To meet the growing demands of transistor users, the power density of active devices continues to rise. Commercial wireless communications, avionics, broadcasting, industrial, and medical systems are pushing for smaller output stage devices that can deliver higher power. Freescale Semiconductor has consistently provided high-performance RF and microwave transistors tailored for these applications, offering competitive advantages in features, packaging, and application engineering.
Freescale has a strong presence in the production and sale of discrete and integrated RF semiconductor devices. Its seventh-generation silicon RF out-of-band diffusion metal oxide semiconductor (LDMOS) with HV7 technology delivers excellent output power and linearity for WiMAX infrastructure at 3.8 GHz. The company’s high-voltage HV7 process is also suitable for industrial, scientific, and medical (ISM) applications, supporting 48V operation. In addition, Freescale has extended the operating frequency of its high-power GaAs PHEMT devices up to 6GHz for use in WiMAX amplifiers.
Recently, Freescale introduced the first two-stage RF integrated circuit (RF IC) capable of delivering 100W output power. When paired with its cost-effective MMG3005N general-purpose amplifier (GPA), the MWE6IC9100N and MW7IC18100N RF ICs provide a complete solution for 100W power amplifiers used in wireless base stations operating at 900 MHz and 1,800 MHz.
While the performance of these RF power devices is impressive, Freescale ensures that customers receive full support throughout the testing, modeling, packaging, and application phases. Every delivery comes with technical assistance from experienced engineers, ensuring smooth integration into customer systems.
**RF Power Characteristics**
Load pull measurement techniques have gained popularity in recent years, especially for characterizing RF power amplifiers under various load conditions. These methods are widely used to measure parameters such as peak output power, gain, and efficiency. Additionally, complex modulation signals are increasingly being used in the same test environments. For high-power RF manufacturers, accurately characterizing their products remains a challenge, and developing such devices often requires large-scale peripherals.
Freescale’s RF department has developed advanced measurement techniques and automated custom solutions to improve accuracy. The company's high-reflection (high gamma) load-pull lab covers frequencies from 250MHz to 8GHz and supports up to 100W continuous power (or 500W pulse power). This facility serves modeling, applications, and other functional groups. Freescale has also created specialized test equipment to optimize impedance conversion ratios, allowing accurate measurements on low-impedance devices.
In addition to traditional fixture-based systems, Freescale uses on-wafer load-pull systems based on commercial wafer probe equipment, primarily for device research, development, and modeling. These systems feature a unique three-dimensional anti-vibration mechanism to reduce tuning vibrations and minimize damage to probes and wafers.
Freescale’s load-pull system offers high accuracy, with a maximum gamma value of 0.93 to 0.95 and sensor differential gain ΔGt less than 0.25dB. Measurements are accurate to within 0.1dB across the tested region. This level of precision is achieved using high-precision 7mm coaxial connectors with a VSWR of typically 1.008:1 at 2 GHz. Additional features include center contact impedance below 0.1mΩ, good correction characteristics, cell-to-cell impedance variation of less than 0.1%, and phase transitions of less than 0.21 degrees at 18GHz.
A combination of vector network analyzers, load-pull systems, and TRL correction methods allows source matching better than 45 dB. Unlike traditional SOLT correction, TRL is not affected by parasitic components at high frequencies, making it more reliable for precise measurements.
Typically, 5,000 to 6,000 impedance points are tested per tuner to ensure even distribution across the source and load planes. For devices with very low termination impedance, high-density testing is essential due to their sensitivity to small impedance changes. However, when evaluating devices with high package matching impedance, sparse load pull testing may suffice.
A typical load-pull setup is shown in Figure 2. Freescale uses its load-pull systems to evaluate parameters like peak pulse compression, AM-AM and AM-PM conversion, frequency response, and input impedance. The system also supports composite signal measurements, including average and peak power, adjacent channel power (ACP), dual-tone and polyphonic intermodulation distortion (IMD), and behavior under different load conditions of the EDGE signal.
Freescale performs CCDF analysis on device signals, a common measurement in 2G and 3G wireless systems. The need for CW, pulse, and modulated signal measurements arises from the different thermal loads these signals impose on the device, requiring optimized load impedance for each modulation format. Beyond its extensive measurement capabilities, Freescale has developed powerful data entry and post-processing tools, enabling users to analyze device behavior in 2D or 3D (Figure 4).
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