1.
Can I increase the bit rate to higher limit than the 64 kbps?
- Yes, by deactivating the bit synchronizer function of the XE1201. You can then reach up to 150 kbps.
- Of course, one has to perform the data stream filtering and synchronization with the microcontroller (digital signal processing).
2.
Can I use the XE1201 for communication audio(voice)?
- YES, after digital conversion of the voice and with few KHz band.
- The audio signal is first converted via an ADC (8 bits sampling rate of 8 to 10 KHz) into a digital bits stream.
- Thanks to the high bit rate up to 64 kbps offered by the XE1201, the data is easily transmitted and/or received.
3.
Can I use the XE1201 in WLAN (wireless LAN system)?
- No, the XE1201 bit rate (even at 150 kbps with the bit synchronizer block deactivated) is not large enough to transmit and decode the data traffic involved in WLAN (i.e. files, transfers handled by Ethernet that are close to 10 Mbps).
- However, the XE1201 becomes interesting for multimedia equipment interfaces: wireless mouse, headset, keyboard, printers, etc..
4.
What is the meaning of "Half-Duplex" mode on the XE1201?
- By essence, the XE1201 communicates in half-duplex (like a standard talky-walky system, although transmit and receive are not simultaneous, when transmitting, the receive chain is off and vice-versa.
- An external input pin "RXTX" allows the user to set the XE1201 as a transmitter or as a receiver.
- Since the switching times from TX to RX are very fast(typically 75 us!), apparent full-duplex operation can be seen with an appropriate communication protocol.
5.
Can I use one unique antenna for both transmitting and receiving?
- YES, with a matching network between the physical antenna and the XE1201, one unique antenna acts alternatively as a receiver and as a transmitter element. The structures and the values of the
matching network components depend on the antenna types and the carrier frequency.
Typical schematics and values can be found in the XEMICS "XE1201 Application information notes" downloadable from the web site www.xemics.ch
6.
Can I derive from the XE1201 a specific version for my application?
- Yes, since the XE1201 is a 100% proprietary design from XEMICS, any cell, block or complete chip can be modified or tuned to specific characteristics.
Examples can be separate transmitter, receiver, fixed PLL or synthesizer based LO, etc....
Obvious advantages are the better matching of chip behaviours and application demands, lower prices, proprietary design (ASIC).
In addition to that, such ASICs are very easy and are low risk to make (starting from existing and well proven designs). The "price" to pay is that one needs to generate a new layout, new mask set and new samples with a small industrialization phase (test program adaptation).
The criteria to consider for making the decision of going to ASIC are the amount of changes to be performed, the yearly volume, allowed timing etc...
7.
What kind of levels are used by the digital pins?
- All digital pins to/from the XE1201 (RXD, CLKD, SD, SC, CE, EN, RXTX, TXD) are CMOS types. For input levels, VIH min= 80% *VCC and VL max = 20%*VCC. For output levels, VOHmin = VCC - 0.4 volt and VOLmax = 0.4 volt.
8.
What are the delivery times for the XE1201 products?
- The XE1201 has been in production since the end of 1998; XEMICS can handle any production order quantities. The delivery times are influenced by the logistics and thus by the shipment quantities. For quantities of a few Kunits, delivery can be better performed within 1 week.
- For quantities up to 20K units, delays are 3 weeks.
9.
Which kind of SAQ should I use for the LO resonator element?
- XEMICS has tested the several SAWs from different sources: Siemens, RFM, u-rata are typical examples. As practical examples at 433.92 MHz, you can use the R707 from Siemens or the RO-2101A from RFM.
10.
What are the typical ranges I can get when using the XEMICS XE1201?
- This depends on several factors (where some are under the customer's control):
- In free space or in building or a mixture of both
- Type and quality of the antenna (wire, loop,...)
- Transmit power chosen inside the XE1201 chip (up to -5 dBm).
- Eventual additional power amplifier
- As indications, with a "quarter" length antenna (piece of wire / -10 dBi gain) and with an external PA giving +10 dBm transmit power, ranges can reach several km in free space and 100 meters in building.
11.
What types of antenna can I use with the XE1201?
- They come in many types and can have differerent forms; whip, piece of wire, loop of wire, printed wire or... nothing: all depend on the available physical place you allow the range to be covered and the transmit power (global current consumption) you have chosen.
- Additional discussions on the antenna calculations and performances can be found in the XEMICS XE1201 Application information notes(downloadable from www.xemics.ch).
12.
What is the appropriate number of preamble bits to use in data stream at the beginning?
- The preamble requires the correct working of the integrated bit synchronizer block.
- XEMICS recommends a number between 8 to 20. It is a trade-off between receiver error rate and total message length. In fact there is no maximum (you can insert as many preamble bits as you want).
If the total message length is critical in your application, you can eventually send the preamble bits. In this latter case,
each data bit will be of course "seen" twice by the controller (which is not a problem if you divide the data sampling clock frequency accordingly).
13.
I like the XE1201 features (data range, integrated bit synchronizer), but I need to work at 900 MHz or at 2.4 GHz. Is there any solution ?
- Yes, by inserting an "up/down" conversion stage at the RF front-end.
