Data Sheet

ADGM1004

Rev. D | Page 27 of 32

APPLICATIONS INFORMATION

SWITCHABLE RF ATTENUATOR

RF attenuator networks are commonly used in RF instrumentation

equipment, such as vector network analyzers, spectrum analyzers,

and signal generators. Routing RF signals through an attenuator

can enable the equipment to accept higher power signals and,

therefore, increase the dynamic range of the instrument. In

RF attenuation applications like the vector network analyzers,

spectrum analyzers, and signal generators, maintaining the

bandwidth of the signal after the signal passes through the

network is critical. Any degradation of the signal reduces the

performance of the equipment. Therefore, the RF characteristics

of the switches used for routing are an integral part of the quality

of an attenuator network.

The ADGM1004 MEMS switch with low flat insertion loss, wide

RF bandwidth, and high reliability is suited for use as a switchable

RF attenuator. The ADGM1004, as an SP4T switch, also brings

added flexibility. Figure 50 shows an example attenuation

network configuration using two ADGM1004 switches and

three different attenuators. The fourth channel of the switches is

used as a nonattenuated route in Figure 50.

15dB

10dB

I/O

ADGM1004

5dB

I/O

ADGM1004

Figure 50. Switching RF Attenuators Using Two ADGM1004 MEMS Switches

RECONFIGURABLE RF FILTER

A reconfigurable RF filter is advantageous in many RF front-

end applications. A reconfigurable RF filter provides more saved

space. As space becomes more constrained in applications, the

option to have an economical reconfigurable RF filter instead of

individual frequency dependent filters is preferred.

The ADGM1004 low flat insertion loss, wide RF bandwidth,

low parasitic, low capacitance, and high linearity are required to

turn on the lump components (capacitor and inductor), which

make the MEMS switch suited for reconfigurable filter application.

In applications such as wireless communications or mobile radios,

the number of bands and/or modes constantly increases. A

reconfigurable RF filter allows more bands and/or modes to be

covered using the same components.

Figure 51 shows an example of a reconfigurable band-pass filter.

The topology shown is of a generalized, two section, inductively

coupled, single-ended band-pass filter, nominally centered on a

400 MHz ultrahigh frequency (UHF) band. The MEMS switches

are positioned in series with each shunt inductor.

The function of the switches includes or omits a shunt inductor

from the circuit. Changing the shunt inductor value affects the

bandwidth and center frequency of the filter. Using inductance

values from 15 nH to 30 nH significantly alters the bandwidth

and center frequency, allowing the filter to dynamically configure

to operate in the UHF bands or very high frequency (VHF)

bands while preserving the 50 Ω match on the input and output

switch makes the switch an ideal choice for this application. The

quality factor of the shunt inductor. The large bandwidth enables

higher frequency band-pass filters.

INPUT

OUTPUT

GND

18nH

22nH

50Ω

13pF

13pF

30nH

24nH

15nH

50Ω

24nH

15nH

18nH

30nH

Figure 51. Reconfigurable Band-Pass Filter Achieved Using Two ADGM1004 MEMS Switches