Compact Quadband NGD Microstrip Circuit for 2-6 GHz
ISM Bands
Nathan B. Gurgel,
Glauco Fontgalland,
Idalmir S. Queiroz Jr.,
Samanta M. Holanda,
Benoit Agnus,
Jerome Rossignol and
Blaise Ravelo
With the increasing interest in negative group delay (NGD) function for RF and microwave circuits, and sensing applications, techniques to fit multiple NGD bands in a single and compact structure can open new possibilities. In this work, a simple and innovative compact quadband NGD microstrip circuit is presented for all ISM bands between 2 GHz and 6 GHz. The circuit is composed of a base line (BL) coupled to the transmission line, which sets the lowest NGD band, and each additional NGD band is created by inserting stubs into the BL. The impact of each stub on the overall circuit is analyzed using parametric simulation. The design and tuning method of the coupled line used to achieve the NGD multiband function is described in detail. Through the insertion loss and group delay results, a well-fitted correlation is observed between the simulated and measured results, where the simulated transmission coefficient and group delay show NGD quadband response with center frequencies at 2.46, 3.49, 4.96, and 5.69 GHz with respective NGD bandwidth of 0.89%, 0.83%, 0.66%, and 0.97%, respectively, whereas the measured results present center frequency NGD deviation of less than 1%. In addition, the NGD quadband circuit prototype has a compact size 40.2 × 30.2 × 1.57 mm3. The measured NGD results are in good agreement with simulated ones.
