HP 8753E manual Length, Requirements, No loss. Characteristic impedance ZO need not be known

The TRL Calibration Procedure

Requirements for TRL Standards

When building a set of TRL standards for a microstrip or fixture environment, the requirements for each of these standard types must be satisfied.

Types

THRU (Zero length)

THRU (Non-zero

length)

REFLECT

LINE/MATCH WW

LINE/MATCH

(WCH)

Requirements

qNo loss. Characteristic impedance (ZO ) need not be known.

q&?I= S12= 1 LO0

0 s11= s22 = 0

qZO of the thru must be the same as the line. (If they are not the same, the average impedance is used.)

qAttenuation of the thru need not be known.

qIf the thru is used to set the reference plane, the insertion phase or electrical length must be well-known and specified. If a non-zero length thru is specified to have zero delay, the reference plane is established in the middle of the thru, resulting in phase errors during measurement of devices.

qReflection coefficient (I’ ) magnitude is optimally 1.0, but need not be known.

qPhase of I’ must known and specified to within f l/4 wavelength or f 90’. During computation of the error model, the root choice in the solution of a quadratic equation is based on the reflection data. An error in delinition would show up as a 180° error in the measured phase.

qP must be identical on both ports.

qIf the reflect is used to set the reference plane, the phase response must be well-known and specified.

qZ0 of the line establishes the reference impedance of the measurement (i.e. Sll = &2 = 0). The calibration impedance is defined to be the same as Z0 of the line. If the ZO is known but not the desired value (i.e., not equal to 50 a), the SYSTEMS ZO selection under the TRL/LRM options menu is used.

qInsertion phase of the line must not be the same as the thru (zero length or non-zero length). The difference between the thru and line must be between (20° and 1600) f n x 1800. Measurement uncertainty will increase significantly when the insertion phase nears 0 or an integer multiple of 180”.

qOptimal line length is l/4 wavelength or 90” of insertion phase relative to the thru at the middle of the desired frequency span.

qUsable bandwidth for a single thru/Iine pair is 8:l (frequency spanstart frequency).

qMultiple thru/line pairs (ZO assumed identical) can be used to extend the bandwidth to the extent transmission lines are available.

qAttenuation of the line need not be known.

qInsertion phase must be known and specified within f l/4 wavelength or f 90”.

qZ0 of the match establishes the reference impedance of the measurement.

qP must be identical on both ports

Application and Operation Concepts 6-97