GC5318 datasheet(11/45 Pages) TI

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GC5318

HIGH-DENSITY DIGITAL UPCONVERTER

SLWS187 – JULY 2006

Each transmit channel includes an RMS power meter used to measure the RMS power within the channel.

The RMS power meter samples the I and Q data stream before the PFIR filter; see Figure 2-7. Both 18-bit

and

data

are

squared,

summed,

and

then

integrated

over

time

determined

pmeter_integration_duc (13 bits). The integration time = 4 x pmeter_integration_duc + 1 (in units of a

sample period or generally a chip period).

A programmable 9-bit interval counter sets the interval over which power measurements are repeated.

The timer counts in increments of 64 samples. The interval time = 64 (pmeter_interval_duc+1). The

interval time must be greater than (not equal to) the integration time.

The power measurement process starts with a sync event (ssel_pmeter). The integration starts at sync

event + 3 chips + sync_delay. The 7-bit delay register permits delays from three to 130 samples after

sync. The integration continues until the integration count is met. At that point, the top 32 bits of the 50-bit

accumulator are transferred to the read register and an interrupt is generated that indicates the power

value is ready to read. The interval counter continues until the programmed interval count is reached.

When reached, the integration counter and the interval counter start over again. Each time the integration

count is reached the upper 32 bits are again transferred to the read register, overwriting the previous

value and sending an interrupt signifying the power value can be read. Failure to read the data before the

next interrupt signal results in overwriting the previous interval measurement.

Sync ssel_pmeter starts the process. Whenever a sync is received, all counters are reset to zero no

matter what the status may be.

For UMTS, I and Q are calculated and the integrated power is read. In CDMA mode the power is

calculated for both the A and B signals, producing two 32-bit results.

For CDMA mode, the integration time is slightly longer. The power read in CDMA mode with a dc input is:

• A power: [ I2 × (X × 4 + 1) + Q2 × (X × 4 + 0) ] × 2-18. Note: One Q sample is missing from the

integration.

• B power: [ I2 × (X × 4 + 1) + Q2 × (X × 4 + 1) ] × 2-18

where X is the integration count.

Table 2-5. Programming

VARIABLE

DESCRIPTION

pmeter_result_a_lsb(15:0)

Lower 16 bits of the A channel power measurement.

pmeter_result_a_msb (31:16)

Upper 16 bits of the A channel power measurement.

pmeter_result_b_lsb (15:0)

Lower 16 bits of the B channel power measurement result. Only available in CDMA mode.

pmeter_integration_duc(12:0)

Integration time = 4 x pmeter_integration_duc + 1.

pmeter_sync_delay_duc(6:0)

Sync delay count in samples.

pmeter_interval_duc(9:0)

Interval time = 64 (pmeter_interval_duc + 1). Interval time must be greater than (not equal to) integration

time.

ssel_pmeter(2:0)

Sync source options.

pmeter_sync_disable

Turns off sync to the channel's power meter

GC5318 Operation

GC5318 Datasheet(PDF) 11 Page - Texas Instruments

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