Devices and Methods for Duplexer Loss Reduction

Abstract

Methods and devices are described for reducing transmit RF signal loss in a bi-directional RF transmit/receive system with a duplexer circuit. In one case a filter in a transmit path is used such as to reduce amplified noise in a receive frequency band.

1 . A radio frequency (RF) circuital arrangement comprising:
 an RF transmit path comprising:
 a plurality of cascaded amplifiers configured, during operation of the circuital arrangement, to amplify a transmit RF signal, the transmit RF signal operating over a first frequency band, and 
 a first filter placed between two consecutive amplifiers of the plurality of cascaded amplifiers, the first filter configured during operation of the circuital arrangement, to attenuate a second frequency band different from the first frequency band, and pass the first frequency band: 
   an RF receive path configured, during operation of the circuital arrangement, to receive a receive RF signal over the second frequency band, and   a bi-directional transmit/receive circuit connected to the RF transmit path and to the RF receive path, the bi-directional transmit/receive circuit comprising:
 a second filter configured, during operation of the circuital arrangement, to pass the first frequency band and to attenuate the second frequency band. 
   
     
     
         2 . The RF circuital arrangement of  claim 1 , wherein:
 an attenuation over the first frequency band provided by the first filter is less than about 5 dB, and   an attenuation over the second frequency band provided by the first filter is greater than about 10 dB.   
     
     
         3 . The RF circuital arrangement of  claim 1  or  claim 2 , wherein an attenuation over the second frequency band provided by the combination of the first filter and the second filter is greater than about 35 dB. 
     
     
         4 . The RF circuital arrangement of  claim 1 , wherein, during operation of the circuital arrangement, the hi-directional transmit/receive circuit is configured:
 to provide an amplified version of the transmit RF signal from the RF transmit path to a transmit/receive antenna, and   to receive the receive RF signal from the transmit/receive antenna and provide said signal to the RF receive path.   
     
     
         5 . The RF circuital arrangement of  claim 1 , wherein the first frequency band and the second frequency band are in correspondence of a mode of operation of the circuital arrangement, and wherein the circuital arrangement is configured, during operation of the circuital arrangement, to operate in one of a plurality of modes of operation comprising a plurality of different first frequency band and second frequency band. 
     
     
         6 . The RF circuital arrangement of  claim 5 , wherein the first filter is a tunable tilter configured, during operation of the circuital arrangement, to be tuned to attenuate a second frequency band and pass a first frequency band in correspondence of a mode of operation of the plurality of modes of operation of the circuital arrangement. 
     
     
         7 . The RF circuital arrangement of  claim 6 , wherein the first filter and the second filter are RLC type filters. 
     
     
         8 . The RF circuital arrangement of  claim 6 , wherein the first tilter is an RLC type filter. 
     
     
         9 . The RF circuital arrangement of  claim 3 , wherein the first filter and the second filter are RLC type filters. 
     
     
         10 . The RF circuital arrangement of  claim 1 , wherein the first filter comprises one or more of: a) a digitally tunable capacitor, and b) a digitally tunable inductor. 
     
     
         11 . The RF circuital arrangement of  claim 7 , wherein the first filter comprises one or more of: a) a digitally tunable capacitor, and b) a digitally tunable inductor. 
     
     
         12 . The RF circuital arrangement of  claim 7 , wherein the first filter is one of: a) a low-pass filter, b) a high-pass filter, c) a band-pass filter, d) a band-stop filter, and e) a notch filter. 
     
     
         13 . The RF circuital arrangement of  claim 1 , wherein the first filter is one of: a) a low-pass filter, b) a high-pass filter, c) a band-pass filter, d) a band-stop filter, and e) a notch filter. 
     
     
         14 . The RF circuital arrangement of any one of  claims 1 ,  2 , or  7 , wherein the bi-directional transmit/receive circuit is a duplexer circuit comprising the second filter, and wherein the second filter is designed with relaxed parameters, wherein the relaxed parameters reduce a number of filter stages of the second filter. 
     
     
         15 . The RF circuital arrangement of  claim 14 , wherein the reduced number of filter stages of the second filter provide a reduced attenuation of the second filter in the first frequency band. 
     
     
         16 . The RF circuital arrangement of  claim 15 , wherein the reduced attenuation of the second filter in the first frequency band is less than about 2 dB. 
     
     
         17 . The RF circuital arrangement of  claim 14 , wherein the duplexer circuit further comprises a third filter coupled to the receive path and configured, during operation of the circuital arrangement, to pass the second frequency band. 
     
     
         18 . The RF circuital arrangement of  claim 1 , wherein the plurality of cascaded amplifiers and the first filter are monolithically integrated. 
     
     
         19 . The RF circuital arrangement of  claim 7 , wherein the plurality of cascaded amplifiers and the first and/or second filter are monolithically integrated. 
     
