RF multipath channel simulator Basics

This page covers RF multipath channel simulator basics with block diagram.It mentions RF multipath channel simulator application note.

Simulator: It is the software or hardware or both which implements real time scenario to help in product testing without putting the product in real environment. This will help product go through successful operational performance once put in the actual conditions for which it has been designed or developed.

channel simulator: The simulator which incorporates effect of real time channel is known as channel simulator. It introduces delay, attenuation, fading, noise, doppler shift etc. to the signal of the device under test.

Multipath channel simulator: It introduces effect of multiple paths to the signal. Number of paths need to be software or hardware configured based on test scenario as per application. This is because, as we know the transmitted signal passes through different paths and will incur reflection from multiple objects (buildings, towers, etc.) during travel till it reaches receiver end. Hence we find multiple copies of transmitted signal at receiver, each having different attenuation and delay. This real time effect is simulated in multipath channel simulator.

multipath channel simultor

Figure-1 depicts implementation side of the RF/IF multipath channel simulator. As shown it operates at IF frequency. In order to use the multipath channel simulator at RF frequencies, Optional RF down converter and RF Up converter modules are needed. In this case, RF signal of the DUT(Device Under Test) is fed to RF Down converter and downconverted IF signal is lated fed to channel simulator input. The IF output from channel simulator is converted back to RF using RF upconversion and fed back to DUT.

Filter: This band pass filter is used to limit the frequency as input. This designed based on bandwidth of interest and rejection needed in stop band of frequencies.

ADC: It converts signal in analog form to digital form for digital signal processing.

DSP: This will house advanced signal processing software to emulate effect of real time channel including multi path scenario. The software is programmable as per various user defined input parameters through front panel or remote terminal.

DAC: It converts the channel impaired digial signal back to analog form in order to interface with analog filter.

Filter: It is a band pass filter which removes all the unwanted frequencies that might have been introduced in the signal due to ADC/DAC processing as well as DSP processing. It passes proper IF band pass signal for test purpose.

For testing which requires additional signal such as interference testing, optionally one more signal generator is required and signals are combined using RF power combiner before feeding to the multipath channel simulator. This will help in multi-channel testing.

RF multipath channel simulator application note

Real Time Logic, Inc. has launched Multipath Channel Simulator model T400CS. It is useful for modem testing as well as transmitter/receiver testing. This channel simulator has following features:

• Operates on various frequency bands such as UHF band, L band, S band, C band, X band and Ku band etc.
• Simulates different types of satellite e.g. LEO, MEO, GEO etc.
• Suitable for testing OFDM as well as continuous wave signal.
• Simulate upto 8 signals with individual impairments and configuration. The parameters which are configured include modulation type, frequency offset, data rate, PRN code, amplitude, filtering etc.
• Built-in spectrum signal analyzer which also provides BER, C/No and Eb/No display. It can analyze both time domain and frequency domain waveforms.
• Supports different versions to support different bandwidth options (40MHz, 85 MHz, 250 MHz) etc.

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