Methods and systems relating to ultra wideband transmitters
Within many applications impulse radio based ultra-wideband (IR-UWB) transmission offers significant benefits for very short range high data rate communications when compared with existing standards and protocols. In many of these applications the main design goals are very low power consumption and very low complexity design for easy integration and cost reduction. Digitally programmable IR-UWB transmitters using an on-off keying modulation scheme on a 0.13 microns CMOS process operating on 1.2 V supply and yielding power consumption as low as 0.9 mW at a 10 Mbps data rate with dynamic power control are enabled. The IR-UWB transmitters support new frequency hopping techniques providing more efficient spectrum usage and dynamic allocation of the spectrum when transmitting in highly congested frequency bands. Biphasic scrambling is also introduced for spectral line reduction. Additionally, an energy detection receiver for IR-UWB is presented to similarly meet these design goals while being adaptable to address IR-UWB transmitter specificity.
1. A transmitter for an impulse radio comprising:
a radio frequency (RF) signal generator for transmitting data, the RF signal generator receiving a data signal to be transmitted and a clock signal characterized by a clock frequency and coupled to an RF antenna and a control circuit;
the control circuit for controlling the generation of the transmitted data such that each bit being transmitted is comprised of a plurality N pulses generated by the RF signal generator wherein each pulse of the N pulses is at a predetermined frequency of a plurality M frequencies, has a predetermined amplitude, and has a predetermined pulse length;
wherein N≥2 and M≥2;
M and N are integers;
wherein the RF signal generator comprises
an AND gate receiving a pulse clock signal and the data signal thereby generating a series of pulses having a pulse repetition rate set by the pulse clock signal and the number of pulses within the series of pulses set by a length of a data signal high; and
a pulse generator generating pulses having Gaussian shaped pulse when triggered by a rising edge of each pulse generated by the AND gate;
wherein the pulse generator comprises:
a first transistor coupled to an input port of the pulse generator receiving the series of pulses output by the AND gate;
an output port providing an output pulse to subsequent stages of the RF signal generator;
a second transistor coupled to the output port;
a third transistor disposed between the first transistor and second transistor and R serially connected inverter stages; and
the R inverter stages;
wherein R is a positive integer;
upon the data signal at the input port of the pulse generator going high with the output of the pulse generator low a node at which the first transistor, second transistor, and third transistor are coupled goes high and this voltage propagates through the R inverter stages to generate the rising edge of the pulse being generated by the pulse generator;
upon the output of the pulse generator going high the second transistor is activated and the voltage at the node discharges which again propagates through the R inverter stages to generate a falling edge of the pulse being generated by the pulse generator.
2. The transmitter according to claim 1 , wherein
the frequencies of the N pulses comprising each bit of the data signal being transmitted are scrambled by randomizing their selection from within the plurality M frequencies;
each transmitted pulse transmitted has either a first phase or a second phase where the sequence of phases of the transmitted pulses is pseudo-randomly established.
3. The transmitter according to claim 1 , wherein
the frequencies of the N pulses for each bit transmitted over multiple bits of the data signal are scrambled;
a phase of each pulse of the N pulses for each bit transmitted over multiple bits of the data signal are pseudo-randomly set to either a first phase or a second phase; and each bit transmitted complies with at least one of a mask and a sub-mask.
4. The transmitter according to claim 3 , wherein at least one of:
the at least one of the mask and the sub-mask to which each bit complies changes between one bit transmitted and a next bit transmitted; and
the transmitter supports dynamic mask adaptation at a per bit level.
5. The transmitter according to claim 1 , wherein
a pulse repetition rate of the RF signal generator is determined in dependence of the clock frequency;
the integer N depends upon a duration of a bit of the data signal and the pulse repetition rate of the RF signal generator; and
the plurality N pulses are transmitted within the duration of the bit of the data signal and comprise pulses at the plurality M frequencies.
6. The transmitter according to claim 1 , wherein
the plurality N pulses each at a predetermined frequency of the plurality M frequencies having predetermined amplitude and predetermined pulse length provide a predetermined accumulated power density spectrum that has one or more notches, each notch of the one or more notches centered at a predetermined frequency defined by a wireless transmission standard; and
the wireless transmission standard is at least one of an international wireless standard and a national wireless standard.
7. The transmitter according to claim 1 , wherein
the RF signal generator comprises at least a pulse generator generating pulses at a pulse repetition rate determined by the clock signal coupled to the pulse generator and a programmable digitally controlled ring oscillator (DCRO) operating over a frequency range covering the plurality M frequencies coupled to an output of the pulse generator; and
the RF signal generator operates independent of any mixer and phase locked loop.
