CN204131531U - A kind of attenuator for communication performance test - Google Patents

Abstract

For an attenuator for communication performance test, comprise resistance r ₀(1), resistance r ₁(2), resistance r ₂(3), host computer (4), 485 lines (5), single-chip microcomputer (6), relay (7), attenuator (8), signal generator (9), frequency spectrograph (10); Wherein resistance r ₀(1), resistance r ₁(2), resistance r ₂(3) attenuator (8) is formed with π type structure, one has 5 attenuators (8) is connected in series, each attenuator (8) is in parallel with a relay (7), relay (7) is controlled by single-chip microcomputer (6), reaches with this access and excision that control attenuator (8).The utility model provides the π type attenuator of one group of fixed value, and attenuator is free to combination, has good flexibility.The relay that attenuator is controlled by single-chip microcomputer accesses and excises, and single-chip microcomputer is communicated with host computer by 485 lines again, and system has good operability.

Description

A kind of attenuator for communication performance test

Technical field

The utility model relates to a kind of signal measurement and process measuring technique, belongs to electric power signal field of measuring technique.

Background technology

Along with the development of intelligent grid, Automatic meter reading system is more and more widely used in electric power system, and power line carrier communication and micro power radio communication are again one of Primary communication modes of Automatic meter reading system.And the producer of related communication module domestic is at present many, performance differs, and the performance of standard also ununified at present to communication module is tested.The test item of communication module performance generally include relaying performance, signal decay, antijamming capability, networking function and accept sensitivity etc., and all need to use attenuator about the measurement of these test items.The Main Function of attenuator has the size of signal in Circuit tuning; In comparative method for measuring circuit, can be used to the pad value of the tested network of direct-reading; Improve impedance matching, if when some circuit requirement has a more stable load impedance, then an attenuator can be inserted between this circuit and actual loading impedance, can cushion the change of impedance.Several structures such as conventional fixed attenuator has L-type, π type, T-shaped, X-type and bridge T-shaped.And the attenuator the being applied to communication module performance test at present shortcomings such as to there is attenuation range little, and regulable control is inconvenient.

In sum, a set of attenuator system by PC control is devised.Host computer by 485 line connection control Single Chip Microcomputer (SCM) system, by the relay of the delivery outlet control connection attenuator of single-chip microcomputer, thus is reached through the object that host computer picks out to the access controlling attenuator.Attenuator adopts the design of fixed attenuator, the pin network be made up of three resistance.Be connected in series by 5 attenuators altogether and form, signal attenuation weight range is 3dB ~ 71dB.System has good operation interface, and continuously adjustabe is good, can test in laboratory to the basic communication performance of carrier module.

Utility model content

The object of the utility model utility model, is that providing a kind of can be used in the lab to the Fader device of metering automation system communication module communication performance test.

The object of the utility model utility model is achieved in that

For an attenuator for communication performance test, the utility model feature is, comprises resistance r ₀, resistance r ₁, resistance r ₂, host computer, 485 lines, single-chip microcomputer, relay, attenuator, signal generator, frequency spectrograph; Wherein resistance r ₀, resistance r ₁, resistance r ₂form an attenuator with π type structure, one has 5 attenuators is connected in series, and each attenuator is in parallel with a relay, and relay, by Single-chip Controlling, reaches with this access and excision that control attenuator.

Single-chip microcomputer described in the utility model communicates with adopting 485 lines between host computer, and by host computer to the fill order of single-chip microcomputer sending filter.

5 attenuators series connection described in the utility model is formed, and attenuation is respectively 30dB, 20dB, 12dB, 6dB, 3dB; One end of attenuator group is accessed a signal generator and is used for sending test massage, and other end frequency spectrograph accepts the signal by attenuator group.

