Abstract:
The circuits of a multimode wireless transmitter are complex and large, and thus difficult to incorporate in a portable wireless device. This problem is solved for a multimode wireless transmitter by enabling the first frequency mode circuit and the second frequency mode circuit to use the same frequency dividers.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a high frequency integrated circuit used in a portable wireless communication device, and relates more particularly to a multimode wireless transmitter affording low power consumption in a smaller and lighter device, and to a portable wireless device using said multimode wireless transmitter. 
   2. Description of Related Art 
   Mobile communication devices increasingly feature functions affording compatibility with different communication systems, and multiband systems that operate across multiple frequency bands are becoming more common. Wireless devices compatible with such systems are extremely complex, necessitate large scale circuits, and have multiple oscillators that can result in spurious errors. See, for example, Japanese Unexamined Patent Application 2000-13274. 
   Conventional dual-mode portable communication terminals that operate on two frequency bands have two completely separate transmission channels with the RF sections tuned to separate frequencies and sharing few parts. Reducing the size, weight, and power consumption is therefore extremely difficult. 
   The present invention is directed to solving the foregoing problems of the prior art, and an object of the invention is to provide a multimode wireless transmitter affording a reduction in size, weight, and power consumption by using a common orthogonal modulator and amplifier in the transmission channels of a dual-mode portable communication terminal that operates on two frequency bands, providing a switch at the amplifier output to selectively supply signals to the transmission circuits in the different modes, and controlling changing the operating mode of the oscillator and two frequency dividers by means of a switch. A further object of the invention is to provide a portable wireless device using this multimode wireless transmitter. 
   SUMMARY OF THE INVENTION 
   A multimode wireless transmitter according to a first aspect of the present invention has a first oscillator that oscillates at a first predetermined frequency; a first frequency divider that frequency divides the frequency of the signal generated by the first oscillator by 2, and outputs a first carrier foIa and a second carrier foQa with a 90 degree phase difference therebetween; a second oscillator that oscillates at a second predetermined frequency that is different from the first predetermined frequency generated by the first oscillator; a second frequency divider that frequency divides the frequency of the signal generated by the second oscillator by 2; a third frequency divider that further divides the frequency of the output signal of the second frequency divider by 2, and outputs a third carrier foIb and a fourth carrier foQb with a 90 degree phase difference therebetween; a first switching amplifier that receives the first carrier foIa and third carrier foIb, selects the first or third carrier based on a control signal applied thereto, and amplifies and outputs the selected carrier; a second switching amplifier that receives the second carrier foQa and fourth carrier foQb, selects the second or fourth carrier based on a control signal applied thereto, and amplifies and outputs the selected carrier; and an orthogonal modulator for orthogonally modulating the baseband signal by means of the output signals from the first and second switching amplifiers. 
   Preferably, this multimode wireless transmitter also has a fourth frequency divider for frequency dividing the output signal frequency of the first frequency divider by 2; a third switching amplifier that receives the output signal from the third frequency divider and the output signal from the fourth frequency divider, selects either output signal based on a control signal applied thereto, and amplifies and outputs the selected output signal; a frequency synthesizer for comparing the selected output signal with a predetermined reference signal, and outputting a signal denoting the phase shift; and a loop filter for receiving the output signal of the frequency synthesizer. The oscillation frequency of the first oscillator or second oscillator is stabilized using output from the loop filter. 
   Yet further preferably, the first frequency divider and second frequency divider are combined in a single frequency divider. 
   Yet further preferably, the third frequency divider and fourth frequency divider are combined in a single frequency divider. 
   Yet further preferably, the first oscillator and second oscillator are combined in a single oscillator. 
