Distributed digital attenuator

A digital attenuator circuit for attenuating RF signals, said attenuator circuit having an RF input port and an RF output port, comprising:

• first impedance means having a first terminal and a second terminal said first terminal of said first impedance means being coupled to said RF input port, said first impedance means having a first given resistive impedance;
• first active device means having a first terminal and a second terminal, said first terminal of said first active device means being coupled to said second terminal of said first impedance means, said first active device means having a first control terminal for receiving a first switching voltage causing said first active device means to switch between a first conducting state and a first nonconducting state;
• resistive means having a first terminal and a second terminal, said first terminal of said resistive means being coupled to said second terminal of said first impedance means and to said first terminal of said first active device means, said second terminal of said resistive means being coupled to said second terminal of said first active device means;
• second active device means having a first terminal and a second terminal, said first terminal of said second active device means being coupled to said second terminal of said first active device means and to said second terminal of said resistive means, said second terminal of said second active device means being coupled to a point of reference potential, said second active device means having a second control terminal for receiving a second switching voltage causing said second active device means to switch between a second conducting state and a second nonconducting state, said first active device means being switched on when said second active device means is switched off, and said first active device means being switched off when said second active device means is switched on, said second active device means having a second given resistive impedance in said second conducting state and a substantially higher resistive impedance in said second nonconducting state;
• and
• second impedance means having a first terminal and a second terminal, said first terminal of said second impedance means being coupled to said terminal of said first active device means, to said second terminal of said resistive means and to said first terminal of said second active device means, said second terminal of said second impedance means being coupled to said RF output port, said second impedance means having said first given resistive impedance, whereby said first given resistive impedance matches said second given resistive impedance thereby enabling said attenuator circuit to operate over a wide bandwidth range.

A digital attenuator circuit for attenuating RF signals, said attenuator circuit having an RF input port and an RF output port, comprising:

• first impedance means having a first terminal and a second terminal, said first terminal of said first impedance means being coupled to said RF input port, said first impedance means having a first given resistive impedance;
• first active device means having a first terminal and a second terminal, said first terminal of said first active device means being coupled to said second terminal of said first impedance means, said first active device means having a first control terminal for receiving a first switching voltage causing said first active device means to switch between a first conducting state and a first nonconducting state;
• first resistive means having a first terminal and a second terminal, said first terminal of said first resistive means being coupled to said second terminal of said first impedance means and to said first terminal of said first active device means, said second terminal of said first resistive means being coupled to said second terminal of said first active device means;
• second active device means having a first terminal and a second terminal, said first terminal of said second active device means being coupled to said second terminal of said first active device and to said second terminal of said first resistive means, said second terminal of said second active device means being coupled to a first point of reference potential, said second active device means having a second control terminal for receiving a second switching voltage causing said second active device means to switch between a second conducting state and a second nonconducting state, said second active device means having a second given resistive impedance in said second conducting state and a substantially higher resistive impedance in said second nonconducting state;
• second impedance means having a first terminal and a second terminal, said first terminal of said second impedance means being coupled to said second terminal of said first active device means, to said second terminal of said first resistive means and to said first terminal of said second active device means, said second impedance means having said first given resistive impedance;
• third active device means having a first terminal and a second terminal, said first terminal of said third active device means being coupled to said second terminal of said second impedance means and said second terminal of said third active device means being coupled to a second point of reference potential, said third active device means having a third control terminal for receiving a third switching voltage causing said third active device means to switch between said second conducting state and said second nonconducting state, said third active device means having said second given resistive impedance in said second conducting state and said substantially higher resistive impedance in said second nonconducting state;
• third impedance means having a first terminal and a second terminal, said first terminal of said third impedance means being coupled to said second terminal of said second impedance means and to said first terminal of said third active device means, said third impedance means having said first given resistive impedance;
• fourth active device means having a first terminal and a second terminal, said first terminal of said fourth active device means being coupled to said second terminal of said third impedance means and said second terminal of said fourth active device means being coupled to a third point of reference potential, said fourth active device means having a fourth control terminal for receiving a fourth switching voltage causing said fourth active device means to switch between said second conducting state and said second nonconducting state, said fourth active device means having said second given resistive impedance in said second conducting state and said substantially higher resistive impedance in said second nonconducting state;
• fifth active device means having a first terminal and a second terminal, said first terminal of said fifth active device means being coupled to said second terminal of said third impedance means and to said first terminal of said third active device means, said fifth active device means having a fifth control terminal for receiving a fifth switching voltage causing said fifth active device means to switch between said first conducting state and said first nonconducting state, said first and said fifth active device means being switched on when said second, said third and said fourth active device means are switched off, and said first and said fifth active device means being switched off when said second, said third and said fourth active device means are switched on;
• second resistive means having a first terminal and a second terminal, said first terminal of said second resistive means being coupled to said second terminal of said third impedance means, to said first terminal of said fifth active device means and to said first terminal of said fourth active device means, said second terminal of said second resistive means being coupled to said second terminal of said fifth active device means;
• and
• fourth impedance means having a first terminal and a second terminal, said first terminal of said fourth impedance means being coupled to said second terminal of said fifth active device means and to said second terminal of said second resistive means, said second terminal of said fourth impedance means being coupled to said RF output port, said fourth impedance means having said first given resistive impedance, whereby said first given resistive impedance matches said second given resistive impedance thereby enabling said attenuator circuit to operate over a wide bandwidth range.

A digital attenuator circuit for attenuating RF signals, said attenuator circuit comprising:

• an input terminal for receiving an input signal to be attenuated;
• an output terminal for outputting the attenuated output signal;
• impedance means extending between said input and output terminals, said impedance means comprising first and second transistors coupled in series between said terminals, each of said first and second transistors being controllable jointly to switch between a conducting state in which they define a low-loss through path between said input and output terminals and a non-conducting state;
• active device means coupled to said impedance means, said active device means being adapted to attenuate said input signal when said first and second transistors are in said non-conducting state and being controllable to switch between a non-conducting and a conducting state, wherein said attenuator circuit is at a state of maximum attenuation when said active device means is in said conducting state and said transistors are in said non-conducting state and is at a state of minimum attenuation when said active device means is in said non-conducting state and said transistors are in said conducting state.