Patent number 8648655 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "There is a high interest in wireless communication to develop highly linear and efficient power amplifier suitable for third generation (3G) and upcoming fourth generation (4G) of communication standards. These new standards have potential for offering more and better data services. However, in order to establish this within a restricted frequency band, it is needed to use signals with high peak-to-average power ratios (e.g., wideband code vision multiple access (WCDMA) .about.10 dB), requiring high linearity of the transmitting amplifier. Hence, in general, power amplifiers are designed to be subjected to the peak-power condition, but are operated most of the time at sufficiently lower power levels (power peak-off). As a result, the power amplifier operating with these signals may function such that the peak efficiency is high, but the average amplifier efficiency is rather low.
"For this reason, there is a renewed interest in high efficiency power amplifiers, for example the
"Therefore, proper compensator structures, such as the composite high power amplifier (C-HPA) have been introduced to increase the efficiency and output power. Such C-HPA comprises from several individual high power amplifier (HPA). Most common configuration is C-HPA with two HPAs which also known as a linear amplification using nonlinear components (LINC).
"The LINC technique was first proposed in 1974 as a method of achieving linear amplification at microwave frequencies. The basic scheme of LINC for amplifier has two RF HPAs that are assumed to be high-efficiency and highly nonlinear. The RF source signal x(t) is split into two constant envelope, phase modulated signals, x1(t), x2(t) by signal component separator (SCS) that has a function of the signal separation or generation process, and each is fed into its own nonlinear RF power amplifier. The HPAs separately increase the power of each signal to generate output signals
"In many issues it is assumed that the bandwidth at the digital-to-analog convertor (DAC) output is unlimited. However for many cases such assumption is not applicable. The real oversampling DAC operating with high clock frequencies may be assumed as such the ideal converter.
"Despite the original signal x(t) has a narrow spectrum, the signal component separating (SCS) operation causes a significant spectrum expansion for signals x1(t) and x2(t) in the C-HPA arms. In the conventional technique disclosed in, for example, patent document 1 and non-patent documents 1-4 cited below, it is assumed the ideal arms with unlimited bandwidth (i.e. ultra-wideband ideal DACs) that may pass wideband signals x1(t) and x2(t) without any distortions to inputs to the HPAs (hereinafter, sometimes to be referred to as HPA1 and HPA2). The most critical element in the arm may be DAC because its bandwidth is limited by operating clock. Typically this is 100-150 MHz for low/mid-ends commercial available Large Scale Integrations (LSIs). In contrast, DACs for the broadband applications such as Worldwide interoperability for Microwave Access (WiMAX), Long Term Evaluation (LTE), Wideband Code Division Multiple Access (W-CDMA) and the like, in order to avoid distortions in signals x1(t) and x2(t), must provide very high bandwidth (must operate with high clock frequencies in order several hundred MHz) and at the same time provide a high level of bit resolution (quantization), for example, 800 MHz clock and 14 bit resolution. The cost for such a hi-speed and hi-resolution hi-end DACs is high.
"The frequency restrictions caused by component of a high frequency circuit such as LPFs at the DACs inputs (or DAC outputs) result in the parasitic AM at the HPA1 and HPA2 inputs for signals x1(t) and x2(t). The LPFs cut some high frequency part of signals x1(t) and x2(t). The high frequency part that cut by LPF causes the unwanted parasitic AM modulation in signals at the LPF output. Such parasitic AM results in growth of out-of-band spectrum components after combining signals
"However for many commercial available (low-mid cost LSI) DACs, such the assumption is not applicable. Normally, the DACs have low-pass filter (LPF) at its output. Such the LPFs introduce some parasitic amplitude modulation (AM) into the DAC output signal. With such the parasitic AM and non-linear HPA, the complete signal reconstruction may not be possible. Thus the out-of-band spectrum components are arising in the HPA output signal spectrum.
"One of the aims of the present invention is to provide a modulator that removes parasitic amplitude modulation automatically, thereby reconstructing a signal inputted into the modulator at an output terminal of the LINC modulator.
"Another of the aims of the present invention is to provide am amplifier having a modulator that removes parasitic amplitude modulation automatically, thereby reconstructing a signal inputted into the modulator at an output terminal of the LINC modulator."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "A linear amplification with nonlinear components (LINC) modulator is provided. The LINC modulator includes: a separator that generates a plurality of constant envelope signals (x1(t), x2(t)) from a source signal (x(t)); a processor that receives an input signal (x1(t), x2(t)) and detects and removes a phase jump in phase trajectory of the input signal (x1(t), x2(t)) to generate a first signal having a continuous phase trajectory and a second signal having a discontinuous phase trajectory; and a quadrature modulator that mixes the first signal with the second signal to reconstruct the input signal (x1(t), x2(t)).
"The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
"It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restricted of the invention, as claimed."
URL and more information on this patent, see: Lozhkin,
Keywords for this news article include: Electronics,
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