   A multimode wireless transmitter according to a second aspect of the invention has a first oscillator that oscillates at a first predetermined frequency; a first frequency divider that frequency divides the frequency of the signal generated by the first oscillator by 2, and outputs a first carrier foIa and a second carrier foQa with a 90 degree phase difference therebetween; a second oscillator that oscillates at a second predetermined frequency that is different from the frequency generated by the first oscillator; a second frequency divider that frequency divides the frequency of the signal generated by the second oscillator by 2; a third frequency divider that further divides the frequency of the output signal of the second frequency divider by 2, and outputs a third carrier foIb and a fourth carrier foQb with a 90 degree phase difference therebetween; a first switching amplifier that receives the first carrier foIa and third carrier foIb, selects the first or third carrier based on a control signal applied thereto, and amplifies and outputs the selected carrier; a second switching amplifier that receives the second carrier foQa and fourth carrier foQb, selects the second or fourth carrier based on a control signal applied thereto, and amplifies and outputs the selected carrier; an orthogonal modulator for orthogonally modulating the baseband signal by means of the output signals from the first and second switching amplifiers; a first processing circuit; a second processing circuit; a switch for selecting the first antenna duplexing means or second antenna duplexing means; and an antenna connected to said switch. The first processing circuit has a first amplification means for amplifying output from the orthogonal modulator, and a first antenna duplexing means connected to the first amplification means, said first amplification means and first antenna duplexing means becoming operable when the first carrier foIa and second carrier foQa are selected. The second processing circuit has a second amplification means for amplifying output from the orthogonal modulator, and a second antenna duplexing means connected to the second amplification means, said second amplification means and second antenna duplexing means becoming operable when the third carrier foIb and fourth carrier foQb are selected. 
   EFFECT OF THE INVENTION 
   The number of oscillators can be reduced, the orthogonal modulator and amplifier can be shared, and the number of input terminals for baseband signals from the baseband signal processor can be reduced in a dual-mode wireless transmitter thus comprised because the intermediate frequency band is not used. The size of a portable wireless device using this multimode wireless transmitter can thus be reduced. 
   The present invention can also reduce the number of oscillators by not using the intermediate frequency band, reduce device size because the modulator can be shared, reduce the number of baseband signal input terminals from the baseband signal processor by sharing the orthogonal modulator, and facilitate adjusting for carrier leaks. 
   Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic block diagram of a multimode wireless transmitter according to a first embodiment of the present invention; 
       FIG. 2  is a block diagram showing the internal arrangement of the switching amplifiers in this first embodiment of the invention; 
       FIG. 3  is a circuit diagram of the switching amplifiers in this first embodiment of the invention; 
       FIG. 4  is a schematic block diagram of a multimode wireless transmitter according to a second embodiment of the present invention; and 
       FIG. 5  is a schematic block diagram of a multimode wireless transmitter according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention are described below with reference to the accompanying figures. 
     FIG. 1  is a schematic block diagram showing the arrangement of a multimode wireless transmitter according to a first embodiment of the present invention. Shown in  FIG. 1  are first and second oscillators  100 ,  101 ; first, second, third, and fourth frequency dividers  102 ,  103 ,  104 ,  105 ; first, second, and third switching amplifiers  106 ,  107 ,  108  having a switch function for selectively outputting one of two inputs; orthogonal modulator  109 ; first, second, third, fourth, fifth, and sixth amplifiers  110 ,  111 ,  112 ,  113 ,  114 ,  115 ; first and second bandpass filters  116 ,  117 ; frequency synthesizer  118  (variable frequency divider); loop filter  119 ; first and second duplexers  120 ,  121 ; mode switch  122 ; and external antenna  123 . 
   The operation of a multimode wireless transmitter thus comprised is described below. 
   When operating in a first frequency (2 GHz) mode, the first oscillator  100  generates a signal of frequency F 1 . In this embodiment of the invention frequency F 1  is 4 GHz by way of example. The first frequency divider  102  divides this signal by N1 (1/N1 frequency division), and outputs two carriers foIa and foQa with a 90 degree phase difference. In this embodiment the first frequency divider  102  divides by 2 (N1=2) and thus outputs two 2-GHz carriers. The first switching amplifier  106  amplifies carrier fola, and the second switching amplifier  107  amplifies the other carrier foQa at a 90 degree phase difference. The output signals from the switching amplifiers  106 ,  107  and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109  to acquire a modulated signal. A first carrier foIa and a second carrier foQa are thus selected and processed when operating in this first frequency mode. 
