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The significant aspect of the prototype switch is the topology of the PC board applied and the connectors for connecting TDR probes and a needle pulse from the generator similar to the one described by Malicki and Skierucha [59]. So as to minimize the impedance discontinuities along the way of the high frequency signal propagation from the generator to the probes, the strip lines of the PC board had 50 Ω impedance. The picture displaying the both sides of the PCB board with the applied integrated circuit and radio frequency connectors of SMA type is presented in Fig. 46. This value was equal to the impedance of the coaxial cables to the TDR probes and the generator. Also the precise SMA connectors were used. The PC board was prepared on three layer FR4 laminate, where the middle layer was connected to the system ground. The middle layer was used so as to decrease the 50 Ω strip line width and to make the PC board mechanically resistant. Fig. 46. Prototype one-to-eight microwave switch for the application in TDR soil water content meter 10.5. Performance of the developed RF switches in TDR applications Fig. 47 presents the comparison of the signals at the input and output of the prototype SP16T switches. The GaAs switch attenuates the input about 2.9 dB and the reed-relay switch – 3.3 dB. These values are in agreement with the catalogue data, taking into account that the total signal attenuation of the ST16T switch is equal to the sum of attenuations (in decibels) from each of four levels shown in Fig. 44. The switches degrade the frequency response of the input signal According to Eq. (83) the 103
upper frequency limit 1.75 GHz decreased to 1.4 GHz and 1.5 GHz after passing the reed-relay and GaAs switches, respectively. Fig. 47. Input pulse and output pulses from the tested SP16T switches The comparison of reflectograms showing the reflections of the initial pulse from TDR probe in the soil, in the cases then there was no and with the switches connected, are presented in Fig. 48. Fig. 48. The reflected signal attenuation introduced by the prototype reed relay and MMIC GaAs switches when the TDR probe was inserted into dry (left picture) and wet (right picture) sand The reflections are more sharp and higher amplitude when there is no switch along the signal propagation path. The upper limit of the frequency range is lower for the reed relay switch because the reflected signals are less sharp than in the MMIC GaAs switch. However in both cases the reflections from the TDR probes are easily distinguishable even in dry sand. It should be stressed that before the reflected signal produced by the generator is sampled, it must travel through the switch two times, towards the TDR probe and back to the sampling head. Therefore in the case of materials that attenuate the TDR signal (saline soils) the reflection from the TDR probe end will not be 104
Page 2 and 3:
TDR METHOD FOR THE MEASUREMENT OF W
Page 4 and 5:
PREFACE The importance of water for
Page 6 and 7:
CONTENTS 1. Status of water as an s
Page 8 and 9:
12.2. New prototype version of FOM/
Page 10 and 11:
that stimulate the phenomena and pr
Page 12 and 13:
The solution to the problem of elec
Page 14 and 15:
3. ELECTRICAL MEASUREMENTS METHODS
Page 16 and 17:
v = c 1 2L = = ( θ ) n ∆t ε (2)
Page 18 and 19:
The TDR probe consists of two waveg
Page 20 and 21:
ε a =1 and φ=0.5 the Eq. (10) has
Page 22 and 23:
The experiment description is given
Page 24 and 25:
Results obtained with the discussed
Page 26 and 27:
Notice that at C s = 0, ie when dis
Page 28 and 29:
water orientation polarization [s],
Page 30 and 31:
Fig. 8. Frequency dispersion of the
Page 32 and 33:
The measurements were performed in
Page 34 and 35:
5. EVALUATION OF DIELECTRIC MIXING
Page 36 and 37:
ε α = ∑V α iε i (29) i where
Page 38 and 39:
where SAND and CLAY are percents of
Page 40 and 41:
Below the transition value, the soi
Page 42 and 43:
To verify the observations concerni
Page 44 and 45:
6. TEMPERATURE EFFECT ON SOIL DIELE
Page 46 and 47:
chamber and the freezer, only one w
Page 48 and 49:
The user interface on the main comp
Page 50 and 51:
soil sample volumetric water conten
Page 52 and 53:
close vicinity of the analyzed obje
Page 54 and 55: process of measurement is non-destr
Page 56 and 57: dielectric permittivity change caus
Page 58 and 59: The values of the refractive index
Page 60 and 61: The relative, ∆n/∆T, and absolu
Page 62 and 63: Fig. 25. The temperature effect on
Page 64 and 65: The temperature effect of TDR soil
Page 66 and 67: The purpose of the above discussion
Page 68 and 69: ( ,25 + T )( 45 + T ) 49 9 f rel =
Page 70 and 71: 8. THE ACCURACY OF SOIL WATER CONTE
Page 72 and 73: gravimetric method and the soil ref
Page 74 and 75: where: a 0 ÷ a 6 are coefficients
Page 76 and 77: values of p F calculated for the re
Page 78 and 79: eason of this is the fact that wate
Page 80 and 81: 9 ∆θ = 0,2 ⋅10 ⋅ ∆t = 0.00
Page 82 and 83: values of θ rel for lower values o
Page 84 and 85: 9. COMPARISON OF OPEN-ENDED COAX AN
Page 86 and 87: ε" = EC ε d " + (82) 2π fε wher
Page 88 and 89: dielectric permittivity, the dielec
Page 90 and 91: The applied lumped capacitance mode
Page 92 and 93: stainless steel wires soldered to t
Page 94 and 95: ε’ Open Coax and ε b-TDR , exce
Page 96 and 97: − − The difference of the imagi
Page 98 and 99: Integrated Circuit) recently introd
Page 100 and 101: 10.2. Electromechanical microwave s
Page 102 and 103: RF1. Two PIN diodes in series in ea
Page 106 and 107: visible for lower values of soil el
Page 108 and 109: In the TDR method the signal propag
Page 110 and 111: description of functional and techn
Page 112 and 113: MASTER modules are wireless transce
Page 114 and 115: time the Real Time Clock module wak
Page 116 and 117: ase station distinguishes A SLAVE d
Page 118 and 119: sensor, format the data received fr
Page 120 and 121: 12. SOIL WATER STATUS MONITORING DE
Page 122 and 123: D-LOG/mpts is a moisture/pressure/t
Page 124 and 125: For compatibility reasons it uses t
Page 126 and 127: D-LOG/mts (Fig. 59) is a TDR (Time-
Page 128 and 129: 12.4. FP/m, FP/mts - Field Probe fo
Page 130 and 131: inside of a separate polyethylene b
Page 132 and 133: differential water capacity and the
Page 134 and 135: − maximum number of LP/p probes t
Page 136 and 137: 12.7. LP/t - Laboratory Probe for s
Page 138 and 139: From the collected data set, after
Page 140 and 141: 25. de Loor G.P.: Dielectric proper
Page 142 and 143: TDR. Symposium on Time Domain Refle
Page 144 and 145: 100. Whalley W.R.: Considerations o
Page 146 and 147: Fig. 14. Fig. 15. Fig. 16. Fig. 17.
Page 148 and 149: Fig. 38. The three-rod TDR probe -
Page 150 and 151: Fig. 67. A set of LP/ms and LP/p LO
Page 152: Table 17. An example of the executa
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