Introduction
RF front ends of mobile phones are getting more complex to accommodate evolving technologies such as carrier aggregation, MIMO and etc. More integrated RF solutions are necessary to realize advanced technologies within crowd phone space. IPD (Integrated Passive Device) is one of the promising solution to help reducing size and cost, increasing functionality for RF front-ends. With the mature and advanced IC fabrication process, IPDs can be developed significantly smaller, thinner, with greater performance and consistency than conventional passive devices.
Xpeedic provides full kinds of passive devices with IPD technology, including filters, diplexers, baluns, couplers, attenuators and etc. with packages such as wire-bonding/flip-chip die, WLCSP. Many of them are developed for mobile phone applications.
Front-End Module Block Diagram
The following diagram demonstrates a typical cell phone FEM. Many passive parts of the front end can be developed with IPD, helping size reduction and function integration.
Harmonic suppression LPF
Transmitters output harmonic tones along with the operating tone. In many cases, especially for high power GSM, low-pass filters are used to suppress the harmonics. IPD LPFs are of low IL, great harmonic suppression and compact size which is perfect candidates for the application.
The typical example of a GSM LPF below shows 2nd and 3rd harmonic suppression.
Xpeedic develops compact and application specific IPD LPFs. A typical Xpeedic IPD LPF gets > 20dB harmonic suppression and < 0.5dB signal loss with small footprint.
CA Diplexer
CA (Carrier Aggregation) is an important technological innovation to efficiently use the spectrum and expand data bandwidth. More spectrum is getting aggregated, including the ISM bands, to further improve data throughput. This brings challenge to RF front ends to operate simultaneously at these separated frequency bands. Multiplexing antenna is one of the solutions to operate at different carriers with compact RF FEM size.
The diagram below shows a CA diplexer combining signal from different frequency bands and feeding to one wideband antenna. The CA diplexer also offers out-of-band rejection and inter-band isolation. A matched CA diplexer is also possible to add matching between antenna and its front end to maximize power transfer within compact size.
The below chart demonstrates performance of a typical Xpeedic CA diplexer. More detailed information can be found in Xpeedic website.
Directional Coupler
Directional coupler is utilized to detect the output power despite the load impedance variation. In phones, the antenna impedance varies in different use occasions, such as handheld, close to head or laid on desk. To accurately measure the output power in all cases, a directional coupler is needed. The figure below shows a directional coupler sampling input and reflected power in a directional manner.
Xpeedic IPD couplers are of compact size and wide bandwidth covering 450MHz-3800MHz. More detailed information can be found in Xpeedic website.
Matching Network RF engineers work much for matching. Matching is important for RF FEM in phones to maximize power transfer and save battery life. Matching networks can be complex, bulk and lossy with great transform ratio, high impedance Q and wide frequency bandwidth. IPD MN can be accurate and compact in size, and ready for integration with other devices, such as diplexers, filters, baluns, antennas and etc. to get an integrated compact matched RF FEM. Matching networks are highly application specific, we encourage direct contact to regional Xpeedic sales for further information. Packaging Based on IC process, IPD devices are ready for packaging with other IC dies and integrated as one SiP (System in Package) module which is the main application method of IPD. IPD die can be packaged aside other dies or stacked upon or under other dies to get more compact packaging. Flip-chip or wire-bonded, IPD can be integrated into various RF FEMs such as switch modules or PA modules. IPD die can be packaged alone as a discrete SMT passive device, ready for PCB level usage. Several IPD dies can be packaged together to compose a passive system, integrating complex passive functions such as filtering-matching-balun, matching-diplexer, antenna feeding matrix and etc. Below charts show several IPD packaging methods, and many more options are available regarding packaging and SiP, application specifically, please contact Xpeedic sales for more information.
