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Phase Shifters and Switches
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Ferrite Phase Shifters

COM DEV International is Europe's leading supplier of Ferrite Phase Shifters and can integrate our designs for use within a variety of Phased Array Antenna configurations.  Key markets are defence radars and satellite communication.

Our product range includes designs covering the frequency range of S-Band to Ka-Band. Key features include Integrated Electronic Drivers, Built-In Test Equipment (BITE), Differential and Insertion Phase Control and Transmit/Receive Operation.

Types of phase shifter offered includes toroidal, dual-mode and switched line. 

Key Features

  • phase accuracy
  • power handling
  • switching time (tens of microseconds)
  • temperature stability
  • reliability 

Ferrite Switches

 1.       INTRODUCTION TO FERRITE SWITCHES

COM DEV International’s range of toroidal and latching ferrite switches includes many of the key features that are found within our ferrite phase shifters. Designs are currently available with 2 or more port configurations and can offer switching speeds of between 0.5 to 50 microseconds, depending on frequency and configuration.

Ferrite switches are generally used for applications with power levels in excess of the capability of PIN diode switches. The combination of low insertion loss, high power handling and fast switching is unique to ferrite switches. Typical applications for these components include radar systems where fast switching between antennae is required, autotrack systems, beam forming networks, and satellite redundancy switching.

Functionality which can be added to our switches includes power splitting, polarisation and cascading of individual elements to create multi-way switch matrices. 

2.       SWITCHING OPTIONS

COM DEV International manufactures two distinct types of latching ferrite switch:

  • Differential phase shift switch
  • Latching junction circulator switch

The document linked below was written by COM DEV International technical staff in 2006, when COM DEV International was a part of Thales, and distributed in the 'Military Microwaves' supplement of the Microwave Journal.

Ka-Band_Switches.pdf

2.1        Differential Phase Shift Switch 

The differential phase shift switch is used for applications with very high peak and average power levels (tens to hundreds of kilowatts of peak power, with hundreds to thousands of watts of average power).

This type of switch has a number of different forms, but can be generally described as a number of ferrite phase shifters sandwiched between fixed phase butler matrix elements (usually waveguide tees and couplers). The simplest toroidal ferrite switch is the SPDT.

A schematic of the circuit for an SPDT differential phase shift switch is shown below:

 

 It comprises dual 90° toroidal ferrite phase shifters located between a 4-port waveguide tee and a 3dB hybrid waveguide coupler. A high power load is generally used to terminate port P3 above for an SPDT application.

The tee splits incident power at port P1 into two signals with equal phase and amplitude. The phase shifters apply a +90° or -90° relative phase shift to the two signals, which are recombined in the coupler to one or other of the two output ports. In the reverse direction (power incident at port P2 or P4) the relative phase shift is reversed compared to the forward direction (due to the non-reciprocal nature of the toroidal ferrite phase shifters) and the switch demonstrates non-reciprocal behaviour. Thus, if the switch is set to give low loss from P1 to P2, there will be isolation from P2 to P1 and low insertion loss from P4 to P1. If power is routed from P1 to an antenna at P2, any power reflected from the antenna will be routed to the high power load at port P3.

The toroids are magnetised by sending a well-controlled current pulse through wires that run along the inside of the ferrite toroids. The ferrite is sensitive to changes in temperature so the driver incorporates a temperature compensation circuit that adjusts the current pulses to maintain the required 90° differential phase over the operating temperature range. The switch is a latched device that does not require a holding current other than the quiescent current draw from the switch driver electronics.

Two examples from COM DEV International’s range of differential phase shift switches are shown below.

