GC5330IZEV Datasheet, PDF (29/49 Pages) Texas Instruments – Wideband Transmit-Receive Digital Signal Processors

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GC5330
GC5337
SLWS226 B – DECEMBER 2010 – REVISED JANUARY 2011
Programmable Power Meters
Interval-Based Power Meter
There are three interval-based power meters which compute magnitude-squared sample values during
programmable time intervals and provide the following results:
• Integrated magnitude-squared power
• Peak power
• Number of magnitude-squared values above a first threshold
• Number of magnitude-squared values above a second threshold
An interrupt bit is set when new measurement results are available. For its input, each power meter can
independently select from the same set of internal node sources as the capture buffers.
Running-Average Power Meter for PA Protection
The running-average power meter monitors up to four signal streams on a single node, which is selectable from
the same set of internal sources as the capture buffers. For each signal stream, it measures running-average
power and counts instantaneous power values above a threshold (referred to as peaks). It can be used in
conjunction with hardware alarms for monitoring power levels for PA protection.
The running-average power meter has the following features:
• Running average mode, with programmable forgetting factor exponent, u (0 < u < 15)
AAA y(k+1) = (1 – 2^-u) × y(k) + 2^-u × |x(k)|²,
AAA where x(k) is the signal sample and y(k) is the power meter output.
AAA Typically, one must set u = 11 to get 0.5-dB accuracy, u = 14 to get 0.1-dB accuracy.
• Peak count mode: counts the number of power values, |x(k)|², above a threshold in a specified number of
samples (window). The number of power values, threshold, and window are all programmable.
• Flexible gating of the operation interval
Alarms
The output, y(k), from the running-average power meter can be compared on an ongoing basis to programmable
high and low thresholds (always positive). There are two alarms, alarm0 and alarm1. Each alarm is triggered (if it
is enabled) based on the programmed mode:
(0) Disabled
(1) Average power alarm. The alarm is triggered based on the following conditions:
If alarm polarity = 0 (see the alm_polarity register), y(k) > high_threshold
If alarm polarity = 1, y(k) < low_threshold
If alarm polarity = 2, y(k) > high_threshold or y(k) < low_threshold
(2) Peak power alarm. The alarm is triggered based on the following conditions:
If the count of power values |x(k)|² > peak_threshold exceeds the programmed number of
samples, peak_samples, in a programmed window, peak_window
(3) The alarm is triggered if either (1) or (2) occurs.
Alarm checks are computed on a per-antenna-stream basis. Each antenna stream y(k) result is compared to
per-stream programmable thresholds.
Once an alarm has been triggered, the output INTERRPT pin is asserted and the appropriate (alarm0 or alarm1)
alarm interrupt bit is set and, for alarm1, a programmable action takes place. The programmable action is the
same for all antenna streams, but the alarm triggering is independent for each antenna stream.
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