Abstract:
A device for detecting RF power information, for use as a stand alone purpose built device, or connectable to an external computing instrument such as a laptop, PDA, or cell phone, or other similarly capable technology. The device scans two or more bands in the wireless frequency and provides output to the user with wireless information about multiple bands of information.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and is a continuation application of U.S. patent application Ser. No. 12/621,187, entitled “MULTIPLE BAND PORTABLE SPECTRUM ANALYZER,” filed on Nov. 18, 2009, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to the field of spectrum analyzers, and more particularly to a mobile device which analyzes multiple bands of RF frequencies. 
     2. Background 
     Wireless networks operating under standard IEEE 802.11, also known as Wi-Fi, are wireless local area network (WLAN) technology commonly used for networking computers together. Wi-Fi can operate in either the 2.4 GHZ Industrial Scientific Medical (ISM) band, or in the 5 GHz band. The 2.4 GHz band is roughly 100 MHz wide. Within that band there are 14 channels that are 22 MHz wide. Due to frequency constraints in the 2.4 GHz ISM band, these Wi-Fi channels overlap each other. The 5 GHz band is 600 MHz wide with 25 channels. Also, the 2.4 and 5 GHz bands share frequencies with a number of other users such as cordless telephones, Bluetooth® devices, ZigBee® devices. To the 802.11 WLAN devices, these other devices may be viewed as interferers. These potential interference sources may cause difficulty with network communications. 
     When setting up a wireless network or troubleshooting network problems, it is necessary to learn what portions of the available radio frequencies, or bands, are free of interfering signals. The test instrument most commonly used for such a task is the spectrum analyzer. A spectrum analyzer scans, or ‘sweeps’ the desired range of frequencies, then normally plots the strengths of the signals received in the vertical axis against the scanned frequencies on the horizontal axis. The result of such a sweep is shown on a graphic display to enable a user to graphically see the spectrum that is analyzed. Spectrum analyzers are specialized test instruments that often cover broad ranges of frequencies. Conventional spectrum analyzers focus on features that enhance the accuracy of measurements, such as: sweep time, principles of the invention, resolution bandwidth and frequency range. These features often require specialized hardware. For instance, conventional spectrum analyzers typically contain dedicated hardware capable of quickly taking precise measurements. This specialized hardware is typically bulky and cost prohibitive for a small scale user, such as a small business, a personal computer user, or highly mobile technical support personnel. Conventional spectrum analyzers also lack certain spectrum display and data manipulation features, creating additional work for a user desiring a particular display or spectrum data manipulation. For example, conventional spectrum analyzers typically graph amplitude versus frequency, requiring users to mentally map channels utilized by devices onto the frequency axis. Furthermore, while conventional spectrum analyzers allow an image to be saved, the image is generally only a representation of a single instant in time. 
     Consequently, it would be desirable to provide a portable and inexpensive device for portable analyzing and troubleshooting the Wi-Fi spectrum. 
     U.S. Pat. No. 7,459,898 to Woodings discloses a System and Apparatus for Detecting and Analyzing a Frequency Spectrum. The apparatus is suitable for spectrum analysis in the 2.4 GHz radio frequency band. The apparatus is a small device that plugs into an available Universal Serial Bus (USB) port of a computing device such as a laptop computer. The result is a highly portable system that includes a 2.4 GHz radio system and hardware to support USB communications. The apparatus together with its companion software, which runs on the connected computer, functions as a spectrum analyzer. The software and the hardware apparatus are operated from the computer&#39;s graphical user interface (GUI). GUI&#39;s are a standard part of modern computer operating systems such as the common Microsoft® Windows operating systems. 
     What is needed is a small, portable, and inexpensive device that will perform spectrum analysis on at least the 2.4 and 5 GHz radio frequency bands. The device should work with a computer that has a GUI, and ideally existing software capable of spectrum analysis and display should be utilized. 
