Low-Loss Wide-Tuning-Range Three-Pole Frequency-Agile Bandpass Diplexer With Identical Constant Absolute Bandwidth

Abstract

This paper presents a low-loss, high-isolation and wide-frequency-tuning-range (FTR) (45%) implementation of the three-pole frequency-agile bandpass diplexer (FA-BPD) with identical constant absolute bandwidth (IC.ABW). The FA-BPD includes two three-pole channels and each channel has three transmission zeros (TZs). To develop such a FA-BPD, first, two bandwidth (BW) -identical and -constant frequency-agile bandpass filters (FA-BPFs) with the FTRs of 1.35-2.25 GHz and 1.9-3 GHz are designed individually. Both two FA-BPFs simultaneously employ the cascaded triplet (CT) topology and source-load coupling to introduce three TZs. All couplings of two filters are arranged opposite in sign, thus two TZs of one channel are placed on the side of the other channel. Finally, two FA-BPFs are fed by a common coupling line, thus forming the three-pole 1.35-3-GHz FA-BPD. The design example is fabricated and measured. The experimental results show that the FTRs are 1.35-2.25 GHz (50%) and 1.9-3.0 GHz (44.9%). The ABW of the two channels keeps nearly a constant of 194±8 MHz. The insertion loss (IL) varies within the range of 2.1-3.3 dB. The measured isolation level keeps better than 38 dB.INDEX TERMS Element variable coupling matrix, frequency-agile bandpass diplexer, identical constant absolute bandwidth.

Three‐pole wide‐tuning‐range balanced frequency‐agile bandpass filter with constant absolute bandwidth and 3 transmission zeros

“…The even‐ and odd‐mode equivalent circuits of VLHWR type II are shown in Figure C,D. To realize the coupling topology in Figure B, only the even‐mode resonance of the VLHWR type II is employed here and the odd mode needs to be suppressed by choosing the proper resistor R s . Here, the DM equivalent circuit of VLHWR type I is used to realize the resonant nodes R 1 and R 3 in Figure B, and the even mode resonance of VLHWR type II is used to realize resonant node R 2 .…”

Tunable Diplexer Composed of Asymmetric Hairpin Resonators Using Varactors with Constant Passband Bandwidth and High Isolation Characteristics

“…Diplexers, which are a basic circuit configuration of multiplexers and composed of two filters, have been exhaustively researched for many years. [1][2][3][4][5][6][7] Rosenberg et al [1] first presented a tunable multiplexer for broadcast satellites by tunable waveguided fourth-order elliptic-function BPFs using tuning plungers.…”

“…Recently, Xu et al [5] presented the most compact planar-type tunable diplexer composed of chip lumped elements, with three kinds of silicon varactor diodes. Li et al [6] also developed a compact planar-type tunable diplexer with large FTR, which is 1.9 to 3 GHz, and very low deviation of BW for low-and high-band BPFs. In the most recent work by the same research group, a larger FTR, which is 2.2 to 3.5 GHz, of their simple structure was realized by maintaining the compact size and almost unchanging BW for each BPF.…”

“…However, it is quite difficult to configure a tunable diplexer structure with constant ABW and low insertion loss maintaining reasonable circuit size. Especially in, [5][6][7] complex design techniques are applied to configure the structure for tunable BPFs.…”

Short-Circuited Stub-Embedded Ring Resonator and its Application in Diplexer

“…As a essential component of RF front end, the diplexer has been widely applied in modern high quality wireless communication systems, including CDMA, WLAN and LTE [1]- [4]. The most common approach to realize a diplexer is to combine two bandpass filters (BPFs) through an impedance-matching junction with two branches [5]- [8].…”