Radial Loaded Transformed Radial Stub for LPF Stopband Extension

Abstract

Abstract-A low pass filter with ultra-wide band rejection and compact size using a proposed radial loaded transformed radial stubs is introduced and investigated. The implemented unite cell low pass filter with 1-dB cutoff frequency f c of 3.2 GHz demonstrates stopband rejection up to 11.8 f c , i.e., 38 GHz. The design is further extended to the high-order LPF through cell cascading. The implemented four-cell LPF with f c of 3.6 GHz demonstrated 35 dB rejection from 4.8 GHz to 39 GHz, 50 dB rejection from 5.4 GHz to 26 GHz (7.2 f c ) and 20 dB rejection from 4.4 GHz to 50 GHz (13.8 f c ). The measured passband insertion loss is less than 1.7 dB, and group delay is 0.45 ∼ 0.8 nS. The size of the four-cell low pass filter is only 0.33λ g × 0.135λ g , (λ g is the guide wavelength at center cutoff frequency) without using any lumped elements.

Design of Radial Microstrip Band Pass Filter With Wide Stop-Band Characteristics for GPS Application

“…The LPF section with ultra-wide stop-band can be designed by using the transmission line elements (coupled line, transmission line and radial stub), which can be represented by lumped elements in certain frequency range [14][15][16]. The radial stub used in filter configuration can be analyzed as a series combination of an inductor and a capacitor and their value of input impedance (Z in ), inductance (L r ) and capacitance (C r ) can be calculated as [24]:…”

“…Using the design equations [14][15][16]24], the design parameters of microstrip LPF for 3-dB cut-off frequency of 1. Next, a slot is etched out in the 50 Ω microstrip line of this LPF; the structure still works as LPF.…”

“…The frequency band allotted for GPS receiver system is 1.559 GHz-1.610 GHz [1]. According to the need of narrowband BPFs in terms of better performance or size miniaturization various designs have been proposed [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The stepped impedance parallel coupled resonators are used for suppression of harmonics in BPF [2].…”

“…Compact narrowband BPFs are also designed using two stub loaded open loop resonator [11] and hybrid resonator [12] with good in-band characteristic at the cost of out-of-band characteristic lower than 4f c . Other methods for size miniaturization and harmonic suppression use defected ground structure (DGS) [13] and radial stub [14][15][16]. By combining both techniques DGS and radial stub, miniaturized dual-mode ring BPFs with wide stop-band have also been proposed [17,18].…”

Design of switchable microstrip low pass‐band stop‐band pass filter

“…The switching is realized by connecting and disconnecting the conducting pads for ON and OFF state respectively. A conventional transformed radial stub (TRS) cell [11][12][13][14] is used for the proposed work, to achieve wide stop-band characteristic. The substrate used in this design was RT/duroid RO5880, with a dielectric constant of e r 52:2, tan d50:0009 and a substrate thickness of 1.57 mm.…”