p-i-n diode attenuator with small phase shift

A computer-aided design technique for minimizing spurious phase shift in microstrip p-i-n diode attenuators is presented. At 9 GHz, a spurious phase shift of 0.17 degrees /dB attenuation has been realized at 15-dB attenuation. This is better than the previous reported value (H. Imai, 1974) of 1 degrees /dB attenuation at comparable operating frequencies and attenuations. The diode mounting location and the DC blocking chip capacitors on microstrip are important, among other parameters, to minimize the spurious phase shift.<
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