Abstract:
The invention concerns 2-oxo-1-pyrrolidine derivatives and a process for preparing them and their uses. The invention also concerns a process for preparing α-ethyl-2-oxo-1-pyrrolidine acetamide derivatives from unsaturated 2-oxo-1-pyrrolidine derivatives. Particularly the invention concerns novel intermediates and their use in methods for the preparation of S-α-ethyl-2oxo-1-pyrrolidine acetamide.

Description:
BACKGROUND OF THE INVENTION 
   Devices of wireless communication network may use dual antennas and/or antenna arrays to improve the network capacity and data rates. The devices may use antenna selection techniques and/or antenna diversity techniques to select one of the antennas to receive or transmit signals. Those techniques may consume valuable power and calculation time of the processors used in the wireless devices. Furthermore, according to those techniques, only one antenna at a time may be used. 
   Thus, there is a need for better ways to combine the signals received by the above described antennas to improve the capacity and data transmission rate of wireless communication networks. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings in which: 
       FIG. 1  is a schematic illustration of a portion of a wireless communication system according to an exemplary embodiment of the present invention; 
       FIG. 2  is a block diagram of a communication device according to an exemplary embodiment of the present invention; 
       FIG. 3  is a schematic illustration of an antenna receiver according to an exemplary embodiment of the present invention; 
       FIG. 4  is an illustration of graphs useful in demonstrating a weighting operation of an antenna weight value generator according to an exemplary embodiment of the invention; 
       FIG. 5  is an illustration of an implementation of a portion of an antenna receiver according to an exemplary embodiment of the present invention; and 
       FIG. 6  is an illustration of another implementation of a portion of an antenna receiver according to another exemplary embodiment of the present invention. 
   