 

Ka-Band SPDT Differential Phase Shift Switch

  • Power handling=1400W peak, 150W average
  • Isolation = 30dB (5% bandwidth)
  • Insertion loss = 0.6dB
  • Switching time = 2µs

  

C-Band SP4T Differential Phase Shift Switch

M301A_-_C-Band_SP4T_Switch.pdf

  • Power handling = 60kW peak, 1000W average
  • Isolation >20dB (10% bandwidth)
  • Insertion loss <1.1dB
  • Switching time < 5µs
  • Reciprocal operation (Tx/Rx without switching)

2.2        Latching Junction Circulator Switch

 The latching junction circulator switch is used for applications where the power level is lower than that requiring a differential phase shift switch, but still too high for a PIN diode switch (kilowatts of peak power and tens of watts of average power). The latching circulator switch gives lower insertion loss and is substantially smaller than the differential phase shift switch.

This switch is essentially a three-port ferrite circulator in which the direction of circulation can be switched by application of current pulses through wires threading the Y-shaped toroidal ferrite resonator.

                                             

A single latching junction circulator can give approximately 0.15dB insertion loss and 20dB return loss and isolation over a 5% to 10% bandwidth.

2.2.1  Circulator Switch Configuration Options

As there is no inherent isolation between output ports (signals entering port O/P1 are circulated directly to port O/P2, or vice versa), isolators or more switches are often added to provide additional isolation function. Some options, other then the simple switch above, are given below:

 

 Latching junction switch with isolators at outputs

The fixed field isolators buffer the outputs so that signals entering ports O/P1 or O/P2 are absorbed in the internal loads and good output to output isolation is achieved. This type of switch can be used for uni-directional operation only

 

 Latching triple junction switch

The triple junction switch provides a higher level of isolation to the unselected port and provides a good level of isolation from selected output to unselected output, while allowing for two-way operation. The drawbacks are increased cost and size/weight  

Other more complex configurations are possible, which give higher isolation or more output ports. Waveguide to coaxial transitions can be integrated into the switch metalwork to give coaxial ports with minimal increase in size and weight.

 2.2.2      Latching Circulator Switch Examples

 Two examples of COM DEV International’s latching junction circulator products are shown below.

  

Ka-Band SP3T Switch

  • 5 latching junction circulators
  • Power Handling 1kW peak, 30W average
  • Insertion loss 0.3dB/junction
  • Isolation 20dB/junction

 

   

X-Band SP3T Switch

M308A_-_X-Band_SP3T_Latching_Junction_Switch.pdf

  • 2 latching junction ciculators
  • isolators
  • waveguide to coax transitions  

3.       SWITCH DRIVERS

Both switch types described above are latched devices – the ferrite material does not require a holding current to maintain its magnetic state – and therefore have low power consumption. The drivers deliver short current pulses (from < 1µs for a Ka-band latching junction circulator switch to around 10µs for an S-band differential phase shift switch) of around 2A to 20A to latch the ferrite material to the required magnetic state. Filtering is used on the driver board so that the input supply sees only minimal ripple on the supply current.

COM DEV International can design driver circuits to suit most customer requirements:

  • Supply voltage: typically +15 to +28V
  • Switch control: TTL, RS-422/485, or other
  • Switching rate: up to 30kHz
  • Power consumption: Typically 0.15W quiescent, 0.2W switching power per kHz of switching rate for single latching junction circulator at Ka-band
  • Driver mechanics: Integrated into switch for larger parts, remote with shielded interconnect for smaller parts

Drivers can be provided to control multiple switches in order to minimise size and mass.

 4.       SWITCHES FOR SPACE APPLICATIONS

Ka-Band latching circulator switches are well suited to space applications due to their high reliability, small mass and size, and low power consumption.

The diagram below shows representative dimensions for a single-junction Ka-band latching circulator.

  

 The switch can be supplied with driver module or without, allowing the customer the flexibility to optimise the system configuration, which can involve a large number of switches and can be simplified by using a driver module which controls a number of switches. COM DEV Internationalcould also supply such a driver module.

 

 

COM DEV International, Lochend Industrial Estate, Newbridge, Edinburgh, EH28 8PL, Scotland
Tel: 0131 333 2000 | Fax: 0131 333 3607 | COM DEV Europe Limited Registered England and Wales Company Number: 1863723