Antenna duplexer and wireless terminal using the same

Abstract

A technology which can realize a high-performance multiband operation in a compact circuit configuration and is advantageous for a wireless terminal of GSM system for which the further increase of the demands is expected in the future is provided. Provided is a multiband switch type antenna duplexer adopted in a mobile phone used in TDMA system such as the GSM system, in which the signals of respectively different first to fourth frequency bands (GSM 850, EGSM, DCS, PCS) share a single antenna, wherein switching elements such as receive filters and diodes are combined in various ways to perform the high-performance band switch with the minimum number of switching elements. The circuit of this antenna duplexer can realize not only the size reduction of the multiband switch antenna duplexer but also the size reduction and performance improvement of the wireless terminal itself.

1 . An antenna duplexer, comprising: 
 a single antenna terminal for transmitting and receiving signals of respectively different first, second, third and fourth frequency bands;    first means for filtering the signals of the first, second, third and fourth frequency bands received by said single antenna terminal into the signals of the first and second frequency bands and the signals of the third and fourth frequency bands;    second means for filtering the signals of the first and second frequency bands filtered by said first means into the signals of the first frequency band and the signals of the second frequency band;    third means for filtering the signals of the third and fourth frequency bands filtered by said first means into the signals of the third frequency band and the signals of the fourth frequency band; and    first, second, third and fourth output terminals each outputting the signals of the first, second, third and fourth frequency bands filtered by said second means and said third means.    
   
   
       2 . A multiband switch type antenna duplexer in which signals of respectively different first, second, third and fourth frequency bands share a single antenna, 
 wherein, when a transmitting frequency band fT and a receiving frequency band fR of said first, second, third and fourth frequency bands are respectively denoted as fT( 1 ) and fR( 1 ), fT( 2 ) and fR( 2 ), fT( 3 ) and fR( 3 ) and fT( 4 ) and fR( 4 ), in the case where the highest frequency of fT( 1 ), fR( 1 ), fT( 2 ) and fR( 2 ) is lower than the lowest frequency of fT( 3 ), fR( 3 ), fT( 4 ) and fT( 4 ), fT( 1 )<fR( 2 ) and fT( 3 )<fR( 4 ) are satisfied, and fR( 1 ) partially overlaps fT( 2 ) and fR( 3 ) partially overlaps fT( 4 ),    receive filters corresponding to said first and second frequency bands and receive filters corresponding to said third and fourth frequency bands are provided, output terminals for reception are independently formed on an output side of said receive filters, and input terminals on the input side thereof are connected in parallel to each other via a matching circuit and a phase shift circuit, thereby forming first and third parallel connection points,    said first parallel connection point corresponding to said first and second frequency bands is further connected in parallel to a switching element for transmission, which is connected to a common input point on the transmission side corresponding to said first and second frequency bands, becomes conductive at the time of the transmission of the signals of said first or second frequency band, and is released at the time of the reception, via a switching element which is connected to the ground at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a second parallel connection point,    said third parallel connection point corresponding to said third and fourth frequency bands is further connected in parallel to a switching element for transmission, which is connected to a common terminal on the transmission side corresponding to said third and fourth frequency bands, becomes conductive at the time of the transmission of the signals of said third or fourth frequency band, and is released at the time of the reception, via a switching element which is connected to the ground at the time of the transmission of the signals of said third or fourth frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a fourth parallel connection point, and    said second parallel connection point and said fourth parallel connection point are connected in parallel to each other with using an antenna terminal as a common terminal, via a low-frequency pass filter and a high-frequency pass filter, respectively.    
   
   
       3 . The antenna duplexer according to  claim 2 , 
 wherein control current flowing at the time of the transmission of the signals of said first or second frequency band and control current flowing at the time of the transmission of the signals of said third or fourth frequency band are almost equal to each other within the range of ±20% and directly supplied from a baseband IC.    
   
   
       4 . A multiband switch type antenna duplexer in which signals of respectively different first and second frequency bands share a single antenna, 
 wherein, when a transmitting frequency band fT and a receiving frequency band fR of said first and second frequency bands are respectively denoted as fT( 1 ) and fR( 1 ) and fT( 2 ) and fR( 2 ), in the case where fT( 1 )<fR( 2 ) is satisfied and fR( 1 ) partially overlaps fT( 2 ),    receive filters corresponding to said first and second frequency bands are provided, input terminals on the input side of said receive filters are connected in parallel to each other via a matching circuit and a phase shift circuit, thereby forming a first parallel connection point,    said first parallel connection point is connected in parallel to a switching element for transmission, which is connected to a common input terminal on the transmission side corresponding to said first and second frequency bands, becomes conductive at the time of the transmission of the signals of    said first or second frequency band, and is released at the time of the reception, via a switching element which is connected to the ground at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a second parallel connection point,    said second parallel connection point is directly connected to an antenna terminal or connected to the antenna terminal via a low-frequency pass filter or a high-frequency pass filter, and    the output terminal of the receive filter corresponding to said first frequency band and the output terminal of the receive filter corresponding to said second frequency band are connected in parallel to each other, via a switching element which becomes conductive at the time of the reception of the signals of said first frequency band and is released at the time of the reception of the signals of said second frequency band and via a switching element which is connected to the ground at the time of the reception of the signals of said first frequency band and becomes conductive at the time of the reception of the signals of said second frequency band and a quarter wavelength phase shift circuit, respectively, thereby forming a third parallel connection point, and said third parallel connection point is used as an output terminal for reception.    
   
