Abstract:
A signal transmission and reception device is disclosed that can be made compact and has wide-band band-pass characteristics. The signal transmission and reception device includes a first filtering unit that is composed of a distributed constant circuit and is capable of eliminating a first frequency component or a second frequency component. The second frequency is higher than the first frequency, and a second filtering unit that attenuates components of frequencies lower than the first frequency or components of frequencies higher than the second frequency.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to a signal transmission and reception device which performs communications by using impulse UWB (Ultra Wide Band) signals. 
         [0003]    2. Description of the Related Art 
         [0004]    In spread spectrum communications, in order to obtain a large variety of correlation characteristics, it is proposed to convert Pseudorandom Noise (PN) codes used in DSSS (Direct Sequence Spread Spectrum) to Return-to-Zero (RZ) codes, and multiply the RZ codes by data. For example, Japanese Laid-Open Patent Application No. 4-347943 (referred to as “reference 1” hereinafter) discloses a technique in this field. Since each PN code can have a positive or a negative value, by converting the PN codes to the RZ codes, output data becomes zero in a certain time period of the PN code, thus, each RZ code can have three types of values, that is, a positive, zero, or a negative value. 
         [0005]    On the other hand, a UWB-IR (UWB-Impulse Radio) communication system is attracting attention since the UWB-IR system is capable of large capacity data transmission and is able to accommodate a large number of users. Since impulses shorter than 1 ns are used in the UWB-IR system, and the corresponding frequency band is at a few GHz, conventional radio communications are not interfered with; thus the frequency band can be shared. 
         [0006]    For example, it is proposed that a signal transmission device supporting the UWB-IR communications performs spread modulation and RZ conversion of the PN codes on data carried by the carrier, and converts the resulting data to impulse radio signals. Further, a signal reception device for receiving the impulse radio signals has been developed. For example, Japanese Laid-Open Patent Application No. 2006-114980 (referred to as “reference 2” hereinafter) discloses a technique in this field. 
         [0007]    In addition to the capability of large capacity data transmission, when the UWB-IR communication system is used in data transmission, it is possible for the transmitter to measure positions with high precision. Further, when a receiver supporting the UWB-IR communications is used together with the transmitter, it is possible to measure distances with high precision. 
       SUMMARY OF THE INVENTION 
       [0008]    It is a general object of the present invention to make some novel improvements. 
         [0009]    One specific object of the present invention is to provide a compact signal transmission and reception device having a one-chip impulse receiver and a one-chip impulse transmitter, having low power consumption and capable of position and distance measurements, and data communications. 
         [0010]    According to a first aspect of the present invention, there is provided a signal transmission and reception device, comprising: 
         [0011]    a transmission unit that converts transmission data spread by spread codes to a RZ signal, multiplies a code of an impulse series by the RZ signal to convert the RZ signal to an impulse radio signal, and transmits the impulse radio signal, said transmission unit being integrated into one chip; and 
         [0012]    a reception unit that receives and demodulates the impulse radio signal, said reception unit being integrated into one chip. 
         [0013]    As an embodiment, a special position of the signal transmission and reception device may be determined when the signal transmission and reception device receives the impulse radio signal transmitted by the signal transmission and reception device itself. 
         [0014]    As an embodiment, the signal transmission and reception device further comprises: 
         [0015]    a distance measurement unit that measures a distance between the signal transmission and reception device and an object based on a time difference between an impulse radio signal transmitted by the transmission unit toward the object and an impulse radio signal reflected by the object and received by the reception unit. 
         [0016]    As an embodiment, the signal transmission and reception device further comprises: 
         [0017]    a filtering unit that passes through the impulse radio signal transmitted by the transmission unit and the impulse radio signal received by the reception unit, 
         [0018]    wherein 
         [0019]    the filtering unit includes
       a first pass band for passing through an impulse radio signal for use of Ultra Wide Band communications,   a second pass band different from the first pass band and for passing through an impulse radio signal for measuring the distance to the object, and       
 
         [0022]    the filtering unit is able to switch the first pass band and the second pass band. 
