Six-State Reconfigurable Filter Structure for Antenna Based Systems

Abstract

This paper demonstrates a six-state reconfigurable band-pass filter intended to add frequency tunability to antenna systems. The present topology produces filter responses with center frequencies of 0 = 9, 10, and 11 GHz and achieves independent bandwidth control with an average tunable passband ratio of 1.73:1 between the wideband configurations ranging from 13.4% and 14.7% and the narrowband configurations ranging from 7.7% and 8.5%. PIN diodes are implemented as switching elements and the distinct states are discretely accomplished by the connection and isolation of strategically placed transmission line sections. The insertion loss of the filter ranges between 1.74 and 1.92 dB. The circuit produces no significant signal distortion resulting in third-order intermodulation intercept points (IIP3) greater than 48 dBm for tones separated by 1 MHz around the center frequencies.

Automated design of tunable impedance matching networks for reconfigurable wireless applications

“…The IMN is designed to match Zs values that range from 20 Ω to 50 Ω, which corresponds to a typical range of variable sources impedances that may be possible due to changes in antenna position [10,16]. In the design optimization process, we pF, respectively, to achieve impedance matching when Zs varies from 20 Ω to 50 Ω. C3 is a switchable capacitor with four discrete values of [5.00, 3.88, 0.65, 0.41] pF that correspond to the four frequency bands of the filter with increasing frequency.…”

“…Reconfigurable filters for tunable/switchable IMNs are significantly more challenging to design than their fixed valued counterparts since they must provide passband impedance matching and stopband rejection for different sets of frequencies and for potentially changing source/load impedances while only modifying a [10][11][12][13][14][15][16][17].…”

“…The in-band constraints on S22 (S22IT ≤ S22IC) and on S21 (S21IT ≥ S21IC) are constructed in the same manner as (10). To ensure that S11 and S22 are large enough outside of the frequency band for each tunable state to provide sufficient stopband rejection, we apply the constraints S11OT ≥ S11OC and S11OT ≥ S11OC, which are defined in a similar manner to (10) except that the constraints are evaluated at a set of frequencies ( − → foi) spanning the spectrum outside of the passband, (11) where RBi and RTi determine the size of the buffer region associated with the stopband rejection constraint for the ith tunable frequency band, and fmin and fmax are the minimum and maximum frequencies that are significant for stopband rejection. The constraint SPT ≤ SPC limits the power at each node of the filter to ensure that the power handling capabilities of the circuit components are not exceeded in any of the possible tunable states.…”

“…A major challenge associated with the realization of reconfigurable wireless systems is the design of tunable impedance matching networks (IMN) for circuits such as low noise amplifiers, power amplifiers, mixers, pre-processing filters, and antennas operating at multiple frequencies with variable load and source impedances [5][6][7][8][9][10]. While significant research efforts have demonstrated the potential performance of tunable IMNs through their physical realization using switches and varactors implemented with standard semiconductor, barium-strontium-titanate (BST), and RF MEMS based technologies [10][11][12][13][14][15][16][17], the design of tunable IMNs has primarily been a manual process that combines well-established design methods for standard non-tunable filters with the specific knowledge of the designer. Given the increasing complexity of reconfigurable wireless systems, systematic automated design techniques must be developed for tunable IMNs to enable greater design flexibility and performance, reduced cost, and shorter time-to-market.…”

Novel Cross-Type Network for Wide-Tuning-Range Reconfigurable Multiband Antennas

“…Frequency tuning can also be achieved using tunable filters in a filter-based reconfiguration. A tunable filter embedded in an antenna can be also regarded as a tunable antenna [13][14][15][16]. The use of reconfigurable antennas has always been hindered by the need for a large number of switches, complex dc wiring, and the limitation of serving one frequency band at a time [2].…”