Figure 1 - uploaded by R.H. Witvers
Content may be subject to copyright.
Source publication
Developments in radio astronomy instrumentation drive the need for lower cost front-ends due to the large number of antennas and low noise amplifiers needed. This paper describes cost reduction techniques for the realization of antennas and low noise amplifiers in combination with a noise budget calculation for array systems in the absence of cryog...
Context in source publication
Context 1
... loss Printed Circuit Board (PCB) materials are expensive, in particular important for the AA systems, and therefore two alternatives have been evaluated to overcome this, one in full metal, and one on polyester foil (Figure 1).The aluminum antenna is laser cut, 1mm thick, and will slide in position in extrusion bars forming a dual polarization grid. A low loss microstrip Duroid PCB feeds the antenna. ...
Citations
... The problem of reducing T n down to T min of a transistor, being a challenge by itself, gets more complicated in ultra-high and super-high frequency ranges since a high dynamic range of the amplifier is required because of intensive broadcasting [6]. The authors' experience with radio telescope RT-70 (Yevpatoria, Crimea AR, Ukraine) has shown that, to avoid intermodulation products in the received signal spectrum at frequencies 327 ± 15 MHz, an amplifier with high dynamic range is needed, having i) an output power 1-dB gain compression point P 1dB >15 dBm, and ii) an output third-order interception point OIP3 >30 dBm. ...
... There is a tendency of avoiding too expensive InP HEMT technology in the frequency range of up to 4 GHz. Instead, SiGe HBT [15], BiCMOS [13], CMOS [5,8] and GaAs E-pHEMT [6] are being implemented. A similar situation is observed with ULNA for 327 MHz (91 cm), where uncooled amplifiers with noise figures of approximately 0.5 dB based on cost-effective commercial devices [1,12] are preferred. ...
An ultra-low-noise input amplifier intended for a use in a radio telescope operating at 91 cm wavelength is presented. The amplifier noise temperatures are 12.8 ± 1.5 and 10.0 ± 1.5 K at ambient temperatures of 293 and 263 K respectively. The amplifier does not require cryogenic cooling. It can be quickly put in operation thus shortening losses in the telescope observation time. High linearity of the amplifier (output power at 1 dB gain compression P1dB ≥ 22 dBm, output third order intercept point OIP3 ≥ 37 dBm) enables the telescope operation in highly urbanized and industrialized regions. To obtain low noise characteristics along with high linearity, high-electron-mobility field-effect transistors were used in parallel in the circuit developed. The transistors used in the amplifier are cost-effective and commercially available. The circuit solution is recommended for similar devices working in ultra-high frequency band.
... The Common Mode (CM) component of the signal in such a system is then rejected by the antenna+balun and/or differential LNA, so that it suffices to optimize the antenna Differential Mode (DM) radiation and impedance characteristics only. However, baluns compromise compactness and increase ohmic losses, thereby reducing the antenna signal-to-noise ratio [1], [2]. ...
... The noise analysis presented in [19] is then applied to the noise-decoupled receivers, of both the SE and MM representations, in order to evaluate the respective receiver noise temperatures. In the analysis to follow, [p, q] denotes either the channels [1,2] The active reflection coefficients of the individual channels/modes are solved by expressing the noise wave at the output of the ideal power combiner -due to the respective 4 channel/mode -as the superposition of three noise wave contributions, i.e., 21 , For identical LNAs, with gains S LNA 21 , the expression in (12) reduces to ...
A theoretical framework for a mixed differential and common mode sensitivity analysis of active receiving antennas is presented, which includes the derivation of a novel set of noise parameters for dual-mode balanced amplifiers. The analysis is applied to an example of a mixed-mode active wire antenna design, consisting of an integrated monopole and dipole structure. Results of numerical simulations and experimental measurements are presented which show that, for a single-polarized design, the judicious use of both differential and common modes enables the field-of-view coverage to be extended over the entire hemisphere with a variation in receiving sensitivity of less than 3dB in the E-plane.
