Abstract The output electrode of a field effect transistor of a high-frequency input stage is connected to a capacitively coupled input (gate) electrode of the field effect transistor of a mixer stage through one of a pair of bifilarly wound coils provided on a ferrite core, while the second of these coils connects the same input of the mixer stage to the output of a local oscillator in such a way that two signal paths leading towards the mixer stage, respectively for the high-frequency signal and the oscillator signal, go through coupled coils in opposite winding directions. The result is that the path for signals in either direction between the local oscillator and the input stage are of much higher impedance than the paths for signals proceeding to the mixer stage respectively from the input stage and from the local oscillator.
A high-frequency amplifier-mixer stage for radio or television receivers having an input stage, a local oscillator and a mixer stage to which the outputs of said input stage and said oscillator are applied as inputs, and comprising the improvement which consists in that: first and second coils wound together bifilarly are used for coupling the outputs of said input stage and of said oscillator to the input of said mixer stage; an input terminal (4) of said mixer stage (2) is connected through said first coil (S 1 ) to an output terminal (5) of said input stage (1); said input terminal (4) of said mixer stage (2) is connected through said second coil (S 2 ) to an output terminal (6) of said oscillator (3); the respective signal paths from said output terminals (5,6) of said input stage (1) and said oscillator (3) to said input terminal (4) of said mixer stage through said first and second coils (S 1 , S 2 ) have opposed winding directions, and none of said terminals (4,5,6) is connected to ground or to a reference potential that is fixed with respect to ground potential.
Claim 2
Dependent Claim
192 words
A high-frequency amplifier-mixer stage for radio or television receivers having an input stage, a local oscillator and a mixer stage to which the outputs of said input stage and said oscillator are applied as inputs, and comprising the improvement which consists in that: first and second coils wound together bifilarly are used for coupling the outputs of said input stage and of said oscillator to the input of said mixer stage; an input terminal (4) of said mixer stage (2) is connected through said first coil (S 1 ) to an output terminal (5) of said input stage (1); said input terminal (4) of said mixer stage (2) is connected through said second coil (S 2 ) to an output terminal (6) of said oscillator (3); the respective signal paths from said output terminals (5,6) of said input stage (1) and said oscillator (3) to said input terminal (4) of said mixer stage through said first and second coils (S 1 , S 2 ) have opposed winding directions, and none of said terminals (4,5,6) is connected to ground or to a reference potential that is fixed with respect to ground potential.
Claim 3
Dependent Claim
29 words
A high-frequency amplifier-mixer stage as defined in claim 1 in which said first and second coils (S 1 , S 2 ) have the same number of winding turns.
Claim 4
Dependent Claim
31 words
A high-frequency amplifier-mixer stage as defined in claim 1 or claim 2 in which said first and second coils (S 1 , S 2 ) are wound on a ferrite core.