Circuit Overview The circuit integrates two VCOs and a 2:1 multiplexer. Both are ring type, with VCO1 controlled by a network of nMOS transistors and VCO2 controlled by a pMOS network. The purpose of the VCOs is to generate oscillating signals at frequencies that can be adjusted based on a control voltage. Each VCO is designed to operate in a distinct frequency band, enabling the circuit to cover a wider range of frequencies.
Components VCO 1: Frequency Band: Designed to operate in the lower frequency band. Control Voltage Input (Vcntr 1): Receives a voltage that determines its oscillation frequency within the specified lower band. Output (F1): Provides the oscillating signal at the determined frequency.
VCO 2: Frequency Band: Designed to operate in the higher frequency band. Control Voltage Input (Vcntr 2): Receives a voltage that determines its oscillation frequency within the specified higher band. Output (F2): Provides the oscillating signal at the determined frequency.
2:1 Multiplexer (MUX): Inputs (F1 & F2): Takes the output signals from both VCOs as inputs. Select Line (S): Determines which VCO output to pass through to the MUX output. Output (Vout): Delivers the selected oscillating signal to the output of the circuit.
Operation VCO Operation: Both VCOs receive control voltages that set their oscillation frequencies within their respective bands. VCO 1 generates a signal in the lower frequency band. VCO 2 generates a signal in the higher frequency band.
Multiplexing: The 2:1 MUX has two input channels connected to the outputs of VCO 1 and VCO 2. The select line of the MUX is used to choose which VCO output to send to the MUX output. Based on the select signal, the MUX passes either the lower band signal from VCO 1 or the higher band signal from VCO 2 to the circuit's final output.
Applications This circuit can be used in systems where frequency agility is required, such as in communication systems, signal generators, and frequency synthesis. The dual-band operation provided by the two VCOs, combined with the switching capability of the MUX, allows for versatile frequency selection in a compact design.
This circuit design offers several advantages: It provides flexibility by covering a broader spectrum through two VCOs with different frequency ranges, ensures compactness by using a multiplexer to switch between the VCO outputs and thus reducing the need for additional components, and offers ease of control through manageable control voltages for the VCOs and select line for the multiplexer. Additionally, the design can be further optimized to meet specific requirements such as varying frequency ranges, control voltage ranges, and integration with other system components.