Shahrokh Saeedi

Novel Coupling Matrix Synthesis for Single-Layer Substrate-Integrated Evanescent-Mode Cavity Tunable Bandstop Filter Design

A new technique for designing tunable bandstop filters is presented. A novel coupling matrix synthesis method for this type of bandstop filter is shown. Phase cancellation, through combining two bandpass filters, is used to derive the coupling matrix. Therefore, classical coupling mechanisms utilized to implement bandpass filters can be used to design and realize bandstop filters. Using this method, bandstop filters can be designed without source-to-load coupling. This eliminates the need for a second substrate when compared to previously reported bandstop filters implemented using substrate-integrated evanescent-mode cavity technology, though the method itself is quite general. Finally, examples of tunable bandstop filters in the range from 3.0 to 3.6 GHz are demonstrated to verify the proposed method.

Tunable, High-Q, Substrate-Integrated, Evanescent-Mode Cavity Bandpass-Bandstop Filter Cascade

A new single substrate-integrated bandpass-bandstop (BP-BS) filter cascade, implemented using high-Q, heavily-loaded, evanescent-mode cavity filters, is presented. The cascade has the capability of dynamically tuning its passband and stopband at any two independent frequencies within a frequency range. A modular design approach is used to design the cascade by directly cascading synthesized coupling matrices of bandpass and bandstop filters. To demonstrate the concept, a 4% second-order Butterworth bandpass filter is integrated with a second-order Butterworth bandstop filter, with 2% fractional bandwidth at 10-dB rejection, to form a cascade that can be tuned continuously from 3000 to 3600 MHz. Measurement shows that a filter cascade with insertion loss as low as 0.9 dB and isolation as high as 100 dB is feasible.

Active resonator using comb-shaped defected ground structure with negative resistance

A design for a new active resonator with gain using a comb-shaped defected ground structure (DGS) with a negative resistance is presented. The negative resistance is realized using a single transistor coupled between two separated parts of the DGS. This negative resistance is realized on a separate circuit-board layer that is attached to the DGS. It is used to compensate for the insertion loss of the resonator. An HFSS-ADS co-simulation is used to combine the electromagnetic structure as well as all parasitic effects along with the behavior of the active circuitry. The design consists of a single resonating element with a center frequency of 2.93 GHz, 3-dB bandwidth of 137 MHz, simulated noise figure of 4.9 dB, and 3.48 dB of gain. The results from the simulation are presented along with the measured response. A good agreement is observed between the results.

Design Methodology of N-Path Filters With Adjustable Frequency, Bandwidth, and Filter Shape

In this paper, an adaptive N-path filter design technique is presented. The filter designed by this method can be reconfigured to different shapes, e.g., Butterworth or Chebyshev with variable bandwidth (BW), based on the user requirements. In addition, an analytical synthesis procedure is introduced to realize high-order bandpass filters (BPFs) based on N-path architecture with a prescribed set of specifications. A proof-of-concept BPF is fabricated and measured in a 65-nm CMOS process. The filter can be reconfigured to realize different filter shapes by changing coupling capacitors. The BW of the proposed filter is also tunable. The passband of the filter is tunable from 0.2 to 1.2 GHz with a gain of 14.5–18 dB, a noise figure of 3.7–5.5 dB, and a total power consumption of 37.5–52.7 mW. The channel BW can be varied from 20 to 40 MHz and the filter out-of-band third-order intercept point (

Single-mode-dual-band to dual-mode-single-band bandpass filter with liquid metal

\Delta f=50

Active tunable substrate integrated evanescent-mode cavity resonator using negative resistance

MHz) is 25 dBm.

A new property of maximally-flat lowpass filter prototype coefficients with application in dissipative loss calculations

A mode-reconfigurable Butterworth bandpass filter, which can be switched between operating as a single-mode-dual-band (SMDB) and a dual-mode-single-band (DMSB) filter is presented. The filter is realized using a substrate integrated waveguide in a square cuboid geometry. Switching is enabled by using empty vias for the SMDB and liquid metal filled vias for the DMSB. The first two modes of the SMDB resonate 3 GHz apart, whereas the first two modes of the DMSB are degenerate and resonate only at the higher frequency. This is due to mode shifting of the first frequency band to the second frequency band. Measurements confirm the liquid-metal reconfiguration between the two operating modes.

Double conversion method for synthesis of inverse filters

A new active tunable substrate integrated evanescent-mode cavity resonator with gain is presented. Gain is achieved through loading the resonator with a negative resistance circuit. The negative resistance is realized using a single transistor circuit implemented on an extra circuit-board layer and coupled into the resonator using aperture coupling. A co-simulation of the electromagnetic structure and active circuit is used for the design of the active tunable resonator. The frequency tuning range of the resonator is from 2259 MHz to 2963 MHz (1.31:1). The resonator exhibits a gain of around 1 dB and a maximum loaded quality factor of 253.

A Dual Linear Polarization Highly Isolated Crossed Dipole Antenna for MPAR Application

This paper presents a new property of maximally-flat filter prototype coefficients. The property can be used to relate the summation of all the coefficients to an elegant expression which only includes the first coefficient. This property is then used to calculate the increase in insertion loss of this type of filters in the presence of dissipative losses due to elements/resonators finite quality factors. This presented equation for the excess loss is very convenient and does not require referring to the prototype element value table. The property is also used to show that the group delay of a maximally-flat lowpass filter at ω = 0 rad/sec is only a function of the first element value of the prototype filter. Finally, a commercial circuit simulation tool is used to generate examples to verify the accuracy of the presented analytical equations. Additionally, the results are compared to expressions found in classical literature.

Capacitive-based, closed-loop frequency control of substrate-integrated cavity tunable filters

A novel method for the inverse filter synthesis of the same type from an original filter is presented. The proposed procedure utilizes a double conversion, frequency inversion and swapping the transfer and reflection functions, which are commonly used for lowpass to highpass filter transformation. Due to the use of double conversions, the resulting filter always has the same type as the original filter. Using this procedure, the available general Chebyshev synthesis method can be used to synthesize inverse Chebyshev and elliptic filters. As an illustration, the coupling matrix of a third-order inverse Chebyshev bandpass filter is synthesized using the presented method. Then the original filter and its inverse filter are fabricated using microstrip technology. The measured and simulated filter results are shown to be in good agreement.