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T attenuator pad vs Pi attenuator pad for Power based RF attenuation

This page describes T attenuator pad vs Pi attenuator pad. It lists difference between these T and Pi RF attenuator pads. These pads are very useful in RF/Microwave circuit design. It mainly provides RF power attenuation. Various resistor values are pre-determines and mounted as per need of attenuation on the path. Mainly used for adjusting instantaneous power level at various points on the RF circuit path.

Frequency range and impedance value(50 Ohm or 75 Ohm) are used to determine right chip resistors for the RF circuit design. Both the Pi and T pads are used mainly in the design of RF transceiver or power amplifier circuit. Read design of RF frequency converter to understand the application of these RF attenuator pads.

Pi Attenuator Pad

Pi attenuator pad

R1=R2= Z ( K-1/K+1)

R3= 2 Z ( K / K2 - 1)

K is the impedance factor equal to Antilog(dB/10) or 10dB/10
Source impedance Zs= Load impedance ZL = Z

T Attenuator Pad

T attenuator pad

R1=R3=Z ((K+1)/(K-1))

R2= Z ((K2 -1 )/2K)

Manufacturers of chip resistors used for RF attenuator pads

The following are few of the popular manufacturers of rf attenuator.

Aeroflex- PCB mountable attenuator pads and chip components are available.
Website: www.aeroflex.com

RF Micro Devices-various types of attenuators viz. analog,digital and temperature controlled are available.
Website: www.rfmd.com

Anaren- Chip attenuators/terminations and SMD attenuators/terminations are available.
Website : www.anaren.com

JFW Industries, Connectorised RF attenuators of various types available.
Website: www.jfwindustries.com

EMC RF Labs , Ideal for RF thermopad purchase.
website: www.emc-rflabs.com

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T Attenuator resistance calculator
PI Attenuator resistance calculator

RF and Wireless Terminologies

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