         [0023]    As an embodiment, the signal transmission and reception device further comprises: 
         [0024]    an adjustment terminal that connects an adjustment device for adjusting electric power of the impulse radio signal transmitted by the transmission unit. 
         [0025]    As an embodiment, the signal transmission and reception device further comprises: 
         [0026]    a detection terminal that connects a detection device for detecting a level of the impulse radio signal received by the reception unit. 
         [0027]    As an embodiment, in the signal transmission and reception device, a common clock signal is supplied to the transmission unit and the reception unit. 
         [0028]    As an embodiment, in the signal transmission and reception device each of the transmission unit and the reception unit is formed of a CMOS or a silicon-germanium semiconductor. 
         [0029]    As an embodiment, the signal transmission and reception device further comprises: 
         [0030]    a switching unit that connects one of the transmission unit and the reception unit to a transmission and reception antenna; and 
         [0031]    a controller that controls the switching unit. 
         [0032]    As an embodiment, the signal transmission and reception device further comprises: 
         [0033]    a sensor terminal that connects an external sensor; and 
         [0034]    a converter that converts detection signals from the external sensor into digital signals. 
         [0035]    According to the present invention, it is possible to provide a compact signal transmission and reception device having a one-chip impulse reception unit and a one-chip impulse transmission unit, having low power consumption and capable of position and distance measurements, and data communications. 
         [0036]    These and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments given with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a block diagram illustrating a configuration of a signal transmission and reception device according to an embodiment of the present invention; 
           [0038]      FIG. 2  is a flowchart illustrating switching a signal transmission procedure and a signal reception procedure in the signal transmission and reception device  1  of the present embodiment; and 
           [0039]      FIG. 3  is a flowchart illustrating a procedure of distance measurement performed by the signal transmission and reception device  1  of the present embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    Below, preferred embodiments of the present invention are explained with reference to the accompanying drawings. 
         [0041]      FIG. 1  is a block diagram illustrating a configuration of a signal transmission and reception device according to an embodiment of the present invention. 
         [0042]    As illustrated in  FIG. 1 , a signal transmission and reception device  1  includes a transmitter  10 , a receiver  20 , a controller  30 , a switch  40 , an antenna  50 , and a power supplier  60 . Each of the transmitter  10 , the receiver  20 , the controller  30 , the switch  40 , and the power supplier  60  is integrated into one chip by using CMOS (Complementary Metal Oxide Semiconductor). 
         [0043]    The transmitter  10  includes a transmission base band processing unit  11 , an impulse converter  12 , an amplifier  13 , and a transmission filter  14 . 
         [0044]    The receiver  20  includes a reception filter  21 , a low-noise amplifier (LNA)  22 , a detector (DET)  23 , and a reception base band processing unit  24 . 
         [0045]    Each of the transmission filter  14  and the reception filter  21  includes a first pass band for passing through impulse radio signals used for Ultra Wide Band communication, and a second pass band for passing through impulse radio signals for distance measurement (as described below), and each of the transmission filter  14  and the reception filter  21  is able to switch the first pass band and the second pass band. For example, the first pass band is set at 4.5 GHz for Ultra Wide Band communications, and the second pass band is set at 1 GHz. 
         [0046]    A common clock signal is supplied to the transmission base band processing unit  11  and the reception base band processing unit  24 . For example, as shown in  FIG. 1 , a clock signal input to the transmission base band processing unit  11  via a clock terminal  15  is also input to the reception base band processing unit  24 . 
         [0047]    The amplifier  13  is connected to an adjustment terminal  16 , which connects the amplifier  13  to an adjustment device for adjusting, from the outside, the electric power of the impulse radio signals to be transmitted. 
         [0048]    The detector (DET)  23  is connected to a detection terminal  25 , which outputs a signal indicating strength of received impulse radio signals. This signal is referred to as a “RSSI (Received Signal Strength Indicator) signal” below, where necessary. 
