Search

High-performance SiGe HBTs and advancements in packaging processes have enabled system-in-package (SiP) designs for millimeter-wave applications. This paper presents a 122-GHz bistatic frequency modulated continuous wave (FMCW) radar SiP. The intended applications for the SiP are short-range distance and angular position measurements as well as communication links between cooperative radar stations. The chip is realized in a 130-nm SiGe BiCMOS technology and is based on a fully differential frequency-multiplier chain with in phase quadrature phase receiver and a binary phase shift keying modulator in the transmit chain. On-wafer measurement results show a maximum transmit output power of 2.7 dBm and a receiver gain of 11 dB. The chip consumes a DC power of 570 mW at a supply voltage of 3.3 V. The fabricated chip is integrated in an embedded wafer level ball grid array (eWLB) package. Transmit/receive rhombic antenna arrays with eight elements are designed in two eWLB packages with and without backside metal, with a measured peak gain of 11 dBi. The transceiver chip size is 1.8 mm × 2 mm, while the package size is 12 mm × 6 mm, respectively. FMCW measurements have been conducted with a sweep bandwidth of up to 17 GHz and a measured range resolution of 1.5 cm has been demonstrated. 2D positions of multiple targets have been computed using two coherently linked radar stations.

This paper presented a rhombic ring monopole antenna with stripline and ring resonator for multiband operation. The antenna is created by adding a stripline in a rhombic ring radiator and placing a ring resonator on the bottom layer of the radiator. It can support the multiple resonant frequencies for wireless communication systems. The antenna dimension is about 36 × 48 mm2. The results confirm the good agreement between simulation and measurement. The antenna operates with |S11| level < −10 dB on impedance bandwidths of 16.11%, 9.8%, and 37.43% at the resonant frequencies of 1.8 GHz, 2.45 GHz, and 3.5 GHz, respectively covering the application bands of LTE 1800, WLAN IEEE802.11b/g, WiMAX and IMT Advance Systems. The radiation patterns are omni-directional at all of operating frequencies and the average gain of the antenna is about 2.4 dBi.

A rhombic grid array antenna (RGAA) is proposed and its frequency-scanning performance is discussed. The RGAA has numerous bent radiation elements, forming rhombic cells and loops. As the frequency is increased, the radiation beam from the RGAA becomes a forward-fire beam. It is found that, as the bend angle of the radiation elements is decreased, the useful antenna characteristics shift to a lower frequency region. It is also found that the RGAA provides a more stable gain within a frequency band bounded by the 3- and 4-guided-wavelength resonances of the loops, compared with a conventional grid array antenna having non-bent radiation elements. Further investigation reveals that the VSWR is small within a frequency band bounded by the 3- and 4-guided wavelength resonances, as desired, and the bend radiation elements of the RGAA contribute to increasing the radiation efficiency.

This letter develops a printed two-element parallel array consisted of dual rhombic loops and a reflecting plate for broadband, high-gain, and circular polarization (CP) operation. An improved mixed feedline network of bud-shape junction is suggested for the parallel antenna array design. The bud-shape junction not only converts the coplanar stripline to the microstrip line, but also expands the impedance-match bandwidth. The dual parasitic rhombic loops are applied to broaden the CP operation bandwidth. The antenna array is simulated and fabricated with good agreement obtained between the simulation and experimental results. The fabricated prototype shows that the bandwidth of AR 12 dB is 18.1%, 18.8%, and 12.1%, respectively. A 2 × 4-array structure is also presented using this bud-shape junction, and it is easy to be expanded to large arrays for high-gain applications.

A Kraus grid array antenna (K-GAA) and a rhombic grid array antenna (RGAA) are investigated as frequency beam-scanning antennas. The fundamental radiation characteristics, including the beam direction and gain, are discussed. The resonance for the RGAA is reduced by adding perturbation elements to the hexagonal loops, thereby enhancing the gain bandwidth.

A NASA research program has been instituted which seeks to replace the present hydraulic and pneumatic control systems on commercial aircraft with electro-optical and electro-mechanical devices. This new technology should be lighter, cheaper, and easier to maintain, but may be susceptible to high-amplitude externally-generated electromagnetic fields. To determine the expected level of interference, a rhombic antenna utilized by the Voice of America for international short-wave broadcasting was modeled using NEC-4D. The predicted gain and take-off angle were calculated, along with the electric-field intensity at several data points located near the ground.

