GB1268634A - Improvements in or relating to radio distance measuring equipment - Google Patents
Improvements in or relating to radio distance measuring equipmentInfo
- Publication number
- GB1268634A GB1268634A GB1760968A GB1760968A GB1268634A GB 1268634 A GB1268634 A GB 1268634A GB 1760968 A GB1760968 A GB 1760968A GB 1760968 A GB1760968 A GB 1760968A GB 1268634 A GB1268634 A GB 1268634A
- Authority
- GB
- United Kingdom
- Prior art keywords
- mixer
- signal
- oscillator
- outputs
- delay
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
- G01S13/342—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using sinusoidal modulation
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
1,268,634. Radio altimeter. T. G. THORNE. 3 July, 1969 [11 April, 1968], No. 17609/68. Heading H4D. Specification describes a radio altimeter comprising, Fig. 4, a transmitter 30 radiating a signal frequency modulated at frequency P by means of oscillator 31, a receiver 33 for receiving Doppler frequency shifted reflections of the transmitted signal, a first mixer 34 arranged to combine the received signal with part of the transmitted signal, tuned amplifier means 35 for selecting from the output of mixer 34, one of the pair of component signals centred about the harmonic nP of the modulation frequency P, second and third mixers 36 and 37 for combining the selected signal from the first mixer with respective signals of frequency nP derived from the modulation oscillator 31, but having different phase shifts and means responsive to the ratio of the amplitudes of the outputs from the second and third mixers at the Doppler frequency d to produce a signal indicative of the range between the transmitter/receiver and reflecting surface. In the described embodiment n = 1 and the outputs of mixers 36 and 37 are respectively where: f o = carrier frequency, m = modulation index, J 1 = Bessel function of first kind and first order, T = propagation time, # 1 = delay imparted to output of oscillator 31 by delay 40, # 2 = delay imparted to output of oscillator 31 by delay 41. The delay imparted by tuned amplifier 35 is cancelled by phase shifters 38 and 39. The manner in which the ratio of their outputs, i.e. Sin(#pT + # 1 )/Sin(#pT + # 2 ), varies with the range dependent #pT, is shown in Fig. 3 for various values of # 1 and # 2 . Rather than determine the ratio directly, an AGC system 47 varies the amplification of amplifier 35 so that the amplitude of signal 37 out remains constant and the amplitude of signal 36 out thus represents said ratio, and, from the known relationship of Fig. 3 also said range. Each of the signals 36 out and 37 out are synchronously detected in respective mixer/detectors 44/45 using the other signal as reference, to produce outputs representing said amplitudes. The output of mixer/detector 45 is thus fed to the AGC system 47 and the output of mixer/ detector 44 is fed to altitude indicator 50. As seen in Fig. 5 range ambiguity occurs when (#pT+ # 2 )##. To determine that this ambiguous state is not prevalent, the modulation frequency P is itself frequency modulated by oscillator 51. This causes the characteristic curves of Fig. 5 to shift from the solid to the dotted line positions. The observed change in the ratio value is very much larger for the ambiguous curves than for the correct (first) curve, and this criterion can be detected in a fault logic circuit 53. The correct operation of the altimeter is monitored by means of an artificial signal injected into the receiver by means of a line from the transmitter via a range simulating delay line 54, with a delay T<SP>1</SP>, a Doppler frequency shift simulating oscillator 65 and a variable attenuator 56 controlled by AGC 47 such that the amplitude of the artificial signal is equal to a normal echo signal. The oscillator 55 is chosen such that the simulated Doppler shift at the outputs of mixers 36 and 37 is rejected by filters 42 and instead is selected by filters 57 and 58 to mixer/detectors 59 and 60 operating similarly to mixer/detectors 44/45. The outputs of the mixer detectors 59, 60 are connected to an amplifier 63 via resistors 61, 62 having values R 1 , R 2 such that Since the outputs of mixer/detectors 59/60 are of opposite polarities, correct working of the altimeter is indicated by zero voltage at the amplifiers, and this is achieved by feeding the amplifier output as a control signal for variable phase shifter 39. The output of mixer/detector 59 and the input of amplifier 63 are fed to logic circuit 53. To check the calibration of meter 50, oscillator 64 is substituted for oscillator 69, such that the simulated Doppler frequency shift is passed by filters 42/43 and the delay T<SP>1</SP> registers on 50. Logic circuit 53 has three flag outputs 66, 67, 68 respectively indicating, " correct operation ", " altitude indication is ambiguous ", " incorrect (failure operation) ".
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1760968A GB1268634A (en) | 1968-04-11 | 1968-04-11 | Improvements in or relating to radio distance measuring equipment |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB1760968A GB1268634A (en) | 1968-04-11 | 1968-04-11 | Improvements in or relating to radio distance measuring equipment |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1268634A true GB1268634A (en) | 1972-03-29 |
Family
ID=10098136
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB1760968A Expired GB1268634A (en) | 1968-04-11 | 1968-04-11 | Improvements in or relating to radio distance measuring equipment |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB1268634A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1989002605A1 (en) * | 1987-09-17 | 1989-03-23 | The Singer Company | Closed loop velocity/altitude sensor for fm-cw doppler radars |
CN102778241A (en) * | 2012-07-31 | 2012-11-14 | 清华大学 | Echo simulator and simulated echo generating method of universal airborne radio altimeter |
-
1968
- 1968-04-11 GB GB1760968A patent/GB1268634A/en not_active Expired
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1989002605A1 (en) * | 1987-09-17 | 1989-03-23 | The Singer Company | Closed loop velocity/altitude sensor for fm-cw doppler radars |
CN102778241A (en) * | 2012-07-31 | 2012-11-14 | 清华大学 | Echo simulator and simulated echo generating method of universal airborne radio altimeter |
CN102778241B (en) * | 2012-07-31 | 2014-09-10 | 清华大学 | Echo simulator and simulated echo generating method of universal airborne radio altimeter |
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