Radar Technology for Level Gauging - Krohne

More documents

Recommendations

Info

3. Radar-Füllstandsmesssysteme However, a situation to be avoided is for the operating frequency to be distinctly higher than the cut-off frequency f c, since then higher modes can also be propagated at a different velocity: which is slower than in free space. The cut-off wave length λ c for individual modes in a circular waveguide is, for example: Typ H 11 E 01 H 21 E 11/H 01 E 21 H 12 λ c /D 1.706 1.306 1.029 0.820 0.612 0.589 At GHz frequencies, the transmission losses of a waveguide are lower than those in coaxial cables or twin lines. 4.4.6 Coupling into waveguides A coupling device is required for transition from the double-line transmission path (e.g. coaxial cable) to a waveguide, e.g. a so-called pin coupler. In addition, there are various possibilities for planar coupling – directly from the PCB to the waveguide. waveguide sheath air upper side lower side PCB coaxial connection pin coupler waveguide waveguide Radar handbook 21 4 Fig. 15: Waveguide (left) and coupling into waveguide (right) Fig. 16: Planar waveguide coupling with fin line (left) or in radial arrangement (right)
4 Fig. 17: Examples of planar directional couplers [Pehl.1] 4.4.7 Directional coupler A directional coupler transforms only such waves along a second line structure that are transmitted in a predetermined direction along the first line. For single-antenna systems it needs to be fitted in front of the antenna connection in order to decouple the received signal and separate it from the transmission signal, since both signals are present simultaneously at the coupling point. P 3 P 1 3 4 1 2 P≈0 P 2 The characteristic of the planar structures shown in Fig. 17 is that a wave (P 1 fed into a gate is transmitted only to 2 gates (P 2 and P 3) while the 4th gate remains largely without power (P = approx. 0). The same applies analogously when a wave is fed into another gate. For example, in the system shown in Fig. 8, the transmission amplifier could be connected to gate 1, the antenna to gate 2, and the receiver mixer to gate 4. Gate 3 is not used and must feature a non-reflecting termination. By this means the high-energy transmission signal is not transmitted to the sensitive mixer. 4.4.8 Reflections at junctions At every junction in a conductor (particularly in waveguides) at which the cross-sectional geometry or the dielectric material changes, the natural impedance will also change, so that unwanted reflections can occur at these points. For that reason suitable design measures are necessary at junctions in order to keep reflections as small as possible. Where there is a junction between one line structure with natural impedance Z 1 and another line with Z 2 we obtain the following voltage reflection factor r: 22 Radar handbook P≈0 P 1 4 1 3 2 P 3 P 2
Page 1 and 2: © KROHNE 07/2003 7.02337.22.00 GR
Page 3 and 4: Content page 1 Introduction 5 1.1 R
Page 5 and 6: Symbols used a Distance, spacing
Page 7 and 8: 2 2. General 2.1 Frequency, wavelen
Page 9 and 10: 2 3. Radar-Füllstandsmesssysteme 2
Page 11 and 12: 3 Fig. 3: Geometric configuration o
Page 13 and 14: 3 Fig. 5: Pulse radar measuring sys
Page 15 and 16: 3 Fig. 8: Basic circuit diagram of
Page 17 and 18: 4 4. Components for radar systems F
Page 21: 4 Fig. 14: Planar line 4.4.3 Planar
Page 25 and 26: 5 Fig. 20: Various form of antenna
Page 29 and 30: 6 6. Wave propagation 6.1 Propagati
Page 31 and 32: 6 Fig. 24: Change of propagation ra
Page 35 and 36: 6 6.5 Modified radar equation Based
Page 37 and 38: 6 Fig. 28: Arrangement to measure t
Page 39 and 40: 7 Fig. 31: Reflection factors of di
Page 43 and 44: 7 3. Radar-Füllstandsmesssysteme O
Page 45 and 46: 7 Fig. 35: Influence of the angle o
Page 51 and 52: 8 Fig. 39: Counting method to deter
Page 53 and 54: 8 Fig. 41: A high-pass filter and i
Page 55 and 56: 8 Fig. 44: Subtraction of empty-tan
Page 57 and 58: 8 Fig. 47: Principle of operation o
Page 59 and 60: A Annex A Table of dielectric permi
Page 61 and 62: B B System-theoretical comparison b
Page 63 and 64: B 3. Radar-Füllstandsmesssysteme T
Page 65: C 3. Radar-Füllstandsmesssysteme [

Radar Technology for Level Gauging - Krohne

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?