Agilent Technologies 8510 - Manual (Page 9)

9
Each standard is described using the Standard
Definition Table in accordance with the 1- or 2-
port model. The Standard Definition table for a
waveguide calibration kit is shown in Table 1. Each
standard type (short, open, load, thru, and arbi-
trary impedance) may be defined by the parame-
ters as specified below.
• Standard number and standard type
• Fringing capacitance of an open, or inductance
of a short, specified by a third order polynomial
• Load/arbitrary impedance, which is specified as
fixed or sliding
• Terminal resistance of an arbitrary impedance
• Offsets which are specified by delay, Z
0
, R
loss
• Frequency range
• Connector type: coaxial or waveguide
• Label (up to 10 alphanumeric characters)
Standard number
A calibration kit may contain up to 21 standards
(See Table 1). The required number of standards
will depend on frequency coverage and whether
thru adapters are needed for sexed connectors.
For the WR-62 waveguide example, four standards
will be sufficient to perform the FULL 2-PORT cali-
bration. Three reflection standards are required,
and one transmission standard (a thru) will be suf-
ficient to complete this calibration kit.
Standard type
A standard type must be classified as a “short”
“open,” “load”, “thru,” or “arbitrary impedance.”
The associated models for reflection standards
(short, open, load, and arbitrary impedance) and
transmission standards (thru) are shown in Figure 1.
For the WR-62 waveguide calibration kit, the four
standards are a
1 /
8
λ λ and
3 /
8
λ λ offset short, a fixed
matched load, and a thru. Standard types are
entered into the Standard Definition table under
STANDARD NUMBERS 1 through 4 as short, short,
load, and thru respectively.
Open circuit capacitance: C
0
, C
1
, C
2
and C
3
If the standard type selected is an “open,” the C
0
through C
3
coefficients are specified and then used
to mathematically model the phase shift caused by
fringing capacitance as a function of frequency.
As a reflection standard, an “open” offers the
advantage of broadband frequency coverage, while
offset shorts cannot be used over more than an
octave. The reflection coefficient (
Γ = pe-
je
) of a
perfect zero-length-open is 1 at 0° for all frequen-
cies. At microwave frequencies however, the magni-
tude and phase of an “open” are affected by the
radiation loss and capacitive “fringing” fields,
respectively. In coaxial transmission media, shield-
ing techniques are effective in reducing the radia-
tion loss. The magnitude (p) of a zero-length
“open” is assigned to be 1 (zero radiation loss) for
all frequencies when using the Agilent 8510
Standard Type “open.”