R&S
®
ZVA / R&S
®
ZVB / R&S
®
ZVT Measurement Examples
Calibration
Operating Manual 1145.1084.12 – 30 75
TRL calibration with 3 Lines
Suppose you want to perform a TRL calibration using coaxial air Lines for the sweep range between 200
MHz and 40 GHz. The through standard has length l
thr
. The ratio of the stop frequency to the start
frequency is 200, therefore an accurate calibration with a single Line standard or even two Lines is not
possible. However, it is possible to calibrate the entire sweep range with three Lines of appropriate
(electrical) lengths l
1
> l
2
> l
3
; see TRL Extensions.
To determine the electrical lengths of the three Lines...
1. Select the length of the longest Line such that the transmission phase of (l
1
– l
thr
) at the start
frequency of 200 MHz is equal to 20 deg: l
1
= λ (200 MHz / 18) + l
thr
= c
0
/ (18 * 200 MHz) + l
thr
=
8.328cm + l
thr
, where c
0
is the velocity of light. This length corresponds to a delay time of Δt
long
=
277.78 ps + l
thr
/c
0
. The maximum frequency of the longest Line is 8 times its minimum frequency,
i.e. 1.6 GHz.
2. Select the length of the shortest Line such that the transmission phase of (l
3
– l
thr
) at the stop
frequency of 40 GHz is equal to 160 deg: l
3
= 4*λ (40 GHz / 9) + l
thr
= 4* c
0
/ (9 * 40 GHz) + l
thr
=
0.333 cm + l
thr
. This length corresponds to a delay time of Δt
long
= 11.11 ps + l
thr
/c
0
. The minimum
frequency of the shortest Line is 1/8 of its maximum frequency, i.e. 5 GHz.
3. Select the length of the third Line in-between l
1
and l
2
, e.g. at 1.666 cm. This corresponds to a
frequency range between 1 GHz and 8 GHz.
Perform the calibration as in the example above; TRL calibration with 2 Lines. If you create a calibration kit
with the three Lines and click Channel – Calibration – Cal Kits – View/Modify Kit – Optimize Line Freq
Ranges, the analyzer will calculate the following transition frequencies between the lines:
1.5 GHz for the transition between Line 1 and Line2.
7.5 GHz for the transition between Line 2 and Line 3.
TRL calibration with low-frequency TRM extension
Suppose you want to perform a TRL calibration using coaxial air Lines for the sweep range between 300
MHz and 4 GHz using a Line standard with an electrical length of l
long
= 16.6666 cm and a through
standard of l
thr
. << l
long
. TRL calibration is known to become inaccurate in the frequency range below f
TRM
=
c
0
/(18*l
long
) = 1 GHz; see TRL Calibration with Two Lines. It is therefore advisable to perform a combined
TRL/TRM calibration using an additional match or sliding match standard.
1. Make sure that the calibration kit contains a match or sliding match standard, in addition to the
Line, the through and the reflect standards required for the TRL calibration. If necessary generate
a cal kit file as described in section TRL calibration with 2 Lines.
2. Click Channel – Calibration – Start Cal – Two Port P1 P2 – TRL... to open the calibration wizard
(see also Manual calibration).
3. In the Physical VNA Test Port Connector(s) dialog, select your Connector type and Calibration Kit.
Click Next >.
4. In the Measured Standards dialog opened, perform the calibration sweeps for the match (or
sliding match) and the reflect standard at all ports. In addition, perform the calibration sweeps for
the through and the Line (Line 1) between any combination of ports.
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