Also, recent challenges and techniques for designing BPF were reported in 5. In 4, a BPF with compact size and low IL designed using coupled line resonators and spoof surface plasmon resonators for communication applications was presented. Microstrip filters such as bandpass filters (BPFs) 4, 5 and lowpass filters (LPFs) 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 have a key role in the design of modern communication systems as they are used for removing unwanted signals and harmonics from radio signals. Microwave components which exhibit these attributes play a crucial role in such modern systems. These specification requirements include low insertion loss (IL), sharp filter response, also known as high roll-off rate (ROR), compact size, high selectivity, high isolation between output ports, wide stopband response, high suppression factor (SF), simple structure and affordable manufacturing processes. In particular, passive microstrip devices such as filters and power dividers have critical specification requirements. In recent years, modern wireless communication systems have become increasingly important, and the demand for high-performance active and passive RF/Microwave components such as antennas 1, 2, 3, filters 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, power dividers 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, mixers 33 and multiplexers 34, 35, 36, 37, 38 has grown substantially. The WPD has been fabricated and tested and shows good agreement between simulated and measured results and the proposed design has desirable characteristics for LTE and GSM applications. The proposed WPD has a small size of 33.8 mm × 27 mm (0.42 λg × 0.33 λg), where λg is the guided wavelength at the operating frequency of 1.8 GHz. The proposed modified WPD has a wide 20 dB stopband (from 2.54 GHz to 13.48 GHz) and filters the second to seventh harmonics with attenuation levels of greater than 20 dB. According to the obtained results, the input return loss (| S 11|), output return loss (| S 22|), output insertion loss (| S 21|) and isolation (| S 32|) are better than 34.2 dB, 26.2 dB, 3.52 dB and 31.2 dB, respectively. A lowpass filter (LPF) structure is utilized in both branches of the power divider to provide harmonic suppression. In order to improve on the current state of the art, a modified microstrip WPD is proposed that exhibits a substantially improved stopband and high isolation. However, these WPDs can also exhibit poor out-of-band performance while requiring a large footprint. Hopefully, this article was helpful in expanding your knowledge in regards to designing and simulating in PSpice.Conventional Wilkinson power dividers (WPDs) can provide acceptable performance close to the nominal center frequency. Lastly, an exercise is provided to reinforce the concept of low-pass filter design in this tutorial. You can utilize this concept to design and simulate more complex filters in PSpice. It covers step-by-step procedures with clear and concise explanations and examples to help us better understand the concept. In conclusion, this tutorial provides an in-depth overview of how to design and simulate a low-pass filter in PSpice. Try doing the frequency domain analysis of any of the circuits we have done previously.In the frequency domain, we can say that the input source is allowing all the frequencies to pass straight through it. The straight line represents that the input source is constant (neither increasing nor decreasing with time), unlike that of the capacitor voltage. The green line at the top represents the input AC sweep of the AC source connection. The output plot in frequency domain, or the bode plots of a simple low-pass filter, is given in the figure below. This frequency is present at -3 dB of the maximum magnitude, which is 0.707, or 70% of the maximum magnitude. The limit of the frequencies up to which the circuit allows is known as the critical frequency and is given by the formula. Introduction to Low-Pass FiltersĪ low-pass filter is such a filter that only allows frequencies with lower magnitude to pass through it and blocks the higher frequencies, as the name suggests. At the end of the tutorial, we have provided an exercise for you to do on your own, and in the next tutorials, we will assume that you have done those exercises, and we will not explain the concept regarding them. After that, we will simulate the circuits using PSpice with the step-by-step approach to simulate a circuit, and then we will compare the results with the theoretical discussion (which should be the same). At the start, we will provide a brief and concise introduction to filters, specifically low-pass filters, and bode plots with an explanation of the output they will show. The purpose of a low-pass filter is to allow only the lower frequencies to pass through the circuit and block the higher frequencies. In this tutorial, I will explain the workings of a low-pass filter.
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