RF Switch Matrix
Encyclopedia
RF Switch Matrix or Microwave
Switch Matrix or Switch Matrix
An RF/Microwave Switch Matrix is used in test systems, in both design verification and manufacturing test, to route high frequency signals between the device under test
(DUT) and the test and measurement equipment. Besides signal routing, the RF/Microwave Switch Matrix may also contain signal conditioning including passive signal conditioning devices, such as attenuators, filters
, and directional couplers, as well as active signal conditioning, such as amplification and frequency converters. Since the signal routing and signal conditioning needs of a test system differ from design to design, RF/Microwave Switch Matrices typically have to be custom designed by the test system engineer or a hired contractor for each new test system. The Switch Matrix is made up of switches and signal conditioners that are mounted together in a mechanical infrastructure or housing. Cables are employed to interconnect the switches and signal conditioners. The switch matrix then employs some type of driver circuit and power supply
to power and drive the switches and signal conditioners. The switch matrix uses connectors or fixtures to route the signal paths of the sourcing and measurement equipment to the DUT. The switch matrix is typically located close to DUT in the test system to shorten the signal paths to the DUT thus reducing insertion loss and signal degradation.
Advantages of creating your switch matrix in-house:
Contracting out advantages:
Electromechanical Switches and Solid State Switches, also known as electronic switch
es. Coaxial electromechanical switch
es can be further divided into two categories based on their architecture, latching relay and non-latching relay. Solid state switches come in three types: PIN diode
, FET
, and hybrid. The advantages of solid state switches over EM switches include they have much faster switching speed (at least 10,000 times faster), they have an almost infinite life, and they are very stable and repeatable. On the other hand, since solid state switches have non-linear portions over their frequency range their bandwidth is limited. Also, EM switches provide better insertion loss
, VSWR, power handling, and isolation specifications. For these reasons EM switches are used much more often in switch matrix designs.
input that is used to perform signal integrity checks on the satellite feeds. Such a design would require 5 SP4T coaxial EM switches as well as interconnecting coax cable for the signal routing along with a mechanical infrastructure, power supply, and switch driver circuit to mount, power, and operate the switches.
An example of a more complex switch matrix is an application that is measuring jitter
on multiple high speed serial data buses. The switch matrix inputs the data bus signals then provides the proper switching and signal conditioning for the signals before feeding the signals to test and measurement instruments. This custom switch matrix employed 14 EM switches and a number of different signal conditioners including: power splitters, amplifiers, mixers, filters, and attenuators.
RF Switch Matrices are also used heavily in the Televison Broadcast market for the reception and re-broadcast of TV Channels. Typically a Cable TV Headend will contain a matrix to enable multiple dishes aligned to different satellites to be routed to a bank of receivers. The RF Switch Matrix allows channel changes to be made remotely without any interuptions.
Test equipment manufacturers offer instruments that provide a power supply
, driver circuitry, and software drivers that essentially saves a test system designer time and cost by eliminating two of the six switch matrix design challenges: power and control hardware design as well as software driver development. Many companies have introduced new product concepts that aid in custom switch matrix design. These new products offers test system designers a power supply
, driver circuitry, and software drivers all wrapped together in a mainframe. The mainframe provides flexible mounting for switches and other components as well as blank front and rear panel that can be easily modified to fit a design need. These new products eliminates 3 of the 6 design challenges: mechanical design, power and control hardware design, and software driver development
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
Switch Matrix or Switch Matrix
An RF/Microwave Switch Matrix is used in test systems, in both design verification and manufacturing test, to route high frequency signals between the device under test
Device under test
Device under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.-In semiconductor testing:...
(DUT) and the test and measurement equipment. Besides signal routing, the RF/Microwave Switch Matrix may also contain signal conditioning including passive signal conditioning devices, such as attenuators, filters
Electronic filter
Electronic filters are electronic circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both...
, and directional couplers, as well as active signal conditioning, such as amplification and frequency converters. Since the signal routing and signal conditioning needs of a test system differ from design to design, RF/Microwave Switch Matrices typically have to be custom designed by the test system engineer or a hired contractor for each new test system. The Switch Matrix is made up of switches and signal conditioners that are mounted together in a mechanical infrastructure or housing. Cables are employed to interconnect the switches and signal conditioners. The switch matrix then employs some type of driver circuit and power supply
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
to power and drive the switches and signal conditioners. The switch matrix uses connectors or fixtures to route the signal paths of the sourcing and measurement equipment to the DUT. The switch matrix is typically located close to DUT in the test system to shorten the signal paths to the DUT thus reducing insertion loss and signal degradation.
Benefits of an RF/Microwave Switch Matrix
The purpose of a switch matrix is to move the signal routing and signal conditioning to one central location in the test system versus having it all distributed at various places in the test system. Moving the signal routing and signal conditioning to a single location in the test system has the following advantages:- Calibration plane between the DUT and test equipment becomes smaller and centralized making it easier to characterize.
- Switches and signal conditioners have similar power, mounting, and driver requirements so moving them to a single location means you will only need a single power supply and driver circuit to power and control them.
- Short signal paths reduce insertion loss and increase signal integrity.
- Exact length signal paths are possible to control phase issues.
- Simplifies service and support.
Making It vs Buying It
Switch matrices present a unique problem to test system designers because the signal conditioning needs, the frequency range, the bandwidth, and power aspects change from application to application. So test and measurement companies cannot provide a one size fits all solution. This leaves test system designers with two choices for their switch matrix design: Create an in-house solution or contract it out.Advantages of creating your switch matrix in-house:
- Proprietary concerns can be a big issue especially in the Aerospace Defense industry. Creating a switch matrix in-house makes proprietary concerns a non-issue.
