Biasing scheme for constant regulated local oscillator in mm-wave tripler
A biasing scheme for a frequency multiplication circuit, and transceiver using LO signals provided by the frequency multiplication circuit are described. A frequency doubler is cascaded with a mixer to provide a mm-wave oscillator signal. The combination provides a frequency triple that of the LO frequency supplied to the frequency doubler from a PLL. A small-sized replica of the frequency doubler is used to determine biasing of transconductance devices of the frequency doubler. A voltage output of the replica is amplified and the difference between the output and a reference voltage is supplied as feedback to the control terminal of the transconductance devices to bias the transconductance devices to near threshold. The biasing is replicated at the frequency doubler to compensate for PVT variations. A PTAT current source tied to the output of the replica regulates an average output current of the frequency multiplication circuit.
1. A frequency multiplication circuit comprising:
a frequency multiplier circuit containing first matched transistors, the frequency multiplier circuit configured to receive differential local oscillator (LO) signals of a first frequency and produce a harmonic signal having a second frequency, the second frequency being a first multiple of the first frequency;
a mixer circuit cascaded with the frequency multiplier circuit, the mixer circuit having mixer matched transistors configured to receive other differential LO signals of the first frequency and the harmonic signal and produce another harmonic signal having a third frequency, the third frequency being a mm-wave frequency that is a second multiple of the first frequency; and
a frequency multiplier biasing circuit that is a reduced-sized replica of the frequency multiplier circuit, the frequency multiplier biasing circuit having second matched transistors, the frequency multiplier biasing circuit configured to control biasing of the first matched transistors via a difference between an output voltage of the frequency multiplier biasing circuit and a reference voltage and application of an output of the difference to the first and second matched transistors.
2. The frequency multiplication circuit of claim 1 , wherein the differential LO signals are in-phase signals (I+, I−), the other differential LO signals are quadrature-phase signals (Q+, Q−), and the frequency multiplier biasing circuit is supplied with the in-phase signals.
3. The frequency multiplication circuit of claim 1 , wherein the first and second matched transistors and the mixer matched transistors are N-type metal-oxide-semiconductor (NMOS) transistors.
4. The frequency multiplication circuit of claim 3 , wherein the biasing of the first matched transistors is Class C region biasing supplied to a gate of each NMOS transistor of the frequency multiplier circuit from an amplifier through a matched resistor, the Class C region biasing supplied to a gate of each NMOS transistor of the frequency multiplier biasing circuit.
5. The frequency multiplication circuit of claim 4 , wherein the amplifier has an inverting input coupled to a drain of each NMOS transistor and a non-inverting input coupled to the reference voltage.
6. The frequency multiplication circuit of claim 4 , wherein mixer biasing is supplied to a gate of each NMOS transistor of the mixer circuit, the mixer biasing being independent of the Class C region biasing.
7. The frequency multiplication circuit of claim 3 , wherein the frequency multiplier biasing circuit comprises a proportional-to-absolute temperature (PTAT) current source coupled to a drain of each NMOS transistor, the PTAT current source configured to provide regulation of an average output current of the frequency multiplier circuit.
8. The frequency multiplication circuit of claim 1 , wherein the frequency multiplier biasing circuit is scaled down version of the frequency multiplier circuit having has a size about ten times less than the frequency multiplier circuit.
9. A frequency multiplication circuit comprising:
means for supplying local oscillator (LO) signals; and
means for supplying mm-wave oscillator signals based on the LO signals, the means for supplying mm-wave oscillator signals comprising:
means for generating the oscillator signals using higher-order harmonics of the LO signals; and
means for biasing the means for generating the oscillator signals when the means for generating the oscillator signals is near threshold,
the means for biasing:
replicating, in reduced size, the means for generating the oscillator signals, and
configured to track large signal performance of devices of the means for generating the oscillator signals across process, voltage and temperature (PVT) variation to determine biasing of the means for generating the oscillator signals based on biasing of the means for biasing.
10. The frequency multiplication circuit of claim 9 , wherein the means for supplying mm-wave oscillator signals is further configured to triple a LO frequency of the LO signal by:
generating second harmonics of the LO frequency, and
subsequently generating third harmonics of the LO frequency based on the second harmonics of the LO frequency.
11. The frequency multiplication circuit of claim 9 , wherein the means for biasing further comprises means for regulating an average output current of the frequency multiplication circuit using a proportional-to-absolute temperature (PTAT) current of an output of the means for biasing.