   Output from the orthogonal modulator  109  is then amplified by the first and second amplifiers  110 ,  111 , frequencies outside the required frequency band are removed by the first bandpass filter  116 , and the third amplifier  112  amplifies the transmission signal, which is then passed through the first duplexer  120  and mode switch  122  and transmitted from the external antenna  123 . 
   The first and second amplifiers  110 ,  111 , first bandpass filter  116 , and third amplifier  112  thus constitute a first processing circuit that operates when in the first frequency mode. 
   The fourth frequency divider  105  divides the output from the first frequency divider  102  by Na (1/Na frequency division) where Na is 2 in this embodiment, and thus outputs a 1-GHz signal. After the 1-GHz signal from the fourth frequency divider  105  is amplified by the third switching amplifier  108 , the frequency synthesizer (variable frequency divider)  118  divides the amplified signal to a comparison frequency, compares the result with an externally supplied reference frequency, and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the first oscillator  100 . This loop stabilizes the frequency of the carrier wave output from the first oscillator  100 . 
   When operating in the second frequency mode (800 MHz), the second oscillator  101  produces a frequency F 2  signal where frequency F 2  is 3.2 GHz, for example. The second frequency divider  103  divides this signal by N2 (1/N2 frequency division where N2=2 in this embodiment), and the third frequency divider  104  further divides the first frequency-divided output by N3 (1/N3 frequency division where N3=2 in this embodiment), thus outputting two 800-MHz carriers foIb and foQb at a 90 degree phase difference. The first switching amplifier  106  then amplifies carrier foIb, and second switching amplifier  107  amplifies the other 90-degree phase shifted carrier foQb. The output signals from the switching amplifiers  106 ,  107  and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109  to acquire a modulated signal. A third carrier foIb and a fourth carrier foQb are thus selected and processed when operating in this second frequency mode. 
   Note that these two frequency dividers  103  and  104  could be combined in a single (1/N2*N3) frequency divider, or more specifically a 1/4 frequency divider in this example. 
   This output from the orthogonal modulator  109  is then amplified by fourth and fifth amplifiers  113 ,  114 , frequencies outside the required frequency band are removed by the second bandpass filter  117 , and the sixth amplifier  115  amplifies the transmission signal, which is then passed through the second duplexer  121  and mode switch  122  and transmitted from the external antenna  123 . 
   The fourth and fifth amplifiers  113 ,  114 , second bandpass filter  117 , and sixth amplifier  115  thus constitute a first processing circuit that operates when in the first frequency mode. 
   After the 800-MHz signal output from the third frequency divider  104  is amplified by the third switching amplifier  108 , the frequency synthesizer (variable frequency divider)  118  divides the amplified signal to a comparison frequency, compares the result with an externally supplied reference frequency, and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the second oscillator  101 . This loop stabilizes the frequency of the carrier wave output from the second oscillator  101 . 
   Switching between the first frequency mode and the second frequency mode is effected by a signal applied to the control terminal  124  as shown in  FIG. 2  and described below. 
   In general, the operating current increases as the frequency being divided increases in a frequency divider that processes high frequency signals, and the frequency divider must be capable of handling a high current flow. This is dependent upon the frequency characteristics of the transistors forming the frequency divider, and a high current flow is necessary to prevent a drop in the output amplitude relative to the input amplitude. The fourth frequency divider  105  thus requires less operating current because the fourth frequency divider  105  operates at a lower frequency than the first frequency divider  102 . The third frequency divider  104  likewise frequency divides a lower frequency than the second frequency divider  103 , and thus also requires less operating current. 
     FIG. 2  is a block diagram showing the internal configuration of the first and second switching amplifiers  106 ,  107  shown in  FIG. 1  in this first embodiment of the invention, and  FIG. 3  is a circuit diagram of the same. Shown in  FIG. 2  and  FIG. 3  are the control terminal  124 , first and second frequency input terminal pairs  125  and  126 , frequency output terminal pair  127 , amplifier  128 , and selector switch pair  129 . 
