Optimal design of third‐order microstrip bandpass filters by direct synthesis technique (DST)

Self Cite

Summary In reality, it is not easy to design microstrip filters for the sake of distributed‐element effect. It is an effective approach to approximate distributed‐element structures through appropriate lumped‐element circuits. In this paper, some basic microstrip structures are discussed, whose equivalent lumped‐element circuits are derived. Then, a novel microstrip filter is obtained by connecting these microstrip structures, according to the similar topology of the third‐order lumped‐element bandpass filter. The equivalent lumped‐element counterpart of the proposed microstrip filter clearly reveals its physical mechanism, ie, how the resonances are created and coupled and how the transmission zeros are created. Furthermore, a set of the design formulas are presented, which can be used to calculate initial structure parameters and then facilitate design process. The proposed microstrip bandpass filter can realize a third‐order elliptic bandpass response with one transmission zero at each side of the passband. In addition, two short‐circuited stubs are added to input/output ports to create the third transmission zero. The filter is featured by good frequency selectivity and out‐of‐band suppression. For demonstration, an actual example was designed, fabricated, and measured.

Section: Proposed Microstrip Bandpass Filter and Its Design Proceduresmentioning

confidence: 97%

Compact third‐order microstrip bandpass filter designed by the distributed‐ to lumped‐element equivalence

Xiao

Cao

et al. 2018

Self Cite

“…The layout and LC equivalent circuit of a transmission line, open‐end, short‐end, and coupled line are presented in Figure . The values of the inductors and capacitors can be obtained from the LC model as follows:

If \frac{true}{l_{y} < λ_{g}} C_{y} = \frac{l_{y}}{Z_{y} v_{p}},

If \frac{true}{l_{s} < λ_{g}} L_{s} = \frac{Z_{s} l_{s}}{v_{p}},

L_{t} = \frac{Z_{t} sin ((), \frac{2 π}{λ_{g}} l_{t})}{ω}, C_{t} = \frac{tan ((), \frac{π}{λ_{g}} l_{t})}{ω Z_{t}},

C_{s} = \frac{((), Z_{ce} - Z_{co}) italictan ((), \frac{2 π}{λ_{g}} l_{c})}{2 ω Z_{ce} Z_{co}}, C_{p} = \frac{italictan ((), \frac{2 π}{λ_{g}} l_{c})}{ω Z_{ce}},

where, Z t , Z y , Z s , and Z c are the impedances of the single, open‐end, short‐end, and gap of the microstrip line with the lengths of l t , l y , l s , and l c , respectively. Here, λ g represents the guided wavelength, ω is the angular center frequency, and v p is the phase velocity of the propagation.…”

Section: The Equivalent Circuitmentioning

confidence: 99%

“…Figure 4. The values of the inductors and capacitors can be obtained from the LC model as follows [19][20][21][22][23] : Abbreviation: BPF, bandpass filter.…”

Section: The Equivalent Circuitmentioning

confidence: 99%

A dual‐mode tunable bandpass filter for GSM, UMTS, WiFi, and WiMAX standards applications

Maragheh

Dousti

Dolatshahi

et al. 2019

Summary This paper presents a dual‐mode tunable bandpass filter (BPF) for global system for mobile communication, universal mobile telecommunications system, wireless fidelity, and worldwide interoperability for microwave access standard applications. The proposed filter consists of a stepped‐impedance resonator, single resonator, and coupled line, which are loaded with varactors. The center frequency and bandwidth of the proposed filter can be tuned with tuning varactors. Furthermore, the measurement results show that the BPF can be tuned over the frequency range of 1.8 to 2.5 GHz. Moreover, the bandwidth can be changed at each certain frequency. Furthermore, using PIN diodes, a bandstop filter is added to the tunable BPF to reduce the out‐of‐band frequencies around the desired frequencies. The values of LC equivalent circuits are calculated, and the results are compared with those obtained from the layout of the proposed structure. Finally, the measurement results justify the simulation results.

Varactor‐tuned bandpass filter using a microstrip stepped‐impedance combline filter and a new J‐inverter

Hoseinabadi,

Bagher Tavakoli,

Rastegar Fatemi

et al. 2024

The stepped‐impedance combline band pass filter (BPF) with novel input and output networks based on a new proposed J‐inverter, which increases the center frequency tuning range with constant bandwidth (BW), is discussed. The even and odd mode analysis shows that the stepped resonators provide the necessary conditions for the appropriate coupling coefficient to keep the BW constant. In order to create an appropriate quality factor, the new proposed J‐inverter is used. In the frequency response of the stopband region, three transition zeros (TZs) are generated, which two of TZs are controllable. The proposed tunable BPF has been fabricated on RO4003 substrate with a dielectric constant of 3.38 and 0.813 mm thickness. The size of the filter is compact and is only , where is the guided wavelength at the lower center frequency. The center frequency is equal to 1.723 GHz and a frequency tuning range from 1.2 GHz to 2.246 GHz with 100 MHz constant 3 dB absolute BW, the insertion loss of 1.4–3.17 dB and return loss of 17.8–25.9 dB is achieved.