A16 Spam Board (Analog Description); A24 If Multiplexer Board - Keysight N5224A Service Manual

Theory of Operation PNA Series Microwave Network Analyzers
Receiver Group Operation N5224A and N5225A
The A27 mixer brick sends the EXT TSET DRIVE LO OUT signal to a rear-panel connector for use with an
external test set. This same output connector on the A28 mixer brick is terminated.

A16 SPAM Board (Analog Description)

The A16 SPAM board contains digital and analog circuitry. For digital descriptions, refer to "A16 SPAM
Board (Digital Description)" on page 5-29.
In this assembly, the IF signals (A, B, C, D, and R for 4-port models and A, B, R1, and R2 for 2-port models)
from the A24 IF multiplexer board go through a gain stage where small signals are amplified to ensure that
they can be detected by the analog-to-digital converter (ADC).
All input 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 5-26
for more information on signal processing.

A24 IF Multiplexer Board

This assembly provides pulse modulation capability and routes the IF signal out through the rear panel
connectors for external use and routes external signals in through rear panel connectors to be included in
the signal processing.
In this assembly, on 4-port models, a single reference signal is selected from R1, R2, R3, and R4 to be sent on
to the A16 SPAM. On 2-port models the R1 and R2 reference signals are sent to the A16 SPAM.
The analog IF signals (A, B, C, D, and R for 4-port models and A, B, R1, and R2 for 2-port models) are sent to
the A16 SPAM board where they are converted to digital information.
Rear Panel Interconnects
The A24 IF multiplexer board includes the following rear panel interconnects.
PULSE I/O A DB-15 female connector. Pin assignments are listed in Table 5-5 on page 5-23.
5-22 Service Guide N5225-90001