High Isolation Diplexer Research Articles

Bandpass Filter and Diplexer Based on Short-Circuited Stub-Embedded Resonators and Novel Coupling Scheme

A novel coupling scheme is proposed based on short-circuited stub-embedded resonator (SCSER) for bandpass filters (BPFs). The BPF utilizing SCSER owns three transmission zeros (TZs) that are controlled by short-circuited and open-circuited stubs. Based on the proposed SCSER and coupling structure, a novel high-isolation diplexer is presented. When the TZ is allocated in the opposite channel and impedance transformation is carried out in the common port, the proposed diplexer can be realized by directly combining two different BPFs without an additional matching network. For the demonstration, a BPF and a diplexer based on SCSER are fabricated and measured. The measured results agree well with the simulated ones.

Design of High-Order Resonator HTS Diplexer with Very Different FBW

Adopting the deformed stepped impedance micro-strip line structure resonators (SIRs), the external weak coupling hairpin SIR (HSIR) and external strong coupling opening SIR (OSIR) resonators are designed, respectively. These two types of resonators are convenient for creating an ultra-narrow band and broadband filters, respectively, and can broaden the second harmonic passband. A high isolation diplexer without an impedance matching structure is realized by cascading 12-order and 14-order HTS filters composed of OSIR and HSIR resonators with a high isolation T-shaped structure. The diplexer is fabricated on a thin YBCO/MgO/YBCO (a MgO wafer with YBa2Cu3O7 thin film deposited on both sides) film with a dimension of 31.85 mm × 17.28 mm, a thickness of 0.5 mm, and a dielectric constant of 9.8. At 77 K, the measured central frequency of the diplexer is 2395 MHz and 3300 MHz, the fractional bandwidths (FBW) are 1.25% and 24.24%, the out-of-band rejections are greater than 60 dB/MHz, the 2f0 are located at 5.1 GHz and 6.6 GHz, the insertion loss is less than 0.20 dB, and the return losses are better than 16 dB and 15 dB. The diplexer has the advantages of a simple design method, compact structure, low insertion loss, high sideband rejection, and high isolation.

Design of broadband RF transceiver front-end using highly selective diplexer and high Q-factor hybrid resonator bandpass filters

In this paper, a development of low cost, miniature, highly integration broadband RF transceiver front-end using the high selectivity hybrid resonator RF bandpass filters, and diplexer integrated with shielding case is presented. The proposed RF transceiver frontend operates at the 2.7 GHz for transmitting and 2.4 GHz for receiving, supporting a channel bandwidth of 100 MHz with frequency division duplexing mode. The designed low loss, high selectivity hybrid resonator bandpass filters are utilized to channel selection and reject the interference signal. The high isolation diplexer is employed to separate the Tx and Rx signals and reject the interferences from other systems to the RF receiver as well as filter out the harmonics generated by the RF transmitter. The measured performance of the proposed RF transceiver front-end module is superior to the requirements as well as can support high spectrum efficiency and high data rate communications with low error vector magnitude.

High-isolation diplexer based on dual-mode substrate integrated waveguide resonator

AbstractA high-isolation diplexer based on a dual-mode substrate integrated waveguide (SIW) resonator is proposed in this paper. Based on the theory of the dual-mode resonator, the miniaturized diplexers are designed by using the SIW dual-mode resonators. The superior isolation of the diplexers is obtained because the two operating modes of the dual-mode SIW resonators are not directly coupled and there is no interference with each other. In order to further improve the isolation of the circuit, the number of the order of the diplexer is added. Equivalent circuits are given to analyze and design the dual-mode high-isolation diplexers. Detailed analyses are given according to the equivalent circuits. The dual-mode third-order and fourth-order diplexers are designed and fabricated. The measured results agree well with the simulated ones. The total sizes of the fabricated third-order and fourth-order diplexers are 1.78λg × 2.64λg and 1.79λg × 3.63λg, respectively.

High isolation diplexer using stub‐loaded resonators

This Letter reports a high isolation diplexer using stub-loaded resonators (SLRs). Each SLR can generate one transmission pole and one transmission zero (TZ). By changing the length of the open stub, the frequency of the TZ can be adjusted. The upper channel filter using the capacitive coupled SLRs can have TZs above the passband, while the lower channel filter using inductive coupled SLRs can have TZs below the passband. With those TZs, the isolation of the diplexer is greatly improved. A high isolation diplexer is designed and fabricated to validate the design concept.

High Selective Microstrip Bandpass Filter and Diplexer With Mixed Electromagnetic Coupling

A high selective bandpass filter and a high isolation diplexer by using mixed electromagnetic coupling have been presented. The filter transmission zeros (TZs) are attributed to the mixed electromagnetic coupling, and additional resonators are not required. TZs also can be adjusted by controlling the electric and magnetic couplings. The diplexer is fabricated and measured, and the new design is demonstrated by measurement. The diplexer has a compact size of $0.483\lambda_{\rm g}\times 0.585\lambda_{\rm g}$ , and a measured high isolation of no less than 42 dB.

Compact and High-Isolation Diplexer Using Dual-Mode Stub-Loaded Resonators

A novel compact microstrip diplexer for UMTS and WCDMA system is proposed in this letter. The diplexer is mainly composed of three dual-mode stub-loaded microstrip resonators. Two resonant modes of a stub-loaded resonator work together with one mode produced by the common stub-loaded resonator to form a passband or operating band of the proposed diplexer. Extensive study is then conducted on coupling scheme involved in various parts of the diplexer. In particular, the resonance of a resonator is employed to create a desired transmission zero in the stopband, thus improving the isolation between two passbands. The proposed diplexer is in final fabricated and measured. A good agreement between EM simulated and measured results evidently validates the proposed methodology.

Switchable and High-Isolation Diplexer With Wide Stopband

This letter presents a switchable diplexer composed of a stepped-impedance distributed coupling feeding line, four different quarter-wavelength stepped-impedance resonators (SIRs), two shunt open stubs, two p-i-n diodes, and bias circuitry. Compared with previous works, the proposed circuit features compactness, wide stopband, high selectivity, and independently switchable channels. To suppress harmonics, various quarter-wavelength SIRs with the same fundamental frequency but harmonic frequencies in stagger are used. Open stubs are also adopted to achieve an optimal stopband response. To meet the demands of reconfigurable application in wireless communication systems, switching circuit is integrated into the proposed diplexer to develop a switchable diplexer. In this way, mismatch losses during integration and circuit size are both further reduced. Simulations and measurements have been carried out to verify the design concept with good agreement.

High isolation diplexer using quarter-wavelength resonator filter

A microstrip diplexer with very high isolation is presented. The diplexer consists of two compact filters with quarter-wavelength resonators coupled by the metallised vias. Each metallised via is inductive and behaves as a K-inverter. This type of filter has two adjustable transmission zeros on each side of the passband, which can be shifted by changing the coupling coefficient between the source and load. By locating the transmission zero of one channel at the passband of the other channel, very high isolation of the diplexer can be achieved. Simulated results of the fabricated diplexer agree well with measured results.