GC5316 Datasheet, PDF (43/75 Pages) Texas Instruments – HIGH-DENSITY DIGITAL DOWNCONVERTER AND UPCONVERTER

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3.2.1.1 Transmit Composite RMS Power Meter
GC5316
SLWS154A − JANUARY 2004 − REVISED MARCH 2004
18
36
I
F rom
Sum chain
18
Q
37 _Integrate
58 bits
36
C lear
pme e rX _ inte rva l
pme t e rX _ sy nc_ de la y
9
21
Re gis te r
32
RM S Power
T ransfer
pme te rX _ inte gra tion
21
Sync
Sync Delay
Counter
9 Bits
(in 8 sample
increme nts)
I nterval
Counter
21 Bits
(in samples)
Integration Period C ounter
21 Bits
Int e rrupt
Power Measurement Time Line
Sync Delay
Integration Time
Interrupt
Integration Time
Interrupt
Integration Time
Interval Time
Interval Time
I nte rrupt
Time
Sync
E vent
Integration
Start
Integration
Sta rt
Integration
Sta rt
Figure 37. Transmit RMS Power Meter
The GC5316 provides four independent transmit output ports, each of which is the sum of a number of individual
transmit carriers (a sum chain). Four composite RMS power meters measures the RMS power of the combined
carriers in each of the four sum chains. These power meters are similar to those used to measure the RMS power
of each individual channel, but have different counter lengths.
The input to the power meter is the scaled and rounded output of a sum chain. Power is calculated by squaring each
18-bit I and Q sample, summing, and then integrating the summed-squared results into a 58-bit accumulator. The
integration time is pmeter_integration (21 bits) output sample periods.
There is a programmable 21-bit interval counter which sets the interval over which power measurements are
repeated. The interval time = pmeter_interval+1. The interval time must be greater than (not equal to) the integration
time. A measurement integration period is started at the beginning of each interval time.
The process begins with a sync event starting the 9-bit delay counter. After the delay count + 2 samples, the
integration interval is started. The power is calculated for each I and Q sample and added to the 58-bit accumulator.
The integration continues until the integration count is met at which point the upper 32 bits of the 58-bit integrator
are transferred to the read register and an interrupt is generated. A new measurement period starts at the end of the
interval period.
NOTE:Each of the four composite RMS power meter blocks has its own delay sync, interval, and integration period
counters, as well as separate sync source registers.
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