Kai Chang

On the Analysis and Design of Spurline Bandstop Filters

The parameters of general two-coupled lines and symmetric three-coupled lines in an inhomogeneous medium for the lossless case are obtained. The impedance and chain matrices of spurline bandstop filters are derived. One-section spurline bandstop filters with their stopbands centered near 33 GHz have been designed and tested. There is excellent agreement between the experimental results and those predicted theoretically.

DESIGN AND PERFORMANCE OF MILLIMETER-WAVE END-COUPLED BANDPASS FILTERS

The design and performance of millimeter-wave microstrip/suspended-stripline end-coupled bandpass filters are presented. Filters in Ka-band (26.5 to 40 GHz) and W-band (75 to 110 GHz) using suspended-stripline and microstrip have been designed. Good agreement between the experimental results and those predicted theoretically was observed. Measured passband insertion losses of less than 1 and 0.5 dB have been achieved in W- and Ka-band, respectively. An extremely wideband waveguide-to-microstrip transition with an insertion loss of 0.25 dB over the full W-band is also presented.

System feasibility study of a microwave/millimeter-wave radar for space debris tracking

A 35 GHz millimeter-wave radar system has been studied for space debris tracking. The objective is to track the particles ranging in size from 4 mm to 80 mm up to a range of 25 km. The system requires various state-of-the-art technologies including phased arrays, monopulse tracking, pulse compression, high power transmitters, low noise receivers, and pulse integration signal processing techniques.

Analysis and Design of Spurline Bandstop Filters

The chain matrices of spurline bandstop filters employing asymmetrical two lines and symmetrical three lines in an inhomogeneous medium were derived and used for accurate filter design. One-section spurline bandstop filters at 26.5 to 40 GHz have been designed and tested. There is an excellent agreement between the experimental results and those predicted theoretically.

Multiband phased array antennas for wireless communications

Need for exchanging a wide range of information among many users in a timely manner, has resulted in a rapid expansion of frequency utilization, in addition to bandwidth expansion. High resolution video, infrared sensors, and various types of radars now are expected to be readily exchanged among users, and these users can be located on the surface, in the air and these users can be expected to be not only mobile, but highly mobile. To exchange this high volume information reliably among these many users requires a high data rate and the use of directional antennas. The use of directional antennas would also tend to reduce the possibility of interference among the users and also reduce the RF terminal power consumption requirements. This paper describes a multi-functional phased array antenna design, which can operate at either Ku-Band or Ka-Band without the need for switching or reconfiguration; and can be readily switched to provide information in an timely manner to the various users.

Integrated image-line steerable active antennas

This paper reports a varactor-tuned Gunn oscillator constructed in an image-line circuit and integrated with a grating antenna. The combined circuit exhibited a 2 percent electronic tuning range corresponding to a frequency steerable range of 4 degrees. The active antenna demonstrated a clean spectrum with low side lobes. The beam angles agree very well with the prediction. The circuit can be produced at low cost and should have many applications at millimeter-wave frequencies

Design and Performance of a W-Band Broadband Finline Diplexer with Over 20 GHz Bandwidth

This paper describes the design and performance of a contiguous 90- to 112-GHz diplexer using the integrated finline technique. State-of-the-art results of 1.5 dB insertion losses have been achieved. There is good agreement between the experimental results and those predicted theoretically; these results demonstrate a significant technological advance of millimeter-wave multiplexer using printed circuit techniques. Results of an extremely wideband H-plane tee with a VSWR of less than 1.4 over the full W-band (75 to 110 GHz) are also presented.

On the design and performance of printed-circuit filters and diplexers for millimeter-wave integrated circuits

This paper describes the design and performance of various millimeter-wave printed-circuit filters and diplexers. These components include microstrip/suspended stripline and finline lowpass filters, capacitive-gap and inductive-iris-coupled bandpass filters, spurline bandstop filters, and finline diplexers. State-of-the-art performances from Ka-band (26.5 to 40 GHz) to D-band (110 to 170 GHz) have been obtained. Agreement between the measured and calculated results was also achieved.

Phased array radar for airborne systems

Phased array antenna systems, which support high pulse rates and high transmit power, are well suited for radar and large-scale surveillance. Sensors and communication systems can function as the eyes and ears for ballistic missile defense applications, providing early warning of attack, target detection and identification, target tracking, and countermeasure decision. In such applications, active array radar systems that contain solid-state transmitter sources and low-noise preamplifiers for transmission and reception are preferred over the conventional radar antennas, because the phased array radar offers the advantages of power management and efficiency, reliability, signal reception, beam steering target detection. The current phased array radar designs are very large, complex and expensive and less efficient because of high RF losses in the phase control circuits used for beam scan. Several thousands of phase shifters and drivers may be required for a single system thus making the system very complex and expensive. This paper describes the phased array radar system based on high power T/R modules, wide-band radiating planar antenna elements and very low loss wide-band phase control circuits (requiring reduced power levels) for beam scan. The phase shifter design is based on micro-strip feed lines perturbed by the proximity of voltage controlled piezoelectric transducer (PET). Measured results have shown an added insertion loss of less than 1 dB for a phase shift of 450 degrees from 2 to 20 GHz. The new wideband phased array radar design provides significant reduction in size cost and weight. Compared to the conventional phased array systems, the cost saving is more than 15 to 1.

Pseudo full-duplex phased array antennas

High data rate networks are now being designed to rapidly exchange high value sensor and video information among various users located on the surface and airborne. Phased array antennas can provide rapid switching amongst the members in addition to the gain necessary to connect these members. For many applications, these antennas would be configured to either transmit or receive. Designing a phased array antenna that is full duplex significantly complicates the design because much of the emphasis in the design is placed on keeping the transmit energy out of the receive channel. A phased array antenna could be designed to receive only when the antenna is not transmitting; thus the design would only need to protect the receiver components during the transmission. The antenna would be then full duplex. This paper describes a small pseudo full duplex wideband multi-frequency band (X, Ku and K) phased array antenna with +/-27 degrees of the beam scanning, using a novel multi-line time delay phase shifter controlled by a piezoelectric transducer (PET). This antenna design is simple, and would use no more space than an antenna used solely for either transmit or receive. Also, some of the isolation between the transmit and receive channels is achieved using novel low-cost fabrication techniques.