     SUMMARY 
     The invention is a device for detecting and analyzing the frequency spectrum of at least two distinct bands, the 2.4 GHz and 5 GHz bands. One embodiment of the present invention may comprise a portable hardware device including a 2.4 GHz radio system, together with hardware to convert signals in the 5 GHz band down to 2.4 GHz for detection by the 2.4 GHz radio system, thus allowing the device to detect signals in two bands with a single radio, or with two radios both reading the 2.4 GHz band. The radio system detects radio frequency (RF) power present across the scanned band. The device also includes a means to connect and communicate with a computing device, preferably a laptop computer, or possibly a cell phone, PDA, or other portable computing means. One means of communicating with computer is to use a Universal Serial Bus (USB) port and connector. The device should also be suitable for operation with existing software applications designed for radio frequency spectrum analysis. 
     The apparatus of the invention is a device for receiving and detecting radio frequency signals on at least two different bands, the 2.4 GHz and 5 GHz bands, for use with a computing device such as a laptop computer, cell phone, a PDA, or other portable computing devices, or as a stand alone purpose built device. The computing device used with the apparatus of the invention preferably includes a graphical user interface. The device includes a housing in which the components of the device are enclosed. It also includes an antenna which is attached to the housing or may be inside the housing, and is configured for receiving radio frequency signals. Included with one embodiment of the device is a switch for selecting a band of radio frequencies for detection. Once the wireless band is selected, the device is capable of routing signals from that band directly to a radio system for detection, or for sending the signals to a band pass filter. 
     The band pass filter passes signals in the desired frequency band of network signals and rejects all other signals. The device also includes a mixer for converting radio frequency signals to the particular band which may be received by the radio system. In one embodiment of the invention the band received by the radio system is 2.4 GHz. This particular frequency has advantages because radios for detecting this frequency of signals are relatively inexpensive. 
     The mixer in the device may be used to convert 5 GHz signals into 2.4 GHz. This conversion takes place because the preferred radio is a 2.4 GHz radio. By using the band pass filter and the mixer to filter out unwanted signals and convert desired signals to a frequency compatible with a single band radio, more than one band may be analyzed using that single band radio. An oscillator is provided with the device to provide local oscillator input which is required for the mixer to function. 
     The radio system thus includes at least one radio receiver, with that receiver configured to detect RF power in a single RF band. Certain configurations of the device can also perform the same function using two 2.4 GHz radios, with one receiving the 2.4 GHz band directly, and one receiving the 5 GHz band stepped down to 2.4 GHz. 
     A connector is provided which may be a USB connector for attaching the device to a computer, or could be other types of conventional connecters to attach to the preferred computing device, such as cables and connectors for PDAs and cell phones. The connector device allows the physical attachment of the device to the computing device, and provides for transfer of the commands and data between the computing device and the apparatus of the invention. The apparatus may also be powered through the connector. 
     The apparatus is thus configured to detect RF power on two or more radio frequency bands with the device configured to utilize radios capable of detection of only one band, but with the data input to the one or more radios being converted from other bands. The device would be configured to be switchable between reading a first band and a second band. The user may manually select a band or configure the device to automatically switch between the bands. When the device is switched to reading a first band, information about that selected band is displayed in the graphical user interface of the computing device. It is also possible for data about both bands to be displayed simultaneously, either from both bands being read simultaneously or sequentially as the device is switched from one band to the other. 
     The oscillator is a voltage controlled oscillator in which the output frequency is controlled by the micro-controller included in the radio system. The voltage controlled oscillator frequency may be varied to allow a narrow band radio to detect RF power across a broad band. 
     An additional embodiment of the present invention is a method for detecting and analyzing RF power on selected radio frequency bands. The method may comprise the following: 1) providing a small hardware device, which may comprise a radio system, a micro-controller, and memory, and be suitable for detecting RF power across frequency spectrum; 2) providing a computing device with a graphical user interface; 3) providing spectrum analysis software suitable for operation with the small hardware device; 4) connecting the small hardware device to the computing device; 5) selecting a wireless frequency band for spectrum analysis; 6) detecting RF power across the selected band; 7) transferring data to a computing device; 8) providing a graphical display of detected RF power across the selected band. The radio system is made up of one or more radios of a selected frequency such as 2.4 GHz radios. The system utilizes single band radio or radios to analyze two or more RF bands. 
