B&K 4070A user manual External Bpsk 000,000.00 Hz 10.0 dBm, External Bpsk Mode Parameters

5.23 External BPSK Mode

Introduction

The External BPSK mode generates a phase shift keyed signal of fixed amplitude. The logic level on the Ext FSK In connector is used as a modulating signal to shift the output phase between 0 and 180 degrees. The modulation is suppressed carrier; i.e. no carrier energy is present in the output waveform.

NOTE: External BPSK is implemented by sampling the Ext FSK In line at 1.43 MHz. When a change in the state of the line is detected, the output phase is switched. Since this input is sampled, there may be a small but unpredictable delay between when the input changes and when the output phase is switched. This delay is never greater than 1/1,430,000 sec (=700 nS). The net result is a 700 nS worst-case jitter in the modulation edges. The faster you modulate the output, the more percentage of your modulating waveform this jitter becomes. Although you can modulate beyond the stated maximum rate, this jitter becomes increasingly greater percentage of your modulating waveform. The jitter becomes 10% of the high or low time at 35.75 KHz. This mode is available under

the “other” modes menu.

External BPSK Mode Parameters

The External BPSK mode has the following front panel display:

1

External BPSK

1,000,000.00 Hz - 10.0 dBm

Figure 5.23-1: External BPSK mode display

2

1. Carrier Frequency

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

2. 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 0.1 dBm steps.

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

By pressing this key, you can enter an offset voltage for the output waveform. For more information on output offsets refer to section 4.4.

Ext FSK Input

Apply the digital data to be modulated on this connector. When this input is high, the output phase is advanced 180 degrees. When this input is low, the output frequency is retarded 180 degrees. (I.e. this input switches the sign of the output carrier).

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BK Precision 4070A User Manual Rev.2.2