# US 2013/0154868 A1 · System and Method for an RF Receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154868 A1 - Document ID: US20130154868A1 - Status: Published application - Kind: A1 - Application number: 13/325,935 - Filed: 2011-12-14 - Published: 2013-06-20 - Earliest claimed: 2011-12-14 - Assignees: Infineon Technologies AG - Inventors: Daniel Kehrer; Kai Jung - Web page: https://patentgrep.com/patent/US20130154868A1 ## CPC - H04B 1/1036: {with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters (H04B1/123 takes precedence; filter circuits H03H)} - H04B 1/109: {by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input} - H04B 1/18: Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H) - H03H 7/0115: {comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence)} - H03H 7/1758: {Series LC in shunt or branch path (H03H7/1791 takes precedence)} - H03H 7/1766: {Parallel LC in series path (H03H7/1783 takes precedence)} - H04B: TRANSMISSION - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) ## Abstract In accordance with an embodiment, a radio-frequency (RF) front-end for a radio configured to receive an RF signal at a first frequency includes an antenna port configured to be coupled to an antenna, and a notch filter having an input coupled to the antenna port. The notch filter is configured to reject one or more frequencies, such that the first frequency is a harmonic or intermodulation distortion product of the one or more frequencies. The RF front-end also includes a piezoelectric filter having an input coupled to an output of the notch filter and an output configured to be coupled to an RF amplifier. The piezoelectric filter has a pass band comprising the first frequency. ## Claims ### Claim 1 A radio-frequency (RF) front-end for a radio configured to receive an RF signal at a first frequency, the RF front-end comprising: an antenna port configured to be coupled to an antenna; a notch filter having an input coupled to the antenna port, the notch filter configured to reject one or more frequencies, wherein the first frequency is a harmonic or intermodulation distortion product of the one or more frequencies; and a piezoelectric filter having an input coupled to an output of the notch filter and an output configured to be coupled to an RF amplifier, the piezoelectric filter having a pass band comprising the first frequency. ### Claim 2 (depends on 1) The RF front-end of claim 1, further comprising a low-noise amplifier (LNA) having an input coupled to an output of the piezoelectric filter. ### Claim 3 (depends on 1) The RF front-end of claim 1, wherein the notch filter comprises a lumped element notch filter. ### Claim 4 (depends on 3) The RF front-end of claim 3, wherein the lumped element notch filter comprises a first parallel LC tank coupled in series between the antenna port and the input of the piezoelectric filter. ### Claim 5 (depends on 4) The RF front-end of claim 4, wherein the lumped element notch filter further comprises a series LC tank coupled between the input of the piezoelectric filter and a reference voltage. ### Claim 6 (depends on 5) The RF front-end of claim 5, wherein: the first parallel LC tank comprises a first end coupled to the antenna port and a second end coupled to the input of the piezoelectric filter; and the series LC tank is coupled between the second end of the first parallel LC tank and the reference voltage. ### Claim 7 (depends on 4) The RF front-end of claim 4, wherein the series LC tank comprises a different center frequency from the first parallel LC tank. ### Claim 8 (depends on 4) The RF front-end of claim 4, wherein the lumped element notch filter comprises one or more discrete inductors and capacitors coupled to a circuit board. ### Claim 9 (depends on 4) The RF front-end of claim 4, wherein the lumped element notch filter is disposed on an integrated passive die (IPD). ### Claim 10 (depends on 1) The RF front-end of claim 1, wherein the first frequency is in a Global Navigation Satellite System (GNSS) frequency band. ### Claim 11 (depends on 1) The RF front-end of claim 1, wherein the piezoelectric filter comprises a surface acoustic wave (SAW) filter. ### Claim 12 (depends on 1) The RF front-end of claim 1, wherein the first frequency is a second harmonic of the one or more frequencies. ### Claim 13 (depends on 1) The RF front-end of claim 1, wherein the notch filter presents a high impedance to the antenna port within a cellular communication band or within in a wireless LAN band. ### Claim 14 A radio-frequency (RF) front-end module comprising: a lumped element notch filter having an input coupled to an input port of the front-end module, the lumped element notch filter configured to reject a first frequency; a piezoelectric filter having an input coupled to an output of the lumped element notch filter, the piezoelectric filter having a pass band that includes a second frequency, the second frequency being a harmonic of the first frequency; and an RF amplifier coupled to an output of the piezoelectric filter. ### Claim 15 (depends on 14) The front-end module of claim 14, wherein the second frequency is a second harmonic of the first frequency. ### Claim 16 (depends on 14) The front-end module of claim 14, wherein the piezoelectric filter comprises a surface acoustic wave (SAW) filter. ### Claim 17 (depends on 14) The front-end module of claim 14, wherein the lumped element notch filter comprises: a parallel resonant LC tank having a first end coupled to the input port and a second end coupled to an input of the RF amplifier; and a series resonant LC tank having a first end coupled to the second end of the parallel resonant LC tank and a second end coupled to a reference voltage. ### Claim 18 (depends on 17) The front-end module of claim 17, wherein the parallel resonant LC tank and the series resonant LC tank comprise discrete inductors and capacitors. ### Claim 19 (depends on 17) The front-end module of claim 17, wherein the parallel resonant LC tank and the series resonant LC tank in integrated in an integrated passive die (IPD). ### Claim 20 (depends on 14) The front-end module of claim 14, wherein the front-end module is a front-end module for a Global Navigation Satellite System (GNSS) receiver. ### Claim 21 (depends on 20) The front-end module of claim 20, wherein the GNSS receiver is a Global Positioning System (GPS) receiver. ### Claim 22 A radio frequency system (RF) comprising: a lumped element notch filter having an input coupled to an input port of the RF system, the lumped element notch filter configured to reject one or more frequencies; a piezoelectric filter having an input coupled to an output of the lumped element notch filter, the piezoelectric filter having a pass band that includes a second frequency, the second frequency being a harmonic or intermodulation distortion product of the one or more frequencies; and an RF amplifier coupled to an output of the piezoelectric filter. ### Claim 23 (depends on 22) The RF system of claim 22, wherein the lumped element notch filter comprises: a parallel resonant LC tank having a first end coupled to the input port and a second end coupled to an input of the RF amplifier; and a series resonant LC tank having a first end coupled to the second end of the parallel resonant LC tank and a second end coupled to a reference voltage. ### Claim 24 (depends on 22) The RF system of claim 22, further comprising a radio receiver coupled to an output of the RF amplifier. ### Claim 25 (depends on 24) The RF system of claim 24, wherein the radio receiver comprises a Global Navigation Satellite System (GNSS) receiver. ### Claim 26 A method of processing a radio frequency (RF) signal at a first frequency, the method comprising: receiving the RF signal; notch filtering the RF signal at one or more frequencies using a lumped element notch filter to produce a first filtered signal; filtering the first filtered signal with a piezoelectric filter to produce a second filtered signal, the piezoelectric filter having a passband including a second frequency, wherein the second frequency is a harmonic or intermodulation distortion product of the one or more frequencies; and amplifying the second filtered signal with an RF amplifier. ### Claim 27 (depends on 26) The method of claim 26, wherein notch filtering the RF signal at the one or more frequencies using the lumped element notch filter comprises filtering with a parallel resonant LC tank having a first end coupled to an input to a system, and a second end coupled to an input of the RF amplifier, and filtering with a series resonant LC tank having a first end coupled to the second end of the parallel resonant LC tank and a second end coupled to a reference voltage.