A kind of design principle of π type attenuator of the attenuator for communication performance test is as follows:

According to attenuation A _twith three resistance r of π type attenuator ₀(1), r ₁and r (2) ₂(3) relational expression: $\left\{\begin{array}{c}{r}_2=\frac{A_T+1}{A_T-1}{r}_0\\ r_1=\frac{{A_T}^2-1}{2A_T}{r}_0\end{array}\right.;$ First determine resistance r ₀(1) value, then calculate r according to above formula ₁and r (2) ₂(3) value, thus the attenuator (8) obtaining fixed attenuation value.

The utility model has the continuously adjustable characteristic of attenuation of attenuator, and can access the pad value of arbitrary size in theory, can regulate access attenuation flexibly in aspect.

π type resistor network as shown in figure (1), the input resistance of entering viewed from input equal r ₀, so can obtain:

(r ₀+r ₁)//r ₂+r ₁＝r ₀ (1)

Can obtain according to the relation of circuit input voltage and output voltage again:

$(\frac{(r_1+r_0)\frac{U_1}{r_0}}{r_2}+\frac{U_1}{r_0})r+\frac{U_1}{r_0}(r_1+r_0)=U_0$

Simultaneous formula (1) and formula (2), can obtain:

$r_1=r_0\frac{\frac{U_0}{U_1}-1}{\frac{U_0}{U_1}+1}$ With $r_2=r_0\frac{{\left(\frac{U_0}{U_1}\right)}^2-1}{2\frac{U_0}{U_1}}---\left(3\right)$ Voltage attenuation amount is:

$201g{A}_T=201g\left(\frac{V_{\mathrm{in}}}{V_{\mathrm{out}}}\right),$ Attenuation multiple A _t=V _in/ V _out

Because $V_{\mathrm{out}}=\frac{r_2//r_0}{r_1+r//r_0}{V}_{\mathrm{in}},$ Can obtain:

$\left\{\begin{array}{c}{r}_2=\frac{A_T+1}{A_T-1}{r}_0\\ r_1=\frac{{A_T}^2-1}{2A_T}{r}_0\end{array}\right.---\left(4\right)$

As can be seen from formula (4), by selecting different r ₀, r ₁and r ₂just can obtain different pad value A _t.

By different resistance values, form the attenuator that 5 attenuations are respectively 30dB, 20dB, 12dB, 6dB, 3dB.Control 5 relays respectively by 5 output ports of single-chip microcomputer, when relay is connected, corresponding attenuator, by short circuit, is equivalent to attenuator and excises from system.And single-chip microcomputer and host computer are connected with 485 lines, thus the switch of control relay can be carried out by host computer, thus reach the control access of attenuator and the effect of excision.

The beneficial effects of the utility model are:

1, provide the π type attenuator of one group of fixed value, attenuator is free to combination, has good flexibility.

2, the relay that attenuator is controlled by single-chip microcomputer accesses and excises, and single-chip microcomputer is communicated with host computer by 485 lines again, and system has good operability.

3, the attenuator of system is free to add and reduce, and decay can be made in theory to reach infinitely great, and attenuation continuously adjustabe.

Accompanying drawing explanation

Fig. 1 is the structural representation of the utility model π type attenuator;

Fig. 2 is system configuration schematic diagram of the present utility model.

In Fig. 1: 1, resistance r ₀; 2, resistance r ₁; 3, resistance r ₂.

In Fig. 2, left side is the host computer of system, and host computer and single-chip microcomputer directly adopt 485 interfaces to communicate, and 5 delivery outlets of single-chip microcomputer receive 5 relays respectively, and 5 relays are in parallel with 5 attenuators respectively.One section from attenuator connects a signal source, another termination frequency spectrograph, the signal source after can testing by attenuator by frequency spectrograph send signal.

