Abstract:
Systems and methods include up-converting a UWB frequency pulse from a UWB radar unit to a V band frequency pulse; transmitting the V band frequency pulse via an active array antenna; receiving a V band echo pulse via the active array antenna; down-converting the V band echo pulse from the active array antenna to a UWB pulse; and feeding the UWB pulse to the UWB radar unit for processing by the UWB radar unit. A V band antenna system includes: an antenna board that defines an antenna plane being the plane of the board and comprising a plurality of antenna elements; a mother board providing a corporate combining feed to the antenna board; and a power management board to which the antenna board and mother board are mounted perpendicularly to the antenna plane, wherein the antenna elements provide a beam forming antenna for ultra wide band pulses at V band frequencies.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/158,301, filed Mar. 6, 2009, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present disclosure generally relates to radio frequency (RF) detection and ranging and, more particularly, to miniaturization of handheld radar units to make them more practical for particular types of use. 
     Portable, handheld radars have been used for detection of hidden objects, e.g., objects such as weapons or people hidden behind a wall of a building. it may be desirable to be able to detect hidden objects in many situations, including for example, constitutionally supported government agency investigation of a premises containing buildings of unknown internal configuration, military intelligence scenarios, and fire and rescue situations. Ultra wideband (UWB) radar systems have shown a high degree of fitness for such types of use. 
     UWB impulse radar systems utilize pulse widths on the order of hundreds of picoseconds (trillionth of a second). Because such short pulses necessarily have very few cycles or even a single cycle of RF signal (such as a Gaussian monopulse), UWB radars may be considered to operate in the time domain as opposed to conventional frequency domain processing of received pulses. This time domain operation enables UWB radars to enjoy very fine range resolutions such as on the order of a fraction of a few feet or less. In addition, UWB radars have high power efficiency because of their low transmit duty cycle. Furthermore, UWB radars provide users with a very low probability of detection because their transmitted pulses occupy a relatively large bandwidth and thus have low power spectral density. 
     Some UWB impulse systems having a 5 GHz center frequency of the RF signal, even though being capable of handheld operation, have an antenna that may be larger and more bulky than desirable for effective use in some situations. Typical systems have focused on narrow band solutions (in contrast to ultra wideband) at higher frequencies. The same principle is applicable to UWB communication systems. As with radar systems, a virtual beam forming mechanism could be applied to omni-directional communication protocols and transform the communication system into a narrow beam width line of sight millimeter wave communication system. Again, the benefit of using virtual beam forming instead of actual physical beam forming would be the size of the antenna system and the fact that in lower RF frequencies where most of the omni-directional wireless systems are working—such as wireless USB or UWB wireless PAN (personal area networks) networks—actual beam forming is not practical or desirable. As can be inferred from the foregoing, there is a need to provide a handheld UWB radar unit using existing 5 GHz UWB radars and having a reduced antenna size not practical with a 5 GHz RF center frequency. 
     SUMMARY 
     According to one embodiment, a system includes: a radar unit having a center frequency in the UWB (ultra wide band) radar band; a transmit module connected to a radar impulse output of the UWB radar unit, the transmit module producing V band frequencies that are up-converted from the UWB input from the radar unit; an active array antenna connected to the transmit module; and a receive module connected to the active array antenna to produce UWB frequencies that are down-converted from the V band input from the active array antenna, and a receive input of the UWB radar unit connected to the receive module. 
     According to another embodiment, a method includes: up-converting a UWB frequency pulse from a UWB radar unit to a V band frequency pulse; transmitting the V band frequency pulse via an active array antenna; receiving a V band echo pulse via the active array antenna; down-converting the V band echo pulse from the active array antenna to a UWB pulse; and feeding the UWB pulse to the UWB radar unit for processing by the UWB radar unit. 
     According to another embodiment, a device includes: an antenna board that defines an antenna plane being the plane of the board and comprising a plurality of antenna elements; a mother board providing a corporate combining feed to the antenna board; and a power management board to which the antenna board and mother board are mounted perpendicularly to the antenna plane, wherein the antenna elements provide a beam forming antenna for ultra wide band pulses at V band frequencies. 
