Abstract
The second-order distortion, often using second-order intercept point (IP2) as an indicator, has been considered easy to be filtered in narrowband radio frequency (RF) communications because it is located far away from the passband of transmitted signals. However, with rapidly increased applications in wideband RF communications, the second-order intermodulation (IM) might become important, partially evidenced by the increased appearances of IP2 in the amplifier datasheets in recent years. In this article, a power spectrum model of the second-order IM is derived to quantify the second-order distortion using the IP2. This model could be used to determine under what conditions, in terms of the relation between the carrier frequency and bandwidth, the second-order IM will affect the passband or the adjacent bands or other applications, using three types of frequency scenarios. These discussions are beneficial for RF engineers and spectrum planners to predict interferences from second-order IM. The experimental measurement at the end of the article validates the spectrum model.
Highlights
Radio frequency (RF) amplifiers are important components in wireless communication systems
Neglecting the even-order terms is usually applied to narrowband RF communications, which are defined as the bandwidth is far less than the centre frequency
Recent studies suggested that the second-order intermodulation (IM) distortion may be significant in wideband transceivers widely used in long-term evolution advanced (LTE-A) and fifth-generation new radio (5G NR) systems [2,3,4,5,6,7]
Summary
Radio frequency (RF) amplifiers are important components in wireless communication systems. Recent studies suggested that the second-order intermodulation (IM) distortion may be significant in wideband transceivers widely used in long-term evolution advanced (LTE-A) and fifth-generation new radio (5G NR) systems [2,3,4,5,6,7]. A power spectrum model of the second-order IM products based on IP2 and other parameters, such as gain, carrier frequency, and bandwidth, is derived. This model is used to analyse under what conditions the second-order IM will affect the passband and adjacent bands through the wideband power amplifier operation using three types of frequency scenarios. The power spectrum model can help RF engineers, spectrum planners and regulators to predict and forecast the potential second-order interferences, for 5G NR, LTE-A, and other wideband applications
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