   The first switching amplifier  106  and second switching amplifier  107  for outputting signals are configured as shown in  FIG. 2  and thus apply a control signal for selecting the 2-GHz mode (first frequency) or the 800-MHz mode (second frequency) from the first frequency input terminal pair  125  or second frequency input terminal pair  126 , respectively, to the control terminal  124 , thereby controlling the position of the selector switch pair  129  so that a signal of the first frequency or second frequency is amplified by the amplifier  128  and output from the frequency output terminal pair  127 . 
   As shown in  FIG. 3 , signals are input from the first frequency input terminal pair  125  in the 2-GHz mode, a 2-GHz mode selection signal is applied to the control terminal  124 , signals are amplified by the amplifier  128 , and signals are then output from the frequency output terminal pair  127 . 
   The number of oscillators is thus reduced by not using the intermediate frequency band, the modulator can be used in both the 2-GHz mode and 800-MHz mode, and size can therefore be reduced. 
   Note that the 2-GHz mode and 800-MHz mode are used in this first embodiment of the invention by way of example only, and the invention can be used to the same effect when operating at other frequencies. 
     FIG. 4  is a schematic block diagram of a multimode wireless transmitter according to a second embodiment of the invention. Note that like parts having the same function in this and the first embodiment shown in  FIG. 1  are identified by the same reference numerals, and further description thereof is omitted below. This embodiment differs from the first embodiment in comprising a fifth frequency divider  130  and a sixth frequency divider  131 . 
   When operating in a first frequency (2 GHz) mode, the first oscillator  100  generates a 4-GHz signal, for example, which the fifth frequency divider  130  divides into two 2-GHz carriers foI and foQ with a 90 degree phase difference. The first switching amplifier  106  amplifies carrier foI, and the second switching amplifier  107  amplifies the other 90-degree phase shifted carrier foQ. The amplifier output signals and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109 , which outputs a modulated signal. 
   Output from the orthogonal modulator  109  is then amplified by the first and second amplifiers  110 ,  111 , frequencies outside the required frequency band are removed by the first bandpass filter  116 , and the third amplifier  112  amplifies the transmission signal, which is then passed through the first duplexer  120  and mode switch  122  and transmitted from the external antenna  123 . 
   The sixth frequency divider  131  frequency divides the output of the fifth frequency divider  130  to a 1-GHz signal which is then amplified by the third switching amplifier  108 . The amplified signal is then frequency divided to a comparison frequency by the frequency synthesizer (variable frequency divider)  118 , which compares the result with an externally supplied reference frequency and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the first oscillator  100 . This loop stabilizes the frequency of the carrier wave output from the first oscillator  100 . 
   When operating in the second frequency mode (800 MHz) the second oscillator  101  produces a 3.2-GHz signal, which is frequency divided by the fifth and sixth frequency dividers  130 ,  131  into two 800-MHz carriers foI and foQ with a 90-degree phase difference. The first switching amplifier  106  amplifies carrier foI, and the second switching amplifier  107  amplifies the other 90-degree phase shifted carrier foQ. The amplifier output signals and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109 , which outputs a modulated signal. 
   This output from the orthogonal modulator  109  is then amplified by fourth and fifth amplifiers  113 ,  114 , frequencies outside the required frequency band are removed by the second bandpass filter  117 , and the sixth amplifier  115  amplifies the transmission signal, which is then passed through the second duplexer  121  and mode switch  122  and transmitted from the external antenna  123 . 
   The signal frequency divided to 800-MHz by the sixth frequency divider  131  is then amplified by the third switching amplifier  108 . The frequency synthesizer (variable frequency divider)  118  then divides the amplified signal to a comparison frequency, compares the result with an externally supplied reference frequency, and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the second oscillator  101 . This loop stabilizes the frequency of the carrier wave output from the second oscillator  101 . 
