User's Manual

SIGMA DESIGNS Windeo Reference Design Module User Guide
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2.2. Receive section:
2.2.1. RF receiver
The B7CW101 contains 3 receive channels. Each of the receiver channels provides both I
and Q outputs and contains an LNA (Low Noise Amplifier), down-converters, I and Q
base-band filters, variable gain amplifiers (VGA’s) and a final fixed gain block. All inputs
and outputs are differential. Each side of the differential RF input is nominally 50 Ohms.
So, the RF inputs are driven from an antenna through a 1:2 differential balun. Each side of
the RX outputs is a source follower with typically a 1.5mA source current.
Each receive channel has typically,
• 3.1GHz to 4.8GHz receive bandwidth
• Sensitivity of -80dBm
• Output capability of 560mV peak to peak for driving an ADC
• Independently controlled VGA gains
Each receiver LNA incorporates a band-pass filter which covers the lower 3 bands of the
UWB spectrum. The RF signal is down converted to a base-band frequency through mixers
driven by a VCO. The VCO frequency is selected through the band selection input pins
BAND[3:1] on the B7CW101. The base-band signal is then filtered and amplified through
the VGA blocks.
Each VGA provides a variable gain range of 31dB in 1dB steps. The 2 VGA’s within each
receiver channel (I and Q) always have the same gain, although the gain can be different
between channels. Each VGA is followed by a fixed gain block to provide a
low voltage, differential analog, output signal to an ADC on the B7CW201 Baseband processor.
2.2.2 Baseband Receiver
2.2.2.1 PHY Receiver
The Windeo PHY receiver of the Baseband chip features the 3-channel Intelligent Array Radio (IAR)
PHY receiver. The front ends and the back end together include all of the signal processing and
decoding blocks required for reliable reception of user data. The signal processing and decoding
functions implemented in the Windeo PHY receiver include the following:
•Packet detection and synchronization
•Automatic gain control
•Overlap-and-add
•Fast Fourier transform for OFDM demodulation
•Channel equalization
•Carrier frequency offset correction
•Sampling frequency offset correction
•Despreading, demapping, deinterleaving
•Viterbi decoding