     
         20 . The circuital arrangement of  claim 9 , wherein the plurality of cascaded amplifiers and the first and/or second filter are monolithically integrated. 
     
     
         21 . The RF circuital arrangement of  claim 1 , wherein the plurality of cascaded amplifiers comprises a first amplifier configured to receive the RF transmit signal into the plurality of cascaded amplifiers, and a last amplifier configured to output an amplified version of the RF transmit signal by the plurality of cascaded amplifiers, and wherein the first filter is configured to attenuate an amplified noise figure at the second frequency band. 
     
     
         22 . The RF circuital arrangement of  claim 1 , further comprising one or more filters similar to the first filter, the one or more filters placed between one or more two consecutive amplifiers of the plurality of amplifiers, the one or more filters and the first filter not being directly connected, wherein the one or more filters are configured during operation of the circuital arrangement, to attenuate the second frequency band and pass the first frequency band. 
     
     
         23 . The RF circuital arrangement of  claim 1 , wherein the plurality of cascaded amplifiers comprises a driver amplifier and a final amplifier, and wherein the first filter is placed between the driver amplifier and the final amplifier. 
     
     
         24 . A communication device for bi-directional transmit and receive of RF signals, the communication device comprising the RF circuital arrangement of  claim 6 . 
     
     
         25 . The communication device of  claim 24  further comprising a transceiver unit, wherein during operation of the communication device, the transceiver unit is adapted to tune the tunable filter according to the mode of operation. 
     
     
         26 . A method for reducing loss of a transmit RF signal in a duplexer unit of an radio frequency (RF) transmit/receive system, the method comprising:
 providing an RF transmit path comprising a plurality of cascaded amplifiers;   inserting, in-between two amplifiers of the plurality of cascaded amplifiers, a first filter;   based on the inserting, attenuating a receive frequency band and passing a transmit frequency band:   based on the attenuating, relaxing design parameters of a second filter of a duplexer unit, the second filter being configured to pass the transmit frequency band and to attenuate the receive frequency band;   based on the relaxing, reducing a number of filter stages of the second filter, and   based on the reducing, reducing an attenuation at the transmit frequency band through the second filter of the duplexer unit.   
     
     
         27 . The method of  claim 26 , wherein the plurality of cascaded amplifiers comprises two amplifiers; a driver amplifier and a final amplifier, and wherein the first filter is inserted between the driver amplifier and the final amplifier. 
     
     
         28 . The method of claim  0  or  claim 27 , further comprising:
 coupling the second filter of the duplexer unit at an output of the plurality of cascaded amplifiers of the RF transmit path; 
 based on the coupling, isolating an RF receive path operating at the receive frequency band from a signal at the output of the plurality of cascaded amplifiers, the RF receive path being coupled to a third filter of the duplexer unit, and 
 based on the coupling, reducing an attenuation of a transmit RF signal via the RF transmit path. 
 
     
     
         29 . The method of  claim 28 , wherein the duplexer unit is coupled to a transmit/receive antenna, and wherein the duplexer unit is configured to receive an RF signal at the receive frequency hand and feed said RF signal to the RF receive path. 
     
     
         30 . The method of  claim 28 , wherein the third filter is configured to pass the receive frequency band and to attenuate the transmit frequency band. 
     
     
         31 . The method of  claim 26 , wherein the first filter is a tunable filter. 
     
     
         32 . The method of  claim 31 , further comprising:
 selecting a different receive frequency band and transmit frequency band, and   based on the selecting, tuning the first filter to attenuate the different receive frequency band and pass the different transmit frequency band,   wherein the second filter is configured to pass the different transmit frequency band and attenuate the different receive frequency band.   
     
     
         33 . The method of  claim 32 , wherein the selecting is in correspondence of a desired mode and/or channel of operation from a plurality of modes and/or channels of operation of the RF transmit/receive system, and wherein the second filter is configured to pass a plurality of transmit frequency hands and attenuate a plurality of receive frequency bands in correspondence of the plurality of modes and/or channels of operation of the RF transmit/receive system. 
     
     
         34 . The method of  claim 32 , wherein the tuning is performed by a controller unit aware of the different receive and transmit frequency bands. 
     
     
         35 . The method of  claim 34 , wherein the selecting and the tuning is performed by a transceiver unit of the RF transmit/receive system. 
     
     
         36 . The RF circuital arrangement of  claim 26 , wherein the second filter is an RLC type filter. 
     
     
         37 . The RF circuital arrangement of  claim 26 , wherein the first and the second filter are RLC type filters. 
     
     
         38 . The RF circuital arrangement of  claim 31 , wherein the first filter comprises one or more of: a) a digitally tunable capacitor, and b) a digitally tunable inductor. 
     
     
         39 . The RF circuital arrangement of  claim 37 , wherein the first filter is one of: a) a low-pass filter, b) a high-pass filter, c) a band-pass filter, d) a band-stop filter, and e) a notch filter.