   It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
   DETAILED DESCRIPTION OF THE INVENTION 
   In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention. 
   Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing term such as “plurality” may be used throughout the specification to describe two or more components, devices, elements, parameters and the like. For example, “plurality of antennas” describes two or more antennas. 
   It should be understood that the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuits and techniques disclosed herein may be used in many apparatuses such as units of a wireless communication system, such as, for example, a wireless local area network (WLAN) communication system, cellular communication systems, two way communication systems, and the like. Units of WLAN communication system intended to be included within the scope of the present invention include, by way of example only, wireless communication devices, mobile units (MU), mobile stations, access points (AP), public APs and the like. Units of cellular communication system intended to be included within the scope of the present invention includes MUs, base stations, and the like. 
   Types of WLAN communication systems intended to be within the scope of the present invention include, although are not limited to, “IEEE-Std 802.11, 1999 Edition (ISO/IEC 8802-11:1999)” standard, and more particularly in “IEEE-Std 802.11b-1999, IEEE-Std 802.11a, IEEE-Std 802.11g, IEEE-Std 802.11j, or the like. 
   Turning to  FIG. 1 , a portion of a wireless communication system  1000  according to embodiments of the present invention is shown. Although the scope of the present invention is not limited in this respect, the portion of wireless communication system  1000  may include a wireless communication device  100  which may include an antenna receiver  110  to provide a combined radio frequency (RF) signal. Antenna receiver  110  may receive RF signals via antennas  120 ,  130 , and  140 . The RF signals may be transmitted by a wireless communication device  170  via antennas  150  and  160 , although the number of antennas that may be connected to the antenna receiver  110  is in no way limited to three antennas. 
   Although the scope of the present invention is not limited in this respect, wireless communication system  1000  may be a WLAN or a wireless metropolitan-area networks (WMAN) that may use the spatial domain in order to improve WLAN and/or WMAN network capacity and data rates. Wireless communication device  170  may include, for example, an AP of WLAN that may transmit RF signals by using beam-forming techniques. Furthermore wireless communication device  170  may transmit RF signals through channels  125 ,  135 ,  145 . In some embodiments of the invention, channels  125 ,  135 ,  145  may be uncorrelated channels, which may be separated by at least one wavelength, if desired. The uncorrelated channel (e.g. channel  125 ) may be characterized by some characteristics such as, for example, frequency, modulation, noise, fading, load and the like. 
   Turning to  FIG. 2 , a block diagram of a communication device  200 , for example, a wireless communication device, according to an exemplary embodiment of the invention is shown. Although the scope of the present invention is not limited in this respect, communication device  200  may include a receiver (RX)  210 , a transmitter (TX)  220  and a controller  230  that may control an antenna switch  240 . Antennas  252 ,  254 ,  255  may be coupled to communication device  200 . Although the scope of the present invention is not limited in this respect, antennas  252 ,  254 ,  255  may be for example, dipole antennas, omni-directional antennas, highly-directional, steerable antennas, and the like. 
   Although the scope of the present invention is not limited in this respect, receiver  210  may include a baseband (BB) unit  260  and an antenna receiver  270 . In this exemplary embodiment of the invention, antenna receiver  270  may include a RF section  272  that may combine RF signals received via antennas  252 ,  254 ,  255 , a RF to intermediate frequency (IF) downconverter (DCON)  274  that may downconvert the combined RF signal provided by RF section  272  to an IF signal, and an IF to BB downconverter (DCON)  276  that may convert the IF signal to a BB signal, if desired. 
   It should be understood by one skilled in the art that in alternative embodiments of the present invention, the number of antennas that may be coupled to communication device  200  may vary from a single antenna to any number of antennas. The number of antennas may be limited only by the physical capacity of the communication device  200 . 
   Although the scope of the present invention is not limited in this respect, controller  230  may select the antennas by controlling antenna switch  240 . Furthermore, antenna switch  240  may toggle communication device  200  between transmit to receive modes, if desired. TX  220  may transmit RF signals via antennas  252 ,  254 ,  255 , and BB unit  260  may process the signals received by antennas  252 ,  254  and  255  according to a protocol of the desired communication system, for example, a cellular communication system, a WLAN communication system, and the like. 
   Turning to  FIG. 3 , a schematic illustration of an antenna receiver  300  according to exemplary embodiment of the present invention is shown. Although the scope of the present invention is not limited in this respect, antenna receiver  300  may be divided into three portions (shown with dotted lines), for example, a RF section  301 , a RF to IF downconverter  302  and an IF-to-BB down converter  303 . The RF section  301  may include bandpass filters  310  and antenna weighted value generators  320  that may each generate real and imaginary components  321 ,  322 , respectively, of an antenna weighted value. 
   Although the scope of the present invention is not limited in this respect, at least one of antenna weight value generators  320  may include a variable linear amplifier (LNA)  324 , for example, a variable linear law noise amplifier, a variable amplifier  326 , and a variable amplifier  328 . LNA  324  may adjust the amplitude of the RF signal received by the antenna, for example, antenna  120 . Variable amplifier  326  may adjust the phase of the RF signal received by the antenna, for example antenna  120 , and may provide real component  321  of the antenna weighted value. Variable amplifier  328  may adjust the phase of the RF signal received by the antenna, for example antenna  120 , and may provide imaginary component  322  of the antenna weighted value. Real components  321  of the antennas weighted values may be combined by an adder  330  to provide a real component  332  of a combined antenna weighted signal, and imaginary components  322  of the antennas weighted values may be combined by an adder  340  to provide an imaginary component  334  of a combined antenna weighted signal. 
   Although the scope of the present invention is not limited in this respect, antenna weighted value generator may provide the antenna weighted value based on a manipulation of a value derived from an amplitude of the RF signal received by the antenna with a value derived from a phase of the RF signal received by the antenna, for example, antenna  120 , as described in detail below. LNA  324  may adjust the amplitude of the received signal; and variable amplifier  326  and  328  may adjust the phase of the amplitude-adjusted received signal. 
   Although the scope of the present invention is not limited in this respect, LNA  324  may be a variable gain amplifier and variables amplifiers  326 ,  328  may be adjustable phase amplifiers, if desired. 
   Although the scope of the present invention is not limited in this respect, the RF-to-IF downconverter section  302  may include mixers  352 ,  354 ,  356 ,  358  that may mix the real component  332  of the combined antenna weighted signal (mixers  352 ,  354 ) and the imaginary component  334  of the combined antenna weighted signal (mixers  356 ,  358 ) with two local oscillator (LO) signals, cos(2πf RFLO t) and sin(2πf RFLO t). Mixers  352 ,  354  and mixers  356 ,  358  may downconvert the RF signals into real and imaginary IF signals, respectively. The downconverted real and imaginary signals may be combined by combiners  362  and  364 . Combiner  362  may provide a real IF signal and combiner  364  may provide an imaginary IF signal. 
   Although the scope of the present invention is not limited in this respect, the IF-to-BB downconverter section  303  may include mixers  372 ,  374 ,  376 ,  378  that may further mix the real IF signal (mixers  372 ,  374 ) and the imaginary IF signal (mixers  376 ,  378 ) with two local oscillator (LO) signals, cos(2πf IFLO t) and sin(2πf IFLO t). Mixers  372 ,  374  and mixers  376 ,  378  may downconverter the IF signals into real and imaginary BB signals, respectively. The downconverted real and imaginary signals may be combined by combiners  382  and  384 . Combiner  382  may provide a real BB signal and combiner  384  may provide an imaginary BB signal. In some embodiments of the invention, the real and imaginary BB signals may be filtered by lowpass filters  392  and  394 , respectively. 
   Although the scope of the present invention is not limited in this respect, embodiments of antenna weight value generator  320  may use a suitable mathematical algorithm to manipulate the amplitude and/or phase of the RF signals received by antennas  120 ,  130 ,  140 , to produce the antenna weight value, if desired. Antenna weight value generator  320  may be implemented by hardware, software, or by any suitable combination of hardware and/or software. 
   Although the scope of the present invention is not limited in this respect, a digitally modulated transmitted signal may generally be represented by:
 
