Spectrum Microwave’s high performance Switched Multiplexers should form the heart of most Self Adaptive Channelized Receivers. These Switched Multiplexers are realized by power splitting the broadband input equally between two filter banks. Each filter bank utilizes multiplexed, switched bandpass channels forming "odd" and "even" channels. The outputs are recombined in a resistive combiner.
Switched Multiplexers
Multichannel Adaptive Filter
Broad bandwidth
High Isolation
Fast Switching Speed
Low Ripple
Custom Configurations Available
Model FSM6420-1 Specifications
Frequency Range (GHz)
2.0 to 6.0 GHz
Number of Channels
16
Nominal Bandwidth
250 MHz
Insertion Loss
20 dB
Insertion Loss Ripple
4 dB
VSWR, max
2.0:1
Rejection at Adjacent Band Center
48 dBc
Isolation
70 dB
Switching Speed
100 nsec
Power
2 watts maximum
Size
5.2” x 4.0” x 1.0”
Temperature Range
-20ºC to +80º C
A switched multiplexer is a two port adaptive filtering device whose filtering characteristics may be electronically controlled to suit the operational environment. A typical application may be to precede an IFM to selectively reduce the incident signal spectrum.
Product Specifications
Spectrum Microwave Switched Multiplexers split the input frequency band into a number of channels, each of which may be switched into a bandpass or bandstop state. For a device comprising "n" channels it is therefore possible to have 2n switched states. This capability allows the device to be instantaneously configured as a tunable band stop filter with single or multiple bandstop channels, or conversely as a tunable bandpass or multiple bandpass filter.
Splitting the full frequency in this manner allows the channel bandwidths to be designed to achieve the correct overlap at the adjacent band edges to ensure recombined amplitude and phase characteristics. Spectrum Microwave has developed a technique for realizing the filter banks which permit many channels to be multiplexed with no channel interactions and giving uniform channel characteristics.
Additional Information
The filter banks comprise a cascade of pseudo-complimentary diplexers multiplexed along a lossy manifold. This structure ensures that all the power on the manifold is delivered to each channel filter while preserving a broadband match on the manifold.
The channelizing network formed is connected to a similar output network through custom non-reflective GaAs FET or PIN diode switches which also incorporate an adjustable attenuator network. The non-reflective switching ensures that the multiplexer match is maintained whatever the switch state and allows the energy in the filter structure to quickly dissipate in the "off" state. The adjustable attenuator allows the amplitude to be equalized over all channels.
To ensure that the overall recombined performance is acceptable under all environmental conditions, the bandedge amplitude and phase characteristics of each filter must exhibit slowly varying functions of frequency. A proprietary "reduced sensitivity" filter prototype has been developed to yield flat amplitude and group delay without sacrificing selectivity.
Devices using this prototype have been produced with passband amplitude ripple of less than 3 dB over full military airborne temperature range with up to 32 channels selected.
Switched multiplexers are essential building blocks in wideband receivers which are expected to operate in dense signal environments.
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