The carrier frequency is translated from 900 MHz or 2.4 GHz into 400 Mhz in the receiver pat and from 400 MHz to 900 MHz or 2.4 GHz into 400 MHz.
- The XE1201 acts simply as an IF and base band processing unit.
- XEMICS has issued an application note (ANO1) illustrating the approach.
14.
Why should you use an Antenna Impedance Matching Network to the RFIN an RFOUT Pins of the XE1201?
- The main purpose is to match the input/output RF amplifier impedances with the antenna impedance at the operating carrier frequency. A good "matching" insures the greatest transfer of power between the circuit and the air.
- In addition, the matching operation (tuning effect) will reduce interference, spurious and harmonics when transmitting (increase of power efficiency) or receiving (increase of receiver sensitivity).
15.
What is the global noise factor performed by the XE1201 receive chain?
16.
The Bit Synchronizer is a powerful function. Its correct working and maximum performance need some practical rules observation. Can XEMICS highlight them?
- The bit synchronizer block is integrated in the XE1201 in hardware and is directly attached to the FSK demodulator. In order to obtain a valid synchronization between received data and synchronize clock, one needs to have the valid RF input already present at the antenna before the XE1201 is switched on its receive mode.
- If you don't know exactly when data is present on the RF input pin, you can use a timer (provided by the timer function of the microcontroller).
- The following example is a typical illustration of the working sequence (which is part of the communication protocol):
-
- 1- You switch the XE1201 in receiver mode
- 2- Start word identification task by the microcontroller. Word identified?
- 21- If no, then switch the XE1201 onto stand-by mode and start timer (wait one second)
- Return to step 1
- 22- If yes, read the data with the synchronized clock
- 221- When the Stop word is identified
- switch the XE1201 in stand-by mode and start timer (wait one second)
Return to step 1
- Additional details are described in the XEMICS XE1201 Application Information brochure(web site).
17.
Is there a set of operating conditions that maximize the XE1201 performances and if yes, what are they?
- Yes, the design of the XE1201 has been optimized for VCC = 3.0 volt, temp = 25癈, carrier frequency of 433.92 MHz, frequency deviation of 125 kHz, data rate of 16 kbps.
- These values give the specification values indicated in the XE1201 data sheet.
18.
Can I let the XE1201 work at 12 volt?
- No, it is not recommended to have power supply higher than 6 volt (even for a shorter period of time) applied to the XE1201. Th limit is imposed by the silicon process where the functions will enter in breakdown.
- This can destroy the chip if not current limitation is active. In addition, the too high power supply will induce "hot electrons" in the MOS silicon oxide gate causing definitive degradation of the transistors (increase of static current consumption)
19.
Is it required that the data stream must be pre-coded in Manchester format before it is applied to the XE1201 modulator?
- No, and that is one of the positive aspects of the XE1201, the data stream accepted by the XE1201 can be the simple NRZ format (data is just the 0 and 1 levels). This is thanks to the DDS (direct digital synthesizer), the levels (1 & 0 are directly converted into digital-synthesized frequency deviation: FDEV for 1 & FDEV for 0).
- This can destroy the chip if not current limitation is active. In addition, the too high power supply will induce "hot electrons" in the MOS silicon oxyde gate causing definitive degradation of the transistors (increase of static current consumption)
20.
My application needs to work on 315 MHz. Is it compatible with the XE1201 operations?
- Yes, the XE1201 is able to work down to 300 MHz. There are several customers that are building 315 MHz applications, mostly in North America.
- XEMICS can provide detailed schematics and BOM for typical 315 MHz environment (matching network, tank, SAW) and evaluation board.
21.
The XE1201 is in a 32-TFQP. Can I purchase the XE1201 in another package or in a die form?
- YES, the XE1201 can be made available as die forms or in another package. the 2 points to keep in mind are:
The new package is compatible with RF. A small industrialisation phase must be planned (test program adaptation).
22.
Do I need to ask for frequency licensing, homologation or certification?
- When used in the ISM band, there is no liscense to be asked (free for everybody). It remains that the FINAL application needs to be submitted to the national homologation or
or certification. Thus components, (XE1201 is a component), and partial blocks (like the ARF2104 module are not concerned.
23.
What is "antenna trimming" and should I consider this in my application?
- The antenna trimming is often an adjustable passive component (variable inductor or capacitator placed in series with the physical antenna).
The purpose is to maximize the antenna efficiency. The type and value of the trimming element depends also on the kind of antenna used; loop, quarter-length, helicoidal, etc....
Normally, if the matching network is correctly designed, the trimming element can be replaced by a fixed value after the development phase.
24.
I would like to monitor and receive signal strength (RSSI system). Can I consider this with the XE1201?
- The XE1201 ( and the ARF2104 board) has no fully integrated RSSI. The main reason being that in a non-channelized band, which is the case for the European 433 MHz ISM band), an evenutal RSSI-AGC will not be very useful.
Pertubators and interferances are so that the signal strength indication will not reflect correctly the situation.
- If your system is based on a net structure with a master and several slaves, one good approach is to do "time slot sharing" where the master
interrogates every slave in sequence. However, if really desired, a RSSI can be built with the IO and QO signals provided by the XE1201;
they exhibit signals where amplitudes levels reflecting the received RF power. The signal levels at IO and QO can go up to 500mV peak.
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