This paper presents a dual-band bandpass filter with independent switchability of each passband. By taking advantage of harmonic ratio of asymmetric stepped-impedance resonators, 2.4- and 5.2-GHz resonators are designed. The second resonance of 2.4-GHz resonators is designed to be suppressed by a transmission zero created by extended feed lines. To achieve a wide upper stopband, 5.2-GHz resonators are designed with a scheme that the second peak of these resonators would not appear at a frequency lower than a third peak of 2.4-GHz resonators. Several design graphs for deciding both geometric parameters and transmission zeros are plotted by using the information obtained from electromagnetic simulations. While extracting coupling coefficients between resonators, an external quality factor at 50-Ω port is fixed to determine the precise transmission zeros. Two kinds of feed lines, such as a hook type and a spiral type, are developed, and spiral-type feed lines are chosen for realizing switchable filters. By controlling p-i-n diodes, four states of switchable dual bands are clearly presented in simulations and experiments.

Independently Controllable Dual-Band Bandpass Filters Using Asymmetric Stepped-Impedance Resonators

This paper presents compact CMOS millimeter-wave bandpass filters based on a new stepped-impedance technique by incorporating a grounded pedestal into the microstrip line. The characteristic impedance of a microstrip line can be effectively changed by varying both the height of pedestal and the width of line. Therefore, the stepped-impedance resonators and stubs can be realized in the compact three-dimensional forms in CMOS. Two millimeter-wave bandpass filters were designed by using the new stepped-impedance resonators and stubs. Their chip sizes are significantly miniaturized to 0.37 x 0.2 mm2, equivalently 0.012 λg2 . The first chip filter has the insertion loss of 3.1-3.4 dB in 59-71 GHz and the second filter has the insertion loss of 3.5-3.8 dB in 53-64 GHz. Both chip filters have good stopband suppression attributed from the existence of transmission zeros.

Compact Millimeter-Wave CMOS Bandpass Filters Using Grounded Pedestal Stepped-Impedance Technique

A new concept of tuning transmission zeros (TZs) in 4-pole tunable bandpass filters is demonstrated. In this work, the tuning elements that were conventionally used for bandwidth control are also utilized for adjusting the TZs at the same time. As a result, the selectivity of the tunable filter can be controlled without increasing the filter order and complexity. A 4-pole stripline filter is used to demonstrate this concept. The filter can be continuously tuned from 1.25 to 2.1 GHz and two TZs are employed to improve the stopband suppression to $> {\hbox{60 dB}}$ at 200 MHz from the passband. These TZs can also be moved from the upper stopband to the lower stopband without any auxiliary tuning elements to significantly change the stopband suppression. The high rejection filter is useful in wireless systems and cognitive radios with large interferers.

Tunable 1.25–2.1-GHz 4-Pole Bandpass Filter With Intrinsic Transmission Zero Tuning

This paper presents a novel method for designing single- and dual-band filtering switches based on coupling control. First, the ON- and OFF-state coupling matrices are analyzed to achieve bandpass responses and high isolation, respectively. Then, they are used to guide the low temperature cofired ceramic circuit realization. The ON- and OFF-states are enabled by controlling the PIN diodes in the filter feeding structures. In the ON-state, the circuit is equivalent to a bandpass filter without signals passing through the PIN diodes, which avoids additional loss introduced by the PIN diodes. For the OFF-state isolation, it is realized by controlling the coupling of the filtering circuit, which is different from that of conventional switches by turning off transistors or diodes to obtain isolation. Thus, isolation is considerably enhanced. For demonstration, a single-band filtering switch is implemented with a compact size of 0.050 λg × 0.048 λg × 0.023 λg . Furthermore, a dual-band one of the same dimension is realized with controllable passband frequencies and bandwidths in the ON-state as well as high isolation in OFF-state. The presented filtering switches feature compact size, low ON-state insertion loss, high OFF-state isolation, and high reliability, which are suitable for industrial applications.

Single- and Dual-Band LTCC Filtering Switch With High Isolation Based on Coupling Control

A switchable microstrip bandpass filter (BPF) with reconfigurable on-state frequency responses is proposed. The filter consists of a two-pole BPF and two switchable delay lines. The proposed filter features not only switch ability with an on-off ratio of 41.2 dB but also two on-state frequency responses: Chebyshev response and quasi-elliptic-function response. Experiment was carried out to validate the design concept, and the simulation agrees well with the measurement.

Switchable Microstrip Bandpass Filters With Reconfigurable On-State Frequency Responses

In this letter, a compact electronically switchable parallel-coupled microstrip bandpass filter (BPF) based on quarter- wavelength resonators and p-i-n diode switch is proposed. The proposed filter occupies only half the circuit size of the conventional parallel-coupled filter. In addition, the type and length of each coupled-line section is suitably chosen such that the inherent transmission zeros associated with the coupled-lines can be used to reject the spurious passbands effectively. By adding only one p-i-n diode along with a simple bias control circuitry, the proposed filter becomes electronically switchable with no current consumption when the filter is turned off. Specifically, a switchable fourth-order microstrip BPF with a center frequency f0 of 2 GHz, passband insertion loss less than 3 dB, and wide stopband up to 7.7 f0 in the ON state is demonstrated. The isolation of the filter is better than 30 dB from dc up to 7.7 f0 in the OFF state.

Compact Electronically Switchable Parallel-Coupled Microstrip Bandpass Filter With Wide Stopband

We report on the design and experimental results of Q-band GaAs bandpass filters (BPFs) for the Atacama Large Millimeter/submillimeter Array (ALMA) band-1 receiver. The BPF is required to reject the lower side band from 15.3 to 29 GHz while retain minimum insertion loss across the passband of 31.3 to 45 GHz. In order to reduce the size and weight of receiver module effectively, on-chip BPF designs using the commercial GaAs process are proposed. The parallel-coupled BPF with quarter-wavelength resonators is adopted to achieve a wide fractional bandwidth of about 37%. In addition, the capacitive/inductive loaded coupled-line and the stepped-impedance resonator are used to largely reduce the filter size. Moreover, the cross-coupling effect is introduced to create transmission zeros, such that the required 25 dB stopband rejection below 29 GHz can be achieved. Specifically, two GaAs BPFs with sizes less than 1.24times0.8 mm2 are demonstrated. They will be applied to the multi-chip-module version of ALMA band-1 receiver prototype for further system evaluation and feasibility studies.

Q-Band GaAs Bandpass Filter Designs for ALMA Band-1

This paper presents two Q-band bandpass filter designs that are targeted for application in the Atacama large millimeter-wave and submillimeter-wave array (ALMA) radio telescope. The bandpass filter is required to reject the lower side band from 15.2~29 GHz and retain minimum loss across the passband of 31.3~45 GHz. The bandpass filter based on WR22 waveguide is first presented. Specifically, the measured in-band insertion loss is around 0.4 dB, and the rejection of lower sideband is better than 34 dB. To further reduce the circuit size and to ease the integration with other MMICs in the receiver, a planar filter design based on GaAs process is also demonstrated. It will be applied to the multi-chip module version of the heterodyne receiver design to achieve more compact module size.

Yu-Shu Hsieh

Papers

Compact Electronically Switchable Parallel-Coupled Microstrip Bandpass Filter With Wide Stopband

Q-Band GaAs Bandpass Filter Designs for ALMA Band-1

Q-band bandpass filter designs in heterodyne receiver for radio astronomy