A 77-GHz rhombic antenna as well as a rhombic antenna array designed for automotive radar applications are presented in 6×6mm2 and 12×8mm2 embedded wafer level ball grid array (eWLB) packages respectively. For the sake of antenna characterization, a 2×2mm2 monolithic microwave integrated circuit (MMIC) including a 77-GHz transceiver and a frequency multiplier is integrated in the package. The frequency multiplier generates the eighteenth harmonic of its input signal and scales a 4.25-GHz input signal to a 76.5-GHz output signal. This enables the antenna beam pattern characterization using a commercial signal source. As the dimensions of a single-element antenna in package (AiP) hardly exceeds the dimension of the MMIC, an AiP typically suffers from an asymmetric beam pattern and limited gain. This paper proposes a highly directional rhombic antenna array solution with more than 10 dBi gain and a symmetric beam pattern.

A grid array antenna composed of V-shaped and rhombic elements is proposed. It is found that the beam direction of the proposed antenna with 2α = 60° scans the range of θ = 3° to 31° as a function of frequency. The gain for this scanned beam is almost constant, at approximately 21 dBi.

The Phillips Laboratory has designed and constructed a continuous wave illuminator for studying the responses of large-scale systems subject to vertically or horizontally polarized electromagnetic stresses incident from the horizontal. The illuminator is developed by a nonuniform two-wire transmission line oriented over the system under test. When the wires are driven from a common mode voltage with respect to the ground a vertically polarized electric field is generated and when the wires are driven from equal but opposite voltages a horizontally polarized electric field is developed. The structure is called the rhombic illuminator since the wire configuration is very similar to the rhombic antenna. In order to illustrate the use of the illuminator, data are presented for the illumination field and for the response of an illuminated aircraft recorded at the Phillips Laboratory.

It is reported that a rhombic loop antenna the perimeter of which is about 1.3 lambda /sub 0/( lambda /sub 0/: centre wavelength) can radiate circular polarisation (Morishita and Hirashawa, 1994). This antenna can have a traveling wave type current distribution, which has approximately a constant amplitude and a linearly changing phase. This current distribution is realized by making one point open or loading an infinitely large impedance on the proper position of the loop. In the present paper, two types of single feed dual rhombic loop antennas for circular polarization are proposed. Each antenna consists of two rhombic loops of the same size and is located above an infinite ground plane. The antenna characteristics including axial ratio, current distribution, radiation pattern and input impedance are calculated by the method of moments with respect to the gap position, the rhombus vertex angle and the feed type. The calculated results are in good agreement with the measured data.

In the early days, the rhombic antenna gained favour because of its wide band frequency characteristics. This type of antennas was first introduced in the early 1930's [1], They were used primarily in the HF band. Until recently, travelling wave rhombic antennas have never been seriously considered for the use in the UHF band where they may have many advantages over the standing wave antennas [2]. A previous study [3,4] of the travelling wave V-antennas revealed that these antennas do not lend themselves to increase in the directional gain by increasing the length of the antenna arms indefinitely. This was attributed to the radiation of most of the power from the input end of the antenna leaving relatively low power to be radiated from the far ends. A similar study showed clearly that the end sections of the arms of tubical travelling wave rhombic antennas do not radiate appreciably and the directional gain of the antenna cannot be increased by increasing the arms of the antenna beyond a certain limit.

A four rhombic loop antenna for circular polarisation is proposed. This antenna has a high gain of about 9.7 dBi and a broad beam of more than 130° half power beam width. Four parasitic loops are added inside the original four loops to increase the axis ratio bandwidth. A broadband balun is incorporated into the antenna for impedance matching. Details of the antenna design and experimental results are presented.

A nonuniformly spaced array of 25 side-terminated vertical half rhombics is synthesized for the entire high-frequency band. The array is to be used for both transmitting and receiving, as a sky-wave Doppler radar for sea scatter measurements. The array has the capability for providing a maximum transmitting-receiving product gain in the order of 60 dB at low take-off angles, a product azimuth pattern with a nominal beamwidth of 2\deg , a 40\deg sectoral coverage, a final product sidelobe level of -38 dB, and a grating-lobe level of -30 dB.

