Substrate integrated waveguide interconnects in high-speed electronic systems

Abstract

The big data era has arrived, and the requirements for high-speed data transmission continue to increase. It is urgent to develop new types of ultra high-speed and high-density interconnects to realize Terabit and even higher data transmission. Conventional planar interconnects such as microstrip lines, strip lines, and coplanar waveguides are in the form of open structures. Owing to the bandwidth and loss limitation, their signal integrity problems such as delays, attenuation, and crosstalk are severe and cannot transmit high-speed data when the data transmission rate is higher than a Gigabit. Based on conventional planar interconnects, SerDes (Serializer-Deserializer), differential lines, equalization, and pre-emphasis techniques were developed to improve the transmission performance. However, these techniques could not radically solve interconnect problems in high-speed data transmission. Substrate integrated waveguides (SIWs), as a new kind of planar interconnect, take advantage of the easy integration of conventional planar interconnects and the high bandwidth, low loss, and low crosstalk of waveguides. SIW interconnects have been gradually applied to realize high-speed data transmission. This paper presents all kinds of SIW interconnects, their physical structures, propagation performance, transmission modes and mechanisms, and data transmission rates in detail. Recent research studies of the authors are also introduced. According to the transmission mode, SIWs can be classified into three types: SIWs with TE mode, substrate integrated coaxial lines (SICLs) with TEM mode, and SIWs with mixed modes. The SIWs with TE mode have band-pass and hence base-band signals that should be modulated before transmission and demodulated after transmission. The introduction of modulation and demodulation techniques in SIWs increases the complexity of the transmission systems but can also improve the channel utilization and increase the data transmission rate. An SICL does not need modulation and demodulation since it propagates the TEM mode and has good signal integrity performance owing to its quasi-closed structure. SIWs with mixed modes integrate the SIW and other types of interconnects to simultaneously transmit TE mode and TEM mode by sharing conductors or media. According to the number of channels, SIWs can transmit single-channel signals through one physical channel, multichannel signals through one physical channel, or multichannel signals through multiple physical channels. Single-channel signal transmission through one physical channel uses one physical channel to transmit single-channel signals in single or multiple modes. Multichannel signal transmission through one physical channel uses one physical channel to transmit multichannel signals with complicated modulation techniques or multiple modes. Multichannel signal transmission through multiple physical channels uses multiple physical channels with single or multiple modes based on parallel data transmission. All kinds of new planar interconnects based on SIWs provide key techniques and solutions for high-speed data transmission.