wiki:WARPLab6/Specifications

WARPLab 6 Specifications

Tx/Rx I/Q Buffers

  • Independent Tx/Rx I/Q Buffers.
  • Each buffer can store a maximum of 214 samples.
  • Buffers persist between triggers.
  • Samples are read from Tx I/Q Buffers to I/Q DACs at 40 MHz.
  • Samples are written from I/Q ADCs to Rx I/Q buffers at 40MHz.

Tx Signal Requirements

  • Amplitude of real part (In-Phase signal: I) in [-1,1] and amplitude of imaginary part (Quadrature signal: Q) in [-1,1]. I/Q signals on transmitter path are represented in the FPGA using Fixed Point 16_15.
  • Lowest Frequency: 30 kHz. Radios filter DC.
  • Highest Frequency: Depends on the Tx/Rx Low Pas Filter (LPF) Corner Frequency Setting. By default, Tx and Rx LPF are set to nominal mode. Possible Tx/Rx LPF settings are the following.
    Tx LPF corner frequency: Mode 0: Undefined, Mode 1: 12 MHz (Nominal Mode), Mode 2: 18 MHz (Turbo Mode 1), Mode 3: 24 MHz (Turbo Mode 2).
    Rx LPF corner frequency: Mode 0: 7.5 MHz, Mode 1: 9.5 MHz (Nominal Mode), Mode 2: 14 MHz (Turbo Mode 1), Mode 3: 18 MHz (Turbo Mode 2).
  • 40 MHz sampling frequency.

I/Q ADC/DAC

  • Are always clocked at 40 MHz.
  • DAC I/Q input signals are represented using Fixed Point 16_15.
  • ADC I/Q output signals are represented using Fixed Point 14_13.

Tx/Rx Amplifiers

  • The Tx path applies gain at three amplifiers: Tx Base Band (Tx BB), Tx RF, and Tx RF PA. The Tx RF PA is always fixed at 30 dB gain. The Tx BB and Tx RF amplifiers are adjusted digitally, the range of gains is the following.
    Tx BB: In [0, 3] applies 1.5 dB/step.
    Tx RF: In [0, 63] applies 0.5 dB/step.
  • The Rx path applies gain at two amplifiers: Rx Base Band (Rx BB) and Rx RF. Rx amplifiers are adjusted digitally, the range of gains is the following.
    Rx BB: In [0, 31] applies 2 dB/step.
    Rx RF: In [1, 3] applies 15 dB/step.
  • A signal with I/Q that span full [-1,1] range of I/Q DAC input (e.g a complex exponential exp(j*2*pi*f*t) with f in passband of Tx/Rx LPFs) will be transmitted at RF with a peak power of approximately 19 dBm when Tx gains are set at maximum values (Tx BB = 3 and Tx RF =63 ), the average power will depend on the waveform.

Received Signal Strength Indicator (RSSI)

  • RSSI reading is a 10-bit number linear in dB that can be converted to received power in dBm.
  • The RSSI is measured after the Rx RF amplifier, so the digital RSSI to Rx Power conversion depends on the Rx RF gain setting. The numbers below are approximate, based on plots from the MAX2829 datasheet. For a more precise mapping, you would need to take measurements using a transmitter with known output power (like an RF signal generator).
    For high gain (Rx RF = 3), RSSI=0 is -100dBm; RSSI=1023 is -30dBm.
    For medium gain (Rx RF = 2), RSSI=0 is -85dBm; RSSI=1023 is -15dBm.
    For low gain (Rx RF = 1), RSSI=0 is -70dBm; RSSI=1023 is 0dBm.
  • MAX2829 specifies the RSSI bandwidth is 3MHz but we have observed that RSSI bandwidth spans nearly the full bandwidth of the RF path (RF path bandwidth is determined by Tx/RF LPFs corner frequency settings). Users are recommended to test RSSI bandwidth directly in their setup to see its characteristics directly; try transmitting a chirp (sweeping sinusoid) and plotting the RSSI vs. time. See WARPLab example 'warplab_siso_example_TxRx_BandwidthChange.m'.
  • The RSSI signal is sampled by its own ADC (independent of I/Q ADCs). In WARPLab, the RSSI ADC is clocked at 10 MHz (1/4 of the rate of the I/Q ADCs).
Last modified 7 years ago Last modified on May 6, 2013, 4:19:52 PM