GC5316 datasheet(43/75 Pages) TI

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GC5316

SLWS154A − JANUARY 2004 − REVISED MARCH 2004

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3.2.1.1

Transmit Composite RMS Power Meter

Integrate

58 bits

C lear

Transfer

Sync

RM S Power

Interrupt

From

Sum chain

Integration Period C ounter

21 Bits

Sync Delay

Counter

9Bits

(in 8 sample

increments)

I nterval

Counter

21 Bits

(in samples)

pmeterX_sync_delay

pmeerX_interval

pmeterX_integration

Sync

Event

Sync Delay

Integration

Start

Integration Time

Integration

Start

Integration Time

Interval Time

Integration

Start

Interval Time

Interrupt

Time

Power Measurement Time Line

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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