Service Guide 12-17
8719ET/20ET/22ET Theory of Operation
8719ES/20ES/22ES Source Group Theory
RF Network Analyzers
Figure 12-4 Simplified Diagram of the Source Block Diagram
The YIG oscillator has a main coil and an FM coil. These are analogous to the woofer and
the tweeter in a stereo speaker: the woofer reproduces low frequencies and the tweeter
reproduces high frequencies. Similarly in the YIG oscillator, the main coil allows large,
slow changes in frequency but cannot respond to high frequency deviations, which are sent
to the faster-acting FM coils.
The tune current from the A11 phase lock assembly splits into two paths. One path is
lowpass filtered, removing high frequency components, and goes to the YIG main coil; the
other path is highpass filtered, removing low frequency components, and goes to the YIG
FM coils. The filters are matched in stop-band response, such that one picks up where the
other leaves off.
In the low band (for all models), the 3.85 to 6.35 GHz output of YIG1 and the fixed 3.8 GHz
output of the A57 fixed oscillator are mixed in the A53 mixer/amplifier assembly. In this
band, A5 and A6 switch A53 into the circuit.
The high band of the 8719ET/ES and 8720ET/ES (mid band of 8722ET/ES) uses the full
band output of YIG1.
Table 12-3 Frequency Bands for All Models
Band Frequency Range
Low for all models
50 MHz to 2.55 GHz
High for 8719ET/ES models 2.55 GHz to 13.05 GHz
High for 8720ET/ES models
2.55 GHz to 20.05 GHz
Mid for the 8722ET/ES models
High for the 8722ET/ES models
20.05 GHz to 40.05 GHz
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