Dual-Band Bandpass Filter With Controllable Stopband Bandwidth

A novel dual-band bandpass filter (BPF) is proposed with independently controllable transmission zeros (TZs) which can realize widely tunable stopband bandwidth (BW). The planar microstrip filter consists of a three-degree L-C ladder lowpass filter loaded with two unsymmetrical shorted stubs which are used to produce different TZs. By tuning the parameters of the two unsymmetrical shorted stubs, the TZs can be independently controlled. Therefore, the BPF has independent controllable center frequencies (CFs), passband bandwidths, and stopband bandwidths between adjacent passbands. All the L-C values in the equivalent circuit of the proposed filter are optimized to fulfill the design specifications. For demonstration, a dual-band BPF is designed. The measured results show good agreement with the simulated ones.

A compact simple microstrip lowpass filter based on elliptical analyzed resonator

In this article, a compact microstrip lowpass filter (LPF) using elliptical shaped resonators with ultra-wide stopband is rendered. In this respect, LC equal structures of the elliptical shaped resonators are calculated based on the formula of circumference. In addition, to calculate transmission zeros of the presented elliptical shaped resonator, the LC equal structure and its output to input ratio are employed. The proposed LPF has a −3 dB cut-off frequency at 1.50 GHz and the stopband bandwidth of the designed filter is about 13fc, which refers to its ultra-wide stopband. The occupied circuit size of the presented filter is 0.151λ g × 0.044λ g (λ g is the guided wavelength at 1.50 GHz). The designed filter is fabricated on RT/Duroid 5880 substrate. The results of the fabricated and designed filter have clearly demonstrated that not only has the proposed LPF shown a suitable agreement between measured and simulated S-parameters, but also an appropriate stopband bandwidth.

Half-Elliptical Resonator Lowpass Filter with a Wide Stopband for Low Band 5G Communication Systems

In this paper, a lowpass filter is designed using half elliptical resonators with a wide stopband. New formulas are presented to achieve a circuit model for the half elliptical resonators used in this work. Additionally, the transfer function and transmission zero equations are used to adjust the frequency of the transmission zeros of the filter. The cut-off frequency of the lowpass filter is 1.26 GHz with a sufficiently large stopband, extending from 1.48 GHz to 20 GHz. The proposed filter’s figure of merit is 62,520, demonstrating its outperformance compared to the state of the art. The filter is implemented on a RT-5880 substrate with a constant dielectric of 2.2, thickness of 31 mil and loss tangent of 0.0009. The LPF was fabricated and tested, showing good agreement between the simulated and measured results.

Optimizing the Amplifier Bandwidth for Pulse Reception

<p>Detecting and recognizing pulses is a critical task, in fields as widely separated as telecommunications, lidar, and target illumination. In all cases, the signal-to-noise ratio (SNR) is a key parameter that can be used to determine both the potential rate of errors and the probability of correct detection. In this paper the relationship among pulse width, amplifier bandwidth, and SNR is determined through modeling four approximations to pulse shapes and four amplifier lowpass filter configurations. The analysis determined that, given a specific filter and pulse shape, the bandwidth that maximizes SNR is a constant divided by the pulse width. For example, if the pulse has a Gaussian shape and the amplifier incorporates a second-order Chebyshev lowpass filter, this constant is 0.3389. Applying this, if the pulse width is 20 ns the maximum SNR comes for a filter bandwidth of 16.95 MHz, while if the pulse width is 50 µs the SNR is maximized at a 6.778-kHz bandwidth. Passing the signal through a filter also distorts the signal shape; the temporal shift and pulse lengthening are also determined. The calculated values are offered as inputs to a potential trade space that includes SNR, pulse distortion by the filter, and cost.</p>

Optimizing the Amplifier Bandwidth for Pulse Reception

<p>Detecting and recognizing pulses is a critical task, in fields as widely separated as telecommunications, lidar, and target illumination. In all cases, the signal-to-noise ratio (SNR) is a key parameter that can be used to determine both the potential rate of errors and the probability of correct detection. In this paper the relationship among pulse width, amplifier bandwidth, and SNR is determined through modeling four approximations to pulse shapes and four amplifier lowpass filter configurations. The analysis determined that, given a specific filter and pulse shape, the bandwidth that maximizes SNR is a constant divided by the pulse width. For example, if the pulse has a Gaussian shape and the amplifier incorporates a second-order Chebyshev lowpass filter, this constant is 0.3389. Applying this, if the pulse width is 20 ns the maximum SNR comes for a filter bandwidth of 16.95 MHz, while if the pulse width is 50 µs the SNR is maximized at a 6.778-kHz bandwidth. Passing the signal through a filter also distorts the signal shape; the temporal shift and pulse lengthening are also determined. The calculated values are offered as inputs to a potential trade space that includes SNR, pulse distortion by the filter, and cost.</p>