         [0049]    For example, the controller  30  includes a CPU (Central Processing Unit). The controller  30  is connected to an interface (I/F)  31 , a pulse input terminal  32 , an analog signal input terminal  33  (AIN), an Analog-Digital-Converter (A/D)  34 , and a flash memory terminal  35 . 
         [0050]    For example, the interface (I/F)  31  is a serial peripheral interface (SPI). For example, when a USB (Universal serial Bus) memory is connected to the interface  31 , various kinds of data to be transmitted can be input to the signal transmission and reception device  1 . 
         [0051]    For example, the pulse input terminal  32  is for inputting pulse signals used for distance measurement (as described below). 
         [0052]    The analog signal input terminal  33  (AIN) is connected to an acceleration meter (not illustrated). An analog signal input from the acceleration meter through the analog signal input terminal  33  is converted into a digital signal, and is input to the transmitter  10  via the controller  30 . 
         [0053]    The flash memory terminal  35 , for example, similar to the interface (I/F)  31 , also supports the serial peripheral interface (SPI). While the interface  31  is used for inputting transmission data, the flash memory terminal  35  is primarily used for inputting identification signals to the controller  30 . For example, the identification signals include identifiers for individual identification. 
         [0054]    The controller  30  performs calculations for measuring the distance to an object based on a time difference between a transmitted wave and a received wave (namely, the delay time of the received wave relative to the transmitted wave). 
         [0055]    The switch  40 , which is used for switching transmitted and received signals, is connected to an output terminal  10 A of the transmitter  10 , and an input terminal  20 A of the receiver  20 . Additionally, the switch  40  is connected to the antenna  50 , which is used for transmitting or receiving signals. 
         [0056]    A power terminal  61  is provided on the signal transmission and reception device  1  for supplying power from the outside to the power supplier  60 . 
         [0057]    Below, operations of the signal transmission and reception device  1  are described. 
         [0058]    First, explanations are made when the signal transmission and reception device  1  is used in a position measurement system for measuring the special position of the signal transmission and reception device  1 . 
         [0059]    For example, the position measurement system includes a calculation device, which performs position measurement processing for measuring the special position of the signal transmission and reception device  1 , and plural signal transmission and reception devices connected to the calculation device. Below, the plural signal transmission and reception devices are referred to as “nodes”. These nodes are arranged at positions allowing UWB communications with the signal transmission and reception device  1 . The signal transmission and reception device  1  is used as a tag, and is arranged in a space which is to be measured. Each of these nodes can be the same as the signal transmission and reception device  1 , and this allows radio communications between the nodes. 
         [0060]    In the position measurement system, when impulse radio signals transmitted from the signal transmission and reception device  1 , which is used as a tag, are received by one of the nodes, the calculation device performs position measurement processing based on the position of the node which receives the impulse radio signals and the time of receiving the impulse radio signals by the node, and by this position measurement processing, the special position of the signal transmission and reception device  1  can be determined with high precision. 
         [0061]    Specifically, when the controller  30  directs to turn the transmitter  10  ON, the transmission base band processing unit  11  encodes and compresses digital data used for position measurement by known appropriate methods, and outputs the encoded and compressed data to the impulse converter  12 . The impulse converter  12  modulates the compressed data from the transmission base band processing unit  11 , for example, by phase modulation or others, and then, the modulated data are further modulated by spread modulation by using the PN (Pseudorandom Noise) codes. Further, the impulse converter  12  converts the data modulated by spread modulation to RZ signals, and the RZ signals are converted into impulse radio signals. At this stage, since the transmitter  10  and the antenna  50  are connected through the switch  40  controlled by the controller  30 , the output signals from the impulse converter  12  are amplified by the amplifier  13  to a certain level, and are transmitted from the antenna  50  through the transmission filter  14 . 
         [0062]    When the impulse radio signals transmitted from the antenna  50  of the signal transmission and reception device  1  are received by one of the nodes of the position measurement system, and the above position measurement processing is executed, the special position of the signal transmission and reception device  1  can be determined with high precision. 
