An implementation of harmonic-suppression microstrip filters with periodic grooves

Abstract

In this paper, a new parallel-coupled-line microstrip band pass filter (BPF) improving the harmonic suppression performance of the second harmonic signal (2 , twice the passband frequency) is described. It is found that the desired passband performance is improved and the harmonic passband signal is diminished by enforcing the consecutive patterns in coupled-line and increasing the number of grooves to the optimum values. The recalculation of design parameters such as space-gap between lines, line widths and lengths is not required due to the simple modification of the conventional filter by inserting periodic patterns. To evaluate the validity of this novel technique, order-3 Butterworth BPF centered at 2.5 GHz with a 10% fractional bandwidth (FBW) and order-5 Chebyshev BPF centered at 10 GHz with a 15% FBW were used. When five and three square grooves are used, over 30-dB suppression at second harmonic signal is achieved in simulation and experiment. Finally, the comparison between the characteristics of filters with square and semicircular periodic grooves has been carried out by using the simulated results.

Novel Class of Microstrip Bandpass Filters With Improved Upper Rejection Band

“…Unfortunately, without special measures, most of the microstrip BPFs exhibit harmonic responses degrading the system performance. To overcome this problem, various methods have been presented in the past [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Among them, modification and perturbation to the width of the coupled-line resonators are the most widely used approach to suppress the spurious response [4][5][6][7].…”

Spurious Response Suppression in Hairpin Filter Using DMS Integrated in Filter Structure

“…A ground-plane aperture [5], meandered lines [6], complementary split-ring resonators [7], and grooved substrate [8] have been designed to equalize the modal phase velocities. Strip-width modulation technique is developed to make up wiggly-line, corrugated, grooved or even fractal shape bandpass filters which extend the actual odd mode travelling path toward its even mode counterpart [9][10][11][12]. These continuous and periodic perturbations with various forms are simple and effective approach which can be used to reallocate the transmission zero so that the first spurious passband is suppressed, while the desired passband response is maintained almost unchanged.…”

Harmonics blocking in hairpin filter using Defected Microstrip Structure

“…A ground-plane aperture [2], meandered lines [3], complementary split-ring resonators [4], and grooved substrate [5] have been designed to equalize the modal phase velocities. Strip-width modulation technique is developed to make up wiggly-line, corrugated, grooved or even fractal shape bandpass filters which extend the actual odd mode travelling path toward its even mode counterpart [6,7,8,9]. These continuous and periodic perturbations with various forms are simple and effective approach which can be used to reallocate the transmission zero so that the first spurious passband is suppressed, while the desired passband response is maintained almost unchanged.…”