   
       5 . A multiband switch type antenna duplexer in which signals of respectively different first and second frequency bands share a single antenna, 
 wherein, when a transmitting frequency band fT and a receiving frequency band fR of said first and second frequency bands are respectively denoted as fT( 1 ) and fR( 1 ) and fT( 2 ) and fR( 2 ), in the case where fT( 1 )<fR( 2 ) is satisfied and fR( 1 ) partially overlaps fT( 2 ),    receive filters corresponding to said first and second frequency bands are provided, input terminals on the output side of said receive filters are connected in parallel to each other via a matching circuit and a phase shift circuit, thereby forming a third parallel connection point, and said third parallel connection point is used as an output terminal for reception,    the input terminal of the receive filter corresponding to said first frequency band and the input terminal of the receive filter corresponding to said second frequency band are connected in parallel to each other, via a switching element which becomes conductive at the time of the reception of the signals of said first frequency band and is released at the time of the reception of the signals of said second frequency band and via a switching element which is connected to the ground at the time of the reception of the signals of said first frequency band and becomes conductive at the time of the reception of the signals of said second frequency band and a quarter wavelength phase shift circuit, respectively, thereby forming a first parallel connection point,    said first parallel connection point is connected in parallel to a switching element for transmission, which is connected to a common input terminal on the transmission side corresponding to said first and second frequency bands, becomes conductive at the time of the transmission of the signals of said first or second frequency band, and is released at the time of the reception, via a switching element which is connected to the ground at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a second parallel connection point, and    said second parallel connection point is directly connected to an antenna terminal or connected to the antenna terminal via a low-frequency pass filter or a high-frequency pass filter.    
   
   
       6 . A multiband switch type antenna duplexer in which signals of respectively different first and second frequency bands share a single antenna, 
 wherein a receive filter corresponding to said first frequency band and a switching element for reception corresponding to said second frequency band, which becomes conductive at the time of the reception of the signals of said second frequency band and is released in other cases, are provided, output terminals for reception are independently formed on the output side of said receive filter and said switching element for reception, and said receive filter is connected in parallel to said switching element for reception on the input side via a matching circuit and a phase shift circuit but said switching element for reception is directly connected to said receive filter, thereby forming a first parallel connection point,    said first parallel connection point is further connected in parallel to a switching element for transmission, which is connected to a common input terminal on the transmission side corresponding to said first and second frequency bands, becomes conductive at the time of the transmission of the signals of said first or second frequency band, and is released at the time of the reception, via a switching element which is connected to the ground at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a second parallel connection point, and    said second parallel connection point is directly connected to an antenna terminal or connected to the antenna terminal via a low-frequency pass filter or a high-frequency pass filter.    
   
   
       7 . The antenna duplexer according to  claim 6 , 
 wherein a receive filter is externally attached to the output terminal for reception corresponding to said second frequency band according to need.    
   
   
       8 . A multiband switch type antenna duplexer in which signals of respectively different first and second frequency bands share a single antenna, 
 wherein receive filters corresponding to said first frequency band and said second frequency band are provided, output terminals for reception are independently formed on the output side of said receive filters, and input terminals on the input side thereof are connected in parallel to each other via a matching circuit and a phase shift circuit, thereby forming a first parallel connection point,    said first parallel connection point is connected in parallel to a switching element for transmission, which is connected to a common input terminal on the reception side corresponding to said first and second frequency bands, becomes conductive at the time of the transmission of the signals of said first or second frequency band, and is released at the time of the reception, via a switching element which is connected to the ground via a resistor at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit and further via a switching element which is connected to the ground at the time of the transmission of the signals of said first or second frequency band and becomes conductive at the time of the reception and a quarter wavelength phase shift circuit, thereby forming a second parallel connection point, and    said second parallel connection point is directly connected to an antenna terminal or connected to the antenna terminal via a low-frequency pass filter or a high-frequency pass filter.    
   
   
       9 . The antenna duplexer according to  claim 2 , 
 wherein a balun circuit for converting a single-ended output to a balanced output is connected to a front stage of at least one of the output terminals for reception, and a receiving signal is outputted via a differential output terminal.    
   
   
       10 . The antenna duplexer according to  claim 9 , 
 wherein said balun circuit is comprised of a circuit composed of a serial arm inductance and a parallel arm capacitance from an input side between said input side and one of said differential output terminals and a circuit composed of a serial arm capacitance and a parallel arm inductance from said input side between said input side and the other of said differential output terminals, or said balun circuit is comprised of a circuit composed of a serial arm inductance, a parallel arm capacitance, a serial arm inductance, and a parallel arm capacitance from said input side between said input side and one of said differential output terminals and a circuit composed of a serial arm capacitance, a parallel arm inductance, a serial arm capacitance, and a parallel arm inductance from said input side between said input side and the other of said differential output terminals.    
   
   
       11 . The antenna duplexer according to  claim 2 , 
 wherein said receive filter is comprised of a SAW filter or a FBAR filter, and said switching element is comprised of a pin diode switch, a GaAs switch or a MEMS switch.    
   
   
       12 . A wireless terminal using the antenna duplexer according to  claim 1 , 
 wherein said wireless terminal is a GSM mobile phone based on a TDMA system, and a direct conversion system or a low IF system is used as a demodulation system.