     The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system block diagram illustrating a portable handheld radar system in accordance with one embodiment; 
         FIG. 2  is a system block diagram illustrating a V-band transmitter and receiver used in a direct conversion setup in accordance with one embodiment; 
         FIG. 3  is a system block diagram illustrating a V-band transmitter and receiver with addition of components to make use of an existing 5 GHz UWB radar in accordance with an embodiment; 
         FIG. 4  is a block diagram with corresponding frequency spectrum graphs illustrating transmit operation of a radar system in accordance with an embodiment; 
         FIG. 5  is a block diagram with corresponding frequency spectrum graphs illustrating receive operation of a radar system in accordance with an embodiment; 
         FIG. 6  is a block diagram of a V band 16-by-1 active array antenna of a radar system in accordance with one embodiment; 
         FIG. 7  is a perspective diagram showing a physical arrangement of components for an active antenna array in accordance with one embodiment; 
         FIG. 8  is a diagram showing a mother board and an antenna board for an antenna array in accordance with one embodiment; and 
         FIG. 9  is block diagram for power management board for an active antenna array in accordance with one embodiment. 
     
    
    
     Embodiments and their advantages are best understood by referring to the detailed description that follows. Like reference numerals are used to identify like elements illustrated in one or more of the figures. 
     DETAILED DESCRIPTION 
     In accordance with one or more embodiments of the present invention, systems and methods disclosed herein provide compact, handheld radar detection of objects using RF pulses in the V band (approximately 50-75 GHz) produced from a radar unit operating in UWB band (approximately 1.6-10.5 GHz) and having a small, active array antenna whose size would ordinarily be too small for use at UWB band and which can take advantage of the higher frequencies of V band for improved beam forming and directionality of the radar pulses. In one particular embodiment, a V band radar system may use an existing commercially available UWB radar at 5 GHz connected to transmit and receive V band modules in a super-heterodyne configuration that converts the UWB radar to V band and uses a compactly sized active array antenna to provide enhanced antenna directionality and beam forming. 
     A portable radar system such as just described may be useful for dynamically scanning for objects (e.g., ordnance or vehicles) behind a wall, both from moving vehicles, on-road and off-road, and from the ground, and to statically locate internal structural details of buildings or other structures. —Such a radar system may be useful, for example, to persons (e.g., fire, rescue workers, military, police) needing information in situations involving their safety where other sources of information are unavailable or unreliable. 
       FIG. 1  illustrates a portable handheld radar system  100  in accordance with one or more embodiments. System  100  may emit RF radiation  101  toward a target object  102  in a direction controlled by a user or operator (not shown), for example, by aiming a hand-held unit containing the radar system  100 . Further aiming or scanning of RF radiation  101  may also be accomplished by a beam forming array antenna  104 . The transmitter of the system  100  may, for example, emit RF radiation  101  in the form of rapid wideband (narrow width) radar pulses at a chosen pulse repetition frequency (PRF) in the V band. The V band pulses can penetrate glass, wood, soil, concrete, dry wall and bricks with varying attenuation constant. By choosing a PRF in the range of 1-10 MHz, for example, and appropriate average transmitter power, a surveillance range of approximately 50-500 feet can generally be achieved. The radar system  100  may, for example, transmit Gaussian pulses as short as 100 pico-seconds wide with center frequency in the V band. Radar system  100  may employ a correlator pulse detector circuit to identify reflections  103  of the radiation  101 . Amplitude and delay information may be extracted and processed in an integrated signal processor, for example, included in signal processing and imaging module of UWB radar unit  110 . Radar unit  110 , which may be a pre-existing, commercially available unit, may provide a display for a user including images for which image construction algorithms may be implemented using digital signal processing (DSP). 
     Although two antennas  104  are shown in  FIG. 1  for clarity of illustration, use of a circulator  106  may enable use of a single antenna  104  for both transmit and receive. Antenna  104  may include a 16-by-1 active array antenna implemented using wafer scale antenna module technology. Wafer scale antenna modules (WSAM) are disclosed by U.S. Patent Application Publication 20090102703, filed Oct. 18, 2007, to Mohamadi et al., and U.S. Patent Publication 20080252546, filed Oct. 31, 2006, to Mohamadi, which are both hereby incorporated by reference. 
