A transmitter IC for TETRA systems based on a Cartesian feedback loop linearization technique

Digitally Assisted RF Architectures: Two Illustrative Designs

“…PA memory effects, which cause great complications in predistorters and adaptive predistorters, are handled by Cartesian feedback with no fundamental change in implementation. Perhaps because of this fundamental advantage, fully integrated realizations of the Cartesian feedback concept have populated the recent literature [1][2][3]. A typical Cartesian feedback system is shown in Fig.…”

“…Such small errors cause no serious problems in experiments. 3 The reader may well ask how we can talk about linearized dynamics when the whole point of Cartesian feedback is to deal with an explicitly nonlinear RF path. It turns out that taking this approach, working out the stability analysis as if we were dealing with a linear system, and then modifying that structure to account for nonlinearities leads to the most conceptually transparent development.…”

A designer’s approach to device mismatch: Theory, modeling, simulation techniques, scripting, applications and examples

“…Furthermore separation should have a minimal effect in good analog design, were devices are placed in close proximity. Some exceptions could be identified in reference structures [10,26] and I/Q mismatch in RF-architectures [28,42]. Since those cases are limited in a design and because layout information is needed (device distance), the author proposes a manual approach to mismatch increase due to distance.…”

“…Mismatch [5,13,25,34,43] is an essential aspect in the design of analog [2,12] and RF integrated systems [28,20]. Analog to Digital (and Digital to Analog) Converters [6,8,13,26,35], receiver architectures [24,41], mixer harmonic rejection [14], and even magnetic storage [36], or digital RAM cells [17], are some examples of circuity, were simulating mismatch is an important part of the design process.…”

Green Communications: Digital Predistortion for Wideband RF Power Amplifiers

“…For high-power, wideband applications such as UMTS and LTE, those PAs do still suffer from nonlinear distortion, so we still need some kind of linearization. In the second trick, for a given PA operating near saturation, the linearity can be improved by signal processing techniques, PA linearization [11], using techniques such as a) feedback distortion compensation [12], [13], [14], [15], [16], using closed-loop regulators to reduce the nonlinear distortion, b) feedforward distortion compensation [17], [18], [19], [20], [21], which utilizes an additional error amplifier in the forward loop to compensate for the nonlinear distortion introduced by the main PA, and c) predistortion linearization [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], which uses a stand-alone module to pre-distort the input signal to the PA, improving the linearity at PA output. Due to its high flexibility and excellent linearization performance, digital predistortion (DPD) has become one of the most preferred choice for linearizing RF PAs, and tends to be an fundamental component in current and next-generation wireless communication systems.…”