of a radio frequency signal inputted into the receiver. Most preferably, this intermediate frequency signal is at a frequency of 70 MHz, but may also be at a frequency of 140 MHz. 
   In another aspect of the present invention, a broadcast receiver is provided. The receiver preferably comprises a spectrum analyzer that is physically integrated into the receiver and operative to receive an intermediate frequency signal and process the spectral contents of the receive signal. 
   In another aspect of the present invention, a broadcast receiver is provided. The receiver preferably comprises a spectrum analyzer that is externally integrated with the receiver and operative to receive an intermediate frequency signal and process the spectral contents of the receive signal. The externally integrated spectrum analyzer may desirably process a signal having a frequency of 800, 140 or 70 MHz. 
   In another aspect, the present invention is a system for performing antenna alignment in a broadcast system. The system preferably comprises a receiver having a spectrum analyzer integrated therein, a remote control unit connected to the receiver and operative to receive spectral data processed by the spectrum analyzer and a controller for processing the spectral data. Most preferably, the controller is connected to the remote control unit, although in some embodiments processing may be done at the remote control unit. 
   In accordance with this aspect of the present invention, the spectrum analyzer may be physically integrated into the receiver. Further in accordance with this aspect of the present invention, the spectrum analyzer is externally connected to the receiver. 
   Further in accordance with this aspect of the present invention, the spectrum analyzer is adapted to receive a signal selected from the group consisting of 800 MHz, 140 MHz or 70 MHz. 
   A further aspect of the present invention is a receiver for processing a broadcast signal. The receiver preferably comprises a first amplifier for amplifying a radio frequency signal; a mixer and synthesizer for down converting the amplified signal to a first intermediate frequency signal; and a spectrum analyzer integrated in the receiver for receiving a portion of the first intermediate frequency signal. In accordance with this aspect of the present invention, the first intermediate frequency signal of the receiver comprises a digital signal centered at a frequency of substantially 800 MHz. 
   Further in accordance with this aspect of the present invention, the radio frequency signal comprises a signal having a frequency of at least 2.0 GHz. Further still, the radio frequency signal comprises a signal that is less than 2.7 GHz. Yet further still, the synthesizer may desirably comprise a local oscillator having a frequency between 2.810 and 3.510 GHz. 
   Further in accordance with this aspect of the present invention, the receiver further preferably comprises a data port for communicating data signals associated with the digital signal. In addition, the data port is preferably selected from an interface selected from the group consisting of an RS232 or universal serial bus interface. 
   In another aspect, the present invention comprises a system for aligning a radio antenna for a radio frequency broadcast signal, comprising: a receiver operable to receive the radio frequency signal and to produce an intermediate frequency signal having a frequency of approximately 800 MHz from the radio frequency signal; a remote control unit having a spectrum analyzer and adapted to receive the 800 MHz signal and data signals associated with the bit error ratio and receive level of the radio frequency signal, the remote control unit being further adapted to display a spectral content of the 800 MHz signal. 
   In addition, the foregoing aspects of the present invention may be implemented in any wireless system or in a portable receiver. The foregoing aspects of the present invention may also be implemented in a broadcast receiver operable to receive RF signals in the 2 GHz or 7 GHz frequency bands. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustratively depicts a conventional system used for determining link reliability. 
       FIG. 2  illustratively depicts a receiver in accordance with an aspect of the present invention. 
       FIG. 3  illustratively depicts a receiver in accordance with an aspect of the present invention. 
       FIG. 4  illustratively depicts a system in accordance with an aspect of the present invention. 
       FIG. 4A  illustratively depicts a circuit schematic of a receiver in accordance with a further aspect of the present invention. 
       FIG. 5  illustratively depicts a system in accordance with an aspect of the present invention. 
       FIG. 6  illustratively depicts a system in accordance with an aspect of the present invention. 
   

   DESCRIPTION 
   In accordance with an aspect of the present invention, a spectrum analyzer is integrated into the architecture of broadcast receiver. Such a receiver is adapted to receive ENG broadcast signals. In accordance with this aspect of the present invention, a more cost effective way for performing antenna alignment and perform spectrum analysis of the broadcast channel is provided. This aspect of the present invention advantageously does not require duplication of a receiver&#39;s amplifier and synthesizer circuitry. Functionally, this aspect of the present invention generally comprises placing a spectrum analyzer (SA) just after the first conversion circuit but prior to the first band pass filter. Note, however, that the signal may also be detected after the first band pass filter.  FIG. 2  shows such a receiver  200  in accordance with an aspect of the present invention. As shown, the receiver  200  includes a first amplifier  210 , which amplifies an RF signal received from a transmitter (not shown). The signal from the first amplifier  210  is then mixed down to a first IF signal  216  using a mixer  218  and synthesizer  220 . Circuitry  224  for a spectrum analyzer or operable to perform spectrum analysis is integrated into the receiver  200  and a portion  226  of the first IF signal  216  is then fed to the circuitry  224 . In the preferred embodiment, the synthesizer  220  is operable as a local oscillator having a frequency range of 2.810 to 3.510 GHz, assuming that the frequency range of the RF input signal is between 2.0 GHz to 2.7 GHz. Thus, when these two signals are mixed, the frequency of the resulting IF signal is the difference−810 MHz. 