8. The transmitter according to claim 7 , wherein
the transmitter operates directly independent of any up-conversion of data being transmitted.
9. The transmitter according to claim 7 , wherein
the programmable digitally controlled ring oscillator (DCRO) comprises a plurality of digitally programmable delay cells (DPDCs) which are serially connected;
a predetermined subset of the plurality of DPDCs each have a pair of transistors disposed in parallel to the respective DPDC;
the pairs of transistors associated with each DPDC are on when no input pulse from the pulse generator is present thereby reducing a gain of each DPDC such that the programmable DCRO is off; and
the pairs of transistors associated with each DPDC are off when an input pulse from the pulse generator is present thereby restoring a gain of each DPDC such that the programmable DCRO is on.
10. The transmitter according to claim 1 , wherein
a predetermined S inverter stages of the plurality of R inverter stages further comprise a first transistor pair coupled to a lower power rail and a second transistor pair coupled to an upper power rail;
an S bit word controls starving of the S inverter stages with a T th bit of the S bit word coupled to the first transistor pair in a T th inverter stage and an inverse of the T th bit of the S bit word coupled to the first transistor pair in the T th inverter stage;
the S bit word establishes a delay within the S inverter stages; and
a pulse width of the pulse generator is established in dependence upon a total delay within the S inverter stages.
11. The transmitter according to claim 1 , wherein
the control circuit includes a power cycling controller comprising a plurality of non-overlapping signal generation circuits;
each non-overlapping signal generation circuit of the plurality of non-overlapping signal generation circuits coupled to a predetermined portion of the RF signal generator and generating appropriate control signals to power up or power down that predetermined portion of the RF signal generator; and
the plurality of non-overlapping signal generation circuits are timed to reduce impact on an output signal whilst reducing power consumption of the RF signal generator.
12. The transmitter according to claim 11 , wherein
the power cycling controller employs the data signal and a transmit clock to determine when to power up or power down the different predetermined portions of the RF signal generator.
13. The transmitter according to claim 1 , wherein
the RF signal generator employs biphasic phase scrambling of sequential pulses such that each pulse has either a first phase or a second phase;
the biphasic phase scrambling is pseudo-random.
14. The transmitter according to claim 13 , wherein
the RF signal generator incorporates a dual output amplifier wherein a first output of the dual output amplifier has the first phase and a second output of the dual output amplifier has the second phase;
the dual outputs of the dual output amplifier are coupled to a switch; and
the switch selectively selects either the first output of the dual output amplifier with the first phase or the second output of the dual output amplifier with the second phase in dependence upon a pseudo-random control signal coupled to the switch.
15. The transmitter according to claim 13 , wherein
the biphasic phase scrambling is implemented by affecting a startup condition of a digitally controlled ring oscillator within the RF signal generator such that it starts up with either an output having the first phase or an output with the second phase; and
the digitally controlled ring oscillator is affected by a pseudo-random control signal.
16. The transmitter according to claim 1 , wherein
the RF signal generator comprises:
a pulse generator generating pulses at a pulse repetition rate determined by the clock signal coupled to the pulse generator;
a programmable digitally controlled ring oscillator operating over a frequency range covering the plurality AI frequencies coupled to an output of the pulse generator; and a variable gain amplifier electrically coupled to the output of the pulse generator; wherein the variable gain amplifier counteracts frequency dependent output amplitude variations of the programmable digitally controlled ring oscillator.
17. The transmitter according to claim 16 , wherein
the variable gain amplifier consists of a common source amplifier with an active load;
a transistor coupled to the variable gain amplifier when disabled by a control signal cuts off a bias current for the variable gain amplifier and when enabled by the control signal acts as an active load.
18. The transmitter according to claim 16 , wherein
a gain of the variable gain amplifier is controlled by a digitally programmable transistor array acting as a tunable degeneration resistance for the variable gain amplifier;
the digitally programmable transistor array comprising an array of X transistors and a Y:X bit decoder;
the Y:X bit decoder receives a Y bit input control code and selectively activates only transistor with the array of X transistors;
each transistor within the array of X transistors is a different size transistor.
19. The transmitter according to claim 16 , further comprising
a driver coupled to an output of the variable gain amplifier;
wherein a series inductor is provided between the variable gain amplifier and the driver to resonate with a decoupling capacitor of the driver to improve gain uniformity at higher frequencies.