Dielectric filter, dielectric duplexer, and communication apparatus

Abstract

A λ/2 resonator comprises an inner conductor formed hole having an inner conductor with both open-ends, formed therein, and λ/4 resonators comprise inner conductor formed holes having inner conductors with one short-circuited ends and the other open ends, respectively. The resonators are coupled, whereby a terminal electrode connected to the vicinity of the one open end of one of the λ/4 resonators functions as an unbalanced terminal, and terminal electrodes connected to both open ends of the λ/2 resonator function as balanced terminals.

1. A dielectric filter, comprising:
 a single dielectric member;  
 a conductor film disposed on the single dielectric member;  
 aan ungrounded λ/2 resonator comprising a strip electrode provided in association with the single dielectric member, resonating substantially at a half wavelength of a predetermined frequency;  
 a λ/4 resonator comprising a strip electrode provided in association with the single dielectric member, resonating substantially at a quarter wavelength of the predetermined frequency;  
 a first terminal comprising a respective strip electrode capacitively connected to the λ/4 resonator and functioning as an unbalanced terminal; and  
 second terminals respectively comprising strip electrodes capacitively connected to the λ/2 resonator and functioning as balanced terminals.  
 
     
     
       2. The dielectric filter according to  claim 1 , wherein said λ/4 resonator has a short-circuited end and an open end, said open end being coupled by a stray capacitance to said conductor film and said short-circuited end being grounded directly to said conductor film. 
     
     
       3. A communication apparatus including the dielectric filter of  claim 1 . 
     
     
       4. The dielectric filter according to  claim 1 , wherein at least one of the λ/2 resonator and the λ/4 resonator comprises a micro-strip line or a strip line. 
     
     
       5. A dielectric duplexer including the dielectric filter of  claim 1 . 
     
     
       6. A communication apparatus including the dielectric duplexer of  claim 5 . 
     
     
       7. A dielectric filter, comprising:
 a single dielectric member;  
 a conductor film disposed on the single dielectric member;  
 aan ungrounded λ/2 resonator comprising a respective strip electrode provided in association with the single dielectric member, resonating substantially at a half wavelength of a predetermined frequency;  
 a first λ/4 resonator comprising a respective strip electrode provided in association with the single dielectric member, and resonating substantially at a quarter wavelength of the predetermined frequency;  
 a second λ/4 resonator comprising a respective strip electrode provided in association with the single dielectric member, and resonating substantially at a quarter wavelength of the predetermined frequency;  
 a first terminal comprising a respective strip electrode capacitively connected to the λ/4 resonator and functioning as an unbalanced terminal and  
 second terminals respectively comprising strip electrodes capacitively connected to the λ/2 resonator and functioning as balanced terminals  
 
       wherein said first and second λ/4 resonators are comb-line coupled to each other, and said second λ/4 resonator and said λ/2 resonator are interdigitally coupled to each other. 
     
     
       8. A dielectric duplexer comprising two filters, one of said filters being the dielectric filter of  claim 7 . 
     
     
       9. A communication apparatus comprising a communication circuit including at least one of a transmitting circuit and a receiving circuit, and connected thereto, the duplexer of  claim 8 . 
     
     
       10. A communication apparatus comprising a communication circuit including at least one of a transmitting circuit and a receiving circuit, and connected thereto, the dielectric filter of  claim 7 . 
     
     
       11. The dielectric filter according to  claim 7 , wherein each said λ/4 resonator has a short-circuited end and an open end, said open end being coupled by a stray capacitance to said conductor film and said short-circuited end being grounded directly to said conductor film.