     This invention is also a method for detecting and analyzing the frequency spectrum of at least two distinct bands using a portable device which incorporates one or more radios which are configured to analyze only one band. Typically, the radios would be one or more radios which detect and analyze signals in the 2.4 GHz band, but the method of the device results in using those radios to detect and analyze both 2.4 GHz and the 5 GHz bands, and other bands are additionally possible. The method involves the steps of connecting the portable device to a computing device. The next step is to receive RF signals at the portable device antenna. The antenna can be internal to the housing of the device, or it can be an external component of the device. The next step is to provide within the device a switch for selecting which band of radio frequency signals are to be analyzed by the device. If the 2.4 GHz band is to be detected, the switch would be positioned to route the signals directly to a radio system. If, for instance, the 5 GHz band is selected for detection, the switch would be set to route the signals to a band pass filter, which will only pass signals in the desired band. Next the signals passed by the band pass filter are routed to a mixer. In the mixer, signals from the band pass filter are combined with signals from the oscillator for conversion to the band received by the radio. This step is accomplished by adjusting the oscillator output so the mixer output is converted to be compatible with the radio. For example, the mixer step may result in 5 GHz signals being mixed with signals from the oscillator for down conversion to 2.4 GHz for analysis by a 2.4 GHz radio. 
     The next step of the method is providing a connecter which allows the device to connect to a computing device. The computing device can be a laptop computer, a PDA, a cell phone, or other portable computing devices. The connecter can be a USB connection or other connecters normally used in the industry at present, or those which may become standard connecting devices in the future. 
     The method of the invention can also comprise the step of providing a second radio, with the signals from the switch being routed to either the first radio or the second radio. Both the first radio and the second radio are configured to operate on the 2.4 GHz band, with RF power signals in the 2.4 GHz band being routed directly to the second radio, and being routed to the first radio after first being down converted from the 5 GHz band into the 2.4 GHz band. 
     The purpose of the Abstract is to enable the public, and especially the scientists, engineers, and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection, the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. 
     Still other features and advantages of the claimed invention will become readily apparent to those skilled in this art from the following detailed description describing preferred embodiments of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiments are to be regarded as illustrative in nature, and not as restrictive in nature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of the present invention. 
         FIG. 2  is a block diagram of one embodiment of the present invention. 
         FIG. 3  is a block diagram of a second embodiment of the present invention. 
         FIG. 4  is a block diagram of a radio system used in the present invention. 
         FIG. 5  is a block diagram of the preferred embodiment of the present invention. 
         FIG. 6  is a flow chart of the method of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the invention is susceptible of various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims. In the following description and in the figures, like elements are identified with like reference numerals. The use of “e.g.,” “etc,” and “or” indicates non-exclusive alternatives without limitation unless otherwise noted. The use of “including” means “including, but not limited to,” unless otherwise noted. 
       FIG. 1  is a perspective view of the apparatus for detecting and analyzing a frequency spectrum  10  is shown. The device includes a housing  12  to contain the circuitry and components of the apparatus. Antenna  14  is mounted to the internal board and may be inside or outside the housing. Connector  16  allows the apparatus to be plugged into an available port on a computing device. The computing device can be a laptop computer, or other computing device types could be utilized such as a cell phone, a PDA, or other computing means. Although a USB connecter is shown in  FIG. 1 , other types of connectors could also be utilized with the device when connecting to different types of computing devices. Connector  16  may be a common type such as a USB connector or other common serial or parallel port connecters. While the antenna  14  shown in  FIG. 1  is external to the housing, an internal antenna, however, may be used and located inside the apparatus housing  12 . The apparatus housing  12  is a small device to facilitate ease of portable use. 
