B&K 4070A user manual Internal AM Mode

5.2 Internal AM Mode

Introduction

The Internal AM mode generates an amplitude-modulated signal form with fixed carrier and modulating frequencies. An internally generated sinusoid is used as a modulating signal to vary the amplitude of a carrier sinusoid. The modulation waveform is not suppressed carrier; i.e. a fixed amount of carrier power is always present in the modulated signal. . Internal AM mode could be entered by pressing “Mode”> “AM” >”1” key at any time.

Internal AM Mode Parameters

The Internal AM mode has the following front panel display:

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	Int AM: 1,000 Hz	Percent Mod: 100%
3	1,000,000.00 Hz	PEP level: -10.0 dBm

Figure 5.2-1: Internal AM mode display

1. Modulating Frequency

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4

In this field enter the frequency of the modulating sinusoid, from 0 Hz to 10,000 Hz in 1 Hz steps.

2. Percentage modulation

In this field enter the degree to which the modulating signal is allowed to change the carrier amplitude. You may enter from 0% (no change) to 100% (maximum change) in 1% steps.

To enter a value, type 1 to 3 numeric digits. If you type 3 digits, the value is automatically entered. If you only type 1 or 2 digits, you can press the MHz key or the KHz key or the Hz key (all are equivalent) to enter the percentage value.

3. Carrier Frequency

In this field enter the frequency of the carrier, from 0 Hz (DC) to 21.5 MHz in 0.01 Hz steps.

4. PEP Level

In this field enter the output level, from 4 mVp -p to 10 Vp -p in 1 mV steps or from -44.0 dBm to +24.0 dBm in .1 dBm steps.

NOTE: The level specified in Internal AM mode is the Peak Envelope Power, or PEP. As a peak-to-peak value, this level represents the maximum peak-to-peak voltage swing that will result from a 100 percent modulated carrier. If no modulating signal were applied, the unmodulated carrier would have only half the peak-to-peak swing of a 100% modulated carrier.

NOTE: The level specified is a 50O loaded level. This is the level of the signal, which will appear across a 50O load connected to the SIG Out connector. Into an open circuit, the output swing will be twice the value entered.

Offset

You can enter an offset voltage for the output signal. For more information on output offsets refer to section 4.4.

Ext Gating Input

This TTL compatible input can be used to gate the output signal on or off. A logic high level turns off the output. For further information on the Ext Gating Input, refer to section 2.0.

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BK Precision 4070A User Manual Rev.2.2