3. TECHNICAL BRIEF

3.3 UMTS Mode

3.3.1 Receiver

The UMTS duplexer receiver output is routed to LNA circuits within the RTR6275 device. The UMTS Rx input is provided with an on-chip LNA that amplifies the signal before a second stage filter that provides differential downconverter. This second stage input is configured differentially to optimize second-order intermodulation and common mode rejection performance. The gain of the UMTS frontend amplifier and the UMTS second stage differential amplifier are adjustable, under MSM control, to extend the dynamic range of the receivers. The second stage UMTS Rx amplifiers drive the RF ports of the quadrature RF- tobaseband downconverters. The downconverted UMTS Rx baseband outputs are routed to lowpass filters having passband and stopband characteristics suitable for UMTS Rx processing. These filter circuits allow DC offset corrections, and their differential outputs are buffered to interface shared with GSM Rx to the MSM IC. The UMTS baseband outputs are turned off when the RTR6275 is downconverting GSM signals and on when the UMTS is operating.

3.3.2 Transmitter

The UMTS Tx path begins with differential baseband signals (I and Q) from the MSM device. These analog input signals are amplified, filtered, and applied to the quadrature up-converter mixers. The up- converter output is amplified by multiple variable gain stages that provide transmit AGC control. The AGC output is filtered and applied to the driver amplifier; this output stage includes an integrated matching inductor that simplifies the external matching network to a single series capacitor to achieve the desired 50-Ω interface.

The RTR6275 UMTS output is routed to its power amplifier through a bandpass filter, and delivers fairly high-level signals that are filtered and applied to the PA. Transmit power is delivered from the duplexer to the antenna through the switch module. The transceiver LO synthesizer is contained within the RTR6275 IC with the exception of the off-chip loop filter components and the VC-TCXO. This provides a simplified design for multimode applications. The PLL circuits include a reference divider, phase detector, charge pump, feedback divider, and digital logic generator.

UMTS Tx using PLL1, the LO generation and distribution circuits create the necessary LO signals for different frequency converters. The UMTS transmitter also employs the ZIF architecture to translate the signal directly from baseband to RF. This requires FLO to equal FRF, and the RTR6275 IC design achieves this without allowing FVCO to equal FRF.

The RTR6275 IC is able to support UMTS 2100/1900 and UMTS 850 mode transmitting. This design guideline shows only UMTS 2100 applications.

- 23 -

Page 22
Image 22
LG Electronics U250 service manual Umts Mode, Receiver, Transmitter

U250 specifications

The LG Electronics U250 is a distinguished device known for its cutting-edge features and innovative technologies within the mobile phone sector. Launched as part of LG's effort to cater to a growing demand for functional yet stylish smartphones, the U250 boasts an array of characteristics that appeal to a savvy clientele.

One of the primary features of the U250 is its impressive display. Sporting a vibrant screen that offers excellent color reproduction and clarity, it enhances the user experience for gaming and multimedia consumption. The responsive touchscreen interface allows for seamless navigation, making it user-friendly for all age groups.

The U250 is powered by a robust processor that ensures smooth performance, whether multitasking between applications or running demanding games. With ample RAM, it minimizes lag and enhances the overall operating experience, allowing users to switch effortlessly between tasks.

Photography enthusiasts will appreciate the U250's advanced camera system. It is equipped with a high-resolution primary camera that captures stunning images in various lighting conditions. The inclusion of features like autofocus and image stabilization significantly elevates the quality of photos and videos. Additionally, the front-facing camera is designed for high-quality selfies and video calls, ensuring that users can always stay connected.

The device supports a range of connectivity options, including 4G LTE, Bluetooth, and Wi-Fi, ensuring users can remain connected to the world around them. The integration of NFC technology also enables quick and convenient transactions, particularly useful in a cashless society.

Battery life is another standout characteristic of the U250. With a durable battery, it offers extended usage time, allowing users to go through their day without the constant worry of recharging. Coupled with fast-charging capabilities, it reduces downtime significantly.

The LG U250 runs on an intuitive operating system that provides easy access to a plethora of apps on the platform. Customization options are abundant, allowing users to tailor their device's appearance and functionality to suit their preferences.

In conclusion, the LG Electronics U250 combines striking design with versatile functionality, making it a formidable entry in the smartphone market. With its impressive display, powerful performance, advanced camera features, and strong battery life, the U250 is poised to meet the needs of modern users seeking both style and substance in a mobile device. Whether for work or leisure, this smartphone is designed to enhance everyday life.