SWITCH FILTERS

Microphase is an unquestioned leader in the area of microwave Switch Filters. Microphase offers a variety of Switch Filters, which are custom designed assemblies of Microphase filters, solid-state switches and switch drivers optimally integrated to achieve a specific requirement. Achieving optimal performance requires a rigorous design tradeoff in individual filter switch and driver designs combined with careful integration and tuning. The ability to tune and match the constituent parts in an assembly offers improved overall performance with significant size and cost benefits. Microphase presently has produced over 125 switch filter assemblies in the 10MHz to 26 GHz frequency range.

Most switch filter assemblies feature one input port and one output port with two or more alternately selectable filter paths (thru path optional). A low loss, well matched response is achieved for the selected filter pass band with a reflective out-of-band response maintaining high isolation and rejection. Optionally, multiple input or outputs may be specified to alternately route the main signal, combine multiple signals or inject BIT signals for testing purposes.

Switch multiplexers are typically used where the slight increase in insertion loss of a solid-state switch is unacceptable. By replacing the input switch with a multiplexer, lower overall loss and reduced switching time is achieved. Because the input signal is always present at the output switch, the group delay of the filter will not add to the selected band transition time, an advantage in fast switching synthesizer applications.

Virtually any type of Microphase filter or multiplexer can be integrated into a switch filter assembly. Lumped element low pass, high pass or band pass filters are typically used at lower frequencies where size is a primary consideration. At higher frequencies, Combline bandpass filters are used where their reduced height and ease of tuning offer performance advantages.

Our experienced engineers and designers possess the knowledge and experience to aid in the design and manufacturing to complete projects cost effectively. We can provide you with timely prototypes as well as full production runs.

Frequency range: 10MHz to 26GHz

PIN diode and GaAs FET switches are used depending upon the specific switching requirements.
Monolithic GaAs switches use 3 terminal FET transistors to achieve extremely fast switching speeds (< 10 nsec.), very low bias power (mW) and small size. Unfortunately they suffer from poor insertion loss and isolation that degrades rapidly with frequency. The poor isolation and increased insertion loss generally limit their use to frequencies less than 6 GHz. PIN diodes are two terminal devices with impedance that is determined by the bias current flowing through them. Forward current on the order of 10mA will produce a series resistance of less than 5 Ohms and a reverse voltage will produce a negligible leakage current and a series resistance greater than 5K Ohms with a parasitic capacitance generally less than 1 pf. A PIN diode in the low impedance state is used in series to conduct RF with low loss or used in shunt to short our RF with high isolation. Conversely, a PIN diode reverse biased to high impedance is used in series to block RF with high isolation or used in shunt to pass RF with low loss. Frequency range 10MHz to 26GHz.

All series diode switches are small, multiple throw broadband, multi octave designs with a simplified driver but suffer from slow speed (1 µsec.), moderate power handling, and poor isolation at higher frequencies.

All shut diode designs are larger, generally restricted to SP2T octave band designs but switch fast (25 nsec.), handle high power and feature low insertion loss at high frequencies.

The most common design is a series, shunt switch to achieve a multiple throw, broadband, fast switching and good isolation with moderate insertion loss and power handling capabilities.

Microphase integral drivers are designed to provide the proper control element bias dependent upon input TTL control signals. + 5 volts and – 5, –12 or –15 volts are standard bias voltages with the current draw determined by the specific assembly requirements, Normally, BCD parallel line TTL inputs are internally decoded to select the desire switch path. Alternately a single line for each switch path may be specified.

Switch Filters RF and Microwave Switch Filters are available as modifications to over 125 existing Microphase designs or in customer specified configurations. They provide reliable high performance, multi-throw, multi-octave switch filtering in compact packages. Most Switch filters feature one input and one output, with two or more selectable filter paths. However, multiple inputs and outputs may be specified to alternately route the signal, or to inject BIT signals. The integrated switches are PIN diode or GaAs FET designs with internal drivers controlled through TTL compatible inputs.