   The circuitry  224  provides the feature that allows for visual indication of the received signals on a selected or desired channel in addition to other signals (i.e., unwanted signals) that may be present on adjacent channels. This allows an operator to view the spectrum of the broadcast signal. The remaining portion of the first IF signal is then coupled to a bandpass filter  230 , amplified by amplifier  236  and further mixed down using synthesizer  244  to product a second IF signal. That second IF signal is filtered by filter  248 , amplified using amplifier  250  and demodulated using demodulator  254 . 
   The spectrum analyzer  224  may be implemented using a sweeping oscillator or digitally using a fast-Fourier transform (FFT) techniques. In addition, the receiver  200  may be adapted so that an operator may be able to view the spectral output on the receiver or via a display or monitor. 
   There are a number of benefits to doing the spectrum monitoring on the first IF signal  216 . First, the spectrum analyzer utilizes the receivers LNA and synthesizer reducing the required RF hardware. In addition, the affects caused by the amplifier  210  and mixer  218  can be monitored. A problem that occurs in simplex systems is receiver overload. This occurs when a very strong signal, either on channel or on an adjacent channel saturates the amplifier, e.g., LNA  210 , causing the desired signal to be destroyed. By monitoring the spectrum just after the LNA  210  and down converting mixer  218  it can be easily determined if the LNA or mixer is being saturated by the desired or undesired signal. Placing the spectrum analyzer at the output of the LNA and mixer also does not affect the receiver sensitivity. 
   Other variants of the configuration shown in  FIG. 2  may be implemented in accordance with further aspects of the present invention. For example, in  FIG. 3 , a receiver  300  is shown which is similar to receiver  200  except that the spectrum analyzer functionality  320  is performed outside the receiver. Thus, the receiver  300  provides the proper output required for spectrum analysis. In the regard, a spectrum analyzer may be used by an operator to view spectrum and perform link reliability analysis. 
   In accordance with an additional aspect of the present invention, since the spectrum analyzer may be implemented as an integral part of the receiver and/or receiver system, spectrum data can be transmitted over a communication channel back to a master control site. Remote control systems have been used in the past to control the receiver and antenna system. In such systems, typically only bit error ratio (BER) and receive levels have been returned to the control center to aid in the alignment of the antennas. In accordance with this aspect of the present invention, an integrated spectrum analyzer at the receiver may send spectrum data back to the control center. This spectral data may be used in conjunction with the BER and receive levels to monitor system perform. For example, that spectrum data then can be used to aid in the alignment of the antenna along with other data that may be available. This also advantageously allows the operator to maintain a reliable link. 
   The spectrum analyzer output may be used in conjunction with an overlay mask that prescribes the boundaries for the mask. This mask would preferably server as a spectral mask. Using the mask, an operator would be able to tell when antenna alignment is achieved by determining whether the spectrum of the transmitted signal lies within the boundaries of the mask. Alternatively, the output of the spectrum analyzer may be compared to a threshold line indicator. For example, the indicator may demark a region that the spectra should be limited to. 
     FIG. 4  shows a system  400  in accordance with this aspect of the present invention. In particular, the system  400  includes a receiver  410 , which includes a spectrum analyzer  416  integrated therein. The receiver  410  communicates with a remote control unit (RCU)  426  over a communication link  432 . The communication link  432  may be an RS232 or USB link, but may also use other technologies. The RCU  426  is also connected to a master controller  440  over a data communications link  442 . Link  442  may be the same as link  432  or may use one of the other technologies distinct from link  432 . A console or monitor  450  is further connected to master controller  440  and used by the operator view data relating to the receiver  410 . In accordance with this aspect of the present invention, during antenna alignment spectral data captured by analyzer  416  is transmitted over the links  432  and  442  to master controller  440 . The data may be then viewed on console  450  and used by an operator to align the antenna associated with the receiver. 
