CN1138701A

CN1138701A - Single ring discrete echo analog device of radar altimeter

Info

Publication number: CN1138701A
Application number: CN 96102455
Authority: CN
Inventors: 吴季; 林林
Original assignee: National Space Science Center of CAS
Current assignee: National Space Science Center of CAS
Priority date: 1996-03-04
Filing date: 1996-03-04
Publication date: 1996-12-25

Abstract

A single-loop discrete echo simulator for radar altimeter is composed of 3 direction couplers (one for backward use and two for forward use), adjustable gain amplifier, limiter, band-pass filter, rectifier, loop gain controller and limit level controller of limiter. Adjusting the gain of adjustable gain amplifier can change the amplification factor ofloop in positive gain state to control the slope of leading edge of echo. Regulating limit level controller can change the peak power of simulated echo signal, so different reflection effects for different sea surfaces are simulated.

Description

Single ring discrete echo analog device of radar altimeter

The invention belongs to radar altimeter calibration technology field.

Radar altimeter is to improve rapidly and a kind of multifunction microwave remote sensor that grows up in recent years.It measures height, wave height, the sea backscattering coefficient of flying platform to the sea by launch a chirp pulse signal to the sea, thereby inverting sea wind speed and other various physical parameters are the strongest remote sensing instruments that are used for studying the ocean dynamics feature at present.

Echo simulator is that altitude gauge is calibrated essential instrument.At present, common echo simulator is made up of two parts: first is the time delay circuit that is used for producing time-delay, and second portion is to be used for the echo simulator of analog sea reflecting effect.The generation time delay is optional to be easier to realize with optical fiber or SAW (Surface Acoustic Wave) device ratio, and the effect of analog sea reflection is wanted the many of difficulty.Existing echo simulator normally adopts the mode of serial or parallel connection, as shown in Figure 1.They all be will input single linear frequency modulation on pulse signal be divided into the n road, in addition different to every road signal again time-delay and decay merge them the effect that has just played the analog sea reflection at last.1-1 is a directional coupler to 1-N-1 among Fig. 1 (a), and 2-1 is an adjustable attenuator to 2-N-1; (b) 1 to N is time-delay cable and the adjustable attenuator that increases gradually in.

This echo simulator has following deficiency: (1) size of whole simulator when n is big is too big, and is difficult to guarantee that the time delay between each discrete chirp pulse signal is equally spaced.Wherein in-line discrete echo simulator (Fig. 1, (a)) has many branch roads, is easy to produce self-excitation; (2) each bar branch road all needs an attenuator in these two kinds of schemes, and when n was very big, cost was too high.

Analogue echoes device-the single ring discrete echo analog device of radar altimeter that the purpose of this invention is to provide a kind of more accurate, reliable, easy analog sea reflecting effect.

The present invention is by directional coupler 1, directional coupler 2, variable gain amplifier 3, and limiter 4, bandpass filter 5, directional coupler 6, wave detector 7, loop gain control circuit 8, limiter slice level control circuit 9 are formed.Wherein directional coupler the 1, the 6th, and forward uses, and directional coupler 2 is reverse uses.

Describe each parts of the present invention and working condition in detail below in conjunction with Fig. 2.Add a chirp pulse signal from input end, signal is divided into two-way through behind the directional coupler 1, and main road leads to directional coupler 2 reverse coupled and enters the propagation of looped cycle ground, and the signal of branch road triggers loop gain control circuit 8 after wave detector 7 detections.Loop gain control circuit 8 sends control signal to variable gain amplifier 3, makes the gain of variable gain amplifier place top grade.At this moment, though there is natural attenuation in the loop, because the effect of variable gain amplifier 3, signal whenever turns around in loop and still can be exaggerated.Loop state at this moment is called the postiive gain state.The forward position of the chirp pulse signal that the forward position of the chirp pulse signal of circulating propagation just improves constantly in amplitude of output terminal generation through directional coupler 6 at every turn in loop, and be superimposed with the chirp pulse signal that before is coupled out that is not over yet, become the stack output of the discrete chirp pulse signal of the constant time lag of being separated by.Its constant time lag is propagated a circle by signal in loop time is determined.

