Service Guide N5230-90024 5-19
PNA Series Microwave Network Analyzers Theory of Operation
N5230C Receiver Group Operation
Receiver Group Operation
The receiver group measures and processes the input signals into digital information for processing and
eventual display. Figure 5-6 on page 5-20 is a simplified block diagram of the receiver functional group.
In this section the following assemblies are described:
• A20 Mixer Brick
• A5 SPAM Board (Analog Description)
A20 Mixer Brick
This assembly contains four identical amplifiers, mixers, and filters. The test signals (channels A and B) and
the reference signals (channels R1 and R2) are mixed with a synthesized source signal that is 250 kHz higher
than the source incident signal to produce a 250 kHz IF signal.
This analog IF signal is sent to the A5 SPAM board where it is converted to digital information.
A5 SPAM Board (Analog Description)
The A5 SPAM board contains digital and analog circuitry. For digital descriptions, refer to “A5 SPA M Boar d
(Digital Description)” on page 5-24.
In this assembly, the IF signals from the A, B, R1, and R2 mixers go through a gain stage where signals less
than 40 dBm are amplified by 34 dB to ensure that they can be detected by the analog-to-digital converter
(ADC).
All four signals are sampled simultaneously by the ADCs, where they are converted to digital form. The ADC
conversions are triggered by timing signals from the digital signal processor (DSP) in response to commands
from the central processing unit (CPU). The digitized data is processed into magnitude and phase data by the
DSP and sent to the CPU random access memory (RAM) by way of the peripheral component interconnect
(PCI) bus.
The processed and formatted data is finally routed to the display, and to the general-purpose interface bus
(GPIB) for remote operation. Refer to “Digital Processing and Digital Control Group Operation” on page 5-21
for more information on signal processing.
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