Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicable.

Modern electronic systems operate in increasingly complex spectral environments, competing for available bandwidth. Many potential interference issues can occur between radar and wireless communications systems.1 For example, United States Navy ships must deal with a myriad of electronic systems, including radar and communications systems which can interfere with each other.2 The Navy is also investigating ship-based Long-Term-Evolution (LTE) wireless technology for close-quarters communications, adding even more complexity to these spectral environments.3 Investigating potential interference issues between complex wireless signals such as LTE and radar may be useful to ensure successful deployment.

A flexible means of evaluating systems in a research and development (R&D) laboratory should enable checking for co-existence issues before they are deployed. Such flexibility should support simulation of a wide range of different emitter signals and the capability to evaluate performance under different interference scenarios. Assessing the potential impact of radar interference on a wireless signal may involve evaluating key wireless performance metrics, such as error-vector-magnitude (EVM) and bit-error-rate (BER) performance or data throughput under a number of different interference scenarios.

A flexible R&D test solution can be created by combining design simulation with a precision arbitrary waveform generator (AWG) to create different interference scenarios. Several case studies are examined to show the flexibility of this approach. The first case study shows the test solution being used to create a multiemitter spectral environment consisting of an LTE emitter in the S frequency band; two S-band radar emitters; GSM, EDGE, and WCDMA emitters; and a WLAN emitter. Test equipment is used to evaluate the coexistence of an LTE and S-band radar emitter by evaluating LTE EVM performance in the presence of an interfering S-band radar emitter. The second case study evaluates simulated coded BER performance of an LTE downlink signal as an S-band radar interferer’s center frequency is swept.

The first case study focuses on an LTE downlink signal at S-band frequencies and an S-band radar signal, which are two of the emitters in a complex multi-emitter spectral environment, and how they can coexist within the same operating environment. The complex multi-emitter spectral environment is created using system-level design simulation which enables multiple wireless, wireless networking, and radar signals to be simulated and combined using commercial-off-the-shelf (COTS) simulation libraries. The multi-emitter signal (including the LTE downlink signal and S-band radar signal) is simulated with the schematic shown in Fig. 1. The S-band radar simulation signal source is shown at the top left, followed by the LTE downlink, EDGE, GSM, and WCDMA signal source. An additional S-band radar signal source and WCDMA signal source are also shown. A WLAN recording, which was captured using the Agilent 89600 VSA software, is read into the simulation environment as a simulation signal source.

Check For Co-Existence Between LTE And Radar, Fig. 1

Simulated signals with different center frequencies and bandwidths were resampled and combined together using a signal combiner element to create an output waveform which could then be downloaded to the precision AWG using a simulation sink element. Figure 2 shows the multi-emitter hardware test-equipment setup to evaluate LTE and radar coexistence, which includes a precision AXIe-based AWG (left), and an RF signal analyzer (right). The system-level simulator has been installed on the AXIe embedded controller (below the AWG) to create the multi-emitter test signals with the AWG.

Check For Co-Existence Between LTE And Radar, Fig. 2

Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicable.