The general theory for oscillator and mixer design is applied to develop an X-band self-mixing oscillator antenna. The antenna uses a Gunn diode as the active device that provides the oscillations and self-mixing operations. The circuit uses a slotline ring resonator for frequency stabilization and can be modified to include a varactor diode for wide-band frequency tuning. The circuit performance is compared with theoretical results derived from simple transmission-line models. The radiation patterns of the self-mixing oscillator antenna are also compared with those measured from a similarly configured passive antenna. Since the radiated power also serves as the local oscillator (LO) frequency for the self-mixing operation, the circuit is useful as a half-duplex transceiver. When the self-mixing operation is not required, a single oscillator antenna can be used as a transmitter and several units can be assembled in a planar array for spatial powercombining applications.

An X-band self-mixing oscillator antenna for transceiver and spatial power-combining applications

The aim of the invention is to regulate the power of a transmit amplifier. To this end, parts of the power emitted by the antenna are received by a coupling element and are converted into a direct voltage value by a high-frequency detector. Said value is used for power regulation. The costly use of a directional coupler between the transmit amplifier and the antenna is no longer necessary.

Method and arrangement for regulating the power of a transmit amplifier

A wide bandwidth, high-gain and high directivity multi-layer patch antenna integrated with coupler and covered with metamaterial superstrate is proposed for frequency range of 10.8 to 12 GHz. The novel high level of integration of three different functions in one configuration is done in a straightforward design. It consists of a 50 ohm microstrip line coupled directly to the non-radiating edge of a patch antenna. This structure is covered by two layers of near zero refractive index metamaterial. The prototype of this configuration shows a flat coupling factor of 25 dB and a high isolation factor of 33 dB. The two layers of metamaterial superstrate enhanced the performance of the patch antenna-coupler. At the center frequency of 11.4 GHz, the gain of the patch antenna-coupler with metamaterial superstrate is improved by 8 dB to 13.4 dB and the return loss bandwidth is improved to more than 10%. Furthermore, the 3-dB beamwidth of the antenna is reduced by more than 70° to 30°.

Wideband high-gain multi-layer patch antenna-coupler with metamaterial superstrate for X-band applications

This paper presents a novel idea that the power is fed from the patch antenna coupler to form a five-element Chebyshev active antenna FET amplifying linear array. An equivalent lumped element circuit was developed to model the mutual coupling having good agreement with experiments. The power level coupled to the transmission line can be controlled by adjusting the length and the gap of the transmission line. The active patch-fed antenna coupler array has the advantages of a single input port, no power divider required, good and controllable radiation patterns, ease of bias, and compactness.

Novel active antenna amplifying arrays

A method and apparatus for controlling the power of a transmit amplifier wherein a portion of the power transmitted from the antenna is received by a coupling element and is converted via a radio-frequency detector to a DC voltage value which is used for power control, such that there is no longer any need for complex use of a directional coupler between the transmit amplifier and the antenna.

Method and apparatus for regulating the power of a transmit amplifier

A novel idea of controlling the coupled power from a patch antenna to a coupled transmission line at resonant frequency is developed. With FETs serving as active components, an appropriate gap and the coupled line's length adjusted for expected coupling, a compact five-element uniform linear array is designed. A thicker substrate giving stronger coupling is also presented. This design may find applications in active arrays and quasi-optical power combining.

http://ieeexplore.ieee.org/iel3/4924/13688/00630061.pdf

Active patch antennas integrated with FETs using coupled transmission lines

An analysis is developed for a patch antenna coupled to a transmission line. The coupling port is placed on the same side and the opposite side of the feeding end. A transmission line method is used to model the circuit. Experimental results are presented to verify the simulated results. Whether the coupling port is placed on the same side or the opposite side of the feeding end, the coupled power levels from the patch to the transmission line are almost the same. The coupling characteristics as a function of the gap and length variations are also identical for these two configurations.

Analysis of a patch antenna coupled to a transmission line

As power is fed into the transmission line of a line-fed antenna coupler, energy is coupled from the transmission line to the patch. Two resonant modes are excited at two different frequencies with orthogonal linear polarizations when the patch is rectangular. A compact 3/spl times/4 uniform linear array was developed to demonstrate the validity of the line-fed antenna coupler in a horizontal mode.

Line-fed antenna coupler arrays

As power is fed into the transmission line of the line-fed antenna coupler, energy is coupled from the transmission line to the patch. Two resonant modes are excited at two different frequencies with orthogonal linear polarizations if the patch is rectangular. Theoretical analysis with experimental verification has been conducted to study the characteristics of this configuration. The antenna can transmit and receive two independent orthogonal, and linear polarized signals.

Yao-Chou Yang

Papers

Active patch antennas integrated with FETs using coupled transmission lines

Analysis of a patch antenna coupled to a transmission line

Line-fed antenna coupler arrays

Analysis of line-fed antenna coupler