Research On Wideband Small Stepping Oscillator Source Of Retro-directive Antenna System At 2.45GHz

Retro-directive antenna can track incoming signal quickly and automatically which relies on analog circuit completely.Phase conjugation scheme of retro-directive antenna can suppress multipath effect effectively and radiate the signal to the source both far and near field.Facing the current communication situation of increased information and promotion of transmission speed,develop twice RF frequency broadband small step local oscillator source for balanced structure heterodyne mixing circuit of wideband retro-directive antenna in 2.420 ~ 2.4835 GHz of ISM.Because of a nonzero initial phase in actual oscillator and requiring near field retro-direction in short-haul communications,promote the generalized phase conjugation principle and proved it's correctness in the conditions of non-plane wave deduced from the antenna beam reorientation delay condition and element relationship of retro-directive antenna array.End design a 4.5 ~ 5.3GHz larger selection range of voltage-controlled oscillator.LC voltage controlled oscillator consists of negative resistance network and resonant circuit.Design a negative resistance network according to the principle of negative resistance energy compensation and the S-parameter characteristic of microwave network,which contains FET active bias,feedback impedance,high frequency choke and output matching network.And design a broadband tuned LC resonant network using varactor diode and inductor in parallel.Add microstrip open stub feedback elements to the DC bias FET gate for improving the potential instability that required for the field effect transistor to oscillate.Determining a output load network based on the input impedance of the FET active loop,and design a wide-band Chebyshev low-pass matching circuit between the active and load networks for obtaining the maximum oscillation power of the circuit as the output is not 50 ? standard terminal.Design of varactor diode pairs of the reverse circuit makes the second harmonic in the resonant network is zero for harmonic reduction effect and circuit stabilization under the suitable varactor.In order to improve the spectral purity of the output signal,a parallel coupled microstrip bandpass filter circuit is added to the output of the oscillator after the oscillator is stable stabilizing.Coordinate and optimize the resonant network,negative resistance network and filter to obtain the linear output frequency of 4.5 ~ 5.3 GHz with the tuning sensitivity is about 112 MHz / V while the tuning voltage is 0.9 to 10 V.At the 4.9GHz output frequency,the phase noise is-104.8dBc / Hz@100kHz,-118.8dBc/Hz@1MHz,which meet the broadband low noise characteristics.In order to maintain the stability of the voltage controlled oscillator,add the voltage-controlled oscillator to the phase-locked loop and calculate the parameters of the loop filter and determine the system loop bandwidth of 1.25 MHz,open-loop phase margin of 51.567 through the simulation optimization.Test the phase-locked loop circuit and obtain the property of center frequency 4.9GHz that lock fast in 120 ?s.The phase-locked loop meets the wideband local oscillator requirements of retro-directive antenna with the property of stable and high precision.