REV. A

ADG901/ADG902

–9–

APPLICATIONS

The ADG901/ADG902 are ideal solutions for low power, high

frequency applications. The low insertion loss, high isolation

between ports, low distortion, and low current consumption of

these parts make them excellent solutions for many high frequency

switching applications.

Applications include switching between high frequency filters,

ASK generator, and FSK generator.

Absorptive vs. Reflective Switches

The ADG901 is an absorptive (matched) switch with 50

Ω termi-

nated shunt legs, and the ADG902 is a reflective switch with 0

Ω

terminated shunts to ground. The ADG901 absorptive switch

has a good VSWR on each port, regardless of the switch mode.

An absorptive switch should be used when there is a need for a

good VSWR that is looking into the port but not passing the

through signal to the common port. The ADG901 is therefore

ideal for applications that require minimum reflections back to

the RF source. It also ensures that the maximum power is trans-

ferred to the load.

The ADG902 reflective switch is suitable for applications where

high off port VSWR does not matter and the switch has some

other desired performance feature. It can be used in many appli-

cations, including high speed filter selection. In most cases, an

absorptive switch can be used instead of a reflective switch, but

not vice versa.

ADG9xx EVALUATION BOARD

The ADG9xx evaluation board allows designers to evaluate the

high performance wideband switches with a minimum of effort.

To prove that these devices meet user requirements, the user

requires only a power supply and a network analyzer along with

the evaluation board. An application note is available with the

evaluation board and provides complete information on operating

the evaluation board.

The RF1 port (see Figure 3) is connected through a 50

Ω trans-

mission line to the top left SMA connector J1. RF2 is connected

through a 50

Ω transmission line to the top SMA connector J2.

J3 is connected to GND. A through transmission line connects

J4 and J5 and this transmission line is used to estimate the loss

of the PCB over the environmental conditions being evaluated.

The board is constructed of a 4-layer, FR4 material with a dielec-

tric constant of 4.3 and an overall thickness of 0.062 inches. Two

ground layers with grounded planes provide ground for the RF

transmission lines. The transmission lines were designed using a

coplanar waveguide with ground plane model using a trace width

of 0.052 inches, clearance to ground plane of 0.030 inches,

dielectric thickness of 0.029 inches, and a metal thickness of

0.014 inches.

Figure 3. ADG9xx Evaluation Board Top View