     Radar system  100  may include V band transmit module  120  and receive module  122 . Transmit module  120  and receive module  122  each have nominally 60 GHz center frequency, or local oscillator frequency for super-heterodyne frequency conversion, and therefore may also be referred to as “60 GHz” modules as well as “V band” modules. Each of 60 GHz transmit module  120  and 60 GHz receive module  122  may produce or be responsive to frequencies in the range of about 53 GHz to 65 GHz, and may provide a wide band platform for transmission of the UWB spectrum of short impulses at 60 GHz. Transmit module  120  and receive module  122  may be provided with a phase reference  123 , as shown in  FIG. 1 . System  100  may also include band pass filters  124 ,  126  to select out unneeded sidebands produced by the super-heterodyne frequency conversion. 
     One operational purpose of system  100  is to provide a link at 60 GHz for transmission and reception of base band (e.g., UWB band) short impulses (as short as 100 pico-seconds) to be used for high precision radar applications. Another purpose of system  100  is to serve as a direct conversion system that modulates a base band short impulse 200 pico-seconds long (producing a spectrum 5 GHz wide) used in a 60 GHz radar front end. System  100  may provide a 60 GHz platform that can be used with an existing 5 GHz UWB radar system that allows the existing 5 GHz UWB system to benefit from the practical size of a directive antenna at 60 GHz. Using the 60 GHz transmit module  120  and receive module  122  in tandem with the existing 5 GHz UWB radar system can provide a virtual narrow beam at 5 GHz which can improve the detection resolution without the need to use antenna arrays with impractical sizes at 5 GHz. 
       FIG. 2  is a system block diagram illustrating a V-band transmitter and receiver system  200  used in a direct conversion configuration using the same 60 GHz transmit module  120  and 60 GHz receive module  122 . System  200  may include an impulse generator  210  connected to transmit module  120 . The impulse from impulse generator  210  is up-converted by transmit module  120 , then transmitted and received through the 23 dB, 10 degrees beam width standard horn antennas  204 . The received reflections  103  may be down-converted and fed to sampling scope  211 . 
       FIG. 3  illustrates a V-band transmitter and receiver system  300  with addition of components to system  200  to make use of an existing 5 GHz UWB radar  110  in accordance with an embodiment. As is shown in the block diagram of  FIG. 3 , with the addition of some external components, e.g., circulator  106  and band pass filters  124 ,  126 , the existing 5 GHz UWB radar  110  can be used alongside the same V band modules  120 ,  122  of system  200  in a super-heterodyne configuration. To choose the lower side band spectrum, system  300  may use band pass filters (and a circulator  106  at transmit module  120 ). If desired, the upper side band spectrum could be used instead by choosing different values for the band pass filter components. 
       FIG. 4  and  FIG. 5  are diagrams showing frequency spectrum graphs to illustrate the transmit and receive, respectively, operation of radar systems  100 ,  200 , and  300 . As is shown in the block diagram of  FIG. 4 , and the frequency spectra shown in  FIG. 4  and  FIG. 5 , the 60 GHz front end (e.g., transmit module  120  and receive module  122 ) is transparent to the 5 GHz radar system  110 . In other words, the 5 GHz output  111  and 5 GHz input  112  of radar system  110  may be approximately the same regardless of whether the 60 GHz front end is connected to or being used with radar system  110 .  FIG. 4  shows the frequency spectrum at the output of each stage of transmit; for example, spectrum  125  shows that a lower side band centered at about 56 GHz has been selected for transmission by the antenna  104  or antenna  204 , while an upper side band centered at about 66 GHz has been suppressed. Similarly,  FIG. 5  shows the frequency spectrum at the input of each stage in the receive chain; for example, spectrum  127  shows the lower side band amplified while the upper side band is suppressed in this example embodiment, and conversion of the lower sideband via receive module  122  to the baseband spectrum  112 . 
