B.P. Kumar

Design of unequally spaced arrays for performance improvement

Classical antenna array synthesis techniques such as Fourier, Dolph-Chebyshev and Taylor synthesis efficiently obtain array current distributions for equally spaced arrays that generate a desired far-field radiation pattern function or keep important parameters like beamwidth and sidelobe level within prescribed performance bounds. However, the concept of optimization of the field pattern (e.g., by decreasing sidelobes or beamwidth) of an given equally spaced array realization by altering its element spacings still represents a challenging problem having considerable practical advantages. These include reduction in size, weight, and number of elements of the array. This paper describes a new approach to synthesis of unequally spaced arrays utilizing a simple inversion algorithm to obtain the element spacings from prescribed far-zone electric field and current distribution, or current distributions from prescribed far-zone electric field and element spacings.

The far-field of a spherical array of point dipoles

In this paper, the far-field of a spherical array of point dipoles is related to the array currents in an elegant manner by invoking the properties of the associated Legendre functions. The inverse problem, viz., determining the array currents from the far-field data is solved in a recursive manner thereby precluding the need for a matrix inversion. >

A reduced size planar balun structure for wireless microwave and RF applications

An extremely important component in the realization of certain RF and microwave system topologies is the high frequency balun network. In addition to its application in radiating structures, it has broad utility in numerous wireless communication system topologies. This paper describes a small and compact coupled microstrip line design for use primarily in the exploding portable wireless market. The main advantage of the design to be discussed is that its size is considerably smaller than traditional planar circuit realizations. Size reduction is achieved by utilizing the property of effective length enhancement of a transmission line by employing additive capactive effects. The design technique is illustrated by presentation of computed and measured data on a /spl sim/0.9 GHz realization developed for wireless applications.

Near-field analysis of spherical loop arrays

In a recent paper (see ibid., vol.42, p473-7, April 1994), the authors presented the development of an algorithm for the reconstruction of element currents of a spherical loop array given the far-field pattern data in an azimuthal plane, and demonstrated the validity of the method with several computational examples. In this letter, it is shown that the same algorithm can be applied to the reconstruction of the spherical loop-array currents from the near-field data by application of spherical wave expansion of the electric field integral of the array. The main feature of the reconstruction algorithm is that the array currents are obtained recursively through the solution of a triangular equation set.

A new technique of analysis of unequally spaced linear arrays

The analysis of unequally spaced (thinned) arrays originated with the work of Unz (1960), and developed later, by Miller and Goodman (1983), with the application of Pronys method to linear array synthesis. A method described earlier by the authors is extended to the analysis of planar arrays. The specific advantage of this algorithm is that the arrays currents are reconstructed in closed form, from a knowledge of limited far-zone electric field data, without the need of general matrix inversion techniques to obtain the array currents.

An improved planar balun design for wireless microwave and RF applications

The high frequency balun network is a vital component in the realization of certain RF and microwave system topologies, especially in wireless communication system architectures. This paper describes an improved compact coupled microstrip line design for use primarily in the exploding portable wireless market. The two main advantages of the design are that its size is a fraction of the standard /spl lambda//4 coupled line design, and that it exhibits an extremely tight coupling of /spl sim/4 dB. The design technique is illustrated by presentation of computed and measured data on a /spl sim/0.9 GHz realization developed for wireless applications.

Radio‐Frequency Multipliers

The sections in this article are 1 Applications of Frequency Multipliers 2 Passive Frequency Multipliers 3 Active Frequency Multipliers

Parametric analysis of improved planar balun circuits for wireless microwave and RF applications

The high frequency balun network is a vital component in the realization of certain RF and microwave system topologies, especially in wireless communication system architectures. This paper describes an in-depth parametric analysis of two planar balun circuits operating in the 900 MHz wireless band. The novel feature of the designs are their compact size which is almost one-tenth of the standard /spl lambda//4 coupled line design. Coupling levels for the two designs are /spl sim/6 dB (with broader bandwidth) for Model 1 and /spl sim/3 dB (with narrower bandwidth) for Model 2. Computed and measured data are presented for coupling performance, and dimensional parametric analysis.

Formulation of the Klopfenstein tapered line analysis from generalized nonuniform line theory

The objective of this problem is to formulate the Klopfenstein analysis of the non-uniform line in the generalized integral equation format. The integral equation approach is a general case without any optimization which gives the equation for reflection coefficient for any tapered line. On the other hand, Klopfenstein uses an optimized reflection coefficient and proceeds to obtain an equation for characteristic impedance in terms of circuit variables. In this paper, the aim is to examine the general formulation analysis of Youla for the non-uniform line, and derive Klopfensteins result for the input reflection coefficient for the line.

Low power consumption voltage controlled oscillator design

Voltage Controlled Oscillators (VCOs) are extremely important components in the exploding field of wireless radio-frequency communications. This paper illustrates the design and fabrication of a unique compact and low power consumption VCO for wireless communication. Subsequent to a description of the design technique, the paper discusses the measured results of a VCO, realized with the design procedure, which was fabricated using lumped components on microstrip dielectric substrate having a dielectric constant of 2.17 and a thickness of 20 mils. Excellent circuit performance is shown to result for very low bias power (1 V, 0.86 mA) values.