 s ( t )= Re[{tilde over (s)} ( t ) exp( j 2 πf   c   t )]= s   1 ( t )cos(2 πf   c   t )− s   Q ( t )sin(2 πf   c   t )  (Equation 1)
 
   wherein, {tilde over (s)}(t) may be a complex-envelope of the signal s(t) and f c  is the transmitted carrier frequency. In some embodiments of the invention, a channel, for example channel  125 , may cause path-loss and/or signal fading, the latter being time-variant. Channels  125 ,  135 ,  145  may be uncorrelated or correlated channels. 
   Consequently, the signal received at a k th  antenna may represented by:
 
 g   k ( t )= Re[{tilde over (g)}   k ( t )exp( j 2 πf   c   t )] g=g   Ik ( t )cos(2 πf   c   t )− g   Qk ( t )sin(2 πf   c   t )  (Equation 2)
 
   wherein, the complex envelope {tilde over (g)} k (t) may be related to the complex-envelope of the signal transmitted through a certain channel weight. More specifically, the signal received at the k th  antenna may be represented by:
 
 {tilde over (g)}   k ( t )= C   k exp( jθ   k ) {tilde over (s)} ( t ).  (Equation 3)
 
   wherein, C k  and θ k  are channel amplitude and phase parameters respectively. 
   Although the scope of the present invention is not limited in this respect, antenna weighted value generator  320  may manipulation of a value derived from an amplitude of the received signal, for example, the complex-envelope {tilde over (g)} k (t) and a value derived from a phase of the received signal, for example, A k exp(jφ k ). Antenna weighted value generator  320  may weigh the complex-envelope {tilde over (g)} k (t) with a programmable antenna weight, for example, A k  exp(jφ k ), wherein A k  may represent a gain and φ k  may represent a phase-shift in an antenna path. Furthermore, in some embodiments of the invention, the antenna weighted value may be computed on a periodic basic based on channel estimation information (C k  and θ k ) which may be estimated from the received signal, if desired. 
   Although the scope of the present invention is not limited in this respect, the combination of the variable gain of LNA  324  and the gains A r  and A i  of amplifiers  326  and  328  may be used to realize the corresponding phase-shift. Thus, the complex IF signal at the output of the RF-to-IF downconverter may be described by: 
                           g   IF     ⁡     (   t   )       =       ⁢       1   2     ⁢     ∑         G     LNA   ,   k       ⁡     (       A   rk     +     j   ⁢           ⁢     A   lk         )       [             g   ~     k     ⁡     (   t   )       ⁢           ⁢     exp   ⁡     (     j   ⁢           ⁢   2   ⁢           ⁢     π   IF     ⁢   t     )         +                           ⁢           g   ~     k   *     ⁡     (   t   )       ⁢           ⁢   exp   ⁢     {     j   ⁢           ⁢   2   ⁢           ⁢     π   ⁡     (       2   ⁢     f   c       +     f   IF       )       ⁢   t     }       ]                 (     Equation   ⁢           ⁢   4     )               
wherein, G LNA,k  may be the magnitude of the antenna weight value, A rk  and A ik  may be the real and imaginary parts of the antenna weight value and f IF  may be the frequency of the intermediate frequency. The BB signal may be described by:
 
                     g   BB     ⁡     (   t   )       =       1   2     ⁢     ∑         G     LNA   ,   k       ⁡     (       A   rk     +     j   ⁢           ⁢     A   ik         )       ⁢         g   ~     k     ⁡     (   t   )                     (     Equation   ⁢           ⁢   5     )               
Equation 5 may be re-written as follows:
 
   
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           g 
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                         ⁡ 
                         
