Dual frequency voltage controlled oscillator

A dual frequency band voltage controlled oscillator, comprising:

• a first and a second transistor with respective first and second bases, first and second collectors and first and second commonly AC and DC coupled emitters;
• the first and second bases are AC coupled to respective first and second resonant circuits, a feedback reactance is shared between an oscillator loop of each resonant circuit, the second base is biased at a predetermined bias voltage greater than a base-emitter junction voltage of the transistors;
• when the first base is biased at a voltage greater than the predetermined bias voltage of the second base, the first transistor turns on which causes the first resonant circuit to operate at a first frequency band and which drives the emitter of the second transistor such that a potential across the second base and emitter is less than the base-emitter junction voltage turning the second transistor and second resonant circuit off;
• and
• when the first base is biased at a voltage less than the base-emitter junction voltage of the transistors, the first transistor and first resonant circuit turn off, the second transistor being biased at the predetermined bias voltage turns on which causes the second resonant circuit to operate at a second frequency band.

A dual band radio communication device having a receiver and including a dual frequency band frequency synthesizer, comprising:

• a locked loop circuit and detector chosen from the group consisting of a phase locked loop with a phase detector, a frequency locked loop with a frequency detector and a delay locked loop with a delay detector;
• a reference oscillator providing a reference signal to a first input of the detector of the locked loop circuit, the detector providing a tuning signal for a voltage controlled oscillator;
• and
• a dual band voltage controlled oscillator, comprising:
• a first and a second transistor with respective first and second bases, the transistors having collectors and having commonly connected emitters;
• the first and second bases are coupled with respective first and second resonant circuits, the second base is biased at a predetermined bias voltage greater than a base-emitter junction voltage of the transistors;
• when the first base is biased at a voltage greater than the predetermined bias voltage of the second base, the first transistor turns on which causes the first resonant circuit to operate within a first frequency band and which drives the emitter of the second transistor such that a potential across the second base and emitter is less than the base-emitter junction voltage turning the second transistor and second resonant circuit off, a first frequency of the first resonant circuit is tunable within the first frequency band, responsive to the tuning signal of the detector, and is applied to a mixer and a second input of the detector;
• and
• when the first base is biased at a voltage less than the base-emitter junction voltage of the transistors, the first transistor and first resonant circuit turn off, the second transistor being biased at the predetermined bias voltage turns on which causes the second resonant circuit to operate at a second frequency within a second frequency band, the second frequency is responsive to the tuning signal of the detector and is applied to a mixer and a second input of the detector.