22-09-2012, 02:32 PM
Smart Antenna UKM Testbed for Digital Beamforming System
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ABSTRACT
A new design of smart antenna testbed developed at UKM for digital beamforming purpose is proposed. The smart antenna
UKM testbed developed based on modular design employing two novel designs of L-probe fed inverted hybrid E-H (LIEH)
array antenna and software reconfigurable digital beamforming system (DBS). The antenna is developed based on using the
novel LIEH microstrip patch element design arranged into 4 × 1 uniform linear array antenna. An interface board is designed
to interface to the ADC board with the RF front-end receiver. The modular concept of the system provides the capability to test the
antenna hardware, beamforming unit, and beamforming algorithm in an independent manner, thus allowing the smart antenna
system to be developed and tested in parallel, hence reduces the design time. The DBS was developed using a high-performance
TMS320C6711TM floating-point DSP board and a 4-channel RF front-end receiver developed in-house. An interface board is
designed to interface to the ADC board with the RF front-end receiver. A four-element receiving array testbed at 1.88–2.22 GHz
frequency is constructed, and digital beamforming on this testbed is successfully demonstrated.
Introduction
Smart antenna with digital beamforming (DBF) is regarded
as one of the key components to meet the ever increasing
appetite for higher data rates. Smart antenna technology
dramatically improves the interference-suppression capability
and greatly increases frequency reuse, resulting in
increased capacity. Smart antenna with its beamforming
capability optimizes the signal-to-noise performance or
power consumption at both ends of the links. Advancement
in powerful low-cost digital signal processor (DSP), generalpurpose
processors, field programmable gate array (FPGA),
application-specific integrated circuits (ASICs), as well
as innovative software-based signal processing techniques
(algorithms) or software-defined radio (SDR), has allowed
the development of smart antenna system to progress
rapidly and make the smart antennas practical for cellular
communications systems [1].
System Architecture and Hardware
Implementation
The novel SATB developed at UKM (UKM testbed) is
developed based on modular concept employing two novel
designs of four-element microstrip patch antenna array and
DSP-based DBS, which allows the exploitation of digital
beamforming. The testbed is designed as a receiver unit. A
block diagram of UKM testbed receiver system architecture
is shown in Figure 1. The testbed receiver system composed
of antenna system, radio unit, and digital signal processing
baseband section.
Measurement Results and Discussions
A testbed is set up in the microwave lab to evaluate system
performance. The DBF measurement result is presented
in this section. A single-tone test is performed for the
evaluation of the UKM testbed performance. An Agilent
54622 D-mixed signal digital oscilloscope is used after the
LPF to observe the baseband signal waveform. Figure 9 shows
the experimental setup for the evaluation of beamforming
algorithm.
Conclusion
This design and development of UKM testbed, capable of
performing digital beamforming that employed LIEH array
antenna operating at 1.88 GHz–2.22 GHz and DSP based
DBS, have been presented in this paper. The UKM testbed
has been designed in a modular manner, which simplifies
the design, reduces the development time, eases hardware
update, and facilitates testing the various modules (e.g.,
antenna hardware, beamforming unit, and beamforming
algorithms) in an independent manner.