Forced stray RF transceiver implemented decorrelation

In large digital beamforming antenna, it is highly desirable to improve the dynamic range by combining signals from the beamformer process distributed waveform generator and a receiver. If the error term associated uncorrelated, it is possible to enhance the dynamic range in 10logN noise and spurious performance. Where N is the number of waveform generator or the receiver channels. Noise is essentially a very random process, making it ideal for tracking correlated and uncorrelated noise sources. However, the presence of spurious signals more difficult to enforce stray related. Thus, any method may be designed to force the spurious signals related to the phased array system architecture is valuable.
　　In this article, we will review the previously published techniques, by techniques related to the LO frequency offset and digitally compensate for this offset, the forced spurious signals. Then, we'll show ADI's new transceiver products, ADRV9009, explain how its integrated features to achieve this function. Then, we have to end the full text of the measured data to prove that the effect of this technology.
　　Related methods known to stray
　　in the phased array, various methods related to the advent of the stray force has been for some time. A first known literature dating back to 2002, which describes a general method for ensuring that the receiver spurious uncorrelated. In this process, first in a known manner ,, the modified signal from the receiver to the receiver. Then, the receiver of the nonlinear components distort the signal. Modify the output of the receiver, just introduced in the receiver reversed. Target signal becomes coherent or related to, but does not restore the distortion terms. Modified test method is implemented in each of the local oscillator (LO) frequency synthesizer set to a different frequency, and digitally tuning numerically controlled oscillator (the NCO), to modify the digital correction processing.
　　It shows a functional block diagram of the ADI's transceiver ADRV9009.
　　RF transceiver - MAX490MJA achieve mandatory stray decorrelation
　　ADRV9009 functional block diagram. Each waveform generator or receiver are implemented with the direct conversion architecture. Daniel Rabinkin article "Nonlinear distortion and the front end of the array waveform synthesis" discusses various direct conversion architectures detail. 4 LO frequency may be programmed independently to each IC. Digital processing portion comprises a digital up / down-conversion, an NCO IC may be independently programmed span. Peter Delos article "Broadband RF receiver architecture options" for digital downconversion was further description.
　　Next, we show a method that can be used to force the plurality of transceivers on a stray decorrelated. First, the offset frequency of the LO by the onboard programming phase locked loop (PLL). Then, set the frequency of the NCO, the LO frequency is applied to the digital compensation of offset. By adjusting the two features within transceiver IC, the digital data out of the transceiver need not be shifted in frequency, and parasitic entire frequency conversion capabilities are built in to the associated transceiver IC.
　　It shows a functional block diagram of the waveform generator array representative. The method of the waveform generator will be described in detail, the data show waveform generator, but the method is equally applicable to any receiver array.
　　Forced stray RF transceiver implemented decorrelation
　 LO frequency and NCO programmed waveform generator array, stray force decorrelation. To illustrate the concepts from the perspective of frequency, Figure 3 shows an example of a transmission with two signals from the direct conversion architecture. In these examples, the RF LO at the high end. In the direct conversion architecture, the image frequency and the third harmonic of the LO appears on the opposite side, below the LO frequency and displayed. When the LO frequency is set to different channels of the same frequency, at the same frequency of the spurious frequency, shown in Figure 3a. Figure 3b is a case of providing a higher frequency of LO1 LO2. Digital NCO equally offset, to achieve coherent gain of the RF signal. Mirror and third harmonic distortion products at a different frequency, and therefore irrelevant. Figure 3c shows the same arrangement to Figure 3b, just add an RF carrier modulation.