Elena Abdo-Sánchez

Planar Broadband Slot Radiating Element Based on Microstrip-Slot Coupling for Series-fed Arrays

A novel planar slot radiating element with applications in series-fed arrays and significant bandwidth enhancement is presented in this communication. The structure is based on the microstrip-slotline coupling and simply consists of a microstrip-fed slot with a symmetrically-arranged strip conductor superimposed onto it. The broad impedance bandwidth (up to 16 GHz) lies in the resulting all-pass section that the strip and the slot make up. A theoretical study of the structure in terms of even and odd modes as well as a straightforward equivalent circuit are provided, which offer the required analytical tools to state the design methodology. Experimental and simulated results corroborate that the strip acts as a mere matching element that does not practically alter the slot radiation characteristics.

A Novel Planar Log-Periodic Array Based on the Wideband Complementary Strip-Slot Element

A novel microstrip log-periodic array based on the broadly-matched complementary strip-slot radiating element is proposed. The array consists of microstrip-fed log-periodically-scaled slots on the ground plane and their complementary stubs on the microstrip layer. Since the radiating element is not resonant, the analysis differs from the previously reported log-periodic arrays. Low scale factor (τ) with high radiation efficiency is possible, since the element radiation efficiency is not resonant and the relative spacing (σ) does not have to be selected for good matching, because the element is intrinsically matched. A design example with τ = 0.909, σ = 0.17 and 15 elements has been analyzed. The achieved bandwidth goes from 2.7 to 8.7 GHz, with a radiation efficiency and a gain of better than 85% and 5 dB, respectively. Moreover, the antenna can be terminated in an open circuit without affecting its performance. Simulated and experimental results show that the radiation pattern is stable over frequency. A method for computing the radiation pattern using equivalent circuits as well as results with a reflector plane for cancelling the beam in one half-space are also included. Due to the good performance, simplicity and low cost, this antenna can be suitable for broadband applications.

Electronically Steerable and Fixed-Beam Frequency-Tunable Planar Traveling-Wave Antenna

The design of an electronically steerable wideband planar traveling-wave antenna is presented. The proposed antenna has a very simple structure based on a microstrip line loaded with several radiating elements and phase shifters between them. The phase shifters are based on tunable capacitances, in order to perform a continuous phase shift between the radiating elements and control the main beam direction. The radiating elements are complementary strip slots that have a very broad impedance bandwidth, thus allowing the antenna to have two different modes of operation: maintaining the main lobe direction over a significant bandwidth, 1.71-2.17 GHz, and performing a main beam scanning over this bandwidth with a maximum angle range of -45° to 45° at 2 GHz.

On the Radiation Properties of the Complementary Strip-Slot Element

The complementary strip-slot radiating element is a microstrip-fed slot modified by introducing its complementary stub on the layer of the microstrip. Previous works have shown that the introduction of the stub into the conventional slot results in an ultra broad impedance bandwidth and have provided a lattice-network equivalent circuit for its precise modeling. In this contribution, an interesting property of the symmetric lattice networks is highlighted and used to illustrate why the complementary strip-slot radiates as the conventional microstrip-fed slot, thus corroborating the conclusions of previous works based on empirical results.

Planar multiband sequentially rotated array with polarisation agility based on the complementary strip-slot element

A novel planar travelling-wave ring array with polarisation agility is introduced. The array is built by applying the sequential rotation technique with the complementary strip-slot element. This element is a conventional microstrip series-fed slot with the special feature of very broad impedance bandwidth thanks to the strip superimposed into it on the microstrip layer. The feeding of the array elements and the required phase shift between them are provided by a ring-shaped microstrip line, which is terminated in two ports. Vertical linear polarisation, horizontal linear polarisation, right-handed circular polarisation and left-handed circular polarisation can be generated with this very simple planar structure, just by controlling the phase and amplitude of the excitation at the two ports. Moreover, thanks to the wide impedance bandwidth of the element, multiband behaviour is achievable. A design example that operates at three different bands (centred around 6, 9 and 12 GHz) is analysed, which presents very good matching ( dB), polarisation purity and broadside radiation pattern.

A self-diplexing dual-band planar array for GNSS applications

A planar dual-band sequentially-rotated array is proposed to cover the radionavigation bands at 1.19 and 1.57 GHz. The antenna consists of a two-port ring microstrip line that series feeds four radiating elements. The basic radiator is the so-called complementary strip-slot, a microstrip-fed slot that has its complementary stub superimposed to it on the microstrip layer, in order to cancel the slot resonant behaviour and provide ultra broad impedance matching. Thanks to this element feature, the antenna can cover the two bands and diplex them into the two ports without the need of additional passive or active components. The detailed design and results of the reflection coefficient, axial ratio and radiation patterns are provided, which confirm the good performance of this simple antenna.

Design aspects of a broadband beam-reconfigurable leaky-wave antenna

Design aspects of a novel beam-reconfigurable planar series-fed array are addressed to achieve beam steering with frequency tunability over a relatively broad bandwidth. The design is possible thanks to the use of the complementary strip-slot, which is an innovative broadly matched microstrip radiator, and the careful selection of the phase shifter parameters.