     Referring now to  FIG. 2 , an embodiment of the present invention is illustrated. Antenna  14  for receiving signals is connected to a switch  18 . This embodiment of the present invention includes two switches  18 . One switch  18  is connected to the antenna; the second switch  18  is connected to the radio  32 . The switches can be set to route signals from the antenna directly to the radio  32  or to a band pass filter  22 . In the preferred embodiment the radio  32  is a 2.4 GHz radio, which receives signals in the 2.4 GHz band. If the signals to be analyzed are in the 2.4 GHz band received by the radio  32  they may be routed directly to the radio  32 . If the signals to be analyzed are not in the band directly received by the radio  32 , switches  18  are positioned to route those signals to band pass filter  22 . Band pass filter  22  allows only signals in a selected band to pass on to the RF input of mixer  24 . Oscillator  26  provides a signal to the local oscillator input of mixer  24 . In the mixer  24  the signal at the RF input is mathematically multiplied together with the signal at the local oscillator input of the mixer  24 , the mixer  24  creates an intermediate frequency signal output. The intermediate frequency signal has two component frequencies: 1) a down converted signal with a frequency equal to the RF input frequency minus the local oscillator frequency, and 2) an up converted signal with a frequency equal to the RF input frequency plus the local oscillator frequency. If for instance, radio  32  receives signals in the 2.4 GHz band and it is desired to use that radio  32  to analyze 5 GHz signals, the 5 GHz signals would be converted down to 2.4 GHz by the mixer  24 , with input from the oscillator  26 . The oscillator input to the mixer  24  is determined by the difference of the frequency desired to be received and the frequency received by the radio system. 
     By way of an example, if radio  32  receives 2.4 GHz signals and it is desired to receive signals from the 5 GHz band, signals from antenna  14  are routed through switch  18  to band pass filter  22 . The band pass filter  22  would be designed to pass only signals in the 5 GHz band, any received 5 GHz signals will pass to the RF input of mixer  24 . Oscillator  26  would be set to produce a signal that is 2.6 GHz and that 2.6 GHz signal is available at the local oscillator input of mixer  24 . When mixer  24  processes the 5 GHz input signal and the 2.6 GHz local oscillator signal the resulting frequencies are 5−2.6 or 2.4 GHz and 5+2.6 or 7.6 GHz. The 2.4 GHz down converted signal output from intermediate frequency output of mixer  24  is sent to radio  32  through the second switch  18  to radio  32  where RF power on the down converted signal is detected. 
     Connector  16  allows the apparatus to be connected to a computer. The connection provided through connecter  16  may supply power to the apparatus  10  as well as facilitating the exchange of data and commands between the apparatus  10  and the connected computer. Detected RF power data from radio  32  is processed by micro-controller  34  for transfer to the connected computer through connector  16 . 
     Connector  16  maybe also be a fixed or semi-fixed type connector whereby the apparatus is connected to, or integrated into a portable computing device. The combination of the apparatus integrated with a portable computing device is a custom handheld apparatus for detecting and analyzing a frequency spectrum. 
       FIG. 3  is a block diagram illustrating another embodiment of the present invention. This embodiment includes an antenna  14 , switch  18 , connector  16 , band pass filter  22 , mixer  24 , and oscillator  26 . In this embodiment, two radio systems are used. A first radio system  28  includes at least a receiver. An example of a radio that may be used as a first radio system  28  is a Texas Instruments CC2500 radio which receives signals in the 2.4 GHz band. A second radio system that includes at least a radio  32 , a micro-controller  34 , memory  36 , and support hardware for a communications port  38 . An example of a second radio system is a Texas Instruments CC2511 2.4 GHz radio system. In particular, the second radio system on this embodiment may include a USB port to allow connection with virtually all modern personal computing devices. 