         [0063]    When the controller  30  directs to turn the receiver  20  ON, the switch  40  is switched to the receiver  20  side, and the signal transmission and reception device  1  is ready for receiving data from the node. 
         [0064]    When the receiver  20  receives the impulse radio signals from the node, the signal transmission and reception device  1  determines whether the received impulse radio signals are those sent to itself. 
         [0065]      FIG. 2  is a flowchart illustrating switching of a signal transmission procedure and a signal reception procedure in the signal transmission and reception device  1  of the present embodiment. 
         [0066]    Note that the procedure shown in  FIG. 2  can be executed by the transmitter  10 , the receiver  20 , and the controller  30 . 
         [0067]    As shown in  FIG. 2 , in step S 20 , the controller  30  switches the switch  40  in each specified time period to determine whether the impulse radio signals are received. 
         [0068]    In this way, impulse radio signals involved in the determination by the controller  30  are signals transmitted from a node of the position measurement system. When the receiver  20  receives the impulse radio signals, the receiver  20  demodulates the received impulse radio signals, and transmits the demodulated data to the controller  30 . 
         [0069]    When it is determined that the impulse radio signals are not received, the procedure proceeds to step S 21 . 
         [0070]    In step S 21 , the switch  40  is switched to the transmitter  10  side. 
         [0071]    In step S 22 , the transmitter  10  encodes and compresses the transmission data by appropriate coding methods. In this step, the base band is modulated by the transmission base band processing unit  11 . 
         [0072]    In step S 23 , the transmitter  10  performs spread modulation and RZ conversion by using the PN (Pseudorandom Noise) codes, and the RZ signals are converted into impulse radio signals. In this way, the impulse radio signals are produced. 
         [0073]    In step S 24 , the impulse radio signals are transmitted from the antenna  50 . 
         [0074]    In step S 25 , when it is determined by the controller  30  in step S 20  that the impulse radio signals are received, base band demodulation is performed on the received impulse radio signals. 
         [0075]    In step S 26 , the controller  30  confirms the identifier included in the demodulated signals. 
         [0076]    In step S 27 , when the controller  30  determines that the identifier included in the demodulated signals is the same as the identifier of the signal transmission and reception device  1 , the controller  30  reads in the received data, and performs processing according to the received data. 
         [0077]    Concerning the impulse radio signals transmitted from the position measurement system and received by the receiver  20 , for example, when plural signal transmission and reception devices  1  are present in a certain space, the impulse radio signals may be signals including data for ranking the signal transmission and reception devices  1 . Due to this, since plural signal transmission and reception devices  1  can be ranked in the position measurement system to perform data communications sequentially, data for performing calling out and standby can be transmitted to the signal transmission and reception devices  1 . 
         [0078]    Signals indicating data requested by the signal transmission and reception device  1  can be transmitted from the position measurement system to the signal transmission and reception device  1 . Due to this, when the signal transmission and reception device  1  is used in the position measurement system, it is possible to construct a network system. 
         [0079]    If an acceleration meter is connected to the analog signal input terminal  33  of the signal transmission and reception device  1 , and acceleration data detected by the acceleration meter are sent to the position measurement system, the position measurement system is able to determine the position of the signal transmission and reception device  1 . Furthermore, the position measurement system can receive acceleration data detected by the acceleration meter connected to the signal transmission and reception device  1 . 
         [0080]      FIG. 3  is a flowchart illustrating a procedure of distance measurement performed by the signal transmission and reception device  1  of the present embodiment. 
         [0081]    As described above, the signal transmission and reception device  1  is able to transmit or receive the impulse radio signals. If the signal transmission and reception device  1  is configured to receive impulse radio signals transmitted by itself toward a specified target, the distance from the signal transmission and reception device  1  to the target can be measured. For example, the controller  30  performs calculations and processing required for the distance measurement. 
         [0082]    As shown in  FIG. 3 , in step S 30 , the controller  30  switches the switch  40  to the transmitter side. 
