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Top-Down Design of RF Receiver

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This example shows how to design an RF receiver for a ZigBee-like application using a top-down methodology. You will start from high-level requirements to derive system-level specifications before allocating a gain, nonlinearity, and noise budget to each component in the RF receiver using the RF Budget Analyzer app. This example verifies the bit error rate (BER) of an ideal reference design, before adding impairments and assessing their impact on the overall performance. This example also verifies the bit error rate (BER) of an impairment-free design, then analyzes BER performance after the addition of impairment models. The example uses the RF Budget Analyzer App to rank the elements contributing to the noise and nonlinearity budget.

Design Specifications

The RF receiver in this example uses these design specifications.

  • Data rate = 250 kbps

  • OQPSK modulation with half sine pulse shaping, as specified in IEEE® 802.15.4 standard for the physical layer of ZigBee®

  • Direct-sequence spread spectrum with chip rate = 2 Mchips/s

  • Sensitivity specification = – 100 dBm

  • BER specification = 1e-4

  • 10-bit analog-to-digital converter (ADC) a saturation power of 0 dBm

To create fully standard-compliant ZigBee waveforms, you can use Communications Toolbox™.

Design Workflow

The workflow to design the RF receiver using the top-down approach consists of these four steps.

Flow chart to represent the steps involved in designing an RF receiver using top-down approach.

Step 1: Develop Baseband Transmitter and Receiver

In this step, you will:

  • Model a ZigBee-like baseband transmitter for waveform generation

  • Model a ZigBee-like baseband receiver model for measuring the BER

  • Use a link-level idealized receiver model to determine SNR that helps you achieve the target BER of 1e-4.

For more information, see the Develop ZigBee-Like Baseband Transmitter and Receiver example.

Step 2: Determine the RF Receiver Specifications

In this step, you will:

  • Determine the noise figure (NF) and gain (G) of the RF receiver using the ADC specifications and SNR you determined in step 1.

  • Verify the BER and measure the corresponding chip error rate (ChER) to speed up the simulation.

For more information, see the Determine RF Receiver Specifications example.

Step 3: Refine the RF Receiver Model and Simulate RF Impairments

In this step, you will:

  • Refine the architecture of the of RF receiver and derive the specifications of its individual components based on the RF budget analysis.

  • Create a circuit envelope model of the RF receiver using direct-conversion architecture.

  • Use the circuit envelope model to simulate RF impairments such as phase noise, nonlinearity, impedance mismatch, and finite local oscillator (LO) isolation.

For more information, see the Refine RF Receiver Model and Simulate RF Impairments example.

Step 4: Simulate High-Power Out-of-Band Interfering Signal

In this step, you will:

  • Add a high-power out-of-band interfering signal and perform multicarrier simulation.

  • Determine the specifications of the DC offset cancellation algorithm.

For more information, see the Simulate High-Power Out-of-Band Interfering Signal example.

See Also

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