Broadband, low power FM/FSK transceiver for wireless communications systems

A method for receiving and transmitting FSK modulated carrier signals in a low power transceiver for a wireless communications interface having an antenna for receiving and radiating said FSK modulated carrier signals, a microcontroller with a parallel port for electrical communication with a host system, and a switch system responsive to said microcontroller for switching said antenna into a receive mode or a transmit mode, which comprises the steps of:

• filtering a third harmonic from a cyrstal controlled oscillator and tripling said third harmonic in a tripler in electrical communication with said crystal controlled oscillator to provide a stable reference signal having a frequency equal to a sum of a frequency of said FSK modulated carrier signals and an offset frequency;
• filtering and amplifying said FSK modulated carrier signals in a preamp/filter system in electrical communication with said switch system;
• mixing said FSK modulated carrier signals received from said preamp/filter system and said stable reference signal in a mixer in electrical communication with said preamp/filter system and said tripler to provide a first FSK modulated offset signal having said offset frequency;
• generating a second FSK modulated offset signal having said offset frequency by applying a transmission data signal received from said microcontroller to a first VCO;
• detecting a phase difference between said first FSK modulated offset signal and said second FSK modulated offset signal in a phase detector in electrical communication with said first VCO and said mixer to provide a phase error signal;
• generating a first of said FSK modulated carrier signals by applying said phase error signal to a second VCO in electrical communication with said phase detector;
• applying a sweep signal from said microcontroller to said phase detector to increase speed of locking said first FSK modulated offset signal to said second FSK modulated offset signal, and said first of said FSK modulated carrier signals to said second FSK modulated offset signal;
• applying said transmission data signal from said microcontroller to said second VCO to feed forward compensate said phase error signal and thereby extend transceiver bandwidth above DC;
• amplifying and filtering said first of said FSK modulated carrier signals in a series circuit comprised of a power amplifier in electrical communication with said second VCO and a filter in electrical communication with said switch system;
• entering said transmit mode in response to a first control signal issued by said microcontroller to said switch system to allow said antenna to radiate said first of said FSK modulated carrier signals;
• electrically isolating said first VCO, said phase detector, said second VCO, and said series circuit from said preamp/filter system and said antenna in response to a second control signal issued by said microcontroller to said switch system to enter said receive mode;
• demodulating said first FSK modulated offset signal and detecting transmission data through adaptive thresholding in a receiver system in electrical communication with said microcontroller;
• and
• issuing transmission data detected in said receiver system to said microcontroller for transfer to said host system by way of said parallel port.

A low power transceiver system for receiving and transmitting FSK modulated carrier signals in a wireless communications interface of a Desktop Area Network, which comprises:

• a crystal oscillator for generating a third harmonic of a stable fundamental frequency;
• a tripler in electrical communication with said crystal oscillator for generating a stable reference signal having a frequency three times that of said third harmonic;
• an antenna which is tuned to resonate at said FSK modulated carrier signals nominal frequency, and which receives said FSK modulated carrier signals when in a receive mode and radiates said FSK modulated carrier signals when in a transmit mode;
• a PIN switch in electrical communication with said antenna for placing said antenna in said receive mode in response to a first control signal and in said transmit mode in response to a second control signal, and routing said FSK modulated carrier signals from and to said antenna;
• a preamp/filter circuit in electrical communication with said PIN switch for removing harmonics and spurious signals from said FSK modulated carrier signals received from said PIN switch;
• a mixer in electrical communication with said preamp/filter circuit and said tripler for mixing said stable reference signal and said FSK modulated carrier signals to generate a first FSK modulated offset signal having an offset frequency;
• a microcontroller having a parallel port for communicating with a host system in said Desktop Area Network;
• a first VCO in electrical communication with said microcontroller and responsive to a transmission data signal issued by said microcontroller to generate a second FSK modulated offset signal having said offset frequency;
• a phase detector in electrical communication with said mixer and said first VCO, and receiving said first FSK modulated offset signal and said second FSK modulated offset signal to detect phase differences and create therefrom a phase error signal, and in electrical communication with said microcontroller and receiving a sweep signal issued by said microcontroller;
• a second VCO in electrical communication with said phase detector and said microcontroller, and receiving said phase error signal and said transmission data signal to generate a feedforward compensated phase error signal as a drive signal in generating said FSK modulated carrier signals;
• a power amplifier in electrical communication with said second VCO and receiving said FSK modulated carrier signals to boost power levels in said FSK modulated carrier signals for wireless transmission;
• a transmit bandpass filter in electrical communication with said power amplifier and said PIN switch, and receiving said FSK modulated carrier signals from said power amplifier to remove harmonics and other spurious signals before said FSK modulated carrier signals are routed by said PIN switch both to said preamp/filter circuit to complete an offset phase lock loop and to said antenna for transmission when said antenna is in said transmit mode;
• and
• a receiver system in electrical communication with said mixer and said microcontroller for detecting an occurrence of said FSK modulated carrier signals through adaptive thresholding and upon detecting said occurrence demodulating said first FSK modulated offset signal to send transmission data to said microcontroller.