... Introduction: Some modern radio telescopes arrays (such as phasedarray feeds [1] and aperture arrays for the planned SKA [2]) have thousands of low-noise amplifiers (LNAs), making cooling the LNAs very expensive. These systems require extremely low-noise, broadband LNAs, which operate at 77K or even room temperature. ...
... The extra 5K (corresponding to a 0.1 dB loss at the input) is most probably due to the SMA input connector, which was not modelled or may be due to uncertainties in the transistor's noise parameters. In a radio telescope receiver, the connector loss can be eliminated by integrating the LNA with the antenna (for example in [1]). When taking this loss into consideration, the simulated noise is less than 12K and 6K at T amb ¼ 77K and 20K, respectively (assuming the transistor's noise decreases like the square root of the ambient temperature and other noise proportional to the temperature). ...
... Comparison: The APERTIF prototype [1] uses a similar Avago GaAs transistor and achieves T lna , 40K and S 11 , 27.5 dB for 1 -2 GHz. On the other hand, Miteq has a commercial LNA [6] with T lna , 28K and S 11 , 210 dB but its power consumption is 2.7 W. ...
A two-path low-noise amplifier (LNA) designed for the planned MeerKAT radio telescope is presented. The LNA has a noise figure (NF) of less than 0.36 dB and input return loss of less than 12 dB from 0.7 to 1.8 GHz. It consumes 100 mW of power and costs about $10 to manufacture.
... APERture Tile In Focus, [17]), which will replace the existing 21 cm single pixel feeds of the Westerbork Synthesis Radio Telescope (WSRT), and should have competitive performance with the present 21 cm cryogenic receiver system. This development resulted in room temperature receivers and LNAs for an APERTIF prototype tile, giving a measured system temperature in the telescope below 68 K for an on-axis beam at 1.4 GHz ([16], [17]), using LNAs with close to 40 K noise temperature ([23]). ...
Aperture arrays have been studied extensively for application in the next generation of large radio telescopes for astronomy, requiring extremely low noise performance. Prototype array systems need to demonstrate the low noise potential of aperture array technology. This paper presents noise measurements for an Aperture Array tile of 144 dual-polarized tapered slot antenna (TSA) elements, originally built and characterized for use as a Phased Array Feed for application in an L-band radio astronomical receiving system. The system noise budget is given and the dependency of the measured noise temperatures on the beam steering is discussed. A comparison is made of the measurement results with simulations of the noise behavior using a system noise model. This model includes the effect of receiver noise coupling, resulting from a changing active reflection coefficient and array noise contribution as a function of beam steering. Measurement results clearly demonstrate the validity of the model and thus the concept of active reflection coefficient for the calculation of effective system noise temperatures. The presented array noise temperatures, with a best measured value of 45 K, are state-of-the-art for room temperature aperture arrays in the 1 GHz range and illustrate their low noise potential.
... The antenna array has 121 tapered slot elements at a pitch of 10 cm. The antenna elements are connected to single-ended LNAs operating at room temperature [4]. The output signals are transported to ground-level over coaxial RF cables. ...
APERTIF (APERture Tile In Focus) is a Phased Array Feed (PAF) system that is being developed for the Westerbork Synthesis Radio Telescope (WSRT) to increase its survey speed with a factor 20. This paper presents an overview of APERTIF and measurement results that demonstrate the unique capabilities of PAFs in practice: Wide field of view (scan range), low system temperature, excellent illumination efficiency, synthesis imaging and a significant reduction of the reflector feed interaction.
... It is therefore essential to include El as a parameter in the simulation scenarios of radio telescopes.Fig.1 presents the first set of simulation results for the axisymmetric reflector with F/D=0.34-0.5 for the case when the antenna operates at 5.6 GHz.Fig.1 (a) shows the aperture efficiency including its spillover and illumination components andFig.1 (b This maximum is the result of trade-off between high antenna efficiency of shallow-and low noise performance of deep reflector antennas. For the cooled and un-cooled receiver systems with T rec ranging from 20 to 30K78, the optimal F/D is equal to 0.40. For very high performance receivers with T rec <10K, the optimal F/D value is smaller (0.34) due to comparable contributions of T a and T rec to the total system noise. ...
