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Application Note·BNC-AN-010 Rev A·October 2026·dc-62022201

How To Program Multi-Channel Synthesizers

This application note describes how to program the Model 855B multi-channel Signal Generator, introducing the basic multi-channel programming command syntax with an example that configures three channels individually.

Application Note·BNC-AN-010 Rev A·October 2026·dc-62022201
Contents
  1. 1Introduction
  2. 2Channel Selection
  3. 3Individual and Shared Settings
  4. 4Quick Command Reference
  5. 5Programming Examples

This application note describes how to program the Model 855B instruments with multiple output channels. Other BNC multi-channel Signal Generators (Model 825-M and the multi-channel Model 875) use the same SCPI 1999 command set; the programmer's manual of each model gives its channel syntax.

The basic multi-channel programming command syntax is introduced. An example shows how to configure multiple channels individually.

Figure 3. Photo: the Model 855B four-channel Signal Generator in its standard 19 inch 1U casing, whose channels the [:SOURce#] and :OUTPut# nodes address.
PhotoFigure 3. The Model 855B four-channel Signal Generator in its standard 19 inch 1U casing, whose channels the [:SOURce#] and :OUTPut# nodes address.

1Introduction

Devices with only one single channel provide one source and one output programming node. The [:SOURce]:… and :OUTPut:… ranges of command enable remote programming of reference configuration, source setup (frequency, power, modulations etc.) and output state (RF on/off).

Single channel device configuration showing Reference Oscillator, Source and Output nodes in series
SchematicFigure 1. A single-channel device. One reference oscillator node, one source node and one output node, addressed by [:SOURce]:ROSCillator, [:SOURce] and :OUTPut.

Multi-channel devices provide multiple [:SOURce]:… and :OUTPut:… programming nodes, each dedicated to one of the channels. Some sub-nodes are common to all channels: frequency, power and modulations are set per channel, while the reference is common to all channels.

Multi channel device configuration showing one shared Reference Oscillator feeding three Source and Output channels
SchematicFigure 2. A multi-channel device. One shared reference oscillator feeds the source and output nodes of channels 1 to 3, addressed as [:SOURce1] to [:SOURce3] and :OUTPut1 to :OUTPut3.

2Channel Selection

The channel can be selected in two different ways.

  • Append a channel index to the [:SOURce] and :OUTPut nodes: [:SOURce#] and :OUTPut#, for example :SOURce1.
  • Select the default source and output nodes. Commands within the [:SOURce] or :OUTPut nodes apply to the selected default source if no channel index is appended.

3Individual and Shared Settings

Some [:SOURce] and :OUTPut sub-nodes are common to all channels. Programming such sub-nodes will affect all channels at once. Channel index and default source selection won’t have any effect. This applies to the following sub-nodes:

Table 1.
Sub-nodeDescription
[:SOURce]:ROSCillatorReference configuration. Common for all sources.
[:SOURce]:SELectDefault source selection.

4Quick Command Reference

This quick command reference covers basic multi-channel functionality: reference configuration, channel selection, per-channel frequency, power and output state settings. Refer to the Signal Generator programmer’s manual (Software & Drivers) for a complete command reference.

[:SOURce]:SEL?
[:SOURce]:SEL? MINimum
[:SOURce]:SEL? MAXimum
[:SOURce]:SEL <x>

Gets or sets default source and output channel selection. Range 1…number of channels. The MAXimum query returns the number of sources available. Reset (*RST) default: 1.

[:SOURce#]:FREQuency?
[:SOURce#]:FREQuency <x>

Gets or sets source frequency. Applies to currently selected default source if [:SOURce#] node or source index # is omitted. Applies to source # (range 1…number of channels) otherwise.

[:SOURce#]:POWer?
[:SOURce#]:POWer <x>

Gets or sets source power. Applies to currently selected default source if [:SOURce#] node or source index # is omitted. Applies to source # (range 1…number of channels) otherwise.

[:SOURce]:ROSCillator:SOURce?
[:SOURce]:ROSCillator:SOURce INTernal|EXTernal

Gets or sets reference source. Applies to all channels. Reset (*RST) default: INTernal.

[:SOURce]:ROSCillator:OUTPut[:STATe]?
[:SOURce]:ROSCillator:OUTPut[:STATe] 0|1|OFF|ON

Gets or sets reference output state. Reset (*RST) default: 0|OFF.

:OUTPut#[:STATe]?
:OUTPut#[:STATe] 0|1|OFF|ON

Gets or sets output state. Applies to currently selected default output if the output index # is omitted. Applies to output # (range 1…number of sources) otherwise. Reset (*RST) default: 0|OFF.

5Programming Examples

Programming of the following setup:

  • Reference source external, reference output enabled
  • Source 1: 0 dBm, 1 GHz, output enabled
  • Source 2: 5 dBm, 2 GHz, output enabled
  • Source 3: 6 dBm, 2.1 GHz, output enabled

Method A: Specifying source and output indices

ROSC:SOUR EXT
ROSC:OUTP ON
SOUR1:POW 0 DBM
SOUR1:FREQ 1 GHZ
OUTP1 ON
SOUR2:POW 5 DBM
SOUR2:FREQ 2 GHZ
OUTP2 ON
SOUR3:POW 6 DBM
SOUR3:FREQ 2.1 GHZ
OUTP3 ON

Method B: Changing the default source selection

SOUR:SEL 1
POW 0 DBM
FREQ 1 GHZ
OUTP ON
SOUR:SEL 2
POW 5 DBM
FREQ 2 GHZ
OUTP ON
SOUR:SEL 3
POW 6 DBM
FREQ 2.1 GHZ
OUTP ON