Colby Instruments XT-100 - Chapter 1.0; Description of the XT-100 Programmable Delay Line Instrument; Introduction; Delay Line Structure and Design

Chapter 10
Description of the XT-100 programmable delay line instrument
11 Introduction
The XT-100 Programmable Delay Line Instrument offers precision programmable delay from 0 to 625.0 picoseconds (ps) range with a
step resolution precision to 0.50 ps per step and wideband signal frequency input from DC to 18 GHz.
The XT-100 offers electrical delay (or phase shift) through a patented electromechanical trombone unit by varying the total signal path
length. Movement is controlled by a high precision aerospace-grade hybrid stepper motor. Step resolution is to 0.50 ps per step with
excellent repeatability.
The XT-100 can be operated locally via Web Browser UI over an Ethernet interface or optionally via MT-100A MicroTerminal over a RS-232
serial port interface. Delay can be set or entered manually or automated via program control. Remote control via Ethernet TCP/IP, RS-
232 Serial interface, or Web Browser UI and SCPI command interface is supported.
All signal input and output connections are easily accessible at the front panel and are terminated with female SMA (50 Ω) connectors.
12 Delay Line Structure and Design
The XT Series of Programmable Delay Line Instruments is based on an “electromechanical trombone” or moveable delay line. A high-
frequency signal passing through an extended or contracted trombone experiences correspondingly more or less electrical delay due to
the varying total signal path-length. The electrical delay corresponds directly to phase shift when measured in the frequency domain.
A digital hybrid precision stepper motor with a custom precision lead screw is used to position a sled on which one part of the trombone
tubing is attached. Precision interfaces are designed to minimize impedance mismatches and a proprietary contact design achieves
reliability while minimizing any signal loss or noise.
An embedded CPU microcontroller processes commands from any of the attached hardware interfaces: Ethernet (Web Browser UI, TCP/
IP) or RS-232 Serial (optional MT-100A MicroTerminal, or Terminal Emulator program). Commands are processed to move the stepper
motor in high-resolution step increments as ne as 0.50 picoseconds(ps) of step resolution (or 0.18 degrees per 1 GHz signal input).
The model XT-100 has one trombone in the base unit. Total delay range can be extended by the in-series addition of one or more delay
sections. Each delay section is a pair of aerospace grade microwave relay switches and precision cut semi-rigid coaxial cable in binary
step size lengths corresponding to multiples of 625.0 ps. e.g., 625 ps, 1.25 ns, 2.50 ns, etc. Total range of delay is the sum of the entire
path length of each of the delay sections. With the combination of binary step sized delay sections and the electromechanical trombone,
any 0.50 ps step can be achieved from 0 to total range of the instrument.
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COLBY INSTRUMENTS XT-100 VERSION 1.0 OPERATING AND PROGRAMMING MANUAL