Local oscillator noise rejection circuit

专利名称：Local oscillator noise rejection circuit发明人：JOHN PETER ORR申请号：AU5771096申请日：19960517公开号：AU5771096A公开日：19961129

摘要：PCT No. PCT/GB96/01188 Sec. 371 Date May 4, 1998 Sec. 102(e) Date May 4,1998 PCT Filed May 17, 1996 PCT Pub. No. WO96/37041 PCT Pub. Date Nov. 21, 1996Alocal oscillator noise rejection circuit is described which has a resistance between theoutput of an MES FET/HEMT and ground. This resistance has the effect of introducing aself-biasing arrangement to the oscillator circuit which means that when there is anyincrease in current through the MES PET/HEMT device, the voltage drop across theresistance also increases. Since the gate is tied to ground via a low resistance (51 OMEGA) this leads to an increased negative gate to source voltage which causes the device to\"pinch-off\" slightly which, in turn, gives a reduction in the current level through the device.This arrangement therefore has the effect of reducing any current surges within thedevice and produces an improvement in phase noise. In a preferred arrangement a 30Ohm resistor is located between the source of the FET/HEMT and ground, the resistorbeing located in series within the printed circuit inductor and the output line. With theaforementioned modified circuit, an improvement in the phase noise performance hasbeen measured from the standard circuit which gave a figure of - dBc. At 10 KHz. Aftermodification using the above mentioned circuit a figure of -76 dBc. At 10 KHz. wasobtained which is approximately a 16 times improvement.

申请人：CAMBRIDGE INDUSTRIES LIMITED

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