диафрагмированные волноводные фильтры / bd5188bd-3efd-4e98-b990-275d52f33b9e

Abstract— This paper presents a rectangular waveguide diplexer based on a T-junction can separate a common input signal into two distanced channels at millimeter-wave (mm-wave) spectrum. This diplexer is capable of separating of two channels operating at the frequencies 116 GHz and 183 GHz providing passbands of 4 GHz and 16 GHz for these two channels, respectively. In this work, a H-plane waveguide T-junction is used to achieve the desired results. The simulated results are in good agreement with the diplexer specifications. A return loss of more than 20 dB and an insertion loss of less than 1 dB have been obtained for both channels.

I. INTRODUCTION

DIPLEXERS are key parts of modern communication systems. Advanced microwave communication systems employ diplexers to separate two different RF signals into two different channels. Diplexers are used at the front end of

transceivers to separate the RX and TX signals and at the same time, connect the receiver and transmitter circuits to the antenna port. A diplexer should have a low-insertion loss at the RX and TX passbands, provide good isolation between the RX and TX circuits, and have a high power handling capability. These desired characteristics can be obtained by using conventional waveguides at microwave frequencies [1, 2].

Diplexers operating at high frequencies with far distanced channels have become highly demanded for many applications such as cube-sat radiometers. Most of the existing mm-wave diplexer configurations can only achieve a limited frequency ratio [3], [4]. In [3], a Ka-band diplexer that consists of a highpass filter, hybrid coupler and low-order bandpass filter was designed based on SIW technology. Whereas, in [4], E- plane groove gap waveguide T-junction is used as a connecting part of groove gap waveguide filters. Moreover, based on airfilled substrate-integrated waveguide circular cavities, a coexistence of a microwave and mm-wave diplexer with a large frequency ratio operating was proposed in [5]. This paper presents a rectangular waveguide diplexer can split a common signal into two distanced channels at millimeter-wave (mmwave) spectrum. This diplexer is capable of splitting 116 GHz and 183 GHz while providing a passband of 4 GHz and 16 GHz, respectively, for these two channels.

II. DIPLEXER DESIGN AND RESULTS

Full-wave electromagnetic simulations were undertaken using CST MICROWAVE STUDIO®. Table I shows the design specifications of the proposed mm-wave diplexer. Figure 1 shows the layout of the proposed diplexer based on conventional rectangular waveguide. Two waveguide bandpass filters are designed using the arms of the long T-junction itself. Irises are created to establishing resonators at both arms (channels). At the meeting point of the H-plane T-junction (i.e.

TABLE I

DIPLEXER DESIGN SPECIFICATIONS

(a)

(b)

Fig. 1. (a) The layout of the bottom part of the proposed diplexer (without the upper lid). (b) The whole structure.

the input of each filter), small ridges are created. Two small capacitive ridges are placed at the propagation direction at the beginning of the lower channel waveguide and another two small capacitive ridges are placed perpendicular to the direction