   Note that the 2-GHz mode and 800-MHz mode are used in this second embodiment of the invention by way of example only, and the invention can be used to the same effect when operating at other frequencies. 
     FIG. 5  is a schematic block diagram of a multimode wireless transmitter according to a third embodiment of the invention. Note that like parts having the same function in this and the second embodiment shown in  FIG. 4  are identified by the same reference numerals, and further description thereof is omitted below. This embodiment differs from the second embodiment in comprising a third oscillator  132 . 
   When operating in a first frequency (2 GHz) mode, the third oscillator  132  generates a 4-GHz signal, which the fifth frequency divider  130  divides into two 2-GHz carriers foI and foQ with a 90 degree phase difference. The first switching amplifier  106  amplifies carrier foI, and the second switching amplifier  107  amplifies the other 90-degree phase shifted carrier foQ. The amplifier output signals and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109 , which outputs a modulated signal. 
   Output from the orthogonal modulator  109  is then amplified by the first and second amplifiers  110 ,  111 , frequencies outside the required frequency band are removed by the first bandpass filter  116 , and the third amplifier  112  amplifies the transmission signal, which is then passed through the first duplexer  120  and mode switch  122  and transmitted from the external antenna  123 . 
   The sixth frequency divider  131  frequency divides the output of the fifth frequency divider  130  to a 1-GHz signal which is then amplified by the third switching amplifier  108 . The amplified signal is then frequency divided to a comparison frequency by the frequency synthesizer (variable frequency divider)  118 , which compares the result with an externally supplied reference frequency and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the third oscillator  132 . This loop stabilizes the frequency of the carrier wave output from the third oscillator  132 . 
   When operating in the second frequency mode (800 MHz) the third oscillator  132  generates a 3.2-GHz signal, which is frequency divided by the fifth and sixth frequency dividers  130 ,  131  into two 800-MHz carriers foI and foQ with a 90-degree phase difference. The first switching amplifier  106  amplifies carrier foI, and the second switching amplifier  107  amplifies the other 90-degree phase shifted carrier foQ. The amplifier output signals and the baseband signal from the baseband signal processor are input to the orthogonal modulator  109 , which outputs a modulated signal. 
   This output from the orthogonal modulator  109  is then amplified by fourth and fifth amplifiers  113 ,  114 , frequencies outside the required frequency band are removed by the second bandpass filter  117 , and the sixth amplifier  115  amplifies the transmission signal, which is then passed through the second duplexer  121  and mode switch  122  and transmitted from the external antenna  123 . 
   The signal frequency divided to 800-MHz by the sixth frequency divider  131  is then amplified by the third switching amplifier  108 . The frequency synthesizer (variable frequency divider)  118  then divides the amplified signal to a comparison frequency, compares the result with an externally supplied reference frequency, and outputs a signal corresponding to the phase shift. The output from the frequency synthesizer  118  is passed through the loop filter  119  and applied to the third oscillator  132 . This loop stabilizes the frequency of the carrier wave output from the third oscillator  132 . 
   Note that the 2-GHz mode and 800-MHz mode are used in this third embodiment of the invention by way of example only, and the invention can be used to the same effect when operating at other frequencies. 
   A wireless transmitter can also be provided using a multimode wireless transmitter according to any of the foregoing embodiments of the present invention with the first to sixth amplifiers, first and second bandpass filters, and first and second duplexers connected to the output stage of the orthogonal modulator, a mode switch, external antenna, and a receiving means (RX) connected through the first and second duplexers. 
   APPLICATION IN INDUSTRY 
   By not using the intermediate frequency band, a multimode wireless transmitter and a portable wireless device according to the present invention can reduce the number of oscillators and use a common modulator in different operating modes, thereby reducing device size. Furthermore, by using a common orthogonal modulator the number of signal input terminals on the baseband signal processor can also be reduced and adjusting for carrier leakage is easier. The present invention can thus be used as a high frequency integrated circuit in portable wireless communication devices. 
   Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.