When loop was in the postiive gain state, the amplitude of the chirp pulse signal of output increased gradually, thereby formed the rising edge of marine echo.When signal reaches the amplitude that needs, also be echo when reaching peak value, limiter 4 remains on signal on this amplitude it is no longer increased.When the chirp pulse signal of input finishes, wave detector 7 triggers loop gain control circuit 8 once more, and variable gain amplifier 3 is placed the low gain state by loop gain control circuit 8, make loop form negative gain, so the amplitude of signal reduces gradually in the loop, make echo occur negative edge again, finish process by discrete linear FM signal analog sea reflecting effect.In addition, because the present invention is a cyclic system, for avoiding being with outer self-excitation, the special bandpass filter 5 that in loop, is provided with.

By adjusting the amplification coefficient of variable gain amplifier 3, the amplification coefficient in the time of can changing loop postiive gain state is controlled the slope of echo rising edge with this; By regulating limiter slice level control circuit 9, can change the peak power of institute's analog echo signal.

Compared with former technology, this discrete echo simulator is simple in structure, size is little, easy realization, and can guarantee that the delay inequality between discrete chirp pulse signal equates.We know, the rising edge slope of true echo be by wave high determine that peak power is determined by backscattering coefficient.Owing to use this echo simulator can adjust these parameters easily, therefore can simulate the echo on various different seas easily.

Embodiment one (see figure 3):

Directional coupler 1, directional coupler 2 and directional coupler 6 adopt waveguide component; Variable gain amplifier 3 adopts the combination of the manual adjustable attenuator 3-1 of waveguides, the program control electrically controlled attenuator 3-2 in SAM joint two rank and microwave amplifier 3-3, and the damping capacity of adjustment adjustable attenuator can change the amplification coefficient after the combination; Limiter 4 adopts SAM joint variable resistor to regulate limiter and potentiometer with slice level control circuit 9; Wave detector 7 adopts the broadband scanning wave detector; Loop gain control circuit 8 is controlled the program control electrically controlled attenuator 3-2 in two rank for Pulse and Digital Circuits commonly used.Because used waveguide component in the loop, bandpass filter 5 can be omitted.But should increase coaxial waveguide conversion 10 in waveguide and SAM joint.

Embodiment two (see figure 4)s:

Directional coupler 1, directional coupler 2 and directional coupler 6 adopt waveguide component; Variable gain amplifier 3 adopts the combination of the manual adjustable attenuator 3-1 of waveguide and SAM joint pulse power power supply microwave amplifier 3-2, and the damping capacity of adjustment adjustable attenuator can change the amplification coefficient after the combination; Limiter 4 adopts SAM joint variable resistor to regulate limiter and potentiometer with slice level control circuit 9; Wave detector 7 adopts the broadband scanning wave detector; Loop gain control circuit 8 is the pulse power of microwave amplifier.Because used waveguide component in the loop, bandpass filter 5 can be omitted.But should increase coaxial waveguide conversion 10 in waveguide and SAM joint.

Claims

1. single ring discrete echo analog device of radar altimeter, it is characterized in that by directional coupler 1, directional coupler 2, variable gain amplifier 3 limiter 4, bandpass filter 5, directional coupler 6, wave detector 7, loop gain control circuit 8, limiter slice level control circuit 9 are formed.Wherein directional coupler the 1, the 6th, and forward uses, and directional coupler 2 is reverse uses.

Add a chirp pulse signal from input end, signal is divided into two-way through behind the directional coupler 1, and main road leads to directional coupler 2 reverse coupled and enters the propagation of looped cycle ground, and the signal of branch road triggers loop gain control circuit 8 after wave detector 7 detections.Loop gain control circuit 8 sends control signal to variable gain amplifier 3, makes the gain of variable gain amplifier place top grade.At this moment, though there is natural attenuation in the loop, because the effect of variable gain amplifier 3, signal whenever turns around in loop and still can be exaggerated.Loop state at this moment is called the postiive gain state.The forward position of the chirp pulse signal that the forward position of the chirp pulse signal of circulating propagation just improves constantly in amplitude of output terminal generation through directional coupler 6 at every turn in loop, and be superimposed with the chirp pulse signal that before is coupled out that is not over yet, become the stack output of the discrete chirp pulse signal of the constant time lag of being separated by.Its constant time lag is propagated a circle by signal in loop time is determined.

2. described by claim one, single ring discrete echo analog device of radar altimeter is characterised in that the amplification coefficient in the time of can changing loop postiive gain state is controlled the slope of echo rising edge with this by adjusting the amplification coefficient of variable gain amplifier 3; By regulating limiter slice level control circuit 9, can change the peak power of institute's analog echo signal.