Product Info

VTech proprietary and confidential
VTech Communications LTD.
R&D Department
The document is VTech’s proprietary information, Please do not disclose to third party without VTech’s consent
Ref. No.: 20191009 Version: 01 Date: 09 Oct, 2019 Page 6 of 33
excellent performance in the presence of noise enables VTBM-A01 BT Module to exceed the Bluetooth requirements for co-
channel and adjacent channel rejection.
2.3 RF transmitter
2.3.1 IQ modulator
The transmitter features a direct IQ modulator to minimize frequency drift during a transmit timeslot, which
results in a controlled modulation index. Digital baseband transmit circuitry provides the required spectral
shaping.
2.3.2 Power amplifier
The internal PA output power is software controlled and configured through a PS Key. The internal PA on the
VTBM-A01 BT Module has a maximum output power that enables it to operate as an up to Class 1 Bluetooth
radio without requiring an external RF PA.
2.3 Bluetooth radio synthesizer
The Bluetooth radio synthesizer is fully integrated onto the die with no requirement for an external VCO
screening can, varactor tuning diodes, LC resonators, or loop filter. The synthesizer is guaranteed to lock in
sufficient time across the guaranteed temperature range to meet the Bluetooth v5.0 specification.
2.4 Baseband
The baseband handles the digital functions of the Bluetooth modem, for example the Burst Mode Controller
and Physical Layer Hardware Engine.
3.0 Clock generation
3.1 Crystal calibration
Crystal calibration uses a single measurement of RF output frequency and can be performed quickly as part of
the product final test. Typically, a TXSTART radio command is sent and then a measurement of the output
RF frequency is read. From this process, the calibration factor to correct actual offset from the intended
frequency can be calculated. This offset value is stored in PSKEY_ANA_FTRIM_OFFSET. VTBM-A01 BT
Module then compensates for the initial frequency offset of the crystal.
The value in PSKEY_ANA_FTRIM_OFFSET is a 16-bit two's complement signed integer that specifies the fractional part
of the ratio between the true crystal frequency, factual, and the value set in PSKEY_ANA_FREQ, fnominal.
PSKEY_ANA_FTRIM_OFFSET = (factual / fnominal – 1) ×2^20
For more information on TXSTART radio test, see the Blue Test User Guide.