Direct conversion receiver with active integrated antenna

This paper describes numerical simulation, fabrication and experimental measurement of a compact miniature integrated antenna using direct conversion detection at 2.4 GHz. In this receiver design, Agilent's ADS software using momentum simulation and circuit simulation is employed to analyze the entire structure. Microstrip dipole antenna is integrated with 90deg hybrid coupler, oscillator and diodes for direct conversion or zero-IF detection is presented here. Microstrip dipole antenna that is presented here has a wide bandwidth up to 23.85 % bandwidth. The 90deg hybrid coupler can act as a phase shifter to provide the necessary 90deg characteristics to operate with I and Q signal for direct conversions. Two Schottky diodes (HSMS 8101) are mounted onto each of two coupler's output port to act as a mixer. One pin of the diodes is connected to the edge of output port and the other pin is grounded via a small hole to ground plane. One kHz sinusoidal signal act as a baseband has been generated and modulated using signal generator. The demodulated signal is detected using direct conversion receiver circuit and the baseband signal at the output ports is successfully detected using oscilloscope