Functional description
The transmit section of the NiM1B consists of a highly integrated sigma delta (fractional N) synthesizer
based single chip RF device, configured over an SPI serial bus by an on-board microcontroller. The primary
frequency reference for the transmitter is a 30MHz VC-TCXO. Modulation is applied directly to this reference
via an AF baseband filter (rather than using the chip's internal modulator) to permit a wider range of
baseband data rates and waveforms. Operation is controlled by the N_TXE line, the transmitter achieving full
RF output typically within 5ms of this line being pulled low. The RF output is filtered to ensure compliance
with the appropriate radio regulations and fed to the 50Ω antenna pin.
The receiver section of the NiM1B consists of a highly integrated sigma delta (fractional N) synthesizer
based Local Oscillator (LO), configured over an SPI serial bus by an on-board microcontroller. The primary
frequency reference for the LO is a 26MHz TCXO. The remainder of the receiver is a conventional dual
conversion super-heterodyne, using a wide dynamic range dual gate mosfet mixer and crystal / ceramic filter
elements for optimum performance. The RF input is filtered using a multi-stage LC filter in the front end to
provide image rejection and enhanced blocking performance. This reduces the user programmable
frequency range to the filter passband, but can easily be re-banded (in the factory) to other frequencies.
User interface
side view (through can)
side view (with can)
11 mm
top view (without can)
RF GND 1
18 0 Volt
Antenna
2
Vcc
17
16
RF OUT (TX)*
RF IN (RX)*
RF GND
3
4
5
6
7
8
9
N_TXE
15
23 mm
14 TXD
13 AF
12 RXD
11 RSSI
10 0 Volt
No pin
recommended PCB hole size: 1.2 mm
module footprint size: 25 x 32 mm
pin pitch: 2.54 mm
30.48 mm
33 mm
pins 4, 5, 6, 7, 8 & 9 are not fitted
Figure 3: NiM1B pin-out and dimension
NiM1B Pin Name
1, 3, 10, 18 0V
Function
Ground
3.3 – 15V DC power supply
17
16
15
14
13
12
VCC
N_RXE / RX PGM Pull low to enable Receiver / receive programming in put
N_TXE / TX PGM Pull low to enable Transmitter / transmit programming in put
TXD
AF
DC coupled input for 3V CMOS logic. Rin = 100k
500mV pk-pk audio. DC coupled, approx 1.5V bias
Open collector output, with a 10k pullup to Vcc. Suitable for Biphase
codes
RXD
11
RSSI
DC level between 0.5V and 2V. 50dB dynamic range
NOTES:
1. N_Rxe and N_Txe have (10K approx.) pullups to +Vin
2. Unit is programmable (in much the same way as an NTX2B or NRX2B) using the N_Rxe or N_Txe pins
Reprogramming requires a 0v to +Vin logic level non-inverted RS232 data-stream to pin 3 or 4
Alternatively. an RS232 port can be directly connected to the enable pin for programming, without risk
3. Avoid N_Rxe and N_Txe both low: undefined module operation may occur (but damage will not result)
4. Pinout is as BiM1. On RF connector end only pins 1,2,3 are present (*except for NiM1B with separate
RX and TX ports which has 4 pins. See ordering info ( p12) for further details on this special build).
5. Switching time as controlled by N_Txe or N_Rxe pins is <5mS, but when power is first applied to the
unit there is a 20mS long “calibration” period before the transmitter becomes active.
If the rail is switched (as opposed to the EN pins) then this should be considered as a 25mS device
Radiometrix Ltd.,
NiM1B transceiver data sheet
Page 3
RADIOMETRIX [ RADIOMETRIX LTD ]