Embodiment

As depicted in figs. 1 and 2, a kind of attenuator for communication performance test, the utility model feature is: comprise resistance r ₀1, resistance r ₁2, resistance r ₂3, host computer 4,485 line 5, single-chip microcomputer 6, relay 7, attenuator 8, signal generator 9, frequency spectrograph 10; Wherein resistance r ₀1, resistance r ₁2, resistance r ₂3 form an attenuator 8, with π type structure has 5 attenuators 8 and is connected in series, and each attenuator 8 is in parallel with a relay 7, and relay 7 is controlled by single-chip microcomputer 6, reaches with this access and excision that control attenuator 8; Adopt 485 lines 5 to communicate between single-chip microcomputer 6 with host computer 4, and give the fill order of single-chip microcomputer 6 sending filter 7 by host computer 4; 5 attenuators 8 are connected and are formed, and attenuation is respectively 30dB, 20dB, 12dB, 6dB, 3dB; One end of attenuator group is accessed a signal generator 9 and is used for sending test massage, and other end frequency spectrograph 10 accepts the signal by attenuator group.

A kind of design principle of π type attenuator of the attenuator for communication performance test is as follows:

According to attenuation A _twith three resistance r of π type attenuator ₀1, r ₁2 and r ₂the relational expression of 3: $\left\{\begin{array}{c}{r}_2=\frac{A_T+1}{A_T-1}{r}_0\\ r_1=\frac{{A_T}^2-1}{2A_T}{r}_0\end{array}\right.;$ First determine resistance r ₀the value of 1, then calculate r according to above formula ₁2 and r ₂the value of 3, thus to the attenuator 8 having fixed attenuation value.

Design parameter and experiment are:

1, as shown in Figure 1, resistance model used is VHA518-7, and maximum power is 1.75W, and 0 DEG C ~ 60 DEG C time, temperature coefficient is 0.05ppm/ DEG C, and noise is 0.01 μ V/V.

2, as shown in Figure 2, adopt a signal source to send the signal of a series of different voltage magnitude and frequency, access the attenuator of differential declines value respectively, output uses a frequency spectrograph to carry out test output signal.

3, the attenuator attenuates amount of 12dB is added, the signal of signal generator difference output frequency 100kHz, 120kHz, 145kHz, 180kHz, 270kHz, 305kHz, 390kHz, 421kHz, the signal after decay is read with frequency spectrograph, every frequency reading 3 number, using mean value as experimental result, experimental data is as follows.Experimental result shows, when attenuation one timing of setting, along with the increase of signal frequency, the gap of attenuation and design load is little, and system has good fade performance.

Input (dB)	-10.67	-10.86	-10.42	-10.35	-10.47	-10.92	-10.62	-11.3
									Export (dB)	-22.69	-22.83	-22.37	-22.27	-22.41	-22.9	-22.6	-23.27
Table end (dB)	-25.99	-26.1	-25.58	-25.4	-25.23	-25.51	-24.74	-25.18
									Attenuator attenuates amount (dB)	12.02	11.97	11.95	11.92	11.94	11.98	11.98	11.97

Claims (3)

1., for an attenuator for communication performance test, it is characterized in that: comprise resistance r ₀(1), resistance r ₁(2), resistance r ₂(3), host computer (4), 485 lines (5), single-chip microcomputer (6), relay (7), attenuator (8), signal generator (9), frequency spectrograph (10); Wherein resistance r ₀(1), resistance r ₁(2), resistance r ₂(3) attenuator (8) is formed with π type structure, one has 5 attenuators (8) is connected in series, each attenuator (8) is in parallel with a relay (7), relay (7) is controlled by single-chip microcomputer (6), reaches with this access and excision that control attenuator (8).

2. a kind of attenuator for communication performance test according to claim 1, it is characterized in that: between single-chip microcomputer (6) with host computer (4), adopt 485 lines (5) to communicate, and by host computer (4) to the fill order of single-chip microcomputer (6) sending filter (7).

3. a kind of attenuator for communication performance test according to claim 1, is characterized in that: 5 attenuator (8) series connection are formed, and attenuation is respectively 30dB, 20dB, 12dB, 6dB, 3dB; One end of attenuator group is accessed a signal generator (9) and is used for sending test massage, and other end frequency spectrograph (10) accepts the signal by attenuator group.