     In operation, the embodiment shown in  FIG. 3  includes antenna  14  to receive signals, and switch  18  is set to route the signals to the first radio  28  or to the band pass filter  22 . If signals in the 2.4 GHz band are to be analyzed, switch  18  is set to route signals to first radio  28 . The first radio receiver detects RF power in the 2.4 GHz band. The data detected by the first radio  28  includes a measure of relative RF power present across the analyzed band. The data from the first radio  28  is routed to second radio system micro-controller  34 . Second radio system micro-controller  34  transfers the detected information transferred from the first radio system  28  to the connected computing device through connector  16 . If it is desired to detect signals other than 2.4 GHz, switch  18  is set to route signals to the band pass filter  22 . Band pass filter  22  is designed to pass signals in the desired band. As described in the discussion of  FIG. 2 , the oscillator  26  provides a local oscillator signal to the mixer  24 . Mixer  24  then converts the received signals to 2.4 GHz for detection by the radio  32  of the second radio system. Detected data is then transferred through micro-controller  34  and is made available to the connected computer through connector  16 . 
     If it is desired to simultaneously scan both bands, switch  18  would be alternately set to route signals to first radio  28  then to band pass filter  22  for analysis. In this manner two bands may be analyzed simultaneously by sharing antenna  14 . To accomplish this simultaneous analysis of two bands, switch  18  would be controlled from the connected computing device using the graphic user interface to command the needed automatic switch  18  operation. 
       FIG. 4  illustrates a block diagram of the major components of radio system  30 . The radio system  30  includes at least a radio  32 . That radio is comprised of at least a receiver and in the preferred embodiment the radio is a 2.4 GHz transceiver. The second radio system also includes a micro-controller  34 , memory  36 , and hardware to support a USB port connection  38 . The radio system  30  of  FIG. 4  would be utilized in the devices of  FIGS. 2 ,  3  and  5 . 
     Referring now to  FIG. 5  a block diagram of the preferred embodiment is shown. The preferred embodiment is designed to detect and analyze signals in the 2.4 and 5 GHz radio frequency bands. This embodiment includes an antenna  14 , and switch  18 . In this embodiment, switch  18  is a solid state switch controlled by the micro-controller  34  in the second radio system. Switch  18  can be set to route signals received at antenna  14  to either first radio system  28 , or to first band pass filter  40 . When the switch is set to route signals to the first radio system  28  the detector in the first radio system  28  detects RF power in the 2.4 GHz radio frequency band received by the antenna. Detected 2.4 GHz information is transferred to the micro-controller  34  of the second radio system where it can be processed and transferred to a connected computer through connecter  16 . 
     If it is desired to detect and analyze 5 GHz signals, switch  18  is set to route signals received by the antenna  14  to the first band pass filter  40 . The radio frequency signals from first band pass filter  40  are sent to a first amplifier  42 . The first amplifier  42  is a low noise amplifier with the function of restoring signal strength lost due to attenuation in first band pass filter  40 , without corrupting the signal to be analyzed. From first amplifier  42  the signal is sent to the RF input of mixer  24 . Oscillator  26  produces a local oscillator signal for use with mixer  24 . In this embodiment, the oscillator  24  is an integrated voltage controlled oscillator and phase locked loop. Second band pass filters  44  remove unwanted noise from the oscillator  26  output. Second amplifiers  46  increase the amplitude of the local oscillator signal for use by the mixer  24 . In the preferred embodiment there are three stages of second band pass filters  44  and two second amplifiers  46 . Selection of alternate filters or amplifiers may increase or decrease the number of filter and amplifier stages required to present a local oscillator signal of the desired quality and strength to the local oscillator input of mixer  26 . Integrated oscillator  26  is controlled by the micro-controller  34  in the second radio system. 
