Chips for data transmission over a radio channel. Reference data

Encyclopedia of radio electronics and electrical engineering / Reference materials

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Let's start the review of Telecontrol microcircuits for transmitting / receiving data in the radio band with super-regenerative receivers of the RRx-XXX series (hereinafter, XXX is the operating frequency of the microcircuit, MHz). These are functionally complete devices made using hybrid thick-film technology. The receiver includes an RF pre-amplifier; radio frequency generator; blanking frequency generator; a low-pass filter that does not transmit vibrations from the radio frequency generator in the absence of reception; amplifier and comparator for generating an output signal with TTL levels. In fact, this is one of the options for a super-regenerative receiver without "strapping". A typical switching circuit is very simple (Fig. 1).

Let us note some features of the microcircuits of this series, the main technical parameters of which are given in Table. 1.

The use of laser contour tuning in the RR3, RR4, RR6, RR8, RR10 and RR11 products made it possible to improve the tuning accuracy up to ±200 kHz, which is 2,5 times better than in the RR1 chip. The RR4 device uses a cascade input amplifier, which made it possible to obtain the lowest level of the emission spectrum (-70 dBm). In cases where low power consumption is required, Telecontrolli recommends using RR6 or RR11 (current consumption 0,5 mA and 0,3 mA, respectively), but these microcircuits are somewhat inferior to the rest in sensitivity. And some deterioration in the parameters of the RR8 product compared to other devices in this series is a fee for a reduced (3 V) power supply.

The last chip in this series - RR15 - is placed in a shielded package. Its parameters are the most attractive: the tuning accuracy is ±75 kHz, the bandwidth at the level of -3 dB is ±250 kHz, the level of spurious emissions is 75 dBm. Only one "but" - the only operating frequency is 433,92 MHz. A significant drawback of super-regenerative receivers is their low selectivity. To obtain high-quality radio reception, superheterodyne receivers of the RRSx-XXX (amplitude modulation) and RRFx-XXX (frequency modulation) series are designed. Functional and typical wiring diagram for RRS1-XXXRRS3-XXX devices is shown in fig. 2.

Among them, the RRS2 chip, with good sensitivity (1,8 μVeff), has a high radiation level (an LC filter is installed instead of a SAW filter), but also a lower cost. The RRS3's preamplifier input filter achieves a narrow -3dB bandwidth and the lowest noise level. The main parameters of the microcircuits are given in Table. 2. The RRF1 FM receiver features an input filter with a preamplifier and a frequency detector instead of an amplitude one. Let's mention two more receivers: RRQ2-XXX and RRFQ1-XXX. Their main parameters are given in table. 2.

The functional diagram of these devices is almost the same as that of the RRSx series microcircuits. The differences are that in both receivers (with amplitude and frequency detectors, respectively), instead of a local oscillator, a crystal oscillator and a frequency synthesizer with phase synchronization are used, and instead of a SAW filter, an LC filter is used.

In addition to receivers, Telecontrolli produces transmitters with both amplitude modulation (RTx-XXX series) and frequency modulation (RTFx-XXX series). Their main parameters are given in table. 3.

Two microcircuits of this series (RT1 and RT2) are not considered here due to the lack of normalized parameters for noise, output power and input voltage level. On fig. 3 shows a typical wiring diagram for RTx series transmitters.

Transmitters RT4 - RT6, operating in the frequency band 303 ... 433 MHz, differ from each other in the level of spurious radio emissions, the output signal power, and RT6, in addition, still has an additional input. Otherwise, they are "twin brothers".

Functional and typical switching diagram of transmitters with built-in crystal oscillator RTQ1-XXX and RTFQ1-XXX is shown in fig. 4. To reduce power consumption in the "standby" mode, the EN input (pin 1) is provided to enable the operation of the generator and synthesizer (for the RTFQ1 device - the input to enable the operation of the synthesizer and amplifier).

The RTFQ1 chip is remarkable in that it has a frequency deviation of ± 30 kHz (total !!!), and a tuning accuracy of ± 25 kHz (typical value - 0).

Where and how can all these microcircuits be applied?

Enough has been said about traditional applications for security and safety systems, including automotive, and remote control. Obviously, such an inexpensive radio channel is of interest in climate monitoring systems as an element of information transmission from any number of geographically distributed sensors that can be located in greenhouses, greenhouses, incubators, and other objects of the agro-industrial complex. The main task of such systems is to measure climatic parameters, register their overshoot and control the corresponding equipment.

An example of the effective use of microcircuits for data transmission over a radio channel is a complex for measuring temperature in a greenhouse. The measuring complex inside each greenhouse consists of a recorder (a receiver with a range of up to 250 m) and the required number of autonomous sensors. Each sensor contains a temperature meter, controller, transmitter and power supply. As a temperature meter, it is best to use a DS1920 digital thermometer or a similar one manufactured by Dallas Semiconductor (see A. Sinyutkin's article "Overview of iButton family devices" in Radio No. 6, 2001).

Such a thermometer automatically captures temperature values ​​​​in non-volatile memory at specified time intervals, at this moment the sensor controller is in standby mode, consuming a minimum of energy. Periodically, it is activated, establishes a connection with the recorder and transmits over the radio channel all the temperature readings accumulated since the last communication session. Similarly, readings are taken from all sensors installed inside one greenhouse. The main advantages of this solution are ease of installation (the sensor can be placed anywhere) and configuration changes.

Of course, the entire measuring complex in the greenhouse can be built on a wired connection. However, there are situations when the wire cannot be stretched: registration of miners who are underground, registration of the movement of vehicles, etc.

The registration of miners is an important issue, since the registration of personnel located underground in emergency situations must be carried out instantly and reliably. In addition, due to the aggressive environment, the means of registration must be well protected, and the registration must be carried out passively, without the participation of people. Such conditions are feasible if radio identifiers are placed, for example, inside the battery of a miner's lamp.

Telecontrolli devices can be effectively used to keep track of scheduled passenger or freight transport schedules. Similar problems arise when taking into account the development and control of the working time of drivers. By equipping cars with electronic identifiers with a radio channel and placing recorders along traffic routes, you can confidently control the traffic schedule without imposing restrictions on the speed and order of routes.

The use of Telecontrolli chips for data transmission in the range of 300...900 MHz allows not only to reduce the total cost of the product, but also to create original systems with new consumer properties. More detailed information about the technical parameters of the Telecontrolli modules can be found on the Internet at

Author: N.Rakovich, Minsk

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