MATLAB: How to use AD9361 TX RF block set in Simulink

simulink ad9361 tx

I am using AD9361 RF blockset to simulate my FHSS code in matlab.I am unable to modulate my signal to Radio wave frequency(in GHz) using the AD9361 TX block.

The input signal is not being mixed with Local Oscillator frequency and when i check the output of TX using spectrum analyser its showing the same base band signal given in the input.

I have tried changing the filter settings of the AD9361 Tx still there is no improvement in the output.

I need help and advice to understand and solve the problem.

Best Answer

The “External LO” block is use to add noise on the LO signal of 2GHz specified in the “ad9361_tx” block mask, while the “Ideal Source” complex sine signal of 2MHz (look under the mask) is the modified input to the modular found in the subsystem “ad9361_tx/ad9361_tx/RF_TX”. The noise skirt is specified in the “External LO” block, while the bandwidth of the signal is related to the “Step size”, Tstep, found in the “ad9361_tx/ad9361_tx/RF_TX/Configuration” block. The Configuration block is also use to specify the simulation frequencies.

The “ad9361_tx/ad9361_tx/RF_TX” has three Inport blocks. The blocks “Inport_I”(real part of complex baseband) and “Inport_Q”(imaginary part of complex baseband) specify that the complex sine signal resides on a DC carrier (Carrier frequency = 0). If the carrier frequency is not DC, then the complex baseband signal is handled as I+jQ. The “ad9361_tx/ad9361_tx/RF_TX/LO Signal” block specifies the LOFreq and the “ad9361_tx/ad9361_tx/RF_TX/Outport” block specifies that the desired output carrier frequency is ‘RF’. The output carrier frequency of interest should be DC+LO=LO=RF=2GHz. The original baseband signal, after system processing, will reside on this RF signal. However, a baseband signal is I=jQ where the carrier is implied but not shown.

You can follow the documentation which is provided in Add-on Manager.

Related Solutions

MATLAB: Changing the LO frequency of ad9361_RX block in ad9361_QPSK testbench model causes unexpected behavior

If you change both the LO and the RF center frequency in the ad9361_RX block, you will notice very minor differences. The RF center frequency of the RX should the same as the TX LO center frequency. The input signal to the RX is a complex equivalent baseband signal, and the RF center frequency of the RX defines the RF center frequency of the incoming signal.

The LO RX center frequency should be close (within the simulation bandwidth) to the RF center frequency. This is described in the support package documentation. To access this, please type the following command at the Command Window -

open(ad93xx_getdoc)

If you set the TX LO frequency at 2 GHz, the RX RF frequency at 2GHz, and the LO center frequency at 1GHz, results will be incorrect.

MATLAB: Which mixer (Circuit Envelop/ Idealized baseband/ Equivalent Baseband from SimRF blocksets) is best suited for single carrier frequency input with imperfections such as noise/clipping in SimRF 3.2 (R2012a)

Idealized baseband mixer has built-in frequency-dependent phase noise. It might be simpler to use for a single-frequency system with a known phase noise model.

Equivalent Baseband mixer is more general, because it allows the arbitrary oscillator signal (see, for example, the phase noise block in the 'simrf_low_if' demo). The "phase noise" block is used as a noisy oscillator to the two mixers in Hartley Receiver.

With respect to circuit envelope mixer, the closest demo which will explain more is 'simrf_friis'. There you can see the simple chain, where the signal is downconverted by a mixer and a noiseless oscillator.

Idealized baseband mixer would be more suited with respect to single frequency system.

Best Answer

Related Solutions

MATLAB: Changing the LO frequency of ad9361_RX block in ad9361_QPSK testbench model causes unexpected behavior

MATLAB: Which mixer (Circuit Envelop/ Idealized baseband/ Equivalent Baseband from SimRF blocksets) is best suited for single carrier frequency input with imperfections such as noise/clipping in SimRF 3.2 (R2012a)

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