     The second radio system includes a 2.4 GHz radio  32  which receives wireless signals and detects RF power in the 2.4 GHz band. Therefore, the 5 GHz wireless radio signals received at the antenna and routed through switch  18  to first band pass filter  40  are converted down in the mixer to 2.4 GHz for detection by radio  32  in the second radio system. To detect signals across the 600 MHz wide band 5 GHz RF band with a 2.4 GHz radio that operates in a 100 MHz wide RF band, the local oscillator signal presented to mixer  24  is sequentially stepped 100 MHz at a time so that the intermediate frequency output from mixer  24  presents, in a piece wise fashion, the 600 MHz wide frequency spectrum of the 5 GHz radio frequency band to the 100 MHz wide 2.4 GHz receiver. In an alternate embodiment the output signal from oscillator  26  could be swept continuously across the 600 MHz wide local oscillator frequency required to down convert the 5 GHz radio frequency band for detection in the 2.4 GHz radio  32 . Detected information is sent to the computing device by way of connector  16 . The piece wise data detected by the 2.4 GHz radio  32  is processed for display on the connected computing device as a continuous 5 GHz radio frequency band spectrum if desired. 
     The method for detecting and analyzing the frequency spectrum of at least two distinct bands using a portable device is shown in  FIG. 6 . The method  60  involves using a portable RF power signal analyzer to analyze multiple RF bands. The method  60  begins with the step of connecting the portable device to a computing device  62 . The next step in method  60  is the step of receiving RF power signals at the antenna of the portable device  64 . From that point the method diverges into one of the embodiments shown in  FIG. 6 . One embodiment involves use of a device with a single radio  66 , and another embodiment involves use of a device with two radios  68 . Each of these embodiments analyzes the 2.4 and the 5 GHz bands. 
     In the one radio embodiment  66 , the switch is used to select a band to be analyzed  70 . To analyze 2.4 GHz signals, the switch is set to route 2.4 GHz band signals to the radio  72 . After routing to the radio, the next step is using the 2.4 GHz radio to analyze RF power in the 2.4 GHz band  74 . The results of analysis are graphically displayed on the computing device to which the portable device is attached  76 . Attachment would typically be a USB port, but other connection protocols and devices may also be utilized as they become available in the industry. 
     As an alternative to reading the 2.4 GHz band, the switch may be set to route 5 GHz signals to the band pass filter  78 . The band pass filter  80  only passes signals in the 5 GHz band. 5 GHz signals are the routed to the mixer  82 . The oscillator is adjusted to provide signal to the mixer such that the mixer down converts the 5 GHz signals to 2.4 GHz  84 . The next step is analyzing the 2.4 GHz down converted signals from the mixer to the 2.4 GHz radio  74 . The step after analysis is displaying the result graphically on the computing device to which the portable device is attached  76 . 
     In the case of a two radio embodiment  68 , the switch is used to select either the 2.4 GHz or 5 GHz band for analysis  86 . If the 2.4 GHz signals are selected to be analyzed first, the next step is routing the 2.4 GHz signal from the antenna to one of the two 2.4 GHz radios  88 . That radio is designated as the second radio  98 . The second radio  98  is a 2.4 GHz radio which analyzes RF power signals in the 2.4 GHz band. Results of the analysis of the 2.4 GHz band are displayed on the graphic display of the computing device  76 . 
     After analyzing the information for the 2.4 GHz band, the next step is to adjust the switch to select the 5 GHz band  86 . Then, the next step is to route the 5 GHz signal to the band pass filter  90 . In the band pass filter step  92 , all but the 5 GHz signals are removed, then the 5 GHz signals are routed to the mixer  94 . The oscillator is adjusted to provide a signal to the mixer so the mixer down converts the 5 GHz signals to 2.4 GHz  96 . From the mixer the 2.4 GHz band is routed to another 2.4 GHz radio, designated the first radio  100 , which then analyzes RF power in the 5 GHz band. Following analysis in the first radio  100 , results are passed on to the computing device for graphic display  76 . 
     While there is shown and described the present preferred embodiment of the invention, it is to be distinctly understood that this invention is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the invention as defined by the following claims.