The SCALE menu for Smith Charts contain two unique buttons to control the display scale (Scale Selection) and control of the phase wrapping (Wrap Setup). Both are described in the sections below.
SCALE Smith Chart Impedance Menu
Menu Identification
• The appearance and button availability of the SCALE menu depends on the settings on the DISPLAY menu. Consult the section above for SCALE menu identification and prerequisites.
Select displays the WRAP SETUP menu which allows the user to define if wrapping of on or off, and if on, the wrap offset in degrees.Additional Common Buttons
The SMITH SCALING Impedance and the SMITH SCALING Admittance menus provide discrete Smith Chart scaling options from the default 0 dB display. Both the impedance and admittance menus provide the same functions. The user can zoom in to areas of interest by expanding the display at selectable levels of –10 dB, –20 dB, or –30 dB. Alternatively, the Smith Chart display can be compressed to a level of 3 dB. No incremental levels are provided. An example of Smith Chart scaling follows the menu description below.
Prerequisites
• The TRACE FORMAT is set to Smith (R+jX Impedance).
• MAIN | Scale | SCALE Smith Impedance | SCALE SMITH IMPED. | SMITH SCALING IMPEDANCE
Button Selection Group
• The five buttons of the SMITH SCALING IMPEDANCE menu form a button selection group where the selection of any one button de-selects the other four buttons.
SCALE Smith Impedance Menu
0 dB (Refl 1.0)
The default Smith Chart Impedance scale is 0 dB with a reflection coefficient of 1.0.
–10 dB (Refl 0.3162278)
Expands the Smith Chart Impedance trace display and sets the scale to –10 dB with a reflection coefficient of 0.3162278.
–20 dB (Refl 0.10)
Expands the Smith Chart Impedance trace display and sets the scale to –20 dB with a reflection coefficient of 0.10.
–30 dB (Refl 0.0316228)
Expands the Smith Chart Impedance trace display and sets the scale to –30 dB with a reflection coefficient of 0.03162278.
+3 dB (Refl 1.4125375)
Compresses the Smith Chart Impedance trace display and sets the scale to +3 dB with a reflection coefficient of 1.4125375.
Smith Chart Scaling Operations
A typical Smith Chart display is shown below at the default 0 dB setting.
Smith Chart Impedance Display – Typical Results at 0 dB
Expanded Smith Chart Displays
The user can zoom into the display by expanding the Smith Chart as shown in the figures below:
Smith Chart Impedance Display – Expanded to -10 dB
Smith Chart Impedance Display – Expanded to -20 dB
Smith Chart Impedance Display – Expanded to -30 dB
Smith Chart Compressed Display
The 3 dB selection compresses the Smith Chart display so that the outer edges can be easily examined. The figure below shows an example of the original 0 dB display on the left, and the compressed 3 dB display on the right.
Compressed Smith Chart Example – 0 dB and 3 dB
– Original Smith Chart Impedance display at 0 dB on left.
– Compresses Smith Chart Impedance display at 3 dB at right.
WRAP Setup Menu
Prerequisites
• The WRAP SETUP submenu is linked to the SCALE Smith Impedance or the SCALE Smith Admittance menus and is only available if the DISPLAY menu is set to a Smith Impedance (R+jX) or Smith Admittance (G+jB) trace display.
This menu is available when TRACE FORMAT is set to Smith (G+jB Admittance) and either Linear/Phase, Log/Phase, Real/Imaginary, or Impedance is selected. Button units are set to:
• Button Units: º (Degrees)
Resolution (Units/Div)
The Resolution button is unavailable.
Reference Value (Units)
The Reference Value button is unavailable.
Reference Position (Number)
The Reference Position button is unavailable.
Scale Selection
The button displays the Smith Chart scale in dB. Select displays the SMITH SCALING menu.
Select displays the WRAP SETUP menu which allows the user to define if wrapping of on or off, and if on, the wrap offset in degrees.Additional Common Buttons