- Using spare human resources may be less costly.
- Being the first to develop an emerging technology into a finished product can be very profitable for a company. When building a switch matrix in-house the timely process of shopping around for the right contractor is bypassed. A company is in control of the amount of daily man hours spent developing a switch matrix.
- Successive switch matrix designs can be highly leveragable from design to design. The switch driver hardware and software, the mechanical designs, the power supply, etc. can all be leveraged from design to design with little or no modification.
Contracting out advantages:
- Company lacks spare human resources.
- System integratorSystem integratorA systems integrator is a person or company that specializes in bringing together component subsystems into a whole and ensuring that those subsystems function together, a practice known as System Integration...
s (contractors) tend to have more experience and expertise. They can design within tight specs and can handle complicated designs. - System integrators can provide guaranteed work as well as product support.
Signal routing
There are two types of switches typically used in switch matrices: CoaxialCoaxial
In geometry, coaxial means that two or more forms share a common axis; it is the three-dimensional linear analogue of concentric.Coaxial cable, as a common example, has a wire conductor in the centre a circumferential outer conductor and an insulating medium called the dielectric separating...
Electromechanical Switches and Solid State Switches, also known as electronic switch
Electronic switch
In electronics, an electronic switch is an electronic component or device that can switch an electrical circuit, interrupting the current or diverting it from one conductor to another....
es. Coaxial electromechanical switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
es can be further divided into two categories based on their architecture, latching relay and non-latching relay. Solid state switches come in three types: PIN diode
PIN diode
A PIN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts....
, FET
Fet
Fet is a municipality in Akershus county, Norway. It is part of the Romerike traditional region. The administrative centre of the municipality is the village of Fetsund.Fet was established as a municipality on 1 January 1838...
, and hybrid. The advantages of solid state switches over EM switches include they have much faster switching speed (at least 10,000 times faster), they have an almost infinite life, and they are very stable and repeatable. On the other hand, since solid state switches have non-linear portions over their frequency range their bandwidth is limited. Also, EM switches provide better insertion loss
Insertion loss
In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels ....
, VSWR, power handling, and isolation specifications. For these reasons EM switches are used much more often in switch matrix designs.
Example applications
Custom Switch Matrices are used extensively throughout test systems in the wireless and aerospace defense sectors for design verification and manufacturing test. They can range from the simple to the complex. An example of a simple design switch matrix application would be a 1:16 MUX configuration that routes 12 satellite TV feeds to a single spectrum analyzerSpectrum analyzer
A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals...
input that is used to perform signal integrity checks on the satellite feeds. Such a design would require 5 SP4T coaxial EM switches as well as interconnecting coax cable for the signal routing along with a mechanical infrastructure, power supply, and switch driver circuit to mount, power, and operate the switches.
An example of a more complex switch matrix is an application that is measuring jitter
Jitter
Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of...
on multiple high speed serial data buses. The switch matrix inputs the data bus signals then provides the proper switching and signal conditioning for the signals before feeding the signals to test and measurement instruments. This custom switch matrix employed 14 EM switches and a number of different signal conditioners including: power splitters, amplifiers, mixers, filters, and attenuators.
RF Switch Matrices are also used heavily in the Televison Broadcast market for the reception and re-broadcast of TV Channels. Typically a Cable TV Headend will contain a matrix to enable multiple dishes aligned to different satellites to be routed to a bank of receivers. The RF Switch Matrix allows channel changes to be made remotely without any interuptions.
Design challenges
There are six main challenges when designing a custom RF/Microwave Switch Matrix from beginning to end:- Mechanical Design: design of an electrically shielded enclosure or box, internal component mounting brackets, as well as component and cabling layout.
- RF/Microwave Design: RF/Microwave signal routing and signal conditioning design and testing. A calibration plan for the switch matrix would need to be developed to properly characterize the signal paths.
- Power and Control Hardware: The power supply and switch driver circuitry will need to be designed and developed.
- Software Control: A software driver will need to be developed to provide an interface between the control hardware and test system program.
- Documentation: The whole switch matrix design will have to be documented to support maintenance and possible future design leveraging.
- Servicing Plan: A servicing plan will need to be developed to ensure the life of the switch matrix lasts as long as the life of the test system.
Test equipment manufacturers offer instruments that provide a power supply
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
, driver circuitry, and software drivers that essentially saves a test system designer time and cost by eliminating two of the six switch matrix design challenges: power and control hardware design as well as software driver development. Many companies have introduced new product concepts that aid in custom switch matrix design. These new products offers test system designers a power supply
Power supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy to electrical energy...
, driver circuitry, and software drivers all wrapped together in a mainframe. The mainframe provides flexible mounting for switches and other components as well as blank front and rear panel that can be easily modified to fit a design need. These new products eliminates 3 of the 6 design challenges: mechanical design, power and control hardware design, and software driver development
External links
- Information on switching in a microwave test system for VXI Technologies
- Application note explaining the difference between "blocking" and "non-blocking" matrix switches from JFW
- Application notes understanding how an RF switch functions from Charter Engineering
- Application note explaining the effects of operating life and repeatability of switches in switch matrix from Agilent Technologies
- Application note discussing the various scale of switch matrix that is required in RF and microwave testing from Agilent Technologies