The article of record may be found at http://dx.doi.org/10.1063/1.1721325 The expression for the driving point impedance of a generalized electric circuit as vizualized by the author is partially integrated, and the physical significance of certain terms is discussed in connection with their application to antenna problems. Upon postulating an unattenuated traveling wave as a first approximation to the current along either a terminated rhombic or Vee antenna, a formula is derived for the free space radiation impedance of each. The expression radiation impedance is used for that portion of the driving point impedance which may be determined from the complex power into the external fields. The resistive component of the impedance for the rhombic antenna checks with the radiation resistance as listed by Leonard Lewin in a discussion of a paper by Donald Foster, with Lewin apparently obtaining his formula by the solid angle Poynting vector method.

Rhombic antennas were the first type employed in the study of propagation via ionospheric scatter. By the use of electrically long leg-lengths gains of the order of 20 decibels were obtained. Experimental measurements using model techniques indicated that assumptions usual in the design of rhombic antennas remained valid even for leg-lengths of 25 to 40 wavelengths. In order to obtain a more compact antenna, while retaining the gain, experimental investigation was carried out on corner-reflector and Yagi-types of antennas. By the use of 60 degree corner-reflector and a collinear array, a corner reflector antenna having gain of 19.9 db. was constructed. By exercising care in adjusting the lengths of parasitic elements, a Yagi antenna, 4.2 wavelength, having a gain of 14.2 decibels, was designed. An array of four such Yagis, having a horizontal spacing of 1.8 wavelengths and a vertical separation of 1.6 wavelengths was measured to have a gain of 19.0 decibels. Full scale corner-reflector antennas and Yagi antennas have been erected and have proved to be operationally satisfactory.

In order to install as many radiating circuits as possible in a given area, consideration has to be given to the operation of antennas in proximity to one another. Therefore, mutual coupling between two nested rhombics and the effect of one rhombic on the radiation pattern of the other were measured. For a ratio of antenna sizes of 2 to 1, the presence of either a coplanar or noncoplanar antenna had no influence on the gain and radiation pattern of the reference rhombic. To determine the minimum acceptable separation, measurements were extended to include rhombics almost equal in size and as close as practicable to each other. For wire separations of 0.5\lambda the gain of the reference rhombic was reduced by 0.5 dB. For 0.2\lambda separation the gain was reduced by 1 dB, and for 0.04\lambda it was reduced by approximately 4 dB. Except for very close spacings, the radiation patterns remained substantially unchanged. Mutual coupling, expressed as transmission loss between the antennas in decibels, varied between -15 and -41 dB.

An analysis of the situation in point-to-point radio communication circuits at frequencies below MUF with respect to radiation in undesired directions brings to the fore some aspects which are useful as guide lines in antenna research, design, and application engineering. In many cases, the interference experienced in operating receivers in the high-frequency range can be attributed primarily to the relatively high side lobes of the radiation pattern of rhombic antennas. Progress has been made in suppressing these side lobes through the development of antenna arrays employing nonuniform amplitude distributions and, more recently, through the advent of modified horn-type antennas. Other sources of interference which are usually overlooked are associated with balanced open-wire lines which are not operated properly. Recently, it has become feasible to replace these lines by coaxial cable using broad-band balun transformers.

The expression of the field radiated by a rhombic antenna, taking into consideration both the vertical and the horizontal polarization components, is used to establish the theory of the array of two stacked rhombics and of the array of four rhombics in a stacked and interlaced arrangement. The main conclusions obtained are that for convenient values of the vertical and horizontal spacings between the antennas of the array, there is a greater concentration of power radiated along the directions of the main lobe of the pattern and, as a result, these arrays show an appreciable gain over a conventional rhombic. Practical rules for the design of these arrays for point-to-point and broadcasting are given in some detail.

A direct theoretical determination of the transmitting properties of the horizontal rhombic antenna and of the closely related inverted V structure has been made. Expressions are given for the intensity of the radiation, the polarization, the radiation resistance, and the gain. The intrinsic simplicity of the radiation distribution functions is revealed by graphical representation. Stereographic representation also supplements the analysis and provides clear insight into the effects available through variations of design, and enables the essential features of a specific design to be obtained for all directions with a very small amount of labor. Methods of diminishing the relative intensity of radiation from subordinate lobes are considered.

In this letter, the effect of terminating resistance loss in the case of rhombic antennas has been studied. Generalized analysis has also been made to compute the radiation pattern of rhombic antennas with the log periodic dipole array termination. Theoretical radiation patterns are plotted and it is observed that this new method improves the directivity and lowers the sidelobe level.