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Control Line ReviewReading the datasheet of a microwave control component.

An independent reference on microwave control components

Control Line Review

A switch, an attenuator and a log detector are sold on one page of figures each. This publication takes that page apart: what every parameter means, how it is measured, and where it misleads.

A microwave test bench seen from above with a coaxial component under test between two torque wrenches, calibration standards laid out on a grey mat
A component under test between two calibrated ports: every figure printed on a datasheet starts as a measurement made on a bench like this one.
  1. 50 Ω Reference impedance The system these parts are specified in
  2. 1.22 : 1 VSWR at 20 dB return loss One reflection, two scales
  3. 3 dB The half power point Where a stated bandwidth ends
  4. 10 to 90 % Switching time window The convention a rise time is read over

These four are definitions and one exact conversion, not measured performance. The VSWR column is computed as (1 + 10^(-20/20)) divided by (1 - 10^(-20/20)), which gives 1.222, recomputed on September 6, 2026. Nothing on this site states the performance of a named product. The same figures are published in the datasheet parameter index.

01 to 05

The five sections

From the component on the bench to the measurement that qualifies it.

  1. A row of small coaxial SPDT switch bodies on an anti static mat, control pins upward, one unit opened to show the internal microstrip carrier

    Solid-State Microwave Switches

    What the topology decides before any figure on the page does.

    Section 01

  2. A voltage variable attenuator module with an analog control lead clipped to a bench supply, a digital multimeter behind it showing a control voltage

    Variable Microwave Attenuators

    Range is the easy column. Flatness and accuracy are the ones that decide.

    Section 02

  3. An oscilloscope displaying a rectangular video pulse next to a small detector log video amplifier module connected by a short semi rigid coaxial jumper

    Detectors and Log Video Amplifiers

    A curve, not a number: what a log detector actually promises.

    Section 03

  4. An opened aluminum microwave housing showing several microstrip carriers, a multipin control connector on the wall and coaxial launchers at both ends

    Integrated Microwave Assemblies

    One housing, several functions, and a different way of specifying.

    Section 04

  5. A vector network analyzer screen showing two traces against a logarithmic scale, with a calibration kit open on the bench and a torque wrench beside it

    Measuring and Specifying RF Components

    Where every number on every other page of this site comes from.

    Section 05

Reference

The two standing references

Cited by every section, so that no page has to define a term twice.

  1. A printed specification sheet held flat on a bench by a coaxial adapter, a mechanical pencil resting across a column of parameter rows

    The datasheet parameter index

    Definition, unit, measurement and trap, for every column of a control component specification.

    Reference

  2. An open technical reference book beside a coaxial through line and two calibration standards arranged on a dark bench mat under a task lamp

    Glossary of control terms

    The terms a specification uses and never defines, with the confusion each one causes.

    Reference

Latest

Everything published here

Every page of the publication, newest first.

  1. What a Solid-State Microwave Switch Is

    Switches

    No moving part, one mechanism, and three numbers that come out of it. This is the primer the rest of the switch section is built on.

  2. Absorptive and Reflective Switches

    Switches

    The off port either sends the power back or turns it into heat. That single difference decides what the rest of the chain sees.

  3. Switching Speed and the Driver Behind It

    Switches

    Two parts built on the same diode can be specified very differently in speed. The difference is almost never the diode.

  4. What a Variable Attenuator Does in a Chain

    Attenuators

    Controlled loss is a design tool, not a defect. This is what the tool is for and what its specification is actually promising.

  5. Voltage Variable and Digital Step Attenuators

    Attenuators

    Neither control philosophy is more accurate in general. They fail differently, and a chain is designed around the failure it can live with.

  6. Flatness, Accuracy and Monotonicity

    Attenuators

    An attenuator can be accurate and useless. These three columns describe three unrelated ways of being wrong.

  7. What a Detector Log Video Amplifier Is

    Detectors and DLVAs

    Power in, voltage out, compressed logarithmically. The specification that matters is the shape of the line, not a point on it.

  8. Reading a Log Detector Transfer Curve

    Detectors and DLVAs

    Dynamic range without a logging error limit is not a specification. This is how the two are read together.

  9. Tangential Sensitivity and Video Bandwidth

    Detectors and DLVAs

    These two figures are traded against each other. Read either one alone and two parts with the same range will surprise you.

  10. What an Integrated Microwave Assembly Integrates

    Assemblies

    An assembly is not a bigger component. It is a change of interface, and the specification changes with it.

  11. Screening and Qualification Documents

    Assemblies

    A method number points at a written procedure. It says the described test was passed under the described conditions, and nothing more.

  12. Insertion Loss and Isolation

    Measurement

    One measurement, taken twice: once through the path that conducts and once through the path that blocks.

  13. VSWR and Return Loss

    Measurement

    A ratio and a decibel figure describing the same reflected wave. The arithmetic between them is short and worth doing once.

  14. Calibration and Connector Care

    Measurement

    The instrument is rarely the weak link. A hand tightened connector and a calibration from yesterday are.

Start here

Four pages to start with

The mechanism, the topology choice, the reflection scales and the detected output.

  1. A small coaxial SPDT switch body opened on a bench mat, its internal microstrip carrier and control pins visible under a magnifier

    What a Solid-State Microwave Switch Is

    No moving part, one mechanism, and three numbers that come out of it. This is the primer the rest of the switch section is built on.

    September 6, 2026

  2. Two coaxial switch bodies side by side on a grey mat, one with an internal termination visible through an open lid, a fifty ohm load beside them

    Absorptive and Reflective Switches

    The off port either sends the power back or turns it into heat. That single difference decides what the rest of the chain sees.

    September 6, 2026

  3. A brass coaxial mismatch standard, a semi rigid jumper and two small adapters laid on a grey bench mat, a torque wrench beside them and an instrument out of focus behind

    VSWR and Return Loss

    A ratio and a decibel figure describing the same reflected wave. The arithmetic between them is short and worth doing once.

    September 6, 2026

  4. A detector log video amplifier module connected by a semi rigid jumper to a source, its video output on a short coaxial lead running off the bench

    What a Detector Log Video Amplifier Is

    Power in, voltage out, compressed logarithmically. The specification that matters is the shape of the line, not a point on it.

    September 6, 2026

Control Line Review publishes nothing about a named product and holds no commercial relationship with any maker of the parts it describes. How the pages are written, and what is deliberately left out, is on the about page. Where each figure comes from is on sources and method.