A concept of an axi-symmetric dish as antenna reflector for the next generation radio telescope - the Square Kilometre Array (SKA) - is presented. The reflector is based on the use of novel thermoplastic composite material (reinforced with carbon fibre) in the context of the telescope design with wide band single pixel feeds. The baseline of this design represents an array of 100's to 1000's reflector antennas of 15-m diameter and covers frequencies from <1 to 10 GHz. The purpose of our study is the analysis of the production cost of the dish and its performance in combination with a realistic wideband feed (such as the 'Eleven Antenna' feed) over a wide frequency band and a range of elevation angles. The presented initial simulation results indicate the potential of the proposed dish concept for low-cost and mass production and demonstrate sensitivity comparable to that of the presently considered off-set Gregorian reflector antenna with the same projected aperture area. We expect this observation to be independent of the choice of the feed, as several other single-pixel wideband feeds (that have been reported in the literature) have similar beamwidth and phase center location, both being rather constant with frequency.
... The latter will be preferred in view of the higher degrees of freedom it offers. In both cases, low-noise amplifiers, as studied by several teams in the world [7], [14][15][16] can be integrated inside the present feed system. ...
The design of a broadband antenna feed system for the cylindrical offset parabolic reflector of the Italian Northern Cross radio telescope is described. Its operative frequency band spans from the Low Frequency Array (LOFAR) upper band, i.e. 120-240 MHz, to the present telescope operative band centered at 408 MHz. The proposed configuration consists of a linear array of gridded Vivaldi (tapered slot) radiators inside a wired subreflector. Numerical simulations have been carried out using both commercial software and a specialized Method-of-Moments approach. They show that the designed feed system provides both a good impedance matching and an efficient illumination of the main reflector in the overall frequency band.
... More concretely, the midfrequency band, which ranges from 300 MHz to 1 GHz, is intended to be covered by a dense array of millions of cheap tapered slot antenna (TSA) elements, with scanning capabilities up to 45 . For this purpose, many research groups are currently working in the development of small array demonstrators in order to validate all the technologies that will be necessary for the final implementation of the SKA telescope (e.g., [2]–[5]). The TSA elements (i.e., Vivaldi or bunny-ear antennas [6]) are balanced antennas that must be fed in a differential way. ...
In this paper, differential low-noise amplifiers are presented as a very powerful solution for radio astronomy applications. A fully differential amplifier topology has been analyzed and implemented in microstrip technology with discrete surface mount components. The amplifier design is made for an active receiving dense antenna array. Thus, the differential amplifier source impedance is no longer 50 Ω, but 150 Ω from the proposed bunny-ear antennas. A full characterization in terms of gain and noise has been undertaken. Source-pull measurements have been included in order to evaluate the performance of the amplifiers operating with variable source impedances. Noise temperatures below 55 K have been obtained for the differential design in the 300-1000-MHz band for the 150-Ω impedance. In addition, the results for different scanning angles are also presented.
... We point out that the differential antenna outputs require an interface to differential receiver technology. For this purpose, separate (design) studies are ongoing with the objective to achieve an optimal low-noise low-cost differential amplifier design [5]. The construction of the array is described in II. ...
This paper describes the preliminary design results of a differentially fed tapered slot antenna. Traditional unbalanced tapered slot antennas often employ a bilateral strip line feed, or a separate feed board, in combination with a potentially lossy radial stub and microstrip line (balun). In order to reduce the associated transmission line losses, a differentially fed tapered slot antenna is considered. Main focus is on the measurement procedure and the determination of the active reflection coefficient. The properties of the (undesired) common modes are also discussed. Finally, the effective area for broadside is determined and turned out to be larger than 80% of the physical aperture area of the array.
