HP 8530A, Руководство по эксплуатации и программированию, Страница: 53 / 439

Principles of Operation
Principles of Operation
This information is provided so you can have a better understanding of how the HP 8530A
makes measurements . If desired, you can skip this section and come back to it when
convenient.
Description of HP 8530A Internal Processes
A simplied block diagram of the HP 8530A receiver is shown in Figure 2-1. It is a high
performance vector receiver with four inputs , two independent digital processing channels , and
an internal microcomputer that controls measurement, digital processing, and input/output
operations . Examples of \digital processing" are features such as averaging, time domain,
calibration, and so on. A special System Bus gives the receiver complete control over the
RF source and, if required, LO source . This interface allows the receiver to make hard copy
outputs to HP-IB compatible printers or plotters . Two RS-232 ports are also supplied for
printing or plotting.
The system must contain a frequency converter , which down converts the RF measurement
frequencies to the 20 MHz IF required by the HP 8530A. T o create the IF frequency , the HP
8511A/B frequency converter uses a built-in local oscillator . The built-in LO is digitally tuned
by the HP 8530A. The digital tuning data is sent over the \T est Set Interconnect" that links
the HP 8530A and the HP 8511A/B . The local oscillator mixes the measurement signals with
a similar frequency that is oset by 20 MHz. The result is the 20 MHz IF signal. Other down
converters , such as the HP 85310A, require another source to supply an LO signal. The HP
8530A tunes external LO sources with HP-IB commands sent over the System Bus .
2-2 System Overview