Signals at different carrier frequencies are used in various applications, such as multi-band RF signals used in wireless and other communication devices or systems. Examples of multi-band RF communication technologies include CDMA bands BC0/1, GSM bands 2/3/5/8, WCDMA bands 1/2/4/5/6/8, LTE bands 1/2/3/4/5/7/8/12/13/17/20/25/26/38/40/41, GPS, Wi-Fi (2.4 GHz and 5 GHz bands), and others.
Various commonly used multi-band multi-radio system designs are based on a combination of multiple single-bandpass filters (or duplexers) and switches for handling multi-band radio operations, such as out-of-band noise floor and spur, antenna isolation. Such single-bandpass filters are discrete devices and are typically used to separately filter their corresponding RF signals at different RF carrier frequencies, respectively.