         [0083]    In step S 31 , the transmitter  10  generates impulse radio signals based on pulse signals from the controller  30 . For example, the pulse signals are input from a pulse generator (not illustrated) connected to the pulse input terminal  32  and are used for distance measurement. At the stage, the pass band of the transmission filter  14  may be switched to the second pass band to transmit impulse radio signals at 1 GHz. 
         [0084]    In step S 32 , the controller  30  switches the switch  40  to the side of the receiver  20 . 
         [0085]    In step S 33 , the receiver  20  demodulates the received impulse radio signals. 
         [0086]    In step S 34 , it is determined whether the transmitted impulse radio signals and the received impulse radio signals are sufficiently strongly correlated to each other. For example, this determination can be executed by sliding correlation. 
         [0087]    In step S 35 , when it is determined that sufficiently strong correlation exists, the controller  30  calculates the time delay between the transmitted impulse radio signals and the received impulse radio signals. 
         [0088]    In step S 36 , the controller  30  calculates the distance to the target based on obtained time delay. 
         [0089]    When it is determined that sufficiently strong correlation does not exist, the controller  30  returns to step S 30 . 
         [0090]    In this way, the distance to the target can be obtained by the signal transmission and reception device  1  of the present embodiment. 
         [0091]    If the signal transmission and reception device  1  is used outside, it can be used in a radar device to realize various applications. That is, the place for using the signal transmission and reception device  1  is not limited to the above mentioned desired space where the position measurement system is installed. 
         [0092]    According to the present embodiment, it is possible to provide a compact signal transmission and reception device formed from a one-chip impulse receiver  20  and a one-chip impulse transmitter  10 , having low power consumption and capable of position and distance measurements, and data communications. 
         [0093]    While the invention is described above with reference to specific embodiments chosen for purpose of illustration, it should be apparent that the invention is not limited to these embodiments, but numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention. 
         [0094]    For example, it is described above that each of the transmitter  10 , the receiver  20 , the controller  30 , the switch  40 , and the power supplier  60  is integrated into one chip by using CMOS (Complementary Metal Oxide Semiconductor), but the present invention is not limited to this. Instead of CMOS, the transmitter  10 , the receiver  20 , the controller  30 , the switch  40 , and the power supplier  60  can be integrated into one chip by using silicon-germanium semiconductor. 
         [0095]    It is described above that the transmitter  10  and the receiver  20  have built-in transmission filter  14  and reception filter  21 , respectively, but the present invention is not limited to this. The transmission filter  14  and reception filter  21  can be provided outside the signal transmission and reception device  1 . 
         [0096]    It is described above that the switch  40  switches the connection between the transmitter  10  and the receiver  20  with the antenna  50 , but the present invention is not limited to this. For example, the transmitter  10  and the receiver  20  may have their own antennae, respectively. In this case, the switch  40  can be omitted. 
         [0097]    It is described above that the first pass band of the transmission filter  14  and reception filter  21  is set at 4.5 GHz, but the present invention is not limited to this. The first pass band can be set to be any value in a range from 3.1 to 10.6 GHz as long as the first pass band is a band allowing Ultra Wide Band communications. 
         [0098]    In addition, when the signal transmission and reception device  1  does not measure the distance but only performs Ultra Wide Band communications, the transmission filter  14  and reception filter  21  may be omitted. 
         [0099]    It is described above that the switch  40  is installed in the signal transmission and reception device  1 , but the present invention is not limited to this. The switch  40  may be provided outside the signal transmission and reception device  1 . 
         [0100]    It is described above that an acceleration meter is connected to the analog signal input terminal  33 , but the present invention is not limited to this. Various sensors can be connected to the analog signal input terminal  33 , for example, when a sensor for detecting vital signs like blood pressure and pulsation, the vital data of the owner of the signal transmission and reception device  1  can be transmitted. 
         [0101]    This patent application is based on Japanese Priority Patent Application No. 2007-051827 filed on Mar. 1, 2007, the entire contents of which are hereby incorporated by reference.