Controllable high-frequency attenuator
AssigneeNokia Mobile Phones Ltd.
InventorJouni I. Verronen
Life of this patent
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Abstract
The present invention decribes a high-frequency attenuator using PIN diodes, which is especially intended as power control means in a radio-telephone transmitter, and in which the input and output impedances remain constant as the attenuation is varied. The attenuator comprises a longitudinal branch between the input and the output port, having PIN diodes (D1, D2) attenuating the RF signal, transverse branches connected with the input and the output port, each comprising a quarter-wavelength transformer (C1, Z1, C2; C4, Z2, C5) viewed from the signal path and a PIN diode (D3, D4). The same control direct current passes via all the diodes. In spite of the variations of the resistance of the PIN diodes, the input and output impedances of the attenuator do not change owing to the quarter-wavelength transformer.
Claims8
A DC controllable, radio frequency (RF) attenuator having an input and an output and exhibiting substantially constant input and output impedances, respectively, over a range of RF attenuation values, said attenuator comprising:
- a signal transmission path between said input and output including series connected first PIN diode means and first capacitor means;
- a first transverse circuit comprising an impedance transformer and second PIN diode means connected between said input and an RF ground circuit;
- a second transverse circuit comprising an impedance transformer and third PIN diode means connected between said output and said RF ground circuit, said second and third PIN diode means thereby connected so as to be identically poled and to provide a DC current flow path including said first PIN diode means;
- and
- DC control current means connected across said first capacitor means for passing a DC control current through said first, second and third PIN diode means so as to alter the RF impedances of said PIN diode means, said impedance transformers reflecting to said signal transmission path opposite sense RF impedance changes from said second and third PIN diode means to RF impedance changes seen in said first PIN diode means.
Dependencies are inferred from the claim text.