                           ( 
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                       = 
                       
                         
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                                   ⁢ 
                                   
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                       wherein 
                       , 
                     
                   
                 
                 
                   
                     
                       
                         
                           g 
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                         ⁡ 
                         
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                       = 
                       
                         
                           
                             G 
                             
                               LNA 
                               , 
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                                 A 
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                                 2 
                               
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                           ⁢ 
                           
                               
                           
                           ⁢ 
                           and 
                           ⁢ 
                           
                               
                           
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                             φ 
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                                 A 
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                 ( 
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   6 
                 
                 ) 
               
             
           
         
       
     
   
   Turning to  FIG. 4 , graphs useful in demonstrating a weighting operation of antenna weight value generator  320  according to an exemplary embodiment of the invention are shown. Although the scope of the present invention is not limited in this respect, the weighting operation may be graphically described in terms of vector addition. The outputs of the variable-gain amplifiers A r    326  and A i    328  may be mutually orthogonal by quadrature mixing in the RF-to-IF downconverter section. Various examples of phase-shifts in the first quadrant are shown, although the scope of the present invention is not limited in this respect, for example, because phase shifts over all four quadrants may be realized. A graph  400  depicts an example of vector summation of the gains of amplifiers  326  and  328 , for vector amplitudes A r =1, A i =0 and a phase φ=0. A graph  410  may depict, for example, vector summation of the gains of amplifiers  326  and  328 , for vector amplitudes A r =1, A i =½ and a phase φ=26.5. A graph  420  may depict, for example, vector summation of the gains of amplifiers  326  and  328 , for vector amplitudes A r =1, A i =1 and a phase φ=45. A graph  430  may depict, for example, vector summation of the gains of amplifiers  326  and  328  for vector amplitudes A r =½, A i =1 and a phase φ=63.5. A graph  440  may depict, for example, vector summation of the gains of amplifiers  326  and  328 , for vector amplitudes A r =0, A i =1 and a phase φ=90. 
   Turning to  FIG. 5 , an illustration of a practical implementation of a portion of an antenna receiver  500  according to an exemplary embodiment of the present invention is shown. Although the scope of the present invention is not limited in this respect, amplifiers A r1    510 , A r2    520  and A r3    530  may be implemented using multiple differential pair transistors, for example, complementary metal oxide semiconductor (CMOS) transistors or the like. The variable-gain functionality may be implemented using second differential pair transistors which may be driven by a gain-control signal, denoted VG, for example a voltage signal. The VG signal may cause a portion of the signal current to be diverted to the supply. The currents from the individual amplifiers may be summed and fed into a primary of a transformer  540 . A secondary of transformer  540  may be connected to multiplexers  550 ,  560 . For example, multiplexer  550  and/or multiplexer  560  may be implemented using a pair of quadrature devices, for example CMOS transistors, which may together realize quadrature downconversion. 
   Although the scope of the present invention is not limited in this respect, this portion of antenna receiver  500  may be used for combining the real components of the antenna signals and/or the imaginary components of the antenna signals, as described above. Embodiments of the present invention may use two similar portions of antenna receiver  500 . A first portion may be used to combine the real components of the antenna signals and the second portion may be used to combine the imaginary components of the antenna signals. 
   Turning to  FIG. 6 , an illustration of another practical implementation of a portion of an antenna receiver  600  according to an exemplary embodiment of the present invention is shown. Although, the scope of the present invention is not limited in this respect, amplifiers A r1    610 , A r2    620  and A r3    630  may be implemented with multiple differential pairs transistors, for example, CMOS transistors or the like. The variable-gain functionality may be implemented using a second differential pair transistors which may be driven by a gain-control signal VG. The VG voltage may cause a portion of the signal current to be diverted to the supply. The currents from the individual amplifiers may be summed and fed into a primary of a transformer  640 . In this embodiment of the invention, transformer  640  may be a 2:1:1 transformer, which may include two secondaries. A first secondary of transformer  640  may be connected to multiplexer  650 , and a second secondary may be connected to multiplexer  660 . Multiplexers  650 ,  660  may be implemented using a pair of quadrature devices, for example CMOS transistors, which may together realize quadrature downconversion. One notable difference between amplifiers  510 ,  520 ,  530  and amplifiers  610 ,  620  and  630  is the arrangement of the multiple differential pair transistors. Because of their different arrangements, amplifiers  510 ,  520 ,  530  may be suitable for some embodiments of the invention and amplifiers  610 ,  620  and  630  may be suitable for other embodiments of the present invention, if desired. 
   While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.