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InGaP-HBT Power Amplifiers
Published in Krzysztof Iniewski, Circuits at the Nanoscale, 2018
A typical block diagram of a CDMA PA and its peripheral circuits is illustrated in Figure 18.1. The PA amplifies the modulated signal from the Si-RF large-scale integration (LSI) up to a specific output power level, and then transmits it to the antenna port through the isolator, duplexer, and antenna switch. Figure 18.2 shows an example of the original spectra and their regrowth of CDMA-modulated signals, where Figure 18.2a shows the input signal (RFin) of the PA and Figure 18.2b shows the spectral regrowth at the PA output (RFout) caused by the distortion of the PA. Since this regrowth involves signal quality degradation and may give unwanted signal interference to adjacent channels, the regrowth levels (signal distortion levels) are strictly restricted by air-interface specifications of each system. These distortion levels are often characterized as adjacent channel power ratio (ACPR) or adjacent channel leakage power ratio (ACLR). As another current technology trend in addition to low distortion characteristics, there are strong requirements for smaller and thinner package size at a low cost. In the linear PA design, therefore, it is essential to realize low distortion characteristics with simple circuit topology suited for smaller size.
Power Amplifier Circuit
Published in Mike Golio, Commercial Wireless Circuits and Components Handbook, 2018
However, if a nonconstant envelope modulation scheme is used, then spectral regrowth, or Adjacent Channel Power (ACP) typically manifests. This distortion can degrade BER for wireless users allocated adjacent (or alternate) frequency bands. Hence most nonconstant envelope schemes have stringent specifications on Adjacent Channel Power Ratio (ACPR). ACPR is defined as the relative difference between the users in-band output power and the users adjacent (or alternate) band output power. For CDMA (IS95/98) a PA can typically operate no more than 1 dB into compression, which limits PAE to around 55% [13]. Methods exist to increase PAE, but these rely on some form of linearization scheme and have proven slow to develop for consumer wireless products.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Amplitude and phase distortion affect digitally modulated signals resulting in gain compression and phase deviation. The resulting signal, however, is far more complex than the simple one- or two-carrier results presented previously. Instead of IMD, adjacent channel power ratio (ACPR) is often specified for digitally modulated signals. ACPR is a measure of how much power leaks into adjacent channels of a radio due to the nonlinearities of the digitally modulated signal in a central channel. Measurement of ACPR is similar to measurement of IMD, but utilizes an appropriately modulated digital signal in place of a single tone signal generator.
Cost-Optimized Energy-efficient Power Amplifier for TD-LTE Outdoor Pico Base Station
Published in IETE Journal of Research, 2022
Brijesh Shah, Gaurav Dalwadi, Hardip Shah, Nikhil Kothari
In view of the advantages of the above-mentioned proposal, four identical amplifiers are used in two pairs of balanced configuration, as shown in Figure 2: (i) PA1 and PA2 (ii) PA3 and PA4. Balanced amplifiers nearly have the gain of each individual amplifier ignoring splitter/combiner losses [14]. Two successive splitters cause nearly 6 dB less power pumped into each PA IC. Thus overall PA can handle ideally 6 dB more input power than single PA. Similarly, one balanced pair increases OIP3 point by 3 dB [14] and two combined balanced pairs with successive two splitters increase overall OIP3 point by 6 dB. For technologies like LTE dealing with a large number of subcarriers, the relationship between Adjacent Channel Power Ratio (ACPR) and 3rd order intermodulation ratio (IMR2) is described in [17], where IMR2 is the ratio of power of two tone signal to the power at the 3rd order intermodulation signal. ACPR is the ratio of power leakage in the adjacent channel to the power transmitted in the desired band. ACPR specifications ensure that transmitter is not leaking the power in the adjacent band beyond a certain value as specified by 3GPP standard. If the PA is operating in the non-linear region, it can leak more power in the adjacent band and may not meet the ACPR requirements [5]. Therefore, ACPR simulation and measurement is essential to validate the PA linearity performance.