Programmable RF attenuator used as Variable attenuator
This page covers programmable RF attenuator. This variable attenuator is useful for varying the attenuation. There are fixed RF attenuator chips available for various frequency ranges. These devices provide fixed value of attenuation in the RF signal path. Based on 1dB compression points of the devices (mixer, amplifier) in the RF signal chain appropriate values (3dB, 6dB) of these attenuator devices are used.
There are places where we need variable attenuation, for this purpose variable attenuator is needed. The typically applications are ATE(Automated Test Equipments), manual testing and more. There are two main types of variable attenuators viz. digital and analog. Also based on application of use connectorized or connectorless attenuators are employed.
The fig-1 depicts digital programmable RF attenuator. As shown in the figure, the device is digitally controlled either using RS232 or TTL controlled.
This device can be easily controlled using microcontroller or processor. The different bits writtern to digital lines will set different values of attenuation.
The device RUDAT-6000-110 from Minicircuits provide attenuation upto 110 dB with frequency range extending upto 6 GHz. This programmable RF attenuator has step size of 0.25dB. The device can be USB or RS232 controlled. The attenuation accuracy varies based on the frequency range from +/-0.15 to +/-0.80 dB. VSWR supported also varies based on different frequency ranges. Typically for frequency range between 4000 to 6000 MHz, VSWR is 1.30:1 for attenuation settings from 0 to 20 dB. VSWR is 1.15:1 for attenuation in the range from 20.25 dB to 110.00 dB.
The fig-2 depicts analog variable attenuator. As shown in the figure, the device attenuation is varied based on different analog voltage at its control pin. This concept is employed in rotary type of RF variable attenuator.DC - 8 Analog VVA 1.5 0 to 32 10 0 to -3V MS8G
The device HMC346MS8G from Hittite Microwave is a voltage variable attenuator.
Following are the features of the device.
• Frequency range: DC to 8 GHz
• Attenuation Range: 0 to 32 dB
• IIP3: 10 dBm
• Control voltage: 0 to -3V
• Loss: 1.5 dB
RF Variable attenuator manufacturers
Following are popular variable attenuator manufacturers.
• Hittite Microwave
• JFW Industries
• Maxim Integrated
• Analog Devices
• API technologies corp.