The transition from 3G to LTE-Advanced introduces a range of complex challenges for equipment and device manufacturers in the development of next-generation mobile communication infrastructure. As wireless devices evolve, they require wider signal bandwidths and more sophisticated modulation techniques to support higher data rates across various global frequency bands. This shift places greater emphasis on critical performance factors such as noise, signal linearity, power consumption, and compact form factor—requirements that are more stringent than ever before. Additionally, component suppliers must also meet demands for smaller and more cost-effective components to enable higher integration density in modern systems.
RF IC designers face increasing complexity as integrated solutions must match or exceed the performance of discrete components. While system designers can leverage different technologies like GaAs, Si Bipolar, or CMOS for optimal design in discrete implementations, RF IC designers working with a single process technology must balance performance with flexibility. Choosing the right process becomes a significant challenge, as it needs to support high-performance RF functions without compromising integration or scalability.
In the base station transmitter, the analog I/Q modulator is a crucial RF IC component that determines the noise floor and linearity of the transmit path. It must maintain high performance while reducing size, power, and cost. This makes it a key element in achieving efficient and reliable wireless communication systems.
Thankfully, SiGe BiCMOS process technology offers a powerful solution by enabling higher levels of integration without sacrificing performance. These processes typically feature SiGe NPN transistors in various speed grades, and often include twice as many complementary PNP transistors as CMOS transistor sizes. Additional features like MIM capacitors, thin-film resistors, and multi-layer copper or aluminum metal layers further enhance design capabilities. This allows engineers to implement multiple high-performance blocks on a single chip, significantly reducing power consumption and physical size while maintaining superior performance.
One critical aspect of transmitter board-level design involves the synthesis and distribution of local oscillator (LO) clocks for upconversion and downconversion circuits. The LO clock must be phase-locked across all remote locations on the PCB, with low in-band noise, wideband noise, and minimal spurious signals. The performance of the mixer is directly tied to the quality of the LO signal, making a high-quality LO essential for overall system performance. Even small amounts of phase noise or spurious components in the LO can cause interference, potentially leading to failure in meeting cellular communication standards such as MC-GSM, WCDMA, LTE, and WiMAX. These standards typically require LO frequencies between 500 MHz and 4 GHz, which demands careful PCB layout for LO distribution. However, keeping LO traces short becomes challenging when the synthesizer must feed multiple devices, often requiring additional space on the board.
The ADRF670x family of integrated modulators addresses many of these challenges by incorporating advanced fractional-N PLLs and VCOs. Utilizing silicon germanium technology, these devices achieve industry-leading dynamic range and competitive performance in a much smaller footprint compared to external VCO/PLL solutions. The VCO is implemented in the upper thick metal layer, allowing the use of high-Q on-chip inductors in the LC circuit. MOS switch-type MIM capacitors are used for the VCO capacitor, enabling wide frequency tuning with low phase noise. The frequency band automatically adjusts each time the PLL is programmed, offering an independent and reliable solution. After initialization, the band size is chosen to ensure operation over the full temperature range. Thick metal layers also allow the integration of an output balun with excellent reflection loss. The ADRF670x family includes four members covering a frequency range from 400 MHz to 3 GHz, with each device defined by the Balun bandwidth on the 1dB and 3dB passbands.
The ADRF670x and ADRF660x families of fractional-N PLL designs are ideal for low-phase-noise applications in 3G and 4G systems. Newer cellular standards feature dense signal constellations that demand increasingly lower LO phase noise for adequate performance. Traditional integer-N PLLs generate large frequency steps by multiplying the reference frequency, which amplifies phase noise and increases in-band noise at the output. Fractional-N PLLs, however, allow smaller frequency steps with a lower total multiplier, reducing phase noise amplification and improving overall signal quality.
Adjacent Channel Power Ratio (ACPR) is a key metric that measures how much of the transmitted signal leaks into adjacent frequency bands. Standards like WCDMA impose strict limits on out-of-band transmit power. The ACPR of the ADRF6702 is shown in Figure 3, where it achieves an impressive -76 dBc at the -6 dBm output point. This high linearity and low noise help reduce the gain stage after the modulator and maximize the dynamic range before the final power amplifier stage.
The ADRF670x family integrates three LDO regulators to operate from a single 5V supply, simplifying system design, lowering costs, and saving board space. These LDOs provide stable power to the VCO, charge pump, and PLL delta-sigma modulators. The +5V supply can be directly used in the IQ modulator to maximize output power, enhancing system efficiency.
In high-density applications, the ADL670x can internally synthesize the local oscillator using its PLL, while other devices can disable their PLL and use a shared LO from a master device, optimizing resource usage and system performance.
Designed for ease of use, the ADRF670x family seamlessly connects to ADI’s latest transmit DAC, the AD9122, and GaAs amplifiers like the ADL5320. The ADL5320 is a high-linearity amplifier capable of driving power above 0 dBm into the final power amplifier stage. Together, these compact ICs form a complete active IC solution, ideal for next-generation multiple carrier frequency cellular wireless platforms.
phone Charging cable,Usb Phone Data Cable Android,iphone charge data cable,Phone data cable adapter
DongGuan BoFan Technology Co.,Ltd. , https://www.ufriendcc.com