   In the embodiment shown in  FIG. 4 , further processing of the 800 MHz IF signal may be performed to allow the spectral data associated with that signal to be sent over the link  432 . In particular, with reference to  FIG. 4A , the 810 MHz signal  226  spilt off from the output of the mixer  218  (see  FIG. 2 ) is preferably fed to an amplifier  460  for level restoration and noise suppression. The output from the amplifier  460  is then fed to a microprocessor controlled attenuator  464  that is used for level control to properly scale the signal. The signal is then amplified by amplifier  468 . The signal is then mixed in mixer  472  with local signal having a frequency of approximately 1040 MHz. Therefore, the resultant signal is at a frequency of approximately 230 MHz. The signal is then transformed from an unbalanced to balanced or differential signal in transformer  476 . The resulting differential signal is further filtered and amplified at block  480  before converted to a digital signal by analog-to-digital converter  482 . That signal is then fed to microprocessor  484 . The output from microprocessor  484  is used to drive and control the signals appearing on link  432 . With regard to the signal associated with the spectral content of the channel, it contains the frequency and power level of the signal that appears in the 12 MHz bandwidth of the channel of interest. In addition, it also contains the frequency components of the 10 MHz wide channels on either side of the 12 MHz channel. The RS232 signal may then be provided a personal computer so that the spectrum of the channel can be viewed. This additional processing may be integrated into the receiver and viewed via a display connected to the receiver or provided on the receiver itself. 
     FIG. 5  shows a variant of the system  400  in accordance with a further aspect of the present invention. In  FIG. 5 , the system  500  includes a spectrum analyzer  510  that is physically located outside the receiver and connected to the first IF signal (see  FIG. 2 ). In this system, the receiver  530  desirably includes an output connector that provides the first IF signal  520  centered around approximately 800 MHz. The spectrum analyzer  510  receives the signal  520  and outputs it as data on port  540 . Port  540  may comprise an RS232 or USB port. The receiver  530  also includes a similar port  534 , which preferably outputs data such as the receive signal level and BER. The data signals from ports  540 ,  544  are then fed to an RCU. The RCU  550  then forwards this data to a master controller  560 . The master controller  560  preferably communicates with the RCU  550  via an RS232 link. That link may however also comprise an USB link. An operator at terminal  564  may then use the data to perform antenna alignment. 
   In a further variant, the RCU  550  of  FIG. 5  may include the spectrum analysis or viewing capability. In particular, a spectrum analyzer  510 ′ may be integrated into the RCU  550 . An IF signal  520 ′ centered at approximately 800 MHz may then be fed to the RCU  550 . The RCU may then relay the content of the spectral data associated with signal  520 ′ over the data link between it and the master controller  560 . The additional data signals from port  544  (e.g., power levels) would still be provided via port  544  on the receiver  530  over an RS232 or USB link to the RCU  550 . 
     FIG. 6  is representative of an additional system  600  where the spectrum analyzer  610  is physically located outside the receiver but connected to the second IF signal (see  FIG. 2 ) at 70 or 140 MHz. Although the system of  FIG. 6  provides an output at the second IF signal, that signal is advantageously integrated into the workflow. Specifically, the signal from the spectrum analyzer is forwarded to the master controller  620  by the RCU  624 . Therefore, although the operator won&#39;t be able to tell as much about he spectral content of neighboring or adjacent signal, spectral analysis is integrated into the system. Thus, spectral analysis is integrated into the workflow. 
   In particular, the workflow for aligning antennas in the conventional system included first turning off the analog transmitter. Next, operators or maintenance personnel at the local and remote sites (e.g., transmitter and receiver or vice versa) would talk to each other as they align the antenna. This procedure is still used even with the deployment of digital systems. That is, analog is first performed and the digital signal is then switched on. This process is not dynamic and offers no guarantee that digital transmission will perform as expected when the switch is made to digital. 
   In contrast, the integrated spectrum analysis procedure and system described in accordance with an aspect of the present invention is dynamic. It takes the guessing out the alignment process as it allows the operator to see neighboring or adjacent channels. Thus, it allows the operator to get a sense of whether co-channel interference exist. This system also is more suitable to the ENG environment involving moving trucks or antennas. Using the old workflow, alignment in the analog domain would not account for the scenario where a neighboring digital signal would clip the signal whose antenna is to be aligned. In accordance with the foregoing aspects of the present invention, the unwanted, or interfering channel, is shown adjacent to the center channel or channel of interest. In addition, the process in simplified and less dependent on the skill or experience of the operator to spot unusual artifacts in the spectrum. 
   For example, as is generally known in the art, in conventional systems the operator had to be trained to spot ghosts or one signal hidden by another. The system and procedures of the present invention advantageously allows an operator to readily identify potential interfering signals by looking at neighboring channels on an spectral trace. 
   Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.