MESFET mixer circuit having a pulse doped structure
AssigneeSumitomo Electric Industries, Ltd.
InventorNobuo Shiga
Life of this patent
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Abstract
An FET mixer circuit having a stable input impedance uses two tandem-connected GaAs MESFET's (1) and (2) of pulse doped structure instead of a conventional MESFET or a HEMT, as an active device. A gate biasing point for the FET (1) is set around a pinch-off point of a mutual conductance, and a gate biasing point for the FET (2) is set in a region which assures non-change of a mutual conductance with respect to the increase of a gate voltage. Thus, a mixer circuit having a good isolation characteristic for an RF signal and a local oscillation signal and exhibits substantially no change in the input impedance is attained.
Claims7
A mixer circuit comprising:
- a first input terminal for receiving a local oscillation signal;
- a second input terminal for receiving an RF signal;
- a first GaAs MESFET having a gate electrode, a drain electrode, and a source electrode, said gate electrode being connected to said first input terminal;
- a second GaAs MESFET having a pulse doped structure, a gate electrode, a drain electrode, and a source electrode, said gate electrode being connected to said second input terminal, said drain electrode of said second MESFET being connected to said gate electrode of said first MESFET,
- a first bias voltage source connected to said gate electrode of said first MESFET;
- a second bias voltage source connected to said gate electrode of said second MESFET;
- an output terminal connected to said drain electrode of said first MESFET;
- wherein
- said second MESFET has a mutual conductance-gate voltage characteristic such that the mutual conductance of said second MESFET remains constant during a change in gate electrode voltage applied to said gate electrode of said second MESFET when a predetermined bias is applied by said second bias voltage source.
Dependencies are inferred from the claim text.