Circularly polarized single-fed wide-band microstrip patch

For more than 25 years, the circularly polarized single-fed microstrip patch was considered to be extremely narrow-band. The reported performances are almost exclusively related to single patches printed on a dielectric substrate, which partially explains the frequency characteristics. The antenna proposed is a variation of the "almost square" patch and exhibits measured axial radio of less than 2.5 dB over a 13% bandwidth. The antenna was designed for wireless applications.     

Compact active integrated antenna with transistor oscillator andline impedance transformer

A novel oscillating antenna is realised by integrating a transistor oscillator and a line impedance transformer inside a rectangular opening in a rectangular patch antenna. This active antenna exhibits stable operation and a clean spectrum. The measured copolarisation radiation patterns are not affected by the modification of the patch while the cross-polarisation levels are low     

Stacked shorted patch antenna with tilted parasitic radiator

A new compact but wideband patch antenna is presented. Compact dimensions are obtained by using a shorted patch. The antenna bandwidth is increased by using a stacked patch configuration. Further increase in bandwidth is obtained by tilting the parasitic patch. The antenna prototype is fabricated and its input impedance and radiation patterns are measured     

Modified rectangular patches for self-oscillating active-antennaapplications

Two modifications to a rectangular-patch antenna, suitable for the integration of active devices, are presented. In the first modification, the impedance inverter was placed in the rectangular opening formed by removing the central part of the patch. This modification allows optimal matching of the active device by changing the position, width, and length of the impedance-line transformer. An oscillating antenna, using this modified patch and a Gunn diode, showed a high EIRP, higher spectral purity, and substantially lower cross-polarization levels, in comparison with the reference active antenna with an unmodified patch. Because of the higher overall Q, this modification is recommended for active-antenna applications with active devices that have a narrower negative-resistance bandwidth. In the second modification, an active device (Gunn diode) was integrated directly into a rectangular opening inside the patch, without the use of a line transformer. This reduced the overall Q of the antenna, thus allowing wide-band frequency tuning by changing the bias voltage. A clear spectrum, with no spurious components of the free-running oscillating antenna, was observed. Radiation patterns in the E and H planes were measured. Low levels of cross-polarization, as for the first modification, were obtained. Injection-locking properties were investigated throughout the tuning range. A relatively wide locking range, with a good locking gain, was achieved. Such a miniaturized wide-band VCO antenna is applicable for integration in injection-locked active arrays, and spatial power combiners     

Circular active integrated antenna with push-pull oscillator

A new oscillating circular patch antenna with two bipolar transistors operating in push-pull mode is presented. By using a circular instead of a rectangular patch the stability of the operating frequency is increased and second-harmonic radiated power is decreased. High radiated power and very linear frequency tuning are observed. Radiation patterns show no degradation due to patch modifications.     

Integrated push-pull oscillating antenna

A new integrated self-oscillating patch antenna is presented. Two bipolar transistors, operating in push-pull mode, are embedded in a rectangular opening inside a rectangular patch in order to increase the power radiated by the antenna. Measurements show a high radiated power and linear frequency change with bias voltage. The radiation patterns of the patch are not affected by the introduced modifications