Specify the target total-power output of one or more correlator channels.

Arguments:

Receivers receivers

The set of receivers to target.

Bands bands

The set of frequency bands to target.

TotalPower power

The desired total-power level after the removal of the offsets of the individual total power detectors.

Example 1:

The following example asks the channelizer task to find the attenuations that will result in a total power detector output of 2.5 volts from each correlator channel. This initiates a lengthy (up to 20 seconds) process that adjusts the individual attenuators until the best match in power outputs is found. In the example, the acquired function is used to wait for this process to complete (or fail).

 tp all, all, 2.5
 until $acquired(channels)

Context:

The CBI has 13 receivers (rx0..rx12) who's 10GHz bandpasses are split into 10 bands (band0..band9) by a channelizer. The resulting 130 signal paths are refered to as channels. Every channel contains a programmable attenuator for setting the input power to the corresponding correlator input. The amount of attenuation needed by each channel depends on the sensitivity of the various components in the signal path and the brightness of the source. For bright planets more attenuation will be needed than when observing the CMB. This attenuation can be set directly using the attenuate command, or it can be set with a target total-power output in mind using the tp command. The latter command allows a target total power detector output to be specified for one or more channels at a time. For each channel it sets the attenuation to the maximum value available, then gradually decreases it until two total power levels that bracket the requested level are found. It then chooses the closest. One iteration of this process is performed on every second integration until the optimal attenuations of all of the target channels have been found (or an error occurs). At this point the control program is notified of the completion and the $acquired(tp) returns true.

Note that if any command that involves the channelizer, such as the channel, attenuate, channelizer, tpzero or another tp command, is initiated before a previous tp (or tpzero) command is complete, the new command replaces the previous one, but only in those channels that are common to both commands. In particular the "channelizer off" command cancels any ongoing commands in all channels.

Note that all of the attenuators are set to maximum attenuation when the control system starts.