Error Analysis of a Quadrature Coherent Detector Processor

Sinsky, A.; Wang, Paul C.P.

doi:10.1109/taes.1974.307900

Cited by 30 publications

(8 citation statements)

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“…1 -(1 + e) cos a + j (1 + e) sin a 1 + (1 + e) cos a + j ( l + e) sin a This equation is identical to the equations obtained in the separate analyses carried out by Sinsky & Wang, 1974and Monzingo & Au, 1987. Monzingo & Au, 1987 further showed that contours of constant IS R (using equation 6.11) resemble ellipses in a plot of differential phase error a versus differential gain error 1 + e. (1.6 dB differential gain error) and a zero differential phase error.…”

Section: Is Rsupporting

confidence: 52%

Stepped-frequency radar design and signal processing enhances ground penetrating radar performance

Noon¹

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This thesis presents a theoretical analysis and applied evaluation of the steppedfrequency radar technique and shows that significant performance benefits can be achieved in ground penetrating radar (GPR) applications. These benefits are suc cessfully demonstrated in field trials of a newly designed stepped-frequency GPR system.An original contribution has been made in establishing a unified characterisation of the performance of GPR for constant Q materials. This enables the maximum penetration depth of a GPR system to be characterised as a fixed number of wave lengths which is constant for any frequency. Similarly, the resolution is expressed as a fixed number of wavelengths which is also constant with frequency. These expressions prove to be a useful design tool in characterising GPR performance in dependently of frequency, and in selecting the waveform parameters for a defined application.A rigorous theoretical study of the stepped-frequency radar technique is un dertaken, which demonstrates the "synthesis" of an impulse waveform using an IDFT-based matched filter with minimum-phase. It is concluded that a physically realisable stepped-frequency radar has far-reaching benefits in the form of higher processed mean energy than an impulse radar with the same frequency bandwidth.A 1-2 GHz stepped-frequency GPR prototype has been completely designed and built to test the above theories. The primary application for this system design is the high-resolution mapping of thin coal seam structures in open-cut coal mines.The 1-2 GHz frequency band is selected to meet the performance requirements of one metre penetration and five centimetre resolution in coal.A novel technique is presented which corrects the broadband quadrature receiver errors in the stepped-frequency radar prototype. It is shown that the technique suppresses the Hermit,Ian images by more than 50 dB below the target responses.The external loop gain of the system is measured to be 156 =b 6 dB for bow-tie antennas and 166 dz 6 dB for horn antennas. These figures represent the maximum power loss that the radiated signal, integrated over a defined ten millisecond interval, can tolerate between the transmit and receive antennas, for a defined signal-to-noise ratio of 10 dB. The performances of typical impulse GPR systems are noted in the literature to lie between 100-130 dB under similar conditions.The system is successfully field tested at various sites, including two open-cut coal mines. The resulting images from these sites demonstrate a penetration depth of at least 80 centimetres and a resolving power of better than 8 centimetres.

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Section: Is Rsupporting

confidence: 52%

Stepped-frequency radar design and signal processing enhances ground penetrating radar performance

Noon¹

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“…The system error of the digital coherent quadrature sampling system is relatively small; nevertheless, it still needs accurate measurement of the system error for error correction and increasing the improvement factor. Therefore, it is of concern to calculate the amplitude error and phase error for both analog and digital coherent quadrature sampling system.Computation method for computing the mirror image level, the relative gain error and phase error, and the effective number of bits (ENOB) and the signal to noise ratio (SNR) of A/D converter (ADC) are, respectively, given in [1][2][3]. The method presented in [1] gives an estimation of the relative amplitude error and the phase error for N samples.…”

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confidence: 99%

“…Computation method for computing the mirror image level, the relative gain error and phase error, and the effective number of bits (ENOB) and the signal to noise ratio (SNR) of A/D converter (ADC) are, respectively, given in [1][2][3]. The method presented in [1] gives an estimation of the relative amplitude error and the phase error for N samples.…”

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confidence: 99%

Error estimate of quadrature sampling system via discrete Hilbert transform

Liu¹,

Huang²,

Zhao³

et al. 2010

2010 2nd International Conference on Signal Processing Systems

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Pulse Doppler radar needs accurate measurement of the quadrature sampling system error for error correction to reduce false alarm rate and improve the clutter suppressing performance and the improvement factor. This paper firstly introduces the discrete Hilbert transform to estimate the relative amplitude error and phase error of quadrature sampling system using coherent testing signa1. The error function with respect to each sample is derived theoretically. Computer simulation shows that the theoretical results are effective and accurate. The results can be used to evaluate and correct the errors in the quadrature sampling system to contribute to suppress the background moving clutter and reduce false alarm rate for the pulse Doppler radar.Keywords-relative amplitude error; phase error; error estimate; quadrature sampling system; discrete Hilbert transform I. 0BINTRODUCTION Quadrature sampling system is responsible for converting intermediate frequency (IF) signals into two orthogonal zero-IF digital signals, i.e., inphase and quadrature (I/Q) channel signals. Ideally, the amplitude of I/Q Channels should be equal, and the phase difference between I/Q channels should be 90 0 , and the DC offset should be zero. Unfortunately, perfect balance of amplitude as well as phase of I/Q Channels is nonexistent in an actual system. In an analog coherent quadrature sampling system, due to environmental changes and device aging, the phase error can reach up to 1 0~50 , and the relative amplitude error can reach up to 0.1dB ~ 1dB. The resulting relative mirror image is between -20dB ~-30dB [1]. The existence of the mirror image level will directly restrict the improvement factor, increase the false alarm rate and reduce the clutter suppressing performance of pulse Doppler radar. The system error of the digital coherent quadrature sampling system is relatively small; nevertheless, it still needs accurate measurement of the system error for error correction and increasing the improvement factor. Therefore, it is of concern to calculate the amplitude error and phase error for both analog and digital coherent quadrature sampling system.Computation method for computing the mirror image level, the relative gain error and phase error, and the effective number of bits (ENOB) and the signal to noise ratio (SNR) of A/D converter (ADC) are, respectively, given in [1][2][3]. The method presented in [1] gives an estimation of the relative amplitude error and the phase error for N samples. In this paper, we present a novel method utilizing the discrete Hilbert transform for estimating the relative amplitude error and the phase error, which will give estimation per sample. II. 1BDISCRETE HILBERT TRANSFORMIn the continuous case, the Hilbert transform of a real signal ( )x t is defined aswhere ˆ( ) x t is the Hilbert transform. The Fourier transform of the Hilbert transform is given by [5] where 1 for >0 ( ) 0 for 0 1 for <0 sgn and ( ) X is the Fourier transform of ( ) x t . We associate ( )x t with a complex signal ( ) c x t , defined as...

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“…Another error results from DC offsets introduced during the analog-to-digital conversion of the I and Q signals. These errors are particularly serious in coherent radar systems where they yield spurious sidebands at the image doppler frequency [2]. Consequently, digital approaches for performing quadrature demodulation on a digitized IF signal have attracted attention.…”

Section: Introductionmentioning

confidence: 99%

“…The matching of the frequency responses is very important because it determines the phase erro'r/image suppression performance that is obtainable [2]. This paper presents a new approach where the problem of matching the frequency responses is considered in the filter design methodology.…”

Section: Introductionmentioning

confidence: 99%