Anritsu 373XXA manual Analog Subsystem Assemblies, 3ANALOG Subsystem, Signal Source Module, Sdm

SYSTEM DESCRIPTION ANALOG SUBSYSTEM ASSEMBLIES

7-3ANALOG SUBSYSTEM	The following paragraphs briefly describe the major assemblies that com-
ASSEMBLIES	prise the 373XXA Analog Subsystem. Descriptions of the functions per-
	formed by each assembly are also included.
Signal Source Module	The Signal Source Module consists of the items listed below; refer to the
	block diagram of the Analog Subsystem (Figure 7-2) at left.
	￿ 2-20 GHz YIG Oscillator Assembly
	￿ A21A1 YIG/Bias Controller PCB
	￿ A21A2 Source Control PCB
	￿ Switched Filter Assembly
	￿ Down Converter Assembly
	The Signal Source Module is a swept frequency signal generator that
	produces a phase locked (and leveled) output signal within a range of
	22.5 MHz to 20 GHz. All Series 373XXA VNA models employ
	phase-lock control of the signal source module so that the output fre-
	quency is accurate and stable. The output signal is phase locked by
	the –6 MHz/volt control signal fed back from the A8 Source Lock/Sep-
	aration Control PCB Assembly (which is described in following para-
	graphs).
	All Series 372XXB VNA models use a single YIG-tuned oscillator to
	produce fundamental frequency source signals from 2.0 to 20 GHz. All
	other output frequencies are derived from the fundamental frequen-
	cies generated by the YIG-tuned oscillator. The signal source output
	frequencies for the low end portion of the frequency range (22.5 MHz
	to 2.0 GHz) are produced by down converting YIG fundamental signals
	in the range of 6.3225 to 8.3 GHz.
	For Model 37369A, the signal source output frequencies for the high
	end portion of the frequency range (20 to 40 GHz) are produced by the
	Switched Doubler Module that doubles the YIG fundamental signals
	in the range of 10 to 20 GHz. The Switched Doubler Module (SDM) is
	located in the Test Set Module (described below.) The A21A2 Source
	Control PCB assembly provides all bias and control signals for the
	SDM.

The YIG-tuned oscillator generates a high-power RF output signal that has low broadband noise and low spurious content. The frequency of the YIG-tuned oscillator is controlled by means of :

￿The YIG main tuning coil

￿The YIG FM (fine tuning) coil

The system A9 Main Microprocessor PCB sends the data that repre- sents the desired operating frequency to the A21A2 (Source Control) PCB, which converts the frequency data to analog signals. These sig-

373XXA MM 7-7