     Another feature of the V band front end (e.g., transmit module  120 , receive module  122 , and band pass filters  124 ,  126 ) which improves the authenticity of the up-converted incident signal  101  and down-converted reflected signal  103  over the original 5 GHz signals from radar unit  110 , is the fact that the local oscillator (LO) frequencies at receive module  122  and transmit module  120  are phase locked through the phase reference  123  provided by the transmit module  120  board to the receive module  122 . 
       FIG. 6  is a block diagram illustrating a V band 16-by-1 active antenna array  600 , which may be used, for example, to implement active array antenna  104  of radar system  100 . The V band 16-by-1 active antenna array  600  is the front-end unit to address the directivity enabler for beam forming within the proposed heterodyne structure. Each element  610  of array  600  has its own dedicated amplifier  620 . Corporate combining may be used to implement a corporate distribution feed network  630 . The corporate distribution feed network  630  may be symmetrical leading to the in-phase addition of the propagated wave from each element  610 . Some nominal values that may be achieved using active antenna array  600  are: antenna array gain=14 dBi (decibels isotropic); antenna gain with reflector=18 dBi; dipole gain=2 dBi; P1 dB=+12 dBm; Gain=21 dB; corporate distribution 1 to 16 insertion loss on RO4035=2 dB; P in =4 dBm; P out =29 dBm EIRP (without reflector); P out =33 dBm EIRP (with reflector). 
       FIG. 7  is a perspective diagram showing a physical arrangement of components for an active antenna array system  700 . System  700  may include three separate boards and a reflector: a mother board  702 , an antenna board  704 , a power management board  706  and the reflector  708 . The mother board  702 , shown in  FIG. 7  and  FIG. 8 , hosts the MMIC (monolithic microwave integrated circuit) amplifiers  620  and the corporate distribution feed network  630 . Antenna board  704  hosts the antenna elements  610 . Power management board  706  hosts circuits to provide power management for the MMIC amplifiers. The antenna board  704  may be wire-bonded to the mother board  702  as shown also, for example, in  FIG. 8 . 
     Continuing with  FIG. 7  and  FIG. 8 , in order to maintain the ground plane integrity on the die and the board (e.g., MMIC dies on the mother board  702 , and antenna board  704 ) and also minimize the length of the wire bonds between antenna board  704  and mother board  702 , a laser cut trench  710  may be devised on the mother board  702 . The trench  710  may house  16  MMIC amplifiers  620  which are die attached to the substrate (e.g., mother board  702 ) and are fed through the corporate distribution feed network  630 . The corporate combining feeds (e.g., network  630 ) to antenna array  600  are also shown in more detail in  FIG. 8 . There may be a pedestal devised in mother board  702  on which the antenna board  704  may be installed so that the continuity of the ground plane between the two boards—mother board  702  and antenna board  704 —is maintained. The antenna board  704  may be installed on the pedestal using silver epoxy and then the lines connecting the two boards may be wire-bonded so that the antenna array on antenna board  704  is attached to the active distribution network (e.g., network  630 ) on motherboard  702 . As shown in  FIG. 8  the maximum dimension, or width, of the antenna array  600  may be less than 2 inches. Active antenna array system  700  may readily be implemented using WSAM methods incorporated by reference above. 
       FIG. 9  is block diagram for power management board  706  for an active antenna array system  700 . Power management board  706  may be powered, for example, by a 5 V (volt) power input  7060 . Power management board  706  may provide a sequenced DC bias to the MMIC amplifiers  620  as indicated in  FIG. 9  by sequencing module  7061 , providing, for example, a 5 V bias sequencing for MMIC amplifiers  620 ; and sequencing module  7062 , providing, for example, a −3 V bias sequencing for MMIC amplifiers  620 . As shown in  FIG. 7 , power management board  706  may be installed perpendicularly to both the motherboard  702  and the reflector  708 . 
     Embodiments described herein illustrate but do not limit the disclosure. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the present disclosure. Accordingly, the scope of the disclosure is best defined only by the following claims.